JP2005099421A - Low transmittance transparent conductive substrate and its manufacturing method, coating liquid for forming low transmittance transparent conductive layer used for manufacturing the substrate, and display device applied with the substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low transmittance transparent conductive substrate which has an excellent body color (a film color, a transmission spectrum) and high film strength, to which a low reflectance property, a static dissipation property, an electric field shielding function and contrast improving effect are optionally added and its manufacturing cost is reduced, and to provide its manufacturing method and the like. <P>SOLUTION: The low transmittance transparent conductive substrate is provided with a low transmittance double layer film comprising a low transmittance transparent conductive layer containing carbon black fine particles and a transparent coating layer sequentially formed on a transparent substrate, and is characterized by having the low transmittance transparent conductive layer composed of low specific surface area carbon black fine particles with 50-200 m<SP>2</SP>/g specific surface area, high specific surface area carbon black fine particles with 500-2,000 m<SP>2</SP>/g specific surface area and a binder matrix as main components and having the transparent coating layer constructed with a colored transparent coating layer with blue type pigment fine particles and/or red type pigment fine particles and a binder matrix as main components. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has a transparent substrate, a low-transmittance transparent conductive layer and a low-transmittance two-layer film sequentially formed on the transparent substrate, for example, on the front plate of a display device such as a cathode ray tube (CRT). It is related to the low transmittance transparent conductive substrate used, especially with good body color (film color, transmission spectrum) and high film strength, and also low reflectivity and antistatic, electric field shielding function, contrast An improvement effect can be added, and the low-transmission transparent conductive substrate that can reduce the production cost, its production method, the low-transparency transparent conductive layer forming coating solution used for the production of this substrate, and this The present invention relates to a display device to which a low transmittance transparent conductive substrate is applied.

  With the recent trend toward office automation, there are increasing opportunities to work in contact with cathode ray tubes (also referred to as CRTs) that are computer displays. This display is required to have a display screen that is easy to see and does not cause visual fatigue, and the display screen is also required to be easy to see in home color televisions.

  In order to satisfy these requirements, a process of reducing the transmittance of the front glass in the CRT and improving the contrast may be performed. In this case, a method using a face panel having a low transmittance (front glass of CRT) and a method of applying a coating film having a low transmittance to a face panel having a relatively high transmittance can be considered, but the transmittance of the CRT can be freely set. The latter method is advantageous in that it can be controlled.

  In recent years, with the flattening of CRT screens, a method has been adopted in which the transmittance is adjusted to a predetermined range lower than 100% (40 to 95%, preferably 65 to 75%) to improve the contrast of the image. Also in this case, the method of applying the coating film having the low transmittance is widely used. The reason for applying a low-transmittance coating film in the flat CRT is that the thickness of the face panel (front glass) is different between the central portion and the peripheral portion of the screen (the outer surface of the panel is flat and the inner surface has a curvature) When conventional colored glass (for example, semi-tinted glass, transmittance: about 53%) is used for the face panel, luminance in-plane nonuniformity occurs. Therefore, a high-transmittance panel glass and the above-described low-transmittance coating film are used. This is because, in combination, it is necessary to achieve both in-plane uniformity of luminance and improvement in contrast (contrast is improved when transmittance is lowered).

  On the other hand, as an attempt to make the display screen easier to see, an anti-glare treatment is applied to the face panel surface to suppress screen reflection. For example, this anti-glare treatment is also performed by a method of increasing the diffuse reflection of the surface by providing fine irregularities, but when this method is used, it is not preferable because the resolution is lowered and the image quality is lowered.

  Accordingly, it is preferable to perform the antiglare treatment by an interference method that controls the refractive index and the film thickness of the transparent film so that the reflected light causes destructive interference with the incident light. In order to obtain a low reflection effect by such an interference method, the optical film thicknesses of the high refractive index film and the low refractive index film are generally set to (1/4) λ, (1/4) λ, and (1/2). A two-layer structure film set to λ and (1/4) λ (λ: wavelength) is generally adopted.

  By the way, when working in contact with a display such as a CRT, in addition to the above-mentioned display screen being easy to see and not causing visual fatigue, it is also required that there is no dust adhesion or electric shock due to charging of the CRT surface. There is a case. In addition to these, recently, there are concerns about the adverse effects of low-frequency electromagnetic waves generated from CRTs on the human body, and it is desirable for CRTs to prevent such electromagnetic waves from leaking to the outside.

As a measure against such antistatic and electromagnetic wave leakage, a method of forming a transparent conductive layer on the front glass surface of the CRT has been adopted, but as a surface resistance of these transparent conductive layers, 10 ⁷ is used for antistatic. About 10 ¹⁰ Ω / □, and at least 10 ⁶ Ω / □ or less is desired for electromagnetic wave leakage prevention.

  Therefore, in order to meet the various requirements described above, carbon black fine particles having a primary particle diameter of 10 to 100 nm are used as black pigment fine particles, and a coating liquid in which the carbon black fine particles are dispersed in a solvent is applied to the front glass of the CRT. After drying, it is overcoated with a coating solution mainly composed of silica sol, etc., and is baked at a temperature of about 200 ° C. to form a low-permeability transparent conductive layer and a transparent coating layer containing carbon black fine particles. There has been proposed a method of obtaining a conductive and low-reflectance film by using a two-layer film (two-layer structure film) (see Patent Document 1).

Further, the low transmittance double-layer film having low resistance and low reflectance of 10 ⁴ units using a coating liquid in which carbon black fine particles having a specific surface area of 500 m ² / g or more and an average primary particle size of 5 to 200 nm are dispersed. A method for obtaining a (two-layer structure film) has also been proposed (see Patent Document 2).

  And even if any of these methods were applied, it was possible to obtain the desired good reflection / conducting characteristics.

  However, the low transmittance two-layer film (two-layer structure film) to which the carbon black fine particles are applied alone has an adverse effect that the transmission spectrum is lowered on the short wavelength side of visible light and becomes a brownish transmission color. In any of the above cases, as a method for neutralizing the transmission color of the film, a measure is taken of adding titanium oxynitride fine particles (blue-black pigment) to the coating solution in which the carbon black fine particles are dispersed.

  However, when a method of adding colored fine particles such as titanium oxynitride fine particles (blue-black pigment) to the coating liquid in which the carbon black fine particles are dispersed is employed, in order to compensate for the decrease in conductivity caused by the added colored fine particles, It was necessary to disperse extra carbon black fine particles in the coating solution, which was not a preferable method.

Further, in the latter method using a coating liquid in which carbon black fine particles having a specific surface area of 500 m ² / g or more and an average primary particle size of 5 to 200 nm are dispersed, the film formability deteriorated due to the high specific surface area of carbon black. There was also a problem that was likely to occur.
JP-A-7-281004 (Claims 1 to 10) JP-A-8-54502 (Claims 1 to 10)

  The present invention has been made paying attention to such problems, and the problem is that it has a good body color (film color, transmission spectrum), high film strength, and low reflectance. An antistatic, electric field shielding function, and a contrast improving effect can be added, and a low-transmission transparent conductive substrate that can reduce the manufacturing cost and a method for manufacturing the same are provided, and the substrate is used for manufacturing the substrate. An object of the present invention is to provide a coating liquid for forming a low transmittance transparent conductive layer and a display device to which a low transmittance transparent conductive substrate is applied.

  Therefore, in order to solve the above problems, the low-transmittance two-layer film (two-layer structure film) described in Patent Documents 1 and 2 has a low-transmittance transparent conductive layer containing carbon black fine particles, and a blue pigment. It is composed of a colored transparent coating layer containing fine particles and / or red pigment fine particles, the low transmittance transparent conductive layer bears only the conductive function, and the colored transparent coating layer is colored (color correction). As a result of adopting a structure that bears only the function, the inventors have found that the use of a small amount of a conductive component (carbon black fine particles) makes it possible to achieve a neutral transmission color, high film permeability, and excellent conductivity.

Furthermore, when the above-mentioned carbon black fine particles were used in combination with a low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and a high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g, It has been confirmed that a low-resistance conductive film can be obtained even in a region where the transmittance of the low-transmittance transparent conductive layer is high (thin film thickness is thin). I came to find that adjustment is possible. The present invention has been completed based on such technical findings.

That is, the invention according to claim 1
On the premise of a low transmittance transparent conductive base material comprising a transparent substrate, a low transmittance transparent conductive layer containing carbon black fine particles sequentially formed on the transparent substrate, and a low transmittance two-layer film comprising a transparent coating layer ,
The low transmittance transparent conductive layer is mainly composed of low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g, high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g, and a binder matrix. The coating layer is composed of a colored transparent coating layer mainly composed of blue pigment fine particles and / or red pigment fine particles and a binder matrix, and a reflectance that is minimal in the reflection spectrum in the visible light region is 2% or less. The low-transmittance two-layer film has a surface resistance and a visible light transmittance of 10 ⁵ to 10 ¹⁰ Ω / □ and 40 to 95%, respectively.

The invention according to claim 2
On the premise of the low transmittance transparent conductive substrate according to the invention of claim 1,
The high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g are ketjen black fine particles,
The invention according to claim 3
On the premise of the low transmittance transparent conductive substrate according to the invention of claim 1 or 2,
The mixing ratio of the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g is high relative to 100 parts by weight of the low specific surface area carbon black fine particles. The surface area carbon black fine particles are 5 to 200 parts by weight,
The invention according to claim 4
On the premise of the low transmittance transparent conductive substrate according to any one of claims 1 to 3,
The blue pigment fine particles or red pigment fine particles are composite oxide pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, isoindolinone pigments, azo pigments, phthalocyanine pigments, dioxazine pigments, cobalt violet, It is at least one kind of colored pigment fine particles selected from ultramarine, bitumen and titanium nitride,
The invention according to claim 5
Based on the low transmittance transparent conductive substrate according to the invention of claim 4,
The red pigment fine particle is a quinacridone pigment having a maximum absorption in a wavelength range of 570 to 585 nm,
The invention according to claim 6
Based on the low transmittance transparent conductive substrate according to any one of claims 1 to 5,
The binder matrix of the low-transmittance transparent conductive layer and the binder matrix of the colored transparent coating layer are characterized by comprising silicon oxide as a main component.

Next, the invention according to claim 7 provides:
Based on the manufacturing method of the above low transmittance transparent conductive substrate,
The solvent and low transmittance transparent consisting mainly of high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of specific surface area of 50 to 200 m ² / g dispersed in the solvent A conductive layer forming coating solution is applied on a transparent substrate, and then a colored transparent coating layer forming coating solution containing blue pigment particles and / or red pigment particles and an inorganic binder is applied, followed by heat treatment. And

The invention according to claim 8 is
Based on the manufacturing method of the low transmittance transparent conductive substrate according to the invention of claim 7,
The high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g are ketjen black fine particles,
The invention according to claim 9 is:
Based on the manufacturing method of the low transmittance transparent conductive substrate according to the invention of claim 7 or 8,
The mixing ratio of the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g is high relative to 100 parts by weight of the low specific surface area carbon black fine particles. The surface area carbon black fine particles are 5 to 200 parts by weight,
The invention according to claim 10 is:
Based on the manufacturing method of the low transmittance transparent conductive substrate according to any one of claims 7 to 9,
The low transmittance transparent conductive layer forming coating solution contains an inorganic binder constituting a binder matrix,
The invention according to claim 11 is:
Based on the manufacturing method of the low transmittance transparent conductive substrate according to any one of claims 7 to 10,
The inorganic binder of the coating liquid for forming a low-transmittance transparent conductive layer and the coating liquid for forming a colored transparent coating layer has silica sol as a main component.

Next, the invention according to claim 12 is:
Assuming the low transmittance transparent conductive layer forming coating liquid,
A solvent, as a main component a high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of the dispersed specific surface area 50 to 200 m ² / g in the solvent, the low specific surface area The mixing ratio of the carbon black fine particles and the high specific surface area carbon black fine particles is characterized in that the high specific surface area carbon black fine particles are 5 to 200 parts by weight with respect to 100 parts by weight of the low specific surface area carbon black fine particles.

The invention according to claim 13 is
Based on the low transmittance transparent conductive layer forming coating solution according to the invention of claim 12,
The high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g are ketjen black fine particles,
The invention according to claim 14 is:
Based on the low transmittance transparent conductive layer forming coating liquid according to the invention of claim 12 or 13,
An inorganic binder constituting the binder matrix is included.

The invention according to claim 15 is
Assuming a display device with a device body and a front plate arranged on the front side,
The low-transmittance transparent conductive substrate according to any one of claims 1 to 6 is incorporated as the front plate with the low-transmittance two-layer film side as an outer surface.

According to the low-transmittance transparent conductive substrate comprising the low-transmittance two-layer film composed of the low-transmittance transparent conductive layer and the transparent coat layer according to the inventions of claims 1 to 6,
The transparent transparent conductive layer is composed mainly of a low specific surface area carbon black fine particle having a specific surface area of 50 to ²⁰⁰ m ² / g, a high specific surface area carbon black fine particle having a specific surface area of 500 to 2000 m ² / g, and a binder matrix. Is composed of a colored transparent coating layer mainly composed of blue pigment fine particles and / or red pigment fine particles and a binder matrix, and has a reflectivity of 2% or less in the reflection spectrum in the visible light region, The low transmittance two-layer film has a surface resistance and a visible light transmittance of 10 ⁵ to 10 ¹⁰ Ω / □ and 40 to 95%, respectively.

  Therefore, it has a good body color (film color, transmission spectrum) and high film strength, and also has an effect of being able to improve the low reflectance, antistatic, electric field shielding function and contrast.

Moreover, according to the manufacturing method of the low transmittance | permeability transparent conductive base material which concerns on invention of Claims 7-11,
The solvent and low transmittance transparent consisting mainly of high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of specific surface area of 50 to 200 m ² / g dispersed in the solvent A conductive layer forming coating solution is applied on a transparent substrate, and then a colored transparent coating layer forming coating solution containing blue pigment particles and / or red pigment particles and an inorganic binder is applied, followed by heat treatment. And

  Therefore, it has the effect that the low-transmittance transparent conductive base material of Claims 1-6 can be manufactured reliably and at low cost.

Next, according to the coating liquid for forming a low transmittance transparent conductive layer according to the inventions of claims 12 to 14,
A solvent, as a main component a high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of the dispersed specific surface area 50 to 200 m ² / g in the solvent, the low specific surface area The mixing ratio of the carbon black fine particles and the high specific surface area carbon black fine particles is characterized in that the high specific surface area carbon black fine particles are 5 to 200 parts by weight with respect to 100 parts by weight of the low specific surface area carbon black fine particles.

  Therefore, it has the effect which can be provided to the manufacturing method of the low transmittance | permeability transparent conductive base material concerning this invention.

According to the display device of the invention described in claim 15,
The low-transmittance transparent conductive substrate according to any one of claims 1 to 6 is incorporated as a front plate with the low-transmittance two-layer film side as an outer surface.

  Therefore, a good body color (film color, transmission spectrum) and contrast can be improved, and a display device having low reflectance, antistatic, electric field shielding function and excellent weather resistance can be provided. Has an effect.

  Hereinafter, the present invention will be described in more detail.

First, the low-permeability transparent conductive substrate according to the present invention having a low-permeability two-layer film composed of a low-permeability transparent conductive layer and a transparent coating layer has a specific surface area of 50 to 200 m. ² / g low specific surface area carbon black fine particles, high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g, and a binder matrix as main components, and the transparent coating layer comprises blue pigment fine particles and / or red pigments It is composed of a colored transparent coating layer composed mainly of fine particles and a binder matrix, and has a minimum reflectance of 2% or less in the reflection spectrum in the visible light region. The light transmittance is 10 ⁵ to 10 ¹⁰ Ω / □ and 40 to 95%, respectively.

  In addition, as described above, the low-transmittance two-layer film in which carbon black fine particles are used alone has a problem of showing a brownish transmission color. Conventionally, a low-transmittance transparent conductive layer using both carbon black fine particles and colored fine particles is used. However, in the low transmittance transparent conductive substrate according to the present invention, only the conductive function is assigned to the low transmittance transparent conductive layer and only the coloring (color correction) function is assigned to the colored transparent coat layer. By applying a small amount of the conductive component (carbon black fine particles), the transmission color is neutral, and high film permeability and excellent conductivity are realized.

"Carbon black fine particles"
Hereinafter, the carbon black fine particles as the conductive fine particles applied in the present invention will be described in detail.

As described above, carbon black fine particles having a primary particle size of 10 to 100 nm such as furnace black described in Patent Document 1 have a relatively small specific surface area of 50 to 200 m ² / g. In the process of producing a coating liquid in which a low specific surface area carbon black fine particles are dispersed in a solvent (that is, a coating liquid for forming a low transmittance transparent conductive layer), the carbon black fine particles are easily dispersed and the dispersion stability is also improved. high.

  Therefore, when forming a coating liquid for forming a low-transmittance transparent conductive layer, coating defects such as aggregation defects (projections formed by agglomeration of carbon black fine particles), streaks (for forming a low-transmittance transparent conductive layer) There is an advantage that whitening (film with high haze) and the like hardly occur when the coating liquid is applied.

  However, since the structure structure (for example, a three-dimensional structure such as a bead-like structure) in the low specific surface area carbon black fine particles has not been developed, there is a drawback that the resistance value of the obtained low transmittance transparent conductive layer is increased.

On the other hand, carbon black fine particles (hereinafter referred to as high specific surface area carbon) such as Ketjen Black (trade name, manufactured by Ketjen Black International Co., Ltd.) having a relatively large specific surface area of 500 to 2000 m ² / g described in Patent Document 2. Black fine particles) have the above-mentioned structure development, so the resistance value of the low-transmittance transparent conductive layer can be lowered, but dispersion is difficult and dispersion stability compared to the above-mentioned low specific surface area carbon black fine particles. In other words, the above-described coating defects are likely to occur.

In the carbon black fine particles, if the specific surface area exceeds 2000 m ² / g, it is not practical because it becomes difficult to disperse in coating. On the other hand, when the specific surface area is less than 50 m ² / g, visible light scattering in the formed low-transmittance transparent conductive layer increases (that is, the haze value of the film increases), which is not practical.

  Therefore, the present invention solves these problems based on the following findings.

First, when low specific surface area carbon black fine particles (specific surface area = 137 m ² / g) are used as the conductive fine particles of the low transmittance transparent conductive layer, the film resistance value rapidly increases as the film thickness is reduced. While the transmittance (hereinafter referred to as critical transmittance) is about 75% (see curve A in FIG. 1), high specific surface area carbon black fine particles (Ketjen black fine particles, specific surface area = 800 m ² / g) This is a finding that when used, the critical transmittance can be increased to about 90% (see curve C in FIG. 1).

  Furthermore, even when a very small amount of the high specific surface area carbon black fine particles is added to the low specific surface area carbon black fine particles, the critical transmittance of the system can be greatly increased. For example, as understood from the curve (B) in FIG. 1, the criticality can be obtained by adding about 10 parts by weight of high specific surface area carbon black fine particles (Ketjen black fine particles) to 100 parts by weight of low specific surface area carbon black fine particles. The transmittance can be increased from about 75% to about 80%.

That is, as the conductive fine particles, by mixing a small amount of high specific surface area carbon black particles having a specific surface area of 50 to 200 m ² / g low specific surface area of carbon black particles the ratio of surface area 500~2000m ² / g, low transmittance transparent conductive layer Since a low-resistance conductive film can be obtained even in a region where the transmittance is high (thin film thickness is thin), it is possible to freely adjust the transmission color without deteriorating applicability.

  If the required resistance value can be set in a region where the transmittance of the low-transmittance transparent conductive layer is high (thin film thickness is thin), naturally, there is little brown coloring caused by the carbon black fine particles, and the colored transparent coat layer The content of the colored fine particles in the inside can be reduced, and the adjustment of the transmitted color itself is simplified. On the other hand, if the required resistance value can be obtained only in the region where the transmittance of the low-transmittance transparent conductive layer is low (thickness is thick), the coloring by the carbon black fine particles becomes strong, so in the colored transparent coat layer It is necessary to adjust the transmission color by increasing the content of the colored fine particles, and the amount of carbon black fine particles and colored fine particles in the low-transmittance two-layer film increases, so that the low-transmittance transparent conductive layer and the colored transparent coat The transmittance of the low-transmittance two-layer film composed of layers becomes low, causing a problem that a desired transmittance cannot be obtained.

Here, the mixing ratio of the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g is based on 100 parts by weight of the low specific surface area carbon black fine particles. The high specific surface area carbon black fine particles should be in the range of 5 to 200 parts by weight, preferably 8 to 100 parts by weight. If the amount is less than 5 parts by weight, the effect of adding high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g may not be sufficiently obtained. This is because, although the conductivity of the layer is improved, the film formability may be deteriorated and the filterability of the coating solution may be lowered due to the high structure of the high specific surface area carbon black fine particles.

"Low transmittance two-layer membrane"
Next, the surface resistance and visible light transmittance of the low-transmittance two-layer film composed of the low-transmittance transparent conductive layer and the colored transparent coat layer are 10 ⁵ to 10 ¹⁰ Ω / □ and 40 to 95%, respectively. (Claim 1). The surface resistance of the low-transmittance two-layer film is determined by the amount of carbon black fine particles blended in the low-transmittance transparent conductive layer forming coating solution and the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g. And a high specific surface area carbon black fine particle having a specific surface area of 500 to 2000 m ² / g. On the other hand, if the visible light transmittance of the low-transmittance two-layer film is less than 40%, the luminance of the CRT becomes too low, and conversely if it exceeds 95%, the contrast of the CRT deteriorates.

By the way, although the optical constants (n−ik, n: refractive index, i ² = −1, k: extinction coefficient) of the carbon black fine particles are not clear in the low transmittance transparent conductive substrate, a relatively large extinction is obtained. Low transmittance composed of carbon black fine particles that seem to have an extinction coefficient, a low-transmission transparent conductive layer mainly composed of a binder matrix, and a colored transparent coating layer mainly composed of silicon oxide and colored pigment fine particles A good low reflection characteristic can be obtained by the two-layer film structure. That is, if the thickness of the colored transparent coat layer is appropriately set (within a range of about 40 to 100 nm) with respect to the low transmittance transparent conductive layer having a predetermined film thickness (transmittance: 40 to 95%), the above low The reflectance (bottom reflectance) which becomes minimum in the reflection spectrum in the visible light region of the transparent transparent conductive substrate can be reduced to 2% or less (claim 1).

"Colored transparent coat layer, pigment"
Next, blue pigment fine particles or red pigment fine particles used for the colored transparent coating layer of the low transmittance two-layer film include composite oxide pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, and isoindolinone pigments. At least one or more kinds of colored pigment fine particles selected from pigments, azo pigments, phthalocyanine pigments, dioxazine pigments, cobalt violet, ultramarine blue, bitumen and titanium nitride can be used. The colored pigment fine particles preferably have an average particle size in the range of 10 to 150 nm. This is because when the average particle size is less than 10 nm, it is difficult to produce the fine particles, and at the same time, it may not be easy to disperse in coating. On the other hand, if the thickness exceeds 150 nm, visible light scattering of the formed low-transmission transparent conductive layer increases, and the haze value of the film increases, which may not be practical. In addition, the average particle diameter here has shown the average particle diameter of the microparticles | fine-particles observed with a transmission electron microscope (TEM).

  By the way, when the quinacridone pigment having the maximum absorption in the wavelength range of 570 to 585 nm is used as the red pigment fine particles, the quinacridone pigments blended in the colored transparent coating layer are CRT green (G: 540 nm) and red. Since the light in the wavelength region between the respective emission wavelengths (R: 630 nm) is selectively absorbed, there is an advantage that the contrast can be improved without lowering the luminance.

"Production method of low transmittance transparent conductive layer forming coating solution"
Next, the coating liquid for forming a low transmittance transparent conductive layer used for forming the low transmittance transparent conductive layer in the present invention can be produced by the following method.

First, as conductive fine particles, low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g are mixed with a dispersant and a solvent, Using a dispersing device such as a sand mill or an ultrasonic dispersing machine, a uniform dispersion of carbon black fine particles is obtained. The low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g may be mixed in advance and then subjected to the dispersion treatment. These may be dispersed separately and then mixed at an arbitrary ratio.

  Subsequently, the dispersion liquid of the carbon black fine particles is mixed with a solvent at a predetermined ratio to prepare a coating liquid for forming a low transmittance transparent conductive layer used for forming the low transmittance transparent conductive layer of the present invention. In addition, the inorganic binder which is a binder matrix component may be contained in this low-transmittance transparent conductive layer forming coating liquid, and the inorganic binder can be added during the dispersion treatment.

  Here, a material having silica sol as a main component can be applied to the inorganic binder, and the silica sol is a polymer obtained by hydrolyzing an orthoalkyl silicate with water or an acid catalyst to promote dehydration condensation polymerization, or A commercially available alkyl silicate solution that has already undergone hydrolysis-condensation polymerization to a tetramer to 5-mer can be used as a polymer obtained by further proceeding hydrolysis and dehydration condensation polymerization. As dehydration condensation polymerization proceeds, the solution viscosity increases and eventually solidifies. Therefore, the degree of dehydration condensation polymerization is less than the upper limit viscosity that can be applied on a transparent substrate such as a glass substrate or a plastic substrate. Prepare in place. However, the degree of dehydration condensation polymerization is not particularly specified as long as it is a level below the upper limit viscosity that can be applied on the transparent substrate, but in view of film strength, weather resistance and the like, a weight average molecular weight of about 500 to 3000 is preferable.

"Formation of a low-transmittance two-layer film"
Next, in order to form the low-transmittance two-layer film, this can be performed by the following method.

First, a solvent and, low permeability mainly comprising high specific surface area carbon black particles of low specific surface area of carbon black fine particles dispersed specific surface area 50 to 200 m ² / g in the solvent and specific surface area 500~2000m ² / g After applying a coating solution for forming a transparent conductive layer on a transparent substrate such as a glass substrate or a plastic substrate by a technique such as spray coating, spin coating, wire bar coating, doctor blade coating, etc., and drying as necessary Then, a coating solution for forming a colored transparent coating layer containing colored pigment fine particles of blue pigment fine particles and / or red pigment fine particles and silica sol is overcoated by the method described above. The silica sol can be the same as the silica sol applied to the inorganic binder described above.

  Then, after overcoating the coating solution for forming the colored transparent coating layer, for example, heat treatment is performed at a temperature of about 50 to 500 ° C., the coating solution for forming the colored transparent coating layer is cured, and the above low transmission A rate 2 layer film is formed.

Here, when the above-mentioned coating solution for forming a colored transparent coating layer containing colored pigment fine particles and silica sol or the like is overcoated by the above-described method, the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g previously applied and Includes overcoated colored pigment fine particles in a gap between carbon black fine particle layers formed by a coating solution for forming a low-permeability transparent conductive layer mainly composed of carbon black fine particles having a high specific surface area of 500 to 2000 m ² / g. When the silica sol liquid (this silica sol liquid becomes a binder matrix mainly composed of colored pigment fine particles and silicon oxide) is impregnated by the above heat treatment, the film strength and the weather resistance are improved at the same time.

  The silica sol solution containing the colored pigment fine particles of the blue pigment fine particles and / or the red pigment fine particles contains the colored pigment fine particles because the dehydration condensation polymerization reaction is almost completed at the time of heating and firing the low-transmittance two-layer film. It becomes a hard silicate film (film mainly composed of colored pigment fine particles and silicon oxide).

  Incidentally, it is also possible to change the reflectance of the low-transmittance bilayer film by adding magnesium fluoride fine particles, alumina sol, titania sol, zirconia sol, etc. to the silica sol and adjusting the refractive index of the colored transparent coating layer.

"Low transmittance transparent conductive substrate"
As described above, the low transmittance transparent conductive substrate according to the present invention includes a transparent substrate such as a glass substrate and a plastic substrate, and a low specific surface area carbon having a specific surface area of 50 to ²⁰⁰ m ² / g formed on the transparent substrate. A black pigment, a lower transparent transparent conductive layer mainly composed of carbon black fine particles having a specific surface area of 500 to 2000 m ² / g and a binder matrix, and a blue pigment formed on the low transparent transparent conductive layer The main part is composed of colored pigment fine particles of fine particles and / or red pigment fine particles and a low-transmittance two-layer film composed of an upper layer of a colored transparent coating layer mainly composed of a binder matrix.

And according to the low-transmittance transparent conductive substrate comprising the low-transmittance two-layer film, the low-transmittance two-layer film has a visible light transmittance of 40 to 95%, and the low-transmittance transparent conductive material The surface resistance of the layer can be set to 10 ⁵ to 10 ¹⁰ Ω / □, and the reflectance that can be minimized in the reflection spectrum in the visible light region of the low-transmittance transparent conductive substrate can be set to 2% or less. It becomes.

  Therefore, the low transmittance transparent conductive substrate according to the present invention has a good body color (film color, transmission spectrum) and high film strength, and also has a low reflectivity, antistatic property, electric field shielding function and contrast. Therefore, for example, it can be used for a front plate in a display device such as a cathode ray tube (CRT).

  Examples of the present invention will be specifically described below together with comparative examples. However, the present invention is not limited to these examples.

  Further, “%” in the text indicates “% by weight” excluding (%) of transmittance, reflectance, and haze value, and “part” indicates “part by weight”.

  In addition, the low transmittance | permeability 2 layer film comprised by the low transmittance | permeability transparent conductive layer and colored transparent coating layer which do not contain the transparent substrate (glass substrate) in the visible light wavelength range (380-780 nm) of the following Table 1 and drawing. Only the transmittance is obtained in the following (formula 1).

That is,
Transmittance (%) of low-transmittance two-layer film without transparent substrate
= [(Transmittance measured for each transparent substrate) / (Transmittance of transparent substrate)] × 100 (Equation 1)
Unless otherwise specified, the transmittance and the transmission spectrum are only the transmittance and the transmission spectrum of the low transmittance two-layer film composed of the low transmittance transparent conductive layer and the colored transparent coat layer.

  Furthermore, the haze value and the visible light transmittance are measured with a transparent substrate using a Murakami Color Research Laboratory haze meter (HR-200), and the reflectance and reflection / transmission spectrum are spectroscopic products manufactured by Hitachi, Ltd. Measured using a photometer (U-4000), and the dispersed particle size of the colored pigment fine particles in the dispersion was evaluated with a laser scattering particle size analyzer (ELS-800) manufactured by Otsuka Electronics Co., Ltd. Furthermore, the surface resistance of the low transmittance transparent conductive layer was measured using a surface resistance meter Loresta AP (MCP-T400) and Haresta IP (MCT-HT260) manufactured by Mitsubishi Chemical Corporation.

After mixing 5 g of carbon black fine particles [MA7, manufactured by Mitsubishi Chemical Corporation] with a specific surface area of 137 m ² / g and 0.5 g of a dispersant with 94.5 g of diacetone alcohol (DAA), paint shaker dispersion is performed together with zirconia beads. And a carbon black fine particle dispersion (liquid A) having a dispersion particle diameter of 124 nm was obtained.

In addition, 5 g of carbon black fine particles having a specific surface area of 800 m ² / g [Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd.] and 5 g of a dispersant are mixed with 90 g of pure water, and then the paint shaker is dispersed together with zirconia beads. A carbon black fine particle dispersion (liquid B) having a dispersed particle diameter of 160 nm was obtained.

  Next, 5 g of blue pigment fine particles [phthalocyanine blue # 5203, manufactured by Dainichi Seika Kogyo Co., Ltd.] and 0.5 g of a dispersant are mixed with 94.5 g of diacetone alcohol (DAA), and then a paint shaker together with zirconia beads. Dispersion was performed to obtain a blue pigment fine particle dispersion (liquid C) having a dispersion particle diameter of 120 nm.

  Also, after mixing 5 g of red pigment fine particles [quinacridone # 44, manufactured by Dainichi Seika Kogyo Co., Ltd.] and 0.5 g of a dispersant with 94.5 g of diacetone alcohol (DAA), dispersion of paint shaker with zirconia beads is performed. And a red pigment fine particle dispersion (liquid D) having a dispersion particle diameter of 135 nm was obtained.

Further, 19.6 parts of methyl silicate 51 (manufactured by Colcoat Co., Ltd .: trade name), 70.3 parts of ethanol, 7.9 parts of 1% nitric acid aqueous solution, and 2.2 parts of pure water were used to obtain SiO ₂ (silicon oxide). A silica sol liquid (E liquid) having a solid content concentration of 10% and a weight average molecular weight of 2200 was obtained.

Then, isopropyl alcohol (IPA), propylene glycol monomethyl ether (PGM), and diacetone alcohol (DAA) are added to 2.16 g of the above liquid A and 0.18 g of liquid B, and carbon black fine particles having a specific surface area of 137 m ² / g ( Hereinafter, it may be referred to as CB-1 fine particles) and carbon black fine particles having a specific surface area of 800 m ² / g (hereinafter also referred to as CB-2 fine particles). CB-1: 0.108%, CB-2: 0.009%, water: 0.16%, IPA: 77.6%, PGM: 15%, DAA: 7.0%).

As a result of observing the obtained coating liquid for forming a low transmittance transparent conductive layer with a transmission electron microscope, the carbon black fine particles having a specific surface area of 137 m ² / g have an average particle diameter of 24 nm and a specific surface area of 800 m ² / g. It was a shape in which particles of 10 to 50 nm were connected in a chain.

  Next, ethanol (EA), propylene glycol monomethyl ether (PGM), and diacetone alcohol (DAA) are added to 0.32 g of the above liquid C, 0.94 g of liquid D, and 10.7 g of liquid E, and blue pigment fine particles, Colored transparent coating layer forming coating solution containing red pigment fine particles and inorganic binder (silicon oxide: 1.07%, blue pigment fine particles: 0.016%, red pigment fine particles: 0.047%, water: 2 0.09%, EA: 60.0%, PGM: 24.3%, DAA: 10.9%).

  As a result of observing the obtained coating solution for forming a colored transparent coating layer with a transmission electron microscope, the particle size of the blue pigment fine particles was 10 to 60 nm, and the particle size of the red pigment fine particles was 10 to 90 nm.

Then, a low transmittance transparent conductive layer forming coating liquid containing carbon black fine particles having a specific surface area of 137 m ² / g and carbon black fine particles having a specific surface area of 800 m ² / g was heated to 40 ° C. (thickness 3 mm). Spin coating (150 rpm, 60 seconds), and then a coating solution for forming a colored transparent coating layer containing blue pigment fine particles, red pigment fine particles and an inorganic binder is spin coated (150 rpm, 70 seconds), and further cured at 180 ° C. for 30 minutes, a low transmittance transparent conductive layer containing carbon black fine particles having a specific surface area of 137 m ² / g and carbon black fine particles having a specific surface area of 800 m ² / g, and a blue pigment With a low-transmittance two-layer film composed of fine particles, red pigment fine particles, and a colored transparent coating layer mainly composed of silicon oxide Glass substrate, i.e., to obtain a low permeability transparent conductive material according to Example 1.

  Table 1 below shows the film characteristics (surface resistance, visible light transmittance, haze value, color index of transmitted color, bottom reflectance / bottom wavelength) of the low transmittance two-layer film formed on the glass substrate.

  In Table 1, the bottom reflectance means a minimum reflectance in the reflection spectrum of the low transmittance transparent conductive substrate, and the bottom wavelength means a wavelength at which the reflectance is a minimum. Moreover, the reflection spectrum of the low transmittance | permeability transparent conductive base material which concerns on Example 1 is shown in FIG. 2, and a transmission spectrum is shown in FIG.

In Example 1, A solution 1.8 g, B solution in Example 1 with the same specific surface area 137m ² / g carbon black particles and carbon black having a specific surface area of 800 m ² / g of the procedure except that the 0.46g of Low transmittance transparent conductive layer forming coating solution containing fine particles (CB-1: 0.09%, CB-2: 0.023%, water: 0.41%, IPA: 77.7%, PGM: 15 %, DAA: 6.7%), a low transmittance transparent conductive layer containing carbon black fine particles with a specific surface area of 137 m ² / g and carbon black fine particles with a specific surface area of 800 m ² / g, blue pigment fine particles, A glass substrate with a low-transmittance double-layer film composed of red pigment fine particles and a colored transparent coat layer mainly composed of silicon oxide, that is, a low-transmittance transparent conductive substrate according to Example 2 was obtained. .

  Table 1 shows the film characteristics of the low transmittance transparent conductive layer formed on the glass substrate.

In Example 1, A solution 1.2 g, B solution in Example 1 with the same specific surface area 137m ² / g carbon black particles and carbon black having a specific surface area of 800 m ² / g of the procedure except that the 0.9g of Low transmittance transparent conductive layer forming coating solution containing fine particles (CB-1: 0.06%, CB-2: 0.045%, water: 0.81%, IPA: 77.8%, PGM: 15 %, DAA: 6.1%), a low transmittance transparent conductive layer containing carbon black fine particles with a specific surface area of 137 m ² / g and carbon black fine particles with a specific surface area of 800 m ² / g, blue pigment fine particles, A glass substrate with a low transmittance two-layer film composed of red pigment fine particles and a colored transparent coating layer mainly composed of silicon oxide, that is, a low transmittance transparent conductive substrate according to Example 3 was obtained. .

Table 1 shows the film characteristics of the low transmittance transparent conductive layer formed on the glass substrate.
[Comparative Example 1]
Formation of a low-transmittance transparent conductive layer containing carbon black fine particles having a specific surface area of 137 m ² / g in the same manner as in Example 1 except that 2.4 g of liquid A was used and liquid B was not applied. A coating solution (CB-1: 0.12%, IPA: 77.5%, PGM: 15%, DAA: 7.3%) containing carbon black fine particles having a specific surface area of 137 m ² / g. A glass substrate with a low-transmittance two-layer film composed of a transparent transparent conductive layer and a colored transparent coating layer mainly composed of blue pigment fine particles, red pigment fine particles and silicon oxide; Such a low transmittance transparent conductive substrate was obtained.

Table 1 shows the film characteristics of the low transmittance transparent conductive layer formed on the glass substrate.
[Comparative Example 2]
A low-transmission transparent conductive material containing carbon black fine particles having a specific surface area of 800 m ² / g in the same manner as in Example 1, except that the liquid A was not applied and 2.4 g of the liquid B was used. A layer-forming coating solution (CB-2: 0.091%, water: 1.64%, IPA: 78.1%, PGM: 15%, DAA: 5%) was prepared, and the specific surface area was 800 m ² / g. A glass substrate with a low-transmittance two-layer film comprising a low-transmittance transparent conductive layer containing carbon black fine particles and a colored transparent coating layer mainly composed of blue pigment fine particles, red pigment fine particles and silicon oxide That is, a low transmittance transparent conductive substrate according to Comparative Example 2 was obtained.

  However, when the coating liquid for forming a low transmittance transparent conductive layer according to Comparative Example 2 is applied, many fine black spots are observed on the coated surface, and further, spiral defects (that part is transparent on the periphery of the glass substrate). The rate was low).

Table 1 shows the film characteristics of the low transmittance transparent conductive layer formed on the glass substrate.
[Comparative Example 3]
In Example 1, ethanol (EA) and propylene glycol monomethyl ether (PGM) were added to 11 g of E liquid, and the coating liquid for forming a transparent coat layer containing no inorganic pigment and blue pigment fine particles and red pigment fine particles ( (Silicon oxide: 1.1%, water: 2.15%, EA: 36.7%, PGM: 25%, DAA: 10%) were prepared and replaced with the coating solution for forming the colored transparent coating layer of Example 1. The low transmittance containing carbon black fine particles having a specific surface area of 137 m ² / g and carbon black fine particles having a specific surface area of 800 m ² / g was obtained by the same procedure as in Example 1 except that the coating liquid for forming the transparent coat layer was used. A glass substrate with a low transmittance two-layer film composed of a transparent conductive layer and a transparent coating layer containing silicon oxide as a main component, that is, a low transmittance transparent conductive substrate according to Comparative Example 3 It was.

  Table 1 shows the film characteristics of the low transmittance transparent conductive layer formed on the glass substrate.

  Moreover, the reflection spectrum of the low transmittance | permeability transparent conductive base material concerning the comparative example 3 is shown in FIG. 4, and the transmission spectrum is shown in FIG.

注１：[比表面積５０〜２００ｍ²／ｇの低比表面積カーボンブラック微粒子の重量]／[比表面積５００〜２０００ｍ²／ｇの高比表面積カーボンブラック微粒子の重量]を示す。

Note 1: [Weight of low specific surface area carbon black fine particles with specific surface area of 50 to ²⁰⁰ m ² / g] / [Weight of high specific surface area carbon black fine particles with specific surface area of 500 to 2000 m ² / g].

  Note 2: This indicates the type of colored pigment fine particles of the “colored transparent coat layer”, B indicates a blue pigment, and V indicates a magenta pigment.

[Weather resistance test]
The low-permeability transparent conductive substrate according to Examples 1 to 3 was immersed in a 10% aqueous sodium chloride solution, a 50% aqueous acetic acid solution and a 5% aqueous ammonia solution for 24 hours, and transmitted through a film provided on a transparent substrate (glass substrate). The rate and appearance were examined, but no change was observed.

[Membrane strength test]
Although the low-transmittance transparent conductive base materials according to Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by a pencil hardness test (load 1 kg), all were 8H or more.

[Evaluation]
(1) Low transmittance transparent conductivity according to Examples 1 to 3 and Comparative Examples 1 to 2 from the data in the “color index of transmitted color”, “haze value”, and “visible light transmittance” columns shown in Table 1 Each of the substrates was confirmed to have a good body color (film color, transmission spectrum) and a contrast improving effect, and from the data in the “surface resistance” column shown in Table 1, Examples 1-3 and It is confirmed that the low transmittance transparent conductive base materials according to Comparative Examples 2 to 3 have antistatic and electric field shielding functions.

In addition, from the results of the “bottom reflectance / bottom wavelength” column of Table 1 and the “film strength test”, the low transmittance transparent conductive base materials according to Examples 1 to 3 and Comparative Examples 1 to 3 have low reflection. It is also confirmed that the low transmittance transparent conductive substrate according to Examples 1 to 3 has sufficient weather resistance from the results of the “weather resistance test”. It is also confirmed.
(2) On the other hand, in the low transmittance transparent conductive substrate according to Comparative Example 3 in which the colored transparent coat layer is not formed, “b ^* ” in the “color index of transmitted color” column is a high value of +5.24. It is confirmed that the body color (film color, transmission spectrum) is inferior.

  Moreover, in the low transmittance transparent conductive substrate according to Comparative Example 1 in which only the low specific surface area carbon black fine particles are applied, the surface resistance is 3100 MΩ / □ and the antistatic and electric field shielding functions are insufficient. Therefore, it is confirmed that there is a need to increase the blending ratio of carbon black.

  Furthermore, in the low-transmittance transparent conductive substrate according to Comparative Example 2 in which only the high specific surface area carbon black fine particles are applied, many fine black spots are seen on the coated surface, and spiral defects are present in the periphery of the glass substrate. It is confirmed that a coating defect occurs so that (the part has low transmittance) can be seen.

  The low-transmission transparent conductive substrate according to the present invention has a good body color (film color, transmission spectrum) and high film strength as described above, and also has a low reflectance, antistatic property, and electric field shielding function. In addition, since an effect of improving contrast can be added, it can be suitably used for a front plate or the like in a display device such as a cathode ray tube (CRT).

The graph which shows the relationship between the film | membrane transmittance | permeability and film resistance value in the transparent conductive film to which the low specific surface area carbon black fine particle and the high specific surface area carbon black fine particle were applied. The graph which shows the reflection spectrum of the low transmittance | permeability transparent conductive base material concerning Example 1. FIG. The graph which shows the transmission spectrum of the low transmittance | permeability transparent conductive base material which concerns on Example 1. FIG. The graph which shows the reflection spectrum of the low transmittance | permeability transparent conductive base material which concerns on the comparative example 3. FIG. The graph which shows the transmission spectrum of the low transmittance | permeability transparent conductive base material which concerns on the comparative example 3. FIG.

Claims (15)

In a low-transmittance transparent conductive base material comprising a transparent substrate, a low-transmittance transparent conductive layer containing carbon black fine particles sequentially formed on the transparent substrate, and a low-transmittance two-layer film comprising a transparent coat layer,
The low transmittance transparent conductive layer is mainly composed of low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g, high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g, and a binder matrix. The coating layer is composed of a colored transparent coating layer mainly composed of blue pigment fine particles and / or red pigment fine particles and a binder matrix, and a reflectance that is minimal in the reflection spectrum in the visible light region is 2% or less. A low transmittance transparent conductive substrate, wherein the low transmittance two-layer film has a surface resistance and a visible light transmittance of 10 ⁵ to 10 ¹⁰ Ω / □ and 40 to 95%, respectively. ^2. The low transmittance transparent conductive substrate according to claim 1, wherein the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m < ² > / g are ketjen black fine particles. The mixing ratio of the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g is high relative to 100 parts by weight of the low specific surface area carbon black fine particles. The low-transmittance transparent conductive substrate according to claim 1 or 2, wherein the surface area carbon black fine particles are 5 to 200 parts by weight.   The blue pigment fine particles or red pigment fine particles are composite oxide pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, isoindolinone pigments, azo pigments, phthalocyanine pigments, dioxazine pigments, cobalt violet, The low transmittance transparent conductive substrate according to any one of claims 1 to 3, which is at least one kind of colored pigment fine particles selected from ultramarine, bitumen and titanium nitride.   The low-transmittance transparent conductive substrate according to claim 4, wherein the red pigment fine particles are quinacridone pigments having maximum absorption in a wavelength range of 570 to 585 nm.   The low transmittance transparent conductive group according to any one of claims 1 to 5, wherein the binder matrix of the low transmittance transparent conductive layer and the binder matrix of the colored transparent coat layer are mainly composed of silicon oxide. Wood. The solvent and low transmittance transparent consisting mainly of high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of specific surface area of 50 to 200 m ² / g dispersed in the solvent A conductive layer forming coating solution is applied on a transparent substrate, and then a colored transparent coating layer forming coating solution containing blue pigment particles and / or red pigment particles and an inorganic binder is applied, followed by heat treatment. A method for producing a low-transmittance transparent conductive substrate. 8. The method for producing a low transmittance transparent conductive substrate according to claim 7, wherein the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m < ² > / g are ketjen black fine particles. The mixing ratio of the low specific surface area carbon black fine particles having a specific surface area of 50 to ²⁰⁰ m ² / g and the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m ² / g is high relative to 100 parts by weight of the low specific surface area carbon black fine particles. The method for producing a low-transmittance transparent conductive substrate according to claim 7 or 8, wherein the surface area carbon black fine particles are 5 to 200 parts by weight.   10. The low transmittance transparent conductive substrate according to claim 7, wherein the coating liquid for forming a low transmittance transparent conductive layer contains an inorganic binder constituting a binder matrix. Method.   The low-transmittance transparent according to any one of claims 7 to 10, wherein the inorganic binder of the low-transmittance transparent conductive layer forming coating liquid and the colored transparent coat layer-forming coating liquid is mainly composed of silica sol. A method for producing a conductive substrate. A solvent, as a main component a high specific surface area carbon black particles of low specific surface area of carbon black particles and a specific surface area 500~2000m ² / g of the dispersed specific surface area 50 to 200 m ² / g in the solvent, the low specific surface area Low transmittance transparent conductive, wherein the mixing ratio of carbon black fine particles and high specific surface area carbon black fine particles is 5 to 200 parts by weight of high specific surface area carbon black fine particles with respect to 100 parts by weight of low specific surface area carbon black fine particles Coating liquid for layer formation. 13. The coating liquid for forming a low transmittance transparent conductive layer according to claim 12, wherein the high specific surface area carbon black fine particles having a specific surface area of 500 to 2000 m < ² > / g are ketjen black fine particles.   The coating liquid for forming a low-transmittance transparent conductive layer according to claim 12 or 13, wherein an inorganic binder constituting the binder matrix is contained. In a display device comprising an apparatus main body and a front plate arranged on the front side,
A display device, wherein the low-transmittance transparent conductive substrate according to any one of claims 1 to 6 is incorporated as the front plate with the low-transmittance two-layer film side as an outer surface.

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