JP2007328355A - Reflection type liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a liquid crystal display device of lightweightness, small size and low electric power consumption by compensating optical anisotropy of a liquid crystal material, thereby improving a visual field angle characteristic and improving the response speed of the liquid crystal material. <P>SOLUTION: The liquid crystal display device is provided with an electrode for display and a reference electrode on one substrate and further, the liquid crystal display device is formed as a reflection type, and the alignment of the liquid crystal material is made into HAN (Hybrid Alignment Nematic) type, and thereby the optical anisotropy of the liquid crystal material is compensated and the response speed is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The invention disclosed in this specification relates to an active matrix liquid crystal display device.

  Liquid crystal display devices are used in a wide range of fields such as computers, calculators, and watches as lighter and more compact display devices than CRTs. The liquid crystal display device has the optical properties (interference, scattering, diffraction, optical rotation, absorption, etc.) of the liquid crystal material due to the change in the alignment state and phase transition of the liquid crystal molecules in response to the application of an external field (electric field, heat, etc.) The principle of operation is to change.

  As for the structure and driving method of a general liquid crystal display device, a liquid crystal material is sandwiched between two substrates, at least one of which has translucency and a distance of 1 to several tens of μm (hereinafter referred to as a liquid crystal panel). In other words, an electric field is applied to the liquid crystal material by the electrodes formed on both or one of the two substrates to control the alignment state of the liquid crystal molecules for each pixel in the substrate surface and transmit the liquid crystal panel. Image display is performed by controlling the amount of light. At this time, depending on which of the above optical properties is used, for example, a polarizing plate is provided on the outside of the liquid crystal panel, so that a configuration corresponding to the operation mode is adopted.

  Currently, the TN (twisted nematic) type or STN (super twisted nematic) type is widely used in liquid crystal display devices, and these are optical properties such as optical rotation of liquid crystal materials and interference of birefringent light, respectively. In any case, it is necessary to provide a polarizing plate.

  In addition, when displaying an image on the above-mentioned liquid crystal display device, various methods have been proposed to control the operation of a large number of pixels at the same time. Among them, active matrix driving enables high-quality and high-density display. Is widely used. The purpose of this is to provide non-linear active elements (diodes, transistors, etc.) in each pixel so that each pixel is in an electrically independent relationship, eliminating interference of extra signals and realizing high image quality. To do. According to this method, each pixel can be viewed as a capacitor to which an electrical switch is connected. Accordingly, the charge can be injected / extracted to / from the pixel by turning on / off the switch as necessary. Further, when the switch is turned OFF, the charge is held in the pixel, so that it is possible to impart memory characteristics.

(Problems of conventional technology)
(1) Power consumption of liquid crystal display device Since any liquid crystal display device does not emit light, the liquid crystal material itself does not emit light. The light incident on the device is utilized (reflection type).

  In the case of the transmissive type, if the light emission luminance of the light source is increased, a brighter display device can be realized, but the power consumption of the entire device increases. The light source occupies most of the power consumption of the transmissive liquid crystal display device (ratio of power consumption: liquid crystal panel: light source = 1: 100 to 1: 1000), and low power consumption is the power consumption of the light source. The point is how to reduce the value. However, in the TN type and STN type, a configuration using two polarizing plates is generally used, and in this case, the transmittance of the liquid crystal panel is considerably lowered. Therefore, in order to realize a bright display, it is necessary to increase the luminance of the light source. There is. As long as it is necessary to maintain a certain level of brightness, a significant reduction in power consumption cannot be expected unless a light source with a sufficiently high luminous efficiency is used.

  On the other hand, in the case of a reflective liquid crystal display device, since there is no special light source in the device, low power consumption and downsizing are possible, which can be said to be a more ideal display device. However, as long as light from the surroundings is used, in order to obtain a brighter display device with a small amount of light, it is necessary to use light efficiently. When the reflective type is the TN type or STN type, the brightness of the device is further reduced because the light source is not used.

(2) Response speed As the image to be displayed becomes higher in definition, it is desired to increase the response speed of the liquid crystal material. However, in the case of the TN type liquid crystal, the response speed is about several tens of ms for the TN type and about 100 ms for the STN type. In these cases, when the image formed on the screen moves in the screen, the image has a tail. The display state is not so good, such as it looks like pulling. In order to improve such a phenomenon, it is necessary to use a liquid crystal material having a higher response speed or to set an operation mode that realizes a higher response speed.

(3) Viewing angle characteristics In addition, when the TN type and STN type liquid crystal display devices are viewed obliquely, phenomena such as a reduction in contrast and inversion of halftone are observed. This is because the polarization state of incident light from an oblique direction changes in the liquid crystal layer in the liquid crystal display device. To solve this problem, pixel electrode division methods, alignment division methods, and the like have been proposed, but they have not been fundamentally solved.

  The present invention provides a liquid crystal display device which is improved in the above-mentioned (1) power consumption, (2) response speed and (3) viewing angle characteristics, is light and small, and can display high image quality with low power consumption. It is.

  In order to solve the above-described problems, the present invention provides a first insulating substrate having translucency, a second insulating substrate facing the substrate and having light reflectivity, the first substrate, and the second substrate. In a liquid crystal display device having at least a liquid crystal material sandwiched between two substrates, a first pixel electrode on the first substrate, a wiring for applying an electric signal to the electrode, and the pixel electrode and the wiring are insulated The liquid crystal display device is characterized in that the second pixel electrode formed has a wiring for applying an electric signal to the electrode.

  The present invention also includes a first insulating substrate having translucency, a second insulating substrate facing the substrate and having light reflectivity, and sandwiched between the first substrate and the second substrate. In a liquid crystal display device having at least a liquid crystal material, a first pixel electrode on the first substrate, a wiring for applying an electric signal to the electrode, and a second pixel electrode insulated from the pixel electrode and the wiring And a wiring for applying an electric signal to the electrode, and the alignment state of the liquid crystal material is different between the vicinity of the first substrate and the vicinity of the second substrate. .

  The present invention also includes a first insulating substrate having translucency, a second insulating substrate facing the substrate and having light reflectivity, and sandwiched between the first substrate and the second substrate. In a liquid crystal display device having at least a liquid crystal material, a first pixel electrode on the first substrate, a wiring for applying an electric signal to the electrode, and a second pixel electrode insulated from the pixel electrode and the wiring And a wiring for applying an electric signal to the electrode is formed, and the liquid crystal material is parallel or substantially parallel to the substrate in the vicinity of the first substrate and perpendicular or substantially vertical in the vicinity of the second substrate. A liquid crystal display device characterized by being oriented.

  The present invention also includes a first insulating substrate having translucency, a second insulating substrate facing the substrate and having light reflectivity, and sandwiched between the first substrate and the second substrate. In a liquid crystal display device having at least a liquid crystal material, a first pixel electrode on the first substrate, a wiring for applying an electric signal to the electrode, and a second pixel electrode insulated from the pixel electrode and the wiring And a wiring for applying an electric signal to the electrode, and a non-linear element is connected to either the first pixel electrode or the second pixel electrode. is there.

  The present invention also includes a first insulating substrate having translucency, a second insulating substrate facing the substrate and having light reflectivity, and sandwiched between the first substrate and the second substrate. In a liquid crystal display device having at least a liquid crystal material, a first pixel electrode on the first substrate, a wiring for applying an electric signal to the electrode, and a second pixel electrode insulated from the pixel electrode and the wiring And a wiring for applying an electrical signal to the electrode is formed, and the liquid crystal material is driven by an electric field having a component parallel to the substrate.

  The structure of the liquid crystal display device of the present invention is shown in FIG. In the figure, (101) is a first substrate, on which a display electrode (110) and a reference electrode (111) are formed. (102) is a second substrate and a reflective layer (103 is formed on the substrate. (104) is a biaxial film, (105) is a polarizing plate, (106) is a liquid crystal molecule. (107) is a polarized light. The optical axis direction of the plate, (108) is the alignment processing direction when the first substrate is uniaxially aligned, and (109) is a non-linear type formed when active matrix driving is performed in the liquid crystal display device of the present invention. Elements (112) are scanning (gate) lines, and (113) is a signal (source) line.

  For the first insulating substrate (101), a material having translucency and a certain degree of strength against external force, for example, an inorganic material such as glass or quartz is used. When a TFT is formed on a substrate, non-alkali glass or a quartz substrate is used. For the purpose of reducing the weight of the liquid crystal panel, a film having low birefringence, such as PES (polyethylene sulfate), can also be used.

  The second substrate (102) may be any material having a certain strength against external force and a function of reflecting light. For example, a film in which a thin film (103) such as Al or Cr is formed on the surface of the first substrate may be used. It is also possible to use a Si substrate.

  In the present invention, in order to operate the liquid crystal material, an electric field having a component parallel to the substrate (hereinafter referred to as a lateral electric field) is generated in the liquid crystal cell, and the alignment state of the liquid crystal molecules is determined by the intensity of the lateral electric field. Took the way to control. Therefore, in the present invention, two types of electrodes, the display electrode (110) and the reference electrode (111), which are electrically insulated, are formed on the first substrate. The two types of electrodes may be made of a conductive material such as Al or Cr. Further, if a transparent material such as ITO is used for the electrode, the aperture ratio of the pixel can be improved. The basic structure of the electrode is such that the display electrode (110) and the reference electrode (111) are engaged with each other with a gap as shown in FIG. Moreover, you may utilize the reflecting plate formed on the 2nd board | substrate as an electrode as needed.

  As an operation mode of the liquid crystal display that can be used in the present invention, an OCB (optically compensated birefringence) mode is used to improve the viewing angle. The OCB mode is such that the refractive index is effectively equal in the three-dimensional direction. The basic configuration of the OCB mode is a configuration in which a bend cell and a biaxial film are inserted between two polarizing plates, and the refractive index is compensated in a three-dimensional direction. The alignment state of the liquid crystal molecules in the bend cell is such that the major axis of the liquid crystal molecules in the liquid crystal panel is parallel to the substrate in the vicinity of the pair of substrate surfaces, and the major axis is perpendicular to the substrate as it goes from one substrate to the other. The orientation is such that it rotates 180 °.

  However, if the above configuration is used as it is, two polarizing plates are used, and a bright liquid crystal display device cannot be realized. Therefore, in the present invention, a reflective liquid crystal display device is used, and only one polarizing plate is required. This is because the orientation of the liquid crystal molecules in the OCB mode is in the form of a mirror image centered on the middle of a pair of substrates, and the orientation state of the liquid crystal material is HAN (hybrid alignment nematic) when this axis is turned to be a reflection type. This utilizes the same configuration as the mode liquid crystal display device. In the HAN mode, the alignment is controlled so that the liquid crystal molecules are vertically aligned on one substrate and horizontally aligned on the other substrate. The alignment state of the liquid crystal molecules 106 when no electric field is applied is shown in FIG. As the liquid crystal material, a nematic material having a positive or negative dielectric anisotropy is used. As for the alignment treatment, a monobasic chromium complex treatment or a silane coupling material may be applied on the substrate surface to be vertically aligned (not shown). A known rubbing process or the like may be performed by applying polyimide or the like (not shown) on the substrate surface to be horizontally aligned.

  The liquid crystal material may be driven by a multiplex method or an active matrix method. In the multiplex method, only two types of display electrodes and reference electrodes need be formed on the first substrate. However, in the case of the active matrix method, a non-linear element (109) such as a thin film transistor (for example) can be used as a switching element. TFT) or a diode is formed for each pixel. As the TFT, a transistor using amorphous silicon or poly (polycrystalline) silicon as an active layer can be used. The non-linear element (109) is connected to the display electrode (110).

  As a further advanced configuration, there is a configuration in which the peripheral drive circuit is formed of thin film transistors and integrated on a substrate. Since this configuration is obtained as an integrated structure in which the pixel region and the peripheral circuit region are integrated on the substrate, the liquid crystal panel can be more easily used.

  Further, a black matrix is formed (FIG. 3 (328)) on a portion not related to display (wiring, non-linear element portion, peripheral driver circuit) in order to improve display characteristics. As the black matrix, it is possible to use a metal such as Cr or a material in which a black substance is dispersed in a transparent substance in order to prevent a decrease in contrast due to irregular reflection inside the liquid crystal display device. In particular, an inorganic material such as glass or quartz or an organic material such as a resin can be used as the transparent substance, but a resin material is preferably used in terms of ease of manufacture. As the resin material, an acrylic material or the like can be used. As the black substance, carbon black or a pigment can be used.

  The method for dispersing the black material in the resin material can be appropriately selected according to the black material to be used, and examples thereof include a stirrer stirring method, a ball mill method, and a three-roll method. Further, at the time of dispersion, it is possible to improve the dispersibility of the black material by adding a small amount of a dispersion aid such as a surfactant. The particle size of the black material to be dispersed is desirably 1 μm or less in view of dispersion stability and the purpose of thinning the black matrix layer.

  Further, the black matrix may be formed on the TFT substrate by the same method as that for forming a resist pattern in a normal photolithography method. First, the organic solution in which the black material is dispersed is applied onto the TFT substrate by a spin coating method or a printing method. Next, patterning is performed by a known photolithography method. Then post-bake at around 200 ° C.

  Further, according to the HAN mode shown in the present invention, the color can be controlled by controlling the voltage applied to the liquid crystal material. Therefore, there is no need to form a color filter used in a conventional liquid crystal display device.

  The substrate subjected to the alignment treatment in this manner is arranged so that the alignment treatment surface or the surface on which the TFT, the transparent electrode or the like is formed faces each other, and a liquid crystal material is sandwiched between the opposing substrates. Spacers or the like are dispersed on the pair of substrates so that the distance between the substrates is constant. The spacer used has a diameter of 1 to 10 μm. The pair of substrates is fixed with an epoxy adhesive or the like. The adhesive pattern is formed on the outer periphery of the substrate so that the pixel region and the peripheral drive circuit region are on the inside.

  By adopting the structure of the present invention, a bright display that does not require a backlight can be manufactured. In addition, unlike a conventional liquid crystal display device, it is possible to configure the device with a single polarizing plate. Therefore, power consumption can be reduced. Furthermore, the reduction of the driving voltage makes it possible to use a dry battery as a power source, which makes it easier to apply to various portable electric devices.

(Function)
In the liquid crystal display device, a display electrode and a reference electrode are provided on one electrode, and liquid crystal molecules are driven by an electric field parallel to the substrate. Further, by making the alignment of the liquid crystal molecules HAN type, the optical anisotropy of the liquid crystal material is compensated and the viewing angle characteristics are improved. Further, by adopting the above-mentioned orientation, the response speed is improved as compared with the conventional TN and STN types. Further, by forming a reflective plate on the other substrate, a reflective liquid crystal display device can be obtained, and it is not necessary to provide a light source in the device, so that power consumption can be reduced.

  A method for manufacturing a substrate of a liquid crystal display device in this embodiment will be described below. In this embodiment, a liquid crystal display device using a multiplex drive system is used. First, an ITO film having a thickness of 120 nm was formed and patterned on a glass substrate as a first insulating substrate. Next, an insulating film made of SiN was formed to 100 nm thereon. Further, 120 nm of ITO was formed thereon as a reference electrode and patterned. The electrode structure of the display electrode and the reference electrode is shown in FIG. Comb-shaped display electrode (110), reference electrode (111) vertical and horizontal electrode widths (203, 204, 205, 206) are each 10 μm, and the length of the meshing part (207) is 60 μm Further, the distance (208) between the display electrode and the reference electrode was set to 5 μm. Further, a Cr film having a thickness of 120 nm was formed on the second insulating substrate to provide a reflection function.

  In this embodiment, the liquid crystal molecules are arranged in HAN alignment. Therefore, alignment films (not shown) were formed on the first substrate (101) and the second substrate (102). A polyimide was formed on the first substrate (101) by a known spin coating method or DIP method. Next, in order to align the liquid crystal molecules so as to be parallel to the substrate, the polyimide film on the first substrate (102) was rubbed. The rubbing was performed in a direction parallel to the portion corresponding to the comb teeth of the reference electrode for display (108). A silane coupling agent was formed on the second substrate (102). As a result, the liquid crystal molecules on the second substrate surface were vertically aligned.

  The first substrate (101) thus formed and the second substrate (102) were superimposed to form a liquid crystal panel. The pair of substrates was made to have a uniform substrate spacing over the entire panel surface by sandwiching a spherical spacer (not shown) having a diameter of 3 μm between the substrates. Further, in order to bond and fix the substrates to the pair, they were sealed with an epoxy adhesive. The seal pattern surrounds the pixel region and the peripheral drive circuit region (not shown). Then, after cutting the pair of substrates into a predetermined shape, a liquid crystal material was injected between the substrates. As the liquid crystal material, nematic liquid crystal ZLI-2293 (Δε = + 10, 1 kHz, 20 ° C.) was used as a material having positive dielectric anisotropy.

  Next, the biaxial film (104) and the polarizing plate (105) were attached in this order on the first substrate. The direction of the optical axis (107) of the polarizing plate was arranged to make 45 ° with the rubbing direction.

  When this liquid crystal display device was operated, it was possible to perform display with a contrast of 100, a response speed of 2 ms, and a wide viewing angle at a driving voltage of 3V.

  A method for manufacturing a substrate of a liquid crystal display device using the active matrix circuit in this embodiment will be described below. The production process for obtaining the monolithic active matrix circuit of this embodiment will be described below with reference to FIG. This step is for the low temperature polysilicon process. The left side of FIG. 3 shows the TFT fabrication process of the drive circuit, and the right side shows the TFT fabrication process of the active matrix circuit. First, a silicon oxide film having a thickness of 100 to 300 nm was formed as a base oxide film (302) on a glass substrate (301) as a first insulating substrate. As a method for forming this silicon oxide film, a sputtering method or a plasma CVD method in an oxygen atmosphere may be used.

  Thereafter, an amorphous silicon film was formed to 30 to 150 nm, preferably 50 to 100 nm by plasma CVD or LPCVD. Then, thermal annealing was performed at a temperature of 500 ° C. or higher, preferably 500 to 600 ° C., to crystallize the silicon film or improve the crystallinity. After crystallization by thermal annealing, light (laser or the like) annealing may be performed to further increase crystallization. Further, at the time of crystallization by thermal annealing, as described in JP-A-6-244103 and JP-A-6-244104, an element (catalytic element) for promoting crystallization of silicon such as nickel may be added.

Next, the silicon film is etched to activate the TFT active layer (303) (for p-channel TFT) and (304) (for N-channel TFT) in the driver circuit on the island and the TFT (pixel TFT) in the matrix circuit Layer (305) was formed. Further, a silicon oxide gate insulating film (306) having a thickness of 50 to 200 nm was formed by sputtering in an oxygen atmosphere. As a method for forming the gate insulating film, a plasma CVD method may be used. When forming a silicon oxide film by plasma CVD, it was preferable to use dinitrogen monoxide (N ₂ O) or oxygen (O ₂ ) and monosilane (SiH ₄ ) as a source gas.

Thereafter, aluminum having a thickness of 200 to 600 nm was formed on the entire surface of the substrate by sputtering. Here, aluminum may contain silicon, scandium, palladium, or the like in order to prevent hillocks from being generated by a subsequent thermal process. Then, this is etched to form gate electrodes (307, 308, 309) (FIG. 3A). Thereafter, phosphorus is implanted into all island-like active layers by ion doping in a self-aligning manner using the gate electrode as a mask and phosphine (PH ₃ ) as a doping gas. The dose is 1 × 10 ^{12 to} 5 × 10 ¹³ atoms / cm ² . As a result, weak N-type regions (310, 311 and 312) are formed. (Fig. 3 (B))

Next, the photoresist mask (313) covering the active layer of the P-channel TFT and the active layer (305) of the pixel TFT are covered in parallel to the gate electrode up to a portion 3 μm away from the end of the gate electrode (309). A photoresist mask (314) is formed. Then, phosphorus is implanted again using phosphine as a doping gas by ion doping. The dose is 1 × 10 ^{14 to} 5 × 10 ¹⁵ atoms / cm ² . As a result, strong N type regions (source, drain) (315, 316) are formed. Of the weak N-type region (312) of the active layer (305) of the pixel TFT, the region (317) covered by the mask (314) remains weak N-type because phosphorus is not implanted in this doping. Become. (Figure 3 (C))

Next, the active layer (304, 305) of the N-channel TFT is covered with a photoresist mask (318), and diborane (B ₂ H ₆ ) is used as a doping gas to form the island-like region (303). Boron is injected. The dose is 5 × 10 ¹⁴ to 8 × 10 ¹⁵ atoms / cm ² . In this doping, since the dose of boron exceeds the dose of phosphorus in FIG. 5C, the weak N-type region (310) formed previously is inverted into a strong P-type region (319). By the above doping, strong N-type regions (source / drain) (315, 316), strong P-type regions (source / drain) (319), and weak N-type regions (low-concentration impurity regions) (317) are formed. . In this embodiment, the width x of the low-concentration impurity region (317) is about 3 μm. (Fig. 3 (D))

  Thereafter, thermal annealing was performed at 450 to 850 ° C. for 0.5 to 3 hours to recover the damage due to doping, activate the doping impurities, and recover the crystallinity of silicon. Thereafter, a silicon oxide film having a thickness of 300 to 600 nm was formed as an interlayer insulator (320) on the entire surface by plasma CVD. This may be a silicon nitride film or a multilayer film of a silicon oxide film and a silicon nitride film. Then, the interlayer insulating film (320) was etched by wet etching or dry etching to form contact holes in the source / drain.

Then, an aluminum film having a thickness of 200 to 600 nm or a multilayer film of titanium and aluminum is formed by sputtering. This was etched to form peripheral circuit electrodes / wirings (321, 322, 323) and pixel TFT electrodes / wirings (324, 325). Further, a silicon nitride film (326) having a thickness of 100 to 300 nm was formed as a passivation film by plasma CVD, and this was etched to form an interlayer film. Further, an ITO (327) film having a thickness of 120 nm was formed thereon as a display electrode, and was patterned to have the same pattern as the display electrode in Example 1.
Furthermore, a silicon nitride film (329) having a thickness of 100 to 300 nm is formed as a passivation film by plasma CVD, and ITO (not shown) is formed as a reference electrode to a thickness of 120 nm. Patterning was performed so as to be the same pattern as the reference electrode. (Figure 3 (E))

Next, a black matrix (328) is formed thereon. Here, the black matrix is the top layer, but ITO and the black matrix may be reversed. As a black matrix material, a solution in which carbon black having an average particle diameter of 100 nm was dispersed in an acrylic resin material was applied by spin coating or printing. Thereafter, prebaking was performed at 100 ° C. for 2 minutes, and then patterning was performed by a known photolithography method. At this time, irradiation with an intensity of ultraviolet light (20 mW / cm ² or more) higher than that used in normal patterning is performed, or after applying a black matrix, an oxygen blocking film is formed with PVA (polyvinyl alcohol) or the like. For the development, a developer in which TMAH was dissolved in water by 2.36% by weight was used. As a result, a black matrix having a thickness of 1 μm could be formed on the peripheral drive circuit, the pixel TFT, and the gate / source wiring. The aperture ratio of the pixel area was 60%.

  In this embodiment, the liquid crystal molecules are arranged in HAN alignment. Therefore, alignment films are formed on the first substrate and the second substrate. A polyimide was formed on the first substrate by a known spin coating method or DIP method. Next, in order to align the liquid crystal molecules so as to be parallel to the substrate, the polyimide film on the TFT substrate was rubbed. The rubbing was performed in a direction parallel to the portion corresponding to the comb teeth of the reference electrode for display. A silane coupling agent was formed on the second substrate. As a result, the liquid crystal molecules on the surface of the color filter substrate were vertically aligned.

  The TFT substrate thus formed and the counter substrate were overlapped to form a liquid crystal panel. The pair of substrates was made to have a uniform substrate spacing over the entire panel surface by sandwiching a spherical spacer having a diameter of 3 μm between the substrates. Further, in order to bond and fix the substrates to the pair, they were sealed with an epoxy adhesive. The seal pattern surrounds the pixel region and the peripheral drive circuit region. Then, after cutting the pair of substrates into a predetermined shape, a liquid crystal material was injected between the substrates. Nematic liquid crystal ZLI-2293 was used as the liquid crystal material.

  Next, the biaxial film (104) and the polarizing plate (105) were attached in this order on the first substrate. The direction of the optical axis (107) of the polarizing plate was arranged to make 45 ° with the rubbing direction.

  When this liquid crystal display device was operated, it was possible to perform display with a contrast of 100, a response speed of 2 ms, and a wide viewing angle at a driving voltage of 3V.

  In this example, an example in which color display is performed using the liquid crystal display device of Example 2 is shown. FIG. 4 shows a change in transmitted light intensity (554.6 nm) accompanying application of a pixel voltage in the liquid crystal display device in this example. As apparent from FIG. 4, the transmittance continuously changed with voltage application, and there was no clear threshold. In addition, when the change in hue was observed, it showed yellow green when no voltage was applied, green at 0.5 V, blue at 0.9 V, and red at 1.2 V.

  By utilizing this phenomenon and performing color display by controlling the pixel voltage in the liquid crystal display device of this embodiment, it becomes possible to perform multicolor display with a driving voltage of 3 V and a wide viewing angle.

1 schematically shows a liquid crystal display device of the present invention. The electrode structure of the liquid crystal display device of this invention is shown. 2 shows a cross section of a pixel TFT and a peripheral drive circuit of a liquid crystal display device of the present invention. The transmittance-applied voltage characteristic of the liquid crystal display device in Example 3 of the present invention is shown.

Explanation of symbols

101, 102 Substrate 103 Reflective layer 104 Biaxial film 105 Polarizing plate 106 Liquid crystal molecule 107 Polarizing plate optical axis 108 Rubbing direction 109 Non-linear element 110 Display electrode 111 Reference electrode 112 Scanning (gate) line 113 Signal (source) line 203 Display electrode (vertical) width 204 Display electrode (horizontal) width 205 Reference electrode (vertical) width 206 Reference electrode (horizontal) width 207 Length 208 of display electrode and reference electrode occlusion portion Display electrode and reference electrode width Interval 301 Substrate 302 Base film (silicon oxide)
303, 304, 305 Active layer 306 Gate insulating film (silicon oxide)
307, 308, 309 Gate insulating film / gate lines 310, 311, 312 Weak N-type regions 313, 314 Photoresist masks 315, 316 Strong N-type regions (source / drain)
317 Low-concentration impurity region 318 Photoresist mask 319 Strong P-type region (source / drain)
320, 329 Interlayer insulating films 321-325 Peripheral drive circuit, pixel TFT electrode / wiring 326 Silicon nitride film 327 Display electrode (ITO)
328 black matrix

Claims (8)

A first substrate having translucency, a second substrate facing the first substrate, and a liquid crystal sandwiched between the first substrate and the second substrate,
A first pixel electrode; a second pixel electrode insulated from the first pixel electrode; and a thin film transistor connected to the first pixel electrode or the second pixel electrode on the first substrate. And a scanning line and a signal line for inputting a signal to the thin film transistor, and a black matrix covering the scanning line, the signal line and the thin film transistor,
Having a reflective layer on the surface of the second substrate sandwiching the liquid crystal;
The liquid crystal is aligned parallel to or substantially parallel to the first substrate in the vicinity of the first substrate and perpendicular or substantially perpendicular to the second substrate in the vicinity of the second substrate. A reflective liquid crystal display device, wherein an alignment state is controlled by an electric field formed by the pixel electrode and the second pixel electrode. In claim 1,
The reflection type liquid crystal display device, wherein the black matrix is formed by dispersing a black substance in a transparent substance. In claim 2,
A reflective liquid crystal display device, wherein the black substance has a particle size of 1 μm or less. In claim 2 or claim 3,
The reflective liquid crystal display device, wherein the black substance is carbon black or a pigment. In any one of Claims 1 thru | or 4,
A reflective liquid crystal display device, wherein a passivation film is formed on the first pixel electrode, and the second pixel electrode is formed on the passivation film. In claim 5,
The reflective liquid crystal display device, wherein the passivation film is a silicon nitride film. In any one of Claims 1 thru | or 6,
The reflective liquid crystal display device, wherein the first pixel electrode and the second pixel electrode have translucency. In any one of Claims 1 thru | or 7,
The reflection type liquid crystal display device, wherein the first pixel electrode and the second pixel electrode are arranged to be engaged with each other with a space therebetween.

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