JPH09288278A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify structure, to reduce cost and to completely cope with fine patterns by arranging a backlight between a liquid crystal display element and a flexible circuit board. SOLUTION: The backlight 3 is a light transmission body 4 made of an acrylic plate whose thickness is 5mm, and a light emitting element 5 is constituted by mounting an LED chip on the surface of the flexible circuit board 2. The backlight 3 is arranged at the back of the liquid crystal display element 1, and the flexible circuit board 2 connected to the element 1 is bent to be nearly U-shaped and fixed respectively by an intervening member 6. A connection terminal 11a formed on the circuit board 2 is conducted to the back and the outside of the backlight 3. By mounting an IC 9 for driving and a control circuit element 7 on the circuit board 2 and integrating the terminal 11a therewith, the number of the connection parts of input/output terminals is reduced from three to one, short circuit and faulty connection caused by floating are drastically reduced, and reliability in connection is enhanced.

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 specifically, to conductively connect a display element such as a liquid crystal panel used in a display unit of communication equipment and portable equipment and a circuit board for driving the display element. Liquid crystal display device.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, a liquid crystal display element and a PCB (Print-type) for driving and controlling the same are provided.
It is known that a circuit board such as Clrcuit-Board) is conductively connected by a wiring member or the like.

In particular, recently, a so-called COF (Chip-On-Film) in which an integrated circuit such as a driving IC chip is arranged on a wiring connecting member having flexibility is used to form a liquid crystal display element and a circuit board. Those that are electrically connected are often used.

FIG. 5 shows an example of a conventional liquid crystal display device using a so-called COF and a circuit board in which an integrated circuit such as a driving IC chip is arranged on a wiring member having the above-mentioned flexibility. FIG.

In the figure, reference numeral 1 denotes a liquid crystal display element, and a control circuit element 7 is mounted on the back side thereof, particularly on the back side of a backlight 3 composed of a light guide 4 and a light emitting element 5 in the case of the figure. The control circuit board 10 is arranged, and the connection circuit board 11 and the liquid crystal display element 1 are conductively connected by the flexible wiring member 2 which is bent in a substantially U-shape. On the wiring member, an IC chip 9 for driving a liquid crystal is so-called TAB.
It is mounted by a (Tape-Automated-Bonding) method or the like. Reference numeral 11 denotes a connection connector formed with an input terminal 11a for connecting a liquid crystal display device constituted by them and an external circuit (not shown), which is connected to the control circuit board 10 and is connected to the liquid crystal display device. It is pulled out.

In addition, the flexible circuit board 2, the control circuit board 10, and the connection circuit board 11 have respective inputs,
The output terminals are electrically connected by soldering.

[0007]

However, in the above-mentioned conventional liquid crystal display device, the number of constituent parts such as the circuit board and the connecting member constituting the liquid crystal display device is large, and as described above, the respective input terminals and Since the output terminals are connected by soldering or the like, a connection failure, a short circuit, or the like occurs, and sufficient connection reliability cannot be obtained. Further, in order to solve the above problem, a connecting method using an adhesive or the like has been proposed instead of soldering, but a large effect cannot be expected because the number of connecting points does not decrease. In recent liquid crystal display devices, the number of electrodes of the liquid crystal display element 1 has increased with the trend of colorization, high density, and compactness, and the electrode pattern tends to be miniaturized. Accordingly, the increase in the number of connection terminal pitches and the miniaturization tend to be more and more accelerated.

Further, when the number of parts is large, the number of assembling steps is increased, and the structure such as fixing of the wiring member is complicated, and the device becomes thick and cannot be made compact. Therefore, the present invention solves the above-mentioned drawbacks, and the object of the present invention is to simplify the structure of the entire device to configure the device compactly, at a low cost, and to sufficiently cope with the fine patterning. Moreover, it is an object of the present invention to provide a highly reliable liquid crystal display device.

[0009]

According to the first aspect of the present invention,
In a liquid crystal display device in which a liquid crystal display device in which a liquid crystal composition is sealed in a pair of substrates having a transparent electrode on the inner surface and a circuit board for driving and controlling the same are electrically connected, a liquid crystal driving IC and a control circuit device are mounted, and A flexible circuit board having an external connection terminal and integrally configured is conductively connected to the liquid crystal display element, and a backlight is arranged and fixed between the liquid crystal display element and the flexible circuit board. It is characterized by being

According to a second aspect of the present invention, the liquid crystal display element and the flexible circuit board are fixed to the light guide body by an elastic member and a reflecting member, and an intervening member made of an adhesive. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided.

According to a third aspect of the present invention, the light emitting element of the backlight is mounted on the flexible circuit board.

[0012]

According to the first aspect of the present invention, since the liquid crystal driving IC and the control circuit are mounted on the flexible circuit board integrally formed with the external connection terminals, the number of conductive connection points is reduced and connection failure or the like occurs. The risk is reduced as much as possible, and the reliability of connection with the liquid crystal display element can be improved. Further, by fixing only the liquid crystal display element and the flexible circuit board to the backlight, the structure can be simplified and the thickness of the device can be reduced.

According to the second aspect of the invention, the liquid crystal display element and the flexible circuit board are fixed to the backlight by an intervening member with an adhesive having elasticity and reflection function, so that light from the light emitting element is guided. It is possible to efficiently guide the light to the body and secure sufficient brightness, and the elastic material absorbs the force against the vibration shock from the outside, and the liquid crystal display element can be prevented from being damaged.

According to the third aspect of the present invention, the light emitting element of the backlight is mounted on the flexible circuit board, so that the number of man-hours for mounting the component can be reduced and an inexpensive liquid crystal display device can be realized.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

[Embodiment 1] FIG. 1 is a perspective view of a liquid crystal display device showing an embodiment of the liquid crystal display device of the present invention, and FIG.
FIG. 3 is a cross-sectional view of an important part for explaining the structure of FIG. 3, and FIG.

In this embodiment, as shown in FIG. 2, an IC 9 for driving a liquid crystal such as an LSI is provided on the liquid crystal display element 1 in which a liquid crystal composition is enclosed in a pair of substrates having transparent electrodes on the inner surface and a flexible circuit board 2. Are implemented by the so-called TAB method or the like. An IC for driving the liquid crystal is provided on the flexible circuit board 2.
Control circuit element 7 for controlling 9 and temperature correction
Has been implemented. The flexible circuit board 2 is integrally formed with an external connection terminal 11a so as to enable electrical connection with an external circuit.

Further, regarding the details of the above-mentioned constituent materials, in the flexible circuit board 2, the polyimide film 7 is formed on the base film.
5μm on one side 35μm thick copper foil Ni7μm, Au
A circuit was formed by plating with 0.5 μm. Gold bumps were formed on the driving IC 9 and mounted by the TAB method, and the control circuit element 7 was also surface mounted on the wiring terminals of the flexible circuit board 2 by soldering. Then, the connection terminal 11a for connecting to the outside is formed by exposing the copper foil by overhanging the polyimide substrate.
As a structure of the terminal portion, a reinforcing plate may be attached to the back surface of the base film material so that it can be connected to an external connector. In the liquid crystal display element 1 of this embodiment, a connection terminal led out from a transparent electrode is formed on the lower glass.

The flexible circuit board 2 on which various components are integrally formed as described above and the connection terminals of the transparent electrodes of the liquid crystal display element 1 are aligned and electrically connected through the anisotropic conductive adhesive 8. Has been taken.

In the illustrated example, the intervening member 6 uses neoprene rubber as the elastic member 6a and an aluminum metal plate as the reflecting member 6b to bond the base materials to each other, and the front surface and the back surface are coated with the adhesive material. ing. The backlight 3 is a light guide 4 made of an acrylic plate having a thickness of 5 mm, and the light emitting element 5 has an LED chip surface-mounted on the flexible circuit board 2.

The structure of the liquid crystal display device of this embodiment is as follows.
The backlight 3 configured as described above is arranged on the back surface of the liquid crystal display element 1, and the flexible circuit board 2 connected to the liquid crystal display element 1 is bent into a substantially U-shape, and the interposition is provided. Each is fixed by the member 6. Further, the connection terminals formed on the flexible circuit board 2 are led out to the back surface and the outside of the backlight 3. As described above, according to the present invention, the driving IC 9 and the control circuit element 7 are mounted on the flexible circuit board 2 and the connection terminal 11a is integrated, so that the liquid crystal display device is different from the conventional liquid crystal display device. , 1 to 3 input / output terminal connections
It was possible to improve the connection reliability by reducing the number of places and the connection failure due to short circuit and floating.

Further, since it is not necessary to use a wiring board such as a PCB conventionally used for mounting the control circuit element 7 or the like, it is possible to realize a low cost liquid crystal display device because the cost of parts can be reduced. Further, the liquid crystal display element 1 and the flexible circuit board 2
It is advantageous in terms of vibration resistance and impact resistance that the LCD is fixed to the backlight by the intervening member 6. For example, the liquid crystal display element 1 or the like is inadvertently displaced due to an external impact and the connection point is peeled off or the wire is disconnected. There is no fear and the reliability can be improved. Further, the interposition member 6 is made of a reflective material 6b.
Since the structure is composed of, the light from the light source can be efficiently guided to the light guide 4, and the light leakage can be prevented.
The display of the liquid crystal display element can be surely visually recognized when used at night.

By mounting the light source of the backlight on the flexible circuit board 2, the number of assembling and mounting steps of the liquid crystal display device can be reduced and the connection reliability can be improved.

When a portable liquid crystal display device was manufactured by the structure based on the above-mentioned embodiment, the short circuit between terminals and the connection failure could be reduced as compared with the conventional one, and the mounting yield was improved. Further, the liquid crystal display device was subjected to an aging test and evaluated, and as a result, a thermal cycle test (-20 ° C. 30 min.
400 cycles at 60 ° C for 30 minutes and humidity resistance test (60 ° C
Normal operation was confirmed even after 400 hours at 90% RH, demonstrating high reliability and durability.

[Embodiment 2] FIG. 4 shows a flexible circuit board 2 in which various parts of the liquid crystal display device of the present invention are integrally formed.
9 is a cross-sectional view showing another embodiment of the liquid crystal display body in which the transparent electrode connection terminal 1a of the liquid crystal display element 1 is electrically connected through the anisotropic conductive adhesive 8. FIG.

This embodiment is an embodiment in which the connection terminal of the transparent electrode is led out to the upper glass side in the liquid crystal display element 1 and unnecessary portions other than the display area are made small, and the structure is flexible. The circuit board 2 uses the same base material as in Example 1, and has a structure in which the patterned copper foil of the connection terminal portion of the liquid crystal display element 1 is bent on the back surface of the polyimide base film. The connection with the liquid crystal display device 1 or the structure for assembling the backlight 3 is the same as the first embodiment.
Is the same as

As described above, according to the present invention, since the flexible circuit board 2 can be bent within the size of the electrode terminals of the liquid crystal display 1, there is no protrusion to the outside. As a result, unnecessary parts outside the display area can be accommodated within the connection terminal width of 3 mm of the liquid crystal display element as compared with the conventional example, and the size of the liquid crystal display device can be reduced by 10 mm as a completed product, realizing a more compact liquid crystal display device. did it.

[0028]

According to the first aspect of the present invention, since the liquid crystal driving IC 9 and the control circuit element 7 are provided with the external connection terminal 11a and mounted on the flexible circuit board 2, they are integrated. Compared with the conventional liquid crystal display device, the number of parts can be reduced and the connection reliability can be improved. Furthermore, the entire device can be made compact and compact, and the device can be easily assembled.

According to the second aspect of the invention, the liquid crystal display element 1 and the flexible circuit board 2 are fixed to the backlight 3 by the intervening member 6 having an elasticity and a reflection function, which is coated with an adhesive material. Prevents light from leaking from Light 3,
The brightness efficiency can be increased. In addition, the elastic material can absorb the vibration shock from the outside, prevent the liquid crystal display device from being damaged, and cause a large stress to the liquid crystal display element 1.
Even when is displaced, the connecting portion is not displaced, so that the electrical connection between the liquid crystal display element 1 and the flexible circuit board 2 can be ensured.

According to the invention of claim 3, the light emitting element 5
Since it is mounted on the flexible circuit board 2, components can be mounted in the same process as the control element, and the number of assembling steps can be reduced.
Furthermore, there is an effect that a substrate for wiring and connecting the light guide element is not necessary, and the cost is low, the reliability is high, and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view showing an embodiment of a liquid crystal display device of the present invention.

3 is a cross-sectional view for explaining the structure of the interposition member in FIG.

FIG. 4 is a cross-sectional view showing another embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view showing a conventional liquid crystal display device.

[Explanation of symbols]

 1. Liquid crystal display device 2. Flexible circuit board 3. Backlight 4. Light guide 5. Light emitting element 6. Intervening member 7. Control circuit element 8. Anisotropic conductive film 9. Liquid crystal driving IC 10. Control circuit board 11. Connection circuit board

Claims (3)

[Claims] 1. A liquid crystal display device in which a liquid crystal display device, in which a liquid crystal composition is sealed in a pair of substrates having transparent electrodes on the inner surfaces thereof, and a circuit board for driving and controlling the same are conductively connected to each other. Is mounted on the liquid crystal display element, and the flexible circuit board integrally formed with the external connection terminal is conductively connected to the liquid crystal display element, and a backlight is provided between the liquid crystal display element and the flexible circuit board. A liquid crystal display device, which is arranged and fixed. 2. The liquid crystal display element and the flexible circuit board are respectively fixed to the light guide by an intervening member made of a member having elasticity and a reflection function and an adhesive. The liquid crystal display device according to claim 1. 3. The light emitting device of the backlight is mounted on the flexible circuit board.
The liquid crystal display device as described in the above.