JP2000066219A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] To provide a high quality image display by preventing display unevenness due to heat generation of a linear lamp. A liquid crystal composition (13) is sealed in a gap between two insulating substrates (1) and (3) each having an electrode for pixel selection formed on an inner surface thereof. A backlight comprising a sealed liquid crystal panel 30 and a linear lamp 38 arranged along at least one side of a light guide plate 37 laminated on the back surface of the liquid crystal panel 30;
A seal portion 1 including an effective area 20 close to one or three linear lamps 38 between two insulating substrates forming a liquid crystal panel 30
The gap d in the vicinity of 9 is made larger than the gaps in the other portions only to compensate for the change in threshold voltage caused by the heat generated by the linear lamp 38.

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 a liquid crystal layer is sealed in a gap between two insulating substrates each having an electrode for pixel selection formed on the inner surface thereof. The present invention relates to a liquid crystal display device provided with a backlight composed of linear lamps arranged along at least one side of a light guide plate laminated on a back surface of a liquid crystal panel sealed with a sealant.

[0002]

2. Description of the Related Art A liquid crystal display device has been widely used as a display device capable of high-definition and color display for a notebook computer or a display monitor.

[0003] The liquid crystal display device includes a simple matrix type using a liquid crystal panel in which a liquid crystal layer is sandwiched between a pair of substrates on which parallel electrodes formed so as to cross each other are formed on each inner surface;
2. Description of the Related Art An active matrix type liquid crystal display device using a liquid crystal display element (hereinafter, also referred to as a liquid crystal panel) having a switching element for selecting a pixel in one of a pair of substrates is known.

An active matrix type liquid crystal display device is
A so-called vertical electric field type liquid crystal display device (generally, a TN type active matrix type) using a liquid crystal panel in which an electrode group for pixel selection is formed on a pair of upper and lower substrates as represented by a twisted nematic (TN) type. A liquid crystal panel in which an electrode group for pixel selection is formed only on one of a pair of upper and lower substrates,
There is a so-called in-plane switching mode liquid crystal display device (generally referred to as an IPS mode liquid crystal display device).

The present invention can be applied to the above-mentioned various liquid crystal display devices. Hereinafter, a simple matrix type liquid crystal display device will be described as an example.

In a conventional simple matrix type liquid crystal display device, a large number of common electrodes are formed on one inner surface and a large number of segment electrodes are formed on the other inner surface, and both substrates are arranged such that these common electrodes and the segment electrodes intersect. A liquid crystal is injected into a gap between the overlapping portions to form a liquid crystal layer, and a seal for bonding the two substrates to an outer periphery of a liquid crystal layer and a pixel area (effective display area) formed at each intersection of the common electrode and the segment electrode. A liquid crystal panel is formed by sealing with a liquid crystal, and a backlight in which a light guide plate and a linear lamp (cold cathode fluorescent lamp: CFL) are arranged along at least one side of the light guide plate on the back surface of the liquid crystal panel is provided. .

[0007] The linear lamps constituting the backlight are not limited to ones arranged close to one side of the light guide plate (one side of the liquid crystal panel), but may be arranged on two opposing sides.

The prior art relating to this type of liquid crystal display device is disclosed, for example, in Japanese Patent Publication No. Sho 51-1.
No. 3666 and the like.

[0009]

When a backlight composed of a light guide plate and a linear lamp is used as an illumination light source for a liquid crystal panel, a portion of the liquid crystal panel close to the linear lamp is heated by the linear lamp. (In general, the threshold voltage changes), so-called display unevenness (brightness unevenness in monochrome display, and color unevenness in color display) occurs, which causes a problem of deteriorating display quality.

An object of the present invention is to provide a high-quality liquid crystal display device which prevents display unevenness due to the above-mentioned linear lamp heat generation.

[0011]

In order to achieve the above object, the present invention provides a sealing portion including an effective area of a liquid crystal panel on which a linear lamp constituting a backlight installed on the back of the liquid crystal panel is installed. A gap (cell gap) between two insulating substrates constituting the liquid crystal panel in the vicinity is made larger than gaps in other portions so as to compensate for a threshold change caused by heat generation of the linear lamp. I do.

That is, a typical configuration of the present invention is described in the following (1) and (2).

(1) A liquid crystal panel in which a liquid crystal composition is sealed in a gap between two insulating substrates each having an electrode for selecting a pixel formed on an inner surface thereof, and a seal around an effective display area is sealed with a sealant. And a backlight comprising a linear lamp disposed along at least one side of a light guide plate laminated on the back surface of the liquid crystal panel, wherein the line between two insulating substrates constituting the liquid crystal panel is provided. The gap in the vicinity of the seal portion including the effective area close to the linear lamp is made larger than the gap in the other portion to such an extent as to compensate for a change in threshold voltage due to heat generation of the linear lamp.

With this configuration, the change in the threshold voltage due to the heat generated by the linear lamp on the side of the effective display area of the liquid crystal panel on the side where the linear lamp is installed is reduced, and the change is caused by the heat generation. Display unevenness is suppressed.

(2) In (1), the gap in the vicinity of the seal portion including the effective area close to the linear lamp is made larger by 1.6% to 8% than the gaps in other portions.

The temperature rise on the side of the liquid crystal panel on the side where the linear lamp is installed is 5 to 15 ° C. at present, and in the current liquid crystal, the decrease in the threshold voltage corresponding to this temperature rise is 10 mV.
１００100 mV. The range of the gap corresponding to the decrease in the threshold voltage is 0.05 μm to 0.5 μm. However, in the present manufacturing accuracy of the liquid crystal display device, since the entire surface has a dispersion of about 0.05 μm to 0.1 μm, the range of the gap that can eliminate the heat unevenness is 0.1 μm to 0.5 μm.
μm. This value corresponds to approximately 1.6% to 8% when the gap (cell gap) between the two glass substrates 1 and 3 is 6.2 μm.

By making the gap in the vicinity of the seal portion including the effective area larger than the gaps in the other portions at the above-described ratio, display unevenness due to a rise in temperature can be suppressed.

It should be noted that the present invention is not limited to the simple matrix type liquid crystal display device described in the following embodiments, and that various modifications can be made without departing from the technical idea of the present invention. Needless to say.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to embodiments applied to a simple matrix type liquid crystal display device.

FIG. 1 is a schematic diagram for explaining the arrangement of a liquid crystal panel and a linear lamp in a simple matrix type liquid crystal display device to which the present invention is applied, and FIG. 2 is a sectional view taken along the line AA 'in FIG. . The liquid crystal panel 30 is formed by laminating the common side glass substrate 1 and the segment side glass substrate 3, and a black matrix made of an opaque metal such as chrome or an organic material mixed with a black pigment or the like on the inner surface of the common side glass substrate 1. A color filter 18 of three colors defined by 17 is formed, and the color filter is covered with an overcoat film 16. The black matrix 17 is formed so as to surround one pixel of the color filter 18.

The overcoat film 16 of an acrylic resin or the like has a function of making the uneven upper surfaces of the black matrix 17 and the color filter 18 smooth. On the overcoat film 16, a transparent electrode 9a made of a tin alloy or the like serving as a common electrode and an alignment film 14a are sequentially formed.

On the inner surface of the segment side glass substrate 3, a transparent electrode 9b to be the segment electrode 4 is formed. The transparent electrode 9b is made of the same material as that of the transparent electrode 9a described above.
It is formed so as to extend from the seal portion to be bonded and bonded to the outside to form a segment terminal 4. An alignment film 14b is formed on the transparent electrode 9b via an insulating film 15.

The two glass substrates 1 and 3 are bonded and adhered to an adhesive made of epoxy resin or the like with a sealant 10 mixed with a seal spacer 11 made of silica spheres or fibers. In the space formed between the alignment films 14a and 14b, a display spacer 12 preferably made of a polymer sphere is scattered.
The liquid crystal composition 13 is sealed in the gap defined by 2 to form a liquid crystal layer. The liquid crystal composition is injected from an injection port in which a part of the sealant is cut, and after the injection, the injection port is sealed with a sealant 6.

Surface of common-side glass substrate 1 (display surface side)
Is provided with a polarizing plate 5 so that only light of a specific polarization line of the light transmitted through the liquid crystal layer is allowed to pass therethrough.
The gap between the two glass substrates 1 and 3 is indicated by d. In some cases, a phase difference plate may be interposed below the polarizing plate 5.
In some cases, a polarizing plate may be attached to the back surface of the segment-side glass substrate, but is not shown.

On the back side of the liquid crystal panel thus constructed, a backlight comprising a linear lamp 38 of a cold cathode fluorescent tube (CFL) arranged along at least one side of the light guide plate 37 is installed.

The heat generated from the linear lamp 38 affects the side of the liquid crystal panel on which the linear lamp 38 is installed. As shown in FIG. 1, this heat causes uneven heat, that is, display unevenness in the seal portion 19 and the vicinity 7 of the seal portion in the effective display area 20. The threshold voltage of the liquid crystal composition changes due to heat.

FIG. 3 is an explanatory diagram showing the relationship between the threshold voltage of the liquid crystal composition and the temperature in terms of the difference between the side where the linear lamp is provided on the liquid crystal panel and other portions. Note that the characteristics shown in this figure are such that the gap (cell gap) between the two glass substrates 1 and 3 is 6.2 μm, and the liquid crystal composition is composed of three typical materials currently used ( Liquid crystal A, liquid crystal B, liquid crystal C)
It is the result of having examined about.

In the operation state of the liquid crystal display device, the temperature near the seal portion 7, that is, near the side where the linear lamp is installed is 35 ° C.
The temperature is 40 ° C. and 25 ° C. to 30 ° C. in other portions. Accordingly, the temperature difference between the vicinity 7 of the seal portion and other portions is 5 ° C. to 15 ° C. Each of these liquid crystals A, B,
Looking at the change in the threshold voltage corresponding to the minimum value and the maximum value of the temperature difference for C, the liquid crystal A shows that V ₆ → V ₄ and the liquid crystal B
In _{V 5 → V 2, V 3} → V 1 becomes the liquid crystal C, 10 m
V to 100 mV.

FIG. 4 is an explanatory diagram showing the relationship between the threshold voltage of the liquid crystal composition and the cell gap at a constant temperature. From this figure, when the cell gap (gap between two glass substrates) is calculated for a change in the threshold voltage from 10 mV to 100 mV, the difference is in the range of 0.05 μm to 0.5 μm.

However, since the current manufacturing accuracy varies from about 0.05 μm to 0.1 μm over the entire surface, the range of the cell gap that can eliminate the heat unevenness is from 0.1 μm to 0.5 μm.
m.

This value corresponds to approximately 1.6% to 8% when the gap (cell gap) between the two glass substrates 1 and 3 is 6.2 μm.

Based on this result, in the liquid crystal panel constituting the liquid crystal display device in which one linear lamp 38 is provided on one side of the liquid crystal panel as shown in FIG. The cell gap on the side (range 7 in FIG. 1 = near the seal portion 19 and the seal portion in the effective display area 20 in FIG. 2) is increased by about 1.6% to 8% with respect to other portions.

The expansion of the cell gap described above depends on the diameter or mixing amount of the seal portion spacer, the width of application of the sealant, the thickness of the color filter (which may include a black matrix), and the thickness of the display portion spacer scattered over the effective display area. It can be realized by means for adjusting the diameter, distribution, and other factors that can be considered in the current technology between the two glass substrates.

According to this embodiment, it is possible to obtain a liquid crystal display device capable of displaying a high quality image without display unevenness over the entire effective display area.

FIG. 5 is an exploded perspective view for explaining an example of the overall configuration of the liquid crystal display device according to the present invention. 40 is an upper frame, 30 is a liquid crystal panel, 31 is a common electrode drive / power supply board, 32a and 32b are segment drive boards, 33 is a tape carrier package connecting the common drive electrode / power supply board 31 and the common terminal of the liquid crystal panel 30 ( TCP), 3
Reference numerals 4a and 34b denote TCPs connecting the segment drive substrates 32a and 32b to the segment terminals 4 (FIGS. 1 and 2) of the liquid crystal panel 30, 35 denotes a mold (intermediate frame), 36 denotes a prism sheet, 37 denotes a light guide plate, and 38 denotes a light guide plate. Linear lamp, 3
9 is a lamp reflector, and 41 is a lower frame. The polarizing plate attached to the liquid crystal panel 30 is not shown.

The liquid crystal panel 30, the prism sheet 36, and the light guide plate 37 are laminated on the mold 35, sandwiched between the upper frame 40 and the lower frame 41, and fixed using claws or the like.

FIG. 6 is a perspective view for explaining a notebook personal computer which is an example of electronic equipment on which the liquid crystal display device of the present invention is mounted. This notebook computer has a display unit 50 and a main unit 5.
1 are connected by a hinge 55. A liquid crystal display device using the liquid crystal panel 30 according to the present invention is mounted on the display unit 50, and an operation unit such as a keyboard 52 is provided on the main body unit 51. Since the liquid crystal panel 30 is of a simple matrix type, the display unit 50 is provided with a brightness adjuster 53 and a contrast adjuster 54.

FIG. 7 is a block diagram for explaining an example of the display circuit of the notebook type personal computer shown in FIG. Around the liquid crystal panel 30, a driver LSI 61 for driving a common electrode and for driving a segment electrode is mounted. The display signal output from the central processing unit MPU of the main body is converted into a display signal processing LSI 63 and a liquid crystal panel display signal using a RAM, a ROM, etc., and supplied to a driver LSI 61 for driving a common electrode and a segment electrode. You. The driver LSI 61 applies a voltage for pixel selection to the common electrode and the segment electrode of the liquid crystal panel 30 based on a predetermined signal processing procedure, and displays a required image.

[0039]

As described above, according to the present invention,
High-quality image display without unevenness in display over the entire effective display area by compensating for changes in the threshold voltage of the liquid crystal layer due to the heat generated by the linear lamps constituting the backlight by changing the cell gap A liquid crystal display device capable of performing the above can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an arrangement of a liquid crystal panel and a linear lamp in a simple matrix type liquid crystal display device to which the present invention is applied.

FIG. 2 is a sectional view taken along the line A-A 'of FIG.

FIG. 3 is an explanatory diagram showing a relationship between a threshold voltage of a liquid crystal composition and a temperature in a difference between a side where a linear lamp is provided on a liquid crystal panel and other portions.

FIG. 4 is an explanatory diagram of a relationship between a threshold voltage of a liquid crystal composition and a cell gap at a constant temperature.

FIG. 5 is an exploded perspective view illustrating an example of the entire configuration of the liquid crystal display device according to the present invention.

FIG. 6 is a perspective view illustrating a notebook personal computer as an example of an electronic device on which the liquid crystal display device of the present invention is mounted.

7 is a block diagram illustrating an example of a display circuit of the notebook computer illustrated in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 common side glass substrate 2 common terminal 3 segment side glass substrate 4 segment terminal 5 polarizing plate 6 sealant 7 display unevenness generating portion 9a, 9b transparent electrode 10 sealant 11 seal portion spacer 12 display portion spacer 13 liquid crystal composition 14a, 14b Alignment film 15 Insulation film 16 Overcoat film 17 Black matrix 18 Color filter 19 Near seal part 20 Effective display area. 37 light guide plate 38 linear lamp.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 LA07 LA08 LA14 NA09 PA05 QA16 TA12 TA14 TA15 TA18 2H091 FA02Y FA08X FA08Z FA23Z FA41Z FD14 GA08 GA13 LA04 LA12 LA15 LA18

Claims (2)

[Claims] A liquid crystal panel in which a liquid crystal composition is sealed in a gap between two insulating substrates each having an electrode for pixel selection formed on an inner surface thereof, and a seal around an effective display area is sealed with a sealant. A liquid crystal display device provided with a backlight comprising a linear lamp disposed along at least one side of a light guide plate laminated on the back surface of the liquid crystal panel, wherein the linear shape between two insulating substrates constituting the liquid crystal panel is provided. A liquid crystal display device, wherein a gap near the seal portion including the effective area near the lamp is made larger than gaps in other portions only to compensate for a threshold change caused by heat generation of the linear lamp. 2. The apparatus according to claim 1, wherein a gap in the vicinity of said seal portion including said effective area close to said linear lamp is made larger by 1.6% to 8% than gaps in other portions. Liquid crystal display device.