JPH0980464A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device which has high reflectivity and opening rate and with which good color display is executable. SOLUTION: This liquid crystal display device includes a pair of substrates 11a, 11b which are respectively formed with active elements for controlling the potential information applied on transparent electrodes and wirings and liquid crystal cells which are held between a pair of these substrates 11a, 11b and are repeatedly successively laminated with at least once liquid crystal layers 14a to 14c and transparent electrode layers 15 on a reflection plate 13. The liquid crystal layers 14a to 14c are composed of guest-host liquid crystals contg. dyestuff molecules and liquid crystal molecules. The respective transparent electrode layers 15 and the active elements are electrically connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a reflective liquid crystal display device.

[0002]

2. Description of the Related Art OA for personal computers, word processors, EWS (Engineering Work Station), etc.
Display device; calculator, electronic book, electronic notebook, PDA (Pe
Display devices for rsonal Digital Assistants); display devices such as mobile TVs, mobile phones, and mobile FAXes place great importance on portability and need to be battery-powered, so low power consumption is desirable. Conventionally, as a thin display device, a liquid crystal display device (LCD), a plasma display, a flat CRT and the like are known. Among them, the liquid crystal display device is most suitable for the demand for low power consumption and has been put to practical use.

Of the liquid crystal display devices, the type in which the display surface is viewed directly is called the direct-view type. The direct view type liquid crystal display device includes a transmissive type in which a light source such as a fluorescent lamp is incorporated on the back surface and a reflective type in which ambient light is used. Among them, the transmissive liquid crystal display device requires a backlight and is not suitable for low power consumption. This is because the power consumption of the backlight is 1 W or more and the battery can be used for only 2 to 3 hours. Therefore, the reflective liquid crystal display device is most popular as a display for portable information equipment.

In a reflection type liquid crystal display device, a reflection plate having a satin-finished surface, a polarizing plate, and a reflection plate made of aluminum foil are laminated and attached to a glass substrate on the back surface. Since such a reflective liquid crystal display device does not emit light, it consumes less power. However, the conventional reflective liquid crystal display device cannot display bright paper white,
This inevitably prevents bright color display. This is a major technical issue in developing a reflective liquid crystal display device having an image quality comparable to that of the transmissive liquid crystal display device.

The reflection type liquid crystal display device has an ECB (Electr
ically controlled birefrigence method, GH (Guest
Host) system, TN (Twisted Nematic) system and the like.
When the ECB method or the TN method is used, a polarizing plate is required. Since the light transmittance of the polarizing plate is about 40%, the light utilization efficiency is deteriorated when the polarizing plate is used.

In the case of a reflection type liquid crystal display device, the brightness is evaluated by a reflectance. This reflectance is usually measured by integrating diffusely reflected light with an integrating sphere, and is represented by the ratio (%) of light reflected to light incident on the liquid crystal display device. For example, the reflectance of newspaper is about 60%, the reflectance of high quality paper is about 80%, and the reflectance of powder such as magnesium oxide or barium sulfate is 99% or more. As described above, E
When the CB method or the TN method is used, a polarizing plate is used, and therefore a reflectance of 40% or more cannot be expected. Therefore, a reflectance of 60% or more, which can be called a paper white display, cannot be obtained, which causes a problem in color display performance.

Therefore, from the viewpoint of light utilization efficiency, the guest-host system which does not require a polarizing plate is most promising. When displaying in color with the guest host system, cyan,
It is necessary to adopt a structure in which three GH cells containing magenta and yellow dyes are laminated. Generally, such a laminated structure is most preferable in order to realize color display with a wide color reproduction range in a reflective liquid crystal display device. FIG.
RGB parallel arrangement as shown in FIG. 0 (A) and FIG. 10 (B).
In the cyan, magenta, and yellow side-by-side arrangement as shown in (1), the same color cannot be displayed on the entire surface, so the color reproduction range is inevitably narrowed.

When dot matrix display is performed using the GH cell having the above-mentioned three-layer structure, it is necessary to transmit image information pixel by pixel. As a matrix driving method for each pixel, there are simple matrix driving and active matrix driving. Simple matrix drive is VT (voltage-transmittance)
Since steepness is required in the characteristics, it is not suitable for a guest-host liquid crystal having a small liquid crystal content due to the mixture of dyes. For active matrix driving, for example, the active element is a transistor T
There is an FT method.

[0009]

In the case of the TFT method,
Normally, as shown in FIG. 11, the signal line 2 connected to the TFT 1
And the scanning line 3 are required, and the signal line 2 and the scanning line 3 are non-display areas, and a certain distance is required between the signal line 2 and the scanning line 3. Further, a black matrix is required to hide these non-display areas, and this black matrix is formed so as to overlap the pixel electrode in consideration of the positional deviation with the pixel electrode. Therefore, in the TFT method, the effective display area is usually narrow, that is, the aperture ratio is small. As a result, the light utilization efficiency is lowered, the reflection brightness is lowered, and the screen becomes dark.

In the case of the TFT system, as shown in FIG. 12, when a GH cell having a three-layer structure is manufactured by stacking four glass substrates 4, the thickness of the glass substrate 4 (usually 0.3 mm or more) Because of this, the effective vision becomes narrow. Further, in the case of the structure shown in FIG. 12, there are a total of six transparent electrodes used as the pixel electrode 5 and the counter electrode 6. Therefore, the incident light must pass through the transparent electrode 12 times in total before it is reflected by the reflection plate (electrode) 7 and exits from the GH cell, and the light is attenuated during that time and the reflectance is lowered. To do. Therefore, there is a demand to reduce the number of transparent electrodes as much as possible.

The present invention has been made in view of the above points, and an object of the present invention is to provide a reflective liquid crystal display device having a large reflectance and an aperture ratio and capable of good color display.

[0012]

According to the present invention, a pair of substrates each having an active element and wiring for controlling potential information applied to a transparent electrode, and a pair of substrates sandwiched between the pair of substrates, are provided. A liquid crystal cell in which a liquid crystal layer and a transparent electrode layer are repeatedly laminated at least once in sequence and the liquid crystal layer is composed of guest-host liquid crystal containing dye molecules and liquid crystal molecules. A liquid crystal display device is provided in which the active element and the active element are electrically connected.

In the liquid crystal display device of the present invention, the liquid crystal layer is composed of a thin film containing microcapsules enclosing guest-host liquid crystals, and a plurality of units are laminated on the reflecting plate with the transparent electrode layer and the thin film as one unit. Preferably.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A liquid crystal display device according to the present invention comprises a pair of substrates each having an active element and a wiring for controlling potential information applied to a transparent electrode, and sandwiched between the pair of substrates. A liquid crystal cell in which a liquid crystal layer and a transparent electrode layer are sequentially laminated at least once on a reflection plate, wherein the liquid crystal layer is composed of guest-host liquid crystal containing dye molecules and liquid crystal molecules, and each transparent The electrode layer and the active element are electrically connected.

In this liquid crystal display device, two substrates having a liquid crystal layer and a transparent electrode layer are bonded to each other,
A guest-host liquid crystal cell is sandwiched between a pair of substrates. Therefore, the number of layer forming steps per substrate is reduced, and the yield per substrate is improved. Further, since the active element and the wiring region, which are the non-display region, do not exist in the liquid crystal cell region, the aperture ratio can be increased.

Further, in the past, the number of transparent electrodes was (pixel electrode + counter electrode) × the number of liquid crystal layers (for example, in the case of three liquid crystal layers, six transparent electrodes). The number of transparent electrodes in the cell region can be set to the number of pixel electrodes × the number of liquid crystal layers (for example, when the number of liquid crystal layers is three, the number of transparent electrodes is three), and the transmittance can be improved as compared with the conventional case.

By forming the liquid crystal layer with a thin film containing microcapsules containing a liquid crystal material, it is not necessary to use a glass substrate between the liquid crystal layers, and the effective viewing angle can be widened.

Further, according to the liquid crystal display device of the present invention,
Since the guest-host liquid crystal is used, a polarizing plate is not required, and the light utilization efficiency is high and the reflectance can be increased. Further, since the liquid crystal layer is laminated, the color reproduction range is wide and good color display can be performed.

In the liquid crystal display device of the present invention, the liquid crystal cell refers to one in which a liquid crystal layer and a transparent electrode layer are repeated at least once and sequentially laminated. In this case, the liquid crystal cell may be formed by injecting a liquid crystal material between a plurality of glass substrates having transparent electrode layers, or may be formed by alternately forming liquid crystal layers and transparent electrode layers.

When a liquid crystal cell is formed by alternately forming a liquid crystal layer and a transparent electrode layer, microcapsules enclosing a liquid crystal material are mixed with a solvent to form a paste, the paste is applied, and the solvent is volatilized to form the micro A thin film containing capsules is formed. On top of that, ITO (Injium Tin Oxid)
e), a transparent conductive material such as tin oxide is deposited by a sputtering method or a printing method, and this is patterned to form a transparent electrode layer. By repeating this operation, a liquid crystal cell having a plurality of units including the transparent electrode layer and the thin film as one unit is formed. The diameter of the microcapsules needs to be set to be equal to or smaller than the cell gap. Microcapsulation techniques that can be used include interfacial polymerization, in-situ polymerization, submerged curing coating, phase separation from aqueous solution, phase separation from organic solvent, melt dispersion cooling method, and suspension in air. There are a turbidity method, a spray drying method and the like, which can be appropriately selected depending on the application, the form and the like. Further, as the microcapsule agent (membrane material), polystyrene, styrenedivinylbenzene copolymer, polymethylmethacrylate, polyacrylonitrile,
Addition polymerization polymers such as polybutadiene, polyisoprene, and polytetrafluoroethylene; polyamides such as nylon 66, polyimides, polyurethanes, polyesters,
Polycondensation polymers such as polyetherimides; natural polymers such as gum arabic, gelatin, natural rubber and cellulose can be used. The film material of the microcapsule is
One having three-dimensionally crosslinked heat resistance is desirable. The binder required for microencapsulation is not particularly limited, but is soluble in a suitable solvent before film formation,
It is necessary to have a function of stably dispersing the microcapsules. Further, the binder polymer is preferably one which is crosslinked and insolubilized by heating after film formation. The thickness of the thin film (liquid crystal layer) is preferably 5 to 15 μm. This is because if the thickness of the thin film is less than 5 μm, sufficient color density cannot be obtained, and if the thickness of the thin film exceeds 15 μm, the applied voltage increases and the active element cannot drive.

With such a structure, it is not necessary to inject a liquid crystal material and it is not necessary to use a glass substrate. Therefore, the thickness of the liquid crystal display device itself can be reduced and the effective viewing angle can be widened.
Further, since the liquid crystal layer and the transparent electrode layer are formed into thin films, patterning of each layer is facilitated, and the through-hole portion can be formed by patterning, so that the active element formed on the substrate and each transparent electrode layer Electrical connection between them can be easily made.

In the liquid crystal display device of the present invention, it is preferable that three transparent electrode layers and three liquid crystal layers are laminated on the reflection plate, and the colors of the liquid crystal layers correspond to cyan, magenta, and yellow, respectively. With this configuration, color display can be performed. It is also preferable that four transparent electrode layers and four liquid crystal layers are laminated on the reflection plate, and the colors of the films correspond to cyan, magenta, yellow, and black, respectively. By providing the black liquid crystal layer in this manner, it is possible to obtain a black display without coloring, that is, a display of a tight black.

In the liquid crystal display device of the present invention, it is preferable that each transparent electrode layer and the active element are electrically connected by a plating layer. Further, it is preferable that a shield electrode having a constant potential is provided between the substrate and the reflection plate. By providing the shield electrode, noise due to electrical coupling between the signal line and the pixel can be prevented, and noise due to coupling between the scanning line or the active element and the pixel can also be prevented. Alternatively, a reflector may be used as an electrode so that this electrode also serves as a shield electrode. By doing so, the number of electrodes can be reduced by one and the number of manufacturing steps can be reduced.

In the liquid crystal display device of the present invention, a glass substrate or the like can be used as the substrate material. However, the substrate needs to be transparent because the reflector is arranged between the substrate and the liquid crystal cell. Therefore, a substrate made of silicon, ceramics or the like may be used. As the material of the reflector, aluminum or chromium can be used when it has conductivity, and magnesium oxide, barium sulfate, or the like can be used when it has insulation.
As the guest dye molecule, a yellow dye, a magenta dye, which is used in a guest-host type liquid crystal display device,
A dye such as a cyan pigment can be used.

As the liquid crystal of the host liquid crystal, for example, a liquid crystal compound having a positive dielectric anisotropy or a mixture of liquid crystal compounds can be used. Note that even a known liquid crystal compound having a negative dielectric anisotropy can be mixed with a liquid crystal compound having a positive dielectric anisotropy and used as a positive dielectric anisotropy as a whole. Further, even a liquid crystal compound having a negative dielectric anisotropy can be used as it is by using an appropriate element structure and driving method.

The active element is a TFT (thin film transistor) or MIM (metal-insulator-metal).
Etc., and the wiring means a signal line (data line), a scanning line (address line), or the like.

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 (A) is a schematic view showing an embodiment of the liquid crystal display device of the present invention, and FIG. 1 (B) is shown in FIG. 1 (A).
3 is a cross-sectional view of the liquid crystal display device shown in FIG. In the figure, 11b shows a glass substrate. A plurality of TFTs are provided on the glass substrate 11b.
12 are formed. A reflecting plate 13 made of aluminum is arranged on the glass substrate 11 with an insulating film interposed therebetween. This reflector 13 constitutes a pixel electrode. Further, a yellow liquid crystal layer 14a, a transparent electrode layer (pixel electrode) 15, a magenta liquid crystal layer 14b, a transparent electrode layer (pixel electrode) 15, and a cyan liquid crystal layer 14c are sequentially laminated on the reflection plate 13. The liquid crystal layers 14a to 14c are formed by printing a paste containing microcapsules enclosing guest-host liquid crystal containing dye molecules of respective colors (yellow, magenta, and cyan) and volatilizing the solvent in the paste. The transparent electrode layer 15 is formed by sputtering a transparent conductive material and patterning it by photolithography and etching. The liquid crystal layers 14a to 14c may be stacked in any order.

Further, TF is formed on the cyan liquid crystal layer 14c.
T12 is formed, and a glass substrate 11a having a transparent counter electrode 16 is arranged. In addition, each TFT1
2 and the reflector 13 or the transparent electrode layer 15 are electrically connected. In this way, the liquid crystal layers 14a to 14b are provided between the glass substrates 11a and 11b on which the TFT 12 is formed.
A liquid crystal display device in which c and the transparent electrode layer 15 are sandwiched is configured.

In this liquid crystal display device, a TFT 12 is formed on a glass substrate 11b, a reflecting plate 13 is formed on the TFT 12 via an insulating film, and a yellow liquid crystal layer 14a is formed on the reflecting plate 13.
A transparent substrate (pixel electrode) 15 is sequentially formed to produce a first substrate, then a TFT 12 is formed on a glass substrate 11a, and a common electrode (pixel electrode) 1 is formed on the TFT 12 via an insulating film.
6 is formed, and a cyan liquid crystal layer 14c and a transparent electrode layer (pixel electrode) 15 are sequentially formed thereon to form a second substrate. Finally, the first substrate and the second substrate are formed as transparent electrode layers. 15
It can be obtained by allowing them to face each other and bonding them via the magenta liquid crystal layer 14b. As a method for bonding via the liquid crystal layer, a liquid crystal microcapsule film is prepared in advance, and two substrates are bonded using this, or after bonding the two substrates via spacers in advance. Examples thereof include a method of injecting a liquid crystal material. As described above, the first substrate and the second substrate are attached to each other with the liquid crystal layer interposed therebetween, whereby the process can be simplified and the yield can be improved.

In the liquid crystal display device having the above structure, since the liquid crystal layers 14a to 14c and the transparent electrode layer 15 do not have active elements and wirings which are non-display areas, the aperture ratio is wide and the transparent electrode layer is formed. Since it is formed of a thin film and no glass substrate is used, the light utilization efficiency is high.

When performing color display with this liquid crystal display device, the voltage applied to the four electrodes sandwiching each liquid crystal layer is predetermined by an arithmetic circuit. For example,
To display "white", a voltage is applied as shown in FIG. In the figure, G means GND, which is a reference potential. V is a potential with respect to GND, and is the above-mentioned V
In the −T characteristic, this is a potential at which T can be saturated to a high level to some extent. Note that the voltage application is shown in two ways because it is necessary to apply an AC waveform to the liquid crystal layer. In the case of the guest-host liquid crystal, when displaying "white", it is necessary to stand the liquid crystal molecules and the dye molecules in the direction perpendicular to the electrode surface as much as possible for the sake of transmitting light, and therefore, as shown in FIG. So that the voltage is applied to.

On the other hand, when "black" is displayed,
In order to absorb light, it is necessary to orient the liquid crystal molecules and dye molecules in all directions as much as possible. In the liquid crystal display device of the present invention, the liquid crystal molecules are aligned such that the liquid crystal molecules are dispersed in all directions in the absence of an electric field. Therefore,
To display "black", a voltage is applied as shown in FIG.

When the primary color "red" is displayed, as shown in FIG. 2B, the magenta liquid crystal layer 14b and the yellow liquid crystal layer 14a absorb light, and the cyan liquid crystal layer 1
4c transmits light. When displaying "green", as shown in FIG. 2C, the cyan liquid crystal layer 14c and the yellow liquid crystal layer 14a absorb light, and the magenta liquid crystal layer 14b transmits light. To display "blue",
As shown in (D), the cyan liquid crystal layer 14c and the magenta liquid crystal layer 14b absorb light, and the yellow liquid crystal layer 14a transmits light.

When displaying the complementary color "cyan", as shown in FIG. 2F, the cyan liquid crystal layer 14c absorbs the light and the magenta liquid crystal layer 14b and the yellow liquid crystal layer 14a transmit the light. Let When displaying "magenta", as shown in FIG. 2G, the magenta liquid crystal layer 14b is displayed.
To absorb light, and the cyan liquid crystal layer 14c and the yellow liquid crystal layer 14a transmit light. When displaying "yellow", as shown in FIG. 2H, the yellow liquid crystal layer 14a is displayed.
To absorb light, and the cyan liquid crystal layer 14c and the magenta liquid crystal layer 14b transmit light.

In this way, the basic eight color display can be performed. In this case, the potentials applied to the electrodes may be V and G. On the other hand, when performing halftone display, so-called frame rate control (FRC) is used,
A dither method using a plurality of pixels, that is, an area gradation method may be used. In addition, the gradation may be displayed by controlling the transmittance with a voltage. That is, when a voltage is applied as shown in FIG. 3A, the cyan liquid crystal layer 14c is in a transmissive state, and the magenta liquid crystal layer 14b and the yellow liquid crystal layer 14a are in a semi-transmissive state. In such a case, it is possible to display a pink color. Further, when displaying light cyan, a voltage is applied as shown in FIG. In the case of such a halftone display, the range of the potential applied to each electrode is -V to G
It is necessary to set to + V.

Next, the specific structure of the liquid crystal display device of the present invention will be described. FIG. 4 is a perspective exploded view showing a region corresponding to one pixel of the liquid crystal display device of the present invention. One scanning line 18 is formed on the glass substrates 11a and 11b, and two scanning lines 18 are formed at intervals on the scanning line 18 of the glass substrate 11b.
One TFT 12 is formed, and one TFT 12 is formed on the scanning line 18 of the glass substrate 11a. this is,
This is because one pixel has three liquid crystal capacitors of cyan, magenta and yellow. Further, the signal line 1 is arranged in a direction orthogonal to the scanning line 18 so as to be in contact with each TFT 12.
7 are formed. A copper-plated pillar 19 is formed in each TFT 12 in the thickness direction.
9, the reflector 13 or the transparent electrode layer 15 and the TFT 12
And are electrically connected. In this case, each signal line 17
The information sent to is sent to the reflector (pixel electrode) 13 and the transparent electrode (pixel electrode) 15 via the TFT 12 and the copper-plated pillars 19.

Regarding the connection between the reflection plate 13 and the TFT, the material of the reflection plate 13 may be directly connected without using the copper plating pillar 19. This means that the lowermost (or uppermost) reflector plate 13 or the transparent electrode layer 16 is different from the other transparent electrode layer 15.
This is because the connection layer can be formed at the time of forming this layer because it is relatively closer to the TFT 12. With respect to the other transparent electrode layers 15, the connection layer is not sufficiently formed in the through holes and step disconnection occurs. Furthermore, to simplify the process,
The insulating film below the reflection plate 13 may be omitted, and the reflection plate 13 may be directly formed on the TFT 12 for connection.

In FIG. 4, the storage capacitance (Cs) is not shown. In reality, Cs is connected in parallel with the liquid crystal capacitance of one pixel. That is, the common wiring for Cs is the scanning line 1
8 is arranged in parallel with each other, and Cs is formed between the common wiring for Cs, the signal line 18, and “a certain metal electrode” in each pixel unit. This "certain metal electrode" is connected to the pixel electrode via the through hole. Since there are three liquid crystal capacitors for one pixel, Cs is also 3 for one pixel.
It is necessary to provide one.

Next, a method of manufacturing the TFT array substrate shown in FIG. 4 will be described. First, a thickness of 10 on a glass substrate
A silicon oxide film or a silicon nitride film of 00 to 2000 angstrom is formed, and molybdenum, tantalum, tungsten, titanium, aluminum, chromium,
A thin film made of a metal such as copper or an alloy thereof, or a laminated film thereof is formed. These thin films are patterned by so-called photolithography, that is, a photo engraving process (PEP) to form TFT gates and gate lines.

Then, a thickness of 2000 to 40 is again formed on this.
A silicon oxide film or a silicon nitride film of 00 angstrom is formed, and this is used as a gate insulating film. In this case, an i / a-Si: H layer having a thickness of 100 to 4000 angstrom is further formed thereon. It is also possible to form a silicon oxide film or a silicon nitride film having a thickness of 1000 to 2000 angstrom as an etching stopper layer on this and pattern it by PEP.

After that, n-thickness of 100 to 1000 angstrom is used for the source / drain contact of the TFT.
⁺ / A-Si: H layer is formed. Here, the i / a-Si: H layer serving as the channel of the TFT and the n ⁺ / a-Si:
The H layer and PEP are patterned.

Then, as the source / drain electrodes and the signal lines, a thin film made of a metal or alloy such as aluminum, titanium, molybdenum, tantalum, tungsten, chromium, or a laminated film thereof is formed. This is PE
P is patterned into a desired pattern. Then, TF
A TFT is manufactured by removing the n ⁺ / a-Si: H layer between the source and drain of T.

Then, as shown in FIG.
On T12, a silicon oxide film, a silicon nitride film, a polyimide film, a polycarbonate film, an acrylic resin film, a fluorine resin film, a polyester resin film, an epoxy resin film,
The insulating film 20 such as a silicone resin film has a thickness of 0.1 to 3 μm.
m. Then, as shown in FIG. 5B, a through hole 21 for making contact with the source or drain of the TFT 12 is formed at a desired portion of the insulating film 20.
Are formed by PEP.

Thereafter, as shown in FIG. 5C, a copper plating pillar 19 is grown in the through hole 21 by a plating process. Then, as shown in FIG.
The surface is flattened by CMP (Chemical Mechanical Polishing). Further, as shown in FIG.
A metal such as aluminum, chrome, molybdenum, or tungsten is deposited thereon to a thickness of 1000 to 4000 angstroms so as to come into contact with the copper-plated pillars 19.
The reflector (pixel electrode) 13 is formed. In order to bring the reflection characteristics of the reflection electrode close to that of perfect diffusion, it is preferable to provide the surface of the reflection plate 13 with unevenness. Examples of the method of providing the unevenness include a method of making the unevenness with PEP, a pressing method such as embossing, a method of roughening the surface with a chemical, a method of roughening the surface by rubbing with a file or the like.
Alternatively, powder such as magnesium oxide or barium sulfide having a perfect diffusion characteristic may be deposited on the reflection plate 13.

Next, as shown in FIG. 5F, a paste containing microcapsules containing guest-host liquid crystal containing dye molecules is applied thereon. Then, the solvent or the like in this paste is volatilized to cure the microcapsules to form a yellow liquid crystal layer 14a having a thickness of 5 to 15 μm. Then, a through hole is formed in the yellow liquid crystal layer 14a by PEP, and a copper-plated pillar 19 connected to the source or drain is grown.

Then, as shown in FIG. 5G, CMP is performed.
Then, the surface is flattened, and a transparent electrode layer (pixel electrode) 15 having a thickness of 100 to 1000 Å is formed and patterned. In this way, the first substrate is formed.

Then, as shown in FIGS. 6A to 6G, a second substrate is formed. That is, an insulating film is formed on the glass substrate 11a on which the TFT 12 is formed, a through hole is formed in the insulating film, and a copper plating pillar 19 is formed in the insulating film to flatten the common electrode 16 (transparent counter electrode). Electrodes) are formed and patterned so that the copper-plated pillars 19 are exposed. Further, a cyan liquid crystal layer 14c is formed thereon, a through hole is formed in the cyan liquid crystal layer 14c to grow a copper-plated pillar 19, and a transparent electrode layer 15 is formed thereon.
To form

After that, the first substrate and the second substrate are bonded together with the magenta liquid crystal layer 14b interposed therebetween, as shown in FIG.
A liquid crystal display device of the present invention as shown in FIG. In the liquid crystal display device manufactured in this manner, the glass substrate interposed between the liquid crystal layers can be omitted, and the number of transparent electrodes can be reduced. As a result, it is possible to prevent the effective visual field and the reflectance from decreasing.

Further, in this liquid crystal display device, 1
Rather than laminating the liquid crystal layer on one glass substrate, the liquid crystal layer is formed on each of the two glass substrates, and the two are bonded together to realize a multi-layer structure. Can be reduced (the number of steps is reduced), and the yield per glass substrate can be improved. This manufacturing method is more effective as the number of liquid crystal layers increases.

In this embodiment, cyan, magenta,
Although the three-layer structure of yellow has been described, a four-layer structure in which a black opaque black liquid crystal layer is added thereto may be used. With this configuration, a brighter black display can be achieved. (Embodiment 2) FIG. 8 is a schematic view showing another embodiment of the liquid crystal display device of the present invention. In this liquid crystal display device, a shield electrode 22 having a constant potential is provided below the reflection plate (pixel electrode) 13 (on the glass substrate 11 side) to reduce capacitive coupling between the pixel electrode 13 and the signal line / gate line / TFT. It has a structured structure. The Cs capacitor 23 may be provided between the shield electrode 22 and the pixel electrodes 13 and 15. In this case, the common electrode 16 serves as a shield electrode.

By providing this shield electrode 22, various electric circuits can be provided below it. The presence of the shield electrode 22 can prevent capacitive coupling between the pixel electrode and the electric circuit. (Embodiment 3) FIG. 9 is a schematic view showing another embodiment of the liquid crystal display device of the present invention. This liquid crystal display device has a structure in which the reflection plate (pixel electrode) 13 is made of a shield electrode 22 having a constant potential. This liquid crystal display device is also the second embodiment.
Similar to the liquid crystal display device described in (1), it is possible to reduce the capacitive coupling between the pixel electrode and the signal line / gate line / TFT. The Cs capacitor 23 may be provided between the shield electrode 22 and the pixel electrode 15. In this case as well, the common electrode 16 functions as a shield electrode.

By providing this shield electrode 22, various electric circuits can be provided below it. The presence of the shield electrode 22 can prevent capacitive coupling between the pixel electrode and the electric circuit. Example 4 A liquid crystal display device having a structure in which the reflection plate (pixel electrode) 13 or the shield electrode 22 was formed of a transparent conductive material to form a transparent electrode, and a diffusion plate was arranged outside the glass substrate 11 was produced. With such a structure,
The manufacturing process can be simplified. For example, since the diffusion plate is attached externally, it is not necessary to make the surface of the reflective electrode uneven in order to improve the diffusivity. Further, by arranging a backlight instead of the diffusion plate, the guest-host liquid crystal cell can be used as both a transmission and reflection type. When this liquid crystal display device is used as a transmissive liquid crystal display device, the light utilization efficiency is high (about 3 times) as compared with a transmissive liquid crystal display device using a conventional color filter.

[0053]

As described above, the liquid crystal display device of the present invention is sandwiched between a pair of substrates on which active elements and wirings for controlling potential information applied to the transparent electrodes are formed, and between the pair of substrates. And a liquid crystal cell in which a liquid crystal layer and a transparent electrode layer are sequentially laminated at least once on a reflection plate, and the liquid crystal layer is composed of guest-host liquid crystal containing dye molecules and liquid crystal molecules. Since each transparent electrode layer and the active element are electrically connected to each other, the number of transparent electrode layers can be reduced, thereby preventing a decrease in reflected brightness and brightening the screen. .

Further, the liquid crystal display device of the present invention can obtain a wide field of view, has a large aperture ratio, and can perform good color display. Further, by laminating the pair of substrates with the liquid crystal layer in between, the number of steps for laminating the liquid crystal layer per substrate can be reduced, and the yield per substrate can be improved.

[Brief description of drawings]

1A is a schematic view showing an embodiment of a liquid crystal display device of the present invention, and FIG. 1B is a sectional view of the liquid crystal display device shown in FIG.

2A to 2H are potential configuration diagrams of the liquid crystal display device of the present invention.

3A and 3B are potential configuration diagrams of the liquid crystal display device of the present invention.

FIG. 4 is a perspective exploded view showing a region corresponding to one pixel of the liquid crystal display device of the present invention.

5A to 5G are cross-sectional views showing the first half of the manufacturing process of the liquid crystal display device shown in FIG.

6A to 6G are cross-sectional views showing the latter half of the manufacturing process of the liquid crystal display device shown in FIG.

FIG. 7 is a cross-sectional view showing a region corresponding to one pixel of the liquid crystal display device of the present invention.

FIG. 8 is a schematic view showing another embodiment of the liquid crystal display device of the present invention.

FIG. 9 is a schematic view showing another embodiment of the liquid crystal display device of the present invention.

10A and 10B are schematic views of a conventional parallel-arranged liquid crystal display device.

FIG. 11 is a circuit diagram of a display area of a conventional liquid crystal display device.

FIG. 12 is a schematic view of a conventional guest-host liquid crystal display device having a three-layer structure.

[Explanation of reference numerals] 11a, 11b ... Glass substrate, 12 ... TFT, 13 ... Reflector (pixel electrode), 14a ... Yellow liquid crystal layer, 14b ...
Magenta liquid crystal layer, 14c ... Cyan liquid crystal layer, 15 ... Transparent electrode layer (pixel electrode), 16 ... Counter electrode, 17 ... Signal line, 1
8 ... Scan line, 19 ... Copper plated pillar, 20 ... Insulating film, 21 ...
Through hole, 22 ... Shield electrode, 23 ... Cs capacitance,
24 ... Dummy conductive pattern, 25 ... Conductive layer.

Claims (8)

[Claims] 1. A pair of substrates each having an active element and a wiring for controlling potential information applied to a transparent electrode, and a pair of substrates sandwiched between the pair of substrates, and a liquid crystal layer and a transparent electrode layer on a reflection plate. A liquid crystal cell formed by repeating at least once and sequentially laminating, wherein the liquid crystal layer is composed of a guest-host liquid crystal containing dye molecules and liquid crystal molecules, and each of the transparent electrode layers and the active element are A liquid crystal display device characterized by being electrically connected. 2. The liquid crystal layer is composed of a thin film containing microcapsules containing the guest-host liquid crystal, and a plurality of units are laminated on the reflection plate with the transparent electrode layer and the thin film as one unit. The liquid crystal display device according to claim 1. 3. The liquid crystal display according to claim 1, wherein three layers of the transparent electrode layer and the liquid crystal layer are laminated on the reflection plate, and the colors of the liquid crystal layers correspond to cyan, magenta, and yellow, respectively. apparatus. 4. The liquid crystal according to claim 1, wherein four layers each of the transparent electrode layer and the liquid crystal layer are laminated on the reflection plate, and the colors of the films correspond to cyan, magenta, yellow, and black, respectively. Display device. 5. The liquid crystal display device according to claim 1, wherein each transparent electrode layer and the active element are electrically connected by a plating layer. 6. The liquid crystal display device according to claim 1, wherein a shield electrode having a constant potential is provided between the substrate and the reflection plate. 7. The liquid crystal display device according to claim 1, wherein the reflector is an electrode. 8. The liquid crystal display device according to claim 7, wherein the electrode also serves as a shield electrode having a constant potential.