JPH05289336A - Composition for forming light shielding thin film - Google Patents

Abstract

PURPOSE:To provide a composition for forming thin film having high light shielding property by blending a specific ratio of bismuth sulfide to a negative resist. CONSTITUTION:The objective composition is obtained by blending 70-20 pts.wt. bismuth sulfide to 30-80 pts.wt. negative resist. So-called ultraviolet-curing resist hardened by light of ultraviolet region is preferably used because of its easy application. The negative resist mainly contains various synthetic resins such as acrylic base, urethane base, epoxy base, synthetic rubber base, polyvinyl alcohol and natural rubber or gelatin or the like and is formed singly or by blending each of these material. In this case, the powder of bismuth sulfide is, if necessary, surface treated by a silane coupling agent or a titania based coupling agent to improve the dispersibility of the powder of bismuth sulfide into the negative resist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-shielding thin film for forming a light-shielding thin film on a transparent substrate or on a gap between fine light-shielding thin film patterns of a transparent substrate having a fine light-shielding thin film pattern. Forming composition.

[0002]

2. Description of the Related Art In a color filter used for colorizing a liquid crystal display, a light-shielding thin film is formed in the stripe gap in order to shield unnecessary light and improve other characteristics. As a method useful for forming such a light-shielding thin film, there is a backside exposure method as disclosed in, for example, JP-A-62-247331. In this back exposure method, a thin film having a light-shielding property and a function (for example, a function as a color filter) is formed on a transparent substrate in advance, and the thin film is used to coat the photocurable composition. This is a method in which the reaction of a thin film made of a substance with light is blocked, while the light-shielding thin film is formed by a curing reaction by light in other portions, that is, in the gaps between the thin films.

By the way, examples of the light-curing light-shielding thin film forming composition used in such a backside exposure method include metal oxide black pigments such as titanium black, black iron oxide and chromium oxide, and carbon black. Alternatively, it is known that a black dye and a mixture of three color pigments of red, blue, and green are dispersed alone or in a mixture in a negative resist.

[0004]

However, when carbon black, titanium black, black iron oxide or the like is used in the light-shielding thin film forming composition, there are the following disadvantages. Carbon black, titanium black,
Black iron oxide and the like have low electric resistance, and therefore, when these are used, the electric resistance of the light-shielding thin film obtained is also low. Therefore, for example, when a fine conductive circuit pattern is formed on this thin film, the fine conductive An unfavorable phenomenon such as a short circuit between the sexual circuit patterns occurs.

Further, when a chromium oxide pigment is used, expensive treatment equipment is required in order to prevent environmental pollution due to outflow of harmful chromium ions. Also,
When red, blue, and green pigments are mixed and used, it is very difficult to make the resulting light-shielding thin film truly black, and each pigment absorbs only a specific wavelength range. The concentration of the pigment when dispersed in the composition must be higher than that of the case of a single black component, and as a result, the photocurability of the composition is significantly reduced.

Further, when a black dye is used, the heat resistance of the light-shielding thin film obtained due to its low heat resistance is lowered, and when the heat treatment is carried out at, for example, 230 ° C. or higher, its light-shielding property becomes remarkable. descend. The present invention has been made in view of the above circumstances, and an object thereof is to provide a high light-shielding thin film forming composition in order to solve the above-mentioned conventional problems.

[0007]

In order to achieve the above-mentioned object, the present inventor has researched such conventional techniques that the properties of the light-shielding thin film obtained by the back exposure method are determined by the light-shielding pigment. As a result of extensive research and attention, bismuth sulfide was found to be an extremely excellent pigment, and the present invention was completed. That is, the light-shielding thin film-forming composition of the present invention solves the above problems by blending 70 to 20 parts by weight of bismuth sulfide with 30 to 80 parts by weight of a negative resist, and more specifically, If necessary, a photoinitiator, a photosensitizer, a reactive diluent and the like are added in appropriate amounts to impart curability, and 0 to 50 parts by weight of other pigments are further added.

The light-shielding thin film-forming composition of the present invention will be described in detail below. As the negative resist used in the present invention, a so-called UV curable resist that is cured by a light source in the UV region is preferable because of its ease of use. Also,
Such negative resists are mainly composed of various synthetic resins such as acrylic, urethane, epoxy, synthetic rubber, polyvinyl alcohol, and natural rubber, or gelatin, which may be used alone or It is formed by mixing and mixing. Note that these materials are commercially available and can be easily obtained.

As the bismuth sulfide (Bi2S3) compounded in the negative resist, those having a particle size of about 0.1 μm to 1.0 μm are suitable. Further, such bismuth sulfide has a characteristic that it is black and stable even at a high temperature of 300 ° C., and has high electric resistance and low environmental pollution. As a method for synthesizing such bismuth sulfide, (1) bismuth chloride is heated in dry hydrogen sulfide. (2) Pass hydrogen sulfide through a hydrochloric acid solution of bismuth chloride. (3) Heat a neutral solution of bismuth nitrate with sodium thiosulfate. Although any of the above methods can be used, (2),
The method (3) is preferable because fine powder can be synthesized.

The compounding amount of bismuth sulfide with respect to the negative resist is 70 to 20 parts by weight with respect to 30 to 80 parts by weight of the negative resist. This is because when the compounding ratio of bismuth sulfide and the negative type resist is larger than 70:30, the photocurability is remarkably deteriorated, while the ratio of 20: 8.
This is because if it is smaller than 0, the light shielding rate of the light shielding thin film becomes small, which is not practical. In order to improve the dispersibility of the bismuth sulfide powder in the negative resist, for example, a silane coupling agent or a titania coupling agent (KR-46B [manufactured by Ajinomoto Co., Inc.]) may be used to improve the dispersibility of the bismuth sulfide powder. The surface treatment may be performed.

Pigments that can be used in combination with bismuth sulfide include
In addition to black pigments such as carbon black, titanium black, black iron oxide and black dye that have been conventionally used, titanium white, red iron oxide, phthalocyanine pigments, perylene pigments and other inorganic or organic pigments There are pigments, extender pigments such as aluminum silicate and magnesium silicate, which can be used alone or in combination with bismuth sulfide.

These pigments are added for the purpose of improving the coating property, improving the smoothness of the light-shielding thin film obtained by the back exposure method, adjusting the film thickness, etc., but do not lose the excellent pigment properties of bismuth sulfide. It is desirable that the amount be as small as possible. When using a pigment with extremely low electrical resistance such as carbon black in combination with bismuth sulfide,
It is necessary to pay particular attention to the electric resistance of the resulting light-shielding coating film. The weight ratio of the negative resist to the total pigment containing bismuth sulfide is the same as the case of the compounding ratio of the negative resist to bismuth sulfide described above, and the negative resist: all pigment = 80: 20 to 30:70. The range of is desirable. That is, when the weight ratio of the pigment is larger than 30:70, the photocurability is remarkably lowered, while when the pigment ratio is smaller than 80:20, the light shielding ratio of the light shielding thin film obtained is small. This is because neither is practical.

In order to obtain the light-shielding thin film forming composition of the present invention, first, a negative resist and bismuth sulfide and a pigment which is optionally used together are mixed in a predetermined ratio and sufficiently kneaded, and then a photoinitiator, The composition is obtained by adding an appropriate amount of a photosensitizer. When the light-shielding thin film-forming composition thus obtained is used, a viscosity modifier may be added to improve its coating workability, and a suitable organic solvent such as hydrocarbon, ester or ketone, or You may use it after adding water and diluting to an appropriate viscosity. Further, when it is desired to improve the adhesion, it is effective to add a silane coupling agent, a titanium coupling agent, or the like. However, it should be noted that the addition of these may impair the storage stability of the composition.

Next, a method of forming a light-shielding thin film on a transparent substrate by a backside exposure method using such a light-shielding thin film forming composition will be described. First, the transparent substrate surface is coated with the light-shielding thin film-forming composition by a method such as roll coating, spin coating, spray coating, screen printing, or offset printing, and prebaking is performed if necessary to obtain a film having a thickness of 2 μm to 20 μm. Form an uncured coating film. Here, a glass plate, a plastic plate, a plastic film, or the like is used as the transparent substrate.

Next, the back side of the transparent substrate is irradiated with an ultraviolet irradiation device using an ultra-high pressure mercury lamp or a metal halide lamp to expose it for 0.5 to 60 seconds. Then,
The light-shielding thin film-forming composition on the substrate cures from the substrate to a thickness of about 0.5 to 3.0 μm depending on the exposure conditions. Then, the substrate is immersed in a developing solution for about 10 seconds to 5 minutes or showered to remove the uncured portion. The developer is variously selected depending on the type of the negative resist used, but is usually an organic solvent such as ester, ketone, alcohol, aromatic and aliphatic hydrocarbon, chlorinated hydrocarbon or sodium hydroxide, An inorganic or organic alkaline aqueous solution such as sodium carbonate or tetramethylammonium hydroxide is used.

Incidentally, in forming such a thin film, if a fine thin film pattern having a light-shielding property such as a color filter is previously formed on a transparent substrate, curing by light does not occur on the pattern. Therefore, the thin film is eluted at the time of development, and the light-shielding thin film that functions as a black mask is formed only in the gap of the pattern of the color filter. As a method of forming a color filter on such a transparent substrate, the electrodeposition method described below is suitable.

To form a color filter by the electrodeposition method, first, as an electrodeposition paint, a red inorganic pigment (azo metal salt red pigment), a green inorganic pigment (phthalocyanine green), and a blue inorganic pigment (phthalocyanine blue). An aqueous solution of anionic polyester resin in which is dispersed [manufactured by Shinto Chemitron: red (Syntron F. Red. C (R73)], green (Syntron F. Green. C (G34)), blue (Syntron F. Blue. C (B18)) is prepared. Separately from this, on a glass substrate with a thickness of 1.1 mm,
An ITO (15Ω / cm2) circuit with a width of 90 μm,
Transparent transparent conductive circuit patterns are prepared by forming parallel straight lines at intervals of m (110 μm pitch).

Next, on the transparent conductive circuit pattern, 50 to 80 V is further applied in the order of red, green and blue according to various types.
For 10 to 20 seconds to form three primary color filters on the transparent conductive circuit pattern. Then, the transparent substrate is thoroughly washed with water and baked at 200 ° C. for 30 minutes to form a color filter thin film of red, green and blue having a thickness of 1.5 μm.

[0019]

According to the light-shielding thin film-forming composition of the present invention, bismuth sulfide is black and stable even at a high temperature of 300 ° C., and has high electric resistance and low environmental pollution. If a fine light-shielding thin film is formed in the gap, the obtained thin film becomes a black thin film having excellent characteristics such as high light-shielding property.

[0020]

EXAMPLES Hereinafter, a method for forming a light-shielding thin film on a transparent substrate using the composition which is one example of the present invention will be specifically described. First, a transparent conductive pattern was formed on a transparent glass substrate by the method described above, and a color filter was further formed thereon.

Separately from this, 50 parts by weight of bismuth sulfide (Sumitomo Cement Co., Ltd.) was added to 50 parts by weight of an acrylic negative resist (Nippon Kayaku Co., INC-116N), and butyl carbitol as a solvent. Acetate 5
Then, 3 parts by weight of a photoinitiator Irgacure # 907 (manufactured by Ciba-Geigy) was dissolved in the resulting mixture to obtain a composition of the present invention. Next, the composition is applied by screen printing to the entire transparent glass substrate on which the color filter is formed, and further 9
Prebaked at 0 ° C for 10 minutes. When the thickness of the obtained coating film was measured, it was 10 μm.

Next, 80 W / cm 2 of UV light was irradiated from the back side of this transparent glass substrate from a distance of 15 cm for 4 seconds for exposure. The main wavelength of UV light at this time is 313
nm and 365 nm. After that, the exposed glass substrate was immersed in butyl cellosolve for 2 minutes to remove the light-shielding thin film in the uncured portion, further washed with ion-exchanged water, and then heated at 200 ° C. for 30 minutes.

When the substrate thus obtained was observed, red, green and blue thin film patterns (color filters) were observed.
It was confirmed that the light-shielding black thin film was accurately formed in the gap. The light-shielding rate, volume resistivity, and heat resistance of such a light-shielding black thin film were investigated, and the results are shown in Table 1. The volume resistivity was measured at 10V.

[0024]

[Table 1] For comparison, the composition shown in Table 2 was used to form a light-shielding thin film in the same manner as in Examples, and the characteristics thereof were investigated and are also shown in Table 1.

[Table 2] As shown in Table 1, the thin film of the present invention is 40
It was confirmed that it has excellent characteristics as compared with the comparative example, such as having a high light-shielding property of 99.9% in the wavelength range of 0 nm to 700 nm.

[0025]

The light-shielding thin film-forming composition of the present invention has black bismuth sulfide and is stable even at a high temperature of 300 ° C., and has high electric resistance and low environmental pollution. If a fine light-shielding thin film is formed in the gap, the obtained thin film becomes a black thin film having excellent characteristics such as high light-shielding property. Therefore, when the black matrix is formed by using this light-shielding thin film-forming composition in the production of a color filter used for a liquid crystal display, the gap of the thin film functioning as a color filter is filled, and unnecessary light is shielded and other characteristics are obtained. It will be improved and a display of extremely excellent quality can be produced.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical indication location G03F 7/004 511 521 (72) Inventor Ken Ken Uehara Sumitomo Cement Research Co., Ltd. (72) Inventor Tsutomu Watanabe 6-1073 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Shinto Paint Co., Ltd. (72) Inventor Go Tokuda 6-1073 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Shinto Paint Incorporated (72) Inventor Nobuhiko Nishihara 6-1073 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Shinto Paint Co., Ltd.

Claims (1)

[Claims] 1. A light-shielding thin film forming composition used in a backside exposure method, comprising 70 to 20 parts by weight of bismuth sulfide mixed with 30 to 80 parts by weight of a negative resist. Thin film forming composition.