KR100708310B1 - Photoresist composition for column spacer of liquid crystal display - Google Patents

Abstract

The present invention relates to a photosensitive resin composition for column spacers of a liquid crystal display device, and more particularly, to a photosensitive resin composition for column spacers of a liquid crystal display device for compensating for nonuniformity of cell gap caused by thickness variation in a patterned column spacer. will be. The present invention provides a photosensitive resin composition for column spacers comprising an alkali-soluble copolymer, a polyfunctional acrylic monomer having two or more ethylenically unsaturated bonds, an alkylene glycol- (meth) acrylate monomer or oligomer, a photopolymerization initiator and a solvent. do. According to the present invention, it is possible to provide a photosensitive resin composition for column spacers having a very high compression displacement and recovery rate as compared with the prior art.

Column spacer, compression displacement, recovery rate, alkylene glycol- (meth) acrylate monomer

Description

Photosensitive resin composition for column spacers of a liquid crystal display element {PHOTORESIST COMPOSITION FOR COLUMN SPACER OF LIQUID CRYSTAL DISPLAY}

1 is a view for explaining the cell gap non-uniformity generated in the pattern column spacer manufacturing process.

2 is a view for explaining the physical properties of the spacer formed of the photosensitive resin of the present invention.

The present invention relates to a photosensitive resin composition for column spacers of a liquid crystal display device, and more particularly, to a photosensitive resin composition for column spacers of a liquid crystal display device for compensating for nonuniformity of cell gap caused by thickness variation in a patterned column spacer. will be.

The liquid crystal display device is constituted by upper and lower panels having a constant interval and liquid crystal injected between the panels. The gap between the upper and lower panels is called a cell gap and determines the thickness of the injected liquid crystal. In the liquid crystal display device, the cell gap must be kept constant throughout the panel. This is because the uniformity of the cell gap affects the fast response characteristics, contrast, and wide viewing angle of the liquid crystal.

Conventionally, a technique for adjusting the cell gap is to control the cell gap by dispersing and applying spherical or cylindrical spacer particles such as transparent glass, silica particles, or plastic beads that are slightly larger than the cell gap in the middle of two substrates. Has been used.

However, this method not only makes it difficult to disperse and apply the spacer particles in a desired position, but also causes other problems in that the particle position changes due to the agglomeration, vibration, or external impact of the particles.

According to this method, a process of causing color change and image distortion of the liquid crystal display device due to spacer particles or scattering incident light in the effective pixel region of the liquid crystal display device, and causing damage to the alignment layer and the electrode, etc. It may also provide the cause of the failure.

In order to solve this problem, a method of manufacturing a patterned column spacer using a photosensitive resin composition has been proposed. This method is performed by applying a photosensitive resin composition to a substrate and then exposing the substrate coated with the photosensitive resin composition to ultraviolet rays using a mask having a predetermined pattern corresponding to the column spacer pattern, and removing the unexposed portion of the resin composition. Form a spacer. Since this method can form the spacer in a fixed position at a desired position, the above-mentioned problem can be solved and the contrast and aperture ratio of the liquid crystal display element can be improved.

Examples of such methods include Korean Patent Laid-Open Publication Nos. 1999-88297, 2002-76924, and 2002-66504. These published patents propose a composition for column spacers comprising a polyvalent acrylate crosslinking agent and a photoinitiator using a binder polymer as an acrylic copolymer, and it is possible to form column spacers having excellent pattern stability, film thickness uniformity, and thermal stability. It is described. However, in order to manufacture a column spacer having a desired thickness in such a patterned column spacer, the photoresist film coating process must be repeatedly performed several times, and the volume nonuniformity of the final spacer film due to the volume shrinkage occurs in the drying process after curing. It is inevitable.

The thickness variation occurring in the final spacer causes the cell gap to be uneven in the bonding process of the upper substrate and the lower substrate. 1 is a view for explaining the cell gap non-uniformity generated in the pattern column spacer manufacturing process.

Referring to FIG. 1, if there is a deviation in the thickness of the spacers 20 formed in the color filter substrate 10, the spacing s formed by bonding with the array substrate (not shown) is different at each point of the substrate. As a result, the cell gap after bonding becomes uneven. In this regard, the above-mentioned conventional published patents have focused on reducing the thickness variation between the formed spacers. However, to date, this approach has not been an effective countermeasure to cure cell gap non-uniformity.

An object of the present invention is to provide a photosensitive resin composition for a column spacer that can uniformize the cell gap by acting as a buffer against the spacer thickness variation even in the presence of the mechanical properties of the spacer to be finally formed.

In order to achieve the said technical subject, this invention provides the photosensitive resin composition for column spacers which consists of the following compositions.

(a) alkali soluble copolymers;

(b) a polyfunctional acrylic monomer having two or more ethylenically unsaturated bonds;

(c) alkylene glycol- (meth) acrylate monomers or oligomers represented by the following general formula (1);

(d) photopolymerization initiators; And

(e) solvent

[Formula 1]

Where m = 2 or 4, n = 3-40, and R is H or CH ₃ .

In the present invention, the alkali-soluble copolymer is

(a1) unsaturated carboxylic acids, unsaturated carboxylic anhydrides or a mixture of both materials; And

(a2) It can be obtained by radical polymerization of at least two or more compounds selected from olefinically unsaturated compounds.                     

In the present invention, the polyfunctional acrylic monomer is propylene glycol methacrylate, tetraethylene glycol methacrylate, bisphenoxy ethyl alcohol diacrylate, tris hydroxyethyl isocyanurate trimethacrylate, trimethyl propane trimetha It is preferable to include at least one compound selected from the group consisting of acrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate and dipentaerythritol hexamethacrylate.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a view for explaining the physical properties of the spacer formed of the photosensitive resin of the present invention.

Referring to FIG. 2, the spacer 30 formed by the pattern process has a constant thickness T (state S ₀ ). Although only one spacer 30 is shown in FIG. 2, the thickness T of each spacer 30 formed on the substrate has a certain range of deviation.

When another substrate, such as an array substrate, is pressed onto the spacer, the thickness of the spacer decreases (state S ₁ ). The displacement by crimping at this time is indicated by the reference number D ₁ . In addition, when the pressing force F is removed, the thickness of the spacer is increased by the restoring force (state S ₁ ). At this time, the difference between the thickness of the spacer and the initial thickness of the non-pressed spacer is indicated by the reference numeral D ₂ .

The elastic properties of the spacer to be finally formed can be expressed by the following formula.

Compression displacement (D ₁₎ in the above formula refers to the change in thickness when the applied external pressure, and reconstruction ratio is the ratio of change in thickness upon release compression state for the compression displacement (S ₂₎ in the pressing state (S ₁₎ do.

The photosensitive resin of the present invention is designed to have a large value of the compression displacement (D ₁ ) and the recovery rate of the manufactured spacer. High compression displacement can eliminate or reduce the number of spacers that do not contact the upper substrate when the upper substrate is pressed against the lower substrate. In addition, the high recovery rate allows the spacer to support the upper substrate without being deformed by the pressing force to keep the cell gap constant.

Column spacers that meet these conditions can perform a buffer against cell gap nonuniformity caused by spacer thickness variation.

In order to implement the above-mentioned principle, the photosensitive resin composition of this invention consists of the composition of following (a)-(e).

(a) alkali-soluble copolymer

As the binder polymer of the photosensitive resin of the present invention, an alkali-soluble copolymer may be used. The alkali soluble copolymers are well known to those skilled in the art and can be obtained by radical polymerization from the following materials.

(a1) unsaturated carboxylic acids, unsaturated carboxylic anhydrides or a mixture of both materials; And

(a2) at least two or more compounds selected from olefinically unsaturated compounds.

As the compound (a1), acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid and anhydrides of these dicarboxylic acids may be used. In particular, acrylic acid, methacrylic acid and maleic anhydride are preferred in view of copolymerization reactivity, heat resistance and easy availability. These compounds may be used in combination of one or more kinds.

Examples of the compound (a2) include acrylic acid glycidyl ester, methacrylic acid glycidyl ester, α-ethyl acrylic acid glycidyl ester, α-n-propyl acrylic acid glycidyl ester, α-n-butyl acrylic acid glycy Dyl ester, acrylic acid-3,4-epoxy butyl ester, methacrylic acid-3,4-epoxy butyl ester, acrylic acid-6,7-epoxy heptyl ester, methacrylic acid-6,7-epoxy heptyl ester, α-ethyl Epoxy group-containing unsaturated compounds such as acrylic acid-6,7-epoxy heptyl ester, o-vinyl benzyl glycidyl ether, m-vinyl benzyl glycidyl ether, p-vinyl benzyl glycidyl ether, such as methyl methacrylate, ethyl Methacrylic acid alkyl esters such as methacrylate, n-butyl methacrylate, sec-butyl methacrylate and t-butyl methacrylate; Acrylic acid alkyl esters such as methyl acrylate and isopropyl acrylate; Methacrylic acid cycloalkyl esters such as cyclohexyl methacrylate, 2-methyl cyclohexyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate and isoboroyl methacrylate; Acrylic acid cycloalkyl esters such as cyclohexyl acrylate, 2-methyl cyclohexyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate and isoboroyl acrylate; Methacrylic acid aryl esters such as petyl methacrylate and benzyl methacrylate; Acrylic acid aryl esters such as phenyl acrylate and benzyl acrylate; Dicarboxylic acid diesters such as diethyl maleate, diethyl fumarate and diethyl itaconic acid; Carboxylic acid ester compounds, such as unsaturated carboxylic ester compound, such as hydroxyalkyl ester, such as 2-hydroxy ethyl methacrylate and 2-hydroxy propyl methacrylate, can be used. In addition, styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, vinyl toluene, p-methoxy styrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide Olefinically unsaturated compounds such as vinyl acetate, 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene may be used. The above-mentioned olefinically unsaturated compound can be used in mixture of 2 or more types.

As a solvent used for the synthesis | combination of the said copolymer, Alcohol, such as methanol and ethanol; Ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol diethyl ether; Propylene glycol alkyl ether acetates, such as propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, and propylene glycol butyl ether acetate, etc. are preferable.

As the polymerization initiator used in the synthesis of the copolymer (a), a normal radical polymerization initiator may be used. For example, 2,2'-azobis isobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (4-methoxy-2,4 Azo compounds such as -dimethylvaleronitrile), organic peroxides such as benzoyl peroxide, t-butyl peroxy pibarate, 1,1'-bis- (t-butyl peroxy) cyclohexane, and hydrogen peroxide. When a peroxide is used as a radical polymerization initiator, you may use it as a redox initiator by using a peroxide together with a reducing agent.

The content of the copolymer (a) in the photosensitive resin of the present invention is preferably about 10 to about 70% by weight, more preferably about 20 to 50% by weight, based on the photosensitive resin solid content. When the content is 10% by weight or less, the storage stability of the copolymer tends to be lowered, and when it exceeds 70% by weight, alkali solubility, heat resistance and surface hardness tend to be lowered.

(b) a polyfunctional acrylic monomer having two or more ethylenically unsaturated bonds

The photosensitive resin composition of this invention can use the polyfunctional acrylic monomer which has a 2 or more ethylenically unsaturated bond as a photopolymerizable material. Monofunctional, bifunctional or trifunctional or higher (meth) acrylates are preferred as the polyfunctional acrylic monomers of the present invention from the viewpoint of polymerizability and the heat resistance and surface hardness of the resulting protective film.

As monofunctional (meth) acrylate, 2-hydroxy ethyl (meth) acrylate, carbitol (meth) acrylate, isobornyl (meth) acrylate, 3-methoxy butyl (meth) acrylate, 2 -(Meth) acryloyl oxy ethyl 2-hydroxy propyl phthalate can be used.

As a bifunctional (meth) acrylate, for example, ethylene glycol (meth) acrylate, 1,6-hexanediol (meth) acrylate, 1,9-nonanediol (meth) acrylate, and propylene glycol (meth) acrylate , Tetraethylene glycol (meth) acrylate, bisphenoxy ethyl alcohol fluorene diacrylate can be used.

As (meth) acrylate more than trifunctional, for example, tris hydroxyethyl isocyanurate tri (meth) acrylate, trimethyl propane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaeryth Lithol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate can be used.

  These monofunctional, bifunctional or trifunctional or more (meth) acrylates can be used individually or in combination.

In the present invention, the content of the multifunctional acrylic monomer is preferably included in about 10 to about 70% by weight based on the total solids of the photosensitive resin.

(c) Additives to improve compression displacement and recovery rate

As described above, the photosensitive resin of the present invention includes an additive for high compression displacement and recovery rate improvement after curing. In the present invention, the additive for improving the compression displacement and recovery rate may be a compound in the form of (c1) alkylene glycol- (meth) acryl monomer or oligomer, or (c2) a double bond.

(c1) alkylene glycol- (meth) acrylic monomers or oligomers

Alkylene glycol- (meth) acrylate monomers or oligomers represented by the following general formula (1) are preferable in view of polymerizability, heat resistance, compression displacement and recovery rate. Specific examples include polyethylene glycol acrylate (n = 3-40), polyethylene glycol methacrylate (n = 3-40), polybutylene glycol acrylate (n = 3-40), polybutylene glycol methacrylate ( n = 3-40).

[Formula 1]

Where m = 2 or 4, n = 3-40, and R is H or CH ₃ .

In the present invention, the content of the alkylene glycol compound having the double bond is preferably contained about 5 to about 30% by weight based on the total solids of the photosensitive resin. If the content is less than 5% by weight, there may be no significant difference compared to the basic properties such as compression displacement and elasticity of the copolymer itself. If the content is more than 30% by weight, the development time becomes longer during the development process, which impairs fairness such as unevenness of surface and turbidity. A problem may occur.

(c2) compounds of the urethane form having a double bond

The urethane form compound represented by the following general formula (2) is also preferable as the photosensitive resin composition of the present invention.

[Formula 2]

Wherein m = 2 or 4, n = 2 to 40, R ₁ is H or CH ₃ , R ₂ is H or an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group, a phenyl group and an alkoxy group having 1 to 12 carbon atoms , A cycloalkoxy group, and an aryloxy group.

Compounds of the general formulas (1) and (2) provided as an additive in the present invention have a double bond and have good photopolymerization. In addition, [-(CH ₂ ) _m- ] _n or [-(CH ₂ ) _m -O-] _n in the general formulas 1 and 2 impart a spring-like elastic property to the photosensitive resin composition. Of course, in addition to that within the scope of the technical idea of the present invention, the photopolymerization is good, the equivalent or replaceable compounds that can improve the heat resistance of the thin film and provide a high compression characteristics and recovery rate can be used.

(d) photopolymerization initiator

The photosensitive resin composition of this invention contains the photoinitiator which generate | occur | produces the active species which can start photopolymerization of a photopolymerizable compound (b) and a compound (c) by exposure.

The photopolymerization initiator may be included in about 1 to about 15% by weight of the total composition of the photosensitive resin composition. When the content is less than 1% by weight, the coating film is easily lost in the developing step, and even if the coating film is maintained in the developing step, it is difficult to obtain a coating film having a sufficiently high crosslink density. When the content of the photoinitiator exceeds 15% by weight, the heat resistance and planarization characteristics of the protective film tend to be lowered.

Examples of the photopolymerization initiator of the present invention include thioxanthone, 2,4-diethyl thioxanthone, thioxanthone-4-sulfonic acid, benzophenone, 4,4'-bis (diethylamino) benzophenone, acetophenone, p -Dimethylaminoacetophenone, α, α'-dimethoxyacetoxybenzophenone, 2,2'-dimethoxy-2-petylacetophenone, p-methoxyacetophenone, 2-methyl [4- (methylthio) phenyl ] -2-morpholino-1-propanone, 2-benzyl-2-diethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-hydroxy-2-methyl-1 Ketones anthraquinones such as -phenylpropane-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, and 1-hydroxycyclohexylphenylketone, 1,4- Quinones such as naphthoquinone, 1,3,5-tris (trichloromethyl) -s-triazine, 1,3-bis (trichloromethyl) -5- (2-chlorophenyl) -s-triazine 1,3-bis (trichlorophenyl) -s-triazine, phenacyl chloride, tribromomethylphenylsulfone, tris (trichloromethyl) -s-triazine, etc. A halogen compound-di -t- butyl-flops acylphosphine oxides, such as peroxide 2,4,6-trimethylbenzoyldiphenylphosphine oxide, such as oxide can be used. In the present invention, the photopolymerization initiator may be used alone or in combination.

(e) solvent

In the present invention, the following materials may be used as a solvent for preparing the copolymer or maintaining the solid content and the viscosity of the composition. Alcohols such as methanol and ethanol; Ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol diethyl ether; Propylene glycol alkyl ether acetates such as propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate and propylene glycol butyl ether acetate. Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol methyl ether acetate in view of solubility in the solvent, reactivity with each component, and convenience of coating film formation; Ketones such as methyl ethyl ketone, cyclohexanone and 4-hydroxy-4-methyl-2-pentanane; Methyl, ethyl, propyl, butyl ester of acetic acid, ethyl of 2-hydroxypropionic acid, methyl ester, ethyl ester of 2-hydroxy-2-methylpropionic acid, methyl, ethyl, butyl ester of hydroxyacetic acid, ethyl lactate, lactic acid Ethyl, propyl lactate, butyl lactate, methyl of methoxyacetic acid, ethyl, propyl, butyl ester, methyl of ethyl propoxy, ethyl, propyl, butyl ester, methyl of methyl butoxy, ethyl, propyl, butyl ester, 2-methic Methyl, ethyl, propyl, butyl ester of oxypropionic acid, methyl, ethyl, propyl, butyl ester, methyl of ethyl, propyl, butyl ester, methyl of 2-butoxypropionic acid, ethyl, propyl, butyl ester, methyl of 3-methoxypropane S, such as ethyl, propyl, butyl ester, methyl of 3-ethoxy propionic acid, ethyl, propyl, butyl ester, methyl of 3-butoxy propionic acid, ethyl, propyl, butyl ester, etc. The use of reuryu preferred.

The solvent may also be used with high boiling solvents. As the high boiling point solvent which can be used, for example, N-methyl formamide, N, N-dimethyl formamide, N-methyl acetamide, N, N-dimethyl acetamide, N-methyl pyrrolidone, dimethyl sulfoxide, benzyl ethyl ether Can be mentioned.

The content of the solvent in the photosensitive resin composition of the present invention may be appropriately designed depending on the intended use. Generally, the solvent accounts for about 50 to about 80% by weight of the total composition of the photosensitive resin composition.

On the other hand, the photosensitive resin composition of the present invention may include additives commonly used in the photosensitive resin composition in order to improve a specific function, such as a surfactant or an adhesion aid in addition to the above-mentioned composition (a) to (e).

For example, the photosensitive resin composition of this invention is brand name FC-129, FC-170C, FC-430, F-172, F-173, F-183, F-470, F-475, Shin-Etsu Silicone company of 3M company Fluorine and silicone based surfactants such as KP322, KP323, KP340, KP341. The amount of the surfactant added is 5 parts by weight or less, more preferably 2 parts by weight or less based on 100 parts by weight of the copolymer. When the amount of the surfactant added exceeds 5 parts by weight with respect to the copolymer, problems such as foaming occur during application.                     

Moreover, the photosensitive resin composition of this invention may also contain an adhesion | attachment adjuvant in order to improve adhesiveness with a base | substrate. A functional silane coupling agent may be used as the adhesion aid, for example trimethoxysilyl benzoic acid, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyltri Ethoxysilane and (gamma)-glycidoxy propyl trimethoxysilane. It is preferable that the addition amount of the said adhesion | attachment adjuvant is 20 weight part or less with respect to 100 weight part of copolymers, More preferably, it is 10 weight part or less. When content of the said adhesion | attachment adjuvant exceeds 20 weight part with respect to the said copolymer, the heat resistance fall of a coating film will be easy to be caused.

Examples 1 to 5 below are examples of measuring physical properties of column spacers prepared using an alkylene glycol- (meth) acrylate monomer or oligomer as an additive (c) of the photosensitive resin composition of the present invention.

Table 1 shows the composition of alkali-soluble copolymers used in Examples 1 to 5 of the present invention.

Each copolymer of Table 1 was prepared by dissolving 2,2'-azobis isobutyronitrile in propylene glycol monomethyl ether acetate as a solvent, followed by styrene, methacrylic acid, glycidyl methacrylate and 2-hydroxyethyl meta. It is obtained by adding acrylate, dicyclopentanyl methacrylate, etc. according to the composition of Table 1, replacing with nitrogen, and gently stirring, while raising the temperature of the solution to 70 ° C. and maintaining it for 4 hours.

Alkali-soluble copolymer Furtherance Solids concentration in the polymer solution A-1 2,2'-azobis isobutyronitrile 5 parts by weight styrene 35 parts by weight methacrylic acid 15 parts by weight methacrylic acid glycidyl 40 parts by weight 2-hydroxyethyl methacrylate 10 parts by weight propylene glycol monomethyl ether acetate 200 parts by weight 35 wt% A-2 2,2'-azobis isobutyronitrile 5 parts by weight benzyl methacrylate 20 parts by weight methacrylic acid 15 parts by weight methacrylic acid glycidyl 40 parts by weight 2-hydroxyethyl methacrylate 10 parts by weight propylene glycol mono 200 parts by weight of methyl ether acetate 33 wt% A-3 2,2'-Azobis isobutyronitrile 5 parts by weight Styrene 35 parts by weight Methacrylic acid 15 parts by weight Methacrylic acid glycidyl 40 parts by weight Dicyclopentanyl methacrylate 10 parts by weight Propylene glycol monomethyl ether acetate 200 Parts by weight 33 wt% A-4 2 parts by weight of 2,2'-azobis isobutyronitrile 5 parts by weight of styrene 35 parts by weight of methacrylic acid 15 parts by weight of methacrylic acid glycidyl 40 parts by weight of butyl acrylate 10 parts by weight of propylene glycol monomethyl ether acetate 200 parts by weight 34 wt% A-5 2,2'-azobis isobutyronitrile 5 parts by weight Styrene 65 parts by weight Methacrylic acid 15 parts by weight Methacrylic acid glycidyl 20 parts by weight Propylene glycol monomethyl ether acetate 200 parts by weight 35 wt%

Example 1

Polymer A-1 of Table 1 was used as the copolymer. 100 parts by weight of the solid content of the polymer A-1, 50 parts by weight of dipentaerythritol penta / hexa acrylate as the polyfunctional acrylic monomer, 10 parts by weight of 2,4-diethyl thioxanthone as the photopolymerization initiator, ethyl 4-di 10 parts by weight of ethylaminobenzoate and 40 parts by weight of butylene glycol-acrylate oligomer (n = 12) were mixed and dissolved in propylene glycol monomethyl ether acetate to prepare a solution having a total solid content of 35% by weight. Subsequently, this solution was filtered with the filter of 0.45 micrometers of pore diameters, and the photosensitive resin composition was produced.

The photosensitive resin composition was applied to a color filter glass substrate using a spin coater, and heated at a temperature of 100 ° C. for 2 minutes on a hot plate to remove the solvent to some extent to form a coating film. Subsequently, ultraviolet rays having a central wavelength of 365 nm were irradiated onto the coating film with a dose of 150 mJ / cm ² through a photomask, followed by development with an aqueous alkali solution. The developed coating film was baked in a clean oven at 220 ° C. for 30 minutes to form a dot spacer pattern having a thickness of 3 μm and a width of 20 μm.

The formed spacer pattern was measured for pattern shape, flatness, heat resistance, solvent resistance, compression displacement and recovery rate in the following manner.

a. Pattern shape

The spacer pattern was cut in the vertical direction, and the cut surface was observed with an electron microscope, and it was evaluated that the length ratio of the bottom and the tower was 85% or more and good, and 85% or less.

b. flatness

Surface irregularities of the pattern were examined at 25 different points on the substrate in α-step to calculate the rate of change of thickness from the difference between the maximum and minimum thicknesses.                     

c. Residual rate

The spacer pattern was heated in a clean oven at 240 ° C. for 60 minutes to measure changes in film thickness before and after heating. When the change in the film thickness was less than 5%, the heat resistance was good, and when it was 5% or more, the heat resistance was evaluated as poor.

d. Solvent resistance

After the glass substrate on which the spacer film was formed was immersed in N-methylpyrrolidone, isopropyl alcohol, and acetone solution at 30 ° C. for 60 minutes, the change in appearance and thickness of the protective film was observed to evaluate the solvent resistance of the film.

e. Compression displacement and recovery

The compression displacement (D ₁ ) and the recovery rate of the spacer pattern were measured by an ultra-microscopic compressive hardness tester manufactured by Shimazu. Compression displacement and recovery were measured by load-unload using a planar indenter with a diameter of 50 μm. In the test, the reference value applied to the indenter was 5 gf / cm ³ , the loading speed was 0.45 gf / sec, and the holding time was 2 seconds.

Table 2 shows the test result of each test item of this example.

Example 2

A spacer pattern was manufactured under the same conditions as in Example 1 except that 100 parts by weight of the solid content of Polymer A-2 of Table 1 was used as a copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 2.9 μm thick and 21 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this example.

Example 3

A spacer pattern was manufactured under the same conditions as in Example 1 except that 100 parts by weight of the solid content of Polymer A-3 of Table 1 was used as a copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 3.2 mu m thick and 21 mu m wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this example.

Example 4

A spacer pattern was manufactured under the same conditions as in Example 1 except that 100 parts by weight of the solid content of Polymer A-4 of Table 1 was used as a copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 2.98 μm thick and 20.8 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this example.

Example 5

A spacer pattern was manufactured under the same conditions as in Example 1, except that 100 parts by weight of the solid content of Polymer A-5 of Table 1 was used as a copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 3.15 μm thick and 20.8 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this example.

Comparative Example 1

A spacer pattern was manufactured under the same conditions as in Example 1 except that butylene glycol-acrylate oligomer (n = 12) was not used in the photosensitive resin composition. The spacer pattern thus prepared was 3.05 μm thick and 20.5 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this comparative example.

Comparative Example 2

A spacer pattern was manufactured under the same conditions as in Example 2, except that butylene glycol-acrylate oligomer (n = 12) was not used in the photosensitive resin composition. The spacer pattern thus prepared was 3.24 μm thick and 20.9 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this comparative example.

Comparative Example 3

A spacer pattern was manufactured under the same conditions as in Example 3, except that butylene glycol-acrylate oligomer (n = 12) was not used in the photosensitive resin composition. The spacer pattern thus prepared was 3.05 μm thick and 20.5 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 2 shows the test result of each test item of this comparative example.

division flatness Residual rate Pattern shape Solvent resistance Pattern thickness T (㎛) Pattern width W (㎛) Compression Displacement D ₁ (㎛) D ₂ (μm) Recovery rate (%) Example 1 <1% O Good Good 3.00 20.0 1.442 0.546 62 Example 2 <1% O Good Good 2.90 19.0 1.396 0.570 59 Example 3 <1% O Good Good 3.20 21.0 1.385 0.580 58 Example 4 <1% O Good Good 2.98 19.8 1.348 0.595 56 Example 5 <1% O Good Good 3.15 20.8 1.452 0.605 59 Comparative Example 1 2% O Good Good 3.05 20.5 1.210 0.984 19 Comparative Example 2 2% O Good Good 3.24 20.9 1.154 0.956 17 Comparative Example 3 2% O Good Good 3.04 18.95 1.087 0.854 21

First, as can be seen from Table 2, for Examples 1 to 5 to which butylene glycol-acrylate was added, a compression displacement of about 20% or more compared to Comparative Examples 1 to 3 to which butylene glycol-acrylate was not added An increase was observed. In addition, it can be seen from Table 2 that the addition of butylene glycol-acrylate caused a sharp increase in the recovery rate.

Nevertheless, the photosensitive resin compositions used in Examples 1 to 5 do not deteriorate characteristics such as pattern shape, solvent resistance, and residual film ratio which the photosensitive resin composition generally should have. Rather, Examples 1 to 5 show improved properties compared to the comparative examples in coating film flatness.

Examples 6 to 8 below are examples of measuring physical properties of column spacers prepared using urethane acrylate as an additive (c) of the photosensitive resin composition of the present invention.

Table 3 shows the composition of the alkali soluble copolymers used in Examples 6-8 of the present invention.

Alkali-soluble copolymer Furtherance Solids concentration in the polymer solution A-6 2,2'-azobis isobutyronitrile 5 parts by weight Styrene 60 parts by weight Methacrylic acid 15 parts by weight Methacrylic acid glycidyl 35 parts by weight Propylene glycol monomethyl ether acetate 200 parts by weight 33 wt% A-7 2,2'-azobis isobutyronitrile 5 parts by weight benzyl methacrylate 60 parts by weight methacrylic acid 15 parts by weight methacrylic acid glycidyl 40 parts by weight propylene glycol monomethyl ether acetate 200 parts by weight 33 wt% A-8 2,2'-azobis isobutyronitrile 5 parts by weight styrene 35 parts by weight methacrylic acid 15 parts by weight methacrylic acid glycidyl 20 parts by weight dicyclopentanyl methacrylate 30 parts by weight propylene glycol monomethyl ether acetate 200 parts by weight part 35 wt%

The manufacturing method of each copolymer of Table 3 is the same as that of the copolymer of Table 1, and is not demonstrated here separately.

Example 6

Polymer A-6 of Table 3 was used as the copolymer. 100 parts by weight of the solid content of the polymer A-6, 50 parts by weight of dipentaerythritol penta / hexaacrylate as the polyfunctional acrylic monomer, 10 parts by weight of 2,4-diethylthioxanthone as the photopolymerization initiator, ethyl 4-di 10 parts by weight of ethylaminobenzoate, 20 parts by weight of a urethane acrylate having a double bond (m = 2, n = 6, R ₁ = H) were mixed, and the total solid content was 35 using a propylene glycol monomethyl ether acetate as a solvent. The photosensitive resin composition was manufactured so that it may be weight%.

A spacer pattern was formed in the same manner as in Example 1 with the prepared photosensitive resin composition, and the pattern characteristics were evaluated in the same manner. The thickness of the spacer pattern thus prepared was 3 μm and a width of 20 μm. Table 4 shows the test result of each test item of the present example.

Example 7

A spacer pattern was manufactured under the same conditions as in Example 6, except that 100 parts by weight of the solid content of Polymer A-7 of Table 3 was used as the copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 2.98 μm thick and 19.8 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 4 shows the test result of each test item of the present example.

Example 8

A spacer pattern was manufactured under the same conditions as in Example 6 except that 100 parts by weight of the solid content of Polymer A-8 of Table 3 was used as the copolymer of the photosensitive resin composition. The spacer pattern thus prepared was 3.15 μm thick and 20.5 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 4 shows the test result of each test item of the present example.

Comparative Example 4

A spacer pattern was manufactured under the same conditions as in Example 6 except that urethane acrylate was not used in the photosensitive resin composition. The spacer pattern thus prepared was 3.05 μm thick and 21.2 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 4 shows the test result of each test item of this comparative example.

Comparative Example 5

A spacer pattern was manufactured under the same conditions as in Example 7, except that urethane acrylate was not used in the photosensitive resin composition. The spacer pattern thus prepared was 3.24 μm thick and 20.1 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 4 shows the test result of each test item of this comparative example.

Comparative Example 6

A spacer pattern was manufactured under the same conditions as in Example 8 except that urethane acrylate was not used in the photosensitive resin composition. The prepared spacer pattern was 2.96 μm thick and 20.2 μm wide. The physical properties of each item were measured in the same manner as in Example 1 using the prepared spacer pattern. Table 4 shows the test result of each test item of this comparative example.

division flatness Residual rate Pattern shape Solvent resistance Pattern thickness T (㎛) Pattern width W (㎛) Compression Displacement D ₁ (㎛) D ₂ (μm) Recovery rate (%) Example 6 <1% O Good Good 3.00 20.0 1.38 0.49 64 Example 7 <1% O Good Good 2.98 19.8 1.28 0.48 63 Example 8 <1% O Good Good 3.15 20.5 1.31 0.45 66 Comparative Example 4 2% O Good Good 3.05 21.2 1.09 0.58 47 Comparative Example 5 2% O Good Good 3.24 20.1 1.18 0.62 47 Comparative Example 6 2% O Good Good 2.96 20.2 0.99 0.58 41

First, it can be seen from Table 4 that when urethane acrylate is added to the photosensitive resin composition, the compression displacement and recovery rate are increased as compared with the case where urethane acrylate is not added.

In addition, it can also be seen that the addition of urethane acrylate does not deteriorate characteristics such as pattern shape, solvent resistance, and residual film ratio which the photosensitive resin composition generally should have, but rather improves the coating film flatness property.

The photosensitive resin composition of this invention has the following advantages in formation of the pattern type column spacer of a liquid crystal display element.

First, the photosensitive resin composition of the present invention not only has excellent heat resistance, but also has good film flatness, solvent resistance, and pattern shape, and has excellent basic characteristics to be used as a column spacer of a liquid crystal display device.

In addition, the column spacer made of the photosensitive resin composition of the present invention has a very high compression displacement compared to that of the conventional one. Therefore, even when there is a nonuniformity in the thickness of the column spacer when the array substrate is bonded to the color filter substrate, it is possible to maintain a uniform cell gap without causing cell gap variation.

Moreover, the column spacer made of the photosensitive resin composition of the present invention has a high restoring force as compared with the conventional column spacer. Therefore, the cell spacer can be kept constant without fear of losing the cell gap holding ability due to the deformation of the column spacer upon bonding of both substrates.

Claims (3)

(Correction) The photosensitive resin composition for column spacers containing an alkali-soluble copolymer, the polyfunctional acrylic monomer which has two or more ethylenically unsaturated bonds, a photoinitiator, and a solvent, The photosensitive resin composition for column spacers which further contains the alkylene glycol- (meth) acrylate monomer or oligomer represented by following General formula (1) . [Formula 1]

Where m = 2 or 4, n = 3-40, and R is H or CH ₃ . The method of claim 1, wherein the alkali-soluble copolymer is (a1) unsaturated carboxylic acids, unsaturated carboxylic anhydrides or a mixture of both materials; And (a2) The photosensitive resin composition for column spacers obtained by radically polymerizing at least 2 or more types of compounds chosen from an olefinically unsaturated compound. The method of claim 1, wherein the multifunctional acrylic monomer Propylene glycol methacrylate, tetraethylene glycol methacrylate, bisphenoxy ethyl alcohol diacrylate, trishydroxyethyl isocyanurate trimethacrylate, trimethylpropane trimethacrylate, pentaerythritol trimethacryl A photosensitive resin composition for column spacers comprising at least one compound selected from the group consisting of latex, pentaerythritol tetramethacrylate and dipentaerythritol hexamethacrylate.

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