JP4223487B2 - Black fine particles, black fine particle dispersion, black light shielding film, and substrate with black light shielding film - Google Patents

Description

  The present invention relates to a black fine particle, a black fine particle dispersion, a black light-shielding film, and a substrate with a black light-shielding film, and is particularly suitable for use in a black matrix of a flat display device such as a liquid crystal display. The present invention relates to a black fine particle, a black fine particle dispersion, a black light shielding film, and a substrate with a black light shielding film.

Conventionally, a liquid crystal display (LCD) capable of full color display is known as a thin and large flat display device.
In this color liquid crystal display, the R (red), G (green), and B (blue) pixels arranged in a matrix on a transparent substrate are shielded from light in order to improve the contrast on the display surface. A highly functional black matrix is formed.
In particular, in the active matrix type liquid crystal display (TFT-LCD) using a thin film transistor (TFT), this black matrix prevents a leakage current induced by light from the TFT and transmits light other than the display surface of each pixel. By preventing the transmission and improving the contrast of each pixel, the image quality of the display device can be improved.

This black matrix may be formed on the TFT array substrate side or on the color filter side.
When formed on the TFT array substrate side, the black matrix is in direct contact with the pixel electrode and the TFT, so that the black matrix is required to have high insulation.
On the other hand, when it is formed on the color filter side, particularly in the case of a lateral electric field drive type liquid crystal display (LCD), the black matrix on the color filter side is also required to have high insulation.

In the past, this black matrix was formed with a highly light-shielding metal film such as Cr so as to cover portions other than the transparent pixel electrode by vacuum deposition or sputtering. As an alternative material, a black matrix forming material having a high light shielding property, a simple manufacturing process, and capable of reducing the price has been developed and put into practical use.
As such a material for forming a black matrix, for example, a dispersion liquid in which carbon black or titanium black whose surface is covered with a resin or silicon oxide and insulated is dispersed in an organic solvent (for example, Patent Documents 1 and 2). (See, for example, Patent Documents 3 and 4) in which metal fine particles such as silver fine particles are dispersed in an organic solvent.
JP 2002-201381 A JP 2002-267832 A JP 2004-317897 A JP 2004-334180 A

By the way, when a black matrix is made with a dispersion using conventional carbon black or titanium black, the light shielding property is insufficient, so it is necessary to increase the film thickness by increasing the concentration of the dispersion or overcoating. There is. However, when the film thickness is increased, the overlap between the black matrix and each pixel increases, the flatness of the color filter decreases, and the cell gap of each pixel becomes uneven, which makes it difficult to form uniform pixels. There was a problem.
When the cell gap is uneven, color unevenness is likely to occur on the display surface, and as a result, the quality of the display surface is degraded.
Further, when the overlap between the black matrix and each pixel increases, there is a problem in that the area occupied by the black matrix in each pixel increases and the aperture ratio of each pixel decreases. When the aperture ratio decreases, the luminance of each pixel decreases, and as a result, the luminance of the entire display surface of the display device decreases.

Carbon black and titanium black are surface-treated by a gas phase method or a liquid phase method, but when surface treatment is performed by a gas phase method, it is difficult to disperse particles in the gas phase. The particles are mixed with the substance to be surface-treated in a state where the particles are in contact with each other. Therefore, the uniformity of the surface treatment is poor, and aggregation of the particles becomes a problem. Therefore, there is a method in which the alkoxide such as tetraethoxysilane is vapor-phase adsorbed on the surface of the particles, and then the excess alkoxide is removed under reduced pressure. However, this method is complicated and takes time and cost. There is a problem.
In addition, when the surface treatment is performed by the liquid phase method, the surface treatment can be performed in a state where the particles are dispersed in the liquid phase. For example, since carbon black and titanium black are obtained in a powder state in which particles are aggregated, it is very difficult to disperse them in water or an organic solvent.

On the other hand, when a black matrix is prepared with a dispersion using conventional metal fine particles, there is a problem in that high insulation cannot be obtained with a black matrix in which metal fine particles are simply dispersed.
In particular, in the case of a dispersion using black silver fine particles, since the silver fine particles are synthesized using gelatin, the gelatin cannot be completely removed after the synthesis. Therefore, the silver fine particles are not contained in the organic solvent. Difficult to uniformly disperse. In this case, silver fine particles cannot be synthesized unless gelatin is used.

  The present invention has been made to solve the above-described problems, and is easily dispersed in a solvent, has a high blackness, and has a high insulating property, a black fine particle dispersion, a black fine particle dispersion, and a black light-shielding film. An object of the present invention is to provide a substrate with a black light-shielding film.

  As a result of intensive studies on materials that are easy to disperse in a solvent, have high blackness, and have high insulating properties, the conventional silver fine particles have a mean particle size of silver tin alloy as a main component. By replacing the fine particles of 1 nm or more and 300 nm or less with the fine particles, and coating the surface of the fine particles with an insulating film, black particles that are easy to disperse in a solvent, have high blackness, and have high insulating properties can be obtained. As a result, the present invention has been completed.

That is, the black fine particles of the present invention are characterized in that the surface of fine particles having a silver tin alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is covered with an insulating film.
The insulating film is preferably a metal oxide or an organic polymer compound.
The silver-tin alloy preferably contains 47.6% by weight to 90% by weight of silver.

  The black fine particle dispersion of the present invention contains the black fine particles of the present invention.

  The black light-shielding film of the present invention is formed by applying the black fine particle dispersion of the present invention.

  The base material with a black light-shielding film of the present invention is characterized in that the black light-shielding film of the present invention is provided on one main surface of the base material.

  According to the black fine particles of the present invention, since the surface of fine particles having a silver tin alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is covered with an insulating film, it can be easily dispersed in a solvent. Further, the blackness of the black fine particles themselves can be improved, and the insulation can be improved.

  According to the black fine particle dispersion of the present invention, since the black fine particles of the present invention are contained, the dispersibility of the black fine particles can be improved, and the coating property can be improved.

Since the black light-shielding film of the present invention is obtained by applying the black fine particle dispersion of the present invention, the light-shielding property and the insulating property can be improved even when the film thickness is thin.
If this black light-shielding film is applied to the black matrix of a flat display device such as a liquid crystal display, the overlap between the black matrix and each pixel can be reduced by reducing the film thickness, and the unevenness of the cell gap of each pixel can be reduced. Can be reduced, and the pixels can be made uniform. Therefore, color unevenness hardly occurs on the display surface, and the quality of the display surface can be improved. In addition, the aperture ratio of each pixel can be improved, and the luminance of the entire display surface of the display device can be improved.

The best mode of the black fine particles, the black fine particle dispersion, the black light shielding film, and the substrate with the black light shielding film of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

In the black fine particles of the present embodiment, the surface of fine particles having a silver tin (AgSn) alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is covered with an insulating film.
The fine particles may be composed of an AgSn alloy as a main component, and may contain, for example, Ni, Pd, Au, etc. as other metal components.
The fine particles may be a mixture of Ag fine particles and Sn fine particles in addition to AgSn alloy fine particles.
When this AgSn alloy is represented by the chemical formula Ag _x Sn, the range of x in which a chemically stable AgSn alloy can be obtained is 1 ≦ x ≦ 10, and chemical stability and blackness can be obtained simultaneously. The range is 3 ≦ x ≦ 4.

Here, when the weight ratio of Ag in the AgSn alloy is determined within the range of x,
When x = 1, Ag / AgSn = 0.4762
When x = 3, 3 · Ag / Ag ₃ Sn = 0.7317
When x = 4, 4 · Ag / Ag ₄ Sn = 0.7843
When x = 10, 10 · Ag / Ag ₁₀ Sn = 0.008
It becomes. Therefore, this AgSn alloy becomes chemically stable when Ag is contained in an amount of 47.6 wt% or more and 90 wt% or less, and when Ag is contained in an amount of 73.17 wt% or more and 78.43 wt% or less. In addition, chemical stability and blackness can be effectively obtained with respect to the Ag amount.

  The fine particles which are constituent elements of the black fine particles can be produced by using a normal fine particle synthesis method. As the fine particle synthesis method, any method such as a gas phase reaction method, a spray pyrolysis method, an atomization method, a liquid phase reaction method, a freeze-drying method, or a hydrothermal synthesis method may be used.

The insulating film is a highly insulating fine particle obtained by insulating the surface of a fine particle having an AgSn alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less, and a metal oxide or an organic polymer compound is preferable. .
As the metal oxide, an insulating metal oxide such as silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), yttrium oxide (yttria), titanium oxide (titania), etc. is preferably used. It is done.
In addition, as the organic polymer compound, an insulating resin such as polyimide, polyether, polyacrylate, polyamine compound, or the like is preferably used.

The thickness of the insulating film is preferably 1 to 100 nm, more preferably 5 to 50 nm, in order to sufficiently maintain the insulating properties of the surface of the fine particles.
This insulating film can be easily formed by a surface modification technique or a surface coating technique. In particular, use of an alkoxide such as tetraethoxysilane or aluminum triethoxide is preferable because an insulating film having a uniform thickness can be formed at a relatively low temperature.

In the black fine particles of this embodiment, the surface of fine particles having an AgSn alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is coated with an insulating film, so that the blackness is higher than that of Ag particles or Sn particles. The light shielding property is improved and the insulating property is also improved.
In addition, the surface of fine particles having an AgSn alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is covered with an insulating film made of a metal oxide, so that the heat resistance is higher than that of metal particles such as Ag particles and Sn particles. In addition, it has excellent mechanical strength and is difficult to wear.

The black fine particle dispersion of the present embodiment contains the black fine particles of the present embodiment, and the black fine particle dispersion is particularly limited as a solvent and a solvent containing an organic binder or the like as necessary. Although not, for example, monohydric alcohols such as water, methanol, ethanol, n-propanol, 2-propanol, butanol, dihydric alcohols such as ethylene glycol, β-oxyethyl methyl ether (methyl cellosolve), Ethylene glycol ethers (cellosolves) such as β-oxyethyl ether (ethyl cellosolve), β-oxyethylpropyl ether (propyl cellosolve), butyl-β-oxyethyl ether (butyl cellosolve), glycols such as ethylene glycol and propylene glycol , Acetone, methyl ethyl Tons, ketones such as diethyl ketone, ethyl acetate, butyl acetate, esters such as benzyl acetate, ether alcohols such as methoxyethanol, ethoxyethanol, and propylene glycol monomethyl ether acetate.

  The black fine particle dispersion of the present embodiment contains black fine particles in which the surface of fine particles having an AgSn alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is covered with an insulating film, so that the degree of blackness is high and the light shielding property. In addition, it is possible to provide a black fine particle dispersion that is an excellent material for insulating black and has a low cost as a raw material for a black light-shielding film.

The black light-shielding film of this embodiment is obtained by applying the black fine particle dispersion of this embodiment on a substrate and then drying.
If this black light-shielding film is formed on one main surface of the substrate, a substrate with a black light-shielding film is obtained.
Although it does not specifically limit as a base material, A glass base material and a plastic base material (organic polymer base material) can be mentioned. Moreover, as the shape, a flat plate, a film form, a sheet form, etc. are mentioned. Moreover, as said plastic base material, a plastic sheet, a plastic film, etc. are suitable.

The material of the glass substrate is not particularly limited, and can be appropriately selected from soda glass, potash glass, non-alkali glass, and the like.
The material of the plastic substrate is not particularly limited. For example, cellulose acetate, polystyrene (PS), polyethylene terephthalate (PET), polyether, polyimide, epoxy, phenoxy, polycarbonate (PC), polyvinylidene fluoride , Triacetyl cellulose, polyethersulfone (PES), polyacrylate, and the like.

  As a coating method, a commonly used method such as a spin coating method, a spray coating method, an ink jet method, a dipping method, a roll coating method, a screen printing method, a bar coating method, or the like is preferably used.

Since the dispersion applied on the substrate contains a solvent, the solvent is removed by a subsequent drying step.
For example, the substrate coated with the dispersion liquid is allowed to stand at room temperature (25 ° C.) in the atmosphere or heated at a predetermined temperature, for example, 50 ° C. to 80 ° C. in the atmosphere. The solvent contained in the liquid is dissipated to form a black light shielding film.

When used as a black matrix for a display device such as a liquid crystal display (LCD), the black light-shielding film preferably has a high insulating property. For example, the volume resistance (Ω · cm) is preferably 10 ⁷ Ω · cm or more. It is a range.
Further, CIE lightness L ^* standardized by CIE (International Lighting Commission) is 10 or less, chromaticity a ^* is −1 or more and 1 or less, chromaticity b ^* is −1 or more and 1 or less, and optical density. The OD value is preferably 3 or more.
The lower the CIE lightness L ^* , the better the blackness. In particular, when the CIE lightness L ^* is used as a black matrix of a display device such as a liquid crystal display (LCD), the lower the CIE brightness L ^* , the better the display contrast. Therefore, a preferable range is 10 or less, which is a range where the display contrast is good.

The chromaticities a ^* and b ^* are preferably achromatic from the viewpoint of display quality, and when the absolute value exceeds 1, the hue takes on a hue. Therefore, the absolute value of an achromatic color within a preferable range is 1 or less, that is, −1 Above and below 1.
If the OD value is low, sufficient light shielding properties cannot be obtained, and in order to obtain sufficient light shielding properties with a film having a low OD value, the film thickness must be increased. In particular, a liquid crystal display (LCD), etc. When used as a black matrix, display unevenness and the like are likely to occur due to an increase in film thickness. Therefore, even when the film thickness is thin, the range in which sufficient light shielding properties can be obtained is set to 3 or more.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-2 and Comparative Examples 1-3, this invention is not limited by these Examples.

"Preparation of black fine particles"
Black fine particles were prepared as follows.
(1) Silica coated AgSn alloy spherical fine particles A
To a solution obtained by diluting 100 g of an aqueous dispersion of black AgSn alloy spherical particles having an average particle diameter of 10 to 30 nm (solid content: 15 wt%, manufactured by Sumitomo Osaka Cement Co., Ltd.) 10 times with pure water, 1200 g of an aqueous solution containing 0.1% by weight of mercaptopropyltrimethoxysilane (MPS) was added and stirred to give solution A.

On the other hand, 150 g of a solution obtained by diluting water glass with water (3% in terms of SiO ₂ ) was adjusted to 10.5 using a cation exchange resin to obtain a solution B.
Next, the pH of the solution A was adjusted to 9.5 with an aqueous NaOH solution (0.1N), and the solution B was slowly added dropwise to the solution A and stirred for 1 hour. Subsequently, unreacted water glass, MPS, ions, and the like were removed from this solution using ultrafiltration, and then concentrated to obtain a dispersion.
Next, the solution and the fine particles were separated from this dispersion by centrifugation, freeze drying, and the like, and dried to obtain silica-coated AgSn alloy spherical fine particles A.

(2) Silica coated AgSn alloy spherical fine particles B
Acetic acid (0.1N) was added to said A liquid, and pH was adjusted to 4.8. Next, 300 g of an aqueous solution containing 1% by weight of tetraethoxysilane was dropped into this solution, and then heated to 60 ° C. and stirred at this temperature for 2 hours. Subsequently, unreacted MPS, tetraethoxysilane, and acetic acid were removed from this solution using ultrafiltration, and then concentrated to obtain a dispersion.
Next, the solution and fine particles were separated from this dispersion by centrifugation, freeze drying, and the like, and dried to obtain silica-coated AgSn alloy spherical fine particles B.

"Preparation of black fine particle dispersion and black light shielding film"
(Example 1)
To 100 g of silica-coated AgSn alloy spherical fine particles A, 2 g of a dispersant (Solsperse 20000: manufactured by Avicia Co., Ltd.) and 100 g of propylene glycol monomethyl ether acetate were added and dispersed using a bead mill to obtain a silica-coated AgSn alloy aggregated particle dispersion. To this dispersion, 50 g of a binder consisting of 64 parts by weight of benzyl methacrylate / methacrylic acid copolymer, 26 parts by weight of dipentaerythritol hexaacrylate, and 907: 9 parts by weight of Irgacure 907 was added and mixed to obtain a coating solution. This coating solution was applied onto a glass substrate by a spin coater, dried at room temperature (25 ° C.), and then irradiated with ultraviolet rays (UV) to form a black film having a thickness of 0.6 μm.

(Example 2)
In Example 1, the black film of Example 2 was formed in the same manner as in Example 1 except that the silica-coated AgSn alloy spherical fine particles B were used in place of the silica-coated AgSn alloy spherical fine particles A.

(Comparative Example 1)
A black film was formed in the same manner as in Example 1 except that AgSn alloy spherical particles not coated with silica were used.

(Comparative Example 2)
A black film was formed in the same manner as in Example 1 except that silica-coated carbon black was used.

(Comparative Example 3)
A black film was formed in the same manner as in Example 1 except that silica-coated titanium black was used.

"Evaluation of black film"
The volume resistance of each black film of Examples 1-2 and Comparative Examples 1-3 was measured. The measurement was performed by a four-terminal method in accordance with Japanese Industrial Standard JIS C 2103-1991 “Volume Resistivity Test”.
The OD value, which is the optical density of the black film, was measured using a transmission densitometer.
In order to evaluate the blackness of the black film, the CIE lightness L ^* and chromaticity a ^* and b ^* of the black film are L ^* a ^* b ^* standardized by the CIE (International Commission on Illumination) ^. Measurement was based on the color system. These measurement results are shown in Table 1.

According to this table, the black film of Examples 1 and 2 is greater than the volume resistivity is ^{10 10} [Omega] cm, and the OD value is 4 or more, CIE lightness ^{L *} is low, the chromaticity ^a *, ^{b *} of the absolute value Therefore, it was confirmed that the insulating property, the light shielding property and the blackness were excellent.
On the other hand, the black film of Comparative Example 1 has an OD value of 4 or more, a low CIE lightness L ^* , and a small absolute value of chromaticity a ^* and b ^* , but a volume resistance of 4.1 × 10 ⁶ Ωcm. It was found that the insulation property was low.
The black films of Comparative Examples 2 and 3 have a volume resistance greater than 10 ¹⁰ Ωcm and a low CIE lightness L ^*, but have an OD value as small as about 2 and an absolute value of chromaticity a ^* and b ^* of 1. It was found that both the blackness and the light shielding property were inferior to the black films of Examples 1 and 2.

  The black fine particles of the present invention are excellent in blackness, light-shielding properties, and insulating properties, and can be used as inexpensive black light-shielding film materials. Therefore, the black fine particles can be used for any material that requires blackness, light-shielding properties, and insulating properties. Applicable. For example, black matrix material, black seal material, black mask material, etc. for display devices such as liquid crystal display (LCD), plasma display (PDP), electroluminescence display (ELD), electrochromic display (ECD), etc. It can also be used as a conductive film, black light-shielding glass, black paper, black cloth, black ink and the like.

Claims (6)

  A black fine particle characterized in that the surface of fine particles having a silver tin alloy as a main component and an average particle diameter of 1 nm or more and 300 nm or less is coated with an insulating film.   The black fine particles according to claim 1, wherein the insulating film is a metal oxide or an organic polymer compound.   3. The black fine particles according to claim 1, wherein the silver tin alloy contains 47.6 wt% or more and 90 wt% or less of silver.   A black fine particle dispersion comprising the black fine particles according to claim 1, 2 or 3.   A black light-shielding film obtained by coating the black fine particle dispersion according to claim 4.   A base material with a black light-shielding film, comprising the black light-shielding film according to claim 5 on one main surface of the base material.