JP4281930B2 - Manufacturing method of color filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a color filter having a color filter layer including a color pattern on a plastic film, and more particularly to a technology for manufacturing a color filter using transfer.
[0002]
BACKGROUND OF THE INVENTION
In general, a color filter used in a color liquid crystal display device is formed on a transparent glass substrate on, for example, primary colors red (R), green (G), blue (B), complementary colors yellow (Y), magenta ( M) and a color filter layer including a plurality of color patterns such as cyan (C). Such a basic structure of the color filter may be either a transmission type or a reflection type color filter, and may be produced by any method such as a printing method, a photolithography method, an electrodeposition method, or a transfer method. It is the same.
[0003]
Glass as a color filter substrate or substrate is excellent in terms of surface smoothness, light transmission, and other characteristics required for display. However, when glass is made thinner, it also has the disadvantage of being easily broken. Therefore, when used for display on portable devices that place importance on impact resistance and reduction in size and weight, the disadvantages of color filters using a glass substrate become conspicuous.
[0004]
In order to solve the problems caused by such a glass substrate, the inventors have attempted to develop a color filter using a plastic film as a substrate. This is because the plastic film is thin and has excellent impact resistance. However, while having such an advantage, the plastic film is inferior in heat resistance and chemical resistance, and in terms of expansion and contraction due to temperature and humidity, as compared with glass, and there is a problem that the manufacturing process of the color filter is restricted.
Therefore, Japanese Patent Application No. 10-225320 (application date: July 24, 1998), which is a prior application, proposed a color filter manufacturing technique using a transfer method in consideration of restrictions caused by a plastic film. . That is, a first step of forming a color filter layer including a color pattern on a substrate (for example, glass or the like) that is less heat stretchable than a plastic film, and after the first step, on the substrate of glass or the like And a second step of transferring the color filter layer onto the plastic film via the adhesive layer. According to such a technique, the chemicals used in the manufacturing process of the color filter layer are concentrated by concentrating the processing including the color patterns of a plurality of colors and requiring alignment with each other on the first process for the substrate such as glass. Restrictions such as heat treatment can be relaxed, and adverse effects due to the thermal stretchability of the plastic film (problems of reducing pattern accuracy and alignment accuracy) can be avoided. In the second step, the plurality of color patterns of the color filter layer are simultaneously transferred onto the plastic film, so that the high accuracy of the first step can be transferred to the plastic film side as it is.
[0005]
Problems to be Solved by the Invention
However, after further examination, when the color filter layer on the substrate such as glass is transferred to the plastic film side via the adhesive layer, the transfer time and the transfer end time (for example, the device including the color filter) It has been found that the temperature difference from the point of use may cause new problems. The temperature difference causes expansion and contraction of the plastic film, especially because the temperature at the time of transfer is higher than the temperature after transfer, the plastic film shrinks, and the color pattern on the plastic film is pulled according to the shrinkage, and the pattern itself Cause dimensional variation.
An object of the present invention is to make the temperature at the time of transfer as close as possible to the temperature at which the device including the color filter is used by specifying the transfer process.
Another object of the present invention is to make the surface of the color filter layer obtained by transfer as smooth as possible.
[0006]
[Means for Solving the Problems]
In the present invention, the adhesive layer for transfer is composed of a photo-curing type adhesive, so that a curing process including light irradiation is performed during the transfer, and the temperature change of the adhesive layer accompanying the curing process is predetermined. By limiting to the range, the dimensional change before and after the transfer of the color pattern is suppressed. Here, as the photo-curing adhesive for transfer, various types of materials that are photo-cured from the ultraviolet region to the visible region, for example, in the range of 200 nm to 700 nm can be used. Such an adhesive is required to be liquid in a solvent-free state as well as having excellent transparency in addition to the original adhesiveness. The latter is a requirement from the point that the adhesive layer is formed smoothly by various application means. For this reason, the adhesive always contains many monomer components. There are two types of photo-curing adhesives: radical polymerization and cationic polymerization. In radical polymerization, the photopolymerization initiator absorbs light, generates radical species, adds to the monomer, and chain polymerization proceeds. In the cationic polymerization type, the photopolymerization initiator absorbs light to generate a cation, and the cation serves as a catalyst to polymerize the monomer to become a polymer to be polymerized. The radical polymerization type has a short radical life, and there is a tendency that unreacted monomer components are inevitably left, and there is a possibility that the monomer components may be inferior in terms of reliability. . On the other hand, since the polymerization of the cationic polymerization type adhesive proceeds even after light irradiation, no unreacted substance remains and good reliability can be obtained. Therefore, a cationic polymerization type adhesive is optimal as the adhesive.
[0007]
In addition, curing by light irradiation has a small temperature rise during the curing process compared to other curing methods such as thermal curing, but for this type of color filter pattern, further measures to suppress the temperature rise are necessary. It is. As a means for suppressing the temperature rise of the adhesive layer accompanying the curing treatment, at least one of a method for suppressing heat generation of an optical system for light irradiation such as ultraviolet rays, or a method for cooling the side of the adhesive layer Can be applied. In addition, the light irradiation at the time of transfer is performed after the first light irradiation for temporary curing in which the adhesive layer is temporarily cured to such an extent that a dimensional change due to temperature rise does not occur in the color pattern and after the first light irradiation. It is also effective to carry out the method in two steps with the second light irradiation for the main curing performed with an irradiation intensity larger than the irradiation intensity at the time of the first light irradiation.
Usually, the temperature change of the adhesive layer at the time of transfer should be in a range satisfying the following relational expression.
ΔL × ΔT <5 × 10- ⁴
Here, ΔL is the difference between the temperature linear expansion coefficient L1 of the substrate such as glass and the temperature linear expansion coefficient L2 of the plastic film, and ΔT is the temperature rise of the adhesive layer accompanying the curing process during transfer. is there.
For example, the linear expansion coefficient of soda lime glass is 10 × 10- ^6, the linear expansion coefficient of polycarbonate is 5 × 10- ^5, when the operating temperature of the device including a color filter and 23 ° C. room temperature, the adhesive The curing temperature of the layer should be in the range of 10.5 ° C to 35.5 ° C.
[0008]
【Example】
Hereinafter, the content of the present invention will be described more specifically with reference to the embodiments shown in the accompanying drawings.
First, as shown in FIG. 1, a cleaned glass substrate 10 is prepared. The thickness of the glass substrate 10 is about 0.7 to 1.1 mm, and has rigidity as a whole. Since this glass substrate 10 is a substrate that supports the color filter layer 30 to be transferred to its surface, it has good surface smoothness, such as scratches and protrusions when visually observed with reflected light having a brightness of 5000 Lux under a dark room. It is desirable to have a surface smoothness (appearance standard of the substrate surface) that cannot be seen.
[0009]
As shown in FIG. 2, a release layer / protective layer 20 serving as a protective layer and a release layer is formed on the entire surface of the glass substrate 10. The release layer / protective layer 20 is a material that can withstand the environment during the formation of a color pattern and the like, stably adheres to the glass substrate 10, and exhibits appropriate peelability and shape retention during transfer. Furthermore, it is required to withstand the formation of a transparent electrode and not to dissolve in the liquid crystal. It is also important to have excellent transparency. A suitable material is polyimide, which can be applied and formed using spin coating or roll coating. The thickness is, for example, 1 to 5 μm. According to experiments, it is preferable that the thickness be four times or more that of the color filter layer 30 formed thereon. The release layer / protective layer 20 not only facilitates the transfer, but also has a function of smoothing the surface of the color filter layer 30, and the greater the thickness, the more advantageous is the smoothing.
[0010]
Next, as shown in FIG. 3, a color filter layer 30 including yellow, magenta, and cyan color patterns 30Y, 30M, and 30C is formed on the release layer / protective layer 20 by photolithography. As a material of the color patterns 30Y, 30M, and 30C, a known coating material in which a colorant such as a dye or a pigment is dissolved or dispersed in a polyimide resin solution can be used (for example, JP-A-10-170716). Each color pattern has a stripe shape, the width is 50 to 200 μm, and the distance between adjacent color patterns is 5 to 20 μm. The color filter layer 30 is of a reflective type and has a thickness of about 0.5 μm, for example, which is very thin compared to other layers.
[0011]
Further, as shown in FIG. 4, an adhesive layer 40 is formed by coating so as to entirely cover the color filter layer 30. The adhesive layer 40 is of an ultraviolet curable type and is of a cationic polymerization type, for example, an epoxy type ultraviolet curable adhesive (UV curable resin KR500 manufactured by Asahi Denka Kogyo Co., Ltd.). The thickness of the coating is about 5 to 20 μm, and can be set to a value having a thickness that can obtain sufficient adhesive strength and does not lose transmittance.
[0012]
Thereafter, as shown in FIG. 5, a plastic film 50 made of a polyethersulfone substrate is disposed on the adhesive layer 40 side, and the color filter layer 30 and the like are transferred from the glass substrate 10 side to the plastic film 50 side. In this transfer process, ultraviolet rays are irradiated from the plastic film 50 side. At the same time, the temperature increase on the side of the adhesive layer 40 (curing target) accompanying the irradiation is actively suppressed, and the temperature is set as close to room temperature as possible. . As a method for controlling the temperature, a. A method of blowing cooling air to an object to be cured; b. A method of inserting an optical cut filter for heat ray shielding between a light source for ultraviolet irradiation and an object to be cured; c. As an optical filter for shielding between the light source for UV irradiation and the object to be cured, the one that transmits the photosensitive wavelength range (365 nm) of the UV-curable adhesive and has an absorption band in other wavelength ranges, for example, a transfer target A method of inserting the same material as the glass substrate 10 on which the plastic film 50 and the color filter layer 30 are formed can be applied in combination.
[0013]
In this regard, when ultraviolet irradiation and transfer are performed without such temperature control, the pattern dimension before curing by ultraviolet irradiation is 100.000 mm, and the pattern dimension after transfer after curing is 99.866 mm. The pattern dimension change rate at 1.3 was 1.3 × 10 ⁻³ . On the other hand, when an object to be cured is placed on an aluminum plate, a quartz substrate having a thickness of 3 mm is placed between the light source for ultraviolet irradiation and the object to be cured, and curing by ultraviolet irradiation is performed, pattern dimension is 100.000Mm, pattern size after transferring after curing is 99.973Mm, the rate of change of pattern size before and after the transfer became 2.7 × 10- ^4. In addition, when the object to be cured is placed on an aluminum plate, the same polyethersulfone substrate as the object to be transferred is placed between the UV irradiation light source and the object to be cured, and curing is performed by UV irradiation. previous pattern dimension is 100.000Mm, pattern size after transferring after curing is 99.987Mm, the rate of change of pattern size before and after the transfer became 1.3 × 10- ^4. Such a transfer process was performed in an environment at room temperature, and the temperature change before and after the transfer was suppressed to the predetermined range. Further, the surface of the color filter layer 30 after the transfer had good smoothness of 0.1 μm or less.
[0014]
Further, as another method, a method in which ultraviolet irradiation is performed in two stages of temporary curing and main curing can be applied. In the pre-curing, irradiation is performed with relatively low energy to such an extent that a dimensional change due to temperature rise does not occur, and in the subsequent main curing, curing is also performed completely by irradiation with higher energy. In pre-curing, use a cold mirror that selectively reflects only the required wavelength, such as irradiating with only indirect light. This effectively suppresses the temperature rise of the object to be cured. For example, after performing temporary curing at an irradiation amount of 7 mW / cm ² × 4 minutes, irradiation of main curing at 1000 mJ / cm ² is performed. In this regard, by electrically controlling the power supply circuit for ultraviolet irradiation, temporary curing in a state in which the temperature rise is suppressed, and main curing for completely curing the resin, and temporary curing and main curing are performed. It can be done continuously. Of course, in the case of an adhesive that requires a small amount of irradiation for curing, the curing treatment can be performed by one irradiation instead of two steps.
[0015]
As the plastic film 50, polyester, polycarbonate, vinyl chloride, nylon, polyarylate, acrylic, polyimide, or the like can be applied in addition to the polyether sulfone. Moreover, the plastic film 50 can be used in any form of a sheet (sheet) or a roll, and a preferable thickness is in a range of 0.1 mm to 1 mm. Therefore, the plastic film here is a concept including a sheet-like member including a so-called film or sheet.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a glass substrate with low thermal stretchability.
FIG. 2 is a cross-sectional view showing a state where a release layer / protective layer is formed on a glass substrate.
FIG. 3 is a cross-sectional view showing a state in which a color filter layer is formed on a release layer / protective layer.
FIG. 4 is a cross-sectional view showing a state in which an adhesive layer is applied on a color filter layer.
FIG. 5 is a cross-sectional view showing a state during transfer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Glass substrate 20 Release layer and protective layer 30 Color filter layer 40 Adhesive layer 50 Plastic film

Claims (6)

A method of manufacturing a color filter including a color filter layer including a plurality of different color patterns on a plastic film, wherein the color filter layer is formed on a substrate having a lower thermal elasticity than the plastic film. And a second step of transferring a color filter layer including the color patterns of the plurality of colors on the substrate onto the plastic film through the adhesive layer after the first step, and the adhesive By configuring the layer with a photo-curing type adhesive, a curing process including light irradiation is performed at the time of the transfer, and further, the temperature change of the adhesive layer accompanying the curing process is suppressed to a predetermined range. A method for producing a color filter, characterized in that dimensional change before and after pattern transfer is suppressed.   The method for producing a color filter according to claim 1, wherein the photocurable adhesive is a cationic polymerization adhesive.   As a means for suppressing the temperature rise of the adhesive layer accompanying the curing treatment, at least one of a method for suppressing heat generation of the optical system for the light irradiation and a method for cooling the side of the adhesive layer is used. The manufacturing method of the color filter of Claim 1 applied.   After the first light irradiation, the light irradiation at the time of the transfer includes a first light irradiation for temporary curing in which the adhesive layer is temporarily cured to such an extent that a dimensional change due to temperature rise does not occur in the color pattern. The method for producing a color filter according to claim 1, wherein the method is carried out over two steps of the second light irradiation for the main curing performed at an irradiation intensity larger than the irradiation intensity at the time of the first light irradiation.   The method for producing a color filter according to claim 1, wherein the color filter layer before transfer is located on one surface of the substrate and on the release layer / protective layer. The method for producing a color filter according to claim 1, wherein the temperature change of the adhesive layer during the transfer is in a range satisfying the following relational expression.
ΔL × ΔT <5 × 10 −4
Here, ΔL is a difference between the temperature linear expansion coefficient L1 of the substrate and the temperature linear expansion coefficient L2 of the plastic film, and ΔT is the temperature of the adhesive layer accompanying the curing process during the transfer. It is a rise.

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