WO2006129924A1

WO2006129924A1 - Method for simultaneously forming color filter overcoat and column spacer of lcd and negative photoresist composition usable therein

Info

Publication number: WO2006129924A1
Application number: PCT/KR2006/001893
Authority: WO
Inventors: Suk-Young Choi; Seon-Hyuk Kim; Hyo-Joon Kim; Ji-Hyun Park; Eun-Suk Park
Original assignee: Ansung Fine Chemical Co., Ltd.
Priority date: 2005-06-03
Filing date: 2006-05-19
Publication date: 2006-12-07
Also published as: KR20060125993A; KR100791022B1

Abstract

Disclosed are a method for simultaneously forming a color filter overcoat and a column spacer of LCD and a negative photoresist composition usable therein. The method according to the present invention includes: (Sl) forming a photoresist film by applying a negative photoresist composition onto a substrate of a liquid crystal; (S2) exposing the photoresist film through a mask composed of a transflective region and a transmissive region; and (S3) forming a region of the photoresist film into a color filter overcoat and a column spacer, respectively. The method of the present invention may be useful to reduce the manufacturing cost and enhance a yield of a liquid crystal display since its manufacturing process can be easily reduced by simultaneously forming, on the color filter substrate, a column spacer and a color filter overcoat having a good shape and height difference.

Description

METHOD FOR SIMULTANEOUSLY FORMING COLOR

FILTER OVERCOAT AND COLUMN SPACER OF LCD AND

NEGATIVE PHOTORESIST COMPOSITION USABLE

THEREIN Technical Field

[1] The present invention relates to a method for forming a color filter overcoat and a column spacer of a liquid crystal display (LCD), and a negative photoresist composition usable therein. Background Art

[2] Generally, a liquid crystal display (LCD) presents an image by using an optical anisotropy of a liquid crystal, and has a structure in which it is filled with the liquid crystal arranged mainly between two facing upper and lower panels, namely between a color filter substrate and a TFT substrate.

[3] Hereinafter, a structure of a conventional liquid crystal display will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing a liquid crystal display. As shown in FIG. 1, the liquid crystal display has two substrates 101a, 101b facing each other, and a liquid crystal filled between them.

[4] In the TFT substrate as a lower substrate, a gate insulator 102 is formed on a substrate 101a, and data lines 103 are patterned on the gate insulator 102. An overcoat 104 composed of a silicon nitride material is laminated on the substrate including the data lines 103, and a pixel electrode 105 composed of an ITO material is formed on the overcoat 104 at a regular distance.

[5] In the color filter substrate as an upper substrate, black matrixes 106 for preventing the light from being transmitted into a region except the pixel electrode are formed on the substrate 101b, and red (R), green (G) and blue (B) color filters 107 for displaying colors are formed in the space between the black matrixes 106. On the front of the substrate including the color filters 107 is formed a color filter overcoat 108 for flattening an irregular surface of the color filter 107 and having excellent physical properties such as transmittance, thermal resistance, chemical resistance, close adhesivity, mechanical strength, etc. Also, column spacers 109 are formed on the color filter overcoat 108 at a predetermined distance to maintain a cell gap.

[6] Referring to a method for forming the color filter overcoat 108 and the column spacer 109 as configured above, the method undergoes a two-step process including a step of forming a color filter overcoat 108 by firstly applying a photoresist composition, for example a negative photoresist composition including a binder resin, a polymeric compound having an ethylenically unsaturated bond, a photoinitiator and a solvent onto a substrate on which the black matrix 106 and the color filter 107 are formed and then curing the applied photoresist composition, and a step of forming a column spacer 109 by applying the photoresist composition on the formed color filter overcoat 108 again and exposing and developing the applied photoresist composition through a mask.

[7] However, as the process for manufacturing the color filter substrate is complicated, additional manpower, time, materials, etc. are further required. Consequently, the manufacturing cost increases and the yield decreases. Accordingly, there have been attempts to reduce the process steps by simultaneously forming a color filter overcoat and a column spacer.

[8] Japanese Patent Publication No. 1996-114809 disclose a method for simultaneously forming a color filter overcoat and a column spacer by applying a negative photoresist composition at a predetermined height onto a substrate in which a black matrix and a color filter are formed, to form a photoresist film; exposing the photoresist film using the conventional mask composed of a transmissive region for transmitting all incident ultraviolet rays and a non-transmissive region for intercepting all incident ultraviolet rays; and then controlling a developing time to maintain a region of the photoresist film on the lower surface of the non-transmissive region at some portion of the predetermined height. Also, Japanese Patent Publication No. 2000-327875 discloses a method for simultaneously forming a color filter overcoat and a column spacer using the same method as described in the above-mentioned published disclosure except that a positive photoresist composition is used therein.

[9] However, the region of the photoresist film formed on the lower surface of the non- transmissive region in the mask is not cured as it can be not exposed in the conventional methods known in the prior art. Accordingly, it is difficult to maintain the region of the photoresist film at a desired height by controlling only a developing time since it is highly sensitive to a developer, and a surface of the film also has a poor flatness.

Disclosure of Invention Technical Problem

[10] Accordingly, the present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to provide a method for simultaneously forming, on a color filter substrate, a color filter overcoat and a column spacer of a liquid crystal display (LCD) having a good shape and height difference. [11] It is another object of the present invention to provide anegative photoresist composition capable of increasing a height difference between the color filter overcoat and the column spacer and accomplishing a flat surface when it is applied to the method for simultaneously forming a color filter overcoat and a column spacer. Technical Solution

[12] In order to accomplish the above object, the present invention provides a method for simultaneously forming a color filter overcoat and a column spacer of a liquid crystal display (LCD), the method including (Sl) forming a photoresist film by applying a negative photoresist composition at a predetermined height onto a substrate of a liquid crystal display in which a black matrix and a color filter are formed; (S2) exposing the photoresist film through a mask composed of a transflective region transmitting only some of incident ultraviolet rays and whose position is set to correspond to the color filter; and a transmissive region transmitting all incident ultraviolet rays and whose position is set to correspond to the black matrix; and (S3) forming a region of the photoresist film, exposed through the transflective region of the mask to be maintained at some portion of the predetermined height, into a color filter overcoat; and a region of the photoresist film, exposed through the transmissive region of the mask to be maintained at all of the predetermined height, into a column spacer, by developing the exposed photoresist film.

[13] In order to accomplish the other object, the present invention provides a negative photoresist composition including a binder resin, a polymeric compound having an ethylenically unsaturated bond, a photoinitiator and a solvent, wherein the pho- toinitiator includes at least one phosphine oxide photoinitiator selected from the group consisting of compounds represented by the following Chemistry Figures 1, 2 and 3;

[14] Chemistry Figure 1

0 R¹-^P-B δ

[15] Chemistry Figure 2

[16] Chemistry Figure 3

[17] wherein R , R , R , R , R and R are independently hydrogen or at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, a cyclic alkyl group, aromatic hydrocarbon, halogen, amine and amide,

[18] R is at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, alkenyl and aromatic hydrocarbon, and [19] A and B are independently at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, a cyclic alkyl group, aromatic hydrocarbon, halogen, amine, amide and an oxyalkyl group.

[20] In the negative photoresist composition of the present invention, a resin represented by the following Chemistry Figure 4 is preferably used as the binder resin; [21] ChemistryFigure 4

[22] wherein a, b, c, d and e are independently mole ratios of the monomers, wherein 0<a<l, 0<b<l, 0<c<l, 0<d<l, and 0<e<l, provided that 0<a+b+c+d<l, and a+b+c+d+e=l,

[23] X is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, [24] Y , Y and Y are independently at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxy alkyl group, an epoxy group, a benzene group, a phenylethyl group, an alkyl group containing amine, amide, carbamate or urea, and an alkenyl group,

[25] Y is aromatic hydrocarbon, [26] Z is at least one selected from the group consisting of an alkyl group having 1 to 24 carbon atoms, a cyclic alkyl group and aromatic hydrocarbon,

[27] n is an integer from 1 to 12, and [28] k is an integer from 0 to 6. [29] Also, the solvent used in the negative photoresist composition of the present invention preferably includes an alkyl acetate solvent represented by the following Chemistry Figure 5; [30] ChemistryFigure 5

O

Λ,« 8

Q-

[31] wherein R , 7 is an alkyl group having 1 o 12 carbon atoms.

Brief Description of the Drawings

[32] These and other features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description with reference to the accompanying drawings. In the drawings:

[33] FIG. 1 is a cross-sectional view showing a configuration of a conventional liquid crystal display; and

[34] FIG. 2 is a schematic view illustrating a method for simultaneously forming a color filter overcoat and a column spacer of a liquid crystal display (LCD) according to the present invention. Best Mode for Carrying Out the Invention

[35] Hereinafter, preferred embodiments of the present invention will be described in detail referring to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

[36] In the method for simultaneously forming a color filter overcoat and a column spacer of a liquid crystal display (LCD) according to the present invention, a photoresist film 121 is firstly formed by applying a negative photoresist composition at a predetermined height onto a substrate of a liquid crystal display in which a black matrix 106 and a color filter 107 are formed, as shown in FIG. 2 (Sl). The applied negative photoresist composition, namely the photoresist film 121 is formed with a thickness obtained by adding the thickness of the color filter overcoat, formed according to the conventional two-step process, to the thickness of the column spacer formed on the color filter overcoat.

[37] Then, the photoresist film 121 is exposed through a mask 200 composed of a transflective region (region B) transmitting only some of incident ultraviolet rays and whose position is set to correspond to the color filter 107; and a transmissive region (region A) transmitting all incident ultraviolet rays and whose position is set to correspond to the color filter 106 (S2). The UV-exposure time is controlled to completely cure a region of the photoresist film exposed through the transmissive region (region A) of the mask 200 and not to completely cure a region of the photoresist film exposed through the transflective region (region B) of the mask 200.

[38] The mask 200 used in exposing the photoresist film 121 is composed of a transflective region (region B) for transmitting some of incident ultraviolet rays, for example 5 to 80 % of the incident ultraviolet rays; and a transmissive region (region A)for transmitting all incident ultraviolet rays. According to a process as described later, a region of the photoresist film on the lower surface of the transmissive region (region A) functions as a column spacer, and therefore an arrangement of the transmissive region (region A) is determined according to the arrangement of the column spacer to be finally formed in the mask 200. The mask 200 as configured above may be manufactured using the method for forming a predetermined thin thickness of a chromium pattern on a quartz substrate having almost 100 % transmittance, the chromium pattern being able to control the transmittance (see Korean Patent Publication No. 1996-182); the method for depositing molybdenum siliside onto a quartz substrate (see Korean Patent Registration No. 10-372579); etc. Accordingly, the term "transmitting all incident ultraviolet rays" used in the present invention is referred to as a meaning that the mask 200 has a UV transmittance of 100 % or a transmittance near to 100 %.

[39] Subsequently, a region of the photoresist film exposed through the transflective region (region B) of the mask 200 to be maintained at some portion of the predetermined height is formed into a color filter overcoat (region C); and a region of the photoresist film exposed through the transmissive region (region A) of the mask 200 to be maintained at all of the predetermined height is formed into a column spacer (region D) by developing the exposed photoresist film 121 (S3). As described above, the region of the photoresist film exposed through the transmissive region (region A) is completely cured, and therefore it functions as the column spacer (region D) since it is not affected upon its development and it is maintained intact at all of the predetermined height. Meanwhile, the region of the photoresist film exposed through the transflective region (region B) of the mask 200 is not completely cure but partially cured, and therefore the region of the photoresist film exposed through the transflective region (region B) is developed by a developer, especially partially developed to the extent that it is maintained at some portion of the predetermined height so that it can function as the color filter overcoat (region C). The region of the photoresist film exposed through the transflective region (region B) of the mask 200 has a reduced sensitivity to the developer since it is partially cured, and therefore it is easy to maintain the region of the photoresist film at a desired height by controlling a developing time and a surface of the film also has a good flatness. The thickness (a) of the formed color filter overcoat (region C) and the height difference (b) between the color filter overcoat (region C) and the column spacer (region D) may be varied according to the developing time, for example controlled at a thickness of 0.5 to 3.0 D and a height difference of 2.0 to 4.0 D, respectively.

[40] Meanwhile, the present invention provides a negative photoresist composition including a binder resin, a polymeric compound having an ethylenically unsaturated bond, a photoinitiator and a solvent, wherein the photoinitiator includes at least one phosphine oxide photoinitiator selected from the group consisting of compounds represented by the following Chemistry Figure 1, Chemistry Figure 2 and Chemistry Figure 3. This negative photoresist composition may increase a height difference between a color filter overcoat and a column spacer and accomplish its flat surface when it is applied to the method for simultaneously forming a color filter overcoat and a column spacer.

[41] <Chemistry Figure 1> [42]

O

A

R P-B

O

[43] <Chemistry Figure 2> [44]

[45] <Chemistry Figure 3> [46]

[47] wherein, R , R , R , R , R and R are independently hydrogen, or at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms (for example, an ethyl group, an ethyl group, an n-propyl group, an isopropyl group, an n- butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, etc.), a cyclic alkyl group, aromatic hydrocarbon, halogen, amine and amide,

[48] R is at least one selected from the group consisting of an alkyl group having 1 to

12 carbon atoms, alkenyl and aromatic hydrocarbon (for example, a benzene group, a phenylethyl group, etc.), and

[49] A and B are independently at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms (for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, etc.), a cyclic alkyl group, aromatic hydrocarbon, halogen, amine, amide and an oxyalkyl group.

[50] As known previously, the negative photoresist composition used for forming a color filter overcoat or a column spacer includes a binder resin, a polymeric compound having an ethylenically unsaturated bond, a photoinitiator and a solvent. An ace- tophenone or benzophenone photoinitiator is generally used as the photoinitiator.

[51] The present inventors found that the height difference between the color filter overcoat and the column spacer may be further increased, the more flat surface may be accomplished and a pattern of the column spacer may be more easily controlled when it is applied to the method for simultaneously forming a color filter overcoat and a column spacer using at least one phosphine oxide photoinitiator selected from the group consisting of the above compounds represented by Chemistry Figure 1, Chemistry Figure 2 and Chemistry Figure 3 as the photoinitiator alone or in combinations with a different kind of photoinitiators than when it is applied to the method using the conventional acetophenone or benzophenone photoinitiator.

[52] A specific example of the phosphine oxide photoinitiator as decribed above includes, but is not limited to, arylphosphine oxide, acylphosphine oxide, bisacylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-diethylbenzoyldiphenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,3,5, 6-tetramethylbenzoyldiphenylphosphine oxide, benzoyldi- (2,6-dimethylphenyl)phosphonate, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, etc.

[53] The photoinitiator has colors by itself and function to reduced its transparency, and therefore a high transparency may be accomplished by using a photoinitiator having a suitable sensitivity at a wavelength used upon the exposure and having no color by itself. Generally, a photoinitiator is used depending on the used wavelength of the ul- traviolet rays in the cross-linking reaction using an acrylic multifunctional monomer, and a mercury lamp having the most widely used UV wavelength has a wavelength range of 310 ~ 420 D, and therefore it uses a photoinitiator that forms a radical in the wavelength range.

[54] Also, the photoinitiator capable of being used in combinations with the phosphine oxide photoinitiator includes photoinitiators selected from the group consisting of, but is not limited to, a carbonyl compound, a dicarbonyl compound, acetophenone, ben- zoisophenone, an aminocarbonyl compound, triazine, oxime derivatives, etc., for example benzophenone, phenylbiphenylketone, 1 -hydroxy- 1-benzoy Icy clohexane, benzyldimethylketal, 1 -benzyl- 1 -dimethylamino- 1 - (4-morpholino-benzoyl)propane, 2-morpholyl-2-(4-methylmercapto)benzoylpropane, ethylantraquinone, 4-benzoyl-4-methyldiphenylsulfide, benzoinbutylether, 2-hydroxy-2-benzoylpropane, 2-hydroxy-2-(4-isopropyl)benzoylpropane, 4-butylbenzoyltrichloromethane, 4-phenoxybenzoyldichloromethane, benzoyl methylformate, l,7-bis(9-acridinyl)heptane, 9-n-butyl-3,6-bis(2-morpholino-isobutyloyl)carbazole, diphenyl(2,4,6-trimethylbenzoyl)-phosphineoxide, lO-butyl-2-chloroacrydone, 4,4'-bis(diethylamino)-benzophenone, 2-[2-(4-methoxy-phenyl)-vinyl] - 4,6-bis-trichloromethyl-[l,3,5]triazine,

2-(4-methoxy-naphthalen-l-yl)-4,6-bis-trichloromethyl-[l,3,5]triazine, 2-bezo[l,3] dioxol-5-yl-4,6-bis-trichloromethyl-[l,3,5]triazine, 2-methyl-4,6-bis(trichloromethyl)-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-naphthyl-4,6-bis(trichloromethyl)-s-triazine, etc.

[55] The polymerization photoinitiator is often used in combinations with a co- photoinitiator, and the co-photoinitiator functions to help the photoinitiator to enhance sensitivity of a photoresist. The co-photoinitiator includes amines, alkoxyanthracenes, thioxanthones, etc. The amines includes, is not limited to, triethanolamine, methyldiethanolamine, triisopropylamine, 4-dimethylaminomethyl benzoate, 4-dimethylaminoethyl benzoate, 4-methylaminoisoamyl benzoate, benzoate 2-methylaminoethyl, 4-dimethylamino-2-ethylhexyl benzoate, N, N - methylparatoluidine, 4,4'-bis(dimethylamino)benzophenone,

4,4'-bis(diethylamino)benzophenone, 4,4'-bis(ethylmethylamino)benzophenone, etc.; the alkoxyanthracenes includes, is not limited to, 9,10-dimethoxyanthracene, 2-ethyl-9, 10-dimethoxy anthracene, 9, 10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, 2-ethyl-9, 10-diethoxyanthracene, etc.; and the thioxanthones includes, is not limited to, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-trichlorothioxanthone, 1 -chloro-4-propoxythioxanthone, etc. [56] In the negative photoresist composition of the present invention, the photoinitiator may be added at a generally used content, for example at a content of 0.1 to 10 % by weight on the basis of the total weight of the composition, for example the phosphine oxide photoinitiator may be added at a content of 0.5 to 5 % by weight on the basis of the total weight of the negative photoresist composition. The co-photoinitiator may be added, for example at a content of 0.01 to 2 % by weight on the basis of the total weight of the composition.

[57] In the negative resist composition of the present invention, the known binder resin used in the negative resist composition may be used as the binder resin, but it is preferred to use a resin represented by the following Chemistry Figure 4 as the binder resin.

[58] <Chemistry Figure 4> [59]

[60] wherein a, b, c, d and e are independently mole ratios of the monomers, wherein 0<a<l, 0<b<l, 0<c<l, 0<d<l, and 0<e<l, provided that 0<a+b+c+d<l, and a+b+c+d+e=l,

[61] X is independently hydrogen or an alkyl group having 1 to 5 carbon atoms (for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n- butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, etc.),

[62] Y , Y and Y are independently at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxy alkyl group, an epoxy group, a benzene group, a phenylethyl group, an alkyl group containing amine, amide, carbamate or urea, and an alkenyl group,

[63] Y is aromatic hydrocarbon (for example, a phenyl group, a naphthyl group, etc.), [64] Z is at least one selected from the group consisting of an alkyl group having 1 to 24 carbon atoms, a cyclic alkyl group and aromatic hydrocarbon (for example, a benzene group, a phenylethyl group, etc.),

[65] n is an integer from 1 to 12, and [66] k is an integer from 0 to 6. [67] The binder resin represented by Chemistry Figure 4 is a copolymer of a monomer containing carboxylic acid and a radical polymeric compound, and the photoresist film has a constant height difference between a color filter overcoat and a column spacer, no defect and a very excellent flatness after its development when it is coated with the composition of the present invention containing the copolymer to form a predetermined pattern. That is to say, Y , Y and Y in the Chemistry Figure 1 are independently an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxy alkyl group, an epoxy group, a benzene group, a phenylethyl group, an alkyl group including amine, amide, carbamate or urea, or alkenyl, and may control a shape of a pattern and enhance an adhesive force, as well as increase a chemical resistance. Unlike the conventional binder resins made of an acryl copolymer resin containing an aromatic group, the binder resin Y enhances a remaining possibility since it has a bulky substituent structure, as well as has an excellent thermal resistance because of its high glass transition temperature and gives a chemical resistance and a high transparency. Meanwhile, the binder resin has an enhanced curing degree and an improved developing property since it has shapes of various structures including carbonate and a long chain-like carboxylic acid in its main chain. The binder resin has an improved adhesive property to a glass surface or a color filter and an enhanced brittle resistance of the pattern, as well as no whitening phenomenon if compatibility is increased between the resin represented by Chemistry Figure 4 and the polymeric compound having an ethylenically unsaturated bond.

[68] It is preferred to use the binder resin represented by Chemistry Figure 4 preferably having an average molecular weight of 2,000 to 50,000, a polydispensity of 1.0 to 5.0, and an acidity of 30 to 400 KOHD/g, and the most preferred to use the binder resin having an average molecular weight of 5,000 to 40,000, a polydispensity of 1.6 to 3.0, and an acidity of 50 to 150 KOHD/g.

[69] In the negative photoresist composition of the present invention, the binder resin may be added at a generally used content, for example at a content of 5 to 30 % by weight on the basis of the total weight of the composition.

[70] One example of the polymeric compound having an ethylenically unsaturated bond, included in the negative photoresist composition of the present invention, may include, but is not limited to, compounds obtained by esterifying a polyvalent alcohol and a α,β-unsaturated carboxylic acid, the polyvalent alcohol being selected from the group consisting of ethyleneglycoldi(meth)acrylate, polyethyleneglycoldi(meth)acrylate having 2 to 14 ethyleneoxide groups, trimethylolpropanedi(meth)acrylate, trimethylol- propanetri(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaery- thritoltetra(meth)acrylate, propyleneglycoldi(meth)acrylate having 2 to 14 propy- leneoxide groups, dipentaerythritolpenta(meth)acrylate, dipentaery- thritolhexa(meth)acrylate, etc.; compounsd obtained by adding (meth)acrylic acid to glycidyl group-containing compounds such as trimethylolpropanetriglycidylether acrylic acid additives, bisphenol A diglycidylether acrylic acid additives, etc.; ester compounds of compounds having a hydroxy group (for example, phthalate diesters of β-hydroxyethyl(meth)acrylate, toluene diisocyanate additives of β-hy- droxyethyl(meth)acrylate, etc.) and an ethylenically unsaturated bond with polyvalent carboxylic acid, or additives with polyisocyanate; (meth)acrylic acid alkylester such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, etc.; additionally known polymeric compounds having an ethylenically unsaturated bond selected from the group consisting of ditrimethylol- propanetetraacrylate, tris(2-acryloxyethyl)isocyanurate, ethoxylated pentaerythritolte- traacrylate (EO 4 mol), pentaerythritoltetraacrylate (EO 35 mol), ethoxylated trimethy- lolpropanetriacrylate (EO 9 mol), ethoxylated trimethylolpropanetriacrylate (EO 3 ,mol), propxylated pentaerythritoltetraacrylate (PO 4 mol), nonaethylenegly- coldiacrylate, dipentaerythritolhexaacrylate-modified caprolactone, trimethylol- propanepropoxylate triacrylate, etc. They are also used alone or in combinations thereof. The polymeric compound having an ethylenically unsaturated bond may be added at a generally used content, for example at a content of 5 to 35 % by weight on the basis of the total weight of the composition.

[71] Meanwhile, generally used solvents may be used as the solvent added to the negative photoresist composition of the present invention, and diethylenegly- coldimethylether (DMC), diethyleneglycolmethylethylether (MEC), methyl- methoxypropionate, ethylethoxypropionate (EEP), ethyllactate, propyleneglycol- methyletheracetate (PGMEA), propyleneglycolmethylether, propyleneglycol- propylether, methylcellosolveacetate, ethylcellosolveacetate, diethyleneglycol- methylacetate, diethyleneglycolethylacetate, methylisobutylketone, cyclohexanone, dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N- methyl-2-pyrrolidone (NMP), γ-butylolactone, diglyme, methylcellosolve, ethyl- cellosolve, diethyleneglycolmethylether, diethyleneglycolethylether, dipropylenegly- colmethylether, etc. are preferably used alone or in combinations thereof when considering compatibility with a binder resin, a polymeric compound having an ethylenically unsaturated bond, and a polymerization photoinitiator.

[72] Especially, a height difference between a color filter overcoat and a column spacer may be maximized when the composition including an alkyl acetate solvent represented by the following Chemistry Figure 5 as the solvent is applied to the method for simultaneously forming a color filter overcoat and a column spacer.

[73] <Chemistry Figure 5>

[74] 0

Λ^- 8

Q-

[75] wherein, R is an alkyl group having 1 to 12 carbon atoms (for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, etc.).

[76] In the negative photoresist composition of the present invention, the solvent is preferably added so that the composition can have a viscosity of 3 to 35 cps, and more preferably a viscosity of 5 to 25 cps. It is desirable to control the viscosity of the composition to the range so as to manufacture a coating layer that has no pin hole in the thin film and may maintain a suitable thickness of a cell gap after its coating.

[77] A silicon compound containing an epoxy group or an amine group may be further added to the negative photoresist composition of the present invention. An adhesive force between the color filter and the composition and a thermal resistant property after curing are improved when the silicon compound containing an epoxy group or an amine group is added to the composition. This silicon compound includes (3-glycidoxypropyl)trimethoxy (ethoxy)silane,

(3-glycidoxypropyl)methyldimethoxy(ethoxy)silane, (3-glycidoxypropyl) dimethylmethoxy(ethoxy)silane, 3,4-epoxybutyltrimethoxy(ethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxy(ethoxy)silane, N - (2- aminoethyl) - 3 -aminopropyldimethoxymethylsilane, (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane, (N,N-diethyl-3-aminopropyl)trimethoxysilane, N - beta(aminoethyl) gamma-aminopropyltrimethoxysilane, etc., and they may be used alone or in combinations thereof. A preferable amount of the added silicon compound containing an epoxy group or an amine group ranges from 0.001 to 0.1 % by weight on the basis of the total weight of the composition when the silicon compound is added to the composition.

[78] It should be understood that additives having compatability with the composition of the present invention, for example a photosensitizer, a thermal polymerization inhibitor, a defoamer, a leveling agent, etc. may be added to the negative photoresist composition of the present invention within the spirit and the scope of the present invention without adversely affecting the objects of the present invention, if necessary. Mode for the Invention

[79] Hereinafter, preferable embodiments of the present invention may be variously modified and changed for the purpose of illustrations in detail only. However, it should be understood that the description proposed herein is just a preferable example, not intended to limit the scope of the invention. So, it should be understood that preferable embodiments of the present invention is provided for a more complete description of the present invention, as apparent to those skilled in the art from this detailed description.

[80] <Examples 1 through 20>

[81] A negative photoresist composition was prepared using compositions and contents of the following compounds except that compositions and contents of a binder resin, a photoinitiator and a solvent were varied as listed in the following Table 1.

[82] Acryl binder resin of Chemistry Figure 4: 20%

[83] Dipentaerythritolhexaacrylate (DPHA): 20%

[84] 3-glycidyloxypropyltrimethoxysilane (A- 187): 0.05%

[85] Photoinitiator: as listed Table 1

[86] Solvent: the balance

[87] <Preparation of Resin represented by Chemistry Figure 4>

[88] The resin of Chemistry Figure 4 was synthesized, as follows.

[89] Synthesis of Chemistry Figure 4a

[90] As monomers, 82.8 g of ethylmethacrylate, 143.2 g of benzylmethacrylate, 82.5 g of glycidylmethacrylate and 67.5 g of methacrylic acid were added to a bath, and a mixture of 8.1 g of 2,2-azobis(2,4-dimethylvaleronitrile) and 610 g of diethylenegly- colmethylethylether was also added to the bath, and then the resultant mixture was stirred at 60 ⁰C for 5 hours under a nitrogen environment and cooled to obtain 1,000 g of a resin of Chemistry Figure 4a.

[91] The resultant resin has an average molecular weight of 15,00, a polydispensity of

2.4, an acidity of 115, and a solid content of 37.5 %.

[92] Synthesis of Chemistry Figure 4b

[93] As monomers, 23.5 g of methylmethacrylate, 150.4 g of dicyclopentanyl- methacrylate, 116.7 g of glycidylmethacrylate, 22.8 g of stylene and 62.8 g of methacrylic acid were added to a bath, and a mixture of 8.0 g of 2,2-azobis(2,4-dimethylvaleronitrile) and 61O g of diethyleneglycolmethylethylether was also added to the bath, and then the resultant mixture was stirred at 60 ⁰C for 5 hours under a nitrogen environment and cooled to obtain 1,000 g of a resin of Chemistry Figure 4b.

[94] The resultant resin has an average molecular weight of 17,00, a polydispensity of

2.4, an acidity of 109.5, and a solid content of 37.2 %.

[95] Synthesis of Chemistry Figure 4c

[96] As monomers, 205.4 g of ethylmethacrylate, 59.0 g of glycidylmethacrylate and

72.1 g of 2-hydroxy ethylmethacrylate were added to a bath, and a mixture of 13.4 g of azobisisobutyronitrile and 650 g of diethyleneglycolmethylethylether was also added to the bath, and then the resultant mixture was stirred at 80 ⁰C for 5 hours under a nitrogen environment and cooled to obtain 1,000 g of a copolymer.

[97] 7.98 g of trimellitic anhydride was added to 100 g of an aliquot of the solution, and

0.06 g of dimethylaminopyridine was also added thereto, and then stirred at 50 °C for 5 hours to obtain a desired resin of Chemistry Figure 4c.

[98] The resultant resin has an average molecular weight of 14,000, a polydispensity of

2.4, an acidity of 115, and a solid content of 38.1 %.

[99] Synthesis of Chemistry Figure 4d

[100] As monomers, 189.3 g of ethylmethacrylate, 39.3 g of glycidylmethacrylate and

107.9 g of 2-hydroxyethylmethacrylate were added to a bath, and a mixture of 13.4 g of azobisisobutyronitrile and 650 g of diethyleneglycolmethylethylether was also added to the bath, and then the resultant mixture was stirred at 80 ⁰C for 5 hours under a nitrogen environment and cooled to obtain 1,000 g of a copolymer.

[101] 8.41 g of tetrahydrophthalic anhydride was added to 100 g of an aliquot of the solution, and 0.06 g of dimethylaminopyridine was also added thereto, and then stirred at 50 ⁰C for 5 hours to obtain a desired resin of Chemistry Figure 4d.

[102] The resultant resin has an average molecular weight of 16,000, a polydispensity of

2.4, an acidity of 90, and a solid content 39.5 %.

[103] Other methods for preparing resins of Chemistry Figure 4 are omitted since they may be easily deduced from the method as described above.

[104] Table 1

[105] [106] In the Table 1, TPO represents 2,4,6-trimethylbenzoyldiphenylphosphine oxide; DTEX represents diethylthioxantone; 1-369 represents

2-benzyl-2-dimethylamino- 1 -(4-morpholinophenyl)-butan- 1 -on; I- 184 represents 1 -hydroxy cyclohexyl phenyl ketone; 1-907 represents

2-methyl-l-[4-(methylthio)phenyl]-2-morpholinopropan-l-on; MEDG represents di- ethyleneglycolmethylethylether; PGMEA represents propyleneglycolethyletheracetate; and NBA represents Normal butylacetate.

[107] <Preparative examples> [108] Each of the above-mentioned negative photoresist compositions of Examples 1 to 20 was coated onto a substrate at a rotary rate of 650 rpm for 13 seconds using a spin coater and pre-baked at 90 ⁰C for 3 minutes, and then exposed for 10 seconds at 365 D wavelength and developed for 70 seconds with a developer, and then post-baked at 220 ⁰C for 30 minutes to form final resist films, respectively.

[109] A mask in which a chromium pattern having a UV transmittance of 15 % was formed on a quartz substrate was used as the mask used in the exposure.

[HO] The prepared resist films were measured for a performance test according to the following standard, and the results are listed in the following Table 2.

[111] (1) Thickness of Color filter overcoat [112] Thickness of the color filter overcoats was measured by observing a single surface of the resist films formed according the preparative examples as described above, using an electron microscope.

[113] (2) Height difference between Color filter overcoat and Column spacer [114] Height differences between the color filter overcoats and the column spacers were measured by cutting central regions of the column spacer patterns of the resist films at a vertical direction and observing the patterns at a direction of their cut surfaces using an electron microscope.

[115] (3) Flatness

[116] Flatness of the resist films was determined by measuring their thickness in 25 different sites of the resist films, followed by calculating differences between their largest thickness and their smallest thickness using a thickness gauge.

[117] (4) Close adhesivity

[118] The resist films were cross-cut, and their close adhesivity was tested by peeling the films with an adhesive tape. A resist film is proved to be "Good" if it is remained at a level of more than 98 %, but "Not good" if it is not remained at a level of more than 98 %.

[119] (5) Transmittance

[120] Each of the above-mentioned negative photoresist compositions of Examples 1 to

20 was coated onto a substrate at a rotary rate of 750 rpm for 13 seconds using a spin coater and pre-baked at 90 ⁰C for 3 minutes, and then exposed for 10 seconds at 365 D wavelength(using the same mask as in the preparative examples), post-baked at 220 ⁰C for 30 minutes to form final resist films, and then their transmittance was measured using a UV transmittance measurement system. A resist film is proved to be "Good" if its transmittance is at a level of more than 98 % at 380 D wavelength, but "Not good" if its transmittance is not at a level of more than 98 % at 380 D wavelength.

[121] Table 2

[122] As shown in the results of Table 2, it was revealed that the negative photoresist composition of the present invention increases a height difference of the column spacer and accomplishes its flat surface, as well as has excellent physical properties such as close adhesivity, transmittance, etc. when it is applied to the method for simultaneously forming a color filter overcoat and a column spacer of a liquid crystal display (LCD). Industrial Applicability

[123] As described above, a thickness of the color filter overcoat and a height difference between the color filter overcoat and the column spacer may be constantly maintained and its surface may be formed with a satisfactory flatness since the color filter overcoat and the column spacer having a good shape and height difference may be simultaneously and easily formed on the color filter substrate according to the method for simultaneously forming a color filter overcoat and a column spacer of a liquid crystal display of the present invention. Accordingly, a large amount of time and cost may be reduced, and therefore its productivity may be significantly improved since the method of the present invention gives functions of protecting a color filter and preventing the contamination of a liquid crystal and a function of the color filter capable of maintaining a constant cell gap even in the one-step process regardless of the size of a liquid crystal display.

[124] Also, the negative resist composition of the present invention may be useful to increase a height difference of a column spacer and accomplish its flat surface when it is applied to the above-mentioned method.

Claims

[1] A method for simultaneously forming a color filter overcoat and a column spacer of LCD, the method comprising:

(51) forming a photoresist film by applying a negative photoresist composition at a predetermined height onto a substrate of a liquid crystal display in which a black matrix and a color filter are formed;

(52) exposing the photoresist film through a mask composed of a transflective region transmitting only some of incident ultraviolet rays and whose position is set to correspond to the color filter; and a transmissive region transmitting all incident ultraviolet rays and whose position is set to correspond to the black matrix; and

(53) forming a region of the photoresist film, exposed through the transflective region of the mask to be maintained at some portion of the predetermined height, into a color filter overcoat; and a region of the photoresist film, exposed through the transmissive region of the mask to be maintained at all of the predetermined height, into a column spacer, by developing the exposed photoresist film.

[2] The method for simultaneously forming a color filter overcoat and a column spacer of LCD according to claim 1, wherein the transflective region of the mask has a UV transmittance of 5 to 80 %.

[3] The method for simultaneously forming a color filter overcoat and a column spacer of LCD according to claim 1, wherein the color filter overcoat has a thickness of 0.5 to 3.0 D and a height difference between the color filter overcoat and the column spacer ranges from of 2.0 to 4.0 D.

[4] A negative photoresist composition comprising a binder resin, a polymeric compound having an ethylenically unsaturated bond, a photoinitiator and a solvent, wherein the photoinitiator includes at least one phosphine oxide photoinitiator selected from the group consisting of compounds represented by the following Chemistry Figures 1, 2 and 3; <Chemistry Figure 1>

0

A

R¹-^- P I l -B

O <Chemistry Figure 2>

wherein R , R , R , R , R and R are independently hydrogen or at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, a cyclic alkyl group, aromatic hydrocarbon, halogen, amine and amide, R is at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, alkenyl and aromatic hydrocarbon, and A and B are independently at least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, a cyclic alkyl group, aromatic hydrocarbon, halogen, amine, amide and an oxyalkyl group.

[5] The negative photoresist composition according to claim 4, wherein the binder resin is a resin represented by the following Chemistry Figure 4; <Chemistry Figure 4>

wherein a, b, c, d and e are independently mole ratios of the monomers, wherein 0<a<l, 0<b<l, 0<c<l, 0<d<l, and 0<e<l, provided that 0<a+b+c+d<l, and a+b+c+d+e=l,

X is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, Y , Y and Y are independently at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, a hydroxy alkyl group, an epoxy group, a benzene group, a phenylethyl group, an alkyl group containing amine, amide, carbamate or urea, and an alkenyl group, Y⁴ is aromatic hydrocarbon,

Z is at least one selected from the group consisting of an alkyl group having 1 to

24 carbon atoms, a cyclic alkyl group and aromatic hydrocarbon, n is an integer from 1 to 12, and k is an integer from 0 to 6. [6] The negative photoresist composition according to claim 4 or 5, wherein a content of the phosphine oxide photoinitiator ranges from 0.5 to 5 % by weight, based on the total weight of the composition. [7] The negative photoresist composition according to claim 4 or 5, wherein the solvent includes an alkyl acetate solvent represented by the following Chemistry

Figure 5;

wherein R is an alkyl group having 1 o 12 carbon atoms. [8] The negative photoresist composition according to claim 4 or 5, further comprising 0.001 to 0.1 % by weight of a silicon compound containing an epoxy group or an amine group. [9] The negative photoresist composition according to claim 4 or 5, wherein the solvent is added to the composition until its viscosity reaches 3 to 35 cps.