JP2000098395A - Liquid crystal display element, method of manufacturing the same, and liquid crystal display device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a liquid crystal display device using all liquid crystal materials including a liquid crystal material exhibiting a smectic liquid crystal phase, capable of preventing occurrence of alignment breakdown, a method of manufacturing the same, and a liquid crystal. A display device is provided. SOLUTION: A frame material 6 is arranged on a surface of an array substrate 2 so as to surround a liquid crystal display unit, and protection is provided on an upper portion of the frame material 6 so as to be substantially parallel to the array substrate 2 and the counter substrate 4. Transparent plate 7 is arranged. As described above, since the liquid crystal display unit is protected so as to be surrounded by the frame member 6 and the protective transparent plate 7, when a stress is applied to the substrates 2 and 4 in the transporting process and the assembling process to the apparatus. In addition, bending is suppressed, and destruction of liquid crystal alignment is prevented.

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, a method of manufacturing the same, and a liquid crystal display device, and more particularly to a liquid crystal display device more suitable when a liquid crystal material exhibiting a smectic liquid crystal phase is used in a specific temperature range including room temperature. And a method of manufacturing the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display elements are the most promising among flat panel displays which are desired to be developed for saving space and reducing power consumption. Currently, a nematic liquid crystal is used as a liquid crystal material, and a thin film transistor (TFT) drives a pixel electrode.
A TN mode or an STN mode in which a twist angle is further increased by using a nematic liquid crystal as a liquid crystal material is used.

In both types, a full-color display of about 20 inches has already been achieved, and is commercially available as an information terminal display. These displays are useful for limited applications such as word processors and spreadsheets.
At present, it has almost satisfactory characteristics.

However, the display based on the STN method is still insufficient in response speed for these applications. In the case of the STN method, the viewing angle is extremely narrow. Improvements for widening the viewing angle using a retardation film or the like are being studied, but a sufficient viewing angle has not been obtained. The TN mode liquid crystal element provided with a TFT element is almost satisfactory in response speed in the present usage form. However, when a larger display is created or when a moving image is displayed, difficulties are expected in terms of response speed.

[0005] Further, the TFT-TN method is
Although the viewing angle is wider than that of the STN method, it becomes extremely narrow when a full-color image is displayed. This is the TFT
-It is expected that the use of the display by the TN method will be limited.

As described above, the liquid crystal display device is expected as an information terminal, and although it satisfies the characteristics required at present for specific applications, it is still insufficient in view angle and response speed. .

A display system using a smectic liquid crystal having a higher order (specifically, a chiral smectic C phase) instead of a nematic liquid crystal has been proposed. A typical example is the surface-stabilized ferroelectric liquid crystal (s) disclosed by Clark and Lagabal in 1980.
urface stabilized ferroe1ectric liquid crystal: SSF
LC.NAClark and STLagererwall Appl.Phys.Lett., 3
6,899 (1980)). In this method, the helical structure of the chiral smectic C phase is solved by the interaction between the alignment film and the liquid crystal material, and switching is performed by the torque generated by the interaction between the spontaneous polarization generated at that time and the electric field. .

According to this method, the response speed is reduced from two digits to three.
The speed is increased by an order of magnitude, and the viewing angle increases like a CRT. Also,
The spontaneous polarization is stabilized only in two states in two directions perpendicular to the interface of the alignment film. For this reason, at the beginning of development, it was strongly expected as a display method having a memory property and not requiring a nonlinear active element such as a thin film transistor (TFT).

However, in the method using the smectic liquid crystal, since only two states are used, it is impossible to display a halftone. Considering the future use of displays, halftone display is indispensable, and several proposals have been made.

On the other hand, a display system using an antiferroelectric liquid crystal is known. This method uses an antiferroelectric liquid crystal phase (SmC
a)) and is disclosed in the following documents.

ADLChandani, T. Hagiwara, T. Suzuki, YO
uchi, H.Takezoe and A.Fukuda, Jpn.J.Appl.Phys., 27L72
9 (1988) In addition to the two stable states of ferroelectric liquid crystal,
It has an antiferroelectric liquid crystal structure when no voltage is applied. The following document discloses that by using this method, halftone display can be performed without driving with an active element. N.Yamamoto, N.Koshoubu, K.Mori, K.Nakamura, Y.Yamada,
Ferroelectrics, 1993, 149, pp.295 In this case, since it is possible to use positive and negative voltages,
This is effective in preventing a phenomenon such as image sticking. Further, the phenomenon that the optical axis returns to a specific position when no voltage is applied is also preferable for displaying a halftone. In recent years, there has been proposed a display method using an active element and using a chiral smectic C-type liquid crystal. In particular,
(J. Funfschilling and M. Schadt, J. Appl. Phys. 66
DHF (Distorted Helical Ferro) described in (8), 15)
electric Liquid Crystal) method or (JSPatel,
Appl. Phys. Lett. 60 (3), pp.280)
An LC (Twisted Ferroelectric Liquid Crystal) method has been proposed.

A display using the DHF system or the TFLC system is more expensive than other systems because of the use of active elements, but is superior in the following points. First
In addition, the display reliability of the halftone is excellent. DHF or T
In the FLC method, the change in transmittance with respect to the applied voltage is relatively gentle. Further, in the conventional surface-stabilized ferroelectric liquid crystal, there is no problem that halftone display is difficult due to switching with domain inversion.

Second, the DHF or TFLC system can be driven at a low voltage (0 to 5 V), resulting in low power consumption.

Further, in recent years, in the antiferroelectric liquid crystal, unlike the conventional antiferroelectric liquid crystal, there is an antiferroelectric liquid crystal which can be driven at a low voltage without exhibiting a hysteresis phenomenon. It has been found that it is particularly suitable for a liquid crystal device using an active element such as a TFD.

A liquid crystal display which drives a smectic liquid crystal such as TFLC, DHF and AFLC by an active element as described above overcomes the drawbacks of the conventional liquid crystal display.
It is possible to realize a liquid crystal display with a high response speed and a wide viewing angle. However, it is known that a liquid crystal display element generally using a smectic liquid crystal such as a ferroelectric liquid crystal and an antiferroelectric liquid crystal causes a defect in a liquid crystal portion due to stress applied to a substrate. This defect is caused by the disorder of the layer structure of the smectic liquid crystal.
Such a phenomenon has been pointed out at an early stage in research on ferroelectric liquid crystals, and has been discussed in many documents. When such a defect occurs, the portion where the defect occurs cannot display black when displaying black,
The contrast is extremely reduced, and normal display cannot be performed. Usually, in order to prevent the occurrence of such a defect, a polarizing plate is provided on two substrates of the liquid crystal display element, and a circuit board and the like are combined to form a module, which is then fixed to a housing. Then, a transparent substrate such as glass, which is usually referred to as a damper from the table, is fixed to a portion corresponding to the liquid crystal display portion of the housing to prevent external stress from being applied to the substrate forming the liquid crystal element. With such a structure, occurrence of alignment breakdown can be prevented.

Such a method is disclosed in, for example, JP-A-10-9
0656, JP-A-10-63202, JP-A-9-329777, JP-A-9-319311,
JP-A-9-304755, JP-A-9-73072, JP-A-6-160841, JP-A-6-148
632, JP-A-6-148606 and the like. According to these techniques, it is possible to prevent the occurrence of the orientation breakdown due to external stress after the product is completed. However, other problems as described below have occurred.

(1) After the liquid crystal injecting step, in the step of attaching a polarizing plate, the step of assembling a module, and the step of assembling a liquid crystal display element in a housing, there is a high possibility that an external stress will be applied to cause alignment breakdown.

(2) There is a high possibility that alignment destruction occurs in the transport system in each step, the transport system between each step, and other movements.

(3) Since liquid crystal display elements are often sold as modules, it is necessary to provide sufficient resistance to external stress in the module state, but conventional elements have low resistance.

(4) Since the size of the final product is increased due to the necessity of providing the damper, miniaturization is difficult.

In particular, the above items (1) and (2) are very serious problems in manufacturing. It is conceivable to solve the problems (1) and (2) by improving the production line. However, the main manufacturing equipment of the current TFT-LCD type liquid crystal display element is provided for the purpose of manufacturing a liquid crystal display element using a nematic liquid crystal,
No consideration has been given to the above problems (1) and (2). In order to improve these problems, a large facility cost is required.

[0022]

As described above, conventionally, there has been a problem that alignment breakdown is apt to occur during a period from injecting liquid crystal to a final step.

In view of the above circumstances, the present invention provides a liquid crystal display device capable of preventing occurrence of alignment breakdown in a liquid crystal display device using all liquid crystal materials including a liquid crystal material exhibiting a smectic liquid crystal phase, a method of manufacturing the same, and a method of manufacturing the same. It is an object to provide a liquid crystal display device.

[0024]

A liquid crystal display device according to the present invention is a device in which a liquid crystal material is sandwiched between two substrates, and the liquid crystal material is sandwiched on one surface of the substrate. A frame material arranged in an area excluding the liquid crystal display,
A protective transparent plate disposed on the frame member so as to be substantially parallel to the substrate.

Here, one of the two substrates has an area larger than that of the other substrate, and surrounds a side surface of the other substrate on a region excluding the liquid crystal display portion on the one substrate. The frame material may be arranged as described above, and the protective transparent plate may be arranged on the surface of the frame material.

A liquid crystal display device according to the present invention is characterized by comprising the above liquid crystal display element and an exterior member for holding an end of the one substrate in the liquid crystal display element via an elastic member.

In the case where the liquid crystal material is a liquid crystal material exhibiting a smectic liquid crystal phase in a predetermined temperature range including room temperature, the bending of the substrate is suppressed by the frame material and the protective transparent plate when stress is applied. The effect of preventing alignment breakdown is more effectively obtained.

When an active element is formed on the liquid crystal display portion of at least one of the two substrates, the active element often has irregularities on the substrate surface. The effect of preventing liquid crystal alignment destruction is greater.

According to the method of manufacturing a liquid crystal display device of the present invention, two substrates are bonded to each other at a fixed interval by using a spacer, and a liquid crystal material is injected between the two substrates and sealed. And a step of arranging a frame material in a region on one surface of the two substrates except for a liquid crystal display portion in which the liquid crystal material is injected, and so as to be substantially parallel to the substrates. Providing a protective transparent plate above the frame material.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device, a method for manufacturing the same and a liquid crystal display device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a longitudinal sectional structure of the liquid crystal display device according to the first embodiment of the present invention, and FIG. 2 shows a planar structure thereof. FIG. 1 corresponds to a longitudinal sectional view taken along line AA in FIG.

A pixel electrode and a thin film transistor (TFT) element are arranged in a matrix on a glass substrate having a thickness of 1.1 mm, and a polyimide (for example, Nippon Synthetic) having an alignment ability in a predetermined direction is provided on the surface thereof. Rubber company JALS55
0), an array substrate 2 having an alignment film formed thereon, and a color filter formed on a glass substrate, and an alignment film formed by subjecting a polyimide having alignment capability in a predetermined direction to a normal rubbing treatment was formed. The opposing substrate 4 is bonded via a sealing agent 3 such as an epoxy adhesive. here,
In order to accurately maintain the distance between the array substrate 2 and the opposing substrate 4, a spacer 8 having a desired height is formed on the surface of the opposing substrate 4. This spacer 8 is formed of two substrates 2
Immediately before laminating the layers 4 and 4, the member may be formed by spraying a spherical or cylindrical glass or resin member having a diameter corresponding to a desired height.

After bonding the substrates 2 and 4 and curing the sealant 3 by heating, for example, L manufactured by Chisso Petrochemical Co., Ltd.
A liquid crystal material such as IXON 1011 is injected from the injection port 10. Although the liquid crystal material is not particularly limited, the effect of preventing alignment breakdown can be more effectively obtained by the present embodiment when a smectic liquid crystal material such as a ferroelectric liquid crystal is used.

After the injection is completed, the injection port 10 is closed with a photocurable resin, and the resin is cured by light irradiation or heating. Optical members 1 and 5 such as polarizing plates are attached on the outer surfaces of the array substrate 2 and the counter substrate 4, respectively.

A frame member 6 made of an epoxy resin or the like having the appearance as shown in FIG. 4 is attached to the surface of the array substrate 2 using an epoxy resin adhesive or the like. The frame member 6 may be formed using a metal material or the like, but is preferably formed from a resin material such as an epoxy resin, an acrylic resin, or a urethane resin. The frame material 6 is not limited to the adhesive, and may be affixed with an adhesive tape having an adhesive component applied to both sides.

Thereafter, the protective transparent substrate 7 is attached to the upper surface of the frame member 6 using an adhesive or an adhesive tape. Conventionally, when a substrate is transported using an existing transport system in a process after the liquid crystal material is injected, stress may be applied to the substrates 2 and 4 to bend and the alignment may be broken. On the other hand, according to the present embodiment, the liquid crystal display portion is surrounded by the frame member 6 and the protective transparent substrate 7 on the array substrate 2, so that the liquid crystal display portion can be transported using the existing transport system. The bending of the substrates 2 and 4 is suppressed, and the alignment breakdown can be prevented. As a result, the production time per liquid crystal display element was reduced to about 1/3 compared to the conventional case.

The protective transparent substrate 7 is particularly indispensable when a smectic liquid crystal is used.
Furthermore, even after being incorporated into the system after transport, it can be used as it is without removal.

As a first comparative example, a structure was prepared in which the protective transparent substrate 7 was not provided in the first embodiment.
When the thus-obtained liquid crystal display device was transported in a transport step, all-orientational destruction occurred, and no good product was obtained. In the case where the steps of the transport system and the like are performed manually so as not to cause the alignment destruction, three times the manufacturing time is required. Further, even when such measures are taken, it is extremely difficult to prevent the alignment breakdown over the entire number.

FIG. 4 shows a second embodiment of the present invention.
This will be described with reference to FIG. In the above-described first embodiment, the optical member 5 such as a polarizing plate is attached to the upper surface of the counter substrate 4. However, there is a possibility that the orientation is broken during the sticking operation. Therefore, in the second embodiment, an optical member 5 such as a polarizing plate is attached on the protective transparent substrate 7 in order to prevent such a phenomenon.

By adopting such a configuration, it is possible to prevent the occurrence of alignment destruction during the sticking operation, but the viewing angle dependency may change. Therefore, in applications requiring a wide viewing angle, the first embodiment is more desirable.

In the first and second embodiments, since a space for placing the frame member 6 around the liquid crystal display portion on the array substrate 2 is required, the area of the non-display portion is increased. As a result, the area of the frame portion of the liquid crystal display element becomes wider than usual. On the other hand, in the third embodiment, as shown in FIG. 5, the frame member 6 is attached on the peripheral region of the counter substrate 4, and the protective transparent substrate 7 is attached on the upper surface of the frame member 6. By doing so, the non-display area can be reduced. In this case, the material of the frame member 6 is desirably silicone rubber or urethane rubber having low hardness so as not to damage the substrates 2, 4 and the liquid crystal display.

In the structure shown in the third embodiment, as in the case of the first embodiment, during the operation of attaching the optical member 5 such as the deflecting plate to the upper surface of the counter substrate 4, the alignment breakage occurs. There is a possibility that. In the fourth embodiment,
This problem is avoided by attaching an optical member 5 such as a polarizing plate to the upper surface of the protective transparent substrate 7 as shown in FIG.

The fifth embodiment of the present invention has a structure as shown in FIG. 7, in which a frame member 6 and a transparent protective substrate 7 are formed on the outer surface of the array substrate 2 and the optical member 5 is opposed to the optical member 5. It is stuck on the substrate 4. The sixth embodiment is as shown in FIG. 8, in which a frame member 6 and a transparent protection substrate 7 are formed on the outer surface of the array substrate 2 and an optical member 5 is provided on the surface of the protection transparent substrate 7. Is attached.

The liquid crystal display according to the seventh embodiment of the present invention includes the liquid crystal display device according to the first embodiment,
In a state where the backlight 15 is arranged on the back side, the backlight 15 is fixed while being sandwiched by protective external members 11 and 12 made of metal or resin via buffer members 13 and 14. As described above, the liquid crystal display element according to the first embodiment has a configuration in which the liquid crystal display portion is surrounded by the frame member 6 and the protective transparent substrate 7 on the array substrate 2, and is transported using an existing transport system. Also in this case, the bending of the substrates 2 and 4 is suppressed, and the alignment breakdown of the liquid crystal can be prevented.

The liquid crystal display device shown in FIG. 10 is shown as a second comparative example with respect to the seventh embodiment. Conventionally, unlike the second comparative example, the structure is such that the protective transparent substrate 7 is fixed to the protective external member 11, and the liquid crystal display is not protected by the frame material and the protective transparent plate. Was. For this reason, the array substrate 2 and the opposing substrate 4 were easily bent in the process of transporting the liquid crystal display element or assembling the device, and the liquid crystal alignment was easily broken. On the other hand, in the seventh embodiment, since the frame member 6 and the protective transparent substrate 7 are directly provided on the array substrate 2 of the liquid crystal display element to surround the liquid crystal display portion, the case where a stress is applied is provided. Also, the bending of the substrate is suppressed, and the alignment breakdown is prevented.

[0046]

As described above, according to the liquid crystal display device, the method of manufacturing the same, and the liquid crystal display device of the present invention, the liquid crystal display portion on one substrate of the device is protected by the frame material and the protective plate. Accordingly, even when a stress is applied in the transporting process or the assembling process after the liquid crystal is injected, the bending of the substrate is suppressed, and the occurrence of liquid crystal alignment destruction can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a sectional structure along a line AA in FIG. 2 of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a planar structure of the liquid crystal display element.

FIG. 3 is a perspective view showing the appearance of a frame material used in the liquid crystal display element.

FIG. 4 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device according to a fourth embodiment of the present invention.

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

FIG. 8 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device according to a seventh embodiment of the present invention.

FIG. 10 is a longitudinal sectional view showing a sectional structure of a liquid crystal display device as a second comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical member 2 Array substrate 3 Sealing material 4 Counter substrate 5 Optical member 6 Frame material 7 Protective transparent substrate 8 Spacer 9 Liquid crystal material 10 Injection 11, 12 Protective external member 13, 14 Buffering member 15 Backlight

Continued on the front page (72) Inventor Tomo Hasegawa 33 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Production Technology Research Institute (72) Inventor Rieko Iida 33 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Co., Ltd. Inside Toshiba Production Technology Research Institute (72) Inventor Kazuto Yamaguchi 33, Isoiso-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Production Technology Research Institute (72) Inventor Takeshi Yamaguchi 33, Shin-Isoko-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture 2H088 FA10 GA04 HA08 HA12 HA18 JA17 MA20 2H089 LA07 MA04Y NA24 QA04 RA13 TA06 TA09 TA12 TA15

Claims (7)

[Claims] 1. A liquid crystal display device in which a liquid crystal material is sandwiched between two substrates, wherein the liquid crystal material is arranged on a surface of one of the substrates excluding a liquid crystal display portion in which the liquid crystal material is sandwiched. A liquid crystal display device comprising: a frame member; and a protective transparent plate disposed on the frame member so as to be substantially parallel to the substrate. 2. One of the two substrates has an area larger than that of the other substrate, and surrounds a side surface of the other substrate on a region excluding the liquid crystal display portion on the one substrate. 2. The frame member is disposed on a surface of the frame member, and the protective transparent plate is disposed on a surface of the frame member.
The liquid crystal display element as described in the above. 3. A liquid crystal display device, comprising: the liquid crystal display element according to claim 2; and an exterior member that sandwiches an end of the one substrate in the liquid crystal display element via an elastic member. . 4. The liquid crystal display device according to claim 1, wherein the liquid crystal material is a liquid crystal material exhibiting a smectic liquid crystal phase in a predetermined temperature range including room temperature. . 5. The liquid crystal display element according to claim 1, wherein an active element is formed in the liquid crystal display portion on at least one of the two substrates. Or the liquid crystal display device according to 4. 6. A method of manufacturing a liquid crystal display device in which a liquid crystal material is sandwiched between two substrates, wherein a step of bonding the two substrates at a predetermined interval using a spacer; A step of injecting a liquid crystal material therebetween and sealing; and a step of disposing a frame material on a surface of one of the two substrates except for a liquid crystal display portion into which the liquid crystal material is injected, Providing a protective transparent plate above the frame material so as to be substantially parallel to the substrate. 7. The method according to claim 6, wherein said liquid crystal material is a liquid crystal material exhibiting a smectic liquid crystal phase in a predetermined temperature range including room temperature.