JP2021002033A - Color filter substrate, liquid crystal display device, and method of manufacturing color filter substrate - Google Patents

Abstract

To provide a color filter substrate appropriate for preventing a variation in luminance between pixels, a method of manufacturing the color filter substrate, and a liquid crystal display device comprising the color filter substrate.SOLUTION: A color filter substrate comprises a transparent substrate, a plurality of color filter layers aligned on the transparent substrate, and a light shielding layer arranged on the transparent substrate and separating the plurality of color filter layers adjacent to each other. The light shielding layer is a resin cured product that is made by patterning a photoresist and forms an eave part protruding in parallel with the transparent substrate on an end of the light shielding layer not in contact with the transparent substrate.SELECTED DRAWING: Figure 3

Description

The present invention relates to a color filter substrate, a liquid crystal display device, and a method for manufacturing a color filter substrate.

A liquid crystal display device is a display device that uses a liquid crystal composition for display, and a typical display method thereof is a backing to a liquid crystal panel in which a liquid crystal composition is enclosed between a color filter substrate and a facing substrate. By irradiating light from a light and applying a voltage to the liquid crystal composition to change the orientation of the liquid crystal molecules, the amount of light transmitted through the liquid crystal panel is controlled. Since such a liquid crystal display device has features such as thinness, light weight, and low power consumption, it is used in electronic devices such as televisions, smartphones, tablet terminals, and car navigation systems.

The light transmitted through the liquid crystal panel passes through the color filter layer provided on the color filter substrate and is converted into color light corresponding to the color of the color filter layer, and color display is realized by mixing the color light. A light-shielding layer (black matrix) is generally provided between the color filter layers. The black matrix has functions such as preventing light leakage during black display and unintended color mixing between adjacent color filter layers. As the black matrix, one made of chrome and one made of resin are known. Patent Document 1 describes an example of a resin black matrix.

JP-A-2015-26049

With the progress of high-definition pixels in liquid crystal display devices, the roughness of the screen display is visually recognized in high-definition liquid crystal display devices exceeding 1000 ppi, which may cause a problem in display quality. This roughness of the display is caused by the difference in the brightness (transmittance) of each pixel in the liquid crystal panel.

By the way, the resin black matrix is generally formed by a photolithography method, and usually has a tapered cross-sectional shape. As a result of the study by the present inventor, in the case of a high-definition liquid crystal panel, it was found that light leakage in the tapered portion of the resin black matrix, which was not affected by the liquid crystal panel having low definition, is the cause of the brightness difference for each pixel. It was. FIG. 9 is a diagram for explaining a transmission state of display light in a liquid crystal panel having a low definition, and FIG. 10 is a diagram for explaining a transmission state of display light in a liquid crystal panel having a high definition. The arrows shown in FIGS. 9 and 10 schematically show the light transmitted through the transparent substrate 11, and the thickness of the arrows corresponds to the magnitude of the amount of light. In FIGS. 9 and 10, a resin black matrix (light-shielding layer) 13A having a forward taper shape with a wider width on the side close to the transparent substrate 11 as a base is provided, which is less than the amount of light transmitted through the opening. , Indicates that there is light that passes through the tapered portion. As can be seen from the comparison between FIGS. 9 and 10, in the liquid crystal panel having high definition, the area ratio of the tapered portion of the black matrix (light-shielding layer) 13A to one pixel is large, and the light leakage in the tapered portion is large. .. On the other hand, in the patterning of the resin black matrix by the photolithography method, it is difficult to make the shape of the tapered portion for each pixel uniform in the entire liquid crystal panel.

The present invention has been made in view of the above situation, and provides a color filter substrate and a manufacturing method thereof suitable for preventing variations in brightness for each pixel, and a liquid crystal display device including the color filter substrate. It is intended to be provided.

(1) In one embodiment of the present invention, a transparent substrate, a plurality of color filter layers juxtaposed on the transparent substrate, and a plurality of adjacent color filter layers arranged on the transparent substrate are separated from each other. A color filter comprising a light-shielding layer, wherein the light-shielding layer is a cured resin product in which a photoresist is patterned, and has an eaves portion protruding in a direction parallel to the transparent substrate at an end on a side not in contact with the transparent substrate. substrate.

(2) Further, in an embodiment of the present invention, in addition to the configuration of (1) above, a color filter substrate having a thickness of the eaves portion of 0.5 μm or more.

(3) Further, in an embodiment of the present invention, in addition to the configuration of (1) or (2) above, a color filter substrate in which the arrangement interval of the light-shielding layers is 30 μm or less.

(4) In one embodiment of the present invention, the color filter substrate of the above (1), the above (2) or the above (3), the opposing substrate facing the color filter substrate, the color filter substrate and the opposing substrate A liquid crystal display device comprising a liquid crystal layer arranged between the two.

(5) One embodiment of the present invention is a method of manufacturing a color filter substrate having a light-shielding layer that separates a plurality of adjacent color filter layers on a transparent substrate, and a photoresist is placed on the transparent substrate. The step of arranging the photoresist, the step of exposing the photoresist with a saturated exposure amount, and the step of developing the exposed photoresist are included, and in the development step, the above-mentioned edge on the side not in contact with the transparent substrate is used. A method for manufacturing a color filter substrate, in which development is continued until an eaves projecting in a direction parallel to the transparent substrate is formed.

According to the present invention, it is possible to provide a color filter substrate and a method for manufacturing the same, which are suitable for preventing the occurrence of variation in brightness for each pixel, and a liquid crystal display device provided with the color filter substrate.

It is sectional drawing which showed the light-shielding layer which has a conventional forward taper shape. It is sectional drawing which showed the light-shielding layer which has a conventional reverse taper shape. It is sectional drawing which showed the light-shielding layer which has the eaves part in embodiment of this invention. It is a flow chart explaining the method of forming a light-shielding layer when a positive photoresist is used. It is a flow chart explaining the method of forming a light-shielding layer when a negative type photoresist is used. It is a graph explaining the correlation between the exposure amount and development time, and the shape of the obtained light-shielding layer. It is a graph which showed the result of the experiment which confirmed the correlation between the exposure time and the development time, and the variation of the transmittance in the display panel surface. It is a flow figure explaining the manufacturing method of a liquid crystal panel. It is a figure explaining the transmission state of the display light in the liquid crystal panel which does not have high definition. It is a figure explaining the transmission state of the display light in the liquid crystal panel with high definition.

Hereinafter, a color filter substrate, a liquid crystal display device, and a method for manufacturing the color filter substrate according to the embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and the design can be appropriately changed within a range that satisfies the configuration of the present invention.

The color filter substrate according to the embodiment of the present invention is a transparent substrate, a plurality of color filter layers juxtaposed on the transparent substrate, and the plurality of adjacent color filter layers arranged on the transparent substrate are separated from each other. The light-shielding layer is a cured resin product in which a photoresist is patterned, and has an eaves portion protruding in a direction parallel to the transparent substrate at an end on the side not in contact with the transparent substrate.

As the color filter layer, those conventionally known in the field of liquid crystal display devices may be used, for example, a photosensitive transparent resin containing a coloring material such as red (R), green (G), and blue (B). (Color resist) is used. Within the area (display area) where the pixels of the liquid crystal display device are arranged when the color filter substrate is viewed in a plan view, the color filter layer is arranged for each portion (pixel area) constituting the pixel, and the light-shielding layer is provided. It is preferable that the pixels are arranged so as to delimit the boundary of the pixel area.

The light-shielding layer is a layer formed in a pattern that separates a plurality of adjacent color filter layers by developing after exposing a photoresist (photosensitive resin), and is formed in a grid pattern by, for example, photolithography. It may be a formed black matrix (BM). The photoresist may be a positive type or a negative type.

The light-shielding layer in the present embodiment has an eaves portion (overhang portion) protruding in a direction parallel to the transparent substrate at an end on the side not in contact with the transparent substrate. By providing the eaves, it is possible to prevent light leakage that has occurred in the conventional light-shielding layer having a tapered shape, and as a result, it is possible to prevent the occurrence of variation in brightness for each pixel.

FIG. 1 is a cross-sectional view showing a light-shielding layer having a conventional forward taper shape, FIG. 2 is a cross-sectional view showing a light-shielding layer having a conventional reverse taper shape, and FIG. 3 is an embodiment of the present invention. It is sectional drawing which showed the light-shielding layer which has the eaves part in the form. In both the forward-tapered light-shielding layer 13A shown in FIG. 1 and the reverse-tapered light-shielding layer 13B shown in FIG. 2, the tapered portion is thin in the vertical direction, so that light shielding is insufficient and light is slightly emitted. To Penetrate. In the present specification, regarding the shape of the light-shielding layer, the shape in which the width on the side close to the transparent substrate 11 is widened is referred to as "forward taper shape", and the shape in which the width on the side close to the transparent substrate 11 is narrowed is referred to as "reverse taper". It is called "shape". The arrows shown in FIGS. 1 and 2 schematically show the light transmitted through the tapered portion. Further, particularly in the case of a high-definition display panel, it is difficult in terms of manufacturing technology to uniformly form the tapered shape of the light-shielding layer in each pixel in the surface of the color filter substrate. For this reason, conventionally, due to the uneven shape of the tapered portion, the transmittance (the amount of light that escapes) differs depending on the location in the display panel. However, in a display panel having a low resolution, the amount of light in the opening is much larger than that in the tapered portion, so that the influence of the variation in the leaked light in the tapered portion has not been a problem. However, in a display panel having a high resolution, since the opening is small, the influence of the leaked light in the tapered portion is large, and the difference in the brightness (transmittance) occurs for each pixel due to the variation in the amount of transmitted light in the tapered portion, so that the screen display is displayed. It will be visually recognized as roughness or unevenness. Therefore, in the present embodiment, as shown in FIG. 3, a light-shielding layer 13 having no tapered portion and having an eaves portion 14 is provided. The arrows shown in FIG. 3 schematically show the light blocked by the eaves 14. The light-shielding layer 13 having the eaves portion 14 can be formed by being exposed to a saturated exposure amount and being sufficiently developed, as will be described later. Since the light-shielding layer 13 of the present embodiment can sufficiently block light from the eaves portion 14, there is no difference in brightness (transmittance) due to variations in the amount of transmitted light in the tapered portion, and roughness and unevenness of the screen display are prevented. can do.

The light-shielding layer 13 having the eaves portion 14 has an end portion 13a on the side surface (lower bottom) in contact with the transparent substrate and an end portion 13b on the side surface (upper bottom) not in contact with the transparent substrate in the outline of the cross section. It has two corners 14a and 14b that bend discontinuously between them, and the area of the surface that does not contact the transparent substrate (length of the contour line) is larger than the area of the surface that contacts the transparent substrate (length of the contour line). It has the characteristic of being large. In addition, there may be three or more corner portions. On the other hand, the light-shielding layer 13B having an inverted tapered shape is formed by a straight line and / or a curved line in which the end portion of the lower base and the end portion of the upper base (tapered portion) are continuous in the contour line of the cross section. Therefore, it is different from the light-shielding layer 13 having the eaves portion 14.

In conventional photolithography, it has been common general knowledge to form a film having a forward taper shape so that an eaves shape is not formed. This is due to the difficulty of covering the film having the eaves with another film when trying to laminate another film on the film having the eaves, and the step existing at the end of the upper bottom or the like. This is because defects such as disconnection of the conductive pattern occur. In the case of the color filter substrate of the present embodiment, there is no risk of electrical defects due to disconnection of the conductive pattern laminated on the light-shielding layer 13, which causes the transmittance to vary in a high-resolution display panel. There is a great merit by eliminating the tapered part.

A preferred embodiment of the color filter substrate according to the above embodiment will be described below.

From the viewpoint of ensuring sufficient light-shielding performance, the thickness of the eaves portion 14 is preferably 0.5 μm or more.

The arrangement interval (width of the opening) of the light-shielding layer 13 may be 30 μm or less. According to the light-shielding layer 13 having the eaves portion 14 of the present embodiment, unlike the conventional light-shielding layer having a tapered portion, the amount of transmitted light is large even in a high-definition display panel in which the arrangement interval of the light-shielding layers 13 is set narrow. It is possible to suppress the difference in brightness (transmittance) due to variation.

The liquid crystal display device according to the embodiment of the present invention includes the color filter substrate, a facing substrate facing the color filter substrate, and a liquid crystal layer arranged between the color filter substrate and the facing substrate. ..

The facing substrate is not particularly limited as long as it is arranged to face the color filter substrate and holds a liquid crystal layer between the color filter substrate and the facing substrate. For example, it is conventionally known in the field of a liquid crystal display device. An active matrix substrate may be used.

The method for manufacturing a color filter substrate according to an embodiment of the present invention is a method for manufacturing a color filter substrate having a light-shielding layer that separates a plurality of adjacent color filter layers on the transparent substrate. A step of arranging the photoresist in the substrate, a step of exposing the photoresist at a saturated exposure amount, and a step of developing the exposed photoresist, and in the development step, the side not in contact with the transparent substrate. Development is continued until an eaves portion protruding in the direction parallel to the transparent substrate is formed at the end.

FIG. 4 is a flow chart for explaining a method for forming a light-shielding layer when a positive photoresist is used, and FIG. 5 is a flow chart for explaining a method for forming a light-shielding layer when a negative photoresist is used. is there. As shown in FIGS. 4 and 5, in order to form the pattern of the light-shielding layer 13, a cycle of film formation (coating), exposure, and development (etching) of the photoresist 12 is performed. For the positive photoresist 12, a photomask 50 having a light-shielding region 51 corresponding to a desired pattern of the light-shielding layer 13 is used, and the exposed portion 12A irradiated with light is dissolved in a developing solution and unexposed. Part 12B does not dissolve in the developer. On the other hand, for the negative photoresist, a photomask 60 having a light-transmitting region 61 corresponding to a desired pattern of the light-shielding layer 13 is used, and the exposed portion 12A irradiated with light is not dissolved in the developing solution.

FIG. 6 is a graph for explaining the correlation between the exposure amount and the developing time and the shape of the obtained light-shielding layer. The arrows in the figure represent the light incident on the light-shielding layers 13, 13A, and 13B, and the light is transmitted through the light-shielding layers 13A and 13B because the film thickness of the tapered portion is thin. Conventionally, as shown in (5) in FIG. 6, a forward taper shape having a taper angle of about 30 to 60 ° has been considered to be optimal. Since the light-shielding layers 13, 13A, and 13B are films for light-shielding purposes, it is difficult for light to reach a portion deeper than a certain film thickness, and it is difficult to insolubilize even if the exposure amount is increased (in the case of a negative type). When the amount of exposure that makes it difficult for light to reach even if the amount of exposure is increased is defined as the "saturated exposure amount", in the present embodiment, the light-shielding pattern (the eaves portion 14) to be retained is surely insoluble. In order to do so, after exposing with a saturated exposure amount and sufficiently curing, the part to be melted (the deep part) is surely removed by securing a sufficient development time, and the tapered part is prevented from being formed. As a result, the shape of the photoresist changes in the order of (9), (6), and (3) in FIG. 6, and finally the light-shielding layer 13 having the eaves portion 14 shown in FIG. 6 (3) is obtained. Be done. The exposure amount and development time differ depending on the material of the light-shielding layer used and the exposure device, but the exposure amount is preferably 1.5 times or more as compared with the case of forming the conventional forward taper shape, and the development time is set. It is preferably 1.5 to 2.0 times. As a result, the eaves portion 14 having less variation in shape can be formed.

FIG. 7 is a graph showing the results of an experiment for confirming the correlation between the exposure time and the development time and the variation in the transmittance in the display panel surface. In this experiment, a 3-inch display panel was used, and the variation with respect to the average value when the brightness was measured at 50 points in the panel was calculated. In the graph of FIG. 7, the conventional optimum exposure time and development time for obtaining the shape (5) in FIG. 6 are displayed as 100%. According to FIG. 7, it can be seen that the transmittance variation becomes smaller by extending the exposure time, and the transmittance variation becomes smaller by increasing the development time. If the transmittance variation is 1% or less, roughness and unevenness are difficult to see, and if it is 0.5% or less, it is not visible at all. The present inventor has confirmed that the transmittance variation is 1% or less according to the conditions of the exposure time and the development time in which the light-shielding layer having the eaves is formed.

The method for manufacturing a color filter substrate is performed by as many members as the number of members constituting the cycle of film formation, resist coating, exposure, development, etching, and resist peeling / cleaning, and laminating each member. However, since the light-shielding layer and the color filter layer are resists that exhibit photosensitivity, the cycle is short in that film formation and resist application are performed in the same step.

FIG. 8 is a flow chart illustrating a method for manufacturing a liquid crystal panel. In the example of FIG. 8, (1) formation of the light-shielding layer (black matrix) 13, (2) formation of the red color filter layer 15R, (3) formation of the green color filter layer 15G, and (4) formation of the blue color filter layer 15B. Formation, (5) formation of overcoat layer (flattening film) 16, (6) formation of photospacer (PS) 17 for cell thickness control, (7) attachment of color filter substrate and facing substrate (TFT substrate) 20 The liquid crystal panel is completed by performing the alignment and the formation of the liquid crystal layer 30 in this order. Before step (7), an alignment film (not shown) for liquid crystal alignment is formed on both the color filter substrate side and the TFT substrate side, and is subjected to alignment treatment (for example, rubbing). Further, the formation of the liquid crystal layer 30 in step (7) may be performed by sealing with the sealing material 40 after dropping the liquid crystal, or after forming the sealing material 40, the liquid crystal is sealed and sealed. It may be something to do.

When manufacturing a liquid crystal panel in the horizontal alignment mode, electrodes for applying a voltage to the liquid crystal layer 30 may be provided only on the TFT substrate side. On the other hand, when manufacturing a liquid crystal panel in the vertical orientation mode, electrodes for applying a voltage to the liquid crystal layer 30 are formed on both the color filter substrate side and the TFT substrate side, and before the formation of the photo spacer 17 in step (6). In addition, the electrode is formed.

The color filter substrate and the method for manufacturing the color filter substrate according to the embodiment of the present invention can be applied to all display panels using a light-shielding layer, and can be applied to a liquid crystal panel in a horizontal alignment mode or a liquid crystal panel in a vertical alignment mode. Not only, for example, a liquid crystal panel having a color filter on array (CF on Array) structure in a horizontal orientation mode, a liquid crystal panel having a color filter on array (CF on Array) structure in a vertical orientation mode, and an OLED panel. It may be applied to (organic EL panel).

According to the method for manufacturing a color filter substrate according to the embodiment of the present invention, the exposure amount is increased and the developing time is longer than the conventional photolithography conditions for forming a light-shielding layer having a forward taper or reverse taper shape. By doing so, it is possible to form an eaves portion in which a light-shielding function is ensured, and to reduce variations in the line width and shape of the light-shielding layer for each pixel. As a result, it is possible to suppress variations in brightness for each pixel, so that roughness and unevenness of the screen display can be prevented from being visually recognized.

11: Transparent substrate 12: photoresist 12A: exposed portion 12B: unexposed portion 13: light-shielding layer (black matrix)
13A: Forward-tapered light-shielding layer 13B: Reverse-tapered light-shielding layer 14: Eaves 15R: Red color filter layer 15G: Green color filter layer 15B: Blue color filter layer 16: Overcoat layer (flattening film)
17: Photospacer 20: Opposing substrate 30: Liquid crystal layer 40: Sealing material 50, 60: Photomask 51: Light-shielding area 61: Light-transmitting area

Claims (5)

With a transparent board
A plurality of color filter layers juxtaposed on the transparent substrate,
A light-shielding layer that is arranged on the transparent substrate and separates the plurality of adjacent color filter layers is provided.
The light-shielding layer is a cured resin product obtained by patterning a photoresist, and is a color filter substrate having an eaves portion protruding in a direction parallel to the transparent substrate at an end on a side not in contact with the transparent substrate. The color filter substrate according to claim 1, wherein the eaves have a thickness of 0.5 μm or more. The color filter substrate according to claim 1 or 2, wherein the light-shielding layer is arranged at an interval of 30 μm or less. The color filter substrate according to any one of claims 1 to 3 and
Opposing substrate facing the color filter substrate and
A liquid crystal display device including a liquid crystal layer arranged between the color filter substrate and the facing substrate. A method of manufacturing a color filter substrate having a light-shielding layer that separates a plurality of adjacent color filter layers on a transparent substrate.
The process of arranging the photoresist on the transparent substrate and
The step of exposing the photoresist at a saturated exposure amount and
Including the step of developing the exposed photoresist.
A method for producing a color filter substrate, which comprises continuing development until an eaves portion protruding in a direction parallel to the transparent substrate is formed at an end of the developing step on a side not in contact with the transparent substrate.

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