JP3427729B2 - Liquid crystal display device, substrate for liquid crystal display device, and method of manufacturing the same - Google Patents

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 for displaying images and information, and more particularly to a liquid crystal display device using a flexible substrate.

[0002]

2. Description of the Related Art Liquid crystal display devices are thin, lightweight and can be driven at a low voltage.
It has come to be widely used for displaying A-devices, portable devices such as electronic notebooks, and various video devices.

Above all, a liquid crystal display device using a plastic plate or film as a substrate can be made thinner and lighter than a device using a glass substrate, and is considered to be a promising display for portable devices. . In addition, since these boards are flexible, it is not necessary to increase the rigidity of the housing in order to prevent the boards from bending in various electronic devices, or there is a problem in design requirements or device shape. There is also an advantage that curved surfaces can be displayed.

For example, in Japanese Patent Laid-Open No. 6-214220, in a liquid crystal display device for curved display in which a MIM switching element is formed on a flexible substrate, the curved direction of the substrate is defined as the short side direction of the rectangular switching element. The direction of curvature of the substrate is made to coincide with the direction of extension of the electrode having the wider line width of the two wiring electrodes in the vertical and horizontal directions, or the side opposite to the center of curvature of the flexible substrate on which the switching element is formed is curved. There is disclosed a technique for preventing the peeling of the wiring electrode and the element by arranging them at the position.

[0005]

However, in the liquid crystal display device as described above, the direction in which the substrate or the liquid crystal panel is bent is specified, so that the use is limited. That is, if the direction in which the board bends is not constant due to usage conditions such as portable equipment, peeling of wiring electrodes and elements is not prevented, and the wiring direction and element configuration are changed for each design of electronic equipment that uses a liquid crystal display device. Since it is necessary, there is a problem that the design work is complicated and the cost of the liquid crystal display device is increased.

Further, when the substrate is bent in the direction in which the wiring or the element is easily peeled off during the manufacture of the liquid crystal display device,
There is also a problem that manufacturing costs increase due to defects such as disconnection and element defects, and that equipment for specifying the substrate bending direction at the time of manufacturing is newly required to prevent such defects.

Further, in order to display a higher quality image,
When a thin film transistor (TFT) having a switching characteristic superior to that of a two-terminal element such as an MIM element is used, wiring crossover can be performed on the substrate. Therefore, when the substrate is bent or curved display is performed, there is a problem that a wiring short circuit occurs at the crossover portion.

In view of the above problems, the present invention prevents damage and short circuit of electrodes due to the bending of the substrate of a liquid crystal display device using a flexible substrate, and is inexpensive, has a long life, and has a wide range of applications. The main purpose is to provide a device.

[0009]

In order to achieve the above object, a first liquid crystal display device according to the present invention has two electrodes for applying a voltage to a liquid crystal layer formed on a flexible substrate. At least one surface of the layer has anisotropic conductivity that is conductive in the thickness direction but not in the in-plane direction.
An electrode protective layer having anisotropic conductivity is formed.

In the second liquid crystal display device according to the present invention, a protective layer is formed so as to cover the bus wiring formed on the flexible substrate and the vicinity thereof, and the protective layer is formed in the thickness direction.
Shows conductivity, but not in-plane anisotropic conductivity
It is characterized by having .

[0011]

A substrate for a liquid crystal display device according to the present invention includes an electrode having a predetermined shape and the electrode formed on the electrode ,
It is characterized by comprising a flexible base material, having a protective layer exhibiting anisotropic conductivity , which exhibits conductivity in the thickness direction but not in the in-plane direction .

The above method for manufacturing a substrate for a liquid crystal display device comprises the steps of forming electrodes of a predetermined shape on a flexible substrate, applying a resin in which conductive particles are dispersed in a base material, And a step of hardening while compressing in the thickness direction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The first invention of the present invention is, in a liquid crystal display device using a flexible substrate, at least one of electrode layers for applying a voltage to a liquid crystal layer formed on two substrates. Is formed with a protective layer exhibiting anisotropic conductivity. As a result, the electrodes are not damaged even when the substrate is bent or curved display is performed during the production or use of the liquid crystal display device. Therefore, the product yield is improved, the product life is extended, and the flexibility of the shape and design of the electronic device using the liquid crystal display device is increased. Further, since it has anisotropic conductivity, there is almost no voltage loss in the protective layer. Therefore, even if the protective layer is formed, the drive voltage of the liquid crystal does not increase, the cost of the drive IC increases due to the high breakdown voltage, and the power consumption increases as the power supply voltage increases. Absent.

According to a second aspect of the present invention, in a liquid crystal display device using a flexible substrate, a pixel electrode, a switching element, and a bus wiring are formed on at least one substrate, and the bus wiring and the bus wiring are provided. A protective layer is formed so as to cover the vicinity. As a result, the bus wiring will not be damaged even when the substrate is bent or a curved surface is displayed when the liquid crystal display device is manufactured or used. Therefore, the product yield is improved, the product life is extended, and the flexibility of the shape and design of the electronic device using the liquid crystal display device is increased. Further, since the protective layer is not formed on the electrodes for applying a voltage to the liquid crystal layer, there is no loss of applied voltage in the liquid crystal layer. Therefore, the cost of the drive IC does not increase due to the high breakdown voltage, and the power consumption does not increase as the power supply voltage increases.

According to a third aspect of the present invention, in a liquid crystal display device using a flexible substrate, a scan electrode, a pixel electrode and a thin film transistor element are formed on the first flexible substrate, and a second flexible substrate is provided. A signal electrode is formed on the flexible substrate. This eliminates wiring crossover on the substrate while using thin film transistors as switching elements.
Therefore, it is a display with high display quality using a thin film transistor, and prevents the occurrence of a short circuit between the scanning line and the signal line when the substrate is bent during manufacture or use of the liquid crystal display device or when curved display is performed. Therefore, the product yield is improved, the product life is extended, and the flexibility of the shape and design of the electronic device using the liquid crystal display device is increased.

According to a fourth aspect of the present invention, in the liquid crystal display device according to the third aspect, the pixel electrode is divided into two sub-pixel electrodes, each of which is connected to a source terminal and a drain terminal of a thin film transistor. As a result, a symmetrical element structure can be obtained, and display with less flicker can be performed.

According to a fifth aspect of the present invention, in the liquid crystal display device according to the third aspect, one of the source terminal and the gate terminal of the thin film transistor is connected to the pixel electrode and the other is connected to the common wiring. is there. Accordingly, when the thin film transistor is in the ON state, electrical continuity is established between the pixel electrode and the common wiring, and the pixel electrode does not remain in the floating state for a long period of time. Therefore, the display is not disturbed by the influence of static electricity or the like, and stable display can be performed.

In a sixth aspect of the present invention, in the liquid crystal display device according to the third aspect, one of the source terminal and the gate terminal of the thin film transistor is connected to the pixel electrode, and the other is connected to the scanning electrode other than this stage. It was done. Thereby, since the common wiring can be omitted, it is possible to obtain a bright liquid crystal display device with a higher aperture ratio as compared with the fifth invention.

According to a seventh aspect of the present invention, in the liquid crystal display device according to the third to sixth aspects, a protective layer having anisotropic conductivity is formed on the surface of at least one of the pixel electrode and the signal electrode. It is a thing. As a result, it is possible to prevent the signal electrodes and the scanning electrodes from being damaged when the substrate is bent or curved display is performed without increasing the voltage applied to the liquid crystal layer.

An eighth invention of the present invention is the liquid crystal display device according to the third to sixth inventions, wherein a protective layer is formed so as to cover the scanning electrodes and the vicinity thereof. As a result, it is possible to prevent the signal electrodes and the scanning electrodes from being damaged when the substrate is bent or curved display is performed without increasing the voltage applied to the liquid crystal layer.

According to a ninth aspect of the present invention, an electrode having a predetermined shape and a protective layer having anisotropic conductivity formed on the electrode are formed on a flexible substrate. Thus, the electrodes are not damaged even when the substrate is bent during manufacturing or use of the liquid crystal display device, and the yield of the liquid crystal display device using the flexible substrate is improved. Further, since there is no voltage loss in the protective layer, the drive voltage of the liquid crystal display device does not rise, and
It can be incorporated into an electronic device that requires curved display or flexibility.

A tenth aspect of the present invention is the step of forming an electrode having a predetermined shape on a flexible substrate, the step of applying a resin in which conductive particles are dispersed in a base material, and the thickness of the resin. And curing while compressing in the direction. As a result, a flexible substrate having an anisotropic conductive resin on the electrodes,
It can be easily manufactured by a simple process.

FIG. 1 shows an embodiment of the present invention.
From now on, description will be made with reference to FIG.

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal display device according to Embodiment 1 of the present invention. In FIG. 1, 101 is a first substrate, 102 is a second substrate,
A first electrode 103 and a second electrode 103 are provided on each substrate.
Electrode 104 is formed, and the electrodes 103 and 1
04 is used to apply a voltage to the liquid crystal layer 107. This first
The electrode 103 and the second electrode 104 are stripe electrodes orthogonal to each other, the first electrode 103 extends in the depth direction of the drawing, and the second electrode 104 extends in the left-right direction of the drawing. It constitutes a matrix type liquid crystal display device. The liquid crystal display modes are TN,
Either a polarization display type such as STN or IPS, a scattering display type such as a polymer dispersion type, or an absorption display type such as a guest host type can be used.

Numerals 105 and 106 are protective layers. The protective layer 105 is formed on the electrode 103, and the protective layer 106 is formed on the electrode 104. Protective layers 105 and 10
6 has anisotropic conductivity. Anisotropic conductivity is a property of having conductivity only in a specific direction.
In the configuration shown in, there is conductivity in the thickness direction of the protective layer,
There is no conductivity in the in-plane direction.

Further, reference numeral 108 denotes a sealant, which has a function of covering the periphery of the liquid crystal layer and adhering the upper and lower substrates. Further, 109 and 110 are polarizing plates for performing polarized display. In addition, depending on the display mode, only one polarizing plate may be arranged or the polarizing plate may not be arranged at all.

In the liquid crystal display device of the present invention, the protective layer 105.
The features of the electrodes 106 and 106 are that the electrodes are not easily damaged even when the substrate is bent during manufacturing or use.

Therefore, this will be described below with reference to FIGS. 2 to 5. In these figures, for simplicity, only the second substrate side is shown. Further, the same numbers are given to the same components as in FIG.

First, the case where the protective layer 106 is not formed will be described. FIG. 2 is a cross-sectional view showing the substrate 102 on which the electrode 104 is formed, and FIG. 2A shows a state without any bending. When forces 111 to 113 as shown in FIG. 2B are applied to the substrate from the outside, the substrate is bent. When the forces 111 to 113 are further applied, as shown in FIG.
As shown in (c), the electrode 104 is cracked or peeled due to the stress generated by the bending of the substrate.

On the other hand, when the protective layer 106 is formed, as shown in FIG. 3, even if the substrate is bent by applying external forces 111 to 113, the electrode 104 is less likely to crack or peel.

FIG. 4 and FIG. 5 schematically show the stress applied to the electrodes at the portions where cracks and peeling occur, with and without the protective layer, and compare the two.
When there is no protective layer, as shown in FIG.
Are stresses 114 and 115 that pull the surface to the left and right.
And a stress 116 that pushes the electrode layer upward. It is considered that these stresses cause cracks and peeling.

On the other hand, when the protective layer 106 is provided as shown in FIG. 5, a stress 117 that pushes the protective layer downward is generated at the interface between the electrode 104 and the protective layer 106. Therefore, the upward stress 116 is canceled or weakened. Moreover, the stress that pulls the electrode 104 to the left and right is also protected by the protective layer 1.
Alleviated by 06. Therefore, the stress on the electrode is weakened, and the occurrence of cracks and peeling is prevented.

According to experiments, it was necessary for the protective layer to have a thickness of 1 μm or more, and more preferably 5 μm or more, in order to exert the above-described effect of preventing electrode damage. Meanwhile, in the liquid crystal display device of FIG.
Increasing the thickness of 06 causes a voltage loss here. Normally, the thickness of the liquid crystal layer is about a few microns,
Of the voltage applied between the first electrode 103 and the second electrode 104, tens of percent is loss in the protective layer. Therefore, in the case where sufficient voltage is not applied to the liquid crystal layer and contrast and brightness are insufficient, or when a higher voltage is applied from the outside to prevent deterioration of display characteristics, a drive IC or a drive circuit is used. May increase the cost and power consumption.

In this embodiment, the effect of the anisotropic conductivity of the protective layer is as follows. In FIG. 1, the protective layers 105 and 106 show conductivity in the thickness direction. Therefore, the voltage applied between the first electrode 103 and the second electrode 104 is applied to the liquid crystal layer with almost no loss. On the other hand, since there is no conductivity in the in-plane direction, a signal is not leaked between adjacent electrodes and display is not damaged.

As the protective layer having anisotropic conductivity, for example, one having the following structure can be used. FIG. 6 is a sectional view schematically showing the effect of the protective layer 105 on the upper substrate. Conductive particles 12 are present in the protective layer 105.
1 are dispersed, and by contacting them in the vertical direction, conductivity in the vertical direction is obtained. There is no such conduction because the particles are laterally separated.

The liquid crystal display device of this embodiment can be manufactured, for example, as follows.

First, a transparent electrode made of ITO (an oxide of indium and tin) is formed on a flexible substrate made of polycarbonate or polyether sulfone and patterned. Next, a thermosetting base material (for example, thermosetting acrylic resin)
A dispersion of transparent conductor particles is applied.
When this is heat-cured while being compressed in the thickness direction with a roller or the like, the distance between the conductive particles in the thickness direction is reduced and conductivity in the thickness direction occurs. As a result, a protective layer having anisotropic conductivity is formed.

If there is a difference between the refractive index of the transparent conductor particles and the refractive index of the substrate, light reflection or scattering occurs at this portion, which is not desirable. If the refractive index difference between the two is set to 0.5 or less, and more preferably 0.2 or less, the above-mentioned problems are practically unproblematic.

Although the thermosetting acrylic has been described as an example of the base material, a UV curable resin may be used in place of it, and UV light may be used instead of heat curing.

As a result, the substrate shown in FIG. 6 can be obtained. As shown in FIG. 6, assuming that the thickness of the protective layer is t and the space width between the adjacent electrodes is d, if t is larger than d, a short circuit between the adjacent electrodes is likely to occur.
Is less than twice the d, and more preferably t is less than or equal to d.

On the protective layer, an alignment film for aligning the liquid crystal is formed. After that, spacers are scattered and the upper and lower substrates are bonded together to form an empty panel, as in a normal liquid crystal panel. Liquid crystal is injected and sealed in an empty liquid crystal panel, a polarizing plate is attached to form a liquid crystal panel, and a drive circuit and the like are attached to manufacture a liquid crystal display device.

In the liquid crystal display device of the present embodiment, even if the substrate is bent during use, the disconnection failure of the electrodes is unlikely to occur, and it is suitable for incorporation in various portable devices. Further, since it can be incorporated in various devices in a curved state, there is an advantage that the degree of freedom in designing various devices is improved. Further, due to the effect of the protective layer on the electrodes, there is also an advantage that the electrodes are not damaged and the electrodes are not damaged during the rubbing process of the liquid crystal panel manufacturing process and various kinds of handling.

The protective layer 106 may be made of a material having the same elastic constant as that of the substrate 102, but better results can be obtained if the protective layer is made of a material slightly harder than the substrate. Since the thickness of the protective layer is thinner than that of the substrate, the stress exerted on the electrode layer from the protective layer side is weakened, but if the protective layer is made of a solid material, the stress balance is improved.

If the substrate and the protective layer have the same coefficient of thermal expansion, the expansion and contraction occurring in the thermal process in the liquid crystal panel manufacturing process is the same on both sides of the electrode. As a result, the electrodes are not damaged and the manufacturing yield of the liquid crystal display device is significantly improved.

(Second Embodiment) FIG. 7 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device of the present embodiment is a reflection type liquid crystal display device in which the electrode 134 on the side of the back substrate 132 is a reflective electrode using a metal such as aluminum or silver, and the reflective electrode is provided on the inner surface of the liquid crystal panel. .

In FIG. 7, 131 and 132 are substrates,
Reference numeral 133 is a transparent electrode, 137 is a liquid crystal layer, and 138 is a sealant, which have the same functions as those described in the first embodiment. In the present embodiment, since 134 is the reflective electrode, only the polarizing plate 139 on the front side is arranged as necessary depending on the liquid crystal display mode.

Reference numerals 135 and 136 are protective layers exhibiting anisotropic conductivity. The function of these protective layers is to prevent damage to the electrodes when the substrate is bent or curved, without loss of applied voltage, as in the first embodiment.

Further, in this embodiment, the electrode 13
Since 4 is composed of a reflective electrode, the anisotropic conductor in the protective layer 136 on the back substrate side may be composed of a reflective material such as metal. In this way, the protective layer has a scattering and reflection property by well dispersing this reflective substance,
The viewing angle of the liquid crystal display device can be further widened.

Since a material having anisotropic conductivity higher than that of the transparent conductor can be used, the protective layer can be made thicker than in the first embodiment to enhance the effect of electrode protection.

In the above-described first and second embodiments, the description has been made assuming that the stripe electrodes are arranged orthogonally to each other to perform the dot matrix display. However, this is a segment display in which a liquid crystal display device combines electrodes of a predetermined shape. The invention described in the first and second embodiments can be applied as it is.

(Third Embodiment) FIG. 8 shows a sectional view of a liquid crystal display device according to a third embodiment of the present invention. In this embodiment, a protective film having anisotropic conductivity is added to an active matrix type liquid crystal display device using a two-terminal element such as a MIM type diode as a switching element.

In FIG. 8, 151 and 152 are flexible substrates. An MIM diode 156 serving as a switching element, a bus wiring 154 connected to the MIM diode 156, and a pixel electrode 155 are formed on the substrate 152.

On the other hand, a stripe electrode 153 extending in a direction substantially orthogonal to the bus line is formed on the substrate 151 and faces the pixel electrode 155. A liquid crystal layer 157 is provided between both substrates, and a voltage between the stripe electrode and the pixel electrode is applied to this liquid crystal layer.

Although not shown in FIG. 8, polarizing plates are formed on the outer sides of both substrates as needed, and a sealing material is provided at the outer edges of the substrates to surround the liquid crystal layer. Covering.

The liquid crystal display device of this embodiment displays by utilizing the non-linear characteristic of the MIM diode. That is, when a signal voltage is applied to the stripe electrode 153 while applying a scanning signal to the bus line 154, the voltage across the MIM diode 156 exceeds the threshold value of the diode and the diode becomes conductive, so that the pixel electrode 155 is charged. Done. In the line where the bus wiring is in the non-scan state, M
The voltage across the IM diode is below its threshold,
The electric charge of the pixel electrode 156 is retained. Display can be performed on the same principle by applying a scanning voltage to the stripe electrode and a signal voltage to the bus bar.

In the liquid crystal display device of this embodiment,
Protective layers 158 and 159 exhibiting anisotropic conductivity are formed on the surface of each substrate. As described in Embodiment 1 above, this protective layer relieves stress applied to the stripe electrodes, bus lines, pixel electrodes, and switching elements due to the bending and bending of the substrate. Therefore, these electrodes and elements are less susceptible to damage such as cracks and peeling, the occurrence of disconnection is suppressed, the yield of the liquid crystal display device is improved, and the life of the liquid crystal display device is extended. In addition, a combination with a flexible housing and curved surface display are possible, and the application is expanded. Further, due to the effect of the protective layer on the electrodes, there is also an advantage that the electrodes are not damaged and the electrodes are not damaged during the rubbing process of the liquid crystal panel manufacturing process and various kinds of handling.

Further, in the liquid crystal display device of the present embodiment, as in the liquid crystal display device of the first embodiment, the voltage applied to the liquid crystal layer is lowered by the protective layer due to the anisotropic conductive effect of the protective layers 158 and 159. Never. Therefore, the cost of the drive IC and the drive circuit does not increase and the power consumption does not increase as the drive voltage increases.

In order to fully exert the effect of the anisotropic conductivity of the protective layer, the stripe electrode 153 and the protective layer 158, and the pixel electrode 155 and the protective layer 159.
Need to be in direct contact with each other and have electrical continuity between them. The bus line 154 and the protective layer 159 may be in direct contact with each other, but if they are electrically insulated from each other, the potential of the bus line will not leak to the liquid crystal layer side. Obtainable.

In the liquid crystal display device of the present embodiment, if either the stripe electrode 153 or the pixel electrode 155 is made of a metal such as aluminum or silver, a reflective liquid crystal display of a type having a reflective electrode on the inner surface of the panel. The device can be obtained. In this case, as in the second embodiment, the anisotropic conductor in the protective layer on the reflective electrode side can be made of a reflective material such as a metal, and the protective layer is given a scattering / reflection characteristic so that a liquid crystal display is obtained. The viewing angle of the device can be widened, and the effect of electrode protection can be enhanced by thickening the protective layer using a material having high anisotropic conductivity.

(Embodiment 4) FIG. 9 shows a sectional view of a liquid crystal display device according to Embodiment 4 of the present invention. The present embodiment is the same as the liquid crystal display device described in the third embodiment.
Instead of the protective layer 159 having anisotropic conductivity formed on the entire surface of the substrate 152, a protective layer 160 is formed so as to cover the bus wiring 154 and its periphery.

In the electrodes and elements formed on the lower substrate 152, if the bus wiring 154 is damaged, it becomes a line defect. In the liquid crystal display device of the present embodiment, due to the effect of forming the protective layer, the bus wiring is damaged even when the substrate is bent during manufacture or use of the liquid crystal display device or curved for curved display. There is nothing to do. Further, due to the effect of the protective layer, there is an advantage that the bus wiring is not scratched and damaged during the rubbing process of the liquid crystal panel manufacturing process and various kinds of handling.

In the case of the present embodiment, the pixel electrode 1
Since the protective layer is not formed on 55, the voltage applied to the liquid crystal layer does not decrease.

Although no protective layer is formed on the upper substrate 151 in FIG. 9, a protective layer exhibiting anisotropic conductivity is formed on the stripe electrode 153, as in the liquid crystal display device shown in FIG. Then, similarly to the description in the third embodiment,
It is possible to prevent the stripe electrode from being damaged.

(Fifth Embodiment) FIG. 10 shows a sectional view of a liquid crystal display device according to a fifth embodiment of the present invention. In the figure, 201 and 202 are substrates. A thin film transistor (TF) as a switching element is formed on the substrate 202.
T) 208, a gate line (scanning line) 205 for opening and closing a switch, and a pixel electrode are formed. The pixel electrode corresponding to one pixel is divided into two sub-pixels 206 and 207.
Are connected.

Signal lines 203 and 204 extending in a direction substantially orthogonal to the gate line are formed on the substrate 201. The signal line 203 is connected to the pixel electrode 206 and the signal line 204.
Respectively face the pixel electrodes 207. A liquid crystal layer 209 is provided between both substrates, and a voltage between the signal line and the pixel electrode is applied to this liquid crystal layer.

Although not shown in FIG. 10, a polarizing plate is formed on both outer sides of the substrates as needed, and a sealing material is provided at the outer ends of the substrates to cover the periphery of the liquid crystal layer. There is.

The voltage writing operation of this embodiment is carried out according to Japan Display '86, pages 80-83 and 84.
~ 87. That is, when a scanning signal is applied to the scanning line 205, the TFT 208 is turned on,
The pixel electrodes 206 and 207 become conductive. At this time, if a predetermined voltage is applied to the signal line, the two signal lines 203 and 2
The potential difference 04 is written to the left and right sub-pixels by almost half. For example, + Vs is applied to the signal line 203 and − is applied to the signal line 204.
When a potential of Vs is applied, the signal line 203 and the pixel electrode 206
A voltage of + Vs is applied between the signal line 204 and the pixel electrode 20.
A voltage of -Vs is applied during 7. If this scanning line is set to the non-scanning state after the potential of each part is stabilized, the TFT2
08 is turned off, and the signal electrode 203 and the pixel electrode 20 are turned off.
6 (+ Vs) and the voltage between the signal electrode 204 and the pixel electrode 207 (-Vs) are the signal lines 203 and 20.
Even if the potential of 4 becomes a different potential for writing a signal to another scanning line, the voltage value at the time of writing is held.

As described above, since the transistor is used as the switching element, the holding characteristic of the applied voltage is better than that using the diode, and the signal voltage does not leak. As a result, it is possible to obtain good display characteristics with high contrast and transmittance.

As the flexible substrate, polycarbonate,
A plate or film such as polyethylene terephthalate or polyether sulfone can be used. Since the heat-resistant temperature of these substrates is about several hundreds to several hundreds of degrees, it is desirable to use an organic TFT for the thin film transistor and lower the element manufacturing temperature.

In the liquid crystal display device of this embodiment,
Since a flexible substrate is used, curved display can be performed, and the degree of freedom in designing various devices is increased. In addition, since the board does not break even if it flexes during use, it is no longer necessary to use a highly rigid housing, which makes it possible to reduce the weight of various portable devices and the like, and to reduce external force on the display surface. It can be used for additional purposes.

Further, in the liquid crystal display device of the present embodiment, the scanning line 205 is formed on the substrate 202, and the signal lines 203 and 204 orthogonal thereto are formed on the substrate 201. There is no overlap of wiring on the board. Therefore, even when the substrate is bent at the time of making or using the liquid crystal display device, or when the substrate is curved and used due to a design problem of the device, a short circuit between wirings is unlikely to occur. Therefore, there are advantages that the product yield is improved and the product life is extended.

As a result, it is possible to stably supply a liquid crystal display device having good display characteristics, being thin and lightweight, hard to break, and capable of being processed into various shapes and curved shapes and having excellent designability at low cost.

Compared with the ones described in the seventh to ninth embodiments, the configuration of the present embodiment has a symmetrical element configuration around the TFT, so that the flicker caused by the asymmetry of the electrical characteristics is caused. Has the advantage of being less likely to occur.

(Sixth Embodiment) FIG. 11 shows a sectional view of a liquid crystal display device according to a sixth embodiment of the present invention. In this embodiment, protective layers 210 and 211 exhibiting anisotropic conductivity are added to the liquid crystal display device of the fifth embodiment. A protective layer 210 is formed on the upper substrate 201 so as to cover the signal electrodes 203 and 204, and a protective layer 211 is formed on the lower substrate 202 so as to cover the pixel electrodes 206 and 207 and the scanning electrode 205. ing.

The liquid crystal display device of the present embodiment has the following features in addition to the features described in the fifth embodiment. That is, similarly to the first embodiment, even when the substrate is bent or curved, the effect of the protective layer is unlikely to damage or disconnect the signal line or the scanning line, and the anisotropic conductivity The effect does not lower the voltage applied to the liquid crystal layer. As a result, compared with the liquid crystal display device of the fifth embodiment, the yield and life of the liquid crystal display device are further improved, and the degree of freedom in design is further improved. The protective layer on the electrodes also has an advantage that the electrodes are not damaged and are not damaged when the rubbing process in the liquid crystal panel manufacturing process or various handlings are performed.

(Embodiment 7) FIG. 12 is a sectional view of a liquid crystal display device according to Embodiment 7 of the present invention. As in the fifth embodiment, the present embodiment eliminates the wiring crossover on the flexible substrate, so that the substrate is bent during the manufacturing process or during use, or the substrate is curved according to design requirements. Even when it is used, the gate line and the signal line are less likely to be short-circuited.

In FIG. 12, reference numerals 301 and 302 denote substrates. On the substrate 302, a thin film transistor (TFT) 307 as a switching element, a gate line (scanning line) 304 for opening and closing a switch, and a common wiring 30.
5 and the pixel electrode 307 are formed. Board 30
A signal line 303 extending in a direction substantially orthogonal to the gate line is formed on the first line 1. Liquid crystal layer 30 between both substrates
8 and a voltage between the signal line and the pixel electrode is applied to this liquid crystal layer.

Although not shown in FIG. 12, polarizing plates are formed outside both substrates as needed, and a sealing material is provided at the outer ends of the substrates to cover the periphery of the liquid crystal layer. There is.

The voltage writing operation according to the present embodiment is performed on pages 80 to 83 and 84 of Japan Display '86.
~ 87. That is, the common wiring 305
When a scanning signal is applied to the scanning line 304 by applying a constant common potential (eg, ground potential) to the pixel electrode 305, the pixel electrode 305 becomes the ground potential. If a predetermined voltage (Vs) is applied to the signal line 303, the signal line 30
A voltage Vs is applied to the liquid crystal layer 308 between the pixel electrode 3 and the pixel electrode 305. When this scanning line is set to the non-scanning state after the potential of each part is stabilized, the TFT 307 is turned off and the pixel 3
06 is in a floating state. As a result, the voltage Vs between the signal electrode 303 and the pixel electrode 306 is
Even if the potential of 3 becomes a different potential for writing a signal to another scanning line, the voltage value at the time of writing is held.

Since the transistor is used as the switching element in this manner, as in the case of the fifth embodiment, the contrast and the transmittance are high, and good display characteristics can be obtained.

As the flexible substrate, polycarbonate,
A plate or film such as polyethylene terephthalate or polyether sulfone can be used. Since the heat-resistant temperature of these substrates is about several hundreds to several hundreds of degrees, it is desirable to use an organic TFT for the thin film transistor and lower the element manufacturing temperature.

Also in the liquid crystal display device of this embodiment,
Since a flexible substrate is used, curved display can be performed, and the degree of freedom in designing various devices is increased. In addition, since the board does not break even if it flexes during use, it is no longer necessary to use a highly rigid housing, which makes it possible to reduce the weight of various portable devices and the like, and to reduce external force on the display surface. It can be used for additional purposes.

Furthermore, the liquid crystal display device of the present embodiment is
The scanning line 304 and the common wiring 305 are parallel to each other on the substrate 30.
2 and the signal line 303 orthogonal thereto is formed on the substrate 301, so that there is no wiring overlapping portion on any of the substrates as in the fifth embodiment. Therefore, even when the substrate is bent at the time of making or using the liquid crystal display device, or when the substrate is curved and used due to a design problem of the device, a short circuit between wirings is unlikely to occur. Therefore, there are advantages that the product yield is improved and the product life is extended.

As a result, it is possible to stably and inexpensively supply a liquid crystal display device having good display characteristics, being thin and lightweight, hardly cracking, being capable of being processed into various shapes and curved shapes and having excellent designability.

Compared with the structure described in the fifth embodiment, in the structure of this embodiment, the potential of the pixel electrode always returns to the common potential at the time of writing a signal for each scan. Therefore, the pixel electrode is not charged due to the influence of static electricity on the substrate, and the electric field generated thereby does not damage the display.

(Embodiment 8) FIG. 13 is a sectional view of a liquid crystal display device according to Embodiment 8 of the present invention. In this embodiment, in the liquid crystal display device of Embodiment 7, the drain 309 of the TFT 307 connected to the gate line 304b is connected to the preceding gate line 304a and the common wiring 305 is omitted.

When the scanning potential is applied to the gate line 304b, the gate line 304a in the preceding stage is at the non-scanning potential after the scanning is completed. The liquid crystal display device of the present embodiment uses this non-scanning potential as a common potential, but other operations are the same as those described in the seventh embodiment.

Also in the present embodiment, as in the case of the seventh embodiment, there is no overlapping portion of wiring on any of the substrates, the substrates are bent at the time of making or using the liquid crystal display device, and there is a problem in designing the device. Even if the substrate is bent and used, a short circuit between wirings is unlikely to occur. Also, since a transistor is used as the switching element, the holding characteristic of the applied voltage is better than that using a diode,
There is also an advantage that good display characteristics with high contrast and transmittance can be obtained.

Further, as compared with the seventh embodiment, since there is no common wiring, the area of the pixel can be increased and the aperture ratio is increased. As a result, there is also an advantage that a brighter display can be performed.

As a result, it is possible to stably supply a liquid crystal display device having good display characteristics, being thin and light weight, hard to break, and capable of being processed into various shapes and curved shapes and having an excellent design property at low cost.

The same effect can be obtained by slightly changing the planar arrangement on the substrate 302 side so that the TFT 307 is located above the pixel electrode 306 and connecting the drain 309 to the scanning line of the next stage. .

(Ninth Embodiment) FIG. 14 shows a sectional view of a liquid crystal display device according to a ninth embodiment of the present invention. In this embodiment, protective layers 311 and 312 exhibiting anisotropic conductivity are added to the liquid crystal display device of the eighth embodiment. A protective layer 3 is formed on the upper substrate 301 so as to cover the signal electrodes 303.
10 is formed, and a protective layer 311 is formed on the lower substrate 302 so as to cover the pixel electrodes 306 and the scanning electrodes 304.

The liquid crystal display device of this embodiment has the following features in addition to the features described in the eighth embodiment. That is, similarly to the first embodiment, even when the substrate is bent or curved, the effect of the protective layer is unlikely to damage or disconnect the signal line or the scanning line, and the anisotropic conductivity The effect does not lower the voltage applied to the liquid crystal layer. As a result, compared with the liquid crystal display device of the eighth embodiment, the yield and life of the liquid crystal display device are further improved, and the degree of freedom in design is further improved. Further, due to the effect of the protective layer, there is an advantage that the bus wiring is not scratched and damaged during the rubbing process of the liquid crystal panel manufacturing process and various kinds of handling.

In the above description, the protective layer having anisotropic conductivity is added to the liquid crystal display device of FIG. 13 described in the eighth embodiment, but instead of this, the seventh embodiment is described. The same effect can be obtained by adding a protective layer having anisotropic conductivity to the liquid crystal display device shown in FIG.

In the liquid crystal display device described in the fifth to ninth embodiments, either the signal electrode or the pixel electrode is made of metal such as aluminum or silver, and this is a reflection type liquid crystal having a reflection plate on the inner surface of the panel. It can also be a display device.

In particular, in the case of the liquid crystal display device described in the sixth or ninth embodiment, as in the second embodiment, the anisotropic conductor in the protective layer on the reflective electrode side is made of metal or the like. It can be composed of a reflective material. In this case, the reflective material can be dispersed well to give the protective layer a scattering reflection characteristic, and the viewing angle of the liquid crystal display device can be widened. Further, since a material having anisotropic conductivity higher than that of the transparent conductor can be used, the protective layer can be made thicker to enhance the effect of electrode protection as compared with the case of using the transparent anisotropic conductor.

Further, in the liquid crystal display device described in the fifth, seventh and eighth embodiments, the scanning electrode functions only as the bus wiring, and the voltage is not directly applied to the pixel. Therefore, similarly to the fourth embodiment, by covering the scan electrodes and their peripheral portions with the protective layer, damage to the scan electrodes can be prevented without lowering the voltage applied to the liquid crystal layer. Further, by forming a protective film having anisotropic conductivity on the signal electrodes on the opposing substrate, it is possible to prevent the signal electrodes from being damaged.

[0099]

As described above, according to the present invention, a protective layer having anisotropic conductivity is added to an electrode layer on a flexible substrate,
Alternatively, by selectively forming a protective layer on and around the bus wiring portion of the active matrix type display using a flexible substrate, electrodes and bus wiring can be formed when the substrate is bent or curved display is performed. Will not be damaged,
Product yield is improved, product life is extended, and product applications are expanded. In addition, the addition of the protective layer does not cause a loss in the voltage applied to the liquid crystal layer, which does not increase the cost of the drive IC or the circuit or increase the power consumption.

Further, according to the present invention, in the liquid crystal display device in which the thin film transistor is formed on the flexible substrate, the gate wiring and the signal wiring are formed on the substrates on different sides to eliminate the crossover between them. This prevents short circuit between the gate wiring and the signal wiring on the flexible substrate when the substrate is bent or curved surface display is performed, improving the product yield, extending the product life, and improving the product application. To enlarge.

[Brief description of drawings]

FIG. 1 is a sectional view showing a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view schematically showing the occurrence of electrode damage in a conventional liquid crystal display device.

FIG. 3 is a cross-sectional view schematically illustrating a bent state of a substrate used in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a sectional view schematically showing stress applied to electrodes in a conventional liquid crystal display device.

FIG. 5 is a sectional view schematically showing stress applied to electrodes in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view schematically illustrating an example of a protective layer having anisotropic conductivity.

FIG. 7 is a sectional view showing a liquid crystal display device according to a second embodiment of the present invention.

FIG. 8 is a perspective view showing a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is a perspective view showing a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 10 is a perspective view showing a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 11 is a perspective view showing a liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 12 is a perspective view showing a liquid crystal display device according to a seventh embodiment of the present invention.

FIG. 13 is a perspective view showing a liquid crystal display device according to Embodiment 8 of the present invention.

FIG. 14 is a perspective view showing a liquid crystal display device according to a ninth embodiment of the present invention.

[Explanation of symbols]

101, 102, 131, 132, 151, 152, 2
01,202,301,302 Flexible substrate 103,104,153,203,204,303 Electrode 105,106,135,136,158,159,2
10, 211, 310, 311 Anisotropic conductive protective layer 107, 137, 157, 209, 308 Liquid crystal layer 108, 138 Sealing material 109, 110, 139 Polarizing plate 111, 112, 113 External force 114, 115, 116, 117 Stress 121 conductive particles 133 transparent electrode 134 reflective electrode 154 bus wiring 155, 206, 207, 306 pixel electrode 156 2 terminal element 160 protective layer 205, 304 gate line 208, 307 thin film transistor 305 common wiring 309 drain

Continuation of front page (56) Reference JP-A-6-222376 (JP, A) JP-A-10-123557 (JP, A) JP-A-6-347825 (JP, A) JP-A-8-136954 (JP , A) JP-A-8-222781 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/1333 505 G02F 1/1368 G09F 9/30 348

Claims (4)

(57) [Claims] 1. A liquid crystal layer comprising two flexible substrates each having an electrode layer for applying a voltage, and a liquid crystal layer sandwiched between the two flexible substrates. , Showing conductivity in the thickness direction on at least one surface of the electrode layer
The liquid crystal display device is characterized in that a protective layer having anisotropic conductivity, which is not conductive, is formed in the in- plane direction . 2. A pixel electrode having a liquid crystal layer sandwiched between two flexible substrates, the pixel electrodes being arranged in a matrix on at least one of the flexible substrates, and arranged in the vicinity thereof. switching elements, said bus lines for applying a predetermined signal to the switching element, and the bus line and a protective layer formed to cover the vicinity thereof are formed, before
The protective layer is electrically conductive in the thickness direction but in the in-plane direction.
A liquid crystal display device having anisotropic conductivity, which is not conductive . 3. An electrode having a predetermined shape and formed on the electrode.
And shows conductivity in the thickness direction, but in-plane direction
The liquid crystal display device substrate made of a flexible substrate to have a protective layer exhibiting no anisotropic conductive conductivity to. 4. An electrode having a predetermined shape and formed on the electrode.
And shows conductivity in the thickness direction, but in-plane direction
May have a non-conductive protective layer with anisotropic conductivity.
A method for manufacturing a substrate for a liquid crystal display device made of a flexible base material
And then forming an electrode having a predetermined shape on the flexible substrate, applying a resin in which conductive particles are dispersed in a base material, and curing the resin while compressing the resin in the thickness direction. A method for manufacturing a substrate for a liquid crystal display device.