JPH03109525A - Image display device - Google Patents

Abstract

PURPOSE:To easily accomplish a multicolor display panel by making the area of a picture element electrode per picture element differ from the area of a color filter which corresponds to the picture element electrode. CONSTITUTION:For example, a red filter 8, a green filter 9 and a blue filter 10 are formed in a mosaic state or in a striped state. A protective film 6 made of SiO2, etc., is formed on the filters, and furthermore, a transparent electrode 5 functioning as a liquid crystal driving electrode is formed on the protective film. As to a counter electrode on the opposite side, an element layer 3 in which a switching element for an active matrix and non-linear element are arranged is formed on a glass substrate 2, and on the layer 3, a transparent driving electrode layer 4 which corresponds to respective dots of the color filters is formed. And then, after making two glass substrates 1 and 2 opposite to each other, a peripheral part is sealed and liquid crystal 7 is enclosed. The driving electrode 4 corresponding to respective color filter parts 8, 9 and 10 makes and breaks so as to transmit a light beam having a wavelength corresponding to a prescribed color. Thus, a color image display can be accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color liquid crystal display suitable for color image display and color graphic display.

Conventionally, it has been impossible to realize multicolor display on a liquid crystal display due to the following points.

One is that the number of constituent dots or lines of the liquid crystal panel itself could not be increased. The limit of the normally used dynamic drive is 1/16 duty, and the maximum possible is to realize 16 lines at most. On the other hand, due to its nature, a color display is meaningless unless it has at least 100 lines, and for this purpose, liquid crystal driving with a duty of 1/100 must be realized.

Second, there was no superior liquid crystal multicolor display means. There is a method of creating color by mixing dyes such as guest-host liquid crystal, but it is extremely difficult to generate multiple colors within one substrate. There is also a method of overlapping panels of several colors, but this is expensive due to its construction, and it is impossible to produce colorful colors due to the multiple layers.

For the reasons mentioned above, it has been difficult to realize a liquid crystal multicolor display panel.

Therefore, an object of the present invention is to provide means for easily realizing a multicolor display panel by improving the above-mentioned drawbacks.

The present invention uses an active matrix using transistor switching and an MI
Using non-linear elements such as M-elements and diodes, the colorization technology uses a negative liquid crystal micro-shutter to open and close dots with mosaic or striped color filters to create multicolor images, which produces vivid color images. , which realizes a color graphic liquid crystal display.

FIG. 1 shows an example of the basic configuration of the present invention. First, a color filter is formed on a glass substrate 1. For example, a red filter 8, a green filter 9, and a blue filter 10 are formed in a mosaic shape or a stripe shape.

A protective film 6 such as 5i (h) is formed on top of this, and a transparent electrode 5 serving as a liquid crystal drive electrode is formed on top of this.The counter electrode on the opposite side is formed on a glass substrate 2, and is used as a switching element for an active matrix. , forming an element layer 3 (the drawing is shown in a simplified manner) in which nonlinear elements are arranged,
A transparent drive electrode layer 4 corresponding to each dot of the color filter is formed on the top thereof.

Next, these two glass substrates 1 and 2 are faced to each other, and the periphery is sealed to seal the liquid crystal 7. When this display panel is used as a transmission type, light is introduced from below through a polarizing plate under the glass substrate 1, and a black negative type guest host liquid crystal is used as the liquid crystal. Filter section 8 for each color. 9.
The drive electrodes 4 corresponding to No. 10 open and close to transmit light of a wavelength corresponding to a predetermined color.

Further, in order to prevent light from passing through the gap between the drive electrodes 4, a negative type guest host is used to maintain the black color at all times. As a result, the part of the liquid crystal that appears black (the part where the liquid crystal is
No light passes through the areas marked F), and the light of the wavelength that matches the corresponding optical filter passes through the parts where the liquid crystal is transparent (parts marked ○N), and the combination of the three primary colors creates a graphic Seven colors can be displayed. In addition, if you add a gradation display function by controlling the intermediate tone, that is, the state in which the liquid crystal becomes translucent, instead of turning the liquid crystal drive completely ON and OFF, all colors can be realized with various brightness, and color images can be realized. Display can be realized.

The above is one example of the present invention.Next, the structure of each part will be explained in order to show another configuration example.

FIG. 2 shows an example of the configuration of an optical color filter. A water-soluble organic resin layer such as polyvinyl alcohol or gelatin is formed on a transparent glass substrate 20, and black, red, blue, and green dyes are printed on this layer in a pattern to form a predetermined filter arrangement. The organic resin layer is dyed.

As a result, each color filter of the red part 22, front part 23, and edge part 24 is formed corresponding to the shutter part of the liquid crystal, and at the same time,
In order to prevent color bleeding at the boundaries of the filters due to transmitted light, the boundaries of each color filter are dyed with black thread to form a black frame 21. This black frame 21 is essential to prevent light from passing through the gap in the shutter when the liquid crystal is of a positive type.

Also, in the case of a negative type liquid crystal display, the presence of a black frame serves to reduce blurring of light. Further, in the case of a negative type liquid crystal, if the degree of dyeing in the horizontal direction of the dye is strong, the black frame 21 may contain a substance that prevents dyeing instead of the black dye. Furthermore, a transparent protective film 25 is applied to the upper part, and a conductive transparent film 26 that will become a liquid crystal driving electrode is formed thereon, and the lower electrode is completed by photo-etching into a required pattern.

Furthermore, the color of the dye used in the filter may be reduced or damaged during the formation of the transparent conductive film.

At this time, as shown in FIG. 3, the filter film 3 on the glass substrate 30 is
A protective film 34 is applied to 1.

Alternatively, a transparent conductive film 33 may be separately formed on a thin glass or plastic film 32 and bonded to the glass substrate 30.

FIG. 4 is an example of the structure of an active matrix formed on the upper substrate used in the present invention. The characteristics of this method are that a drive duty of 100 or more can be easily achieved and that gradation display can be easily achieved. In this example, a Si thin film transistor is fabricated on a transparent glass substrate with a relatively high melting point such as Pyrex or quartz, and it is relatively easy to fabricate a Si thin film transistor on a transparent substrate compared to an active matrix on a normal 6i single crystal wafer. It is characterized by being configurable.

FIG. 4(a) is a plan view showing one pixel (one dot) cell 41 of the matrix. Gate line (Y selection line)
44 is connected to the gate of the transistor 49, the data line (X line) 43 is connected to the source of the transistor 49 through the contact hole 47, and the liquid crystal drive electrode 42 is connected to the drain of the transistor 47 through the contact hole 46.

Further, the ground line 45 forms a charge holding capacitor 48 between the ground line 45 and the liquid crystal drive electrode 42 .

FIG. 4(b) shows an equivalent circuit of this cell 41. When the transistor 49 is ONL, the voltage input via the data line 43 is applied to the charge holding capacitor 48 or the liquid crystal drive electrode 42.
is held as an electric charge by the capacitance between the electrode and the opposing electrode. Therefore, since the leakage current of transistors and liquid crystals is small, the charge is retained for a quite long time, so in principle the duty is (
(retention time)/(time required to write charge), which is actually 10,000 or more. Furthermore, if the area of the liquid crystal drive electrode is large, the storage capacitor 48 is not necessary.

FIG. 4(C) is a sectional view taken along line A-B in FIG. 4(A). A first layer of Si thin film, which will become a channel, is formed on the transparent substrate 40 by low pressure CVD, plasma CVD, etc. After buttering, an oxide film is formed on the surface by oxidizing the Si layer, and then a second layer is formed. Form a Si layer to connect the gate line and GN.
After patterning the D line, the oxide film is further etched using the pattern as a mask to form a gate insulating film 51 and a gate electrode 50. Thereafter, using the gate electrode 50 as a mask, P ions are implanted into the entire structure to form an N-type layer, thereby forming a transistor base 53, a channel 55, and a drain 54.

Thereafter, an oxide film 52 is formed, a contact hole is made, a transparent conductive film is applied, and the data line 43 and the drive electrode 42 are formed by patterning.

As a result, the liquid crystal drive electrode acts as a light shutter, and the color of the filter corresponding to this electrode position is transmitted or blocked. Also, depending on the level of the voltage input to the data line,
Since the light transmittance of the liquid crystal can be continuously changed, so-called gradation display is possible, and since the three primary colors can be weighted and mixed additively, it has the great advantage of being able to reproduce all colors.

Also, since the drive duty can be made as high as possible even in the dot-sequential method, a full color image with 500 x 500 dots can be achieved.

In the present invention, the liquid crystal is further driven through a nonlinear element as a means for improving the driving duty of the liquid crystal. FIG. 5 and FIG. 6 are examples of configurations of nonlinear elements.

Figure 5 shows a configuration example of a metal-insulator-metal (MIM) element. The matrix cell 61 is connected from the X drive line 58 to the M
This is a configuration in which the drive electrode 57 is driven via the IM element 62. (b) is a cross section of (a), and for example, a Ta film is sputtered and patterned to form a Ta film 58, and its surface is anodized by 300 to 500 Å. Thereafter, the Ta film that will become the upper electrode is sputtered and patterned to form a Ta layer 60, and further a transparent drive electrode 57 is formed.

Figure 6 shows an example in which two diodes are connected in series with each other facing each other, and the N(P) sanctuary 67 is connected to the X drive line 66.
, P (N) Sanctuary 68. It is connected to the liquid crystal drive electrode 65 via the N(P) sanctuary 69 .

(B) is a cross-sectional view of (A), in which Si is placed on the transparent substrate 63.
After forming the layer islands, the N-type (P) region 67 is formed by ion implantation.
．． 69 and a P-type (N) region 68 are formed, and a transparent conductive film is further formed to form an X drive line 66 and a liquid crystal drive electrode 65.

The nonlinear element thus formed has a VI characteristic as shown in FIG. 7, and the current suddenly increases from a certain voltage.

When a liquid crystal cell is driven through this nonlinear element, an equivalent circuit as shown in FIG. 8 is obtained. The nonlinear element 80 has a nonlinear resistance RM and a capacitance of 1 icM, and the liquid crystal 81 has an equally low resistance RL and a capacitance C.
It can be expressed by L. When lighting the liquid crystal, if a voltage higher than that of the VTR is applied, RM has a low resistance and VM becomes almost equal to VD, so that most of the applied voltage is applied to the liquid crystal. After that, when the voltage drops below VTH, RM becomes very high, and VM is discharged with the time constant of CL and RL while the ON voltage applied by the capacitor JICL is held. Furthermore, when the liquid crystal is not lit, only a potential lower than that of the VTR is applied, so VM is almost at O potential.

Therefore, as in the active matrix shown in FIG. 4, the voltage for lighting is held as VM at JICL, so the duty can be increased. In this case as well, the fifth
The liquid crystal driving electrodes shown in FIGS. 57 and 65 correspond to the color filters and serve as shutters for light.

Furthermore, the feature of this nonlinear element is that it has a simple structure, and the driving method may be the same as the conventional simple 1/8 or 1/16 dynamic driving method. Although this method is suitable for graphic display, gradation display is also possible. One is to set the voltage level applied from the X line continuously, similar to the active matrix, and the other is to set the voltage level applied from the X line continuously.
The first method is to drive by dividing it in time.

The switching elements and nonlinear elements used in the present invention are constructed on a glass substrate and serve as the upper liquid crystal drive electrode.
The other glass substrate on which the filter is formed constitutes the lower liquid crystal drive electrode.

This is because, as shown in FIG. 2, forming elements directly on the filter not only deteriorates the characteristics of the filter but also causes a reduction in yield. In order to avoid this, there is a method of configuring the element on the thin glass 32 as shown in Fig. 3 and bonding it to the lower filter part to form a lower electrode.
There is a method in which a switching element or a nonlinear element is first formed on a glass substrate, and then a filter layer is formed.

FIG. 9 shows an example of the structure of the display panel of the present invention.

(A) is a cross-sectional view in which a switching element or a nonlinear element is configured on a glass substrate 90 as an upper electrode, and a drive electrode 9
form 7. Also, a color filter 92 is placed on the glass substrate 91 as a lower electrode. 93. 94 and a protective film 95
A liquid crystal drive electrode 96 is formed through the wafer.

Thereafter, the liquid crystal layer 98 is sandwiched between the two glass substrates 90 and 91, and a polarizing plate 99 is attached above or below, and light is irradiated from above or below. At this time, the problem is the gap between the filters or between the drive electrodes, and if the light goes around these areas, the reproducibility of beautiful colors will be poor.For example, if the light is transmitted from below, When the liquid crystal shutter is closed, light that has passed through the gap in the filter leaks through the gap in the drive electrode.

One way to prevent this is to use a negative type liquid crystal (a type that does not transmit light when no voltage is applied). Therefore, in this method, light is always blocked from the gap between the drive electrodes 97.

Another method is to provide a black frame in the gap between the filters as shown in FIG. Moreover, if both are used together, the effect will be further doubled. The light blur is caused by the shutter opening,
Occurs when light passes through it.

For example, when only the shutter on the red filter 92 is open, the blue filter 94 and green filter 93 on both sides
The light from the edge of the screen wraps around and leaks through the shutter above the red filter, which also reduces color reproducibility.

In order to prevent this, it is preferable to form the color filter larger than the effective shutter section of the liquid crystal. For example, for a mosaic filter as shown in FIG. 9(b), the active matrix drive electrode 97 is made small. In addition, in the example of a nonlinear element as shown in (c), the intersection of the lower liquid crystal drive electrode 96 and the upper liquid crystal drive electrode 97 becomes the effective shutter part, but the size of this effective shutter part is determined from the stripe type color filter. Keep it small. The same is true for mosaic filters.

The display method of such a color liquid crystal display requires a large ratio of transmittance when the liquid crystal shutter is open and when it is closed. In the case of a normal TN display, two polarizing plates are arranged above and below the display panel, and the planes of polarization are aligned so that it becomes a positive type. In this case, the transmittance ratio of the shutter is determined by the polarizing plates, which is the ratio between when the polarization directions of the two polarizing plates are parallel and when the polarization directions are perpendicular.

In reality, this ratio is about 10 at most in this polarizing plate, and the polarizing plate requires some ingenuity. On the other hand, when a guest-host liquid crystal is used, only one polarizing plate is required, so firstly, the brightness is twice that of a TN liquid crystal, and at the same time, the transmittance ratio is determined by the liquid crystal material, so it can be increased. For example, a guest-host liquid crystal containing a black dye usually blocks light well and is also quite transparent when a voltage is applied, with a transmittance ratio exceeding 50. Furthermore, a positive type guest-host liquid crystal has better stability and reliability than a negative type, and has a lower driving voltage, and at the same time, a positive type has a better transmittance ratio required for the present invention.

On the other hand, as mentioned above, a positive type liquid crystal is better at eliminating light wrapping, blurring, and leakage, and in this respect, the guest-host positive type liquid crystal is most suitable for the color display of the present invention. In particular, panels with black pigments have the best reproducibility of the three primary colors.

FIG. 10 shows an example of the filter arrangement and driving method for the color liquid crystal display of the present invention. Three primary color filter 106
are arranged in stripes in the X direction, and the drive electrodes on the filter side are arranged in a line or solid pattern in the same direction as the filter. Further, the upper electrode 105 is separated for each pixel in the X direction (the drawing is simplified and connected).

The shift register 101 is shifted from Sl to S by clock input φ5. This is a dot sequential system in which the video signal vS is sequentially sent to X1 to Xo. Further, the shift register 102 sequentially selects Y1 to Y using the clock φ4.

The three color signals VSR, VSB, and VSG are clocked by clock φ1.
~φ3 switches every line of Y, and φ1
．． φ2. φ3 has the same pulse width as φ4, and the pulse period is φ
It is three times 4.

The feature of this method is that the color filter is striped in the X direction, so the switching frequency of the color signal does not need to be slow, so the number of lines in the X direction can be increased, the display resolution is good, and high quality color images can be reproduced. be.

Figure 11 shows a striped color filter 11 in the X direction.
This is an example of arranging 6 dots, which is useful for increasing the number of lines in the horizontal direction, and also makes the dots close to square in size, giving the image a natural feel.

The shift register 112 sequentially selects the drive electrodes 115 based on the signals Y1 to Y. While any one of the drive electrodes 115 is selected, the shift register 111 sequentially selects filter groups R, G, and B as one unit.

Furthermore, R, G, B selection clock manual operation, φ2. φ3 is a signal obtained by further dividing the clock φ5 into three phases, and in synchronization with this selection clock, each color signal VSR, VSG, and VSB is selected one by one and guided to the X drive line.

In this method, the video signal line is connected to the sample-and-hold switch 113 in 3x parallel according to each color, so the frequency of the transfer lock φ5 of the shift register 111 can be 1/3 the frequency for the same number of dots. This has the advantage that the power consumption of the shift register can be reduced and that the shift register can be used within a margin of operating speed.

FIG. 12 shows an example in which filters are arranged in a mosaic pattern.

Red filter 121, green filter 122, blue filter 12
A white filter 124 is further added to 3 to form one block, and this is repeated in a matrix pattern.

When the transmittance of light to the filter is low, this white part
When all light passes through two filters, the white color does not come out clearly. In order to solve this problem, the transparent part is further formed as a white filter, and the luminance signal VSW of the video signal is
When controlled with , brightness improves and white reproducibility improves.
Overall brightness is improved. In this case, the driving method in the X direction is selected by a shift register in units of filter blocks, and operates in the same manner as shown in FIG. 11. Further, the X direction is selected by the shift register 126, and VSR and vSB, and VSG and vSW are alternately connected by half frequencies φ1 and φ2 synchronized with clock φ3.

As explained above, the present invention drives a positive type guest host liquid crystal with good light switching performance through a means that can improve the drive duty, that is, a switching element or a nonlinear element, and supports dots that serve as the liquid crystal drive electrode. Color display is achieved by arranging colored filters. As for the display format, a transmissive type can be used for applications where power consumption is tolerable to a certain extent, and a reflective type with a reflective surface arranged on the lower side can be used for applications where power consumption is to be kept low. The display body of the present invention is 100
It is capable of color display of more than 100 lines and has extremely high performance, that is, compared to CRT, it is small, compact, has less distortion, and achieves low power consumption graphics or image display, and has unprecedented performance. You can get .

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of the present invention. 1.2... Substrate 3... Element section 4.5... Liquid crystal drive electrode 6... Protective film 7... Liquid crystal body 8, 9. 10...Color filter FIGS. 2 and 3 are diagrams showing an example of the configuration of a color filter used in the present invention. 20.30... Substrate 22.23, 24.31... Filter section 21... Black frame 25.34... Protective film 26.33... Transparent conductive film 32... Thin substrate No. 4(a), (b), and (c) are diagrams showing an example of the configuration of an active matrix substrate used in the present invention. 49...Si thin film transistor FIGS. 5(a) and 6(b) and FIGS. 6(a) and 6(b) are diagrams showing examples of nonlinear elements used in the present invention. 62...MIM element 67.68.69...Si thin film diode Figure 7 is a V-I characteristic diagram of the nonlinear element. FIG. 8 is an equivalent drive circuit diagram. FIGS. 9A, 9B, and 9C are diagrams showing an example of the configuration of a color display device of the present invention. 90.91...Substrate 92.93.94...Filter 95...Protective film 96.97...Liquid crystal drive electrode 98...Liquid crystal 99...Polarizing plate Fig. 10, Fig. 11, FIG. 12 is a diagram showing an arrangement and driving example of the color filters of the color display device of the present invention. 101.102,111,112,126...Shift registers VSR, VSB, VSG-...Video color signal VSW...
・Applicant for luminance signal and above Seiko Epson Co., Ltd. agent Patent attorney Kizobe Suzuki and 1 other name) (c7) (Seno Figure 6)

Claims (1)

[Scope of Claims] A pair of substrates in which an electro-optical conversion substance is sealed, pixel electrodes arranged in a matrix on the substrates, and a color filter arranged corresponding to each of the pixel electrodes. An image display device comprising: an area of the pixel electrode per pixel and an area of the color filter corresponding to the pixel electrode are different from each other.