JP2005099393A - Color filter substrate and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the degradation of display quality caused by occurrence of unevenness by preventing an active element from defectively operating owing to light transmitted through a light shielding layer and light reflected by the light shielding layer. <P>SOLUTION: A color filter substrate 10 has a transparent substrate 1, the light shielding layer (BM) which is formed on the transparent substrate 1 and arranged opposite the active element (TFT), and color filters 2R and 2B of at least two colors which are formed on the transparent substrate 1. The color filters 2R and 2B of the two colors are laminated on the BM. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color filter substrate. The present invention also relates to a display device such as a TFT (Thin Film Transistor) type liquid crystal display device using a color filter substrate.

  FIG. 7 is a cross-sectional view schematically showing a conventional color liquid crystal display device. The color liquid crystal display device shown in FIG. 7 includes a color filter substrate 100 in which a color filter 2 is formed on a glass substrate 1, a TFT substrate 20 in which TFTs as active elements are formed on a glass substrate 3, and both substrates 100. , 20 and the liquid crystal layer 30. The color filter substrate 100 is formed with a light shielding layer, that is, a BM (black mask or black matrix) for optically separating the red, green, and blue sub-pixels and shielding the TFTs.

  However, as shown in FIG. 7, the light BL from the backlight may be reflected by the BM and enter the TFT channel. Alternatively, light incident from the viewer side may pass through the BM and enter the TFT channel. When external light is incident on the channel of the TFT, a current is generated by photoexcitation, and charges are accumulated, thereby deteriorating the retention characteristics of the TFT. That is, the OFF current characteristics of the TFT deteriorate. When the current generated by the photoexcitation has a local non-uniformity, unevenness called “mist” is generated in the display, and the display quality is lowered.

  For example, Patent Document 1 discloses a liquid crystal display device in which light shielding with respect to a TFT is ensured. In the liquid crystal display device shown in FIG. 1 of Patent Document 1, a black photoresist is selectively etched to form a first protrusion 38 </ b> A of a black matrix 38 on the TFT 20. Further, the color filter substrate 13 is formed with a second protrusion 50 in which red, green, and blue color filters 46R, 46G, and 46B are stacked at a position facing the first protrusion 38A. Yes. As a result, light shielding to the TFT 20 is ensured, and malfunction of the TFT 20 due to external light can be prevented (see paragraphs [0040], [0059], [0060] and [0064] of Patent Document 1).

JP-A-7-281195

  However, Patent Document 1 assumes a BM on TFT method in which BM is formed on the TFT substrate side, and BM is formed on the TFT element on the TFT substrate side. Since this method is different from the conventional general method, a new process is required for manufacturing a color filter substrate and a TFT substrate. Specifically, in the liquid crystal display device of Patent Document 1, the BM formed on the TFT element on the TFT substrate side and the laminated color filter formed on the TFT light shielding portion on the color filter substrate side are matched. In addition, it has a role of a spacer for controlling the cell gap. Therefore, the sum of the height to the top of the BM formed on the TFT element on the TFT substrate side and the height to the top of the laminated color filter formed on the TFT light shielding portion on the color filter substrate side is defined as the cell gap. Strict control is required to accommodate.

  In the liquid crystal display device described in Patent Document 1, since the BM is not formed on the color filter substrate, the document discloses a problem that light from the backlight is reflected by the BM and enters the TFT channel. Does not suggest.

  One of the objects of the present invention is to prevent malfunction of the active element by increasing the light blocking ability with respect to the light transmitted through the BM, that is, to suppress the fog caused by the transmitted light. Another object of the present invention is to suppress fog caused by backlight light reflected by the BM.

  In the present invention, by providing color overlap with two color filters on the BM, the spectrum in the visible region is absorbed, and the light blocking ability for light transmitted through the BM and reflected light from the BM is increased. For example, by superimposing two colors of the three color filters used in the picture element portion on the TFT light shielding portion, a color superposition having a sufficient light shielding capability is formed on the TFT light shielding portion.

  The color filter substrate of the present invention is a color filter substrate disposed opposite to an element substrate on which an active element having a semiconductor layer is formed, and is formed on the transparent substrate and opposed to the active element. And at least two color filters formed on the transparent substrate, and two color filters of the at least two color filters are disposed on the light shielding layer. Are stacked. The at least two color filters may be three color filters of red, green and blue.

  The two color filters stacked on the light shielding layer may be the same color filter as the color filter adjacent to the light shielding layer. Alternatively, the color filter of one color among the two color filters stacked on the light shielding layer may be a color filter having a different color from the color filter adjacent to the light shielding layer.

  The two color filters stacked on the light shielding layer may be red and blue color filters.

  The display device of the present invention includes an element substrate on which an active element having a semiconductor layer is formed, a color filter substrate of the present invention in which the light-shielding film is disposed at a position facing the active element, the element substrate, and the color And a display medium layer interposed in the gap of the filter substrate. The “display medium layer” is a layer whose light transmittance is modulated by a potential difference between electrodes facing each other, or a layer that emits light by current flowing between electrodes facing each other. The display medium layer is, for example, a liquid crystal layer, an inorganic or organic electroluminescence (EL) layer (white light emitting layer), or the like.

  According to the present invention, it is possible to suppress the fogging due to the incidence of external light, the reflection of backlight light, the multiple reflection inside the liquid crystal cell, and the like, and the deterioration of display quality can be prevented. In Patent Document 1, it is the BM formed mainly on the TFT element on the TFT substrate side that prevents malfunction of the TFT element due to external light, and the color overlap formed on the TFT light shielding portion on the color filter substrate side. Is for improving the light shielding property and securing the cell gap. In the present invention, the color overlap formed on the TFT light-shielding portion on the color filter substrate side is intended to ensure light-shielding to the TFT elements and prevent deterioration of display quality. In other words, the purpose of forming the color overlap is to provide the TFT light-shielding portion with a sufficient light-shielding capability that does not transmit external light and does not cause reflection. Therefore, in Patent Document 1, depending on the cell gap, the height to the top of the BM formed on the TFT element on the TFT substrate side and the top of the color overlap formed on the TFT light-shielding portion on the color filter substrate side. However, in the present invention, this is not necessary.

  Further, according to the present invention, since a method for forming the BM on the color filter substrate side is premised as before, the color filter forming material is used, and the color overlap is formed together with the formation of each color filter. Therefore, in the manufacture of the TFT substrate and the color filter substrate, there is no need for a special process for forming a color overlay, and there is no need to change the manufacturing process. Thus, the manufacturing process is simple.

  According to the present invention, it is possible to prevent the malfunction of the active element due to the light transmitted through the light shielding layer (BM) and the light reflected by the light shielding layer, so that it is possible to prevent deterioration in display quality due to fog.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a transmissive liquid crystal display device will be described as an example. However, the display device of the present invention can be widely applied to display devices having a color filter substrate and an active element substrate. For example, the present invention can be applied to a reflection type or a transflective liquid crystal display device, an organic EL display device, and an inorganic EL display device. In the following embodiments, an active matrix type liquid crystal display device using a TFT (Thin Film Transistor) as a switching element will be described. The liquid crystal display device of the present invention is a display in which an active element having a semiconductor layer is formed. Can be widely applied to the device.

  FIG. 1 is a plan view schematically showing one pixel of the liquid crystal display device of the present embodiment. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line III-III in FIG. The pixel is composed of red, green, and blue sub-pixels.

  The liquid crystal display device of this embodiment includes a color filter substrate 10, a TFT substrate 20 on which a TFT having the semiconductor layer 4 is formed, and a liquid crystal layer 8 sandwiched between both substrates. On the glass substrate 3 of the TFT substrate 20, a plurality of scanning wirings (not shown) extending in the row direction, a plurality of signal wirings 7 extending in a column direction substantially orthogonal to the row direction, and the scanning wirings and signal wirings 7 are arranged. TFTs (in other words, arranged in a matrix) provided in the vicinity of the intersection with the. Note that the column direction and the row direction merely indicate that the two directions are relatively different, and do not define the horizontal direction or vertical direction of the substrate, but specify the longitudinal direction or short direction of the substrate. Not a thing.

  The TFT is connected to the gate electrode 5 connected to the scanning wiring, the gate insulating film 6 covering the gate electrode 5, the semiconductor layer 4 formed on the gate electrode 5 through the gate insulating film 6, and the signal wiring 7. And a drain electrode 8 connected to a pixel electrode (not shown). In FIG. 2 and FIG. 3, reference numeral 7 is assigned to the signal wiring and the source electrode.

  The color filter substrate 10 includes a glass substrate 1, a BM formed on the glass substrate 1, and red, green, and blue color filters 2R, 2G, and 2B. The color filters 2R, 2G, and 2B are arranged so as to face the red, green, and blue sub-pixels. BM is a light-shielding layer disposed at a position facing the TFT region and the region that separates the red, green, and blue sub-pixels. Light incident from the glass substrate 1 side enters the TFT semiconductor layer 4 (channel). Prevents incidence.

  Two color filters are stacked on the BM. In this embodiment, a red color filter 2R and a blue color filter 2B are stacked on the BM. FIG. 4 is a graph showing a transmitted light spectrum in the visible light region by each color filter. As shown in FIG. 4, when the transmitted light spectrum by the red filter 2R and the transmitted light spectrum by the blue filter 2B are superimposed, the transmitted light can be substantially blocked.

  FIG. 5 is a graph showing color filters of respective colors and OD (Optical Density) values when these are combined. A 7B18 color filter manufactured by Toppan Printing Co., Ltd. was used as the color filter. As the light shielding ability of BM, an OD value of 3.5 or more is considered ideal in practical use. The BM of this embodiment has an OD value of 3.5. Therefore, the light incident from the glass substrate 1 side can be sufficiently shielded under normal use even when the color filter is not laminated on the BM.

  However, when the liquid crystal display device is mounted on the vehicle, sunlight directly enters from the glass substrate 1 side, so that it is necessary to further increase the light shielding ability of the BM. In addition, the light BL from the backlight reflected by the BM is incident on the TFT semiconductor layer 4 (channel) as it is when no color filter is stacked on the BM. There is. Even when a single-layer color filter is laminated on a BM, the OD value of the single-layer color filter is 1.01 at most. Not necessarily enough.

  In this embodiment, a red color filter 2R and a blue color filter 2B are stacked on the BM. Since the OD value of the two-layer color filter is 2.97, the sum with the OD value of BM is 6.47, and sufficient display quality can be ensured even under severe conditions such as in-vehicle. In addition, since the reflected light from the backlight BL reflected by the BM is transmitted twice through the two-layer color filter, the total light shielding ability for the backlight incident on the BM and the backlight reflected by the BM Is the square of the original OD value of the color filter. Therefore, by combining the red color filter 2R and the blue color filter 2B, a light-shielding property corresponding to an OD value of 8.82 can be obtained, so that fog caused by reflected light can be sufficiently suppressed even under severe conditions such as in-vehicle. .

  When three layers of red, green, and blue color filters 2R, 2G, and 2B are stacked on the BM, the OD value is 3.52, so that the light shielding property is sufficient. However, the three-layer color filters 2R, 2G, and 2B formed on the color filter substrate 10 side do not rub the portion (the periphery of the three-layer structure portion) that becomes a shadow of the three-layer structure portion even when the rubbing process is performed. This causes a problem that liquid crystal molecules cannot be aligned in a predetermined direction at the alignment film portion that has not been rubbed.

  In the present embodiment, the red color filter 2R and the blue color filter 2B are combined, but the combination of the red color filter 2R and the green color filter 2G, the blue color filter 2B and the green color filter 2G, Even with this combination, the light shielding ability is greatly improved.

  Next, a manufacturing method of the liquid crystal display device of this embodiment will be described. FIG. 6 is a plan view showing a manufacturing process of the color filter substrate 10 of the present embodiment. A method for manufacturing the color filter substrate 10 will be described with reference to FIG. First, BM is formed on the glass substrate 1 by an etching method or the like. Specifically, positive resist coating, mask exposure, development, etching, and peeling treatment are performed on a metal film, for example, a chromium film, formed on the glass substrate 1 by sputtering or the like. Note that a low reflection chromium film in which an oxide film is laminated on one side or both sides of a chromium film may be used.

  A green color filter 2G is formed at a position facing the green sub-pixel by a spin coating method or a film laminating method (see FIG. 6A). At this time, the color filter 2G is not stacked on the BM. Next, a red color filter 2R is formed at a position facing the red sub-pixel and all TFTs (see FIG. 6B). Thus, the red color filter 2R is laminated on each BM provided at a position facing all the TFTs. Further, a blue color filter 2B is formed at a position facing the blue sub-pixel and all the TFTs (see FIG. 6C). Accordingly, the red color filter 2R and the blue color filter 2B are sequentially stacked on each BM provided at a position facing all the TFTs.

  As shown in FIG. 2, the two color filters 2R and 2B stacked on the BM are the same color as the red and blue color filters 2R and 2B adjacent to the BM in the section taken along the line II-II in FIG. This is a color filter. On the other hand, as shown in FIG. 3, in the section taken along the line III-III in FIG. 1, one of the two color filters 2R and 2B stacked on the BM is red and red adjacent to the BM. This is a color filter of a color different from the green color filters 2R and 2G, that is, a blue color filter 2B.

  In the present embodiment, the two color filters 2R and 2B are stacked only on the BM at a position facing the TFT in the BM. However, the position facing the area that separates the red, green, and blue sub-pixels. For the BM, two color filters may be laminated.

  Further, a transparent electrode (not shown) such as ITO (indium tin oxide) is formed on the color filters 2R, 2G, and 2B by a chemical vapor deposition (CVD) method or a sputtering method. A polyimide-based or polyamide-based alignment film (not shown) is formed on the transparent electrode by a printing method, a spin coating method, an inkjet method, or the like, and a rubbing process is performed.

  Next, a method for manufacturing the TFT substrate 20 will be briefly described. A scanning wiring and a gate electrode 5 are formed on the glass substrate 3 by a photolithography method or the like, and a gate insulating film 6 is formed to cover them. Further, a semiconductor layer 4 is formed, and an impurity such as phosphorus is doped to form a channel. After forming the signal wiring (not shown), the source electrode 7, the drain electrode 8, and the pixel electrode, a polyimide-based or polyamide-based alignment film (not shown) is formed, and a rubbing process is performed.

  After columnar spacers (not shown) are formed on the color filter substrate 10 or the TFT substrate 20 by photolithography or the like, the color filter substrate 10 and the TFT substrate 20 are bonded together. The liquid crystal layer 30 is formed by injecting a liquid crystal material into the gap between the two substrates defined by the columnar spacers and sealing the injection port with a sealing material. Further, a retardation layer and a polarizing layer (both not shown) are sequentially bonded to the outer surfaces of the glass substrates 1 and 3, respectively. A backlight (not shown) as a light source is arranged on the opposite side (TFT substrate side) with respect to the observer, and the liquid crystal display device of this embodiment is obtained.

  In this embodiment, three color filters of red, green, and blue are used, but three color filters of magenta, yellow, and cyan may be used, and four or more color filters may be used. good. For example, four color filters of cyan, magenta, yellow, and green may be used. The pixel arrangement of the color filter substrate is not limited to the stripe arrangement shown in the embodiment, and other pixel arrangements such as a delta arrangement, a mosaic arrangement, and a square arrangement may be adopted.

(Comparative example)
FIG. 8 is a plan view showing a manufacturing process of the color filter substrate 100 in the liquid crystal display device shown in FIG. A method for manufacturing the color filter substrate 100 will be described with reference to FIG. First, in the same manner as in the embodiment, after forming a BM on the glass substrate 1, a green color filter 2G is formed at a position facing the green subpixel and the TFT connected to the electrode of the subpixel ( (See FIG. 8 (a)). Next, the red color filter 2R is formed at a position facing the red sub-pixel and the TFT connected to the electrode of the sub-pixel (see FIG. 8B). Further, a blue color filter 2B is formed at a position facing the blue subpixel and the TFT connected to the electrode of the subpixel (see FIG. 8C). In the same manner as in the embodiment, a transparent electrode and an alignment film are formed and a rubbing process is performed.

  In the color filter substrate 100 of this comparative example, a color filter of any one of the three color filters 2R, 2G, and 2B is laminated on a BM at a position facing the TFT. However, as shown in FIG. 5, since the OD value of the single-layer color filter is 1.01 at most, the increase in the light shielding property by the color filter is not always sufficient under severe conditions such as in-vehicle. Accordingly, there is a possibility that the off-current characteristics of the TFT deteriorate due to the external light incident from the observer side and transmitted through the BM, and the display is blurred.

  The color filter substrate of the present invention can be used for a color display device, particularly a color liquid crystal display device.

It is a top view which shows typically one pixel of the liquid crystal display device of this embodiment. It is the II-II sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is a graph which shows the transmitted light spectrum in the visible light area | region by the color filter of each color. It is a graph which shows the OD value at the time of combining the color filter of each color, and these. It is a top view which shows the manufacturing process of the color filter substrate 10 of embodiment. It is sectional drawing which shows the conventional color liquid crystal display device typically. It is a top view which shows the manufacturing process of the color filter substrate 100 in the liquid crystal display device shown in FIG.

Explanation of symbols

4 Semiconductor layer 10 Color filter substrate 20 TFT substrate 30 Liquid crystal layer 2R Red color filter 2G Green color filter 2B Blue color filter

Claims (7)

A color filter substrate disposed opposite to an element substrate on which an active element having a semiconductor layer is formed,
A transparent substrate; a light shielding layer formed on the transparent substrate and disposed at a position facing the active element; and at least two color filters formed on the transparent substrate; A color filter substrate in which two color filters of color filters are laminated on the light shielding layer.   The color filter substrate according to claim 1, wherein the at least two color filters are three color filters of red, green, and blue.   The color filter substrate according to claim 1 or 2, wherein the two color filters stacked on the light shielding layer are color filters of the same color as a color filter adjacent to the light shielding layer.   3. The color filter substrate according to claim 2, wherein one of the two color filters stacked on the light shielding layer is a color filter having a color different from that of the color filter adjacent to the light shielding layer. .   5. The color filter substrate according to claim 1, wherein the two color filters stacked on the light shielding layer are two color filters of red and blue. 6.   6. The color filter substrate according to claim 1, wherein the element substrate on which an active element having a semiconductor layer is formed, and the light shielding film is disposed at a position facing the active element, and the element substrate. And a display medium layer interposed in a gap between the color filter substrates.   The display device according to claim 6, wherein the display medium layer is a liquid crystal layer.

Images