JP2003301141A - Coating liquid for forming transparent electroconductive layer having low transmittance and front panel of display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid which can inexpensively form a low- resistant, transparent electroconductive layer having a low transmittance in order to enhance uniformity of luminance in a plane and contrast in correspondence to planarization of a front panel of a CRT, and the like. <P>SOLUTION: The coating liquid for forming the transparent electroconductive layer having the low transmittance comprises, as the main component of an electroconductive fine particle dispersed in a solvent, a linear carbon fine particle having a length of 10-1,000 nm, preferably a ketchen black fine particle or a carbon nanotube fine particle. A face panel equipped with a transparent two-layer film comprising the transparent electroconductive layer having the low transmittance manufactured by using the coating liquid and a transparent coat layer is suitable as a flat face panel of the CRT, or the like. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cathode ray tube (CR
The present invention relates to a low-transmittance transparent conductive layer applied to a front plate of a display device such as T), particularly a flat type front plate, and a coating liquid for forming a low-transmittance transparent conductive layer suitable for the formation thereof.

[0002]

2. Description of the Related Art At present, a cathode ray tube (also referred to as a CRT or a cathode ray tube) used as a display device for a computer, a television or the like has a display screen which is easy to see and does not cause visual fatigue, and dust adhesion due to electrification or electric shock. No shock is required. Recently, in addition to these, there is a concern that a low-frequency electromagnetic wave generated from a CRT may adversely affect the human body, and it is also desired that such an electromagnetic wave does not leak to the outside.

As a measure against such charging prevention and leakage electromagnetic wave prevention (shielding of electric field), a transparent conductive layer is formed on the surface of the front plate made of, for example, glass of a display device. For example, in a CRT, it is necessary to form a transparent conductive layer having a low resistance of 10 ⁸ Ω / □ or less for antistatic purposes and at least 10 ⁶ Ω / □ or less for electric field shielding.

Although several proposals have been made for the above-mentioned low resistance transparent conductive layer, antimony tin oxide (ATO).
Generally, a transparent conductive layer containing conductive oxide fine particles such as indium tin oxide (ITO) as a main component is used. That is, a coating liquid in which conductive oxide fine particles such as ITO are dispersed in a solvent is applied to a front glass plate of a CRT and dried, and then a coating liquid for forming a transparent coating layer containing silica sol as a main component is applied and dried. The most widely used method is to form a transparent two-layer film composed of a transparent conductive layer and a transparent coat layer by firing at a temperature of about 200 ° C.

In order to make the display screen easier to see, C
In RT, for example, the surface of the front plate is subjected to an antiglare treatment to suppress reflection on the screen. As this antiglare treatment, a method of providing fine irregularities to increase the diffuse reflection on the surface can be used, but it is not preferable because it lowers the resolution and the image quality. As a preferred antiglare treatment, there is an interferometry method in which the refractive index and the film thickness of the transparent film are controlled 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 λ / 4 and λ / 4, or λ / 2 and λ, respectively. The two-layer structure set to / 4 is adopted, and the transparent conductive layer made of ITO fine particles in the above-mentioned transparent two-layer film is also used as this kind of high refractive index film.

Recently, the front plate of the CRT is rapidly changing from the conventional curved type to the flat type. In this flat type front plate (face panel), the outer surface of the panel is a flat surface, while the inner surface is a curved surface having a predetermined curvature, so that the thickness is thin in the central portion of the screen and thick in the peripheral portion. There is.

Therefore, a conventional colored glass (for example, semi-tinted glass, transmittance: about 5) is used for the flat type front plate.
3%), there is a problem that in-plane non-uniformity of luminance occurs due to the difference in thickness. As a solution to this problem, it has been studied to improve the in-plane uniformity of brightness by reducing the transmittance of the transparent conductive layer of the transparent two-layer film applied to the front plate. By reducing the transmittance of this transparent conductive layer, the contrast of the screen is simultaneously improved.

In order to achieve uniform in-plane luminance and improvement of contrast in this flat type front plate,
It is necessary to adjust the transmittance of the transparent conductive layer to a predetermined range lower than 100%, specifically about 40 to 75%.

[0010]

In response to the demand for uniforming the in-plane brightness and improving the contrast in the above-mentioned flat type front plate, it has been studied to color the transparent conductive layer to reduce the transmittance. There is. That is, attempts have been made to add black pigment fine particles such as carbon black and titanium black to a coating liquid for forming a transparent conductive layer in which antimony tin oxide (ATO) or indium tin oxide (ITO) is dispersed in a solvent. There is.

However, in the low-transmittance transparent conductive layer formed by using the coating liquid containing such black pigment fine particles, the black pigment fine particles prevent the ATO fine particles and the ITO fine particles from contacting each other, and the resistance of the transparent conductive layer is reduced. It had the drawback of rising. On the other hand, in order to maintain the resistance of the transparent conductive layer at a low level, it is necessary to use a large amount of ATO fine particles or ITO fine particles, which is disadvantageous in that the production cost of the transparent conductive film is increased.

The present invention has been made in view of the above-mentioned conventional circumstances, and has a low transmissivity transparent electroconductivity necessary for uniforming the in-plane brightness and improving the contrast accompanying the flattening of the front plate of a CRT or the like. An object of the present invention is to provide a coating liquid for forming a low transmittance transparent conductive layer, which can form a layer at low cost while maintaining low resistance.

[0013]

In order to achieve the above object, the coating liquid for forming a low transmittance transparent conductive layer provided by the present invention has a length of 10 to 10 as a main component of conductive fine particles dispersed in a solvent. It is characterized by containing chain-like carbon fine particles of 1000 nm.

In the coating liquid for forming a low transmittance transparent conductive layer of the present invention, the chain carbon fine particles are Ketjen black fine particles or carbon nanotube fine particles. Further, the coating liquid for forming a low transmittance transparent conductive layer of the present invention may further contain colored pigment fine particles.

Further, the present invention is a front plate for a display device, comprising a transparent two-layer film comprising a low transmittance transparent conductive layer and a transparent coat layer on a transparent substrate, which is included in the low transmittance transparent conductive layer. The present invention provides a front plate for a display device, characterized in that the main component of the conductive fine particles is chain carbon fine particles having a length of 10 to 1000 nm.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention did not use ATO, ITO, etc., which have been conventionally used as conductive fine particles, and required a low transmittance transparent conductive layer for flattening a front plate such as a CRT. As a result of investigating a method of forming a very low cost while maintaining low resistance, it was found that chain carbon fine particles are effective as the conductive fine particles.

That is, in the coating liquid for forming a low-transmittance transparent conductive layer of the present invention, chain carbon fine particles having a length of 10 to 1000 nm formed by chaining primary particles are used as a main component of the conductive fine particles. The chain-like carbon fine particles have a strong coloring power and can effectively reduce the transmittance of the transparent conductive film even when added in a small amount, and also form a conductive path having a mesh structure in the transparent conductive layer, which is necessary for electric field shielding. It is possible to maintain resistance.

The chain carbon fine particles have a length of 10 to 10
The range is 00 nm, preferably 50 to 500 nm. When the length of the chain-like carbon fine particles is less than 10 nm, the conductive path of the mesh structure is not sufficiently formed and the resistance of the transparent conductive film becomes high. On the contrary, when it exceeds 1000 nm, the low transmittance transparent conductive layer is formed. It is not practical because filtration of the coating liquid with a filter becomes difficult, and at the same time, aggregates are easily formed and a film defect is likely to occur during coating and drying of the coating liquid. The length of the carbon fine particles mentioned here indicates the length of the fine particles observed by a transmission electron microscope (TEM).

Specifically, the chain carbon fine particles are preferably Ketjen black fine particles or carbon nanotube fine particles. The Ketjen black fine particles or carbon nanotube fine particles are particularly preferable as the conductive fine particles used in the present invention because they have a chain structure (structure structure) developed.

Further, the color of the film of the transparent conductive film can be adjusted by adding fine particles of colored pigment to the coating liquid for forming the low transmittance transparent conductive layer. Such colored pigment fine particles include titanium black, titanium nitride, complex oxide pigments, cobalt violet, molybdenum orange, ultramarine blue, dark blue, quinacridone pigments, anthraquinone pigments, perylene pigments, isoindolinone pigments, azo pigments. One or more types of fine particles selected from pigments and phthalocyanine pigments are used.

Next, the coating liquid for forming a low transmittance transparent conductive layer according to the present invention can be manufactured by the following method. That is, the chain carbon fine particles are mixed with a dispersant and a solvent, and a dispersion treatment is performed using a disperser such as a paint shaker, a sand mill, an ultrasonic disperser, etc. to obtain a uniform dispersion liquid, and further if necessary. Dilute with a solvent to adjust the composition and viscosity.

Further, in order to form a low-transmittance transparent conductive layer, this coating solution is applied onto a transparent substrate by a technique such as spray coating, spin coating, wire bar coating, doctor blade coating, etc., and if necessary. Dry and heat cure. A glass substrate, a plastic substrate, or the like can be used as the transparent substrate.

As a preferred method for forming a transparent two-layer film comprising a low-transmittance transparent conductive layer and a transparent coat layer, as described above, a low-transmittance transparent conductive layer-forming coating liquid containing chain carbon fine particles as a main component is transparent. After coating on a substrate and drying if necessary, a coating liquid for forming a transparent coating layer containing silica sol as a main component is overcoated by the same method. Then, for example, a heat treatment is performed at a temperature of about 50 to 500 ° C. to cure the transparent coating layer forming coating liquid to form a transparent two-layer film.

In forming this transparent two-layer film, when a coating liquid for forming a transparent coating layer containing silica sol as a main component is overcoated, it is formed by a coating liquid for forming a transparent conductive layer having a low transmittance previously applied. The silica sol liquid overcoated permeates the interstices of the chain carbon fine particle layer. Therefore, the silica sol liquid that has permeated the interstices of the chain-like carbon fine particle layer becomes a binder matrix containing silicon oxide as the main component by the subsequent heat treatment, and the strength of the transparent two-layer film and the further improvement of the weather resistance are simultaneously improved. To be achieved.

Although the optical constant (n-ik) of the low-transmissivity transparent conductive layer dispersed in the above-mentioned binder matrix composed mainly of chain-like carbon fine particles and silicon oxide is not clear, the low-transmissivity transparent conductive layer is not clear. Due to the two-layer film structure of the layer and the transparent coat layer, the reflectance of the transparent two-layer film can be significantly reduced.

As the silica sol applied to the coating liquid for forming the transparent coating layer, a partially hydrolyzed polymer obtained by adding water or an acid catalyst to orthoalkyl silicate to hydrolyze it to promote dehydration polycondensation, or already 4 to 4 parts. It is possible to use a commercially available alkyl silicate solution that has undergone hydrolysis condensation polymerization to a pentamer, or a partially hydrolyzed polymer that has undergone hydrolysis and dehydration condensation polymerization.

If the dehydration polycondensation proceeds too much, the solution viscosity rises and eventually solidifies. Therefore, the degree of the dehydration polycondensation is adjusted to be below the upper limit viscosity that can be applied on a transparent substrate. The degree of dehydration polycondensation is 500 to 3000 in terms of weight average molecular weight in consideration of film strength and weather resistance.
The degree is preferable, but it is not particularly limited as long as it is at a lower level.

The partially hydrolyzed polymer of an alkyl silicate undergoes a dehydration polycondensation reaction when heated and baked, and becomes a hard silicate film (a film containing silicon oxide as a main component).
It is also possible to add magnesium fluoride fine particles, alumina sol, titania sol, zirconia sol, etc. to the silica sol to adjust the refractive index of the transparent coating layer to change the reflectance of the transparent two-layer film.

By using the coating liquid for forming a low transmittance transparent conductive layer according to the present invention, a transparent two-layer film including a low transmittance transparent conductive layer formed on a transparent substrate and a transparent coating layer provided thereon. Can be formed at extremely low cost, while maintaining excellent conductivity with low resistance required for electric field shield, etc.
It is possible to obtain the low transmittance required for the in-plane uniformity of the brightness and the improvement of the contrast due to the flattening of the front plate such as a CRT.

[0030]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. In the text, "%" means "% by weight" excluding transmittance, reflectance and haze value, and "part" means "part by weight". The term "transmittance" means the transmittance of only a transparent two-layer film that does not include a transparent substrate, unless otherwise specified.

[0031]Example 1 Chain carbon particles (Ketjen Black EC, Mitsubishi
Gaku Co., Ltd.) 10 g and a dispersant 3.3 g, water 86.7
Mix with g and paint shaker with zirconia beads
-After dispersion, dilute with ethanol (EA) and chain
Obtained carbon fine particle dispersion (carbon: 2%) (solution A)
It was

Ethanol and water were added to this liquid A to form a coating liquid for forming a low transmittance transparent conductive layer (carbon: 0.15%, water:
7.4%, EA: 92.4%). As a result of observing the chain carbon fine particles in the obtained coating liquid for forming a low transmittance transparent conductive layer with a transmission electron microscope, it was a long chain shape having a width of 20 to 50 nm and a length of 50 to 300 nm.

Next, this low-transmittance transparent conductive layer forming coating solution was spin-coated on a glass substrate (soda lime glass having a thickness of 3 mm) heated at 40 ° C. at 150 rpm for 120 seconds, and then, continuously. , Silica sol liquid 150r
It was spin-coated at pm for 60 seconds. Then, it is cured at 180 ° C. for 30 minutes to form a glass substrate with a transparent two-layer film composed of a low-transmissivity transparent conductive layer containing chain carbon fine particles and a transparent coating layer containing silicon oxide as a main component. ,
That is, a low transmittance transparent conductive substrate of Sample 1 was obtained.

The silica sol liquid was oxidized using 19.6 parts of methyl silicate 51 (trade name of Colcoat Co.), 57.8 parts of ethanol, 7.9 parts of 1% nitric acid aqueous solution, and 14.7 parts of pure water. Silicon (SiO ₂ ) solid content concentration of 10%,
Weight were prepared in average molecular weight 1050, eventually a mixture of SiO ₂ solid content concentration of 1.0% and becomes as isopropyl alcohol (IPA) n-butanol (NBA) (I
It was obtained by diluting with PA / NBA = 3/1).

Regarding the film characteristics of the transparent two-layer film formed on the glass substrate of Sample 1 above, the visible light transmittance, haze value, bottom reflectance / bottom wavelength, and surface resistance were determined, and the results are shown below together with the results of other samples. The results are shown in Table 1. The bottom reflectance means the minimum reflectance in the reflection profile of the coating liquid for forming a low transmittance transparent conductive layer, and the bottom wavelength means the wavelength at which the reflectance is minimum.

In Table 1, the visible light wavelength range (3
The transmittance of only the transparent two-layer film which does not include the transparent substrate (glass substrate) in 80 to 780 nm) is determined as follows. That is, the transmittance (%) of only the transparent two-layer film =
[(Transmittance of each transparent substrate) / (Transmittance of transparent substrate)]
× 100 Moreover, the haze value and the transmittance of each transparent substrate were measured using a haze meter (HR-200) manufactured by Murakami Color Research Laboratory. The reflectance and the reflection / transmission profile were measured using a spectrophotometer (U-4000) manufactured by Hitachi, Ltd. The surface resistance of the transparent two-layer film was measured using a surface resistance meter HALESTA IP (MCP-HT260) manufactured by Mitsubishi Chemical Corporation. The particle shape of the chain carbon fine particles was evaluated using a transmission electron microscope manufactured by JEOL Ltd.

[0037]Example 2 Phthalocyanine blue fine particles (5203, Dainichi Seika Kogyo
(Manufactured by K.K.) and 1 g of a dispersant were mixed with ethanol (E
A) Mix with 94g and pay with zirconia beads
Ant shaker dispersion to obtain a phthalate with a dispersed particle size of 96 nm.
Cyanine blue fine particle dispersion liquid (B liquid) was obtained.

The liquid A (chain carbon fine particle dispersion liquid) obtained in Example 1 above, ethanol, and water were added to the liquid B to prepare a coating liquid for forming a low transmittance transparent conductive layer (carbon: 0. 1
5%, Phthalocyanine Blue: 0.03%, Water: 7.4
%, EA: 92.4%). The chain-like carbon fine particles in the coating liquid for forming a low transmittance transparent conductive layer have a width of 20 to 50 nm and a length of 50 to 300, as in Example 1.
It had a long chain shape of nm.

Using this low-transmittance transparent conductive layer forming coating solution, in the same manner as in Example 1, a low-transmittance transparent conductive layer containing chain carbon fine particles and phthalocyanine blue fine particles, and silicon oxide as a main component. A glass substrate with a transparent two-layer film composed of a transparent coating layer made of a silicate film, that is, a low-transmittance transparent conductive substrate of Sample 2 was produced.
The film characteristics of the transparent two-layer film formed on the glass substrate of Sample 2 were evaluated in the same manner as in Example 1, and the results are also shown in Table 1 below.

[0040]Comparative Example 1 ITO fine particles with an average particle size of 30 nm (SUFP-HX, Sumitomo
Tomo Metal Mining Co., Ltd.) 20.0 g and dispersant 1.5 g
Was mixed with 78.5 g of ethanol (EA), and
Disperse the paint shaker with Konia beads and
An ITO fine particle dispersion liquid (C liquid) having a dispersed particle diameter of 105 nm is obtained.
It was

Further, 20.0 g of particulate carbon bonblack particles having an average particle size of 20 to 30 nm and 1 g of a dispersant were mixed with 79 g of ethanol (EA), and then dispersed with paint shaker together with zirconia beads to obtain dispersed particles. Granular carbon black fine particle dispersion liquid with a diameter of 135 nm (D
Liquid) was obtained.

Next, ethanol and water are further added to the above liquids C and D to form a coating liquid for forming a low transmittance transparent conductive layer (ITO: ITO: 2.0%, carbon: 0.15%,
Water: 7.4%, EA: 90.4%) was prepared.

Using this low-transmittance transparent conductive layer forming coating liquid, in the same manner as in Example 1, a low-transmittance transparent conductive layer containing ITO fine particles and granular carbon black fine particles, and silicon oxide as a main component. A glass substrate with a transparent two-layer film composed of a transparent coating layer made of a silicate film, that is, a low-transmittance transparent conductive substrate of Sample 3 was produced. The film characteristics of the transparent two-layer film formed on the glass substrate of Sample 3 were evaluated in the same manner as in Example 1, and the results are also shown in Table 1 below.

[0044]

[Table 1]

As is clear from the results shown in Table 1,
Compared with the transparent two-layer film of the sample 3 of the comparative example which is the conventional example, the transparent two-layer films of the samples 1 and 2 of the example show that the transmittance value is reduced to about 65% which is almost the same. In addition, the resistance is comparable to 60 to 70 KΩ / □.

Therefore, according to the method of the present invention, expensive IT
It can be seen that a practical low-transmittance transparent conductive film can be obtained at a very low cost without using O fine particles. Also,
Compared with the sample 3 of the comparative example which is a conventional example, in the low transmittance transparent conductive base materials of the samples 1 and 2 in the example of the present invention,
It was confirmed that the reflection characteristics in the visible light wavelength range were equivalent or higher.

Further, an ultraviolet irradiation test was carried out as a weather resistance test for the low-transmissivity transparent conductive base materials of Samples 1 to 2 in the above Examples and Sample 3 which is a Comparative Example. At an ultraviolet irradiation dose of 100 KJ / cm ² , all of the low transmittance transparent conductive substrates of Samples 1 to 3 showed a resistance increase up to twice the initial film resistance value.

Further, with respect to the low-transmissivity transparent conductive substrates of Samples 1 to 3, the film strength was evaluated by a pencil hardness test (load: 1 Kg). Samples 1 to 2 of Examples were 8H, and Sample 3 of Comparative Example. Had a hardness of 7H.

From the results of the weather resistance test and the film strength test, it was confirmed that the transparent two-layer film of the present invention is equivalent or superior to the transparent two-layer film of the comparative example. .

[0050]

According to the present invention, a transparent conductive layer having a low transmittance and a low resistance can be formed at low cost by using a coating liquid for forming a low transmittance transparent conductive layer in which the conductive fine particles are chain carbon fine particles. can do. With this low transmittance transparent conductive layer,
A transparent two-layer film formed of a transparent coat layer formed thereon has excellent conductivity, low resistance, and low reflectance as a flat type front plate used for a display device such as a CRT, and also has a flat surface. Along with this, it is possible to achieve uniform in-plane brightness and improvement in contrast.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01B 1/24 H01J 29/89 5G435 H01J 29/89 H01B 5/14 A // H01B 5/14 G02B 1/10 Z F Term (reference) 2K009 BB02 CC09 CC21 EE01 EE03 4J038 AA011 HA026 HA216 HA316 HA441 JB16 JB27 JB28 KA06 KA08 KA12 KA20 MA07 MA10 NA01 NA19 NA20 PB09 5C032 AA02 FE02 FA02 FC02 FA02 FA02 FA02 FA02 FA02 FA02 FA02 DA01 FA32 DA01 FA32 DA01 FA32 DA01 GG11 GG32 GG33 HH02 HH03 HH12 KK07 LL04 LL06 LL08

Claims (5)

[Claims] 1. A coating liquid for forming a low-transmittance transparent conductive layer, which comprises chain carbon fine particles having a length of 10 to 1000 nm as a main component of conductive fine particles dispersed in a solvent. 2. The coating liquid for forming a transparent conductive layer having a low transmittance according to claim 1, wherein the chain carbon fine particles are Ketjen black fine particles or carbon nanotube fine particles. 3. The coating liquid for forming a low transmittance transparent conductive layer according to claim 1, further comprising colored pigment fine particles. 4. The colored pigment fine particles are titanium black, titanium nitride, complex oxide pigment, cobalt violet, molybdenum orange, ultramarine blue, dark blue, quinacridone pigment, anthraquinone pigment, perylene pigment, isoindolinone pigment, The coating liquid for forming a low transmittance transparent conductive layer according to claim 3, which is at least one kind of fine particles selected from an azo pigment and a phthalocyanine pigment. 5. A front plate for a display device, comprising a transparent two-layer film comprising a low transmittance transparent conductive layer and a transparent coat layer on a transparent substrate, wherein the conductive fine particles contained in the low transmittance transparent conductive layer. Is a chain carbon fine particle having a length of 10 to 1000 nm, and a front plate for a display device.