JP2007010845A - Pixel forming method and color filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pixel forming method by which pixels with uniform film thickness all over a substrate can be formed with tendency of film thickness distribution being corrected even when the coating film shows the tendency of film thickness distribution specific to the coating machine used, and to provide a color filter produced by the pixel forming method. <P>SOLUTION: The pixel forming method includes steps of applying a coating film 2 of a negative photoresist on a substrate 1, exposing the film to light through a photomask and developing, wherein the photomask PM2 has a halftone portion 4 in a part on the photomask corresponding to a portion with a large film thickness in the film thickness distribution of a coating film specific to the coating device used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pixel forming method, and more particularly to a method for forming a pixel having a uniform thickness by correcting the thickness of a coating film unique to a coating apparatus.

In a display device such as a liquid crystal display device or a PDP, it is a useful means to use a color filter for purposes such as color display, reflectance reduction, contrast improvement, and spectral characteristic control.
In many cases, the color filter used in the display device is formed and used as a pixel. As a method for forming a pixel of a color filter for a display device, a photolithography method, a printing method, and the like can be cited as methods that have been put into practical use.

For example, FIG. 3 is a plan view schematically showing an example of a color filter used in a liquid crystal display device. 4 is a cross-sectional view of the color filter shown in FIG. 3 taken along line XX ′.
As shown in FIGS. 3 and 4, the color filter used in the liquid crystal display device has a black matrix (51) and colored pixels (52) sequentially formed on a glass substrate (50).
3 and 4 schematically show a color filter, and 12 colored pixels (52) are shown. In an actual color filter, for example, several hundreds of pixels are displayed on a 17-inch diagonal screen. A large number of colored pixels of about μm are arranged.

The black matrix (51) is a matrix having light shielding properties, and the colored pixels (52) have, for example, red, green, and blue filter functions.
The black matrix determines the position of the colored pixels of the color filter, makes the size uniform, and shields unwanted light when used in a display device, making the image of the display device uniform and uniform. In addition, it has a function of making an image with improved contrast.

This black matrix (51) is an example in which a resin is used as a black matrix material on a glass substrate (50).
The black matrix (51) is formed on the glass substrate (50) by, for example, a photolithography method using a black photoresist for forming a black matrix. It is called the resin black matrix (51).

  The colored pixel (52) is a photolithography method using a negative colored photoresist in which a pigment such as a pigment is dispersed on the glass substrate (50) on which the resin black matrix (51) is formed. That is, it is formed as a colored pixel by exposure through a photomask to a coating film of a colored photoresist, and development processing. Red, green, and blue colored pixels are sequentially formed.

Conventionally, in a manufacturing process of a liquid crystal display device, as a coating device such as a photoresist, a spin coater that forms a coating film by dropping a coating solution from a nozzle onto the center of a glass substrate and then rotating the glass substrate to spread the coating solution Has been used a lot.
Fig.1 (a) is a top view explaining the state of the coating film (2) formed on the glass substrate (1) with the spin coater. Moreover, FIG.1 (b) is sectional drawing in the AA of (a). As shown in FIGS. 1A and 1B, the film thickness of the coating film (2) formed on the glass substrate (1) by the spin coater is such that the central portion of the glass substrate (1) is thin and the peripheral portion is There is a tendency for the film thickness distribution to be thick.
In the plan view of FIG. 1 (a), for the sake of explanation, the thickness of the coating film is represented by the density of oblique lines.

The slit coater is a method for applying a coating solution to a glass substrate from a slit nozzle while horizontally moving a coating plate or a coating head on which the glass substrate is placed. Mainly, the glass substrate is, for example, 1 m × 1. This is a coating apparatus applied to a large size of 3 m or more.
Fig.2 (a) is a top view explaining the state of the coating film (2) formed on the glass substrate (1) with the slit coater. Moreover, FIG.2 (b) is sectional drawing in the AA line of Fig.2 (a). Similar to FIG. 1A, the thickness of the coating film is represented by the solid line density.

As shown in FIGS. 1A and 1B, the film thickness of the coating film (2) formed on the glass substrate (1) by the slit coater is the film thickness at the start of application to the glass substrate (1). The film thickness tends to be thick. In addition, the white thick arrow represents the application direction of the coating liquid.
This phenomenon is because the concentration of a part of the coating liquid in the tip becomes higher if the tip of the slit nozzle is in contact with air during standby before the start of coating.

  In the slit coater, the reverse phenomenon occurs, but there may be a tendency of the film thickness distribution such that the film thickness at the application start point on the glass substrate (1) is thin (not shown). This phenomenon is because, for example, the concentration of a part of the coating liquid in the tip is lowered by immersing it in a tank in which the cleaning liquid is stored in order to prevent the tip of the slit nozzle from drying during standby before the start of coating.

  As described above, when the coating film formed on the glass substrate has a thin distribution, the formed pixel reflects the tendency of the thin distribution, and is composed of, for example, the colored pixels. Such a color filter impairs the quality of the display device.

FIG. 5 is an explanatory diagram of an example in which the distribution tendency of the thickness of the coating film is reflected in the thickness of the pixel. As shown to Fig.5 (a), exposure (5) through a photomask (PM1) is given to the negative photoresist coating film (2) formed on the glass substrate (1) with the spin coater, and development is carried out When the processing is performed, as shown in FIG. 5B, a pixel (3) reflecting a film thickness distribution in which the central portion of the glass substrate (1) is thin and the peripheral portion is thick is formed.
Japanese Patent Laid-Open No. 10-206622

The present invention has been made to solve the above problems, and the photoresist coating film applied on the substrate has a tendency of the coating thickness distribution inherent in the coating apparatus used. However, an object of the present invention is to provide a pixel forming method in which the tendency of the film thickness distribution is corrected and pixels having a uniform film thickness can be formed over the entire surface of the substrate.
It is another object of the present invention to provide a color filter manufactured using the pixel forming method.

  The present invention provides a pixel forming method in which a negative photoresist coating film is provided on a substrate using a coating apparatus, and pixels are formed by exposure and development processing through a photomask. In the film thickness distribution of the coating film unique to the apparatus, the pixel forming method is characterized by having a half-tone portion in a portion on the photomask corresponding to a thick portion.

According to the present invention, in the pixel forming method according to the above invention, the halftone portion is a line and space pattern having a pitch equal to or lower than a resolution of a system for forming pixels.

  In addition, the present invention is a color filter manufactured using the pixel forming method according to claim 1 or 2.

  The present invention provides a pixel forming method in which a negative photoresist coating film is provided on a substrate using a coating apparatus, and pixels are formed by exposure and development processing through a photomask. Of the coating film thickness distribution unique to the device, it has a half-tone part on the photomask corresponding to the thick part of the coating film, so the coating film of the photoresist coated on the substrate is used Even if it has a tendency of the film thickness distribution unique to the film, the tendency of the film thickness distribution is corrected, and the pixel forming method can form pixels with a uniform film thickness over the entire surface of the substrate.

  In addition, since the present invention is a color filter manufactured using the above pixel forming method, the tendency of the film thickness distribution is corrected, and the color filter has pixels with a uniform film thickness over the entire surface of the substrate.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 6 is an explanatory view schematically showing an example of a pixel forming method according to the present invention. FIG. 6 (a) shows a negative photoresist formed on a glass substrate (1) by a spin coater, and a coating film (2) having a film thickness distribution unique to the spin coater is provided on the coating film (2). The state which has given exposure (5) through the photomask (PM2) in this invention is shown.

The photomask (PM2) includes a portion on the photomask (PM2) corresponding to the thick portion of the coating thickness distribution on the glass substrate (1), that is, the periphery of the photomask (PM2). Has a half-tone part (4). The half tone part (4) is provided in the light transmission part of the peripheral part of the photomask (PM2).
Accordingly, as shown in FIG. 6B, the pixel (3 ′) obtained after the development processing has a low residual film ratio of the coating film at the peripheral portion of the glass substrate (1), that is, the film of the pixel at the peripheral portion. The thickness is reduced, the tendency of the film thickness distribution is corrected, and pixels having a uniform film thickness are formed over the entire surface of the glass substrate.

The density of the halftone part (4) at the peripheral part of the photomask (PM2) is such that the film thickness of the pixel formed at the peripheral part on the glass substrate is the same as the film thickness of the pixel formed at the central part of the glass substrate. It sets so that it may become, according to the film thickness of the coating film on a glass substrate (1).
The half-tone part (4) includes a thin film that attenuates ultraviolet rays, for example, a half-tone part made of a metal oxide film such as ITO, or a half-tone part obtained by photo-etching a chromium film formed when manufacturing a photomask. It is done.

However, since the film thickness distribution of the coating film on the glass substrate (1) is, for example, inclined so that the film thickness gradually increases from the central portion to the peripheral portion of the glass substrate, the half-tone portion (4) Is preferably a line and space pattern having a pitch less than or equal to the resolution of the system forming the pixels.
This line and space pattern has a density gradient from the central portion to the peripheral portion at a pitch less than the resolution of the system.

FIG. 7A is an enlarged plan view showing a part of the line and space pattern. Moreover, FIG.7 (b) is sectional drawing of the XX 'line in Fig.7 (a).
As shown in FIGS. 7A and 7B, this haline and space pattern includes a line (L) that blocks light and a space (S) that transmits light.
The line and space pattern in the present invention is below the resolution of the system of the photolithography method used.
The photolithographic system refers to, for example, an entire process such as an optical system for forming pixels, a photomask, a colored photoresist, and a development process, and the resolution of a pixel pattern obtained is determined by the resolution of the system. .

For example, the degree of phase alignment of the exposure light, the case where the photomask is used after being projected at a reduced size, and the case where the photomask is used in its original size, or the difference in effective resolution of the photomask depending on the structure type of the photomask, The resolution of the system is determined by the resolution of the colored photoresist and the development processing conditions.
In the present invention, the film thickness distribution of the coating film on the glass substrate by exposure through a single photomask, the film thickness of the pixel formed in the normal film thickness portion, and the thick film thickness portion In order to simultaneously and uniformly form the film thickness of the pixels formed on the photomask, the line-and-space pattern of the halftone portion (4) on the photomask is subjected to the photolithographic method system at the time of exposure to the colored photoresist. Below the resolution.

  FIG. 8 is an enlarged view of the cross-section of the line and space pattern shown in FIG. 7B, and coloring of light transmitted through the space (S) (transparent portion (opening)) of the line and space pattern. There is a schematic representation of the intensity distribution on the photoresist. As shown in FIG. 8A, if the pitch (Pw) and the line width (Lw) of the line and space pattern are sufficiently large, the light transmitted through the opening forms an image on the photomask. However, as shown in FIG. 8B, for example, when the line width (Lw) is narrowed, the images cannot be separated by diffraction by light from adjacent openings. Eventually, the light transmitted through the opening is averaged into a uniform intensity distribution.

  That is, in the present invention, the line-and-space pattern is formed to have a line-and-space image of the line-and-space pattern of the halftone portion (4) on the photomask by making the line-and-space pattern below the resolution of the photolithography system. It is made to function as a halftone portion having a uniform optical density.

  The effective optical density as a halftone portion is expressed as a ratio of lines and spaces to a unit area. In addition, the line and space line (L) has a density that blocks light (for example, OD> 2.5 or more), the space (S) transmits light, and the density is substantially zero. Therefore, it is possible to accurately obtain a semi-light-shielding portion having an effective optical density arbitrarily by adjusting the line ratio.

The relationship between the line and space pattern and the resolution of the photolithographic system includes the line and space pattern pitch (Pw) shown in FIG. 8, the line and space pattern line width (Lw), and the space width (Sw). However, the resolution of the colored photoresist used when forming the colored pixels of the color filter for the liquid crystal display device by the pigment dispersion method is about 6 μm, so about 6 μm is a standard.
Specifically, for example, when the line width (Lw): space width (Sw) = 1: 1, the line and space cannot be separated when the pitch (Pw) is about 8 μm or less. For example, when the line width (Lw): space width (Sw) = 1: 5, the line and space cannot be separated if the line width (Lw) is about 3 μm or less.

In addition, the line and space pattern in the present invention is a line and space pattern that is less than the resolution of the system of the photolithography method, and is particularly limited as long as it is a pattern that represents the optical density in the ratio of the line occupying the unit area. is not. For example, checkered pattern, wavy pattern, circular pattern, etc.

(A) is a top view explaining the state of the coating film formed on the glass substrate with the spin coater. (B) is sectional drawing in the AA of (a). (A) is a top view explaining the state of the coating film formed on the glass substrate with the slit coater. (B) is sectional drawing in the AA of FIG. 2 (a). It is the top view which showed typically an example of the color filter used for a liquid crystal display device. It is sectional drawing in the X-X 'line | wire of the color filter shown in FIG. It is explanatory drawing of the example in which the distribution tendency of a coating film is reflected in the thinness of the film thickness of a pixel. It is explanatory drawing which shows typically an example of the pixel formation method by this invention. (A) is a top view which expands and shows the halftone part shown in FIG. FIG. 7B is a cross-sectional view taken along line X-X ′ in FIG. It is explanatory drawing which expands and shows the cross section of the halftone part shown in FIG.7 (b).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 50 ... Glass substrate 2 ... Coating film 3 ... Pixel 3 'reflecting film thickness distribution ... Pixel 4 in the present invention ... Half-tone part 5 ... Exposure 51 ... Black Matrix 52... Colored pixels L... Light shielding line Lw... Line width PM1... Photomask PM2. ..Light-transmitting space Sw ... Space width

Claims (3)

  In a pixel forming method in which a negative photoresist coating film is provided on a substrate using a coating apparatus, and pixels are formed by exposure and development processing through a photomask, the photomask is unique to the coating apparatus used. A pixel forming method characterized by having a half-tone portion in a portion on a photomask corresponding to a thick portion of the film thickness distribution of the coating film.   2. The pixel forming method according to claim 1, wherein the half-tone portion is a line and space pattern having a pitch equal to or less than a resolution of a system for forming pixels.   A color filter manufactured using the pixel forming method according to claim 1.

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