JP2000137446A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent display unevenness caused by temperature difference from occurring in the horizontal direction of a screen due to a circuit board mounted with heat- generating parts. SOLUTION: This liquid crystal display device is provided with a liquid crystal panel 1 wherein one substrate having a common electrode for composing display pixels and the other substrate having segment electrodes are arranged opposing each other via a liquid crystal layer, a common electrode driving circuit board 2 and a segment electrode driving circuit board 10 for applying signals for forming pixels on the common electrode and the segment electrodes respectively, and a backlight which is installed on the backside of the liquid crystal panel 1 and irradiates the panel 1 with illuminating light, and comprises at least a metallic upper frame 3 which is placed above the liquid crystal panel 1 and has an opening in a display area, and a metallic lower frame 4 which is placed under a light transmission plate 6 and coupled to the circumferential edge of the upper frame and thereby holds the liquid crystal panel 1, the common electrode driving circuit board 2, the segment electrode driving circuit board 10, and the backlight in one body, and a power circuit board 8 mounted with parts including heat-generating parts of the common electrode driving circuit board is mounted on the lower frame 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device, in which various driving circuit boards are arranged on the periphery of a liquid crystal panel, and a backlight is installed on the back surface of the liquid crystal panel to be integrated with upper and lower frames. The present invention relates to a liquid crystal display device fixed in a fixed manner.

[0002]

2. Description of the Related Art A liquid crystal display device, which is frequently used as a means for displaying image signals and various kinds of visible information, includes a liquid crystal panel for forming an image, and a driving signal and a voltage which are arranged on the periphery of the liquid crystal panel to apply the driving signal and voltage to the liquid crystal. And a driving circuit board for applying the light to the panel, and a backlight for irradiating illumination light for visualizing an image formed on the liquid crystal panel is laminated and sandwiched and fixed between upper and lower frames.

For example, in a liquid crystal display device using a passive type liquid crystal panel, a common electrode (also referred to as a scanning electrode, a line electrode, or a common electrode) corresponding to a row of the liquid crystal panel and a segment electrode (display electrode, By applying a display voltage corresponding to a value of a display signal to a data electrode or a pixel electrode), a pixel is displayed by controlling the orientation of liquid crystal corresponding to a predetermined pixel.

[0004] The driving technique of this type of liquid crystal display device is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-67628.

FIG. 7 is a schematic diagram for explaining a basic structure of a conventional liquid crystal display device. The common electrode includes a segment electrode drive circuit board 10 on two parallel sides of a liquid crystal panel 1 and a power supply circuit on one adjacent side thereof. An electrode drive circuit board 20 is disposed, and a light guide plate 6 and a linear lamp 1 are provided on the back of the liquid crystal panel.
A backlight consisting of 3 is installed. Then, the upper and lower portions of these components are covered with a metal frame, and the two are joined together at their peripheral edges and integrally fixed to form a liquid crystal display device. Note that the frame is not shown in FIG.

FIG. 8 is a cross-sectional view corresponding to a state cut along line AA of FIG. 7 for explaining the relationship between components of a conventional liquid crystal display device. The liquid crystal panel 1 has a liquid crystal layer sandwiched between two substrates, a polarizing plate and a phase difference plate laminated on the outer surface of each substrate, and a light diffusing plate between light guide plates 6 constituting a backlight. Optical seals such as a prism and a prism plate are arranged, but these are not shown.

After the backlight is held by the intermediate mold case 5 and the liquid crystal panel 1 is laminated thereon, the metal upper frame 3 having an opening in the display area and the backlight are sandwiched by the metal lower frame 4. And a claw 3a formed at the side end of the upper frame by reinforcing with a plastic mold 7
Is fixed by caulking to form an integrated liquid crystal display device.

[0008]

In the above-mentioned conventional liquid crystal display device, a so-called power circuit such as a power supply circuit is mounted on a common electrode drive circuit board arranged on one side edge (in general, one of right and left) of a liquid crystal panel. Or, as a separate circuit board on the same side as the installation position of the common electrode drive circuit board,
It is mounted at a position deviated from the liquid crystal panel.

With the recent increase in the size of the screen, heat generated by heat-generating components constituting a power circuit mounted on a drive circuit board disposed on a side edge of a liquid crystal panel (hereinafter, described as one side edge in the left-right direction) is generated. It tends to increase. This heat is transmitted to the side edges of the liquid crystal panel and affects the operation characteristics of the liquid crystal. This effect causes a temperature difference in the horizontal direction of the screen as the screen becomes larger. As a result, there is a problem that a luminance difference occurs between the displayed images on the left and right sides of the screen, and so-called display unevenness occurs.

It is an object of the present invention to provide a liquid crystal display device which solves the above-mentioned problems of the prior art and has a structure which does not cause display unevenness even on a large screen.

[0011]

In order to achieve the above-mentioned object, the present invention provides a driving circuit board for driving a liquid crystal panel, in which a power circuit board on which a heat-generating component is mounted is disposed on a lower frame. Is achieved in. The lower frame is generally made of a metal plate such as an aluminum plate or an iron plate having a good heat transfer coefficient. A concave portion for installing a power circuit board is formed in a part of the lower frame, and the power is formed in the concave portion. By storing the circuit board, the temperature difference between the left and right directions of the screen is eliminated, and the heat generated from the power circuit board is dissipated in the lower frame.

The typical constitutions of the present invention are as follows. That is, (1) a liquid crystal panel in which one substrate having a common electrode for forming a display pixel and the other substrate having a segment electrode are opposed to each other with a liquid crystal layer interposed therebetween, and each of the common electrode and the segment electrode A common electrode drive circuit board and a segment electrode drive circuit board that apply signals for forming pixels, and a backlight that is installed on the back of the liquid crystal panel and irradiates the liquid crystal panel with illumination light; A metal upper frame disposed above and having an opening in a display area; and a liquid crystal panel, a common electrode driving circuit board, and a segment electrode driving circuit disposed below the backlight and coupled to a periphery of the upper frame. At least a metal lower frame that integrally holds the substrate and the backlight, including a heat-generating component of the common electrode drive circuit board A power circuit board on which components were mounted was mounted on the lower frame.

It is preferable that the storage position of the power circuit board in the above configuration is substantially at the center of the lower frame.
The position is not necessarily limited to the central part. With the above configuration, most of the heat generated by the power circuit board is dissipated through the lower frame, and the light guide plate is interposed between the liquid crystal panels. And the transmitted heat is applied without causing a temperature difference to the liquid crystal panel, so that display unevenness on the left and right sides of the screen does not occur.

(2) The lower frame in (1) has a recess for accommodating the power circuit board.

By forming the recess, the thickness of the entire liquid crystal display device can be reduced, the mechanical strength of the lower frame itself can be increased, and the power circuit board can be securely held.

(3) A plastic mold for reinforcement in which a concave portion corresponding to the concave portion of the lower frame is formed on the rear surface of the lower frame in (1).

With this configuration, it is possible to minimize an increase in the thickness of the liquid crystal display device due to the provision of the reinforcing plastic mold.

(4) The common electrode drive circuits in (1), (2) and (3) are separated into two, and arranged on each of two parallel sides of the liquid crystal panel, and drive signals are respectively transmitted from the power circuit board. Was supplied.

With this configuration, the distortion of the drive voltage waveform due to the distance from the common electrode drive circuit installation side is canceled out, and the display unevenness caused by the distortion of the drive voltage waveform is suppressed, and a high quality display is achieved. Obtainable.

The present invention is not limited to the above configuration, and various modifications can be made without departing from the scope of the technical idea of the present invention.

Further objects and configurations of the present invention will be apparent from the following detailed description with reference to the accompanying drawings.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view for explaining the structure of a first embodiment of the liquid crystal display device according to the present invention, and FIG. 2 is a first exploded view of the liquid crystal display device according to the present invention, showing the essential parts of FIG. FIG. 2 is an exploded perspective view for explaining the configuration of the embodiment, wherein 1 is a liquid crystal panel, 2 is a common electrode drive circuit board, 3 is an upper frame, 3a is a claw, 4 is a lower frame, 4a is a recess in the lower frame, and 5 is An intermediate mold case, 5a is a cutout for passing a flexible wiring, 6 is a light guide plate, 7 is a plastic mold, 7a is a concave portion of the plastic mold, 8 is a power circuit board on which heat-generating components are mounted, 9 is a heat-generating component, 10
Is a segment drive circuit board, 11 is a flexible wiring,
11a is a joiner connector, and 12 is a board connector. The linear lamps constituting the backlight are not shown.

In the figure, a segment electrode drive circuit board 10 is attached to two upper and lower parallel sides of the liquid crystal panel 1, and a common electrode drive circuit board 2 is attached to two left and right parallel sides. An intermediate mold case 5 is provided on the back surface of the liquid crystal panel 1, and a light guide plate 6 constituting a backlight is accommodated from below the intermediate mold case 5.

Below the light guide plate 6, a lower frame 4 and a plastic mold 7 installed on the back of the lower frame 4
Is located. The lower frame 4 is made of an aluminum plate, and a concave portion 4a that is convex toward the light guide plate 6 is formed by drawing at the center. The power circuit board 8 is housed inside the recess 4a.

Heat generating components are housed in the power circuit board 8, flexible wirings 11 are drawn out from both sides thereof, and joiner connectors 11a are attached to the ends, respectively, and the common electrodes are connected between * a and * b. It is connected to a board connector 12 on each of the drive circuit boards 2.

FIG. 3 is a schematic diagram for explaining the structure of the first embodiment of the liquid crystal display device according to the present invention, and illustrating the cross-sectional structure along the line AA in FIG. The power circuit board 8 is housed in a concave portion 4a formed in the lower frame 4 from the back side (the plastic mold 7 side) of the lower frame 4. And
The bottom surface of the power circuit board 8 is
Is seated in the recessed portion 7a formed in the recess.

Then, the flexible wiring 11 drawn out from the power circuit board 8 passes through the notch 5a formed in the intermediate mold case 5 to connect to each connector (shown in the figure) of the common electrode drive circuit board 2 installed on the left and right sides of the liquid crystal panel 1. )).

According to the present embodiment configured as described above, heat from the power circuit board is hardly transmitted to the liquid crystal panel,
In addition, the heat dissipated in the lower frame and slightly transmitted to the liquid crystal panel does not change the operation characteristics of the liquid crystal layer, and there is no possibility that display unevenness as in the related art will occur.

Further, the common electrode drive circuit boards are arranged on the left and right sides of the liquid crystal panel, and drive voltages are applied to the common electrodes, for example, every other one from the left and right common electrode drive circuit boards, so that the drive voltage waves are rounded. The resulting display unevenness can be equalized, and a high quality display can be obtained.

Further, the concave portion formed in the lower frame has a function of improving the mechanical strength of the lower frame, and the strength of the entire liquid crystal panel can be further improved by using a plastic mold. Note that this plastic mold is not always necessary, and if desired, only the lower frame can be used.

FIG. 4 is an exploded perspective view for explaining the structure of a liquid crystal display device according to a second embodiment of the present invention, and FIG. 5 is a view for explaining the structure of the liquid crystal display device according to the second embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating a cross-sectional structure along the line A, and the same reference numerals as those in the drawings of the first embodiment correspond to the same parts.

This embodiment is the same as the first embodiment except that the recess 4a formed in the lower frame 4 is a recess opened toward the light guide plate 6. That is, as shown in FIG. 5, the power circuit board 8 is housed in the bottom of the recess 4a of the lower frame 4, and is preferably fixed with an insulating adhesive or the like. In this embodiment, the heat-generating components are directly exposed to the light guide plate 6 side, but most of the heat is transmitted to the lower frame 4 side and dissipated. The other configuration is the same as that of the first embodiment, and the description is omitted.

According to the present embodiment, the heat from the power circuit board is hardly transmitted to the liquid crystal panel, and is dissipated in the lower frame, and the heat slightly transmitted to the liquid crystal panel also changes the operation characteristics of the liquid crystal layer. Therefore, there is no possibility that display unevenness occurs as in the related art.

Further, the common electrode drive circuit boards are arranged on the left and right sides of the liquid crystal panel, and drive voltage is applied from the left and right common electrode drive circuit boards, for example, every other common electrode to the common electrodes, so that the drive voltage waves are rounded. The resulting display unevenness can be equalized, and a high quality display can be obtained.

Further, the concave portion formed in the lower frame has a function of improving the mechanical strength of the lower frame, and the strength of the entire liquid crystal panel can be further improved by using a plastic mold. Note that this plastic mold is not always necessary, and if desired, only the lower frame can be used.

FIG. 6 is a block diagram illustrating a driving system of the liquid crystal display device according to the present invention. 100 is a liquid crystal display device,
101 is a liquid crystal panel, 102 is a common electrode driving circuit (scanning electrode driving circuit, common driver) for simultaneously selecting two lines, and 103 is a common driver 102 for selective scanning.
A segment electrode drive circuit (data driver) 104 for determining a display state on a line, 104 is 8-bit parallel display data D7 to D0, 105 is a data latch clock (CL2) synchronized with the display data 104, and 106 is a line clock CL1. Yes, one line of data is sent in one cycle of the line clock (CL1).

Reference numeral 107 denotes a head line clock (FLM: frame clock).
One cycle of M is one frame period. Reference numeral 108 denotes a display off control signal (DISPOFF). When this signal is "0", the display is stopped. The display data (image signal) and the synchronization signals 104 to 108 are provided from the liquid crystal controller 109.

Reference numerals 115 and 116 denote the liquid crystal panel 101.
And 114 is a power supply circuit for generating liquid crystal drive voltages 115 and 116. Reference numerals 111 and 112 denote external power supply voltages VCC and VEE (GND) on which the liquid crystal driving voltages 115 and 116 are based, and 113 denotes a voltage VC for adjusting the voltage levels of the liquid crystal driving voltages 115 and 116.
When turned on, it is supplied from the display system main body 110. Note that 117 and 118 are orthogonal function W1 and W2 signals generated by the scanning driver 102.

In this drive system, particularly, the electronic components constituting the power supply circuit are heat-generating components, and this portion is mounted on the power circuit board and mounted substantially at the center of the lower frame. Since the specific operation of this drive system is not directly related to the present invention, a detailed description of the operation will be omitted.

In the above embodiment, the passive type, that is, the liquid crystal display device generally called STN has been described. However, the present invention is not limited to this, and the installation position of the power circuit board is not particularly limited. The present invention can be similarly applied to a liquid crystal display device, for example, a TN type active matrix liquid crystal display device.

[0042]

As described above, according to the present invention,
The heat from the power circuit board is less likely to be transmitted to the liquid crystal panel, and is dissipated in the lower frame, and the heat transmitted slightly to the liquid crystal panel does not change the operation characteristics of the liquid crystal layer. There is no danger of display unevenness. Further, the common electrode driving circuit boards are arranged on the left and right sides of the liquid crystal panel, and a driving voltage is applied from the left and right common electrode driving circuit boards to every other common electrode. Unevenness can be equalized, and a display with good quality can be obtained. Further, the concave portion formed in the lower frame has a function of improving the mechanical strength of the lower frame, and the strength of the entire liquid crystal panel can be further improved by using a plastic mold.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view illustrating a configuration of a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is an exploded perspective view illustrating a configuration of a first embodiment of the liquid crystal display device according to the present invention, in which main parts of FIG. 1 are further expanded.

FIG. 3 is a schematic diagram illustrating a cross-sectional structure taken along line AA of FIG. 1 illustrating a configuration of a first embodiment of the liquid crystal display device according to the present invention.

FIG. 4 is an exploded perspective view illustrating a configuration of a second embodiment of the liquid crystal display device according to the present invention.

FIG. 5 is a schematic diagram illustrating a cross-sectional structure taken along line AA of FIG. 4 illustrating a configuration of a second embodiment of the liquid crystal display device according to the present invention.

FIG. 6 is a block diagram illustrating a driving system of the liquid crystal display device according to the present invention.

FIG. 7 is a schematic diagram illustrating a basic configuration of a conventional liquid crystal display device.

FIG. 8 is a cross-sectional view corresponding to a state cut along the line AA of FIG. 7, illustrating a relationship between components of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Common electrode drive circuit board 3 Upper frame 3a Claw 4 Lower frame 4a Lower frame recess 5 Intermediate mold case 5a Notch for passing flexible wiring 6 Light guide plate 7 Plastic mold 7a Plastic mold recess 8 Heating parts Mounted power circuit board 9 Heat generating component 10 Segment drive circuit board 11 Flexible wiring 11a Joiner connector 12 Board connector 13 Linear lamp.

Claims (4)

[Claims] 1. A liquid crystal panel in which one substrate having a common electrode for forming a display pixel and the other substrate having a segment electrode are opposed to each other via a liquid crystal layer, and each of the common electrode and the segment electrode is provided. A common electrode drive circuit board and a segment electrode drive circuit board that apply signals for forming pixels, and a backlight that is installed on the back of the liquid crystal panel and irradiates the liquid crystal panel with illumination light; A metal upper frame disposed above and having an opening in a display area; and a liquid crystal panel, a common electrode driving circuit board, and a segment electrode driving circuit disposed below the backlight and coupled to a periphery of the upper frame. A liquid crystal display device comprising at least a metal lower frame that integrally holds a substrate and a backlight, wherein the common electrode drive circuit base is provided. A liquid crystal display device comprising: a power circuit board on which components including heat-generating components of a plate are mounted; 2. The liquid crystal display device according to claim 1, wherein the lower frame has a recess for accommodating the power circuit board. 3. The liquid crystal display device according to claim 1, wherein a reinforcing plastic mold having a concave portion corresponding to the concave portion of the lower frame is disposed on a rear surface of the lower frame. 4. The liquid crystal panel according to claim 1, wherein said common electrode drive circuit is divided into two, and arranged on each of two parallel sides of said liquid crystal panel to supply drive signals from said power circuit board. The liquid crystal display device according to claim 1.