JP5866997B2 - Photomask and color filter manufacturing method - Google Patents

Description

  The present invention relates to a color filter used for a color liquid crystal display element, and more particularly to a color filter provided with a fixed spacer for controlling a cell gap of a liquid crystal display cell and a photomask used for manufacturing the color filter.

In an active matrix liquid crystal display element, generally, a pixel electrode substrate in which a switching element such as a thin film transistor (TFT) is formed for each pixel on a glass substrate, and a colored transparent pixel in which a pixel pattern is arranged on another glass substrate. A color filter substrate that covers and forms a uniform transparent electrode is disposed opposite to the liquid crystal. This element controls the shutter function using the change in the liquid crystal alignment of each pixel by the switching operation of each TFT element.
In recent years, alignment regulations that control the alignment of liquid crystals in VA liquid crystals, called vertical alignment, in line with higher image quality such as larger size, higher definition, faster response, wider viewing angle and higher contrast of liquid crystal display devices An MVA method in which a protrusion is formed and an IPS (In Plane Switching) method liquid crystal display element in which an electric field for driving a liquid crystal is applied in the horizontal direction of the pixel have been adopted.

  In a liquid crystal display element using TFT, a TFT substrate which is a pixel electrode substrate and a color filter substrate are arranged to face each other with a predetermined interval, and these substrates are bonded by a sealing agent in which reinforcing fibers are mixed with epoxy resin or the like. It is configured by pasting together. Liquid crystal is sealed between the color filter substrate and the TFT substrate, but if the distance between the color filter substrate and the TFT substrate is not accurately maintained, the thickness of the liquid crystal layer will differ, resulting in a difference in the optical rotation characteristics of the liquid crystal. This causes a phenomenon in which coloring is caused by or a partial color unevenness occurs and the image is not displayed correctly. Therefore, in the cell forming process, a large number of spheres made of resin, glass, alumina or the like having a diameter of 2 μm to 10 μm, which are also referred to as bead spacers, or a rod-like body of the same size are dispersed and spacers are provided. (Holding interval) is maintained. Since this spacer is a transparent particle, if there is a spacer in the pixel with liquid crystal, light leaks through the spacer during black display, and between the substrates in which the liquid crystal material is sealed Due to the presence of the spacers, the alignment of the liquid crystal molecules in the vicinity of the spacers is disturbed, causing light leakage at this part, resulting in a problem that the contrast is lowered and the display quality is adversely affected.

  As a technique for solving such a problem, for example, a photosensitive resin is used, and a protrusion having a fixed spacer function is formed on a light shielding layer between color filter pixels by a photolithography method of partial pattern exposure to development. A method has been proposed (see Patent Documents 1 and 2). The fixed spacer is also called a photo spacer or a columnar (post) spacer, and is abbreviated as PS. In many cases, a plurality of PSs formed by being selectively positioned by a photosensitive resin are regularly arranged on a color filter substrate using a photolithography method. Patent Documents 3 to 6 disclose techniques for forming the above-described fixed spacers or protrusion patterns such as the above-described MVA-type alignment regulating protrusions by a photolithography technique.

It is important that the fixed spacer sufficiently exhibits the function of holding the liquid crystal cell gap in a certain range against various external pressures. The liquid crystal cell often receives strong pressure from the outside even after the cell forming process. Therefore, it is required to improve the strength and elastic properties of the material constituting the fixed spacer so that the fixed spacer does not easily collapse even under such strong pressure.
Further, if the total cross-sectional area of the columnar fixed spacers in the cell plane is small, the gap between the substrates is difficult to be uniform in the cell forming process, and color unevenness or the like is likely to occur in the liquid crystal display device. Furthermore, when an excessive load is locally applied, color unevenness or the like is likely to occur in the liquid crystal display device. Therefore, it is necessary to make the pressure resistance of the cells determined by the cross-sectional shape and arrangement density of the columnar fixed spacers above a certain level together with the strength and elastic characteristics of the material constituting the above-mentioned fixed spacers.

If the cross-sectional area of the columnar fixed spacer is large and the pressure resistance is high, the gap between the substrates can be kept uniform in the cell forming process, but vacuum bubbles are easily generated in the liquid crystal cell due to the excessive pressure resistance. For example, when the liquid crystal volume shrinkage occurs at a low temperature, if the cell gap cannot sufficiently follow the shrinkage, an abnormal phenomenon called low-temperature foaming occurs due to fluctuations in internal pressure, thereby degrading the display quality.
As a method for solving this problem, Patent Document 7 describes a method in which a columnar fixed spacer (sub-spacer) having a lower height than a columnar fixed spacer (main spacer) that holds a gap between substrates is also formed. ing. The above-mentioned method of providing the sub-spacer is effective for adjusting the pressure from the outside by setting the lower limit cell gap according to the height of the sub-spacer as well as the support of the cell gap to compensate for the insufficient pressure resistance only by the main spacer. It is meaningful to easily adjust the cell gap as needed.

The main spacer and the sub-spacer have a circular or polygonal cross-sectional shape that is horizontal to the substrate, and the overall shape often uses a columnar pattern in which the upper bottom is narrower than the lower bottom.
In forming the main spacer and the sub-spacer, it is possible to sequentially produce two patterns having different heights in separate steps, but the manufacturing process becomes longer due to the repetition of the photolithography method, and the product becomes longer. It is disadvantageous to supply high quality at low cost. Therefore, for the purpose of shortening the process, an attempt has been made to simultaneously realize patterns of different heights at once by using the same photosensitive resin and devising a photomask pattern. Specifically, regarding the control of the thickness of the thickly applied photoresist film, an intermediate exposure amount between a region that provides a sufficient exposure amount and a region that shields light is provided, and the height of the protrusion is made at an intermediate level. If this method is used, a pattern of sub-spacers lower than the main spacer can be formed together with the main spacer.
Further, Patent Document 8 describes a method of forming three types of alignment spacer projections, a main spacer, a sub-spacer, and an MVA, using a photomask having a semi-transmissive halftone film having different light transmittance. Yes.

  On the other hand, for the purpose of forming a liquid crystal cell having a uniform cell gap in the surface without trouble in the cell forming process, there is a proposal to provide a dummy pattern equivalent to the main spacer at the end of the color filter substrate. Is formed such that the height direction position of the zenith portion of the dummy pattern at the end portion is lower than the height direction position of the zenith portion of the main pattern of the effective portion. This is because even if the height of the dummy pattern itself is the same as that of the main spacer, there is no thickness of each layer of the color filter on the planar position of the edge part which becomes the base for providing the dummy pattern at the edge part. This is because the position in the height direction of the zenith portion of the main spacer becomes lower than the position in the height direction of the zenith portion of the main spacer. In order to prevent the above problem, as a method of aligning the height direction of the pattern zenith in the photomask, the height of the main spacer itself in the effective surface of the color filter is made smaller than the height of the dummy pattern itself. A method of providing a step has been proposed (see Patent Document 9).

Japanese Patent Laid-Open No. 10-48636 JP-A-8-262484 JP 9-258192 A Japanese Patent Laid-Open No. 11-248921 JP 2001-201750 A Japanese Patent Laid-Open No. 2001-108813 Japanese Patent No. 3925142 JP 2009-151071 A JP 2006-330545 A

  In a color filter substrate incorporated in a liquid crystal display element, a halftone mask (Patent Document 8) or a stepped photo is used as a photomask to be used for the purpose of controlling the height of different types of fixed spacers depending on the planar arrangement position of the fixed spacers. The use of a mask (Patent Document 9) has already been proposed. However, in the case of using a photomask with a step, the fixed spacer of the effective portion projected by the normal pattern provided low on the photomask surface in order to increase the exposure gap in the proximity exposure (proximity) method, It is not easy to set the height of the spacer pattern to be formed low in a freely controlled manner compared to the dummy pattern at the end projected by the normal pattern provided high on the photomask surface in order to reduce the size. Absent.

  In contrast, in the case of using a halftone mask, the exposure amount passing through the halftone film can be directly controlled by appropriately setting the light transmittance of the halftone film. It is easy to control the height freely. However, when the main spacer and the sub-spacer are formed at a time using a halftone mask, depending on the size of the sub-spacer, the upper bottom portion of the sub-spacer becomes a concave shape, which causes light leakage due to liquid crystal orientation disorder and sub-space. Deterioration of the elastic properties of the spacer may occur. 3A and 3B show a protrusion formed of a negative type material made of (a) a photomask 30 using a conventional halftone film 36 and a photomask 30 manufactured by a proximity exposure method and (b) a photocurable resin. It is a schematic cross section for demonstrating an example of the color filter 40 which was made. The height of the sub-spacer 46 formed by reducing the exposure amount by the halftone film 36 is controlled to be lower than that of the adjacent main spacer 45 formed by being subjected to the full transmission exposure through the opening 35 on the surface. However, it is liable to be inferior in shape such as a shape in which the upper bottom is recessed due to photocuring with an insufficient exposure amount.

  In addition, in the case where an alignment regulating protrusion formed lower than the main spacer is provided using the same photomask as the sub-spacer, a defect may occur in liquid crystal alignment control due to a defective shape of the protrusion. The concave shape of the sub-spacer and the alignment regulating protrusion can be generally improved by widening the exposure gap during exposure by the proximity exposure method in the spacer or protrusion forming process, but it is sufficient for the main spacer formed at the same time. When the exposure gap at the time of giving the exposure amount becomes excessively large, there arises a problem that the height variation of the main spacer is deteriorated. For this reason, it has been difficult to improve practically when a plurality of types of protruding patterns having different heights are simultaneously formed.

  The present invention is proposed in view of the above-mentioned problems, and the problem to be solved by the present invention is to appropriately project a plurality of types of protruding patterns having different heights by an exposure process in a single photolithography method. It is to provide a photomask for simultaneously forming while maintaining a high height and shape.

As means for solving the above-mentioned problems, the invention according to claim 1 is characterized in that a plurality of types of protrusion-shaped patterns having different heights are used to manufacture protrusions having different heights on the same surface side of the exposure target substrate. Photomask corresponding to the formation of a pattern,
A step is provided on the pattern forming side of the transparent substrate, and a mask pattern for forming a protruding pattern (sub-spacer) excluding the highest protruding pattern (main spacer) is provided on the lower side of the step. The photomask is characterized in that the mask pattern provided on the lower side is formed as a halftone film in order to form an appropriate shape in which the upper bottom portion of the sub-spacer is not recessed .

The invention according to claim 2 is a method for producing a color filter, wherein a plurality of types of protruding patterns having different heights are formed by a single photolithography process using a photocurable photosensitive resin. a method of manufacturing a color filter, which comprises using a photo-mask according to claim 1 during the exposure photolithography process.

  The present invention is a photomask for use in manufacturing a plurality of types of protruding patterns having different heights on the same surface side of an exposure target substrate, and corresponding to the formation of protruding patterns having different heights. The mask pattern for forming the projection pattern excluding the pattern is provided in the opening of the photomask with a semi-transparent halftone film, and the mask pattern using the halftone film is the highest projection pattern that does not use the halftone film Since it has a transparent substrate surface that is lower than the mask pattern corresponding to pattern formation, multiple types of protruding patterns with different heights are maintained at the appropriate height and shape by one exposure process in photolithography. A photomask for simultaneous formation can be provided.

  In addition, by applying the photomask of the present invention to the manufacture of a fixed spacer composed of a main spacer and a sub-spacer in a color filter for a liquid crystal display element, the height of each spacer is optimally maintained and a good shape is obtained. Since the color filter can be provided, in a liquid crystal display element incorporating the color filter, the load resistance can be improved without causing a display defect due to low-temperature foaming.

It is a schematic cross section for demonstrating an example of a structure of the photomask of this invention in order of formation. It is a schematic cross section for demonstrating an example of a structure of the color filter of this invention. It is a schematic cross section for demonstrating the conventional photomask (a) and an example of the color filter (b) manufactured using it. It is a schematic cross section which shows an example of the manufacturing method of the color filter of this invention. It is a schematic cross section for demonstrating an example of a structure of the liquid crystal display element of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining an example of the configuration of the photomask of the present invention in the order of formation.
Hereinafter, a case where a fixed spacer including a main spacer and a sub-spacer having a height lower than that of the main spacer is simultaneously formed on the color filter as a processing target will be described. Generally, a plurality of types of protruding patterns having different heights are used. A similar function can be obtained with a similar configuration with respect to a photomask used in manufacturing the substrate on the same surface side of the substrate to be exposed.

In FIG. 1A, a transparent substrate 1 of a photomask can be a glass substrate such as quartz glass having excellent flatness, optical uniformity, surface hardness, thermal stability, chemical resistance and the like. If the pattern forming side of the transparent substrate 1 is the front surface and the opposite surface on which the pattern is not formed is the back surface 14, the high surface 11 and the low surface 12 can be selectively formed by providing the step 13 on the surface. Here, the high surface refers to the surface of the region where the transparent substrate 1 is thick, and the low surface refers to the surface of the region where the transparent substrate 1 is thin.
The step 13 is formed by thinning the original plate thickness of the transparent substrate 1 only at a specific location. There are a wet etching method and a dry etching method as the methods, and wet etching is considered in consideration of flatness of the processed portion. Is preferred. A positive resist is applied to a quartz glass substrate serving as a base material for the photomask, and only the portion where the substrate thickness is reduced by etching is exposed and developed by drawing to expose the base material surface. Next, etching is performed with a hydrofluoric acid solution using a positive resist left as a high surface 11 on the substrate surface as a mask to form a step 13 and a low surface 12 appearing as a result, and then a resist pattern is formed. Removal with a special stripping solution yields a transparent substrate 1 with a step.

  Next, a light shielding film 5 composed of a chromium oxide film, a multilayer of chromium film and a chromium oxide film is formed on the processed surface of the stepped transparent substrate by vacuum deposition, sputtering, etc., and a resist is formed on the light shielding film by a spin coating method or the like. Is applied to form a resist layer, and a resist pattern is formed by performing patterning processing by a photolithography method such as pattern drawing and development processing by an electron beam drawing apparatus. In electron beam exposure, when pattern exposure is performed on resist layers formed in regions having different substrate thicknesses, the position (focus) of the exposure surface can be adjusted more easily than in the case of batch exposure of light. Thereafter, the light-shielding film 5 is selectively etched with a dedicated etching solution using the resist pattern as a mask, and the resist pattern is removed with a dedicated stripping solution, whereby the light-shielding film 5 on the stepped transparent substrate 1 is predetermined. A high surface opening 15 and a low surface opening 16 are respectively formed at positions (see FIG. 1B). Next, a halftone film 6 made of chromium oxide is formed on the entire surface, a resist is applied by a spin coat method or the like, a resist layer is formed, and patterning processing such as pattern drawing and development processing is performed by an electron beam drawing apparatus. Then, a resist pattern is formed so as to cover the halftone film on the opening 15 on the high surface with the resist opening, and cover the halftone film on the opening 16 on the low surface with the resist. Using the resist pattern as a mask, the halftone film is selectively etched with a dedicated etchant, and the resist pattern is removed with a dedicated stripper to make the high surface opening 15 a fully transmissive opening and low. A photomask 10 of the present invention is obtained in which the opening 16 on the surface is a region in which the halftone film 6 is formed in a semi-transmissive opening (see FIG. 1C).

FIG. 2 is a schematic cross-sectional view for explaining an example of the configuration of the color filter of the present invention.
As shown in FIG. 2, this color filter is obtained by adding two types of columnar fixed spacers having different heights to a color filter having a basic function as a color filter used in a liquid crystal display element.
That is, in the color filter 20 shown in FIG. 2, a light blocking black matrix 22 and generally three colors of red, green, and blue are selectively provided on a transparent substrate 21 of a color filter that generally uses low expansion glass or the like. After the colored transparent pixels 23, 24, and 25 arranged in a plane are sequentially formed by photolithography, an overcoat layer 26 is formed by coating. If necessary, a transparent electrode layer is formed on the entire surface of the overcoat layer 26 by a vacuum deposition method, a sputtering method, or the like, but is omitted in the drawing. Further, as two types of columnar fixed spacers having different heights, a main spacer 27 and a sub-spacer 28 are formed simultaneously for the above-mentioned purpose. As described above, the sub-spacer 28 is 0.3 to 0.8 μm lower than the main spacer 27 in order to easily adjust the cell gap as needed against the external pressure. Form about 0.5 μm lower.

  FIG. 4 is a schematic cross-sectional view showing an example of the method for producing the color filter of the present invention for the exposure process. In order to form the color filter 20 of the present invention in the configuration shown in FIG. 2, the photocurable photosensitive resin 8 is applied by laminating the black matrix 22, the colored transparent pixels 23, 24, 25 and the overcoat layer 26. To do. Thereafter, the main spacer 27 ′ and the sub-spacer 28 ′ indicated by broken lines are simultaneously formed as two types of columnar fixed spacers having different heights selectively depending on the photosensitive resin material. Proximity exposure using the photomask 10 is performed, and a color filter is manufactured through a series of photolithography processes such as subsequent development. Hereinafter, the exposure process will be described in detail.

After accurate alignment between the photomask 10 and the color filter 20, uniform and parallel irradiation light 7 is directed toward the photomask pattern surface from a light source (not shown) installed on the back surface 14 side of the photomask 10. Proximity exposure with a minimum exposure gap of about 50 μm is performed. The light having a large exposure amount that is totally transmitted through the opening 15 on the high surface of the photomask 10 and the light having a small exposure amount that is partially transmitted by the halftone film 6 provided in the opening portion on the low surface are formed by the photosensitive resin 8. By irradiating a predetermined position, the main spacer 27 'and the sub-spacer 28' can be finally left.
That is, a projection excluding the highest projection pattern in a photomask corresponding to the formation of projection patterns with different heights, used when manufacturing a plurality of types of projection patterns with different heights on the same surface side of the exposure target substrate. A mask pattern for forming the sub-spacer 28 ', which is a pattern, is provided in the opening portion of the photomask with the semi-transmissive halftone film 6, and the mask pattern using the halftone film 6 is not used with the halftone film. By exposing using a photomask on the transparent substrate surface provided lower than the opening 15 which is the mask pattern corresponding to the highest protrusion pattern formation, multiple types of protrusion patterns with different heights are exposed. They can be simultaneously manufactured on the same side of the target substrate.
In this example, the plurality of types of protruding patterns having different heights include a fixed spacer including a main spacer 27 ′ and a sub-spacer 28 ′ having a height lower than that of the main spacer. The photomask 10 provided with the provided halftone film is effective as a photomask used when manufacturing the color filter 20 having the fixed spacer.

Further, the mask pattern for forming the sub-spacer is a semi-transmissive halftone film having an i-line transmittance of 10 to 30%, and the mask pattern for forming the main spacer is a totally transmissive film obtained by removing the light shielding film. It is desirable that the opening has a mask pattern for forming the sub-spacer on the surface of the transparent substrate that is 20 to 100 μm lower than the mask pattern for forming the main spacer.
When proximity exposure is performed using the photomask of the present invention, it is practical to use a high-pressure mercury lamp as a light source. The main wavelength of irradiation light emitted from the high-pressure mercury lamp is g-line (wavelength 436 nm),
Although they are h-line (wavelength 405 nm) and i-line (wavelength 365 nm), i-line is most effectively used to form a fine pattern such as a fixed spacer of a color filter. The amount of exposure to irradiate the sub-spacer 28, which is 0.3 to 0.8 μm lower than the main spacer 27, is extremely good if it is less than 10% of the sufficient amount of i-line exposure to irradiate the main spacer. In this case, the half-tone film 6 has an i-line transmittance of 10 to 10% because a desired difference from the main spacer cannot be obtained in the height of the sub-spacer to be formed. 30% is desirable.
Further, the amount of the step for providing the photomask pattern for forming the sub-spacer lower than the pattern for forming the main spacer is preferably 20 to 100 μm from the results of the examples described later.

  As described above, by performing proximity exposure using the photomask of the present invention, a plurality of types of protruding patterns having different heights can be formed at the same time. Therefore, one-time photolithography using a photo-curable photosensitive resin. In the process, a fixed spacer composed of a main spacer and a sub-spacer can be added to a conventional color filter. The obtained color filter optimally holds the height of each fixed spacer and can have a good shape. Therefore, in the liquid crystal display element incorporating the color filter described later with reference to FIG. The load bearing characteristics can be improved without causing display defects.

Note that the mechanism by which a plurality of types of protruding patterns having different heights can be simultaneously formed in good shape by performing proximity exposure using the photomask of the present invention is considered as follows.
First, in the mask opening area and the exposure gap of a comparative example using a photomask having no step described in the examples described later, the exposure intensity at the center of the pattern is weaker than the pattern edge due to light diffraction and interference. If it is a fully transmissive aperture with no halftone, the saturation sensitivity will be reached even if the exposure intensity is somewhat weak due to light interference. The influence of interference is easily reflected in the shape of the sub-spacer, which is a low projection pattern. If the exposure gap is set appropriately in accordance with the sub-spacer, the shape defect due to light interference can be eliminated. However, if the exposure gap is too large, the line width and height variation of the main spacer will be adversely affected. Effect.
That is, the exposure gap suitable for forming the sub-spacer is often different from the exposure gap suitable for forming the main spacer. If priority is given to the formation of the main spacer, the shape of the sub-spacer is deteriorated. If priority is given to this, the main spacers will vary in height and line width. In a conventional photomask, the main spacer and the sub-spacer are always formed with the same exposure gap, and depending on the specifications of the fixed spacer, it may not be possible to form the sub-spacer without a shape defect. On the other hand, in the present invention, the exposure gap between the main spacer and the sub-spacer is set with a certain difference by etching the transparent base material of the photomask and providing a step in the pattern portion corresponding to the sub-spacer formation. Therefore, the exposure gap for setting one photomask at the time of exposure can be optimally set for each of the main spacer and the sub-spacer.
Further, according to the present invention, even in a specification in which in-plane variation or shape defect occurs in the conventional method, the main spacer can be formed in a state where the in-plane variation of the main spacer is good and there is no shape defect of the sub-spacer or alignment control protrusion. it can.

FIG. 5 is a schematic cross-sectional view for explaining an active drive type TN type transmissive liquid crystal display element 60 as an example of the configuration of the liquid crystal display element of the present invention.
The main spacer 27 and the sub-spacer 28 are generally provided on the color filter 20 side as described above. Although the main spacer 27 and the sub-spacer 28 are not provided on the color filter 20 side, they can be provided on the pixel electrode substrate 50 opposite to the color filter 20 constituting the liquid crystal cell structure, but a resin material is used. It is often more convenient in the manufacturing process to provide the color filter 20 after the series of processing. Regardless of which side the main spacer 27 and the sub-spacer 28 are on, the liquid crystal display element 60 has a fixed spacer for controlling the cell gap and is generally sandwiched between liquid crystal alignment films 62 provided on both sides to drive alignment. A cell structure closed with a sealant 63 for sealing the liquid crystal 61 to be formed can be formed.

  In the liquid crystal display element 60 of FIG. 5, the color filter 20 is formed on the surface of the transparent substrate 21 facing the inside of the cell, the black matrix 22, the colored transparent pixels 23, 24, 25, and the overcoat layer 26, if necessary. A transparent electrode layer 29 is provided, and in addition, a liquid crystal alignment film 62 is provided. A polarizing plate 64 is attached to the surface outside the cell. The pixel electrode substrate 50 facing the color filter 20 has a liquid crystal alignment film 62 in addition to the active drive switching element 52 such as TFT and the pixel electrode 53 on the surface of the transparent substrate 51 facing the cell. A polarizing plate 65 having a rotation angle orthogonal to the cell external polarizing plate 64 on the color filter side is provided on the surface outside the cell, and further on the outer side for liquid crystal display. A backlight (not shown) is provided as an illumination light source.

Examples of the photomask of the present invention and a color filter produced using the photomask will be described below.
First, a specific example will be described with respect to a method of manufacturing a color filter component before forming a fixed spacer which is a protruding pattern.

A black matrix is formed on a transparent substrate. Thereafter, color filter layers for each color of the red layer, the blue layer, and the green layer are formed.
Next, an overcoat layer is formed as a protective film on the front surface. For the overcoat, a thermosetting transparent resin was used, applied by a die coating method, dried under reduced pressure, and baked at 230 ° C. for 30 minutes.

As the colored resist for forming the colored layer, one having the following composition was used.
The following were used as pigments used in the colored resist.
[Red Pigment 1 (R-1)]
Red pigment 1 (CI Pigment Red 254, “IR Gap HOR RED B-CF” manufactured by BASF; R-1) was used.
[Red Pigment 2 (R-2)]
Red pigment 2 (CI Pigment Red 177, “CROMOPHTAL RED A2B” manufactured by BASF; R-2) was used.
[Green Pigment 1 (G-1)]
500 parts of green pigment (CI Pigment Green 36, Toyo Ink Mfg. Co., Ltd. “LIONOL GREEN 6YK”; G-1), 1300 parts of sodium chloride, and 270 parts of diethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) And kneaded at 70 ° C. for 3 hours. Next, this mixture is poured into about 5 liters of warm water, heated to about 70 ° C. and stirred with a high speed mixer for about 1 hour to form a slurry, then filtered and washed to remove sodium chloride and diethylene glycol, It was dried at 80 ° C. for 24 hours to obtain 496 parts of a salt milled pigment.
[Yellow Pigment 1 (Y-1)]
Yellow pigment (CI Pigment Yellow 138, “PALIOTOL YELLOW K0961HD” manufactured by BASF) 200
Parts, 1,500 parts of sodium chloride, and 270 parts of diethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.), 1 gallon kneader (manufactured by Inoue Seisakusho) made of stainless steel, and kneaded at 60 ° C. for 6 hours. Next, this mixture is poured into about 5 liters of warm water, stirred in a high speed mixer for about 1 hour while being heated to about 70 ° C. to form a slurry, filtered, washed with water to remove sodium chloride and diethylene glycol. And dried at 80 ° C. for 24 hours to obtain 196 parts of a salt milled pigment.
[Blue Pigment 1 (B-1)]
Blue pigment 1 (CI Pigment Blue 15: 6, “LIONOL BLUE ES” manufactured by Toyo Ink Co., Ltd.) was used.
[Purple Pigment 1 (V-1)]
Purple Pigment 1 (CI Pigment Violet 23, “LIONOGEN VIOLET RL” manufactured by Toyo Ink Manufacturing Co., Ltd.) was used.
[Preparation of acrylic resin solution]
The preparation of the acrylic resin solution used in the examples will be described. The molecular weight of the resin is a weight average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography).
A reaction vessel was charged with 370 parts of cyclohexanone, heated to 80 ° C. while injecting nitrogen gas into the vessel, and a mixture of the following monomer and thermal polymerization initiator was added dropwise at the same temperature over 1 hour to carry out the polymerization reaction. .
Methacrylic acid 20.0 parts Methyl methacrylate 10.0 parts n-Butyl methacrylate 35.0 parts 2-Hydroxyethyl methacrylate 15.0 parts 2,2'-azobisisobutyronitrile 4.0 parts paracumylphenol ethylene oxide modification Acrylate 20.0 parts ("Aronix M110" manufactured by Toa Gosei Co., Ltd.)
After completion of the dropwise addition, the mixture was further reacted at 80 ° C. for 3 hours, then 1.0 part of azobisisobutyronitrile dissolved in 50 parts of cyclohexanone was added, and the reaction was further continued at 80 ° C. for 1 hour, An acrylic resin solution was obtained. The weight average molecular weight of this acrylic resin was about 40,000.
After cooling to room temperature, about 2 g of the resin solution was sampled and heat-dried at 180 ° C. for 20 minutes, the non-volatile content was measured, and cyclohexanone was added to the previously synthesized resin solution so that the non-volatile content was 20 wt%. An acrylic resin solution was prepared.
[Preparation of pigment dispersion]
A mixture having the composition (weight ratio) shown in Table 1 below was uniformly stirred and mixed, then dispersed with an Eiger mill for 2 hours using zirconia beads having a diameter of 0.5 mm, filtered through a 5 μm filter, and pigment dispersion RP -1, GP-1, and BP-1.

[Preparation of colored composition]
The mixture (weight ratio) shown in Table 2 below is stirred and mixed to be uniform, and then filtered through a 1 μm filter, and RR-1 (red) and GR-1 (green) which are colored compositions of each color. ) And BR-1 (blue).

Specific examples of the compositional elements in Table 2 are shown below.
Monomer: Trimethylolpropane triacrylate (Shin Nakamura Chemical "NK Ester ATMPT")
Photoinitiator: 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one ("Irgacure 907" manufactured by BASF)
Sensitizer: 4,4′-bis (diethylamino) benzophenone (“EAB-F” manufactured by Hodogaya Chemical Co., Ltd.)
Organic solvent: cyclohexanone

[Colored layer formation and overcoat layer formation]
Using the colored composition obtained as described above, pixels of each color were formed in regions partitioned by a 2.0 μm-thick black matrix formed in advance on a transparent substrate.
That is, RR-1 which is a red coloring composition was apply | coated to the transparent substrate by die coating so that it might become a finished film thickness of 1.5 micrometers. Next, after drying at 90 ° C. for 3 minutes, the light from a high-pressure mercury lamp was irradiated at 100 mJ / cm ² through a stripe photomask for pixel formation, and developed with an alkali developer for 60 seconds. Then, it hardened | cured by baking for 30 minutes at 230 degreeC, and the red pixel was obtained. At this time, the film thickness of the red layer on the black matrix was 0.65 μm. The finished film thickness means the film thickness after hardening for 30 minutes at 230 ° C. or the height of the color layer.
Next, in the same manner, GR-1, which is a green coloring composition, is applied by die coating so that the finished film thickness is 1.5 μm, dried at 90 ° C. for 5 minutes, exposed through a photomask, and developed. After that, a green pixel was obtained by hardening at 230 ° C. for 30 minutes. At this time, the film thickness of the green layer on the red layer was 0.6 μm.
Further, BR-1 which is a blue coloring composition is applied by die coating so that the finished film thickness becomes 1.5 μm in the same manner as in the case where red pixels and green pixels are formed. After drying for a minute, exposure through a photomask, development, and hardening at 230 ° C. for 30 minutes to form a blue pixel with a finished film thickness of 1.8 μm at a position adjacent to the green and red pixels did. At this time, the film thickness of the blue layer on the green layer was 0.5 μm.
In this way, a color filter having red, green, and blue pixels on the transparent substrate was obtained. The alkaline developer has the following composition.
Sodium carbonate 1.5% by weight
Sodium bicarbonate 0.5% by weight
Anionic surfactant (Kao Perillex NBL) 8.0% by weight
90.0% by weight of water
An overcoat layer or a transparent electrode layer is formed on the color filter in which the pixels of these three colors are formed according to the design of the liquid crystal display device, and a spacer is formed thereon by a method described later.

[Formation of fixed spacer]
For Example 1, a negative photoresist was applied to a substrate having a black matrix, a colored layer, and an overcoat layer with a spinner, and the coating amount was adjusted so that the finished film thickness was 3.5 μm. Formed. After drying under reduced pressure and pre-baking, a photomask base material having a 50 μm depression step, a semi-transparent film (half-tone film) light-shielding part having an i-line transmittance of 15.0%, and a light-transmitting part Exposure was carried out using a photomask according to the invention. As can be discriminated by appearance, the mask opening for the main spacer is a square with a side of 8 μm, and the opening for the sub-spacer on which the halftone film is formed is a regular octagon with a diameter of an inscribed circle of 14 μm. Proximity exposure was performed with a gap amount between the high surface of the mask for the main spacer and the exposed surface being 50 μm, an exposure illuminance of 40 mW / cm ² , and an exposure amount of 100 mJ / cm ² . The design conditions and exposure gap amount of the photomask are shown in the column of Example 1 in Table 3.
The main spacer is exposed through the translucent part, and the sub-spacer lower than the main spacer is exposed through the semi-transparent film (halftone film), developed with an inorganic alkaline developer, and cleaned. As a result of baking at 230 ° C. for 30 minutes in an oven, the size of the fixed spacer and the state evaluation of the columnar shape shown in Example 1 of Table 4 were obtained.
For Examples 2 to 8 and Comparative Examples 1 to 9, as shown in Table 3, various photomask design conditions, that is, any one of the conditions of the step of the dent, the mask opening size, and the halftone transmittance were carried out. A fixed spacer was formed in the same manner as in Example 1 except that a mask different from that in Example 1 was used and the size of the exposure gap was changed.

Each of the comparative examples is an example using a photomask manufactured by a conventional method.
Table 4 shows the results of measuring the height and line width (unit: μm) of the main spacer and sub-spacer of the color filter produced in the examples and comparative examples, and confirming the shape of the sub-spacer. The line width of the spacer is the bottom line width when measured with a microscope in a plane view. Further, the height variation 3σ of the main spacer is a variation in height when 20 points in the color filter plane are measured. The shape of the sub-spacer was observed at an angle of 60 ° with a scanning electron microscope, and the determination was made based on the presence or absence of dents and interference fringes. A circle indicates that the shape is good, and a cross indicates that the shape is bad.

From the above results, the photomask pattern for simultaneously forming a plurality of types of protrusion-like patterns having different heights on the same surface side in the range of the photomask design conditions and the exposure gap in this example and the comparative example is the same plane. When it is provided above, the variation in the height of the higher protrusion pattern formed by using it increases, or the shape of the lower protrusion pattern becomes defective, and the pattern formation surface of the photomask becomes defective. It has been proved that the above-mentioned problems can be overcome by forming with a height difference.
By using the photomask of the present invention, it is possible to improve the occurrence of sub-spacer shape defects or main spacer height variations in the conventional method, provide a good color filter, and a liquid crystal display incorporating the same In the element, the load bearing characteristics can be improved without causing display defects due to low-temperature foaming.

DESCRIPTION OF SYMBOLS 1, 31 ... Transparent base material 5 of photomask ... Light shielding film 6 ... Halftone film 7 ... Irradiation light 8 ... Photosensitive resin 10, 30 ... Photomask 11 ... High surface 12 ... Low surface 13 ... Surface step 14 ... Back surface 15 ... High surface opening 16 ... Low surface openings 20 and 40 ... Color filters 21, 41 .. Color filter transparent substrates 22, 42 ... black matrix 23, 24, 25, 43 ... colored transparent pixels 26, 44 ... overcoat layers 27, 45 ... main spacers 28, 46 ... Sub-spacer 29 ... transparent electrode layer 35 ... surface opening 36 ... halftone film 50 ... pixel electrode substrate 51 ... transparent substrate 52 ... switching element 53 ... pixel electrode 60 ... Liquid crystal display element 61 And LCD 62 ... liquid crystal alignment film 63 ... sealant 64, 65 ... polarizer

Claims (2)

A photomask corresponding to the formation of protrusion patterns having different heights, which is used when manufacturing a plurality of kinds of protrusion patterns having different heights on the same surface side of the exposure target substrate,
A step is provided on the pattern forming side of the transparent substrate, and a mask pattern for forming a protruding pattern (sub-spacer) excluding the highest protruding pattern (main spacer) is provided on the lower side of the step. A photomask comprising a halftone film for forming the mask pattern provided on the lower side into an appropriate shape that does not dent the upper bottom portion of the sub-spacer . A plurality of types of projecting patterns having different heights, a color filter manufacturing method of forming by one photolithography process using a photo-curing type photosensitive resin, to claim 1 during the exposure photolithography process A method for producing a color filter, comprising using the photomask described above.