JP3192745B2 - Light absorbing material for liquid crystal display, light shielding film and liquid crystal display panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light absorbing material and a light shielding film for a liquid crystal display, and a liquid crystal display panel using the same.

[0002]

2. Description of the Related Art In a liquid crystal display (hereinafter abbreviated as LCD) as a device requiring a light-shielding film, in a color display LCD, for example, a black matrix of a color filter or a transistor (TFT) light-shielding film in an active matrix driving system is used. Yes, and negative display type LC
In D, there are a black mask for blacking the background other than the display unit, a black seal for sealing the liquid crystal, and the like.
Devices other than LCDs include an electric field limiting layer in an EL display and a light shielding film in an optical device.

Conventionally, as these materials, inorganic pigments such as carbon black and titanium black, vapor-deposited or sputtered films of metallic chromium, and organic pigments have been mainly used.

[0004]

By the way, high light absorption characteristics (light shielding properties) are naturally required for the light absorbing material of the LCD and the light shielding material for forming the light shielding film. Also, LC
In order to manufacture display devices such as D, high insulation and heat resistance are required, and further, light resistance and stability are required in terms of life. Here, the reason why high heat resistance is required is that a process for providing an alignment film that requires a high-temperature treatment after forming the light-shielding film is included.

However, the metal chromium film has a problem that the process of manufacturing the LCD is complicated because an insulating layer needs to be overcoated on the chromium film due to its metal conductivity. In addition, there is a problem that the production cost is increased because of the film formation, and furthermore, although the light shielding property is good, the metal reflection characteristic of the metal is large, and the screen becomes like a mirror, and the screen becomes hard to see. There's a problem. In addition, there is a problem that the production cost is further increased because the treatment involves a harmful substance called chromium.

In addition, the above-mentioned carbon black and titanium black tend to cause agglomeration and tend to form pinholes, cause bleed-out, and have the same conductivity as metal chromium. There is a problem that the light-shielding property is insufficient. In addition, the above-mentioned organic pigments do not have sufficient light-shielding properties and cause a decrease in contrast of the display, and furthermore, there is an inconvenience that the production process is inferior in heat resistance, and in particular, the alignment film formation process requiring heating is limited. Due to poor light resistance, there is a problem that reliability is insufficient when used for a long time.

As described above, in the conventional materials, the light absorption characteristics,
There is nothing that satisfies all requirements such as insulation, heat resistance, light resistance, stability, etc., so the manufacturing process is complicated, the heating process is limited, the cost is high, and the panel life is long At present, it is necessary to tolerate lack of reliability.

The present invention has been made in view of the above circumstances, and provides a light absorbing material and a light-shielding film for a liquid crystal display, which are excellent in various performances and are also advantageous for LCD production, and a liquid crystal display panel using the same. The purpose is to do.

[0009]

In order to achieve the above object, the present inventor has conceived of forming a film by a printing method and a coating method which are suitable for low-cost production. Focusing on inorganic materials that are considered to be excellent in light resistance, as a result of examining all inorganic pigments,
Bismuth sulfide (Bi ₂ S ₃ ) is excellent in visible light absorption characteristics (light shielding properties), heat resistance and light resistance, and has a surface resistance of 10 ¹³ Ω / cm ² or more in conductivity. The present inventors have found that the electrical insulation is superior by at least seven orders of magnitude as compared with titanium black and metallic chromium, and completed the present invention.

That is, in the light-absorbing material for a liquid crystal display according to claim 1 of the present invention, the pigment is used in an amount of from 0.1 to
Using 0.5μm bismuth sulfide fine particles, epoxy this
Resin, silicone-modified epoxy resin, silicone resin
In at least one binder selected from
Dispersing and forming a paint is a means for solving the above problem. Further, in the liquid crystal display panel according to the second aspect of the present invention, the light-absorbing material for a liquid crystal display is used as a means for solving the problem. The light-shielding film according to claim 3, wherein fine particles of bismuth sulfide having a particle size of 0.1 to 0.5 µm are used as the black material, and the black material is an epoxy resin or a silicon-based resin.
In a binder consisting of at least one selected from
It was formed as a solution to the above-mentioned problem by being formed by scattering and forming a paint . Further, in the light shielding film according to claim 4,
Is a sputtering target made of bismuth sulfide
The use of a material to solve the above problem
Was. Characteristic light-shielding film. According to a fifth aspect of the present invention, there is provided a liquid crystal display panel using the light-shielding film according to the third or fourth aspect .

Hereinafter, the present invention will be described in detail. The light-absorbing material for a liquid crystal display according to the first aspect of the present invention is characterized in that 0.1 to 0.5 μm bismuth sulfide powder is used as a filler, which is dispersed in a resin such as an epoxy resin, a silicone-modified epoxy resin, or a silicone resin. It is made into paint. Further, the light shielding film according to claim 4 is formed by CVD.
The light-shielding film according to claim 3 is a bismuth sulfide film produced by a vapor phase film forming method such as a vapor deposition method, a sputtering method, or the like .
0.1-0.5 μm bismuth sulfide powder as filler,
This is a small amount selected from epoxy resin and silicone resin.
It is a film obtained by dispersing in at least one kind of binder to form a coating and forming a film.

Here, the method for synthesizing bismuth sulfide (Bi ₂ S ₃ ) powder used in the present invention is as follows: (1) Bismuth chloride is heated in dry hydrogen sulfide. (2) Pass hydrogen sulfide through the hydrochloric acid solution of bismuth chloride. (3) Heat the neutral solution of bismuth nitrate with sodium thiosulfate. Any method such as (2),
According to the method (3), a fine powder can be synthesized, which is preferable.

Further, when preparing a bismuth sulfide coating material, a surfactant, a silane coupling agent, a titanium coupling agent, or the like may be used, if necessary, to improve the dispersion stability of the bismuth sulfide powder in various resins. Additives such as silica sol, alumina sol and zirconia sol may be added.
In the case of a printing paint, ultrafine silica powder, ultrafine titania powder, ultrafine zirconia powder, and fine barium sulfate powder may be added in order to improve printability. Here, specific examples of the binder (resin) of the coating material to be the light-absorbing material for a liquid crystal display according to claim 1 include Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Ltd.) and DEN3
Bisphenol A such as 31 (manufactured by Dow Chemical Co., Ltd.)
Those mainly composed of a mold epoxy resin are preferable. In order to increase the heat resistance of such a binder,
For example, a phenol novolak type epoxy resin such as DEN431 (manufactured by Dow Chemical Co., Ltd.) may be added.

The amine-based curing agent used in the epoxy resin is not particularly limited, but it is preferable to use an aromatic amine. In order to control the fluidity during curing of the paint, for example, Aerosil # 150, # 20
0, # 300, # 380 (manufactured by Nippon Aerosil Co., Ltd.)
Or an organic gelling agent such as Gelol D (manufactured by Shin Nippon Rika Co., Ltd.).

According to a second aspect of the present invention, in the liquid crystal display panel, the light absorbing material (paint) for the liquid crystal display is applied to a panel member such as a glass plate by a printing method such as offset printing, and a black matrix or a black mask is formed. , A black seal or the like. According to a fifth aspect of the present invention, in the liquid crystal display panel, the light-shielding film using the bismuth sulfide according to the third or fourth aspect is formed by an ordinary thin film forming method, for example, CV.
D method, vapor deposition method, vapor phase method such as sputtering method, or coating obtained by dispersing bismuth sulfide powder by roll coating, spin coating, bar coating, offset printing screen printing, etc. A pattern is formed from the obtained light shielding film by a photolithography technique, and is obtained by forming a black matrix, a black mask, a black seal, a TFT light shielding film, and the like.

Here, the same paint as that used for the light-shielding film according to claim 3 can be used as the paint used when forming by the coating method. Particularly, for the LCD panel, a UV curable resin or a thermosetting resin is used. Among them, it is particularly preferable to use an epoxy resin or a silicone resin as a binder from the viewpoints of workability, heat resistance, and long-term reliability. Although the solvent to be used varies depending on the film forming method, it is preferable to use a combination of a high-boiling point solvent and a low-boiling point solvent in order to maintain the smoothness of the coating film surface, and to adjust the drying rate and the viscosity.

The content of bismuth sulfide which should exert light-shielding performance varies depending on the target portion in the LCD panel. For example, when a black matrix having a thickness of 1.2 μm is formed, the content of bismuth sulfide in the film is reduced. If the amount is 40 to 50% by weight, the OD value (opti
The light shielding property of about 3 to 3.5 can be achieved with a cal density of about 3 to 3.5, and the same light shielding performance as that of metallic chrome can be achieved. Further, when a black mask having a thickness of 2 μm is formed, the content of bismuth sulfide in the film is reduced to 2 μm.
By setting the amount to 0 to 30% by weight, a light-shielding property with an OD value of about 3 can be achieved. Further, when a black seal having a thickness of 6 μm is formed, by setting the bismuth sulfide content in the film to 5 to 10% by weight, a light-shielding property with an OD value of about 3 can be achieved. Thus, the amount of bismuth sulfide in the paint is determined by the desired film thickness and light shielding performance.

Regarding the electrical insulation of the light-shielding film of the LCD panel obtained in this way, the surface resistance of each of them has a value of 10 ¹³ Ω / cm ² or more, and the insulation is almost the same as that of the liquid crystal. It has performance. As for the heat resistance, no change such as discoloration, peeling of the film and deterioration of the insulating property occurs up to 300 ° C. However, when the heating is performed at 350 ° C. or more, the light-shielding film gradually whitens or peels off.
It is 280 ° C, and there is no problem in processing as long as it has sufficient heat resistance at 300 ° C.

[0019]

The present invention will be described below in more detail with reference to examples. Example 1 First, bismuth nitrate (Bi (NO ₃ ) ₃ .5)
H ₂ O) and 194 g of sodium hydroxide in water 20
Dissolve in 00 cc. Also, sodium thiosulfate (Na
The _{2 S 2 O 3 · 5H 2} O) 164g dissolved in water 1500cc. Then, the latter solution is added to the former solution, and the mixture is heated at 95 ° C. for 20 hours with stirring, filtered, desalted and washed by a usual method, and further dried at 150 ° C. to 0.1 to 0.1 ° C.
Bismuth sulfide fine particles of 0.5 μm were obtained.

Here, bismuth sulfide (Bi ₂ S ₃ ) is produced by the following reaction. 2Bi (NO ₃ ) ₃ + 3Na ₂ S ₂ O ₃ + 3H ₂ O → Bi ₂ S ₃ + 6NaNO ₃ + 3H ₂ SO _{4 The} obtained bismuth sulfide fine particles were black, and the residual sodium content was 0.1 ppm or less. .

Next, using a titanate-based coupling agent (Plenact KR-55 [manufactured by Ajinomoto Co., Inc.]),
A surface treatment was performed on the obtained bismuth sulfide fine powder. Next, 25 g of the bismuth sulfide powder after the surface treatment and methylphenyl silicon varnish (silicone resin TSR14
5 (manufactured by Toshiba Silicone Co., Ltd.)), 32 g of silicon-modified epoxy resin (silicon resin TSR194 (manufactured by Toshiba Silicone Co., Ltd.)), and ultrafine silica powder (Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.) for improving fluidity ]) And 8 g were pre-mixed, and then kneaded with a three-roll mill for 3 hours to produce a black light-absorbing material.

For comparison, an organic pigment (aniline black) was used in place of the bismuth sulfide powder after the surface treatment, and a light-absorbing material was produced using the same other ingredients. Next, these two types of light-absorbing materials were used, each of which was printed on a glass plate at a thickness of 2 μm by an offset printing machine, and further heated at 150 ° C. for 2 hours to be cured, thereby forming two types of light-absorbing films. Produced.

The thickness of the light absorbing film thus manufactured,
The light transmittance (light shielding property) at 550 nm, the withstand voltage, the heat resistance, and the light resistance were examined, and the obtained results are shown in Table 1. In addition, here, about heat resistance, it heats at 260 degreeC for 2 hours,
The color difference before and after that was examined. For light resistance, see JI
Light was irradiated for 100 hours according to SK5400, and the color difference before and after the irradiation was examined.

[Table 1] From the results shown in Table 1, the product of the example of the present invention has the same light-shielding properties, insulation properties and heat resistance as compared with the conventional organic light-absorbing material as the comparative product, but has the same light resistance. It is remarkably excellent.

Example 2 A liquid crystal display cell shown in FIG. 1 was manufactured as the liquid crystal display panel according to the second aspect of the present invention. First, an alkali-free glass plate 1 having a thickness of 1.1 μm shown in FIG. 1 is prepared, and the light-absorbing material is manufactured by offset printing using the light-absorbing material (product of the embodiment) manufactured in Example 1. A desired pattern was printed on the plate 1 at a thickness of 1 μm, and further heated and cured at 150 ° C. for 2 hours to produce a black mask 2. next,
An ITO transparent electrode layer was formed on the black mask 2 by vapor deposition at 260 ° C., and was further etched to form an electrode pattern, thereby forming an ITO transparent electrode 3 ′.

Next, a 6 μm glass spacer was added to and mixed with the light-absorbing material prepared in Example 1 (Example product).
The obtained mixture is printed in a desired pattern on a glass plate 1 with a black mask 2 by screen printing to form black seal films 4 and 4, and a glass plate 6 on which an ITO transparent electrode 5 is formed is pasted thereon. 150 ℃
And cured for 1 hour to form a liquid crystal cell with a black seal film. Thereafter, a liquid crystal 7 was injected into the liquid crystal cell, and the injection port was sealed to produce a negative display type liquid crystal display cell 8. When the negative display type liquid crystal display cell 8 and the light 9 were energized, no bleeding of the boundary between the seal portion and the liquid crystal, that is, the seal film at the periphery of the display was observed, and the contrast of white-black display was extremely good. there were.

Example 3 Bismuth sulfide fine particles of 0.1 to 0.5 μm were obtained in the same manner as in Example 1. next,
This powder was pressed and molded at 100 kg / cm ² and heat-treated at 400 ° C. for 2 hours in a vacuum to prepare a sputtering target material. The obtained bismuth sulfide target material was set in a sputtering apparatus (SPS210 type, manufactured by JEOL Nerva Corporation), and a thickness of 0.6 was placed on a glass plate.
A μm bismuth sulfide light-shielding film was produced. For comparison, a light-shielding film made of metal chromium having a thickness of 0.3 μm was prepared by the same method.

Example 4 A titanate-based coupling agent (preneact KR-46B) was added to 0.1 to 0.5 μm bismuth sulfide fine particles obtained by the same method as in Example 1.
[Manufactured by Ajinomoto Co., Ltd.]] to give a filler for paint. Then, 12 g of the filler for paint and a silicone resin (Campecera # 402-
SC [manufactured by Kansai Paint Co., Ltd.]), 31.2 g of silica sol (NBA-ST [manufactured by Nissan Chemical Co., Ltd.]) as a dispersion powder, and 5 g of ethyl alcohol as a solvent.
And 31 g of 2-butanol were added and mixed and dispersed in a sand mill for 3 hours to prepare a bismuth sulfide paint. Then
This was applied to a glass plate by a spin coater, and 18
Heat cured at 0 ° C for 1 hour, thickness 1.1μm and 1.6μm
Bismuth sulfide light-shielding film was prepared.

(Example 5) 25 g of the paint filler obtained in Example 4 and an epoxy resin (Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Ltd.)) 40 as a binder
g, 27 g of an aluminum-based curing agent (Epicure Z (manufactured by Yuka Shell Epoxy Co., Ltd.)) and 8 g of ultrafine silica powder (Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.)) for improving fluidity, and then premixed 3 roll mill
The mixture was mixed for time to prepare a bismuth sulfide coating for printing. Next, the bismuth sulfide paint was printed on a glass plate by an offset printing machine, and then cured by heating at 150 ° C. for 2 hours to produce a light-shielding film having a thickness of 2 μm. For comparison, a light-shielding film was prepared using carbon black, titanium black, and aniline black in place of bismuth sulfide powder and using the same other ingredients.

The light-shielding films thus obtained in Examples 3 to 5 had a thickness of 550 mm, an OD value (light-shielding property), a light reflectance (reflection degree), a surface resistance (insulating property),
The heat resistance and the light resistance were examined, and the results obtained are shown in Table 2. Here, the OD value is obtained from the following equation by measuring the light transmittance (T%). OD = -log (T / 100) The heat resistance was obtained by examining the properties of the film after heating at 280 ° C. for 2 hours, and the light resistance was determined by JIS.
The properties of the film after light irradiation for 100 hours according to K5400 were examined.

[Table 2] Based on the results shown in Table 2, claims 3 and 4 of the present invention were obtained.
In addition, it was confirmed that the products of Examples of Claim 4 were all excellent in light-shielding properties, insulation, heat resistance, and light resistance as compared with the conventional light-shielding film using a black material as a comparative example.

(Embodiment 6) The bismuth sulfide paint shown in Embodiment 4 was used as the LCD panel according to the fifth aspect of the present invention, and bismuth sulfide was used as a light-shielding film (black matrix) in the steps shown in FIGS. A color filter was prepared, and incorporated into an active matrix driving type LCD element to prepare an LCD panel. Here, the process shown in FIG. 2 will be described.
First, the bismuth sulfide paint is applied to the glass substrate 10 to form a light-shielding film 11 ((b) in FIG. 2), and a resist 12 is further applied thereon ((c) in FIG. 2), and a photomask is applied. [(D) in FIG. 2], and etched with a 5% -HNO3 solution to form a black matrix pattern 13.
[(E) in FIG. 2].

Next, a coloring material 14 is applied on the glass substrate 10 on which the pattern 13 is formed, and a positive resist is further applied thereon, exposed with a photomask, developed, and etched [FIG. (F)]. Then, this step (the step shown in FIG. 3 (f)) is repeated to form a colored layer 15 # of a desired color, and then a protective film 16 is formed to form a color filter. The resulting display panel is made of a conventional metal chrome with a light-shielding film (black matrix).
As compared with a panel incorporating a color filter, the color LCD was low in reflection and therefore did not show any image, and had very good visibility.

[0032]

As described above, the light absorbing material for a liquid crystal display according to the first aspect of the present invention uses bismuth sulfide as a pigment to provide heat resistance, insulating properties, and the like.
It is excellent in stability and the like. In the liquid crystal display panel according to the second aspect of the present invention, the light absorbing material is used, for example, by using the light absorbing material for a black mask or a black seal, so that the seal film bleeds around the display such as a seal portion or a liquid crystal boundary. Are prevented, and the contrast of white-black display becomes extremely good. The light-shielding film according to claim 3 or 4 has excellent light-shielding properties, insulation properties, heat resistance, light resistance, and the like by using bismuth sulfide as the black material. Since the liquid crystal display panel according to claim 5 uses the light-shielding film, for example, by using the light-shielding film for a black matrix, a TFT light-shielding film, a black mask or a black seal, the reflection is reduced and the visibility is improved. ,
Moreover, bleeding of the seal film at the periphery of the display, such as the seal portion and the liquid crystal boundary, is prevented.
The contrast of the black display is also very good.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a liquid crystal display panel according to claim 2 of the present invention, and is a side view showing a schematic configuration of a negative display type liquid crystal display cell.

FIG. 2 is a process diagram for explaining a method for producing a color filter as one embodiment of the liquid crystal display panel according to claim 5 of the present invention, and is a diagram showing a black matrix producing process.

FIG. 3 is a process diagram for explaining a method of manufacturing a color filter as one embodiment of the liquid crystal display panel according to claim 5 of the present invention, and is a diagram illustrating a color filter forming process.

[Explanation of symbols]

 2 Black mask 4 Black seal film 8 Negative display type liquid crystal display cell 10 Glass substrate 11 Light shielding film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1335 G02F 1/13 101 G02B 5/20

Claims (5)

(57) [Claims] 1. Bismuth sulfide fine particles having a particle size of 0.1 to 0.5 μm are used as a pigment ,
Small number of resins selected from modified epoxy resin and silicone resin
Disperse in at least one kind of binder to make paint
A light-absorbing material for a liquid crystal display, characterized in that: 2. The light for a liquid crystal display according to claim 1.
Liquid crystal display characterized by using an absorbing material
Ipanel. 3. Black bismuth sulfate fine particles of 0.1 to 0.5 μm are used as a black material ,
Binder composed of at least one selected from binder resins
A light-shielding film formed by dispersing into a paint to form a coating ; 4. A sputtering method comprising bismuth sulfide.
A shield formed using a target material.
Light film. 5. The light-shielding film according to claim 3 or 4.
Liquid crystal display panel characterized by using
Le.