JP2002214644A - Active matrix type liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active matrix type liquid crystal display which causes no color shift at any voltage and actualizes high image quality. SOLUTION: The active matrix type liquid crystal display device which adopts an IPS system has multiple kinds of color filters with different spectral transmission characteristics arranged in matrix on at least one of an array substrate and an opposite substrate and is characterized by that the distance between side ends of adjacent pixel electrodes of pixels corresponding to the spectral transmission characteristics of those color filters and the side end of a common electrode is larger as the wavelength light is shorter according to the spectral transmission characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an active matrix type liquid crystal display device used as a flat display for AV equipment, OA equipment, and the like.

[0002]

2. Description of the Related Art At present, a display device using a liquid crystal display element includes a viewfinder of a video camera, a pocket TV,
Furthermore, it has been applied in various fields such as high-definition projection TVs and display devices in information devices such as personal computers and word processors, and is being actively developed and commercialized. In particular, a thin film transistor (TF
The active matrix type liquid crystal display device using T) has a great feature that high contrast can be maintained even when a large-capacity display is performed. The development and commercialization of notebook PCs, as well as large and large-capacity full-color displays for engineering workstations, are actively pursued.

The liquid crystal display modes used in such an active matrix type liquid crystal display device include I
There is a PS (In-plane Switching) method. The IPS mode is a mode in which the direction in which an electric field is applied to the liquid crystal is substantially parallel to the substrate. That is, a comb-shaped electrode is formed on one of the two substrates sandwiching the liquid crystal layer, and an electric field is applied between the comb-shaped electrodes to control the arrangement direction of the liquid crystal molecules. The polarization state of light passing through the panel changes depending on the arrangement state, and the light transmittance is modulated.

Such an IPS type liquid crystal display device has excellent viewing angle characteristics, and a luminance inversion phenomenon, that is, a display luminance at a predetermined voltage when the viewpoint is inclined obliquely, and a display luminance at a lower voltage. Since the phenomenon of becoming brighter does not occur, application to a large monitor is expected.

[0005]

FIG. 2A is a schematic plan view of three pixels of a TFT array substrate in a conventional liquid crystal display device employing the IPS system. FIG. 2 (b)
FIG. 2 is a schematic cross-sectional view of the liquid crystal display device taken along a dashed line BB ′ shown in FIG.

As shown in FIG. 2, a plurality of scanning wirings 1 and signal wirings 2 are formed on an array substrate 8 so as to be orthogonal to each other, and are switching elements corresponding to respective intersections of the scanning wirings 1 and the signal wirings 2. A TFT 3 is provided. Also,
A common line 4 is formed between two adjacent scanning lines 1 in parallel with the scanning line 1, and a comb-shaped common electrode 5 electrically connected to the common line 4 is formed.

Then, a comb-shaped pixel electrode 6 connected to the TFT 3 is formed so as to engage with the common electrode 5, and a storage capacitor 7 connected to the pixel electrode 6 is formed on the scanning wiring 1. Further, a black matrix 13 is formed on the counter substrate 9 corresponding to the pixels formed on the array substrate 8, and a red color filter 10 is provided for each pixel.
, A green color filter 11 and a blue color filter 12.

When a voltage is applied between the pixel electrode 6 and the common electrode 5 to the liquid crystal display device having such a configuration, the liquid crystal molecules tend to be arranged in the direction of the electric field. The polarization state of the incident light passing through the layer changes and the light transmittance is modulated. Then, by passing through the red color filter 10, the green color filter 11, and the blue color filter 12, respectively, full color display can be performed by additive color mixture.

However, when the polarization state of the incident light changes,
The magnitude of polarization change differs depending on the wavelength of light. That is, the light transmittance has wavelength dependence. FIG. 4 shows the relationship between the voltage between the pixel electrode 6 and the common electrode 5 and the light transmittance (hereinafter, referred to as “TV characteristics”).

As shown in FIG. 4, in the case of light having different wavelengths from red, green and blue, the transmittance is different even at the same voltage. Therefore, in order to make the light passing through the red color filter 10, the green color filter 11, and the blue color filter 12 achromatic by additive color mixing, the difference between the transmittances of red, green, and blue at a certain voltage is determined by the incident light. The color needs to be adjusted.

However, since the color of incident light is constant, even if it can be set to achromatic at a certain voltage,
There is a problem that color misregistration occurs because other voltages cannot be adjusted. For example, in order to gain panel transmittance, when the voltage is adjusted to achromatic at a voltage corresponding to the green peak transmittance with the highest visibility, the balance is lost at a lower voltage (halftone), and the blue color is lost. Since the transmittance is relatively large, the result is a bluish halftone.

An object of the present invention is to provide an active matrix type liquid crystal display device in which color shift does not occur at any voltage in order to solve the above problem.

[0013]

In order to achieve the above object, an active matrix type liquid crystal display device according to the present invention comprises a comb-shaped pixel electrode, a comb-shaped common electrode formed by engaging the pixel electrode. An array substrate having a liquid crystal layer sandwiched between the array substrate and the opposing substrate, and a liquid crystal layer sandwiched between the array substrate and the opposing substrate. In an active matrix liquid crystal display device that changes the arrangement of liquid crystal molecules by generating a substantially parallel electric field, a plurality of types of color filters having different spectral transmission characteristics are arranged in a matrix on at least one of an array substrate and a counter substrate, The distance between the side edge of the adjacent pixel electrode and the side edge of the common electrode in a pixel corresponding to the spectral transmission characteristics of a plurality of types of color filters is different. Characterized vary depending on transmission characteristics.

With this configuration, the distance between the electrodes can be adjusted according to the spectral transmission characteristics of a plurality of types of color filters, so that the TV characteristics can be freely adjusted, and the transmittance due to the difference in color can be adjusted. , It is possible to display a high-quality image with no color shift in any gradation display.

Further, the active matrix type liquid crystal display device according to the present invention preferably comprises three types of color filters having spectral transmission characteristics for transmitting mainly red, green and blue light, respectively. This is because if the three primary colors of light can be adjusted, it is sufficient for color display.

Further, the active matrix type liquid crystal display device according to the present invention is characterized in that adjacent pixel electrodes of pixels corresponding to three types of color filters having spectral transmission characteristics for transmitting mainly red, green and blue light, respectively. The distance between the side end and the side end of the common electrode is Lr, L, respectively.
Assuming that g or Lb, it is preferable to satisfy the relationship of Lr ≦ Lg <Lb. When the distance between electrodes is increased, TV
This is because the characteristic shifts to the high voltage side, so that the longer the wavelength of the light, that is, the lower the voltage at the peak transmittance, the larger the distance between the electrodes.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an active matrix type liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a schematic plan view of three pixels of a TFT array substrate in an active matrix type liquid crystal display device according to an embodiment of the present invention. FIG. 1B is a view similar to FIG.
FIG. 2 is a schematic cross-sectional view of the liquid crystal display device taken along a chain line AA ′ shown in FIG.

In this embodiment, the scanning wirings 1 are formed on the array substrate 8 by photolithography using chromium in a pattern as shown in FIG. 1A. At the same time, the common wiring 4 is formed, and the common electrode 5 is formed in a comb shape as shown in FIG. The material is not particularly limited to chromium, and a conductive single-layer film or a multilayer film such as aluminum or a metal containing aluminum as a main component may be used.

Next, silicon nitride (SiNx) is used as the first insulator layer 14 functioning as a gate insulating film of the TFT 3.
Is laminated thereon, and amorphous silicon (α-Si) is laminated on the semiconductor layer that controls the switching function of the TFT 3 by a plasma CVD method.

Thereafter, two layers of titanium / aluminum (Ti / Al) are deposited by a sputtering method, and then the signal wiring 2 is patterned by dry etching. At the same time, the pixel electrode 6 is formed in a comb shape along the common electrode 5. The material is not particularly limited to titanium / aluminum (Ti / Al), and a single-layer film or a multilayer film of a conductive metal may be used.

At this time, the storage capacitor section 7 is formed by forming the pixel electrode 6 so as to overlap the scanning wiring 1 with the first insulating film layer 14 interposed therebetween. The storage capacitor unit 7 is provided to hold the voltage supplied to the pixel. Further, silicon nitride (SiNx) is laminated thereon as the second insulator layer 15 functioning as a protective film of the TFT 3.

An alignment film is applied to the thin film transistor array substrate completed in the above-described steps, the counter substrate 9 including the red color filter 10, the green color filter 11, the blue color filter 12, and the black matrix 13, A rubbing process is performed. Thereafter, a gap of 4 μm is formed and bonded, liquid crystal having a positive dielectric anisotropy is injected between the gaps, and a polarizing plate is arranged outside of both substrates so as to be orthogonal to each polarization axis to display the liquid crystal. Make the device.

For example, the distance Lr between the end of the adjacent pixel electrode 6 and the end of the common electrode 5 in the pixel corresponding to the red color filter 10 is set to 11 μm, and the distance Lg between the electrodes corresponding to the green color filter 11 and the blue color filter 12 is set. When Lb and Lb are set to 12 μm and 14 μm, respectively, and the lighting image inspection is performed, the liquid crystal display device has a wide viewing angle characteristic and excellent image display of achromatic display without color shift at any gradation. We were able to.

The distance L between the end of the adjacent pixel electrode 6 and the end of the common electrode 5 in the pixel corresponding to the red color filter 10
r is 12 μm, and the distances Lg and Lb between the electrodes corresponding to the green color filter 11 and the blue color filter 12 are set to 12 μm and 14 μm, respectively, so that Lr = Lg because the difference between the TV characteristics of red and green is small. When the lighting image inspection was performed with the setting, the liquid crystal display device also had a wide viewing angle characteristic, and an excellent achromatic color image display without any color shift was obtained at any gradation.

As described above, TV in the IPS system
The characteristics depend on the distance between electrodes to which a voltage is applied. That is, by changing the distance between the side edge of the adjacent pixel electrode and the side edge of the common electrode in the pixel corresponding to each of the red, green, and blue color filters,
As shown in the graph of FIG. 3, the TV characteristics when the wavelengths are different from red, green, and blue can be made the same. Specifically, when the distance between the electrodes is increased, the TV characteristic shifts to the high voltage side. Therefore, by increasing or decreasing the width of the common electrode, the pixels corresponding to the red, green, and blue color filters are reduced. , The distance between the side edge of the adjacent pixel electrode and the side edge of the common electrode can be changed.
Assuming that the distances between the side edges of the adjacent pixel electrodes and the side edges of the common electrode in the pixels corresponding to the red, green, and blue color filters are Lr, Lg, and Lb, respectively, Lr <L
By adopting a configuration that satisfies g <Lb, it is possible to adjust the TV characteristics to be the same. As a result, there is no difference in transmittance between red, green, and blue at any voltage, so that achromatic display can be performed without color shift in any gradation display.

The active matrix type liquid crystal display device as described above can be applied to various types of image display application devices, and it goes without saying that similar effects can be expected in each image display application device.

[0027]

As described above, according to the active matrix type liquid crystal display device of the present invention, a simple configuration and the same manufacturing steps as those of the prior art can be used without changing the drive circuit configuration. An achromatic image without color shift can be displayed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a TFT array substrate in an active matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a TFT array substrate in a conventional active matrix type liquid crystal display device.

FIG. 3 is a diagram showing a relationship between applied voltage and transmittance in an active matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between applied voltage and transmittance in a conventional active matrix type liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanning wiring 2 Signal wiring 3 TFT 4 Common wiring 5 Common electrode 6 Pixel electrode 7 Storage capacity part 8 Array substrate 9 Counter substrate 10 Red color filter 11 Green color filter 12 Blue color filter 13 Black matrix 14 First insulator layer 15 First 2 insulator layers

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirofumi Sekimoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 2H091 FA02Y GA02 HA06 LA15 LA20 2H092 GA14 JA24 JA34 JA37 JA41 JB05 MA05 MA13 MA18 NA01 PA08 QA06 5C094 AA07 AA08 BA03 BA43 CA19 CA24 CA25 ED03

Claims (4)

[Claims] 1. An array substrate having a comb-shaped pixel electrode, a comb-shaped common electrode formed by engaging with the pixel electrode, an opposing substrate arranged to face the array substrate, and the array A liquid crystal layer sandwiched between the substrate and the counter substrate, and changing the arrangement of the liquid crystal molecules by generating an electric field between the pixel electrode and the common electrode that is substantially parallel to the array substrate and the counter substrate. An active matrix liquid crystal display device, wherein a plurality of types of color filters having different spectral transmission characteristics are arranged in a matrix on at least one of the array substrate and the counter substrate, and the spectral transmission characteristics of the plurality of types of color filters are changed. The distance between the side edge of the adjacent pixel electrode and the side edge of the common electrode in the corresponding pixel is different depending on the spectral transmission characteristic. An active matrix type liquid crystal display device. 2. The active matrix type liquid crystal display device according to claim 1, further comprising three types of said color filters each having a spectral transmission characteristic for transmitting mainly red, green or blue light. 3. A side edge of an adjacent pixel electrode and a side edge of the common electrode in a pixel corresponding to three kinds of the color filters each having a spectral transmission characteristic of transmitting red, green, or blue light, respectively. Are Lr,
The active matrix liquid crystal display device according to claim 2, wherein Lg or Lb has a relationship of Lr≤Lg <Lb. 4. An image display application device comprising the active matrix type liquid crystal display device according to claim 1. Description: