JPH05281415A - Formation of protective film for color filter - Google Patents

Abstract

PURPOSE:To improve a protective film characteristic and flatness and to improve heat resistance and moisture resistance by using polyorgano silcesquoxane having a specific mol. wt. and terminal group. CONSTITUTION:The surface of a color filter substrate is coated with the polyorgano silcesquoxane contg. 0.3 to 6wt.% hydroxyl group and 0.9 to 16wt.% alkoxy group as the terminal groups expressed by formula so as to have the molar ratio of both ranging from 1.0 to 2.0 and having 500 to 50000 number average mol.wt. and the coating is heated. In the formula, R1 denotes 1 to 3C alkyl group, substd. or unsubstd. phenyl group; R2 denotes 1 to 3C alkyl group or hydrogen group; (n) denotes a positive integer. The polyorgano silcesquoxane is used as a soln. prepd. by dissolving the polyorgano silcesquoxane in a solvent at the time of coating the surface of the color filter substrate with the polyorgano silcesquoxane expressed by the formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a liquid crystal color filter protective film. More specifically, it relates to a method for forming a protective film having a flat surface on a color filter, which is manufactured by dyeing, printing, electrodeposition, a pigment dispersion method or the like for a liquid crystal display device or a solid-state image pickup device.

[0002]

2. Description of the Related Art Color LCD (Liquid C
As the screen size, density, and cost of crystal displays are increasing, it is inevitable to improve the performance of color filters, and in order to maintain the reliability of color LCD displays, a protective film for color filters. As a flat film, the importance of the film is increasing.

As a structure of a color filter, red (R), green (G) and blue (B) pixels are arranged on a glass substrate, and a black matrix layer is formed between the R, G and B pixels. An overcoat layer (protective layer) made of a transparent resin is formed thereon, and a transparent conductive layer made of indium tin oxide (ITO) or the like is further formed. The R, G, and B pixel overcoat layers have flatness in which unevenness of the color filter surface is smooth to the extent that the display characteristics of the LCD are not impaired, and a film formed by ITO sputtering (with a sputtered film) that is a post-process. It is necessary to withstand the heat treatment and chemical treatment that accompanies the orientation process, the panel assembly, and the chemical treatment, and to have the performance as a protective film for the color filter pixel.

As materials for the protective layer, organic resins such as acrylic resins or polyimide resins, or those having a siloxane skeleton introduced into the resin structure have been used.

However, since acrylic resin and polyimide resin can be thickened to several tens of μm,
Although the flatness of the R, G, and B pixel patterns is obtained, satisfactory performance is not necessarily obtained in terms of film transparency, heat resistance, and hygroscopicity. In particular, regarding the heat resistance, it was not possible to form an overcoat layer that could withstand the heat treatment temperature associated with the ITO sputtered film, the alignment treatment, and the panel assembly in the subsequent steps.

Further, in recent years, so-called inorganic SOG (Spin on Glass), which is typified by tetrahydroxylan, and so-called organic SO, such as alkyltrihydroxylane, which are typified by tetrahydroxylane, as materials for forming a polysiloxane coating film.
It has been proposed to use G as a protective film and a flattening film for a color filter.

However, this inorganic SOG and organic S
It has been pointed out that the OG cured film has various problems. For example, an inorganic SOG film requires curing (curing) at a high temperature of 400 ° C. or higher in order to form a completely cured product,
250, which seems to be the limit of heat resistance of the color filter itself
A completely cured product cannot be formed by curing at ℃,
Even if high-temperature curing is performed, there is a drawback that cracks may occur if a film thickness of 1 μm or more is formed to fill the irregularities on the surface of the color filters R, G, and B pixels. Since the organic SOG film can be thickened to 1 to 2 μm, the flatness of the R, G, and B pixel patterns can be obtained, but the heat resistance of the color filter itself is considered to be 250 ° C.
A completely cured product cannot be formed by the curing of
There is a problem in degassing (heat resistance) with a sputtered film and hygroscopicity, and there is concern about the reliability of the color filter.

Therefore, an object of the present invention is to solve the above-mentioned problems in the organic SOG used for the overcoat film of the liquid crystal color filter, and it is excellent in the protective film property and the flattening property and has the above-mentioned heat resistance and moisture absorption. An object of the present invention is to provide a method of forming a liquid crystal color filter protective film having improved properties.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned objects, and as a result, in place of alkyltrihydroxysilane in organic SOG, a polyorganosilsesqui having a specific molecular weight and a terminal group has been obtained. The inventors have found that a liquid crystal color filter protective flattening film capable of achieving the above object can be obtained by using oxane, and have completed the present invention.

That is, the present invention has the general formula (I)

[Chemical 2] (In the formula, R ₁ represents an alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted phenyl group, and R ₂ represents 1 to 1 carbon atoms.
3 represents an alkyl group or a hydrogen atom, and n is a positive integer. ), A hydroxyl group of 0.3 to 6% by weight and an alkoxy group of 0.9 to 16% by weight are contained so that the molar ratio of both is in the range of 1: 0.2 to 2.0, and the number average molecular weight is 500 to The present invention provides a method for forming a protective film for a liquid crystal color filter, which comprises coating 50,000 polyorganosilsesquioxanes on a color filter substrate and heating.

In the polyorganosilsesquioxane of the general formula (I) used in the present invention, R ₁ of the side chain is an alkyl group having 1 to 3 carbon atoms (that is, methyl, ethyl, propyl group) or a substituted group. Alternatively, it is an unsubstituted phenyl group. Substituents other than these are not suitable because the heat resistance is insufficient. As the substituent of the phenyl group, an alkyl group,
An alkenyl group, a halogen group, etc. are illustrated.

In the present invention, the polyorganosilsesquioxane has terminal groups of 0.3 to 6% by weight of hydroxyl groups, 0.9 to 16% by weight of alkoxy groups and a molar ratio of both terminal groups of 1 :.
It is contained in the range of 0.2 to 2.0. A methoxy, ethoxy or butoxy group can be used as the alkoxy group.

When the hydroxyl group of the terminal group is 6% by weight or more, there is a hydroxyl group which remains unreacted after curing, which causes a drawback that the hygroscopicity of the cured film becomes high. If the amount of the terminal alkoxy group is 16% by weight or more, there is an unreacted residual alkoxy group even after curing, which causes a problem that the amount of degassing during heating of the cured film at high temperature (such as ITO sputtering) increases. Occurs. On the other hand, when the amount of the terminal hydroxyl groups is 0.3% by weight or less and the amount of the alkoxy groups is 0.9% by weight or less, the adhesiveness to the substrate and the flattening property become unsatisfactory, and the hardness of the cured film does not reach a sufficient level. Further, the molar ratio of the hydroxyl group of the terminal group to the alkoxy group is 1: 0.2 to 2.0, preferably 1: 0.5 to
It is 1.5, and the performance development during curing does not proceed smoothly even if the amount of alkoxy groups is larger or smaller than this range. That is, when the amount of alkoxy groups is small, the hygroscopicity of the cured film becomes unsatisfactory, and when the amount of alkoxy groups is large, the degassing property at the time of heating at high temperature becomes a problem.

The number average molecular weight of the polyorganosilsesquioxane in the present invention is a value obtained by converting the data measured by the GPC (gel permeation chromatography) method into a conversion value based on a calibration curve of a polystyrene standard sample. is there. The value of the number average molecular weight in the present invention is preferably 500 to 50,000. Number average molecular weight is 500
If it is smaller than the above range, the shrinkage at the time of high temperature heating and curing, which is one of the objects of the present invention, is insufficient. On the other hand, if the number average molecular weight is more than 50,000, the solubility in an organic solvent will be insufficient and the flattening characteristics will be unsatisfactory.

When the polyorganosilsesquioxane of the general formula (I) of the present invention is coated on a color filter substrate, it is used as a solution in which the polyorganosilsesquioxane is dissolved in an organic solvent.

The polyorganosilsesquioxane in the molecular weight range of the present invention is soluble in various general organic solvents, for example, alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol, acetone, methyl ethyl ketone, Ketones such as methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethylene glycol, glycerin, diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether , Propylene glycol monoethyl glycol, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol Polyhydric alcohols such as monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate and the like. Organic solvents such as ethers can be used. These solvents may be used alone or in combination of two or more.

The solid content of the polyorganosilsesquioxane in the organic solvent solution depends on the coating method, but is usually 2 to 30% by weight, preferably 5 to 20% by weight.
Is. In addition, a leveling agent, a coupling agent, a thickener, a filler, and other additives may be added to the polyorganosilsesquioxane solution in the present invention, if necessary.

When coating the polyorganosilsesquioxane solution on the color filter substrate,
Spin coating is usually used. Moreover, you may coat by dip coating, roll coating, screen printing coating, spray coating, and other methods as needed.

The film thickness of the polyorganosilsesquioxane as the liquid crystal color filter protective film in the present invention is 0.
It can be freely selected within the range of 01 to 5 μm. In particular, even if the film is thicker than 1 μm, cracks do not occur, so
It is possible to fill the concave portions of the R, G, and B pixel patterns of the color filter to make the surface flat. Further, these film thicknesses can be obtained by coating once, but the protective film may be formed by coating two or more times.

In the present invention, after coating the polyorganosilsesquioxane solution, heating is performed at 150 to 300 ° C. for 10 to 120 minutes to perform curing. At this time, depending on the type of organic solvent, 100
The organic solvent may be removed by heating at ˜200 ° C. for 1 to 10 minutes. It is desirable that the curing temperature be as high as possible within the range allowable from the heat resistance of the constituent materials, from the viewpoint of the coating material after curing and the required time, but in the polyorganosilsesquioxane used in the present invention, Two
It is possible to completely cure at a temperature of 50 ° C.

As described above, the polyorganosilsesquioxane cured film can be cured at a relatively low temperature as compared with the conventional organic SOG such as alkyltrihydroxysilane, and the obtained cured film is a relatively thick film. As a result, cracks are unlikely to occur, and the amount of degassing during heating at high temperature is small and the hygroscopicity is low as compared with the conventional organic SOG film.

From the above characteristics, polyorganosilsesquioxane is suitable for a flattening protective film of a liquid crystal color filter. Spin coating, dip coating, roll coating,
Screen printing coating, spray coating,
An arbitrary method such as brush coating can be selected. Further, in order to lower the curing temperature, it is possible to add a catalyst such as an alkali or an alkali metal salt, if necessary.

[0023]

The cured film of polyorganosilsesquioxane used in the present invention is a conventional organic SO such as alkyltrihydroxy.
The reason why a completely cured product can be formed at a lower temperature and that the cured film has less degassing property and lower hygroscopicity when compared to G is inferred as follows.

That is, the conventional curing reaction of organic SOG proceeds by the following condensation reaction accompanied by dehydration.

[Chemical 3]

On the other hand, in the polyorganosilsesquioxane of the present invention, in addition to the above reaction, the following condensation reaction involving dealcoholization is the main component.

[Chemical 4]

Since the dealcoholization reaction proceeds faster than the conventional dehydration reaction, curing proceeds faster, at a lower temperature, and the degree of completion of the reaction is higher. Here, it is considered that a high degree of completion of the reaction leads to a small shrinkage at the time of heating at a high temperature, and a low amount of unreacted —Si—OH leads to a low hygroscopicity. In the conventional organic SOG, a large shrinkage stress of curing is inevitable since the organic SOG starts from a low molecular weight material and is cured, whereas the polyorganosilsesquioxane of the present invention is an oligomer having a constant molecular weight at the start. Therefore, it is considered that the shrinkage during curing becomes small.

[0027]

The present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these. In addition, each physical-property value in an Example and a comparative example was measured according to the following method.

(1) Measurement of number average molecular weight (Mn) Data measured by GPC method (Shod of Showa Denko KK)
(ex column is used) is represented by a conversion value based on a calibration curve of a polystyrene standard sample.

(2) Measurement of the amount of terminal --OH groups and --OC ₂ H ₅ groups By adding an acid to the solution, --OH groups are converted into H ₂ O and --OC.
_{The 2} H ₅ group is defined as C ₂ H ₅ OH, and the terminal —O
H, was quantified -OC ₂ H _5.

(3) Spin coating method A spinner 1H360 type (manufactured by Kyoei Semiconductor Co., Ltd.) was used.
m, 10 seconds, and then 1000 rpm for 5 seconds to form a coating film.

(4) Method of measuring film thickness The film thickness is measured by measuring the step between the part where the coating film is formed and the part where there is no coating film formed on the glass substrate with Dectac 3030 (manufactured by Sloan). It was measured.

(5) Method for measuring physical properties of coating film A coating film was formed on a heat-resistant glass substrate and heat-treated at 250 ° C. for 1 hour, and then the cross-cut adhesion of the coating film was observed with a 50 × microscope.

Acid and alkali resistance A coating film is formed on a glass substrate and (1) 15N in 10N HCl.
Immersion at 0 ° C for 10 minutes, (2) Immersion in 4% KOH at room temperature for 10 minutes, (3)
Heated at 180 ℃ for 2 hours (30 minutes each for heating and cooling), (4) 4%
After the KOH was soaked at room temperature for 10 minutes, the cross-cut adhesion of the coating film was observed with a 50 × microscope.

Constant Temperature and Humidity Test After forming a coating film on a glass substrate and treating it at 85 ° C. and 95% RH for 75 hours, the cross-cut adhesion of the coating film was observed with a 50 × microscope.

Flatness A coating film was formed on a color filter substrate on which R, G, and B pixel patterns were formed, and Rmax (maximum height of surface roughness) was measured with Dectak 3030 (manufactured by Sloan).

Example 1 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 1.4% by weight, the ethoxy group content is 3.6% by weight, and the molar ratio of the two. 20 parts by weight of a ladder type silicone oligomer having a ratio of 1: 1 and a number average molecular weight Mn of 2500 was dissolved in 80 parts by weight of a mixed solvent of ethanol and butanol (weight ratio 1: 1) to obtain a coating solution. This coating solution was spin-coated on a glass substrate to a film thickness of 1 μm, heated at 120 ° C. for 20 minutes and then at 200 ° C. for 30 minutes in a clean oven to be cured. After curing, it was cooled to room temperature and various physical properties were measured. The results are shown in Table 1.

Example 2 In the general formula (I), R ₁ consists of 90 mol% of methyl group and 10 mol% of phenyl group, R ₂ consists of hydrogen and ethyl group, and the content of hydroxyl group is 4.9% by weight and ethoxy group is contained. Ladder type silicone oligomer 18 having an amount of 6.6% by weight, a molar ratio of the two of 1: 0.5, and a number average molecular weight Mn of 1300.
Part by weight was dissolved in 82 parts by weight of a mixed solvent of ethyl acetate and butyl acetate (1: 1 by weight ratio) to obtain a coating solution. This coating solution was coated in the same manner as in Example 1, and after curing, various physical properties were measured. The results are shown in Table 1.

Example 3 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 3.0% by weight, the ethoxy group content is 14.2% by weight, and the molar ratio of the two. 1: 1.8 and 16 parts by weight of a ladder type silicone oligomer having a number average molecular weight Mn of 7200 are dissolved and applied in 84 parts by weight of a mixed solvent of ethanol, butanol and ethylene glycol monoethyl ether acetate (weight ratio 4: 4: 2). A liquid was obtained, this coating liquid was coated in the same manner as in Example 1, and after curing, various physical properties were measured. The results are shown in Table 1.

Comparative Example 1 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 9.4% by weight, the ethoxy group content is 25% by weight, and the molar ratio of the two is 20 parts by weight of a ladder type silicone oligomer having a 1: 1 number average molecular weight Mn of 400 was dissolved in 80 parts by weight of a mixed solvent of ethanol and butanol (weight ratio 1: 1) to obtain a coating solution. Coating was performed in the same manner as in 1 and various physical properties were measured after curing. The results are shown in Table 1.

Comparative Example 2 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 0.1% by weight, the ethoxy group content is 0.3% by weight, and the molar ratio of the two is 20 parts by weight of a ladder type silicone oligomer having a ratio of 1: 1 and a number average molecular weight Mn of 60,000 was dissolved in 80 parts by weight of a mixed solvent of ethanol and butanol (weight ratio 1: 1) to obtain a coating solution.
This coating solution was coated in the same manner as in Example 1, and after curing, various physical properties were measured. The results are shown in Table 1.

Comparative Example 3 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 3.9% by weight, the ethoxy group content is 1.0% by weight, and the molar ratio of the two. Is 1: 0.1
Then, 20 parts by weight of a ladder type silicone oligomer having a number average molecular weight Mn of 2400 was dissolved in 80 parts by weight of a mixed solvent of ethanol and butanol (weight ratio 1: 1) to obtain a coating solution.
This coating solution was coated in the same manner as in Example 1 and after curing, various physical properties were measured. The results are shown in Table 1.

Comparative Example 4 In the general formula (I), R ₁ is a methyl group, R ₂ is hydrogen and an ethyl group, the hydroxyl group content is 0.6% by weight, the ethoxy group content is 4.3% by weight, and the molar ratio of the two. Is 1: 2.5
Is dissolved in 80 parts by weight of a mixed solvent of ethanol and butanol (weight ratio 1: 1) to obtain a coating solution, and the coating solution is prepared in the same manner as in Example 1. After coating and curing, various physical properties were measured. The results are shown in Table 1.

Comparative Example 5 A coating solution prepared by dissolving 17 parts by weight of methyltrihydroxysilane in a mixed solvent of methanol and ethyllenglycol butyl ether (weight ratio of 1: 1) was coated in the same manner as in Example 1 and cured. The physical properties were measured. The results are shown in Table 1.

Comparative Example 6 Various physical properties were measured after coating and curing in the same manner as in Example 1 using a coating solution prepared by dissolving 15 parts by weight of an acrylic thermosetting resin in ethyl acetate. The results are shown in Table 1.

[0045]

[Table 1]

[0046]

INDUSTRIAL APPLICABILITY In the polyorganosilsesquioxane used in the present invention, the condensation reactivity of the terminal group is greatly improved as compared with the conventional one, and the molecular weight is the same as that of the conventional organic SOG. In comparison, since those in the polymer region are adopted from the oligomer, the heat curing can be performed at a relatively low temperature, the curing shrinkage is small, and the completion degree of the curing reaction is high. Therefore, the generated gas of the cured coating film is small and the hygroscopicity is also low. Polyorganosilsesquioxane is excellent in transparency and flattening ability, and is suitable as a flattening protective film for liquid crystal color filters, in addition to the above-mentioned characteristics.

Claims (1)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ₁ represents an alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted phenyl group, and R ₂ represents 1 to 1 carbon atoms.
3 represents an alkyl group or a hydrogen atom, and n is a positive integer. ), A hydroxyl group of 0.3 to 6% by weight and an alkoxy group of 0.9 to 16% by weight are contained so that the molar ratio of both is in the range of 1: 0.2 to 2.0, and the number average molecular weight is 500 to A method for forming a protective film for a liquid crystal color filter, which comprises coating 50,000 polyorganosilsesquioxanes on a color filter substrate and heating.