JPH0543116B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention combines a color filter and a liquid crystal, particularly a twisted nematic liquid crystal (hereinafter abbreviated as TN liquid crystal), to produce a thin film field effect transistor (hereinafter abbreviated as TFT), etc. The present invention relates to a color liquid crystal display device in which a liquid crystal is driven by a switching element.

(Conventional Structure and its Problems) Liquid crystal display devices are thin, driven at low voltage, and have low power consumption, and as a result, market needs for flat panel displays have been rapidly increasing recently. Conventionally, monochrome display devices have been the mainstream, but color liquid crystal display devices capable of displaying full color using red, green, and blue (hereinafter abbreviated as R, G, and B) color filters are about to be commercialized. In terms of drive, even if the number of scanning lines is increased to increase the resolution of the display, it is possible to display images with excellent contrast and visual dependence, so switching elements such as TFTs (thin film transistors) are incorporated to drive the liquid crystal. An active matrix method is also being used.

FIG. 1 is a cross-sectional view of the panel of a conventional color liquid crystal display device, in which 1 is a TN liquid crystal, 2a and 2b are alignment films for controlling the initial alignment of the TN liquid crystal 1 when no voltage is applied, and 3a and 3b are alignment films for controlling the initial alignment of the TN liquid crystal 1 when no voltage is applied. It is a transparent electrode. The transparent electrode 3b corresponds to a picture element electrode, and will be described later.
It is electrically connected to the drain electrode 4b of the TFT. 4a is a source electrode, 4b is a drain electrode,
5 is a semiconductor, 6 is a gate, and 7 is an insulating film, which constitute a TFT. The insulating film 7 serves as a gate insulating layer of the TFT and an insulating layer between the source electrode 4a and the gate 6.

8a, 8b, and 8c are R, G, and B color filters, 9a, 9b are transparent substrates, and 10 is a black stripe that partitions the color filters 8a, 8b, and 8c.

The operation of the conventional color liquid crystal display device configured as described above will be explained.

First, when a scanning signal is applied to gate 6, the TFT
ON, source electrode 4a, drain electrode 4b
The liquid crystal layer is electrically connected, and the video signal applied from the source electrode 4a charges the liquid crystal layer. Even if the scanning signal disappears, the TFT is turned off, so the transparent electrodes 3a and 3b
A voltage is continuously applied to the liquid crystal layer between the two. Since the amount of light transmitted through the liquid crystal layer changes depending on the voltage applied to the liquid crystal layer, it is possible to control the amount of light transmitted by the video signal voltage. The charge applied to the liquid crystal layer is applied to the gate by the following scanning signal,
After the TFT is turned on, until the next video signal is applied, leakage occurs through the TFT's OFF resistance and the resistance of the liquid crystal layer, but if both the TFT and liquid crystal have sufficiently large resistances, the leakage will be slight.

The picture element electrodes and the TFTs connected to them are arranged in a matrix, and a scanning signal applied to the gate 6 turns on the TFTs in the horizontal direction all at once, writes a video signal from the source electrode 4a to the picture element, and writes the video signal in the vertical direction. It is possible to display an image by sequentially scanning the images.

R, G, B color filters 8a, 8b, 8c
are installed corresponding to each picture element electrode, R,
Since the amount of light transmitted through each of the G and B picture elements can be arbitrarily controlled by applied voltage, full-color display is possible by additive color mixing of R, G, and B.

However, in the conventional method, apart from the step of forming the color filters, a step of forming black stripes for dividing the R, G, and B color filters was required. Black stripes are usually formed using blackened chromium (chromium + chromium oxide) or black dye, but this has the disadvantage of increasing cost and decreasing yield. Furthermore, when a TFT is used as a switching element, it is necessary to provide a light shielding layer for the TFT in order to prevent deterioration of the switching function due to the photoconductive effect, but this step is also required in addition to the color filter forming step.

(Object of the Invention) The object of the present invention is to solve the conventional drawbacks and to improve the black stripe and TFT for dividing the color filter.
It is an object of the present invention to provide a color liquid crystal display device that can be manufactured with high yield by simplifying the process of forming a light shielding layer. Another object of the present invention is to provide a color liquid crystal display device with excellent contrast and color reproducibility by actively employing such a configuration in a liquid crystal display device in which liquid crystal layers have different thicknesses for R, G, and B.

(Structure of the Invention) The color liquid crystal display device of the present invention includes a first substrate on which one or more transparent electrodes are formed, and an electrode corresponding to a pixel electrode or a transparent electrode on one principal surface. The electrode group and a second substrate on which a switching element group provided for each picture element electrode for driving the picture element electrodes are formed, facing each other such that the main surface on which the electrodes are formed is the opposing inner surface. , a liquid crystal layer is sandwiched in the opposing space, and three types of color filters, red, green, and blue, are arranged on the opposing inner surface of the first substrate in a predetermined repetition pattern corresponding to one type of pixel electrode. The red color filter has a red colored layer, the green color filter has a green colored layer, and the blue color filter has a blue colored layer.
Each of the color filters is divided into light-absorbing stripes formed by overlapping two types of colored layers, and the portion facing the switching element is formed by three types of colored layers and overlapping colored layers. A light-absorbing layer is formed, and each thickness d _R of the liquid crystal layer corresponding to the red, green, and blue color filters is
d _G and d _B are predetermined values such that d _R > d _G > d _B , and a voltage is applied to the liquid crystal layer to modulate light.

Further, the thickness of the color filter is different for red, green, and blue.

(Description of Embodiment) An embodiment of the present invention will be described based on FIGS. 2 to 7.

FIG. 2 is a configuration diagram of R, G, and B color filters used in the color liquid crystal display device of the present invention. As can be seen from the figure, the R color filter consists of a layer colored with a red (abbreviated as R in the figure) dye or pigment, and the G color filter consists of a layer colored with a red (abbreviated as R in the figure) dye or pigment. The color filter B consists of two layers: a colored layer made of yellow (abbreviated as Ye in the figure) and a colored layer made of a dye or pigment of yellow (abbreviated as Ye in the figure), and a colored layer made of cyan dye or pigment, etc. It consists of two colored layers made of dyes or pigments.

Figure 3 shows R, G, B configured as described above.
FIG. 2 is a spectral transmission characteristic diagram of a color filter.

Figure 4 shows the arrangement of picture elements, where 11 is the TFT light-shielding part;
12 is the picture element part, 13 is the black stripe part,
For the picture elements arranged in this way, R, G, and B color filters are installed as shown by R, G, and B in the same figure.

FIG. 5 is a sectional view showing the process of forming a color filter.

First, as shown in Figure 5a, the picture element part of R and
A colored layer of R is selectively formed on the TFT light-shielding part and the black stripe part. The formation range is shown in the figure by a hatched area surrounded by a thick frame, and this is common to b to d.

Next, as shown in b, a colored layer of Cy is selectively formed on the G picture element part and the B picture element part, and then c
As shown in the figure, a Ye colored layer is selectively formed on the G picture element area and the TFT light shielding area. Finally, with the picture element part of B
d. Selectively forming a colored layer of B on the TFT light-shielding area and black stripe area. As a result, the black stripe portion has a two-layer structure of overlapping R and B colored layers, and the portion facing the TFT has a three-layer structure of overlapping R, Ye, and B colored layers. Note that a transparent layer may be used in the B picture element portion instead of the cyan colored layer.

At this time, the thickness of each colored layer is adjusted so that the thicknesses d _R , d _G , d _{B of the liquid crystal layer corresponding to each picture element of R, G, and B} become optically optimized values. In this way, a color filter with even better optical properties can be obtained. This is to compensate for the optical rotational dispersion of the TN liquid crystal, as stated in Japanese Patent Application No. 16552/1983.

Figure 6 shows two layers of R and B, and R, Ye, and B.
The spectral transmission characteristics of the three layers are shown below. As can be seen from this figure, the overlapping portion of the two layers R and B has excellent light shielding properties with a light transmittance of 3% or less over the entire visible light range (400 to 700 μm), and improves color separation and contrast. It fully fulfills its function as a black stripe that improves the appearance. Also, from the same figure,
The overlapping portion of the three layers of R, Ye, and B has excellent light-shielding properties with a light transmittance of 0.5% or less over the entire visible light range, and plays a sufficient role as a light-shielding layer for TFT, and has a photoconductive effect. It is possible to prevent the TFT's switching function from deteriorating due to this phenomenon and ensure good display performance.

FIG. 7 is a sectional view of the panel part of the color liquid crystal display device of the present invention, and the numbers of each part are the same, except that 8d is a red colored layer, 8e is a cyan colored layer, 8f is a yellow colored layer, and 8g is a blue colored layer. Same as Figure 1.

In FIG. 7, the green filter is formed by additive color mixing by laminating a cyan colored layer 8e and a yellow colored layer 8f. In addition, since the optical rotary dispersion ability of TN liquid crystal has wavelength dependence of light,
The optimal liquid crystal thickness is different for red, green, and blue. As shown in Figure 7, if d _R , d _G , and d _B are each the optimal thickness, d _R
The relationship is ＞d _G ＞d _B. According to the invention,
Since each color filter is formed by overlapping two types of colored layers, the above liquid crystal thickness can be easily achieved by selecting the thickness of each colored layer.

The operation is also the same as that of the conventional example, so the explanation will be omitted.

Although only the color liquid crystal display device combined with TFT was explained here, MOS-
It is also applicable when combined with nonlinear elements such as FETs. Furthermore, the scope of the present invention also includes a color liquid crystal display device, which is a combination of a color filter and a liquid crystal, regardless of whether it is a transmissive type or a reverse type.

(Effects of the Invention) According to the present invention, the black stripes that partition the R, G, and B color filters and the TFT light-shielding layer are formed in the same process as forming the R, G, and B color filters. This has the effect of simplifying the process, reducing an increase in cost, and suppressing a decrease in yield.

In addition, at that time, the black stripe part is R and B.
By having a two-layer structure of colored layers, it has excellent light absorption over the entire visible light range, and satisfactorily fulfills the functions of a black stripe, such as improving color separation and contrast.

In addition, the FET light-shielding part has a three-layer structure of R, Ye, and B colored layers, which has extremely excellent light absorption over the entire visible light range.This blocks light from the TFT, allowing the TFT to function as a switching function due to the photoconductive effect. This has the effect of preventing a decrease in the display performance and ensuring good display performance.

Furthermore, with such a configuration, by appropriately adjusting the thickness of the colored layer, the thickness of the liquid crystal layer corresponding to each R, G, and B picture element can be set to an optically optimum value, and TN
It has the effect of compensating for optical rotational dispersion of liquid crystals and providing excellent contrast and color reproducibility.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the panel of a conventional color liquid crystal display device, Fig. 2 is a configuration diagram of R, G, and B color filters, and Fig. 3 is a spectral transmission characteristic diagram of the R, G, and B color filters. Figure 4 is a pixel arrangement diagram, Figure 5 is a color filter manufacturing process diagram, Figure 6 is a diagram of spectral transmission characteristics of two layers of R and B and three layers of R, Ye, and B.
FIG. 7 is a sectional view of the panel portion of the color liquid crystal display device of the present invention. 1...TN liquid crystal, 2a, 2b...alignment film, 3
a, 3b...transparent electrode, 4a...source electrode, 4
b...Drain electrode, 4d...R colored layer, 4e...
...Cy colored layer, 4f...Ye colored layer, 4g...B colored layer, 5...Semiconductor, 6...Gate, 7...Insulating film, 8a, 8b, 8c...Color filter, 8
d, 8e, 8f, 8g... colored layer, 9a, 9b...
...Transparent substrate, 10, 13...Black stripe, 11...TFT light shielding section, 12...Picture element section.

Claims (1)

[Scope of Claims] 1. A first substrate on which one or more transparent electrodes are formed; an electrode or transparent electrode group corresponding to a picture element electrode on one principal surface; and a first substrate on which one or more transparent electrodes are formed; A second substrate on which a switching element group provided for each picture element electrode for driving is formed is opposed to the second substrate such that the main surface on which the electrode is formed is the opposing inner surface, and within the opposing space. A liquid crystal layer is sandwiched between the first substrate, and a large number of red, green, and blue color filters are arranged on the opposing inner surface of the first substrate in a predetermined repetition manner, one color filter corresponding to each of the picture element electrodes. The color filter has a red colored layer, the green color filter has a green colored layer, and the blue color filter has a blue colored layer. Each is divided into light-absorbing stripes formed by overlapping two types of colored layers, and a light-absorbing layer formed by three types of colored layers and overlapping colored layers is provided in the portion facing the switching element. The thicknesses d _R , d _G , and d _B of the liquid crystal layers corresponding to the red, green, and blue color filters are set to predetermined values such that d _R > d _G > d _B , and the liquid crystal layers correspond to the red, green, and blue color filters. A color liquid crystal display device that modulates light by applying a voltage to its layers. 2. The color liquid crystal display device according to claim 1, wherein the color filters have different thicknesses for red, green, and blue.