[DESCRIPTION]

[Invention Title]

COLOR FILTER AND METHOD FOR MANUFACTURING THEREOF

[Technical Field]

The present invention relates to a method of manufacturing a color filter and a color filter

manufactured by using the same. More particularly, the present invention pertains to a method

of manufacturing a color filter, in which an ink affinity property of a pixel unit is maintained

while a process and complicated surface treatment for forming a separate ink affinity layer are

not performed in order to reduce a cost during manufacturing of the color filter by using inkjet,

and a color filter manufactured by using the same.

This application claims priority from Korean Patent Application No. 10-2007-0011022

filed on February 2, 2007 in the KIPO, the disclosure of which is incorporated herein by

reference in its entirety.

[Background Art]

In general, fine patterns which are used in display devices such as semiconductor circuit

devices and LCDs (Liquid Crystal Display) are formed according to a photolithography process

by using a photoresist. In connection with this, the photoresist is applied on the substrate,

exposed, developed, washed, and cured to produce the fine pattern. Even though the

photolithography process is advantageous in that desired patterns are precisely obtained, there

are disadvantages in that many steps are performed, various types of materials are used in order

to maximize the effect of the photoresist, and a great amount of photoresist is used during

processes such as a coating process. In recent, a method for obtaining a fine pattern by using an

inkjet printing process has been suggested in order to avoid the disadvantages of the

photolithography process.

With respect to the production of the color filter by using the inkjet printing process, a

BM (black matrix) which is a light blocking part is formed by using a known photolithography

process, and three types of ink having R, G, and B colors are jetted into pixel units between the

light blocking parts used as partitions. A manufacturing method of a color filter by using the

inkjet printing is shown in FIG. 1. In connection with this, if the light blocking part used as the

partition does not have the ink repellency in respects to the ink, the ink which is jetted into the

pixel units between the light blocking parts flows through the light blocking part from the pixel

unit to the adjacent pixel unit, which may cause color mixing in respects to the same color or the

different colors. Therefore, it is required that the light blocking part pattern which is used as

the partition during the inkjet printing has the significantly high ink repellency in respects to the

ink.

On the other hand, the jetted ink is uniformly spread in the pixel units only when the

surface of the glass substrate of the pixel units between the light blocking parts has the low ink

repellency in respects to the ink, which prevents light leakage due to unfilling of the pixel units

and reduces steps in the pixel unit or between the pixel units. However, if the light blocking

part pattern is made of a light blocking part material having the high ink repellency, due to the

post-baking process, the surface of the glass substrate of each of the pixel units is reformed so

that the surface of each of the pixel units has the ink repellency similar to that of the surface of

the light blocking part. Accordingly, even though the ink is jetted, the ink is undesirably spread

in each of the pixel units to cause the unfilling and significant steps in the pixel unit or between

the pixel units. The light blocking part and the pixel unit that are formed by using the above

light blocking part pattern are shown in FIG. 2, and unfilling of ink due to the material having

the ink repellency adsorbed on the pixel unit is shown in FIG. 3.

In order to avoid the above-mentioned problems, Japanese Unexamined Patent

Application Publication No. 1997-203803 discloses a method of performing surface treatment in

respects to a main unit by using an ink affinity treatment agent and surface treatment in respects

to a projection unit by using an ink repellency treatment agent. However, this method is

problematic in that the treatment is performed by using the ink affinity treatment agent so that

the ink repellency treatment agent is not affected or two treatment processes are separately

performed by using the ink affinity treatment agent and the ink repellency treatment agent.

Furthermore, Korean Unexamined Patent Application Publication No. 2000-0047958

discloses a color filter which has a wettability- variable layer capable of changing the wettability.

However, this method is disadvantageous in that the wettability-variable layer is separately

provided in addition to a partition layer which is a light blocking part and an ink layer which is

an opening part, thus complicating the production process.

Additionally, Japanese Unexamined Patent Application Publication No. 2000-258622

discloses a method of pattern exposing a photosensitive layer to convert an exposed portion into

a hydrophilic portion. However, in this method, it is required that an additional process is

performed to form an additional photosensitive layer.

[Disclosure]

[Technical Problem]

It is an object of the present invention to provide a method of manufacturing a color filter

in which color mixing does not occur in a pixel unit or between pixel units, discoloration due to

unfilling does not occur, a surface is uniform, and there is an insignificant step in the pixel unit

or between the pixel units by maintaining a hydrophilic property of the pixel unit defined by a

light blocking part while an ink repellency property of the light blocking part used as a partition

is maintained to improve the spreadability of ink in the pixel unit during manufacturing of the

color filter by using an inkjet process, and a color filter manufactured by using the method.

[Technical Solution]

In order to accomplish the above object, the present invention provides a method of

manufacturing a color filter that includes a) applying a light blocking part material on a

substrate; b) prebaking the light blocking part material to form a light blocking layer; c)

selectively exposing and developing the light blocking layer to form a light blocking part pattern;

d) precuring the light blocking part pattern; e) applying a solution on the substrate on which the

light blocking part pattern is formed; f) postbaking the light blocking part and the solution; and

g) filling ink in a pixel unit that is defined by the light blocking part pattern.

In addition, the present invention provides a color filter that is manufactured by using the

above manufacturing method.

In addition, the present invention provides a display device that includes the above color

filter.

[Advantageous Effects]

In the present invention, during manufacturing of a color filter by using an inkjet printing

process, a hydrophilic property of the pixel unit between light blocking part patterns is

maintained while an ink repellency property of the light blocking part used as a partition is

maintained to improve the spreadability of ink in the pixel unit. Thus, it is possible to

manufacture a color filter in which color mixing does not occur in the pixel unit or between pixel

units, discoloration due to unfilling does not occur, a surface is uniform, and there is an

insignificant step in the pixel unit or between the pixel units.

[Description of Drawings]

FIG. 1 is a view that illustrates a procedure of manufacturing a color filter by using inkjet

printing;

FIG. 2 is a cross sectional view of a patterned substrate;

FIG. 3 is a CCD (Charge-Coupled Device) camera picture ( ^χ 50) that illustrates unfilling

of ink due to a material having the ink repellency adsorbed on a pixel unit;

FIG. 4 is a view that illustrates volatilization of the material having the ink repellency of

a light blocking part during a postbake process;

FIG. 5 is a schematic flow chart that illustrates a process of the present invention;

FIG. 6 is a view that illustrates volatilization of the material having the ink repellency of

the light blocking part during the postbake process after a solution is applied;

FIGS. 7 to 9 are CCD camera pictures ( ^χ 50) that illustrate the pixel unit uniformly filled

with ink according to Examples 1 to 3 of the present invention; and

FIGS. 10 to 12 are CCD camera pictures ( ^χ 50) that illustrate unfilling of ink in the pixel

unit according to Comparative Examples 1 to 3 of the present invention.

[Best Mode]

Hereinafter, the present invention will be described in detail.

A method of manufacturing a color filter according to the present invention includes a)

applying a light blocking part material on a substrate; b) prebaking the light blocking part

material to form a light blocking layer; c) selectively exposing and developing the light blocking

layer to form a light blocking part pattern; d) precuring the light blocking part pattern; e)

applying a solution on the substrate on which the light blocking part pattern is formed; f)

postbaking the light blocking part and the solution; and g) filling a pixel unit that is defined by

the light blocking part pattern by using ink.

Specifically, during the process of manufacturing the color filter, when an inkjet process

is used, in the case of when the above light blocking part pattern that acts as a partition is formed

by using a known photolithography process, the light blocking part material having the ink

repellency property is applied on the substrate, and subjected to prebaking, UV exposure,

development, and postbaking processes. In particular, during the postbaking process in which

the light blocking part material is cured by using heat treatment at high temperatures, the

component having the ink repellency property of the light blocking part affects the pixel unit,

which enables the pixel unit having the ink affinity property to be reformed to have the ink

repellency property. It is deemed that the reformation is caused by the adsorption of the

material having the ink repellency property on the pixel unit that is disposed adjacent to the light

blocking part pattern in the course of volatilizing the material having the ink repellency property

of the light blocking part pattern at a high speed during the postbaking process when the light

blocking part pattern is produced. The volatillization of the material having the ink repellency

property of the above light blocking part pattern is shown in FIG. 4.

However, in the present invention, in order to prevent the pixel unit from having the ink

repellency property before the step of treating the light blocking part pattern by using the

postbaking process, the solution having the low volatility is coated on the substrate on which the

above light blocking part pattern is formed. In connection with this, in order to prevent the

partition of the light blocking part that is not cured from being dissolved due to the coated

solution, after the light blocking part is precured, the solution is coated. FIG. 5 is a schematic

flow chart that illustrates a process of the present invention.

The above step a is a step in which the light blocking part material is applied on the

substrate.

Examples of the substrate include, but are not limited to a glass substrate, a plastic

substrate, and a flexible substrate. It is preferable to use a transparent glass substrate having

high heat resistance.

The application of the light blocking part material on the above substrate may be

performed by using a process which is known in the art, for example, spin coating, dip coating,

doctor blading or the like.

It is preferable that the above light blocking part material have the ink repellency

property. In order to allow the above light blocking part material to have the ink repellency

property, it is preferable that the silicon or fluorine surfactant which is a component having the

ink repellency property is contained in an amount of 0.01 to 0.3 parts by weight based on 100

parts by weight of the light blocking part material. In addition, the above light blocking part

material may include 20 to 50 parts by weight of carbon black, an organic pigment mixture type

light blocking coloring agent, or a hybrid type coloring material containing carbon black and the

organic pigment mixture type light blocking coloring agent mixed with each other as a coloring

agent, 20 to 50 parts by weight of a binder polymer component, 10 to 40 parts by weight of a

crosslinking agent, and additives in respects to the total solid of the composition. Furthermore,

the above composition for forming the light blocking part may further include a solvent for a

coating property.

The above step b is a step in which the above light blocking part material is prebaked to

form the light blocking layer.

It is preferable that the prebaking be performed at 50 to 150 ^° C for 10 to 1000 sec.

The above step c is a step in which the light blocking layer is selectively exposed and

developed to form the light blocking part pattern.

The selective exposure and development may be performed by using a process which is

known in the art. For example, after the prebaked light blocking part material is selectively

exposed by using a photomask, an exposed portion or a non-exposed portion may be developed

to perform the prebaking.

It is preferable that the thickness of the manufactured light blocking part pattern be in the

range of 1.1 to 5 μm and an optical density thereof be in the range of 2 to 6 within the above

thickness range. Additionally, it is preferable that the above light blocking part pattern have a

contact angle in the range of 20 to 60° in respects to ink.

The above step d is a step in which the above light blocking part pattern is precured.

After the above precuring step, the above step d is performed in order to prevent the

uncured component of the light blocking part from being dissolved in the solution and thus being

modified in the course of applying the solution.

In the above precuring step, photocuring, heat curing, or both photocuring and heat

curing may be performed. In connection with this, it is preferable that the heat curing be

performed at 50 to 150°C for 10 to 1000 sec so that the component having the ink repellency

property does not affect the pixel unit. It is preferable that the above photocuring be performed

while UV is radiated in the intensity of 50 to 500 mW/αtf for 5 to 500 sec. In connection with

this, since a photosensitive resin is used as the light blocking part material in the present

invention, it is preferable that the precuring according to the present invention be performed by

using the photocuring.

The above step e is a step in which the solution is applied on the substrate on which the

above light blocking part pattern is formed.

The application of the above solution may be performed by using a typical entire surface

coating process such as spin coating, slit coating, or dip coating. Since the above light blocking

part pattern has the ink repellency property, when the solution is applied on the entire surface of

the light blocking part pattern, the solution flows down from the light blocking part even though

the solution is not subjected to a separate treatment process to be applied only on the pixel unit.

The solution is vertically volatilized in the course of volatilizing the material having the ink

repellency property of the light blocking part while the solution is applied on the pixel unit and

subjected to the postbaking process, which functions to prevent the material having the ink

repellency property of the light blocking part from affecting the pixel unit. Even though the

volatilization occurs horizontally, since the volatilization is diluted due to the coating solution,

the effect may be significantly reduced. FIG. 6 is a view that illustrates volatilization of the

material having the ink repellency of the light blocking part during the postbake process after the

solution is applied.

In connection with this, it is undesirable that the volatilization of the coated material first

occurs before the material having the ink repellency property of the light blocking part is

volatilized. Thus, it is preferable that the solution contain a material having the low volatility.

In addition, it is preferable that the solution have a boiling point in the range of 200 to 250 "C

which is similar to the temperature of the high temperature heat treatment so that the solution is

volatilized at the temperature of the postbaking process in the range of 200 to 250 ^° C without a

separate process. Furthermore, it is preferable that the solution be well mixed with ink to be

applied by using inkjet. In particular, it is preferable that the solution which is the same as the

solvent of the ink composition used during the inkjet process be used. This contributes to the

provision of the ink affinity property when ink is discharged in the case of when the coating

material remains on the pixel unit.

Specific examples of the above solution include butyl carbitol acetate (boiling point:

245 ^° C), diethyl ene glycol monoethyl ether acetate (boiling point: 217 ^" C), dipropyleneglycol

methyl ether acetate (boiling point: 209 ^° C) or the like.

The above step f is a step in which the above light blocking part and the solution are

subjected to the postbaking process.

The substrate on which the light blocking part pattern coated with the above solution is

formed is subjected to the postbaking process at 200 to 250 ^" C for 10 to 200 min. The solution

is vertically volatilized in the course of volatilizing the volatile material during the postbaking

process, which functions to prevent the volatile material from affecting the pixel unit. During

the above postbaking process, the solution which is applied in conjunction with the curing of the

light blocking part may be removed, the light blocking part may have the ink repellency property,

and the pixel unit may include the pattern having the ink affinity property that is the same as that

of the ink.

The above step g is a step in which a pixel unit defined by the above light blocking part

pattern is filled with ink.

The filling of ink may be performed by continuously using two types or more of ink, for

example, three types of ink having R, G, and B colors. The above ink may be photocurable ink

or heat curable ink. It is preferable that the filling of ink be performed by using an inkjet

process.

If the ink is discharged onto the pixel unit by using the inkjet process, since the light

blocking part pattern which is formed according to the method of the present invention has the

ink repellency property and the pixel unit has the ink affinity property, the discharged ink may be

uniformly dispersed in the pixel unit and applied so that the layer of ink is higher than the light

blocking part pattern.

During this process, since the discharged ink does not flow over the light blocking part

pattern having the ink repellency property, it is possible to continuously discharge the three types

of ink while a separate post treatment process is not performed, and the photocuring or the heat

curing may be performed in respects to ink after each ink is discharged or all types of ink is

discharged if necessary.

In the case of the photocurable ink, after each ink is discharged or all types of ink are

discharged, the exposure is performed in an exposure intensity of 40 to 300 mJ/cm , the high

temperature heat curing may be performed at the temperature in the range of 200 to 250 ^° C for 10

to 200 min. In the case of the heat curable ink, after each ink is discharged or all types of ink

are discharged, the low temperature heat curing may be performed at the temperature in the

range of 50 to 150 ^° C for 10 to 2000 sec, and the high temperature heat curing may be performed

at the temperature in the range of 200 to 250 ^° C for 10 to 200 min without an additional exposure

process. The above-mentioned procedure may be performed in respects to ink including the

heat curing type and the photocuring type mixed with each other.

The present invention provides a color filter that is manufactured by using the above

method.

In the manufactured color filter, an ink affinity property of the pixel unit is maintained

without a process of forming a separate ink affinity layer and a complicated surface treatment

process. Thus, during the filling, it is possible to manufacture a color filter in which color

mixing, discoloration, unfilling, and staining do not occur, and a surface is uniform.

Furthermore, a process is simplified, contributing to a reduction in cost.

The present invention provides a display device which includes the color filter.

The display device according to the present invention may have a configuration which is

known in the art, except that the display device includes the color filter according to the present

invention.

[Mode for Invention]

A better understanding of the present invention may be obtained in light of the following

Examples which are set forth to illustrate, but are not to be construed to limit the present

invention.

PREPARATION EXAMPLE 1 : Preparation of the light blocking material

Based on 1000 parts by weight of the photosensitive resin composition, 65 parts by

weight of carbon black used as the coloring agent, 29 parts by weight of the copolymer of

benzyl(metha)acrylate/(metha)acrylic acid (acid value 110 KOH mg/g, molar ratio 70/30, Mw =

30,000) used as the alkali-soluble resin binder, 70 parts by weight of the polymer in which

allylglycidyl ether was added to the copolymer of benzyl(metha)acrylate/(metha)acrylic acid

(acid value 80 KOH mg/g, Mw = 22,000), 50 parts by weight of dipentaerythritolhexaacrylate

used as the functional monomer, 20 parts by weight of

2-benzyl-2-(dimethylamino)-l-(4-morpholinophenyl)butyl-l- one used as the

photopolymerization initiator, 10 parts by weight of

2,2'-bis(o-chlorophenyl)-4,4,5,5'-tetraphenyl-l,2'-non-im idazole, 5 parts by weight of

4,4-bis(diethylamino)benzophenone, 5 parts by weight of mercaptobenzothiazole, 9 parts by

weight of the polyester dispersing agent used as the additive, 1 part by weight of the fluorine

surfactant used as the leveling agent for providing the ink repellency property, 440 parts by

weight of propylene glycol monomethyl ether acetate used as the solvent, and 290 parts by

weight of ethoxyethyl propionate were mixed with each other. Next, the mixture was agitated

for 5 hours to prepare the photosensitive resin composition.

PREPARATION EXAMPLE 2: Preparation of the heat curable ink

As to the R heat curable ink which was sprayed onto the pixel units by using the inkjet

process, 4.33 parts by weight of PIGMENT RED #254, 1.26 parts by weight of PIGMENT RED

#177, and 0.87 parts by weight of PIGMENT YELLOW #139, which were used as the coloring

agent, 3.77 parts by weight of the polymer (Mw = 24,000) used as the alkali-soluble resin binder,

in which ally! glycidyl ether was added to the copolymer containing benzyl(metha)acrylate and

(meta)acrylic acid mixed with each other at the molar ratio of 70:30, 7.54 parts by weight of

dipentaerythritolhexaacrylate used as the functional monomer, 0.5 parts by weight of the

azoamide heat-curing initiator (Vam-110, Wako Pure Chemical Industries., Ltd.), 2.29 parts by

weight of the polyester dispersing agent used as the additive, 1.0 parts by weight of

3-methacryloxypropyltrimethoxysilane, 0.04 parts by weight of the fluorine surfactant

(Megaface F-475, Japan Ink Chemical Industry Co., Ltd., Japan) used as the leveling agent, 64.7

parts by weight of butyl carbitol acetate used as the solvent, 6.22 parts by weight of propylene

glycol monomethyl ether acetate, 5.95 parts by weight of methoxy propanol, and 1.53 parts by

weight of butyl cellosolve acetate were mixed with each other, and the mixture was then agitated

for 5 hours to prepare the ink composition for inkjet.

EXAMPLES 1 to 3 and COMPARATIVE EXAMPLES 1 to 3: Preparation of the color

filter

EXAMPLE 1

The light blocking material which was prepared in the above Preparation Example 1 was

applied on the glass substrate by using spin coating, and subjected to a preheat treatment process

at about 100 ^° C for 2 min to form a film having a thickness of about 2.4 μm. Next, the film was

cooled at room temperature, and exposed for 1 min using energy of 100 mJ/cnf by means of a

photomask and a high-pressure mercury lamp. The exposed substrate was developed by using

the 0.04% KOH aqueous solution at a temperature of 25 "C according to the spray process,

washed with pure water, and dried by using air blowing. After the light blocking part pattern

was pre-cured at 100 "C for 2 min, butyl carbitol acetate (boiling point: 245 "C) was uniformly

applied on the formed glass substrate by using a dip coating process, and then subjected to a

postbaking process in the convection oven at 220 ^° C for 30 min to cure the light blocking part

pattern and to remove the coating solution.

FIG. 7 illustrates the heat curable ink which was prepared in the above Preparation

Example 2 discharged on the formed light blocking part pattern (20 drops).

EXAMPLE 2

The light blocking part pattern was formed by using the same method as that of the above

Example 1, except that the light blocking part pattern was not precured at 100 ^° C for 2 min but

subjected to a photocuring process by using UV energy of 100 mJ/cnf for 1 min to perform the

precuring.

FIG. 8 illustrates the heat curable ink which was prepared in the above Preparation

Example 2 discharged on the formed light blocking part pattern (20 drops).

EXAMPLE 3

The light blocking part pattern was formed by using the same method as that of the above

Example 1, except that the light blocking part pattern was not precured at 100 ⁰ C for 2 min but

subjected to a heat curing process at 100 ^° C for 2 min and to a photocuring process by using UV

energy of 100 mJ/αif for 1 min to perform the precuring.

FIG. 9 illustrates the heat curable ink which was prepared in the above Preparation

Example 2 discharged on the formed light blocking part pattern (35 drops).

COMPARATIVE EXAMPLE 1

The color filter was manufactured by using the same method as that of the above

Example 1 , except that the application of the solution was not performed during the process of

forming the light blocking part pattern.

FIG. 10 illustrates unfilling of ink after the heat curable ink was discharged.

COMPARATIVE EXAMPLE 2

The color filter was manufactured by using the same method as that of the above

Example 2, except that the application of the solution was not performed during the process of

forming the light blocking part pattern.

FIG. 11 illustrates unfilling of ink after the heat curable ink was discharged.

COMPARATIVE EXAMPLE 3

The color filter was manufactured by using the same method as that of the above

Example 3, except that the application of the solution was not performed during the process of

forming the light blocking part pattern.

FIG. 12 illustrates unfilling of ink after the heat curable ink was discharged.