JP2012088640A - Color filter substrate for ips (in-plane switching) system, and liquid crystal display device employing ips system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart an antistatic function to a color filter substrate for a liquid crystal display device employing an IPS system without using a transparent conductive film.SOLUTION: The color filter substrate for an IPS system comprises a transparent substrate 1, a black matrix 2 having conductivity and color pixels 3 formed on the substrate, and a transparent insulating layer 4 covering the surface, in which a part of the black matrix 2 is exposed outside the transparent insulating layer 4. The black matrix 2 is made of a metal or contains conductive carbon black.

Description

  The present invention relates to a color filter substrate used for a liquid crystal display device, and more particularly to a color filter substrate provided with antistatic properties.

  A color filter formed by applying a photolithographic method or an inkjet method pattern forming technique using a colored photosensitive resin or a non-photosensitive resin has a heat resistance of 250 ° C. or more, light resistance, high definition, It has excellent transparency and is used in various liquid crystal display devices in recent years.

  However, in both the photolithography method and other methods, a color filter film is formed with a resin composition on a transparent substrate. In this case, since the process cannot be controlled at high humidity, the process is electrostatically charged. In particular, as the substrate size increases, it becomes easier to be charged, and in extreme cases, the glass may adhere to the temperature control plate and cause conveyance failure.

  In addition, it is desirable to use a thin glass substrate for weight reduction, but if it is too thin, cracks are likely to occur during the process, resulting in an increase in the deflection of the glass substrate, resulting in a decrease in alignment accuracy during exposure. is there.

  In addition, even if there is no problem in transportation, the quality of a panel assembled with cells using a charged substrate tends to cause uneven cell gap control spacer beads due to the electrostatic charge, causing display unevenness defects and defective products. The rate that is high.

  In addition, electrostatic charging increases the adhesion of foreign matter, which also reduces the yield. In extreme cases, the transistor on the opposite side of the active matrix substrate may be deteriorated. In order to prevent display unevenness defects and maintain good transportability in the process, processes such as antistatic and neutralization are very important in the production of color filters and liquid crystal display devices.

  A normal liquid crystal alignment mode in a liquid crystal display device is twisted nematic alignment, but a lateral electric field driving method (in which a liquid crystal is rotated in a plane parallel to the substrate surface by applying a voltage parallel to the substrate surface in a different mode) IPS method). This IPS method has a feature that the viewing angle can be widened. However, since an electrode is not provided on the color filter side and the electrode is placed only on the substrate side on which a driving element such as a TFT is formed, an external electric field is applied from the color filter substrate side. Has a problem that the display tends to adversely affect the display.

  Regarding the provision of an antistatic function to an IPS color filter substrate, a technique of forming a transparent conductive film on the back side of the color filter substrate is disclosed (Patent Document 1). In this technique, since a transparent conductive film is formed on the back surface, harmful external electric fields can be blocked without affecting the display. Since a transparent conductive film can be directly formed on a glass substrate, the substrate temperature can be increased and there is no degassing from the underlayer compared to forming a transparent conductive film on a polarizing film or the like to be attached to the back surface of the color filter substrate. There are advantages. As a similar technique, there is a technique for attaching a film on which a transparent conductive film is formed (Patent Document 2).

However, in order to form the transparent conductive film on one surface of the glass substrate, it is necessary to use the surface on which the color filter is formed as the transport surface, so there is no dirt or scratches due to transport and processing of the transparent conductive film. There is a problem that it is easy to stick. In terms of process, a reverse mechanism is required between the front and back of the glass substrate, which requires a large amount of capital investment and extra space, which may be impossible in some cases. Moreover, even if it says that a transparent conductive film has a high light transmittance, the disadvantage that the transmittance | permeability falls on the whole glass substrate surface is unavoidable.

Japanese Patent Laid-Open No. 10-293207 JP 7-318878 A

  Therefore, an object of the present invention is to provide an antistatic function to a color filter substrate for an IPS liquid crystal display device without using a transparent conductive film.

  In order to achieve the above object, according to the first aspect of the present invention, a conductive black matrix and colored pixels are provided on a transparent substrate, the surface thereof is covered with a transparent insulating layer, and a part of the black matrix is transparent. The IPS color filter substrate is characterized by being exposed to the outside of the insulating layer.

  The invention according to claim 2 is the color filter for IPS system according to claim 1, wherein the black matrix is made of metal or is a resin-type black matrix containing conductive carbon black. It is a substrate.

  According to a third aspect of the present invention, there is provided an IPS liquid crystal display device using the color filter substrate.

According to the present invention, an antistatic function and a charge removal ability can be imparted to a color filter substrate using an existing apparatus and without making a new capital investment.
In the color filter substrate thus obtained, the color filter forming surface does not touch the conveying device when forming the color filter. Therefore, the production yield of the color filter substrate can be improved.
In addition, since the electrostatic charge is small during the cell assembling process, the deterioration of the thin film transistor can be reduced and the display unevenness defect in the liquid crystal panel can be reduced.
Further, since a film such as a conductive film is not formed on the back surface, there is an effect that the degree of freedom in processing the back surface is increased. In particular, when forming a color filter or the like, it is possible to use a glass substrate having a sufficient thickness that causes less trouble in the process. Thereafter, the back surface is etched to make a thin plate, and a light and highly accurate color filter substrate can be manufactured.

(A)-(e) is process drawing explaining the outline of the manufacturing process of the color filter substrate which becomes this invention.

  Hereinafter, the present invention will be described with reference to FIGS.

As a method for forming the colored pixels 3 (color filter) and the black matrix 2 on the transparent substrate 1, a pigment dispersion method can be used. In the pigment dispersion method, a plurality of colored layers (black, red, green, blue, etc.) are formed into a pixel shape by patterning a coating layer of a colored photosensitive resin in which a color material such as an organic pigment is dispersed by a regular photolithography method. It is a method of forming. Although the color order of the black matrix 2 and the plurality of colored pixels 3 is not particularly limited, the colored pixels 3 are sequentially formed after forming the pattern of the black matrix 2 for convenience of alignment. In addition to the pigment dispersion method, an inkjet method can also be applied.

  The black matrix 2 has a thickness in the range of 1 to 3 μm and a width in the range of 5 to 150 μm, and the film thickness (thickness) of the red pixel, the green pixel, and the blue pixel is in the range of 1.3 to 3.5 μm ( It depends greatly on the composition of the colored photosensitive resin and the coating method.) Typically, the thickness of the black matrix is about 1.5 μm, the thickness of the red layer is about 1.8 μm, the thickness of the green layer is about 1.5 μm, the thickness of the blue layer is about 1.2 μm, and the transparent insulating layer 4 The thickness is about 1.5 μm.

  If the size of the colored pixel is set to 24 μm × 54 μm and the vertical and horizontal pitches are set to 93 μm, the black matrix occupancy is about 45%. In this case, the conductivity of the black matrix is 0.0863Ω · It is desirable that there be about cm. The conductivity can be achieved by setting the thickness of the black matrix to about 1.1 μm or more.

  When the metal is a black matrix, the metal film may be a single-layer film, a metal oxide / metal two-layer film with improved low reflection characteristics, or a metal oxide with improved low reflection characteristics. A three-layer film such as / metal / metal oxide may be used. As the metal, chromium, nickel and the like are preferably used. These metal films can be patterned by etching using a photoresist and an acidic etchant.

  First, as shown in FIG. 1, a transparent substrate 1 such as glass is prepared (FIG. 1A). Use a transparent substrate with a thickness that does not cause exposure errors due to problems during transport and deflection. As a substrate other than glass, a substrate having a flat surface such as a silicon substrate, a polycarbonate substrate, a polyester substrate, an aromatic polyamide substrate, a polyamideimide substrate, a polyimide substrate, an Al substrate, or a GaAs substrate may be used.

  An alkali developable black resin composition for forming a black matrix using carbon black having conductivity as a coloring material is prepared and applied, for example, by a slit coating method, and then heated as necessary, for example, at 100 ° C. for 3 minutes. Then, volatile components such as a solvent are dried (prebaked). Next, using a predetermined mask, exposure is performed using an ultra-high pressure mercury lamp as a light source, then alkali development is performed with, for example, an aqueous sodium carbonate solution, washing and drying, and baking is performed at 230 ° C. for 1 hour, for example, to form a black matrix 2 (FIG. 1B).

  As a method for applying the colored resin composition, known methods such as a spray coating method, a spin coating method, a roll coating method, and a slit coating method can be used.

  As a light source of active light used for exposure, light having a wavelength of 300 to 450 nm can be used. For example, in addition to the above ultra-high pressure mercury lamp, light emitted from a mercury vapor arc, carbon arc, xenon arc, or the like. Can be used.

  In the development, an aqueous solution such as sodium carbonate or sodium hydroxide can be used as an alkali developer, and an organic alkali such as dimethylbenzylamine or triethanolamine can also be used. Moreover, an antifoamer and surfactant can also be added to a developing solution.

The optical density (OD value) depending on the thickness of the formed black matrix 2 is preferably used in the range of 3.0 to 6.0. If it is less than 3.0, sufficient display contrast cannot be obtained when used in a black matrix of a liquid crystal display, and backlight light leaks. In addition, when the value is larger than 6.0, sufficient light-shielding properties can be obtained, but the pigment concentration becomes high and the shape tends to overhang when forming a pattern.
The term “depending on the thickness” means the optical density of the thickness that is not reduced per unit thickness (1 μm).

  Next, on the transparent substrate 1 on which the black matrix 2 is formed, the dry photosensitive film thickness is adjusted to a desired film thickness by a coating method such as spray coating, spin coating, slit coating, or roll coating. Apply to. The red photosensitive resin layer dried as necessary is exposed to active energy rays through a photomask having a predetermined pattern using, for example, an ultrahigh pressure mercury lamp as a light source.

  Thereafter, the unexposed portion is developed with an alkaline developer, for example, a 2, 5% aqueous sodium carbonate solution, washed thoroughly with water, and further washed with water and dried. In this way, as shown in FIG. 1, patterned red colored pixels are obtained on the transparent substrate 1 on which the black matrix 2 is formed. An antifoaming agent or a surfactant can be added to the developer as necessary. After the development, for example, heat treatment is performed at 230 ° C. for 60 minutes to perform main curing (post-bake). By repeating this until a pixel portion having a desired number of colors is formed, patterning of the colored layer is performed, for example, the green colored layer patterned using the green photosensitive composition is replaced with the blue photosensitive composition. A blue colored layer is obtained that has been patterned. In this way, the color pixel 3 arranged in a predetermined pattern on the transparent substrate 1, for example, the red color pixel, the green color pixel, and the blue color pixel, and the black matrix 2 that shields light from each adjacent color layer is provided. A color filter layer can be obtained (FIG. 1C).

  Next, the unevenness between the colored pixels 3 is relaxed on the colored pixels 3 and a transparent insulating layer 4 for preventing the pigment from eluting into the liquid crystal is applied, or a silicon dioxide film is formed by sputtering. (FIG. 1 (d)). As a result, a color filter substrate including the conductive black matrix 2 can be obtained.

  In the present invention, since the transparent conductive film is not formed on the back surface, the glass substrate can be thinned by glass etching on the back surface. If a protective film is stuck on the color filter and put into a hydrofluoric acid solution for glass etching, only the back surface can be etched. If the protective film is peeled off, a thin and light color filter substrate can be obtained.

  At the glass substrate end 5, as shown in FIG. 1 (e), which is a top view, the end of the conductive black matrix is exposed to the air and is not covered with the transparent insulating layer 4. is necessary. The exposed end of the black matrix 2 is grounded to prevent charging.

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Conductive black matrix 3 ... Colored pixel 4 ... Transparent insulating layer 5 ... Edge of glass substrate

Claims (3)

  For an IPS system, wherein a conductive black matrix and colored pixels are provided on a transparent substrate, the surface thereof is covered with a transparent insulating layer, and a part of the black matrix is exposed to the outside of the transparent insulating layer Color filter substrate.   2. The color filter substrate for an IPS system according to claim 1, wherein the black matrix is made of a metal or is a resin-type black matrix containing conductive carbon black.   An IPS liquid crystal display device using the color filter substrate.

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