JP4356444B2 - Overcoat layer forming method and color filter - Google Patents

Description

  The present invention relates to a color filter used for an organic EL element or a liquid crystal display, and more particularly to a method for forming a smooth overcoat layer free from foreign matter on a color filter.

  An organic EL device has a structure in which a thin organic layer containing a fluorescent organic compound is sandwiched between a cathode forming an electron injection electrode and an anode forming a hole injection electrode, and electrons and holes are injected into the organic layer. In this display element, an exciton is generated by recombination and light is emitted (fluorescence / phosphorescence) when the exciton is deactivated. There are several methods for producing a full-color organic EL display using an organic EL element, and the following methods are known as full-color methods.

  The method of patterning three types of EL elements that emit three colors of red, green, and blue according to the pixel (method 1) is highly efficient because the emitted light can be used as it is. However, there is a problem that the process of painting EL is complicated and it is difficult to increase the screen size because vapor deposition is performed using a metal mask, and it is necessary to make the life of each color uniform.

  The EL element that emits blue light is made solid on the entire screen, and the red and green pixels have a color conversion layer that absorbs blue light and emits red and green fluorescence, respectively, and is patterned according to the pixels The method of performing full color using layers (method 2) converts light of one color into other light, so that the light use efficiency is good, and the EL element does not need to be complicatedly divided.

However, in the case of this method, in the color conversion layer, it is necessary to suppress the dye concentration in the film to a certain amount or less so that the fluorescent dye contained in the film does not cause concentration quenching. In order to increase the light conversion efficiency while suppressing the dye concentration, it is necessary to increase the film thickness of the conversion layer, and the film thickness is generally about 10 μm.
However, this film thickness is too thick for patterning by photolithography. Furthermore, in order to prevent the fluorescent dye of the color conversion layer from being excited by external light, it is necessary to further stack red and green color filters on the base of the color conversion layer. Therefore, there is a difficulty that the manufacturing process of the color conversion layer becomes complicated.

The EL element emits white light and the red, green, and blue color filters are superimposed on it to make it full color (Method 3), which is very similar to the transmissive LCD full color method and has the most structure. There is an advantage that it is simple and has good productivity, and there is no color shift due to the change of EL over time, but this method is inferior to other full color methods because the white light source is changed to RGB. .
However, this method is attracting attention because of the cost of mass production and the ease of expansion to a larger screen.

Among the above-mentioned full color schemes for organic EL elements, a scheme for converting blue light emitted by the EL elements into red and green (method 2) and white light emitted by the EL elements for red, green and blue color filters In the method of colorizing by (Method 3), a method of laminating an EL light emitting layer on a substrate on which a color filter layer and a color conversion layer are formed is generally used.
At this time, the electrode and light emitting layer formed on the upper part are disconnected due to the unevenness of the step between the pixels of the patterned color filter layer and color conversion layer and the roughness of the surface of the color filter layer and color conversion layer. In order to prevent this, an overcoat layer is often provided on the color filter layer or the color conversion layer in order to smooth the surface.

  Furthermore, in order to prevent the organic EL element from deteriorating due to the influence of moisture contained in the binder resin of the overcoat layer, the color filter layer, and the color conversion layer, a barrier layer called a passivation layer is formed on the overcoat layer. It is often done. It is known that a passivation layer mainly uses a silicon nitride or oxynitride film, and this film is formed by CVD or sputtering.

  By the way, when forming a passivation layer on the overcoat layer, if a minute foreign matter adheres to the surface of the overcoat layer, only a portion of the foreign matter at the time of film formation of the passivation layer has a film formation defect portion like a pinhole. From this, moisture contained in the color filter layer or the color conversion layer oozes out and damages this portion of the EL light emitting layer, resulting in a point-like non-light emitting portion called a dark spot.

  In order to prevent pinholes from being generated during the formation of the passivation layer, methods such as forming a thick passivation layer or forming a plurality of layers have been used. However, light transmittance by absorption of the passivation layer is used. As the film thickness of the passivation layer is increased, the stress of the film is increased and cracks are generated in the passivation layer.

  On the other hand, when forming the overcoat layer, the photosensitive resin for forming the overcoat layer is coated on the color filter and then exposed to foreign matter adhering to the substrate from the environment or when exposed through a photomask. In order to make a gap between the substrates, foreign substances transferred from the photomask to the substrate once exist on the surface of the overcoat layer when the substrate and the photomask are brought into contact with each other. This is similar to the case where foreign matter adheres when forming the overcoat layer in the production of the color filter for liquid crystal.

  To prevent foreign matter from being transferred from the photomask to the overcoat during exposure, the overcoat layer may be formed as a solid film without patterning, but when a passivation layer is formed on the overcoat solid film When the substrate is cut into each panel, the overcoat layer is exposed in the cut section, and moisture is oozed out from the portion, so that the patterning of the overcoat layer is necessary. In the case of a color filter for liquid crystal, if the size of adhering foreign matter is smaller than the cell gap of the liquid crystal panel, it is said that there is no problem with the operation of the liquid crystal element, and the size is generally about 5 μm.

  However, the size of the foreign matter that must be removed in order not to affect the organic EL light-emitting layer is that the thickness of the light-emitting layer of the organic EL element is much thinner than the cell gap of the liquid crystal element, so a color filter for liquid crystal A foreign material smaller than the size of the foreign material that must be removed when the overcoat layer is formed, for example, a foreign material of about 1 μm must be removed. Existing liquid crystal color filter substrate cleaning methods include roll brush cleaning, high pressure shower cleaning, two-fluid water cleaning, and ultrasonic cleaning. In general, however, cleaning becomes more difficult as the size of foreign matter that must be removed becomes smaller. . In addition, when the overcoat layer has tackiness after application and before post-baking, the adhesion of the foreign matter is strengthened, so that it is difficult to remove the foreign matter as compared with normal glass substrate cleaning.

On the other hand, a liquid crystal display has an electrode formed on a glass substrate by sandwiching a liquid crystal substance aligned by an alignment film or a rib between two glass substrates spaced apart by cell beads or post spacers. The image is formed by controlling the voltage to change the orientation of the liquid crystal substance and controlling the light transmittance in combination with the polarizing plate. In many cases, the color filter is formed on one glass substrate so as to be under the electrode. At this time, if foreign matter is present on the overcoat of the color filter, an electrode on the color filter is formed on the foreign matter, causing a problem that the electrode contacts the electrode of the counter substrate and short-circuits.

  In this case, as described above, if the height of the foreign material is smaller than the cell gap, a short circuit between the electrode formed on the foreign material and the electrode on the counter substrate does not occur. However, development has progressed in the direction of narrowing the cell gap in order to drive the liquid crystal display at a high speed, and for this reason, there is a strong demand for removing foreign substances on the overcoat layer on the color filter.

Also, in the case of the overcoat layer of the liquid crystal color filter, unlike the organic EL color filter, the requirement for moisture removal is not so strict, but the adhesion strength when bonding two glass substrates enclosing a liquid crystal substance is increased. For the purpose of increasing the thickness, an overcoat layer at an adhesive portion is also removed by photolithography. In this case, the adhesion of foreign matter through a photomask becomes a problem as in the method of manufacturing the organic EL color filter.
JP-A-6-11612 JP-A-6-281808 JP 2003-75626 A

  The present invention relates to a method for forming an overcoat layer in which, in an organic EL color filter or a liquid crystal color filter, when an overcoat layer is formed on the color filter, an overcoat layer having no foreign matter on the surface and having high smoothness is formed. It is a problem to provide. Another object of the present invention is to provide a color filter for organic EL or a color filter for liquid crystal manufactured by this forming method.

The present invention relates to a method for forming an overcoat layer in which an overcoat layer having a high surface smoothness is formed on a color filter using a photolithography method.
1) A positive photosensitive resin was used on the substrate on which the color filter layer was formed, and the film thickness (film thickness 2) of the foreign substance removal layer was added to the film thickness (film thickness 1) of the patterned overcoat layer to be formed. Providing a coating film having a film thickness (film thickness 3);
2) a step of performing exposure through a photomask for forming a patterned overcoat layer on the coating film;
3) A step of performing overall exposure on the coating film corresponding to the film thickness (film thickness 2) of the foreign substance removal layer;
4) A step of removing the foreign matter removal layer by development and removing the non-patterned portion of the overcoat layer to form a patterned overcoat layer;
A method for forming an overcoat layer.

Further, the present invention provides a method for forming an overcoat layer in which an overcoat layer having high surface smoothness is formed on a color filter using a photolithography method.
1) A positive photosensitive resin was used on the substrate on which the color filter layer was formed, and the film thickness (film thickness 2) of the foreign substance removal layer was added to the film thickness (film thickness 1) of the patterned overcoat layer to be formed. Providing a coating film having a film thickness (film thickness 3);
2) A step of performing overall exposure corresponding to the film thickness (film thickness 2) of the foreign substance removal layer on the coating film;
3) A step of performing exposure through a photomask for forming a patterned overcoat layer on the coating film,
4) A step of removing the foreign matter removal layer by development and removing the non-patterned portion of the overcoat layer to form a patterned overcoat layer;
A method for forming an overcoat layer.

  The present invention is also the overcoat layer forming method according to the above invention, wherein the overcoat layer is an overcoat layer of a color filter for an organic EL device.

  The present invention is also the overcoat layer forming method according to the above invention, wherein the overcoat layer is an overcoat layer of a color filter for a liquid crystal display.

  The present invention also provides a color filter for an organic EL element having an overcoat layer formed by the overcoat layer forming method according to claim 3.

  The present invention also provides a color filter for a liquid crystal display having an overcoat layer formed by the overcoat layer forming method according to claim 4.

  In the present invention, 1) a positive photosensitive resin is used on a substrate on which a color filter layer is formed, and the film thickness (film thickness 2) of the foreign substance removal layer is added to the film thickness (film thickness 1) of the overcoat layer. A step of providing a coating film having a film thickness (film thickness 3), 2) a step of performing exposure through a photomask for forming a patterned overcoat layer, and 3) corresponding to a film thickness (film thickness 2) of the foreign matter removing layer. A method of forming an overcoat layer comprising a step of performing overall exposure, 4) a step of removing a foreign matter removal layer by development, and a step of removing a non-patterned portion of the overcoat layer to form a patterned overcoat layer. This is a method for forming an overcoat layer in which an overcoat layer having no foreign matter on the surface and high smoothness is formed.

  In addition, since it is a color filter for organic EL elements or a color filter for liquid crystal display having an overcoat layer formed by the above-described method for forming an overcoat layer, the organic EL having a highly smooth overcoat layer with no foreign matter on the surface It becomes a color filter for elements or a color filter for liquid crystal displays.

  Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is a cross-sectional view showing one embodiment of a method for forming an overcoat layer of an organic EL color filter or a liquid crystal color filter according to the present invention. In FIG. 1 (1), a color filter layer 2 is provided on a transparent substrate 1, and a positive photosensitive resin for forming an overcoat layer 3 is applied thereon.
The positive photosensitive resin coating film 33 includes a coating film portion 31 for forming a patterned overcoat layer and a coating film portion 32 of a foreign matter removal layer for removing foreign matter. That is, the film thickness (film thickness 3 (D3)) of the positive photosensitive resin coating film 33 is set to a film thickness (film thickness 1 (D1)) necessary for forming the overcoat layer 3 to remove foreign matter. Is added to the necessary film thickness (film thickness 2 (D2)). The film thickness 1 and the film thickness 2 are in the relationship of film thickness 1> film thickness 2.

At this time, foreign matter adhering to the coating film 33 from the environment after coating or foreign matter originally attached to the lower surface of the photomask 6 is transferred to the surface of the coating film 33 when the photomask 6 and the substrate come into contact with each other. , Adhered foreign matter 4 is present.
In FIG. 1B, exposure light 5 is given to the overcoat layer through a photomask. By performing sufficient exposure, the coating film 33 in the portion 33 ′ that is not shielded by the photomask 6 reacts with the exposure light so that the film thickness 3 (D3) can be dissolved in the developer.

  In FIG. 1C, the entire surface of the substrate is exposed after the photomask 6 is removed. At this time, the exposure light 5 'has a smaller exposure amount than the exposure light 5 when exposed through the photomask 6 in FIG. At this time, the coating film portion 32 of the foreign matter removal layer having a film thickness 2 (D2) above the coating film 33 coated so as to cover the color filter layer 2 can be dissolved in the developer in response to the exposure light. It becomes a state.

  In FIG. 1 (4), the exposed coating film is removed from the portion of the coating film that can be dissolved in the developing solution by development. The coating film portion 32 of the foreign matter removing layer and the coating film portion 31 of the portion 33 ′ (non-patterned portion) that is not shielded by the photomask 6 are removed, and at the same time, the foreign matter 4 attached to the surface is also removed. At this time, the development time is adjusted so that the film thickness of the remaining overcoat layer 3 after development becomes a desired film thickness.

In the description so far, the patterning exposure is performed through the photomask 6 as shown in FIG. 1 (2), and then the entire surface exposure is performed as shown in FIG. 1 (3). Patterning exposure may be performed.
By baking and curing the positive photosensitive resin thus patterned, the overcoat layer 3 having no foreign matter and high smoothness can be formed.

Example 1 of the present invention will be described below, but the present invention is not limited to this example.
First, red, green, and blue color filter layers were formed on a glass substrate so that each film thickness was 1.5 μm. Next, a positive type photosensitive resin PC-403 (manufactured by JSR) was applied on the color filter layer using a spin coater so as to have a film thickness of 4 μm, and prebaked on a hot plate at 90 ° C. for 2 minutes.
Next, this coating film was exposed to 300 mJ / cm ² using a photomask shaped so as to cover the matrix of the color filter layer. Further, the photomask was removed and 100 mJ / cm ² overall exposure was performed. Next, this coating film was developed for 40 seconds using an alkali developer, and then post-baked at 230 ° C. for 1 hour.

The film thickness of the overcoat layer remaining on the matrix of the color filter layer was about 3 μm . When the obtained overcoat layer was observed with a laser microscope, no foreign matter was found on the surface.

First, red, green, and blue color filter layers were formed on a glass substrate so that each film thickness was 1.5 μm. Next, a positive photosensitive resin PC-403 (manufactured by JSR) is applied on the color filter layer using a spin coater so as to have a film thickness of 2.5 μm, and prebaked on a hot plate at 90 ° C. for 2 minutes. It was. Next, this coating film was exposed to 300 mJ / cm ² using a photomask shaped so as to cover the matrix of the color filter layer.

  Next, this coating film was developed for 30 seconds using an alkaline developer, and then post-baked at 230 ° C. for 1 hour. The film thickness of the overcoat layer remaining on the matrix of the color filter layer was about 2 μm. When the obtained overcoat layer was observed with a laser microscope, foreign matter having a size of about 5 μm was confirmed on the surface.

It is sectional drawing which shows one Example of the formation method of the overcoat layer of the color filter for organic EL by this invention, or the color filter for liquid crystals.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent base material 2 ... Color filter layer 3 ... Overcoat layer 4 ... Foreign material 5, 5 '... Exposure light 6 ... Photomask 31 ... Patterned overcoat layer Coating film portion 32 for forming the coating film portion 33 of the foreign matter removal layer ... coating film 33 'of the positive photosensitive resin ... portion not shielded by the photomask

Claims (6)

In the overcoat layer forming method of forming an overcoat layer with high surface smoothness using a photolithography method on the color filter,
1) A positive photosensitive resin was used on the substrate on which the color filter layer was formed, and the film thickness (film thickness 2) of the foreign substance removal layer was added to the film thickness (film thickness 1) of the patterned overcoat layer to be formed. Providing a coating film having a film thickness (film thickness 3);
2) a step of performing exposure through a photomask for forming a patterned overcoat layer on the coating film;
3) A step of performing overall exposure on the coating film corresponding to the film thickness (film thickness 2) of the foreign substance removal layer;
4) A step of removing the foreign matter removal layer by development and removing the non-patterned portion of the overcoat layer to form a patterned overcoat layer;
A method for forming an overcoat layer, comprising: In the overcoat layer forming method of forming an overcoat layer with high surface smoothness using a photolithography method on the color filter,
1) A positive photosensitive resin was used on the substrate on which the color filter layer was formed, and the film thickness (film thickness 2) of the foreign substance removal layer was added to the film thickness (film thickness 1) of the patterned overcoat layer to be formed. Providing a coating film having a film thickness (film thickness 3);
2) A step of performing overall exposure corresponding to the film thickness (film thickness 2) of the foreign substance removal layer on the coating film;
3) A step of performing exposure through a photomask for forming a patterned overcoat layer on the coating film,
4) A step of removing the foreign matter removal layer by development and removing the non-patterned portion of the overcoat layer to form a patterned overcoat layer;
A method for forming an overcoat layer, comprising:   The method for forming an overcoat layer according to claim 1, wherein the overcoat layer is an overcoat layer of a color filter for an organic EL device.   The method for forming an overcoat layer according to claim 1 or 2, wherein the overcoat layer is an overcoat layer of a color filter for a liquid crystal display.   A color filter for organic EL elements, comprising an overcoat layer formed by the method for forming an overcoat layer according to claim 3.   A color filter for a liquid crystal display, comprising an overcoat layer formed by the method for forming an overcoat layer according to claim 4.

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