JPH11153795A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high quality display by eliminating ununiformity of distribution of brightness in a display area of a liquid crystal panel. SOLUTION: This liquid crystal display device comprises; at least a liquid crystal panel 20 wherein a 1st substrate and a 2nd substrate are made to face each other with a predetermined space in-between and outer periphery of a display area is bonded with a sealing material to enclose a liquid crystal layer in said space; plural linear lamps 24a, 24b which are installed on the back of this liquid crystal panel 20 and illuminate the liquid crystal panel from behind; and a brightness adjusting device comprising lamp drive current adjusting circuits 26a-26b for independently adjusting each current quantity to be supplied to the plural linear lamps 24a, 24b and controlling a distribution of brightness of the display area of the liquid crystal panel 20 and brightness adjusters 27a-27b.

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 provided with a backlight for illuminating a liquid crystal panel for generating a display image from the back surface, and adjusting the brightness of a display area within the display area. The present invention relates to an enabled liquid crystal display device.

[0002]

2. Description of the Related Art A high-definition and color display liquid crystal display device for a notebook computer or a computer monitor is provided with a light source (so-called backlight) for illuminating a liquid crystal panel from behind.

This type of liquid crystal display device basically forms a so-called liquid crystal panel in which a liquid crystal layer is sandwiched between two substrates at least one of which is made of transparent glass or the like, and is formed on the substrate of the liquid crystal panel. A type in which predetermined voltages are selectively applied to the various electrodes for pixel formation to turn on and off predetermined pixels (simple matrix), the various electrodes and active elements for pixel selection are formed, and the active elements are selected. Accordingly, it is broadly classified into a form (active matrix) for turning on and off a predetermined pixel.

A conventional active matrix type liquid crystal display device employs a so-called vertical electric field method in which an electric field for changing the orientation of a liquid crystal layer is applied between an electrode formed on one substrate and an electrode formed on the other substrate. Was adopted.

In recent years, a so-called in-plane switching (IPS) liquid crystal display device has been realized in which the direction of an electric field applied to a liquid crystal layer is substantially parallel to the substrate surface. As this in-plane switching type liquid crystal display device, a device in which a very wide viewing angle is obtained by using a comb electrode on one of two substrates is known (Japanese Patent Publication No. 63-21907, US Patent No. 4345249).

On the other hand, among the liquid crystal display devices, a simple matrix type liquid crystal display element has a common electrode on one of two substrates and a segment electrode on the other substrate, and has a twist angle of liquid crystal molecules constituting a liquid crystal layer. It has been proposed to increase the number of time divisions by improving the time division drive characteristics by making α larger than 180 degrees and utilizing the birefringence effect. Applied Physics Letter 45, No. 10, 1021 1984 (Applied Physics Lette
r, TJScheffer, J.Nehring: "A new, highly multiplexab
le liquidcrystal display "), and a super twisted birefringence (SBE) liquid crystal display device has been proposed.

A liquid crystal display element having a twisted structure capable of high time-division driving performs lighting by causing a state change of a liquid crystal layer between a non-selection voltage and a selection voltage determined by a bias voltage and a duty ratio. . However, when the twist angle is 180 degrees or more, coloring occurs due to the birefringence effect of the liquid crystal.

In order to avoid this coloring phenomenon, by providing a compensating element in which the liquid crystal layer is twisted in the opposite direction to the liquid crystal layer or a birefringent medium called a retardation plate, the phase difference is compensated and a monochrome display is possible. (Yoshino, Ozaki, "Liquid Crystal and Display Application and Basics", Corona Co., Ltd. 19
94). The halftone display is performed by applying a voltage between the non-selection voltage and the selection voltage.

In order to color a simple matrix type liquid crystal display device of this type, at least three color filters are formed on one of a pair of substrates, and a segment electrode provided for each color filter is provided. By selectively applying a voltage, a required color image can be displayed.

FIG. 7 is a schematic diagram illustrating a configuration example of a liquid crystal display device. This liquid crystal display device has segment driving substrates 21a and 21b and a common driving substrate 22 on the periphery of a liquid crystal panel 20 having a liquid crystal layer sandwiched between two transparent substrates, and a rectangular acrylic resin on the back surface of the liquid crystal panel 20. The backlight includes a transparent light guide plate 23 such as a plate, and linear lamps 24a and 24b and reflectors 29a and 29b arranged along a pair of opposing sides of the light guide plate 23.
This type of backlight is called a side edge type.

FIG. 8 is a schematic diagram illustrating another configuration example of the liquid crystal display device. This liquid crystal display device uses a so-called direct type backlight. The direct-type backlight includes a plurality of linear lamps 24a to 24d arranged on a back surface of a liquid crystal panel 20 similar to that shown in FIG. 7 in a plane parallel to the liquid crystal panel 20, and these linear lamps 24a to 24d.
A reflector 30 having a ridge shape for reflecting the emitted light in the direction of the liquid crystal panel 20, and a diffusion plate 31 interposed between the reflector 30 and the liquid crystal panel 20.

The liquid crystal display device shown in FIGS. 7 and 8 is further provided with a prism sheet, a polarizing plate and other various optical members, but these are not shown here.

[0013]

In the above-described simple matrix type liquid crystal display device, the common electrode driven by the common drive substrate 22 extends from the side of the liquid crystal panel 20 where the common drive substrate 22 is provided to the opposite side thereof. Extending.
The common electrode is formed by patterning a metal foil using a photolithographic etching technique or the like, and the resistance value increases as the distance increases from the side where the common drive substrate 22 is installed in the direction of the opposite side.

Therefore, the common drive voltage decreases as the distance increases from the side where the common drive board 22 is installed toward the opposite side, and the brightness of the screen gradually decreases.

Further, in order to maintain the thickness (cell gap) of a liquid crystal layer between two substrates, a liquid crystal panel constituting a liquid crystal display device is provided with a spacer such as a plastic bead between the two substrates. Distributed.

FIG. 9 is a cross-sectional view of a liquid crystal panel illustrating a spacer for holding a cell gap at a predetermined value.
This liquid crystal panel is shown as an example of the simple matrix type described above, but the same applies to an active matrix type liquid crystal display device.

In FIG. 9, 1 is a first substrate, 2 is a second substrate, 3 is a common electrode, 4 is a segment electrode, 5 is an insulating layer, 6 is a first alignment film, 7 is a second alignment film, and 8 is a second alignment film. Liquid crystal layer, 9
Is a seal, 10 is a spacer, 11 is a first polarizing plate, 12 is a second polarizing plate, and 13 is a retardation plate.

Spacer 1 for maintaining cell gap
0 is supplied to the inner surface of the substrate by dispersing ultrafine particles in a dispersion medium and spraying. Therefore, the distribution density is random and may flow in the liquid crystal layer during the manufacturing process of the liquid crystal panel or during use, and is not necessarily uniformly distributed in the plane of the liquid crystal panel. Absent. As shown in the figure, when the distribution of the spacers becomes non-uniform (the density at the end of the cell gap is large in the figure), the transmittance of the illumination light is shifted, and the brightness of the liquid crystal panel is increased. Changes locally. This causes the display quality to deteriorate.

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 eliminates non-uniform brightness distribution in a display area of a liquid crystal panel and enables high quality display. It is in.

[0020]

SUMMARY OF THE INVENTION The present invention is to solve the problem of uneven brightness distribution in the display area of a liquid crystal panel by adjusting the illumination characteristics of a backlight for illuminating the liquid crystal panel from the back. It is characterized by having each structure of.

(1) The first substrate and the second substrate are opposed to each other at a predetermined gap, and the outer periphery of the display area is bonded with a sealant.
A liquid crystal panel having a liquid crystal layer sealed in the gap; and a backlight having at least a plurality of linear lamps installed on a back surface of the liquid crystal panel and illuminating the liquid crystal panel from the back surface. The brightness distribution of the screen area of the liquid crystal panel is controlled by independently adjusting the amount of current supplied to the lamps.

With this configuration, the brightness in the display area of the liquid crystal panel can be easily adjusted, and even if the brightness distribution is not uniform, it can be easily corrected.

(2) The first substrate and the second substrate are opposed to each other at a predetermined gap, and the outer periphery of the display area is bonded with a sealant.
A liquid crystal panel having a liquid crystal layer sealed in the gap, and a backlight having at least a plurality of linear lamps installed on the back of the liquid crystal panel and illuminating the liquid crystal panel from the back, the backlight comprising: A light guide made of a transparent rectangular plate, and at least one linear lamp arranged along at least two sides of the light guide, and the amount of current supplied to the linear lamp is There is provided a backlight light amount control device which independently adjusts the brightness distribution of the screen area of the liquid crystal panel.

With this configuration, the brightness in the display area of the liquid crystal panel can be easily adjusted by operating the backlight light amount control device, and even if the brightness distribution is non-uniform, it can be easily corrected.

(3) A light reflection pattern is provided on the back surface of the light guide in (1) or (2), and the distribution of the light reflection pattern causes the display area of the liquid crystal panel to vary with the distance from the linear lamp. The brightness is adjusted.

With this configuration, the brightness in the display area of the liquid crystal panel can be set and adjusted to a desired value, and even if the brightness distribution is non-uniform, it can be easily corrected.

(4) The first substrate and the second substrate are opposed to each other at a predetermined gap, and the outer periphery of the display area is bonded with a sealant.
A liquid crystal panel having a liquid crystal layer sealed in the gap, and a backlight having at least a plurality of linear lamps installed on the back of the liquid crystal panel and illuminating the liquid crystal panel from the back, the backlight comprising: A plurality of linear lamps arranged in parallel with the liquid crystal panel, and a reflector installed on the back of the plurality of linear lamps, each independently controlling the amount of current supplied to the linear lamps A backlight light amount control device for adjusting the brightness distribution in the screen area of the liquid crystal panel is provided.

With this configuration, the brightness in the display area of the liquid crystal panel can be easily adjusted by operating the backlight light amount control device, and even if the brightness distribution is non-uniform, it can be easily corrected.

The present invention includes a backlight adjusting device (brightness adjusting device) including a lamp driving current adjusting circuit and a brightness adjuster, so that the brightness of the display area of the liquid crystal panel is shifted. The present invention is not limited to the type of liquid crystal display device to be applied in that the adjustment is performed by adjusting the current value of the linear lamp constituting the backlight.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the illustrated embodiments.

FIG. 1 is a schematic diagram for explaining a first embodiment of a liquid crystal display device according to the present invention.
1a and 21b are segment drive boards, 22 is a common drive board, 23 is a light guide plate, 24a and 24b are linear lamps, 25
Denotes an inverter power supply board, 26a and 26b denote lamp drive current adjustment circuits, 27a and 27b denote brightness adjusters, and 28 denotes a liquid crystal display driver.

In this embodiment, the liquid crystal panel 20 is a so-called double scan type simple matrix type, and a pixel is formed at the intersection of the common electrode and the segment electrode driven by the common drive substrate 22 and the segment drive substrates 21a and 21b. Is configured. The display signal is supplied from a host (not shown) to the liquid crystal display driver 28.

The backlight is composed of the light guide plate 23 and the linear lamp 2.
4a, 24b, and each linear lamp 24a, 24b
Are supplied independently from the inverter power supply board 25. The inverter power supply board 25 is provided with lamp drive current adjustment circuits 26a and 26b and brightness adjusters 27a and 27b. Each of the linear lamps 24a and 24b is configured so that the amount of current supplied can be adjusted independently. ing.

As described above, since the common electrode extends from the common driving substrate 22 side to the opposite side, the brightness of the display area near the linear lamp 24a of the liquid crystal panel 20 is reduced by the linear lamp 24b. Brighter than the display area close to. This difference in brightness can be eliminated to some extent by forming light reflection dots or the like on the back surface of the light guide plate 23 by printing or the like. However, when the size of the liquid crystal panel becomes large, such a means cannot cover the entire area. .

In this embodiment, the brightness of the linear lamp 24a is reduced by the lamp drive current adjusting circuits 26a and 26b and the brightness adjusters 27a and 27b provided on the inverter power supply board 25, and the brightness of the linear lamp 24b is reduced. By increasing, the entire display area can be adjusted to have a uniform brightness.

According to the configuration of this embodiment, uniform brightness can be obtained over the entire display area.

FIG. 2 is a schematic diagram for explaining a second embodiment of the liquid crystal display device according to the present invention, in which only the backlight portion is shown and the configuration on the liquid crystal panel side is the same as that of FIG. .

In this embodiment, the lamps are provided with linear lamps 24a to 24d on the four sides of the light guide plate 23, respectively, and the driving current supplied to each linear lamp is adjusted independently. Circuits 26a, 26b, 2
6c, 26d and brightness adjusters 27a, 27b, 27c,
It was configured so as to be adjusted by 27d.

In this embodiment, since the amounts of light introduced from the four sides of the light guide plate 23 can be adjusted independently of each other, more accurate brightness adjustment becomes possible.

According to the structure of this embodiment, uniform brightness can be obtained over the entire display area.

FIG. 3 is a schematic view for explaining a third embodiment of the liquid crystal display device according to the present invention, in which only a backlight portion is shown, 30 is a ridge-shaped back reflector, and the same reference numerals as those in the above embodiment are the same. It corresponds to the functional part. The configuration on the liquid crystal panel side is the same as that in FIG.

The backlight of this embodiment is of a direct type,
A plurality of linear lamps 24a to 24d on the back of the liquid crystal panel
Are arranged in parallel with the liquid crystal panel, and a ridge-shaped back reflector 30 is provided on the back surface thereof.

In this embodiment, when the liquid crystal panel is of a simple matrix type, the linear lamps are arranged so as to be orthogonal to the common electrode, so that the brightness of the display area of the liquid crystal panel due to the voltage drop of the common electrode is reduced. You can adjust the bias.

Also in this embodiment, the brightness of the display area of the liquid crystal panel can be adjusted uniformly over the entire surface, and a high-quality image display can be obtained.

FIGS. 4 and 5 are explanatory diagrams of examples of the arrangement of the light reflection patterns formed on the back surface of the light guide plate.
Indicates a light reflection pattern.

FIG. 4 shows the case of the liquid crystal display device having linear lamps on two sides shown in FIG. 1, and FIG. 5 shows the case of the liquid crystal display device having linear lamps on four sides shown in FIG. It is a schematic diagram of the backlight showing.

As shown in FIG. 4, in the case of a liquid crystal display device having linear lamps on two sides of a light guide plate, a region near each linear lamp has a high density and is far from the linear lamp. The light reflection pattern is arranged so that the density gradually becomes smaller according to.

This makes it possible to uniformly adjust the brightness of the display area of the liquid crystal panel in combination with the adjustment of the light emission amount of the linear lamp by the lamp drive current adjustment circuit.

FIG. 6 is an external view showing an example of a liquid crystal monitor mounted with a liquid crystal display device according to the present invention.

In this liquid crystal monitor, the liquid crystal display device 51 of any one of the above-described embodiments is mounted on the display unit 50, and the brightness adjustment which constitutes the backlight adjusting device is provided on a part 70 of the frame of the display unit 50. A vessel is provided. Note that 6
0 indicates a monitor base. In this liquid crystal monitor, the brightness of the display screen can be easily adjusted, and a high quality display can be obtained.

[0051]

As described above, according to the present invention,
Since the illumination light of the backlight for illuminating the liquid crystal panel can be arbitrarily adjusted, an image display with uniform brightness over the entire display area can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram illustrating a second embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is a schematic diagram illustrating a third embodiment of the liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram of an example of an arrangement of a light reflection pattern formed on a back surface of a light guide plate.

FIG. 5 is an explanatory diagram of another arrangement example of the light reflection pattern formed on the back surface of the light guide plate.

FIG. 6 is an external view showing an example of a liquid crystal monitor on which the liquid crystal display device according to the present invention is mounted.

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

FIG. 8 is a schematic diagram illustrating another configuration example of the liquid crystal display device.

FIG. 9 is a cross-sectional view of a liquid crystal panel illustrating a spacer for holding a cell gap at a predetermined value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 Common electrode 4 Segment electrode 5 Insulating layer 6 1st alignment film 7 2nd alignment film 8 Liquid crystal layer 9 Seal 9a 2nd wiring electrode 10 Spacer 11 1st polarizing plate 12 2nd polarizing plate 13 Phase difference plate 20 Liquid crystal panel 21a, 21b Segment drive board 22 Common drive board 23 Light guide plate 24a, 24b Linear lamp 25 Inverter power supply board 26 Lamp drive current adjustment circuit 27 Brightness adjuster 28 Liquid crystal driver.

Claims (4)

[Claims] 1. A liquid crystal panel having a first substrate and a second substrate opposed to each other with a predetermined gap, a periphery of a display area bonded with a sealant, and a liquid crystal layer sealed in the gap, and a back surface of the liquid crystal panel. And a liquid crystal display device having a backlight having at least a plurality of linear lamps for illuminating the liquid crystal panel from the back surface thereof, wherein the amount of current supplied to the plurality of linear lamps is adjusted independently. A liquid crystal display device comprising a backlight light amount control device for controlling a brightness distribution of a screen area of a liquid crystal panel. 2. A liquid crystal panel in which a first substrate and a second substrate are opposed to each other with a predetermined gap, a periphery of a display area is bonded with a sealing material, and a liquid crystal layer is sealed in the gap. A liquid crystal display device comprising a backlight having at least a plurality of linear lamps for illuminating the liquid crystal panel from the backside thereof, wherein the backlight comprises: a light guide made of a transparent rectangular plate; And at least one linear lamp respectively arranged along at least two sides of the light body. The brightness of the screen area of the liquid crystal panel is adjusted by independently adjusting the amount of current supplied to the linear lamp. A liquid crystal display device comprising a backlight light amount control device for controlling distribution. 3. The liquid crystal panel according to claim 1, wherein a light reflection pattern is provided on a back surface of the light guide, and a brightness of a display area of the liquid crystal panel is adjusted by a distance from the linear lamp according to a distribution of the light reflection pattern. The liquid crystal display device according to claim 1, wherein: 4. A liquid crystal panel in which a first substrate and a second substrate are opposed to each other with a predetermined gap, a periphery of a display area is bonded with a sealing material, and a liquid crystal layer is sealed in the gap, and a back surface of the liquid crystal panel. A liquid crystal display device comprising a backlight having at least a plurality of linear lamps for illuminating the liquid crystal panel from the back surface thereof, wherein the backlight comprises a plurality of linear lamps arranged in parallel with the liquid crystal panel. A lamp, and a reflector installed on the back of the plurality of linear lamps, and independently controlling an amount of current supplied to the linear lamps to control a brightness distribution of a screen area of the liquid crystal panel. A liquid crystal display device comprising a backlight light amount control device.