JPH10133181A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the display quality by suppressing the influence on a display screen due to a lamp cable as a noise source. A light guide disposed below a liquid crystal display element is provided.
Of the two lamp cables LPC1 and LPC2 drawn from both ends of the fluorescent tube LP disposed along one end face of the lamp tube LPC1, the lamp cable LPC1 drawn from the end far from the inverter IV is insulated from the flat strip conductor FC. A flexible cable covered with the objects IN1 and IN2, and the flexible cable is disposed along the fluorescent tube LP between the side wall of the lower case MCA opposite to the light guide GLB and the lamp reflection sheet LS. Was placed.

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 in which a linear light source for supplying light is disposed on a liquid crystal display element in which liquid crystal is sealed between two superposed transparent insulating substrates.

[0002]

2. Description of the Related Art In a liquid crystal display device, for example, two transparent insulating substrates made of glass or the like are laminated with a predetermined gap therebetween so that the surfaces on which a transparent electrode for display and an alignment film and the like are laminated face each other. The two substrates are stuck together by a sealing material provided in a frame shape (b-shape) near the peripheral portion between the two substrates, and a sealing material between the two substrates is provided through a liquid crystal sealing opening provided in a part of the sealing material. A liquid crystal display element (ie, a liquid crystal display panel, LCD: Liquid Crystal Display) comprising a liquid crystal sealed and sealed inside the substrate and a polarizing plate provided outside the two substrates, and a liquid crystal display element. A backlight which is disposed below and supplies light to the liquid crystal display element, a liquid crystal driving circuit board which is disposed outside the outer peripheral portion of the liquid crystal display element, and a frame-shaped body which is a molded product holding these members And this Each member was housed, it is configured to include a metal shield case which is opened display window (frame) and the like.

[0003] The backlight is, for example, a light guide made of a transparent acrylic or other synthetic resin plate for guiding light emitted from the light source to a direction away from the light source and uniformly irradiating the light to the entire liquid crystal display element. A linear light source such as a cold-cathode fluorescent tube disposed near at least one end surface (one side surface) of the light guide along the end surface and in parallel with the end surface; A U-shaped lamp reflection sheet having a white or silver inner surface, a diffusion sheet disposed on the light guide and diffusing light from the light guide, and a light guide disposed under the light guide; And a reflection sheet for reflecting light from the body toward the liquid crystal display element. Such a backlight is called an edge light system.

Light that has entered the light guide from the fluorescent tube guides the light while totally reflecting the light inside the light guide. However, the light is emitted from the upper surface of the light guide by diffuse reflection.
Are provided with a plurality of projections and depressions formed integrally with the bottom surface, and a light diffusion pattern composed of a plurality of dots formed by graining or printing with white ink.

[0005] Such a conventional liquid crystal display device includes:
For example, Japanese Patent Publication No. Sho 60-19474 and Japanese Utility Model Laid-Open No. 4-22
780.

[0006]

FIG. 7 is a schematic plan view of a backlight housed in a lower case of a conventional liquid crystal display device.

The MCA is formed by integral molding, and a lower case (mold case) for storing a backlight, LP
Is a fluorescent tube (cold cathode fluorescent tube) that is the light source of the backlight,
LS is a lamp reflection sheet, GLB is a light guide plate, LPC1,
LPC2 is a lamp cable drawn from both ends of the fluorescent tube LP, and IV is an inverter.

In the conventional liquid crystal display device, as shown in FIG. 7, the fluorescent lamp LP is pulled out from the end of the fluorescent tube LP farther from the inverter IV (or a connector, ie, a lighting circuit) (ie, farther from the inverter IV). Low voltage side lamp cable LPC1 connected to the electrode of the fluorescent tube LP
Was wired so as to surround the periphery of the display screen. In addition,
Although not shown in detail in FIG. 7, the lamp cable LP
C1 and C2 are housed and wired in a housing groove provided integrally with the lower case MCA formed of plastic by integral molding.

For this reason, depending on the type of the lighting circuit of the cold cathode fluorescent tube, a high frequency high voltage is applied to the lamp cable LPC1 wired so as to surround the display screen, and the lamp cable LPC1 causes noise affecting the display. There was a source problem. That is, one side of the transformer secondary side output is connected to ground or the like and used as a reference, and the voltage amplitude (ie, output) is obtained on the other side. When an inverter IV driven by a method of obtaining an amplitude (output) is used, a high frequency high voltage is also applied to the lamp cable LPC1 on the low voltage side, noise from the lamp cable LPC1 jumps into the liquid crystal display element, and ripples (that is, stripes) occur. Display abnormalities), which causes a problem of deteriorating the display quality.

An object of the present invention is to provide a liquid crystal display device capable of suppressing the influence of a lamp cable as a noise source on a display screen and improving display quality.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of wiring a lamp cable as a noise source affecting a display screen as far as possible from a liquid crystal display element in a limited space. It is characterized by doing. That is, according to the present invention, in a liquid crystal display device in which a linear light source for supplying light to a liquid crystal display element is arranged, at least one of two lamp cables drawn from both ends of the linear light source is formed into a flat band shape. Characterized by a flat strip-shaped flexible cable formed by covering the above conductor with an insulator.

Further, in a liquid crystal display device having a linear light source disposed along at least one end face of a light guide disposed below the liquid crystal display element, two lamp cables extending from both ends of the linear light source are provided. Among them, a lamp cable drawn from an end far from a lighting circuit of the linear light source is constituted by a flexible cable in which a flat band-shaped conductor is covered with an insulator.

Further, the flexible cable is arranged along the linear light source.

Further, the flexible cable is arranged along the linear light source between the side wall (or the inner surface of the bottom surface) of the backlight storage case and the lamp reflection sheet of the linear light source. .

As described above, according to the present invention, the lamp cable serving as a noise source affecting the display screen is constituted by the flexible cable, and the backlight storage case is provided on the opposite side of the light guide along the linear light source. By wiring between the side wall of the linear light source and the lamp reflection sheet of the linear light source, wiring can be made as far as possible from the liquid crystal display element, and the length can be shortened without being extended. Therefore, it is possible to reduce ripples (abnormal display of stripes) and suppress the influence of noise on display. Further, the liquid crystal display device can be made compact.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

<< Active matrix liquid crystal display device >> An embodiment in which the present invention is applied to an active matrix type color liquid crystal display device will be described below. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof will be omitted.

<< Overall Configuration of Liquid Crystal Display Module >> FIG.
Is an exploded perspective view of the liquid crystal display module MDL, and the specific configuration of each component is shown in FIGS.

SHD is a shield case (also called a metal frame) made of a metal plate, WD is a display window, INS1
To 3 are insulating sheets, PCB1 to 3 are circuit boards (PCB1
Is a drain side circuit board, PCB2 is a gate side circuit board,
PCB3 is an interface circuit board), JN is a joiner for electrically connecting the circuit boards PCB1 to PCB3, T
CP1 and TCP2 are tape carrier packages, PNL
Is a liquid crystal display panel, GC is a rubber cushion, ILS is a light shielding spacer, PRS is a prism sheet, SPS is a diffusion sheet, GLB is a light guide plate, RFS is a reflection sheet, and MCA is a lower case (mold case) formed by integral molding. , LP is a fluorescent tube, LPC is a lamp cable, and GB is a rubber bush that supports the fluorescent tube LP. The respective members are stacked in an up-down arrangement as shown in the figure to assemble the liquid crystal display module MDL.

The module MDL includes a lower case MCA,
It has two kinds of storage and holding members for the shield case SHD. Insulating sheets INS1-3, circuit boards PCB1-3,
The module MDL is formed by combining a metal shield case SHD containing and fixing the liquid crystal display panel PNL and a lower case MCA containing a backlight BL including a fluorescent tube LP, a light guide plate GLB, a prism sheet PRS, and the like. Assembled.

Hereinafter, each member will be described in detail.

<< Fluorescent tube LP, lamp cable LPC1,
LCP2, Storage in Rubber Bush GB in Lower Case MCA >> FIG. 1 (A) shows the backlight BL (fluorescent tube LP, lamp cable LPC, rubber bush GB, light guide plate GLB) stored in the lower case MCA. FIG. 7B is a top view showing a mounted state, FIG. 7B is a cross-sectional view taken along line BB of FIG. 7A, and FIG. 7C is a cross-sectional view taken along line CC of FIG.

In FIG. 4 showing the inner surface (upper surface) of the lower case MCA, MB is a holding portion of the light guide plate GLB, ML is a storage portion of the fluorescent tube LP, and MG is a storage portion of the rubber bush GB.

The backlight BL is shown in FIGS. 1A to 1C.
As shown in (1), it is stored in a lower case MCA which is a backlight storage case. That is, the rubber bushes GB1, G2 holding the fluorescent tube LP and the lamp cable LPC.
B2 is fitted into the storage portion MG shown in FIG. 4 in which the rubber bushes GB1 and GB2 are formed to fit tightly,
The fluorescent tube LP is stored in the storage section ML without contact with the lower case MCA.

The lighting circuit of the fluorescent tube LP, that is, the lamp cable LPC1 drawn from the end remote from the inverter IV (that is, connected to the electrode of the fluorescent tube LP far from the inverter IV) is shown in FIG. As shown in FIG. 1), the flat belt-shaped conductor FC is made of a flat strip-shaped flexible cable which is covered with insulators IN1 and IN2. The conductor FC is made of, for example, copper, and the insulators IN1 and IN2 are made of, for example, polyimide. Also,
The dimensions of the flexible cable are, for example, a width of 3 to 5 mm,
The thickness is 0.5 to 1 mm.

As shown in FIGS. 1A to 1C, the lamp cable LPC1 composed of the flexible cable is arranged along the fluorescent tube LP on the side opposite to the light guide GLB. Placed in the space of the lower case MCA, that is, the side wall of the lower case MCA and the fluorescent tube LP
And the lamp reflection sheet LS.

Since the fluorescent tube LP tends to be thin and long (for example, the diameter of the fluorescent tube LP is 2.4 mm) as the liquid crystal display module becomes smaller, lighter, and larger in screen, the brightness tends to be inclined and the display becomes easier. Not desirable for quality. Therefore,
In order to avoid this, as described above, the inverter IV of the midpoint ground drive which is not one-side ground is used. However, in this case, the high frequency high voltage is applied also to the low voltage side lamp cable LPC1, and the lamp cable LPC1 is a noise source. And there is a problem that display quality is deteriorated. In order to prevent this, the lamp cable LPC1 which is a noise source
With the flexible cable, and the fluorescent tube L
Lower case MCA on the opposite side of the light guide GLB along P
And the lamp reflection sheet LS, the wiring can be arranged as far as possible from the liquid crystal display panel PNL (see FIG. 3), and the wiring can be shortened without long wiring. Therefore, ripples can be reduced, and the influence of noise on display can be suppressed. Further, since the lamp cable LPC1 is arranged in the space where the fluorescent tube LP is arranged, it is not necessary to provide a groove for accommodating the lamp cable LPC1 in the lower case MCA so as to surround the light guide GLB as in the related art. Thus, the liquid crystal display module MDL (FIG. 3) can be made compact.

The diameter of a conventional lamp cable having a circular cross section is, for example, 1.6 mm. If the diameter of the lamp cable is set to 0.5 to 1 mm, which is the same as the thickness of the flexible cable of the present example, not only will there be a problem in pressure resistance, but it will be necessary to change the coating material from silicon or the like to another high-voltage wire. Wiring becomes difficult because the flexibility of the cable is lost.

As shown in FIG. 1A, the lamp cables LC1 and LC2 near the tip connected to the inverter IV, that is, the lamp cables LC2 and LC2 after the rubber bush GB2 are almost exactly the same as the shapes of the lamp cables LPC1 and LPC2. It is stored in a storage part formed of a groove formed in the lower case MCA along the direction. In addition, the lamp cables LPC1 and LPC2 after the rubber bush GB2 change their directions from the long axis direction of the circuit board PCB2 substantially perpendicularly to the long axis direction of the circuit board PCB2 (see FIGS. 1 and 3), and are provided with mounting holes. M
It is stored in the space between H3 (see FIG. 4) and the circuit board PCB2. An inverter IV is connected to the ends of the lamp cables LPC1 and LP2.
As shown in FIG. 1A, it is housed in an inverter housing MI provided beside the circuit board PCB2. As described above, when the module MD is incorporated in an application product such as a personal computer, the lamp cable LPC does not pass through the outer side of the module, and the inverter IV does not protrude outside the module MD. Lamp cable LPC, rubber bush GB, inverter IV
Can be stored and mounted compactly, the module MDL can be reduced in size and weight, and the manufacturing cost can be reduced.

In the present embodiment, one fluorescent tube LP is provided, but two or more fluorescent tubes LP may be provided, and the fluorescent tube LP may be provided on the short side of the light guide plate GLB.

<< Backlight BL >> FIG. 2 shows a fluorescent tube LP and lamp cables LPC1, LPC of the backlight BL.
FIG. 2 is a top view of main parts of rubber bushes GB1 and GB2.

The backlight BL for supplying light to the display panel PNL includes one cold-cathode fluorescent tube LP, lamp cables LPC1, LPC2 of the fluorescent tube LP, rubber bushes GB1, G for holding the fluorescent tube LP and the lamp cable LPC.
B2, the light guide plate GLB, the diffusion sheet SPS disposed in contact with the entire upper surface of the light guide plate GLB, the reflection sheet RFS disposed in the entire lower surface of the light guide plate GLB, and the prism sheet disposed in contact with the entire upper surface of the diffusion sheet SPS It is composed of PRS.

In the module MDL, the elongated fluorescent tube LP is arranged in a space below the drain-side circuit board PCB1 and the tape carrier package TCP1 mounted on one of the long sides of the liquid crystal display panel PNL.
As a result, the external dimensions of the module MDL can be reduced, so that the module MDL can be reduced in size and weight, and the manufacturing cost can be reduced.

The rubber bushes GB1 and GB2 hold both one cold cathode fluorescent lamp LP and the lamp cables LPC1 and LPC2. That is, the fluorescent tube LP has a hole formed in the rubber bushes GB1 and GB2 (a substantially keyhole shape as shown in FIG. 1B in which a hole having a large inner diameter and a hole having a small diameter are connected).
The lamp cable LPC2, which is inserted and held in the larger hole of the inner diameter of the rubber bush GB2 on the cable outlet side in the same direction as the lamp cable LPC1, is held by being inserted into the hole of the rubber bush GB2 on the cable outlet side. Further, the lamp cable LPC1 is a rubber bush GB1,
It is held between GB2 and the side wall of lower case MCA.

<< Diffusion Sheet SPS >> Diffusion Sheet SPS
Is placed on the light guide plate BLB, diffuses light emitted from the upper surface of the light guide plate GLB, and uniformly irradiates the liquid crystal display panel PNL with light.

<< Prism Sheet PRS >> The prism sheet PRS is placed on the diffusion sheet SPS, and the lower surface is a smooth surface and the upper surface is a prism surface. The prism surface includes, for example, a plurality of V-shaped grooves arranged in a straight line parallel to each other. Prism sheet PRS
Can collect the light diffused from the diffusion sheet SPS over a wide angle range in the normal direction of the prism sheet PRS, thereby improving the brightness of the backlight BL. Therefore, the power consumption of the backlight BL can be reduced, and as a result, the size and weight of the module MDL can be reduced, and the manufacturing cost can be reduced.

<< Reflective Sheet RFS >> Reflective Sheet RFS
Is disposed below the light guide plate GLB, and reflects light emitted from the lower surface of the light guide plate GLB toward the liquid crystal display panel PNL.

<< Lower Case MCA >> FIG. 4 is a top view, upper side view, rear side view, right side view, left side view, and FIG. 5 is a bottom view of the lower case MCA. .

Lower case M formed by molding
CA stands for fluorescent tube LP, lamp cable LPC, light guide plate G
It is a holding member such as LB, that is, a backlight storage case, and is made by integrally molding a single mold with a synthetic resin. For the lower case MCA, see “Shield case SH
As described in detail in "D", since the metal shield case SHD is firmly united by the action of each fixing member and the elastic body, the module MDL can be improved in the vibration shock resistance and the heat shock resistance, and the reliability can be improved. Can be improved.

On the bottom surface of the lower case MCA, a large opening MO occupying at least half the area of the surface is formed in the center portion excluding the peripheral frame portion. Thereby, after assembling the module MDL, the liquid crystal display panel PNL and
Due to the repulsive force of the rubber cushion GC between the light guide plates GLB,
The bottom surface of the lower case MCA can be prevented from bulging due to the force applied vertically to the bottom surface of the lower case MCA from the upper surface to the lower surface, and the maximum thickness can be suppressed.
Therefore, it is not necessary to increase the thickness of the lower case in order to suppress swelling, and the thickness of the lower case can be reduced, so that the module MDL can be reduced in thickness and weight.

MLC is an interface circuit board PC
A heat-generating component B3, in this embodiment, a notch provided in the lower case MCA at a location corresponding to a mounting portion of a power supply circuit (DC-DC converter) formed as a hybrid IC (for connecting a connector CT shown in FIG. 6). Notch). As described above, the heat generating portion on the circuit board PCB3 is connected to the lower case MCA.
By providing the notch without covering with the cover, the heat radiation of the heat generating portion of the interface circuit board PCB3 can be improved. That is, at present, thin film transistor TFT
In order to improve the performance of a liquid crystal display device using the same and to improve the ease of use, it is required to increase the number of gradations and use a single power supply. A circuit for realizing this requires large power consumption, and if the circuit means is to be compactly mounted, the circuit will be mounted at a high density, and heat generation will be a problem. Therefore, the lower case M
By providing the CA with the notched MLC corresponding to the heat-generating portion, the high-density mountability and compactness of the circuit can be improved. In addition, the signal source integrated circuit TCON
Are considered heat-generating components, and the lower case MCA above this may be cut out.

MH1 to MH4 are four mounting holes for mounting the module MD to an application device such as a personal computer. Lower case MC for metal shield case SHD
Mounting holes SH1 to 4 corresponding to the mounting holes MH1 to MH4 of A are formed, and are fixed and mounted on the applied product using screws or the like.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the scope of the invention. . For example, it is needless to say that the present invention is not limited to the active matrix type liquid crystal display device described in the above embodiment, but can be applied to a simple matrix type liquid crystal display device. Further, the structure and wiring method of the lamp cable LPC1 composed of a flexible cable formed by covering the flat band-shaped conductor shown in FIG. 1 with an insulator are merely examples. For example, the lamp cable LPC1 is located below the fluorescent tube LP (ie,
(Between the lamp reflection sheet LS and the inner surface of the bottom surface of the lower case MCA) or the like, along the fluorescent tube LP.

[0043]

As described above, according to the present invention,
The lamp cable, which is a noise source affecting the display screen, is composed of a flexible cable and is wired along the linear light source, so that it can be wired as far as possible from the liquid crystal display element, and it can be shortened without long wiring Therefore, the ripple can be reduced, and the influence of noise on the display can be suppressed. Further, the liquid crystal display device can be made compact.

[Brief description of the drawings]

FIG. 1A is a top view of a light guide plate GLB, a fluorescent tube LP, a rubber bush GB, and the like housed in a lower case MCA;
(B) is a cross-sectional view taken along line BB, and (C) is CC.
It is sectional drawing in a cutting line.

FIG. 2 is a top view of a main part of a fluorescent tube LP, a lamp cable LPC, and a rubber bush GB of a backlight BL.

FIG. 3 is an exploded perspective view of a liquid crystal display module of an active matrix type color liquid crystal display device.

FIG. 4 is a top view, a front side view, a rear side view, a right side view, and a left side view of the lower case MCA.

FIG. 5 is a bottom view of the lower case MCA.

FIG. 6 is a perspective view of a notebook personal computer or a word processor on which a liquid crystal display module MDL is mounted.

FIG. 7 is a schematic plan view of a backlight housed in a lower case of a conventional liquid crystal display device.

[Description of Signs] LPC1, 2 ... Lamp cable, LP ... Fluorescent tube, LS ...
Lamp reflection sheet, MCA: Lower case, GLB: Light guide, IV: Inverter.

Continued on the front page (72) Inventor Norihisa Miyama 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd. (72) Inventor Naoto Kobayashi 3681-Hayano, Mobara-shi, Chiba Hitachi, Ltd.

Claims (4)

[Claims] 1. A liquid crystal display device having a linear light source for supplying light to a liquid crystal display element, wherein at least one of two lamp cables drawn from both ends of the linear light source is connected to a flat band. A liquid crystal display device comprising a flexible cable in which a conductor is covered with an insulator. 2. A liquid crystal display device in which a linear light source is disposed along at least one end face of a light guide disposed below a liquid crystal display element, wherein two lamp cables are drawn from both ends of the linear light source. A liquid crystal display device, wherein a lamp cable drawn from an end far from a lighting circuit of the linear light source is a flexible cable formed by covering a flat band-shaped conductor with an insulator. 3. A liquid crystal display device in which a linear light source is disposed along at least one end face of a light guide disposed below a liquid crystal display element, wherein two lamp cables are drawn from both ends of the linear light source. Among them, the lamp cable drawn from the end far from the lighting circuit of the linear light source is constituted by a flexible cable in which a flat band-shaped conductor is covered with an insulator, and the flexible cable is formed by the linear light source. A liquid crystal display device characterized by being arranged along. 4. The linear cable according to claim 1, wherein the flexible cable is disposed along the linear light source between a side wall of a backlight storage case and a lamp reflection sheet of the linear light source. Or the liquid crystal display device according to 3.