JP4617821B2 - LIQUID CRYSTAL DISPLAY DEVICE SUBSTRATE, LIQUID CRYSTAL DISPLAY DEVICE SUBSTRATE MANUFACTURING METHOD, AND PHOTO MASK USED FOR THE METHOD - Google Patents

Description

  The present invention relates to a vertical alignment (VA) type liquid crystal display (LCD), and more particularly to an alignment control protrusion used in an alignment division vertical alignment (MVA) type multi-domain vertical alignment (LCD) type LCD. And a substrate having a spacer, a manufacturing method thereof, and a photomask used therefor.

  MVA-LCD (Multi-domain Vertical Alignment-Liquid Crystal Display, alignment division vertical alignment type liquid crystal display device, see Patent Documents 1 and 2, Non-Patent Document 1) has a plurality of tilt directions of liquid crystal molecules in one pixel. The vertical alignment type liquid crystal display device which is controlled in this way and is capable of uniform halftone display in all directions, is said to be a liquid crystal display device having excellent contrast, viewing angle characteristics and response speed.

  FIGS. 1A and 1B are explanatory views schematically showing the operation of the MVA-LCD in its cross section. As shown in FIGS. 1A and 1B, a general MVA-LCD (10) includes a TFT side substrate (11) provided with alignment control protrusions (13) via liquid crystal molecules (15). And the color filter side substrate (12) provided with the alignment control protrusions (14). However, the alignment control protrusions (13) and the alignment control protrusions (14) are in alternate positions. It is like that.

  FIG. 1A shows a state when no voltage is applied, and when no voltage is applied, the liquid crystal molecules (15) are vertically aligned between the two substrates, but the alignment control protrusion (13) and the alignment control protrusions. The liquid crystal molecules in part (14) are slightly tilted due to the influence of the slopes of the protrusions. FIG. 1B shows a state when a voltage is applied. When a voltage is applied, the liquid crystal molecules on the slopes of the protrusions begin to tilt, and the liquid crystal molecules other than the tilted portions sequentially have the same orientation. That is, the alignment of liquid crystal molecules is controlled by providing protrusions instead of rubbing treatment.

  Therefore, it is necessary to add a new process to form such a pattern. When forming by a photolithography method, in general, a positive resist is used for forming alignment control projections, and a spacer is used for forming spacer columns. Uses negative resist. Although this method is excellent in sensitivity and patterning characteristics, it is necessary to create it in separate steps because of different resist materials, and the process such as replacement of resist solution and developer increases, time and cost. Reduction is an issue.

  In order to solve this problem, a method for collectively forming alignment control protrusions and spacer columns has been studied. As this method, for example, a method of differentiating the exposure amount by performing multiple exposures (see Patent Document 3). , A method in which at least two layers of the colored pixel layer and the light shielding layer are overlapped in advance to make the spacer column forming portion high (see Patent Document 4), and two photosensitive resin composition layers having different photosensitivity are stacked. A method of exposing with a wavelength selective mask (see Patent Document 5) has been reported. However, these use a plurality of masks, and the number of exposures is 2 times or more, so alignment during exposure is difficult, and it is difficult to maintain the height accuracy of the spacer column in order to overlap the colored pixel layers. There were problems such as an increase in the layer formation process.

Japanese Patent No. 2947350 Japanese Patent Laid-Open No. 11-248921 Electronic Journal October 1997 P.I. 33 JP 2002-236371 A Japanese Patent No. 3255107 JP 2003-248323 A

  The present invention has been made in order to solve the above-described problems. For a substrate used in a liquid crystal display device, the process of forming alignment control protrusions and spacer columns is simplified, and the time and cost are greatly reduced. An object of the present invention is to provide a substrate for a liquid crystal display device having excellent display quality, a method for producing the same, and a photomask that can be used for the production.

  As a result of studying various materials and processing methods in order to solve the above-mentioned problems, the present inventor has found that as a photomask used for exposure of the photosensitive resin composition layer, alignment control protrusions and spacer columns can be obtained in a single exposure. By using a photomask capable of forming both, specifically, by using a wavelength selective functional mask having at least two types of transmissive patterns, it becomes possible to collectively form alignment control protrusions and spacer columns, It has been found that the time and cost are greatly reduced, and the present invention has been achieved.

That is, the engagement Ru inventions in claim 1, a liquid crystal display device for holding the liquid crystal between the opposed substrate, method of manufacturing a substrate for a liquid crystal display device comprising at least an alignment control projection and the spacer pillars, Providing a photosensitive resin composition layer on a substrate; exposing and developing the photosensitive resin composition layer through one type of photomask to simultaneously form alignment control protrusions and spacer columns ; the photomask is a range transmittance of 20% to 60% of at least one wavelength transmissive patterns in 365 nm, and Ri der transmittance than 10% in 314 nm, the light completely transmissive portion, of the complete light-shielding portion otherwise, one or more with a photomask having a semi-transparent portion, the liquid crystal display device substrate manufacturing method of forming the material of the semi-transmissive portion is characterized in that it is a ITO thin film That.

  According to the present invention, it is possible to form the alignment control protrusions and spacer columns having different heights and shapes with the same material at the same time by one exposure, so that the process and material are reduced by half compared to the conventional method, Time and cost can be greatly reduced.

  In addition, according to the present invention, since the difference in height between the alignment control protrusion and the spacer column can be made sufficiently, even when these are formed on the color filter layer, the colored pixel layer is previously stacked on the light shielding layer to increase the height. Therefore, it is not necessary to increase the thickness, and therefore, batch formation is possible without reducing the height accuracy of the spacer column.

  In addition, by combining wavelength transmission patterns that optimize not only 365 nm but also 314 nm transmittance, it is possible to form alignment control projections that meet the finer required quality in a lump, and can be added to meet various specifications. A valuable liquid crystal display device substrate can be provided at low cost.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention relates to a method of manufacturing a substrate for a liquid crystal display device having at least alignment control protrusions and spacer columns, which constitutes a liquid crystal display device that sandwiches liquid crystal between opposing substrates, or a photomask used therefor, The present invention relates to a substrate for a liquid crystal display device and a liquid crystal display device manufactured by using the liquid crystal display device, and particularly to a liquid crystal display device used for an alignment division vertical alignment type LCD.

  The substrate used for the MVA-LCD is generally a color filter layer composed of a colored pixel layer and a light shielding layer (black matrix), and if necessary, a specific orientation control via a transparent protective layer and a transparent conductive layer. In order to form such alignment control protrusions and spacers, the alignment control protrusions are usually formed with a positive resist, followed by a negative resist. Form spacer pillars. However, in this method, it is necessary to repeat the photolithography processes of resist coating, exposure, and development twice, and it is unnecessary to replace the resist and developer and clean the line when manufacturing on the same line. Will also increase. Therefore, simplification of the process is highly desired from the viewpoint of cost reduction. Further, if it can be formed of the same resist, the amount of the chemical solution to be discarded can be reduced to about half, which is excellent in terms of environment.

  As a method for satisfying such a requirement, the present inventor has proposed that one type of photomask be used as the photomask in an image forming method in which a substrate provided with a photosensitive resin composition layer is exposed and developed through a photomask. Specifically, for wavelength control using a wavelength selective mask having at least two kinds of transmissive patterns, and when there is a color filter layer, a spacer column is formed at a corresponding position on the light shielding layer. It has been found that the protrusion and the spacer column can be formed with high accuracy by a single photolithography process.

  Hereinafter, in this specification, a liquid crystal display substrate in which a color filter layer including a colored pixel layer and a light shielding layer is provided on a light-transmitting substrate, and an alignment control protrusion and a spacer column are formed thereon is mainly described. Although described, this does not mean that the substrate for a liquid crystal display device or the liquid crystal display device according to the present invention must include a color filter layer.

The substrate constituting the substrate for a liquid crystal display device of the present invention is preferably a light-transmitting plate-like one, and is made of glass or plastic such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone or polyacrylate. A sheet or a film is mentioned.
In addition, since the heating process is performed after forming the alignment control protrusions and spacer columns, a glass substrate excellent in heat resistance is preferable, and further, a glass having a small coefficient of thermal expansion and excellent dimensional stability in the heating process. It is preferable to select.

In general, a color filter is formed by forming a black matrix (K, light-shielding layer) on a light-transmitting substrate, followed by red (R), green (G), and blue (B) colored pixel layers. When the liquid crystal is used for a liquid crystal, a transparent conductive layer and an alignment film layer are sequentially stacked. For example, the liquid crystal layer is disposed opposite to a counter substrate on which an electrode such as a thin film transistor is formed. This constitutes an LCD.
In this specification, the light shielding layer (black matrix) and the red, green, and blue colored pixel layers are collectively referred to as a color filter layer.

  The light shielding layer constituting the color filter layer can be formed using a known method. For example, a thin film of a metal or metal oxide such as chromium or titanium is formed on a substrate by a method such as sputtering, and then patterned by a technique such as etching. Alternatively, light-sensitive fine particles such as carbon black and metal oxides and a colorant such as a pigment or dye composed of a plurality of types are mixed in the photosensitive resin composition, and this is formed as a photosensitive resin composition layer on the substrate. Examples thereof include those formed by photolithography, but any method may be used in the present invention.

  The colored pixel layer is provided in the opening of the light shielding layer, and a pixel pattern composed of three primary colors, usually a red pixel pattern (R), a green pixel pattern (G), and a blue pixel pattern (B), is arranged in a desired shape. It is a thing. As the formation method, there are already known methods such as a pigment dispersion method, a dye method, an electrodeposition method, a printing method, a transfer method and a method of forming each pixel by ink jetting. In the present invention, any method is used. Also good.

  As an embodiment of the substrate having alignment control protrusions and spacer columns in the present invention, a configuration in which alignment control protrusions and spacer columns are provided on these color filter layers or transparent conductive layers, or color filter layers and transparent conductive layers. It is characterized by comprising a layer, a protrusion for alignment control and spacer columns, an alignment film layer in this order, or a plurality of layers provided with a protective film layer between any of these layers if necessary.

The transparent conductive film layer is an essential component for at least one of the substrates used for the liquid crystal display device, which sandwiches the liquid crystal with the opposing substrate. Normally, it is formed directly under an alignment film or alignment protrusion that regulates the alignment direction of the liquid crystal, and the behavior of the liquid crystal sandwiched between the substrates is controlled by transmitting an electric signal. Alternatively, it can be provided by vapor deposition or the like on the upper layer of the alignment protrusion.
The transparent conductive layer is made of a material that is transparent and conductive and can be formed into a thin film. Usually, an ITO (indium and tin composite oxide) film is used, and IZO (indium and zinc composite oxide) and SnO are used. _{2 A} (tin dioxide) film or the like is selected, and each is formed by a technique such as sputtering or vacuum deposition.

  The photosensitive resin composition layer used in the present invention is not particularly limited as long as it has a photosensitivity of at least 365 nm, but particularly preferably contains a photosensitive component having an absorption maximum at 365 nm or less. By using a combination of such a material and a wavelength selective mask, the difference in the exposure amount and the exposure wavelength between the alignment control protrusion forming portion and the spacer column forming portion becomes larger. Formation is easier. Examples of the material for forming such a photosensitive resin composition layer include a photosensitive resin composition comprising a photopolymerizable monomer, a photopolymerization initiator and a binder, a photosensitive resin composition comprising an azide compound and a binder, Among them, a photopolymerizable resin compound is particularly preferable because of the wide range of selection of the photosensitive wavelength. In addition, those capable of alkali development are preferable from the viewpoint of work safety and environmental performance.

  Next, a method for forming the alignment control protrusions and spacer columns of the present invention will be described. The photosensitive resin composition described above is applied to a bar coater on a substrate having a light-transmitting property or, if necessary, on a substrate on which a color filter layer, a transparent conductive layer, and a protective film layer are laminated by the method described above. The film is laminated using a known coating method such as an applicator, a wire bar, a spin coater, a roll coater, a slit coater, a curtain coater, a die coater, or a comma coater. Alternatively, the above-described photosensitive resin composition may be formed into a dry film by a known method, and this may be transferred and laminated on a substrate using a laminator.

  Thereafter, pattern exposure is performed by irradiating light through a wavelength selective mask having a predetermined pattern, development is then performed, and unnecessary portions are dissolved and removed, thereby forming alignment control protrusions and spacer columns in a lump.

The wavelength selective mask in the present invention is a photomask characterized by having at least one kind of semi-transmissive portion in addition to the light complete transmission portion and the complete light shielding portion. The semi-transmission part here is a part having a different transmittance depending on the wavelength in the range of 300 to 450 nm. Generally, a Cr thin film is used as a complete light-shielding portion of a photomask. For example, if the thickness of the Cr thin film is partially reduced or a Cr pattern is formed in a halftone dot pattern, only a portion of the Cr light is allowed to pass through. It becomes like this. However, in this case, since the transmittance changes almost uniformly in the range of 300 to 450 nm, there is no selectivity of the exposure wavelength even if the exposure amount can be controlled. Therefore, even if the height of the resist pattern obtained can be controlled, the shape cannot be controlled.
On the other hand, when an ITO thin film, a compound thin film containing Ti or W, or a compound thin film containing Ti or Mo is used instead of the Cr thin film as a semi-transmissive part forming material, a semi-transmissive part having different transmittance depending on the wavelength is formed. be able to. The wavelength selectivity of these thin films can be controlled depending on the material and the formation process, and thereby it is possible to collectively form resist patterns having different shapes as well as heights. In the present invention, it is preferable that the transmittance at 365 nm is high and the transmittance is low in the shorter wavelength range, particularly 20 to 60% at 365 nm, 20% or less at 335 nm, and 10% or less at 314 nm. Those are preferred.

  By using a wavelength-selective mask formed by combining a light transmissive part and a semi-transmissive part according to the height and shape of the pattern to be formed, it is possible to form patterns with different heights and shapes in a single exposure. Become. Specifically, for example, when the photosensitive resin composition is a negative type, the spacer column forming part is a completely light transmitting part, the alignment control protrusion forming part is a semi-transmitting part, and the part where nothing is left is a completely light shielding part. When the wavelength selective mask is used, the spacer forming portion is completely cured to the upper part of the photosensitive resin composition layer, so that a columnar resist pattern almost faithful to the mask pattern is formed, and the alignment control protrusion forming portion is A semicircular pattern having a lower height than the spacer column is formed. Furthermore, by using a wavelength selective mask having two or more types of semi-transmissive portion patterns having different transmittance characteristics, it is also possible to collectively form the alignment control protrusions with partially changed shapes and heights. .

  As the light source for exposure, a light source that emits light having a wavelength of 300 to 450 nm, for example, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a xenon lamp, a halogen lamp, or the like can be used. After exposure, an image faithful to the mask pattern can be obtained by developing with a predetermined developer. As the developer, an organic solvent system or an alkaline aqueous solution system is generally used, but an alkaline aqueous solution system is preferable from the viewpoint of ensuring work safety and environmental safety, and an inorganic alkaline system is particularly preferable. However, when an image is formed on the TFT array substrate, it is preferable to use an organic alkali developer because Na and K ions in the inorganic alkali aqueous solution cause contamination. Moreover, these can also mix well-known various additives, such as surfactant.

  In the present invention, by performing a heating step after the photolithography step, the curing of the alignment control protrusion and the spacer column is promoted to improve the adhesion to the substrate, and further, solvent resistance and chemical resistance are imparted. be able to. In addition, the alignment control projections cured at the semi-transmission part have a slightly lower curability than the spacer pillars cured at the completely light transmission part, so that the liquid crystal molecules become smooth due to heat shrinkage and reflow. It becomes possible to further improve the orientation of. The heating step may be carried out at a temperature and time at which the thermosetting component sufficiently reacts in a hot plate, a hot air furnace, a far-infrared furnace or the like, for example, at 200 to 250 ° C. for 15 to 100 minutes.

  Here, the alignment control protrusions are colored pixels on the transparent conductive film on the colored pixel layer in the liquid crystal display substrate provided with the color filter layer, or when the color filter layer is provided on the opposite substrate. It is formed on the transparent conductive film at a position corresponding to the layer, and the shape is preferably regular, such as a dot shape, a stripe shape, or a zigzag shape, and its cross section is semicircular, semielliptical, or triangular A polygonal shape such as The spacer column is formed on the transparent conductive film on the light shielding layer or on the transparent conductive film at a position corresponding to the light shielding layer of the opposing substrate, and the shape is generally a cylinder or a polygonal column.

  At least one of the substrates constituting the liquid crystal display device of the present invention is provided with an alignment film layer, which is different from the alignment control protrusion. For the alignment film layer, a negative liquid crystal compound is vertically aligned and a transparent and insulating material is used. Usually a polyimide resin is used. A polyimide resin solution, a polyamic acid solution, or the like is formed by a known coating method or printing method, and then fired.

  If necessary, the protective film layer provided on the color filter layer is a liquid crystal layer in order to flatten a step generated when the light shielding layer and the colored pixel layer are formed, or a component contained in the light shielding layer or the colored pixel layer Is required to be transparent. Examples of the material for forming the protective film layer include photocurable, thermosetting, light and thermosetting resin compositions, resin cured products such as epoxy, acrylic and polyimide, and inorganic compounds by sputtering and vapor deposition. Any material can be used as long as the object can be achieved. In consideration of the surface state of the color filter layer, it can be formed in the range of 0.5 to 3 μm.

  Hereinafter, embodiments of the present invention will be described with reference to specific examples, but the present invention is not limited to the examples described below. In addition, since the photosensitive resin composition layer used in the present invention is extremely sensitive to light, it is necessary to prevent exposure to unnecessary light such as natural light, and all operations should be performed under a yellow or red light. Needless to say.

  First, a black photosensitive resin in which carbon black is dispersed in an acrylic resin is applied onto a transparent substrate 21A made of 0.7 mm-thick alkali-free glass (OA-2: manufactured by Nippon Electric Glass Co., Ltd.) using a spinner. This was applied to form a black photosensitive resin composition layer, and patterning treatment such as exposure / development and heat treatment were performed to form a light shielding layer 22 having a width of 14 μm and a height of 1.3 μm.

  Next, a photosensitive resin in which a dianthraquinone pigment is dispersed in an acrylic resin is applied using a spinner to form a red photosensitive resin composition layer, and a patterning process such as exposure / development using a predetermined exposure mask Then, heat treatment was performed to form a red pixel layer 23R having a width of 100 μm and a film thickness of 1.3 μm. Similarly, a photosensitive resin in which a phthalocyanine green pigment is dispersed in an acrylic resin is applied using a spinner to form a green photosensitive resin composition layer, and a patterning process such as exposure and development using a predetermined exposure mask. Then, heat treatment was performed to form a green pixel layer 23G having a width of 100 μm and a film thickness of 1.3 μm. Similarly, a photosensitive resin in which a phthalocyanine blue pigment is dispersed in an acrylic resin is applied using a spinner to form a blue photosensitive resin composition layer, and a patterning process such as exposure and development using a predetermined exposure mask. Then, heat treatment was performed to form a blue pixel layer 23B having a width of 100 μm and a film thickness of 1.3 μm.

  Next, an indium oxide-based target was sputtered to form a transparent conductive film 24A having a thickness of 200 nm on the colored pixel layer 23 and the light shielding layer 22 made of red, green, and blue.

Next, a photosensitive resin composition having the following <Prescription 1> component is applied with a spinner to form a 4.2 μm-thick photosensitive resin composition layer on the transparent conductive film 24A. 150 mJ / cm ² is applied to the photosensitive resin composition layer using a wavelength selective mask in which the light completely transmissive part, the alignment control protrusion forming part is a semi-transmissive part made of an ITO thin film, and the other part is a complete light shielding part. Were exposed and cured. Here, the transflective portion had a transmittance at 365 nm of 55%, a transmittance at 335 nm of 20%, and a transmittance at 314 nm of 6%.

Photosensitive resin composition <Prescription 1>
Styrene / benzyl methacrylate / methacrylic acid copolymer 100 parts by weight (molar ratio 10/60/30, molecular weight 34000)
-Dipentaerythritol hexaacrylate 100 parts by weight-Irgacure 907 (Ciba Specialty Chemicals) 12 parts by weight-Diethylthioxanthone 2 parts by weight-Leveling agent 0.2 parts by weight-Cyclohexanone 506 parts by weight

  Next, after developing with an alkali developer, heat treatment is performed in an oven at 240 ° C. for 60 minutes, and spacer columns 26 are formed on the transparent conductive film 24A on the light shielding layer 22 and are colored red, green, and blue. An alignment control protrusion 25 was formed on the transparent conductive film 24A on the pixel layer 23 to obtain the color filter 20 for a liquid crystal display device of the present invention.

  When the shape of the obtained pattern was observed, the spacer column had a 10 μm square, a height of 3.5 μm, a height accuracy of less than 0.1 μm, and a trapezoidal cross section, while the alignment control protrusion had a stripe shape having a width of 10 μm. The height of 1.5 μm and the semicircular cross section sufficiently satisfy the required characteristics.

  An alignment film is formed on both the color filter 20 for the liquid crystal display device of the present invention and the array substrate 30 on which the transparent conductive film 24B serving as the liquid crystal driving element array is formed on the transparent substrate 21B, and the alignment film forming surface is on the inside. Thus, the peripheral part was sealed and bonded together to produce a liquid crystal cell. Furthermore, liquid crystal was sealed in a liquid crystal cell to obtain a color liquid crystal display device 40 of the present invention. When an image was observed by applying a voltage to this, the image was high-definition, there was no unevenness in the image, and the viewing angle was excellent.

It is explanatory drawing which shows the board | substrate for MVA-LCD which formed the processus | protrusion for orientation control. It is explanatory drawing which shows the board | substrate for MVA-LCD which formed the protrusion for alignment control and the spacer pillar by this invention.

Explanation of symbols

10 ... MVA-LCD
DESCRIPTION OF SYMBOLS 11 ... TFT side board | substrate 12 ... Color filter side board | substrate 13 ... Protrusion 14 for orientation control ... Protrusion 15 for orientation control ... Liquid crystal molecule 20 ... Color filter 21A, 21B, 27A, 27B for liquid crystal display devices ... Transparent substrate 22 ... Light shielding layer ( Black matrix)
23R ... Red pixel layer 23G ... Green pixel layer 23B ... Blue pixel layer 23 ... Colored pixel layers 24A, 24B, 28A, 28B ... Transparent conductive film 25 ... Alignment control protrusion 26 ... Spacer column 29 ... Color filter layer 30 ... Array substrate 40 ... Color liquid crystal display device

Claims (1)

In the method of manufacturing a substrate for a liquid crystal display device having at least alignment control protrusions and spacer columns, which constitutes a liquid crystal display device that sandwiches liquid crystal between the opposing substrates, a step of providing a photosensitive resin composition layer on the substrate And exposing and developing the photosensitive resin composition layer through one type of photomask to simultaneously form alignment control protrusions and spacer columns , wherein the photomask has at least one wavelength transmission property. ranges transmittance of 20% to 60% pattern in 365 nm, and Ri der transmittance than 10% in 314 nm, the light completely transmitting unit, in addition to the complete light-shielding portion, having one or more of the semi-transmissive portion A method for producing a substrate for a liquid crystal display device, wherein the substrate is a photomask and the material for forming the translucent portion is an ITO thin film .

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