Liquid crystal display device.

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a liquid crystal display device, and more particularly to a reflective liquid crystal display device preferably implemented in OA (office automation) devices such as word processors and notebook computers, various video devices, and game devices.

【0002】

[Conventional technology]

Liquid crystal display devices are currently used in a wide range of fields such as clocks, calculators, computer terminals, word processors, and TV receivers. A typical display mode used for these applications is a so-called TN (Twisted Nematic) mode in which liquid crystal molecules in a liquid crystal display element are twisted by approximately 90 degrees as an initial orientation.

【0003】

In the TN mode, a liquid crystal display element is arranged between a set of polarizing plates, and the optical properties of the liquid crystal display element, that is, the optical rotation characteristic when no voltage is applied and the depolarization characteristic when a voltage is applied, are used for monochrome (monochrome). Black and white) display.

【0004】

Regarding color display, for example, red, blue, and green color filters are provided in the liquid crystal display element, and the above-mentioned optical switching characteristics in the TN mode are used to perform multi-color display or full-color display by additive color mixing. The color display method is currently used in a portable so-called pocket liquid crystal television display to which active matrix drive or simple matrix drive is applied.

【0005】

A display mode widely used as a display for a word processor is the STN (Super Twisted Nematic) mode, which has a liquid crystal display element structure similar to the above TN mode and sets the twisted angle of liquid crystal molecules to 180 to 270 degrees. Be done. The feature of this STN mode is that the twist angle of the liquid crystal molecule is increased by 90 degrees or more and the polarizing plate installation angle is optimized, so that the rapid molecular orientation deformation accompanying the increase of the applied voltage is reflected in the birefringence change of the liquid crystal. , It realizes electro-optical characteristics with a sharp threshold. Therefore, it is suitable for simple matrix drive.

【0006】

On the other hand, the disadvantage of this STN mode is that the background color of the display is yellowish green or dark blue due to the birefringence of the liquid crystal. As a remedy for this, a liquid crystal display element has been proposed that enables color compensation by superimposing an optical compensation panel or a retardation plate made of a polymer such as polycarbonate on a display STN panel to enable black-and-white display. There is. Currently, a liquid crystal display element structure is on the market as a so-called paper white LCD. Further, regarding the color display in the STN mode, multi-color display or full-color display is possible by the same operating principle as the above-mentioned TN mode.

【0007】

When a wide viewing angle is required, a so-called GH (guest host) mode is used in which a dye (dichroic dye) having different absorbances in the major axis direction and the minor axis direction of the molecule is added to the liquid crystal molecule. To. This GH mode can be classified into a Heilmeier type that uses a polarizing plate, a White-Taylor type (phase transition type) that does not use a deflection plate, and a two-layer type. , The orientation of the dye is controlled through the orientation of the liquid crystal molecules by voltage, and the difference in absorbance in the direction of the dye molecules is used for display. Regarding color display, color display is possible by using a dye that absorbs a part of the wavelength of visible light as the dye, or by combining a GH mode liquid crystal display element using a dye that becomes black with a colored filter. The detailed operating principles of TN mode, STN mode, and GH mode are described in "Liquid Crystal Device Handbook" (1989), pp. 315-346, edited by the 142nd Committee of the Japan Society for the Promotion of Science.

【0008】

[Problems to be Solved by the Invention]

In the conventional liquid crystal display device, a sufficient applied voltage cannot be maintained in the pixels of the liquid crystal display element, and a good display cannot be obtained. Further, in the display mode using a polarizing plate, the light utilization rate is reduced to at least 50% or less due to the optical properties of the polarizing plate. Therefore, in order to realize the so-called bright display required for a reflective display or a projection display, the polarizing plate-free display mode is more advantageous. From this point of view, the candidates from the above-mentioned display modes are the White-Taylor type (phase transition type) GH mode and the two-layer type GH mode.

【0009】

Comparing these two display modes, it has already been reported that the two-layer GH mode is superior in terms of contrast and brightness [Proc. Of the SID.2514 (1984) P.275). ]. However, in the conventional two-layer type GH mode liquid crystal display element, since a normal glass substrate is used between the liquid crystal layers, there is a drawback that parallax occurs between the upper and lower liquid crystal layers depending on the viewing angle, and the display becomes loose.

【0010】

As a remedy for this, it is conceivable to make the glass thickness between the liquid crystal layers extremely thin, but there are problems such as difficulty in handling and difficulty in controlling the thickness of the liquid crystal display element. Therefore, it cannot be applied to a display having a relatively large area and high definition.

【0011】

For the above-mentioned parallax, the White-Taylor type GH mode is more suitable because it is composed of one layer, but it is inferior in terms of display accuracy as described above, and especially in the case of multicolor display, it is microcolor. Brightness is lost due to the need to use filters, and the display is inferior in vividness.

【0012】

The present invention is to provide a liquid crystal display device capable of solving the above-mentioned problems and performing high-definition and bright display.

【0013】

[Means for solving problems]

In the present invention, a liquid crystal layer sandwiched between a pair of insulating substrates, a plurality of pixels provided on one insulating substrate, and a drive corresponding to the pixels from a scanning signal and a drive signal provided for each pixel. In a liquid crystal display device including a switching element that outputs a signal and a signal holding means that is electrically connected to the switching element and holds a drive signal corresponding to the pixel, the switching element and the signal holding means are electrically connected. It is characterized by having a buffer which is connected to and supplies a signal to the pixel by a drive signal corresponding to the pixel from the switching element or the signal holding means. Further, the present invention corresponds to a liquid crystal layer sandwiched between a pair of insulating substrates, a plurality of pixels provided on one insulating substrate, and scanning signals and drive signals provided for each pixel to correspond to the pixels. In a liquid crystal display device having a liquid crystal display element including a switching element that outputs a drive signal and a signal holding means that is electrically connected to the switching element and holds a drive signal corresponding to the pixel, for each switching element. When the first signal holding means and the second signal holding means provided are provided and the driving signal corresponding to the pixel is supplied to the pixel from the first signal holding means, the second signal holding means is provided. The means is characterized by having a switching means for supplying a drive signal corresponding to the display on the next screen from the switching element.

【0014】

Further, the present invention is characterized by having a light selection means for changing the wavelength of the incident light on the liquid crystal display element every predetermined unit time. Further, in the present invention, the switching means includes an n-channel transistor provided between the switching element and the one signal holding means, and a p-channel transistor provided between the one signal holding means and the pixel. It has a p-channel transistor provided between the switching element and the other signal holding means, and an n-channel transistor provided between the other signal holding means and the pixel, and the gate of each transistor has an n-channel transistor. , Commonly characterized by supplying high-level and low-level signals every unit time.

【0015】

[Action]

The invention of claim 1 is a signal holding means by providing a buffer that is electrically connected to a switching element and a signal holding means and supplies a signal to the pixels by a drive signal corresponding to the pixels from the switching element or the signal holding means. Since the electric charge held in the signal is not directly applied to the liquid crystal but the voltage is applied to the liquid crystal through the buffer, it is possible to suppress a decrease in the capacity held by the signal holding capacity, and the capacity of the signal holding capacity can be suppressed. A good display can be obtained regardless of the size.

【0016】

Further, the invention of claim 2 has a first signal holding means and a second signal holding means provided for each switching element, and a drive signal corresponding to the pixel is transmitted from the first signal holding means to the pixel. By providing the second signal holding means with a switching means for supplying a drive signal corresponding to the display of the next screen from the switching element, the entire screen of the liquid crystal display element is switched to the next screen all at once. This makes it possible to display moving images with high display quality.

【0017】

Further, the invention of claim 3 enables time-divided color display by providing a light selection means for changing the wavelength of the incident light on the liquid crystal display element at predetermined unit times, and enables color display of area classification. Compared with this, the resolution is increased and a good display state can be obtained.

【0018】

Further, the invention of claim 4 is to supply a common signal to the gate of each transistor by connecting a plurality of signal holding means, a switching element and a pixel via an n-channel transistor and a p-channel transistor. When a drive signal corresponding to the transistor is supplied to the pixel from the signal holding means of the above, it is possible to obtain a switching means for supplying a drive signal corresponding to the display of the next screen from the switching element to the other signal holding means. , Eliminates the need to generate multiple control signals.

【0019】

[Example]

In the present invention, a color variable filter capable of converting the wavelength of transmitted light by a voltage applying means is installed on a reflective liquid crystal display element that displays black and white, and the reflective liquid crystal display element is synchronized with the color change of this filter. Multi-color display or full-color display is performed by changing the display pattern of. That is, when a color variable filter capable of transmitting and changing the wavelengths of light corresponding to, for example, red, blue, and green in a voltage-applied state is selected, the display pattern of the liquid crystal display element is matched with the transmission change of the color variable filter. The desired color display is possible by changing. If the liquid crystal display element is capable of halftone display, full-color display is possible, and if only black-and-white display is possible, eight-color multicolor display is possible.

【0020】

FIG. 1 is a diagram showing a schematic configuration of a liquid crystal display device 1 which is an embodiment of the present invention. The liquid crystal display device 1 drives the reflective liquid crystal display element 2, the light selection means 3 laminated on the reflective liquid crystal display element 2, the drive circuit 4 for driving the reflective liquid crystal light element 2, and the light selection means 3. The filter drive circuit 5 is configured to include, and a display control circuit 6 that controls the drive circuit 4 and the filter drive circuit 5 in order to display a desired color on the liquid crystal display device 1.

【0021】

The reflective liquid crystal display element 2 is an active matrix type liquid crystal display element, and the transparent substrate 7 and the substrate 8 provided with the light reflecting means for reflecting the incident light from the transparent substrate 7 side are arranged so as to face each other. A liquid crystal 9 is interposed between the transparent substrate 7 and the substrate 8. One common electrode is formed on almost the entire surface of the transparent substrate 7 facing the substrate 8, and a plurality of display electrodes are formed in a matrix on the surface of the transparent substrate 8 facing the transparent substrate 7, and each electrode is formed. The overlapping area is the display area (pixels). In the reflective liquid crystal display element 2, the drive voltage from the drive circuit 4 is applied between the common electrode and the display electrode, and a predetermined display is performed. The drive circuit 4 is controlled by a display control signal from the display control circuit 6.

【0022】

In the light selection means 3, the cyan filter 19C, the magenta filter 19M, and the yellow filter 19Y are laminated in this order and arranged on the transparent substrate 7 side of the reflective liquid crystal display element 2. The cyan filter 19C forms transparent electrodes (not shown) over the entire surface of the pair of transparent substrates 10 and 11 facing each other, and a liquid crystal 12 containing a cyan dichroic dye, which will be described later, is interposed between the substrates 10 and 11. It is composed of. The magenta filter 19M forms transparent electrodes (not shown) over the entire surface of the pair of transparent substrates 13 and 14 facing each other, and a liquid crystal 15 containing a magenta dichroic pigment described later is interposed between the substrates 13 and 14, respectively. It is composed of. The yellow filter 19Y forms transparent electrodes (not shown) over the entire surface of the pair of transparent substrates 16 and 17 facing each other, and a liquid crystal 18 containing a yellow dichroic pigment, which will be described later, is interposed between the substrates 16 and 17. It is composed of.

【0023】

The cyan filter 19C, the magenta filter 19M, and the yellow filter 19Y are supplied with AC voltage from the AC power supply 21 via switching circuits 20C, 20M, and 20Y, respectively. The switching circuits 20C, 20M, and 20Y selectively apply an AC voltage to the cyan filter 19C, the magenta filter 19M, and the yellow filter 19Y based on the switching signal from the display control circuit 6, and drive each filter. By controlling the on / off of each filter in this way, red light, green light, and blue light, which are the three primary colors of the color, can be incident on the reflective liquid crystal display element 2. Table 1 below shows the correspondence between the driving state of each filter and the color of the incident light.

【0024】

[table 1]

<img file="JP2829149B2_D0001.tif" />【0025】

FIG. 2 is a timing chart showing the basic operation of the optical selection means 3. A voltage is applied to the cyan filter 19C during the period from time t1 to time t3. The liquid crystal molecule does not change its orientation state immediately when a voltage is applied, and requires a certain transition period τ. This period τ corresponds to the response recovery rate of the liquid crystal molecule to the electric field. Therefore, even if the application of the voltage is started at the time t1, the change of the orientation state of the cyan filter 19C actually stabilizes in response to the voltage at the time t2 after the transition period τ elapses. Therefore, in the period TR from the time t2 to the time t3, the transmitted light of the light selection means 3 becomes red light.

【0026】

Similarly, the application of voltage to each filter is repeated in the order of magenta filter 19M, yellow filter 19Y, cyan filter 19C, and so on. As a result, the transmitted light becomes green light in the period TG, the transmitted light becomes blue light in the period TB, and so on, and so on, red light, green light, blue light, red light, and so on.

【0027】

FIG. 3 is a circuit diagram showing the basic configuration of the drive circuit 4. In FIG. 3, the capacitor 31 represents a liquid crystal in one display area (one picture element) in the reflective liquid crystal display element 2. The drive circuit 4 includes a signal scanning unit 32, a signal holding capacitor 33, and a picture element driving unit 34. The signal scanning unit 32 is an N-channel MOS transistor 36, and the scanning signal VD from the display control circuit 6 is given to the gate, the drive signal VS is given to the source, and the drain is the signal holding capacitor 33 and the element drive. It is connected to the buffer circuit 35, which is a unit 34. The liquid crystal drive voltage V0 is supplied to the buffer circuit 35, and the output voltage from the buffer circuit 35 is applied to the liquid crystal 31.

【0028】

When the high-level scanning signal VD is given to the gate of the transistor 36, the transistor 36 is turned on and the drive signal VS is given to the liquid crystal 31 via the buffer circuit 35. Further, the drive signal VS is also given to the signal holding capacitor 33, and the drive signal VS is held by the signal holding capacitor 33 until the next scanning signal VD is given to the gate of the transistor 36.

【0029】

On the other hand, in the active matrix type reflective liquid crystal display element 2, assuming that the number of scanning electrodes (number of gate electrodes) is N and the number of signal electrodes (number of source electrodes) is M, the following two driving methods are proposed as driving methods. Will be done.

【0030】

FIG. 4 is a timing chart for explaining the first driving method which is a premise of the present invention. In this first driving method, N scanning electrodes are scanned in an extremely short time as compared with the period τ + period TR (TG, TB), and a desired charge is injected into N × M pixels. This is a method of displaying the period TR, TG, and TB at almost the same timing.

【0031】

As shown in FIG. 4 (1), first, in the period τ, all N scanning electrodes of the reflective liquid crystal display element 2 are scanned, and charges are sequentially injected into N × M pixels. A desired drive signal is applied to the signal electrode from the start time of the scanning period τ, and a predetermined voltage is applied to the liquid crystal.

【0032】

As described above, the liquid crystal molecules require a certain transient period from the orientation state when no voltage is applied to the orientation state when a voltage is applied and stable. Therefore, as shown in FIG. 4 (2), a period W1 is required for the reflective liquid crystal display element 2 to reach a stable display state. The period W1 is the sum of the period τ and the response time of the display mode applied to the reflective liquid crystal display element 2.

【0033】

Therefore, in the display period DR, DG, DB, ... From the start time of the scanning period of the liquid crystal display element 2 to the time after the elapse of the period W1 to the start time of the next scanning period, red, green, and blue 3 The colors are displayed in sequence. As a result, by selecting transmitted light for each picture element, multicolor display of eight colors is possible by the principle of additive color mixing. Further, when the liquid crystal display element 2 is capable of halftone display, full color display is possible.

【0034】

In FIG. 4, the transition period τ in the optical selection means 3 is selected as the period for scanning all N scanning electrodes, but the period τ is not limited to the period τ, and the scanning period τ is as short as possible. It is preferable to obtain a good color and a bright display. Further, since light leakage occurs in which two of the three colors are mixed in the scanning period τ, the display of the liquid crystal display element 2 is black in this period τ, and the desired display pattern is displayed in the periods TR, TG, and TB. Scanning may be performed. However, even in this case, in order to obtain a brighter display, it is desirable that the transition period τ and the scanning period τ are as short as possible. Further, in FIG. 4, the period W1 is the sum of the scanning period τ and the response time of the display mode applied to the liquid crystal display element 2, and since it is necessary to shorten the period W1, the response speed of the display mode is combined with the scanning period τ. Is also desirable to be fast.

【0035】

FIG. 5 is a circuit diagram showing a basic configuration of a drive circuit 4a used when executing a second drive method according to an embodiment of the present invention, and FIG. 6 is a timing for explaining the second drive method. It is a chart. The drive circuit 4a shown in FIG. 5 is similar to the drive circuit 4 shown in FIG. 3 described above, and the corresponding configurations are designated by the same reference numerals. In the drive circuit 4a, two signal holding capacitors 33a and 33b are provided to hold the drive signal from the signal scanning unit 32, and a switch that switches and gives the drive signal from the signal scanning unit 32 to the capacitors 33a or 33b. A SW1 and a switch SW2 that switches and gives a drive signal held in the capacitor 33a or 33b to the element drive unit 34 are provided.

【0036】

The second drive method is a method of writing the drive signal of the next screen to the drive circuit 4a while performing a desired display by using the drive circuit 4a. As a result, as compared with the first drive method described above, since the drive signal has already been taken into the drive circuit 4a, it is not necessary to perform high-speed scanning, and therefore, the high speed of the scanning electrode drive circuit and the signal electrode drive circuit is high. The requirements for properties are relaxed.

【0037】

With reference to FIGS. 5 and 6, while each liquid crystal (picture element) 31 is driven by the drive signal information stored in the capacitor 33b, the next picture element is passed through the signal scanning unit 32 and the switch SW1. The drive signal information to be displayed on the capacitor 33a is stored in the capacitor 33a. Such an operation is performed for all N × M elements, and after the drive signal information to be displayed next to each pixel is taken into the liquid crystal display element 2 (drive circuit 4), each picture is taken at an appropriate timing. The switch SW1 provided corresponding to the element is switched to the terminal a1, and the switch SW2 is switched to the terminal b2. By switching the switches SW1 and SW2, the display screen of the liquid crystal display element 2 is instantly switched to the next screen. After that, the drive signal information to be displayed next is stored in the capacitor 33b, and the drive signal information is taken into the liquid crystal display element 2 (drive circuit 4). Hereinafter, color display is possible by repeating the above operation and synchronizing the screen switching timing, that is, the switching timing of the switches SW1 and SW2 with the timing of the color change of the optical selection means 3. In FIG. 6 (4), the period W2 corresponds to the response characteristics of the display mode applied to the liquid crystal display element 2, and is preferably shorter.

【0038】

In FIG. 2, two colors (blue and red, red and green, green and blue) are mixed by appropriately timing the application of each applied voltage to the cyan filter 19C, the magenta filter 19M, and the yellow filter 19Y. It is possible to avoid it, and accordingly, the start timing of the period W1 shown in FIG. 4 and the period W2 shown in FIG. 6 can be appropriately designed. Further, in the reflective liquid crystal display element 2, light reflection on a layer other than the light reflecting means, for example, on a transparent substrate, a transparent electrode interface, and various thin film interfaces is a problem, and an antireflection film is formed at these points. This is effective in improving the contrast characteristics.

【0039】

The problem here is the response characteristics of each liquid crystal element. Since the lower limit of the frequency at which the human eye does not feel the flicker of the display is about 30 Hz, in the above-described embodiment, the permissible time displayed corresponding to each of the red, blue, and green colors is about 10 msec. In order to perform sufficient display within 10 msec, the light selection means 3 and the reflective liquid crystal display element 2 are required to have a response speed of several msec or less and to realize color modulation and display. ..

【0040】

As a result of examining various liquid crystal display elements in consideration of the above response characteristics, the present inventor considers the liquid crystal display modes as a phase transition mode in which a dichroic dye is added, a polymer-dispersed liquid crystal display mode, and a ferroelectricity. It has been found that the liquid crystal display mode is preferable, and the active matrix drive type liquid crystal display element is preferable as the reflective liquid crystal display element. In particular, in the active matrix drive type liquid crystal display element, a two-terminal type active element such as an MIM or a diode, a thin film transistor (TFT) using a-Si, p-Si, etc., a single crystal silicon or a single crystal GaAs was used. A 3-terminal active element such as a MOS-FET, a plasma address type liquid crystal display element (TSBuzak; SID90 DIGEST, P.420) or an optical scanning type liquid crystal display element can be used. Of these, a-Si TFT-LCD and p-Si are particularly important for mass-producing high-definition displays. TFT-LCD and single crystal silicon MOS-FET-LCD are preferable. Further, as the display mode, a phase transition mode (white tailor mode) in which a polarizing plate-free dichroic dye is added or a polymer-dispersed liquid crystal display mode is desirable in order to obtain a bright reflective display.

【0041】

The light selection means 3 has a structure in which a plurality of liquid crystal elements having transparent electrodes formed over the entire display surface are formed, and each liquid crystal element absorbs light at a different wavelength in the visible light region wavelength. Presented when voltage is applied or when no voltage is applied.

【0042】

Such a light absorption function can be realized by a so-called guest host liquid crystal in which a dichroic dye such as anthraquinone type, azo type, azomethine type, styryl type, or merocyanine type is added to the host liquid crystal.

【0043】

For example, in order to obtain each transmitted light of red, green, and blue by using the light selection means 3, cyan, magenta, and yellow dyes may be used, and as an example, the following dyes are generally known.

【0044】

[Chemical 1]

<img file="JP2829149B2_D0002.tif" />【0045】

[Chemical 2]

<img file="JP2829149B2_D0003.tif" />【0046】

[Chemical 3]

<img file="JP2829149B2_D0004.tif" />【0047】

The above dyes are mixed with biphenyl-based liquid crystals, phenylcyclohexane-based liquid crystals, cyclohexylcyclohexane-based liquid crystals, phenylester-based liquid crystals, phenylpyrimidine-based liquid crystals, phenyldioxane-based liquid crystals, trans-based liquid crystals, fluorine-based liquid crystals, and other liquid crystals, or a mixture thereof. A cyan filter 19C, a magenta filter 19M, and a yellow filter 19Y constituting the light selection means 3 are formed by three types of guest host liquid crystals added in appropriate amounts to the liquid crystal system.

【0048】

Furthermore, as described above, in order to meet the demand for high-speed response characteristics, as a result of examination from the viewpoint of high-speed response characteristics, a chiral nematic liquid crystal was added to the above guest host liquid crystal, and d / p 2 (d; cell thickness, It was confirmed that high-speed responsiveness (several msec or less) can be achieved by setting p; intrinsic spiral pitch) and d 10 μm and containing at least phenylcyclohexane-based liquid crystal or fluorine-based liquid crystal as the host liquid crystal material.

【0049】

This host liquid crystal can be used in combination with the substrate orientation if the dielectric anisotropy (Δε) is positive or negative, and it is positive at low frequencies and negative at high frequencies depending on the drive frequency (2). (Frequency drive liquid crystal) is also effective in obtaining a high-speed response.

【0050】

Further, as another realization method, the above-mentioned guest host material or the guest host material to which the chiral nematic liquid crystal is added is microencapsulated and dispersed in the polymer material, or directly dispersed in the network-like polymer matrix. In addition, even if the structure is a so-called polymer-dispersed liquid crystal, or even if the liquid crystal is impregnated with an aggregate of ultrafine fibers that perform the same operation, high-speed response can be easily realized. be able to.

【0051】

It is also possible to use a ferroelectric liquid crystal, but in this case, since a polarizing plate is required, it is necessary to consider that the brightness of the display is impaired. Although the three-layer laminated type light selection means 3 is illustrated in this embodiment, the present invention is not limited to this, and the type of dye and the number of laminated layers can be designed according to a desired display color.

【0052】

High-speed scanning is required for the active matrix substrate that constitutes the reflective liquid crystal display element 2. In this regard, MOS-FETs and p-Si TFTs (reflection type structures) using a single crystal silicon substrate with high mobility are desirable as active elements. Further, if the liquid crystal display element has a small number of scanning electrodes, a-Si TFT (reflective structure), which is advantageous for mass productivity and upsizing, can also be used.

【0053】

In the above-mentioned single crystal silicon MOS-FET and p-Si TFT, the resistance value is extremely low because the liquid crystal drive circuit can be integrated in the periphery and the N channel and P channel can be easily controlled. Even if the liquid crystal cannot be supported by the parallel addition of the above, it can be handled by forming a switching element for a picture element having a CMOS structure as shown in FIG. Although the signal scanning unit 32 is composed of N-channel MOS transistors in FIG. 3 described above, it can also be configured with P-channel MOS transistors.

【0054】

Furthermore, the mobility of single crystal silicon MOS-FETs is extremely higher than that of p-Si and a-Si (mobility μ = 500 cm).² / V S), the fastest scanning is possible, the display capacity can be increased, and the memory circuit and arithmetic circuit can be built into the liquid crystal display element by applying conventional semiconductor technology. By forming intelligent switching elements on the peripheral drive circuits, the peripheral drive circuit mounting area can be eliminated and the display can be made smaller, and those liquid crystal panels can be mounted on the substrate. By laminating a plurality of them on the upper surface (for example, a quartz substrate), it is possible to cope with an increase in the display area.

【0055】

As the display mode of such a reflective active matrix type liquid crystal display element, the phase transition mode to which the above-mentioned dichroic dye is added or the polymer-dispersed liquid crystal can be applied. In this case, the dichroic dye is used. It is necessary to mix it so that it becomes black.

【0056】

FIG. 7 is a cross-sectional view showing an element structure when the reflective liquid crystal display element 2 is formed as a silicon single crystal active substrate. The fabrication process applied MOS semiconductor process technology.

【0057】

From one writing to the next writing period, a storage capacitor is formed between the silicon substrate 8 via the insulating film and p-Si41 as a means for assisting the retention of the electric charge injected into the picture element.

【0058】

In addition, the pixel electrode 42, which is also a reflective film, uses aluminum (Al), and its unevenness is realized by applying a resist on the insulating layer (SiNx) 43 under aluminum and forming the unevenness on the surface with hotoriso. There is.

【0059】

Liquid crystal 9 is a black guest host liquid crystal ZLI-2327 manufactured by Merck &amp; Co., Ltd., and by adding a small amount of CB-15 manufactured by Merck &amp; Co., Ltd., d / p = 4 (d; cell thickness, p; spiral pitch). Adjusted to be. An 8 μm spacer is used to adjust the substrate spacing, and the substrate alignment process is a vertical alignment process of polyimide. The number of picture primes is 240 x 380.

【0060】

In FIG. 7, 44 indicates the field oxide film, 45 indicates the source line, and 46 indicates the common electrode.

【0061】

On the other hand, as filters 19C, 19M, 19Y, the host liquid crystal is ZLI-1840 manufactured by Merck &amp; Co., Ltd., and G209, G232, and D35 manufactured by BDH Co., Ltd. are added in 2 wt%, and as a chiral material. CB-15 was added to form a three-layer laminated filter. The d / p at this time is about 5, and the substrate alignment treatment is a vertical alignment treatment of polyimide. When the above filter was superposed on the liquid crystal display element shown in FIG. 7 and driven at the timing shown in FIG. 4, good color display was confirmed.

【0062】

In the liquid crystal element structure shown in FIG. 7 described above, a case where a polymer-dispersed liquid crystal is used as the liquid crystal will be described. For the reflective active matrix substrate, a solution of 2-ethylhexyl acrylate (monoma): urethane acrylate oligoma: ZLI-2327 = 16: 24: 60 mixed uniformly with the photopolymerization initiator is sealed in the liquid crystal element. After that, it was created by irradiating with UV (ultraviolet).

【0063】

On the other hand, using the above dye and host liquid crystal (ZLI-1840), three layers of liquid crystal elements (filters) were prepared by mixing with a solution outside the liquid crystal in the same ratio as described above. When these liquid crystal display elements and filters were superposed, good color operation characteristics could be confirmed.

【0064】

Further, in the liquid crystal element structure shown in FIG. 7 described above, the P channel and the N channel are controlled so that the reflective active matrix substrate becomes an equivalent circuit to the circuit shown in FIG. 3 described above, and a CMOS configuration is realized. Even in this case, good color display characteristics were confirmed.

【0065】

FIG. 8 is a circuit diagram showing still another configuration of the drive circuit 4b. The drive circuit 4b shown in FIG. 8 is similar to the drive circuit 4a shown in FIG. 5 described above, and the corresponding configurations are designated by the same reference numerals.

【0066】

In the drive circuit 4b, switching circuits 37a and 37b are provided in place of the switches SW1 and SW2 provided in the drive circuit 4a. In the drive circuit 4b, the liquid crystal 31 can be driven by the drive signal stored in the capacitor 33a or 33b by giving a high level or low level signal to the terminal VC. Therefore, at the same time as displaying the screen of the liquid crystal display element 2, it is possible to accumulate the drive signal to be displayed next, and the drive method shown in FIG. 6 described above can be implemented. The switching circuits 37a and 37b are provided with N-channel MOS transistors 37a2 and 37b1 as described in connection with FIG. 3 above, and as is clear from FIG. 8, P-channel MOS transistors 37a1 and 37b2 are provided. Used. That is, the switching circuit 37a is provided with a P-channel MOS transistor 37a1 which is a conductive type on one side and an N-channel MOS37a2 which is a conductive type on the other side, and capacitors 33b and 33a are connected to and driven by these transistors 37a1 and 37a2, respectively. Hold the signal. Further, in the switching circuit 37b, the output of the capacitor 33b is connected to the N-channel MOS transistor 37b1 of the other conductive type, and the output of the capacitor 33a is given to the P-channel MOS transistor 37b2 of the other conductive type. The outputs of these transistors 37b1 and 37b2 are both given to buffer 35. High-level and low-level signals are alternately given to the terminal Vc so that the drive signal for each screen corresponding to the filter is given from the capacitors 33b, 33a to the buffer 35, and for this purpose the transistors 37a1,37a2, The above-mentioned high-level and low-level signals are alternately given to the control terminals that are the gates of 37b1 and 37b2.

【0067】

As described above, according to this embodiment, since various display colors can be displayed in one picture element, the resolution is improved and the rear light source (so-called backlight) is higher than the conventional color display by attaching a micro color filter. ) Is unnecessary, and a thin and lightweight color liquid crystal display becomes possible. Therefore, it is extremely effective for various information devices such as notebook personal computers, palmtop personal computers, and game machines.

【0068】

[Effect of the invention]

According to the invention of claim 1, the electric charge held by the signal holding means is not directly applied to the liquid crystal, but the voltage is applied to the liquid crystal through the buffer, so that the capacity held by the signal holding capacity is lowered. It is possible to obtain a good display regardless of the size of the signal holding capacity.

【0069】

Further, according to the invention of claim 2, the entire screen of the liquid crystal display element can be switched to the next screen all at once, and a moving image with high display quality can be displayed.

【0070】

Further, according to the invention of claim 3, time-division color display is possible, and a better display state can be obtained with higher resolution than color display of area division. Further, according to the invention of claim 4, when a common signal is supplied to each transistor and a drive signal corresponding to the pixel is supplied from one signal holding means to the pixel, the other signal holding means is used. It is possible to obtain a switching means for supplying a drive signal corresponding to the display on the next screen from the switching element, and it is not necessary to generate a plurality of control signals.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the basic structure of the liquid crystal display device 1 which is one Example of this invention.

[Figure 2]

It is a timing chart explaining the driving method of the light selection means 3 of the liquid crystal display device 1.

[Fig. 3]

It is a circuit diagram which shows the basic structure of the drive circuit 4.

[Fig. 4]

It is a timing chart for demonstrating the first driving method of the liquid crystal display device 1 which is the premise of this invention.

[Fig. 5]

It is a circuit diagram which shows the structure of another drive circuit 4a.

[Fig. 6]

It is a timing chart for demonstrating the second driving method of the liquid crystal display device 1 of one Example of this invention.

[Fig. 7]

It is sectional drawing which shows the element structure of the reflective liquid crystal display element 2 used in the liquid crystal display device 1.

[Fig. 8]

It is a circuit diagram which shows the structure of the other drive circuit 4b used for the liquid crystal display device 1.

[Explanation of symbols]

1 Liquid crystal display device 2 Reflective liquid crystal display element 3 Light selection means 4 drive circuit 5 Filter drive circuit 6 Display control circuit 19C cyan filter 19M magenta filter 19Y yellow filter