JPH08201779A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display device capable of displaying a high-quality picture without the unevenness of display even when temperature partially rises in a liquid crystal display element by heat from a light source lamp in spite of the device using an edge light system backlight unit. CONSTITUTION: The light source lamp 42 of the backlight unit 40 is arranged to be opposed to the side end face of a light guide plate 41 in the length direction of the scanning electrode 13 of the liquid crystal display element 10 out of the peripheral end faces of the light guide plate 41. A scanning side driving circuit 20 is constituted to have a means for controlling the potential of a scanning signal supplied to each scanning electrode 13 of the display element 10 in accordance with the temperature distribution of the display element 10 whose temperature rises by the heat from the light source lamp 42.

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 having a backlight unit called an edge light system.

[0002]

2. Description of the Related Art As a liquid crystal display device which displays an image using a liquid crystal display element, there is one which uses a backlight unit called an edge light system as an illuminating means for illuminating the liquid crystal display element from its rear side.

The edge-light type backlight unit is composed of a light guide plate which faces the back surface of the liquid crystal display element over at least the entire display area thereof, and a light source lamp which is arranged so as to face a side edge of the light guide plate. There is. A straight tube fluorescent lamp is used as the light source lamp, and a transparent plate made of acrylic resin or the like is used as the light guide plate. The back surface of this light guide plate is normally guided inside the light guide plate. The surface is roughened to reflect the light toward the surface side.

This backlight unit is for making the light from the light source lamp enter the liquid crystal display element through the light guide plate, and the light from the light source lamp enters the light guide plate from its side end face, and the light guide plate is made. The light is guided to the entire area, is reflected by the back surface (roughened surface) of the light guide plate, is emitted to the front surface side, and is incident on the liquid crystal display element.

The edge-light type backlight unit has a merit that the entire display device can be thinned and the entire display area of the liquid crystal display element can be illuminated substantially evenly because of its thin thickness.

The backlight unit includes a light source lamp arranged on one side of the light guide plate, a light source lamp arranged on both sides of the light guide plate, and the like, and is used for a personal computer, a word processor or the like. As a liquid crystal display device having a relatively large screen, a light source plate having light source lamps arranged on both sides thereof is used.

[0007]

However, in the liquid crystal display device using the edge light type backlight unit, the intensity of light incident on the liquid crystal display element from the backlight unit is substantially uniform over the entire display area. However, there is a problem that the displayed image becomes an image with "unevenness" in which the contrast is partially different.

This is because the edge-light type backlight unit has a structure in which the light source lamp is arranged so as to face the side edge of the light guide plate facing the back surface of the liquid crystal display element. The side closer to the light source lamp is partially heated by the heat from the light source lamp, and the value of Δn · d (product of refractive index anisotropy Δn of liquid crystal and layer thickness d of liquid crystal layer) in that region changes. Is.

That is, in general, the liquid crystal display element is designed so that the liquid crystal layer thickness d is substantially uniform over the entire display area in order to eliminate variations in its electro-optical characteristics. Since Δn changes with temperature and becomes smaller as the temperature rises, the value of Δn · d becomes smaller when the temperature of the liquid crystal display element rises.

Since the optical characteristic (retardation) of the liquid crystal display element is determined by the value of Δnd, when the temperature of the liquid crystal display element is partially raised by the heat from the light source lamp as described above, The optical characteristics have changed,
Display unevenness occurs.

Although the present invention uses the edge light type backlight unit, even if the liquid crystal display element is partially heated by the heat from the light source lamp,
It is an object of the present invention to provide a liquid crystal display device capable of displaying a high quality image without display unevenness.

[0012]

In a liquid crystal display device of the present invention, a plurality of scanning electrodes are provided on one of a pair of substrates facing each other across a liquid crystal layer, and a plurality of signal electrodes are provided on the other substrate. A simple matrix type liquid crystal display element, a scanning side drive circuit for sequentially supplying a scanning signal to each scanning electrode of the liquid crystal display element, a signal side drive circuit for supplying a data signal to each signal electrode of the liquid crystal display element, An edge light type backlight unit including a light guide plate facing a back surface of the liquid crystal display element and a light source lamp arranged to face a side edge of the light guide plate is provided, and the light source lamp includes the light guide plate. Of the peripheral end faces of the liquid crystal display element, the scanning side driving circuit supplies the scanning electrodes of the liquid crystal display element to the scanning electrode of the liquid crystal display element. The potential of No. scanning signal, and is characterized in that it comprises means for controlling in accordance with the temperature distribution of the liquid crystal display element to increase the temperature by the heat from the light source lamp.

In the present invention, the scanning side drive circuit supplies a scanning signal having a lower absolute value than a scanning signal supplied to the scanning electrodes in other regions to the scanning electrodes in the temperature rising region of the liquid crystal display element. Anything can be used.

[0014]

In the liquid crystal display device of the present invention, the backlight unit is arranged such that the light source lamp is arranged so as to face the side end surface of the light guide plate along the length direction of the scanning electrode of the liquid crystal display element. Therefore, the temperature distribution of the liquid crystal display element, which is heated by the heat from the light source lamp, has a temperature gradient in the arrangement direction of the scanning electrodes.

Also in this liquid crystal display device, when the liquid crystal display element is partially heated by the heat from the light source lamp, the value of Δn · d in the temperature rising region becomes small,
Accordingly, if the voltage applied between the electrodes (between the scanning electrode and the signal electrode) in the temperature rising region is reduced, Δn ·
The contrast of the display in the temperature rising region where the value of d is small is almost the same as that of the other regions.

Therefore, the potential of the scanning signal supplied from the scanning side drive circuit to each scanning electrode of the liquid crystal display element is controlled according to the temperature distribution of the liquid crystal display element, and the scanning electrode in the temperature rising area is scanned in another area. If a scanning signal having an electric potential whose absolute value is lower than the electric potential of the scanning signal supplied to the electrodes is supplied, the display contrast can be made substantially equal over the entire display area, and a high-quality image without display unevenness can be displayed.

Moreover, in the present invention, since the voltage applied between the electrodes in the temperature rising region is changed by controlling the potential of the scanning signal supplied to the scanning electrodes, the data signal supplied to the signal electrodes is changed. It is possible to easily control the potential of the signal as compared with the case where the potential of is controlled according to the temperature rise of the liquid crystal display element.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a liquid crystal display device. This liquid crystal display device is a simple matrix type liquid crystal display element 10.
A scanning side drive circuit 20 and a signal side drive circuit 30 for driving the liquid crystal display element 10, and a backlight unit 40 arranged on the back side of the liquid crystal display element 10.
It consists of

The above-mentioned simple matrix type liquid crystal display element 1
0 is a pair of transparent substrates (for example, glass substrates) 11 and 12 facing each other across the liquid crystal layer, and a plurality of scanning electrodes 13 are parallel to each other on the inner surface of one substrate (lower substrate in the figure) 11. And a plurality of signal electrodes 14 are provided in parallel to each other on the inner surface of the other substrate (upper substrate in the drawing) 12 so as to be orthogonal to the scanning electrodes 13. Are each formed of a transparent conductive film made of ITO or the like.

Although not shown in FIG. 1, the electrodes 13 and 14 are formed on the inner surfaces of the pair of substrates 11 and 12, respectively.
Is provided with an alignment film (not shown) made of polyimide or the like, and the alignment film is subjected to an alignment treatment by rubbing.

The pair of substrates 11 and 12 are bonded to each other via a frame-shaped sealing material 15.
A liquid crystal (not shown) is enclosed in a region surrounded by the seal material 15 between the first and the second portions.

The liquid crystal display element 10 is of a TN mode or an STN mode, and the number of molecules of liquid crystal sealed between the substrates 11 and 12 is approximately 9 between the substrates 11 and 12.
0 ° (for TN mode) or 180 ° to 270 °
The twist arrangement is performed at a twist angle (in the STN mode), and polarizing plates (not shown) are provided on the outer surfaces of both substrates 11 and 12, respectively.

The scanning side driving circuit 20 supplies a scanning signal to each scanning electrode 13 of the liquid crystal display element 10 in sequence, and the signal side driving circuit 30 outputs image data to each signal electrode 14 of the liquid crystal display element 10. The scanning side drive circuit 20 is a circuit for supplying a corresponding data signal.
The signal side driving circuit 30 is connected to the terminal portions of the signal electrodes 14.

The scanning side driving circuit 20 and the signal side driving circuit 30 are each one or a plurality of LSIs.
The LSI is composed of a liquid crystal display element 10
It is provided on a wiring board connected to the above or is attached to both boards 11 and 12 of the liquid crystal display element 10.

The back light unit 40 is of an edge light type, and the back light unit 40 faces the back surface of the liquid crystal display element 10 at least over the entire display area (liquid crystal enclosing area). 41 and a pair of light source lamps 42 arranged to face both end surfaces of the light guide plate 41.

The backlight unit 40 makes light from the light source lamp 42 incident on the liquid crystal display element 10 through the light guide plate 41, and the light from the light source lamp 42 enters the light guide plate 41 from both side edges thereof. The light enters, is guided throughout the light guide plate 41, and is reflected by the back surface of the light guide plate to be emitted to the front surface side.

The light source lamp 42 is a straight tubular fluorescent lamp having a length that extends over the entire width of the light guide plate 41, and the light guide plate 4 is used.
Reference numeral 1 denotes a transparent plate made of acrylic resin or the like. The back surface of the light guide plate 41 is roughened to reflect light guided through the light guide plate (light from the light source lamp 42) toward the front surface side. Has been done.

In this liquid crystal display device, the pair of light source lamps 42 of the backlight unit 40 are respectively arranged on the liquid crystal display element 1 of the peripheral end face of the light guide plate 41.
It is arranged so as to face the side end surface of the scanning electrode 13 of 0 along the length direction.

By the way, since the liquid crystal display device uses the edge light type backlight unit 40, the liquid crystal display element 10 is partially heated by the heat from the light source lamp 42 of the backlight unit 40, and The value of Δn · d in the temperature rising region changes.

In this case, in the above liquid crystal display device, the light source lamp 42 of the backlight unit 40 is opposed to the side end surface of the liquid crystal display element 10 along the length direction of the peripheral end surface of the light guide plate 41. Liquid crystal display element 10 that is heated up by the heat from the light source lamp 42
Temperature distribution of the scanning electrode 13 (scanning electrode 13
The distribution has a temperature gradient in the direction orthogonal to the length direction of.

The temperature in the temperature rising region of the liquid crystal display element 10 gradually rises after the light source lamp 42 is turned on, but is stabilized in about 20 minutes after the light source lamp 42 is turned on.
FIG. 4 is a temperature distribution diagram when the temperature rise of the liquid crystal display element 10 is stabilized. Here, the liquid crystal display element 10 has 240 scanning electrodes and one of the light source lamps 42 of the backlight unit 40. To the electrode (No
1 scanning electrode) 13 and the other light source lamp 4
2 shows the temperature distribution when the distance from 2 to the electrode (scan electrode of No 240) 13 at the other end of the scan electrode group is about 20 mm.

As shown in FIG. 4, the temperature of the liquid crystal display element 10 at the time of stabilization is counted from both ends of the scan electrode group, and the first electrode (No 1 scan electrode and No 1 scan electrode and No 1 scan electrode) is counted.
240 corresponding to the scanning electrode) 13 (light source lamp 4
2 to about 20 mm) at about 40 ° C, 18th piece (No
18 and the part corresponding to the No. 223 scanning electrode (about 25 mm from the light source lamp 42) is about 35 ° C., and the part corresponding to the 34th scanning electrode (No. 34 and No 207 scanning electrode) (about 30 mm from the light source lamp 42) Part) about 30 ℃
Then, the temperature gradually decreases from both ends of the scan electrode group toward the center, and the temperature corresponding to the 68th (No 68 and No 173 scan electrodes) (the distance from the light source lamp 42 is about 40 mm or more) is almost normal temperature ( About 25 ° C).

When the temperature of the liquid crystal display element 10 rises in such a temperature distribution, the temperature rises in the liquid crystal display element 10, that is, in the area where the temperature from the light source lamp 42 becomes higher than room temperature (25 ° C.). The value of Δn · d of each part becomes smaller according to the temperature of the part, and therefore the driving voltage (applied voltage to the liquid crystal layer) Vop at which sufficient contrast (hereinafter referred to as maximum contrast) is obtained changes with temperature. To do.

FIG. 5 shows the relationship between the driving voltage Vop and the temperature at which the maximum contrast in the liquid crystal display element 10 is obtained. In the TN or STN mode liquid crystal display device 10, the maximum contrast increases as the temperature rises. The driving voltage Vop that obtains the voltage decreases.

The liquid crystal display element 1 used in this example
As shown in FIG. 5, Vop of 0 is Vop = 2 at room temperature (25 ° C.).
Vop = 21.5v at 1.9v and 30 ° C, Vop = at 35 ° C
Vop = 20.8v at 21.1v and 40 ° C.

Therefore, in this liquid crystal display device, the scanning side drive circuit 20 is connected to each scanning electrode 1 of the liquid crystal display element 10.
3 is provided with a means for controlling the potential of the scanning signal supplied to the liquid crystal display element 3 in accordance with the temperature distribution of the liquid crystal display element 10, so that the display contrast of the liquid crystal display element 10 is substantially equal over the entire display area.

FIG. 2 shows the configuration of the scanning side drive circuit 20. The scanning side drive circuit 20 is a liquid crystal display element 1.
0 according to the predicted heating temperature of the scanning signal forming unit 21 that creates the waveform of the scanning signal supplied to each scanning electrode 13 and the portion corresponding to each scanning electrode 13 of the liquid crystal display element 10 due to the heat from the light source lamp 42. ROM 22 storing the corrected applied potential data for each scan electrode 13 and D / A converter 23
And an amplifier 24 and a control unit 25.

In the ROM 22, each scanning electrode 1 corrected according to the predicted temperature rise temperature of the portion corresponding to each scanning electrode 13 of the liquid crystal display element 10 due to the heat from the light source lamp 42.
The applied potential data for every 3 is stored.

The applied potential data is a potential such that the voltage applied between each scanning electrode 13 and the signal electrode 14 becomes the driving voltage Vop for obtaining the maximum contrast, and the number of scanning electrodes is 240. As described above, the liquid crystal display element 10 has 1 to 68 counted from both ends of the scan electrode group.
The area corresponding to the first scanning electrode 13 is approximately 40 ° C to 25 ° C.
In this embodiment, the temperature rising region of the liquid crystal display element 10 is set to a region corresponding to the 1st to 70th scan electrodes 13 counted from both ends of the scan electrode group with a slight margin. Considering this, the potential data applied to each scan electrode 13 in this temperature rising region is counted from other regions, that is, from both ends of the scan electrode group, and the 71 or more scan electrodes (No 71
.About.No. 170 electrode) 13 is set to be lower than the applied potential data for each scan electrode in the region corresponding to No.

The potential data applied to each scan electrode 13 in the temperature rising region is obtained in other regions, that is, No 71 to No 17.
It is a value obtained by multiplying the applied potential data of each scan electrode of 0 to each scan electrode 13 by α under the condition of α ≦ 1.0. In this embodiment, when the electrode number of the scan electrode 13 is n, the correction coefficient is The applied potential data for each scan electrode 13 in the temperature rising region is set so that α satisfies the following empirical formula α = 1-[(71-n) / 70] ² × 0.1.

The value of the correction coefficient α is, for example, α = 0.9 when n = 1 and α = 1.0 when n = 70,
Therefore, counting from both ends of the scan electrode group,
70th scan electrode, that is, No 1 to No 70 and No 1
The applied potential data for the scan electrodes 13 of Nos. 71 to 240 is 0.9 times to 1.0 times the applied potential data for the scan electrodes (No 71 to No 170 electrodes) 13 in other regions.
It is a double range.

The scanning side driving circuit 20 selects the scanning electrode 13 of the potential applied to each scanning electrode 13 from the ROM 22 in accordance with an instruction from the control section 25 in each selection period of each scanning electrode 13 of the liquid crystal display element 10. To the D / A converter 23, and the analog signal output from the D / A converter 23 is amplified by the amplifier 24 at a predetermined amplification rate according to the data, and the scanning signal forming unit 21
Is input to the scanning signal forming unit 21 to generate a scanning signal having a potential corresponding to the amplified signal, and the scanning signal is supplied to the selective scanning electrode 13, and the scanning signal forming unit 21 generates the scanning signal. The scanning signal is a signal in which the absolute value of the potential of each scanning electrode 13 in the selection period corresponds to the applied potential data from the ROM 22 and the positive / negative is inverted every frame.

On the other hand, although the circuit structure of the signal side drive circuit 30 is not shown, each signal electrode 1 of the liquid crystal display element 10 is synchronized with each scanning electrode 13 selection period.
4 is supplied with a data signal having a potential (absolute value) corresponding to the image data, and the data signal supplied from the signal side drive circuit 30 to each of the signal electrodes 14 is positive / negative for each frame. Is the inverted signal.

FIG. 3 shows the waveform of the scanning signal supplied from the scanning side driving circuit 20 to each scanning electrode 13 and the signal side driving circuit 30 to each signal electrode 14 after the temperature of the liquid crystal display element is stabilized. It is a figure which shows the waveform of the supplied data signal and the voltage applied between the scanning electrode 13 and the signal electrode 14, and is supplied to the scanning electrodes 13 of No1, No18, No71 here. The scan signal, the data signal supplied to the first signal electrode 14, and the No 1 and No 1
8 shows the voltage applied between the No. 71 scan electrode 13 and the first signal electrode 14.

In FIG. 3, Tf is one frame period and t
1, t18, t71 are selection periods of the scan electrodes 13 of No 1, No 18, and No 71, and Vc1, Vc18, and Vc71 are No.
1, No 18 and No 68 scan signals supplied to the scan electrodes 13, Vs1 is a data signal supplied to the signal electrodes 14,
V (c1-s1) is No 1 scan electrode 13 and the signal electrode 1
The voltage applied between V4 and V (c18-s1) is No 18
The voltage applied between the scan electrode 13 of No. 71 and the signal electrode 14, V (c71-s1) is the voltage applied between the scan electrode 13 of No 71 and the signal electrode 14.

In each scanning signal, data signal and inter-electrode voltage, 0 indicates the reference potential. The data signal supplied to the signal electrode 14 is either the ON signal or the OFF signal shown in FIG. 3, and the inter-electrode voltage is the voltage when the ON data signal is supplied.

As shown in FIG. 3, the liquid crystal display element 10 is supplied to the scan electrode 13 of No 71 in a region corresponding to each scan electrode 13 which is not affected by heat from the light source lamp 42. The potential (absolute value) of the scanning signal Vc71 is, for example, 20.2v. In addition, 71 or more scanning electrodes (No 71 to No) counted from both ends of the scanning electrode group, respectively.
The area corresponding to the electrode 170 is a light source lamp 42.
Since it is a region that is not affected by the heat from the above, the potential (absolute value) of the scanning signal supplied to all the scanning electrodes 13 in this region may be the same as that of the scanning signal Vc71.

On the other hand, the scanning electrodes 13 of No. 1 and No. 18 in the area heated by the heat from the light source lamp 42.
Potential of scanning signals Vc1 and Vc18 supplied to (absolute value)
Is, for example, Vc1 is 17.2v and Vc18 is 18.2v, and these scanning signals Vc1 and Vc18 are signals whose absolute values are lower than the potential of the scanning signal Vc71 supplied to the scanning electrode 13 of No 71.

Although not shown in FIG. 3, No 1 to No 70 and No 171 to No 240 in the temperature rising region are included.
The scan signals supplied to the scan electrodes 13 of No 70 and No 171 among the scan electrodes 13 of No. 71 are the scan signals supplied to the scan electrodes (electrodes of No 71 to No 170) 13 (No 71 Signal which is almost the same as the potential of the scan signal Vc71 supplied to the scan electrode 13 of No. 70, and the absolute value of the potential supplied to each scan electrode 13 in the temperature rising region is No 70, No 69 , No 68, ..., No 171, No 172, No 173 ..., in that order, and the absolute value of the scanning signal supplied to the scanning electrodes 13 of No. 1 and No. 240 closest to the light source lamp 42 is the lowest.

Further, in this embodiment, the potential of the data signal Vs1 supplied to the signal electrode 14 (potential with respect to the reference potential 0) is set to O during the frame period Tf for supplying the positive scanning signal.
N potential = -1.86v, OFF potential = 1.86v, ON potential = 1.V during the frame period Tf for supplying a negative scanning signal.
86v, OFF potential = -1.86v.

Between the selected scan electrode 13 and the signal electrode 14 of the liquid crystal display element 10, a potential difference between the scan signal supplied to the scan electrode 13 and the data signal supplied to the signal electrode 14 is obtained. However, as described above, the scan signal supplied to the scan electrodes (electrodes No 1 to No 70 and No 171 to No 240) 13 in the temperature rising region is supplied to the scan electrodes in other regions as described above. (No 71 to No 1
If the absolute value is lower than that of the scanning signal supplied to the electrode 70, the voltage having a lower absolute value is applied between the electrodes in the temperature rising region than between the electrodes in the other regions.

This is applied to the inter-electrode voltage V (c1−
s1), V (c18-s1), V (c71-s1), V (c1-s1) is about 18.9v, V (c18-s1) is about 19.9v, V (c71-s1) Is about 21.9v. The inter-electrode voltage corresponds to the potential of the scanning signal supplied to each scanning electrode 13, and becomes lower in a region closer to the light source lamp 42, that is, in a region where the temperature rise is higher.

As shown in FIG. 5, the driving voltage Vop at which the maximum contrast of the liquid crystal display element 10 used in this embodiment is obtained is Vop = 21.9 at room temperature (25 ° C.).
V, Vop = 21.5 at 30 ° C., Vop = 21.
Vop = 20.8v at 1v and 40 ° C. Further, the temperature distribution of the liquid crystal display element 10 at the time when the temperature is stabilized is shown in FIG.
As shown in, scan electrodes 13 of No 71 to No 170
At a portion (a portion to which an inter-electrode voltage V (c71-s1) is applied) corresponding to the above, the scanning electrode 1 of No 18 and No 223 at about 25 ° C.
The portion corresponding to No. 3 (the portion to which the inter-electrode voltage V (c18-s1) is applied) is about 35 ° C., and the portion corresponding to the scanning electrodes of No 1 and No 240 (the inter-electrode voltage V (c1-s1) is applied). Since the temperature is about 40 ° C. in the (part), the contrast in the temperature rising region and the contrast in other regions are the maximum contrast.

As described above, in the liquid crystal display device, when the liquid crystal display element 10 is partially heated by the heat from the light source lamp 42, the value of Δn · d in the temperature rising region becomes small. Further, the potential of the scanning signal supplied from the scanning side drive circuit 20 to each scanning electrode 13 of the liquid crystal display element 10 is controlled according to the temperature distribution of the liquid crystal display element 10, and the scanning electrode 13 in the temperature rising area is caused to scan another area. By supplying a scanning signal whose absolute value is lower than that of the scanning signal supplied to the electrode 13, the display contrast of the temperature rising region where the value of Δn · d becomes small becomes almost the same as that of other regions. Become.

Therefore, according to the above liquid crystal display device,
Even though the edge light type backlight unit 40 is used, even if the liquid crystal display element 10 is partially heated by heat from the light source lamp 42, a high-quality image without display unevenness is displayed. You can

The temperature rise region of the liquid crystal display element 10 is at room temperature (about 25 ° C.) immediately after the light source lamp 42 is turned on, and the temperature is gradually raised after the light source lamp 42 is turned on. Immediately after the light source lamp 42 is turned on, the drive circuit 20 supplies a scan signal having the same potential as the scan signal supplied to the scan electrodes 13 in the other regions to the scan electrode 13 in the temperature rising region, and to some extent after the light source lamp 42 is turned on. 5% of the time, for example, about half the time until the temperature of the liquid crystal display element is stabilized (about 20 minutes), and
Scan signal with a reduced absolute value (correction coefficient α = 0.9
With the configuration in which 5) is supplied, a high-quality image with substantially no display unevenness can be displayed until the temperature of the light source lamp 42 is stabilized after lighting.

Further, in the above liquid crystal display device, the voltage applied between the electrodes in the temperature rising region of the liquid crystal display element 10 is changed by controlling the potential of the scanning signal supplied to the scanning electrode 13. Compared to the case where the potential of the data signal supplied to the signal electrode 14 is controlled according to the temperature rise of the liquid crystal display element 10, the potential control of the signal can be performed easily.

That is, since the voltage applied between the electrodes of the liquid crystal display element 10 can be controlled also by changing the potential of the data signal supplied to the signal electrode 14, the light source lamp 42 of the backlight unit 40 is connected to the light guide plate 41. Of the peripheral edge of the liquid crystal display element 10 is arranged so as to face a side edge of the liquid crystal display element 10 along the length direction, and the potential of the data signal supplied to each signal electrode 14 of the liquid crystal display element 10 is set to the potential of the liquid crystal display element 10. By controlling according to the temperature distribution, it is possible to display a high-quality image without display unevenness.

However, in the multiplex driving of the liquid crystal display element 10, the driving is performed with the bias b, that is, the ratio (b = Vop / Vs) of the driving voltage Vop at which the maximum contrast is obtained and the potential Vs of the data signal fixed. In order to change the voltage Vop, the potential Vs of the data signal supplied to the signal electrode 14 must be changed, which is very difficult.

Therefore, in the above liquid crystal display device, the light source lamp 42 of the backlight unit 40 is connected to the light guide plate 4.
By arranging the liquid crystal display element 10 so as to face the side edge of the liquid crystal display element 10 along the length direction of the liquid crystal display element 10, the temperature distribution of the liquid crystal display element 10 which is heated by the heat from the light source lamp 42 is scanned. As a distribution having a temperature gradient in the direction in which the electrodes 13 are arranged, a scanning signal V supplied to each scanning electrode 13
The potential of c is controlled according to the temperature distribution of the liquid crystal display element 10. According to this liquid crystal display device, the potentials of the bias b and the data signal Vs are fixed and the potential of the scanning signal is changed. Since it is only necessary to obtain the optimum drive voltage Vop, it is possible to easily control the potential of the signal.

In the above-described embodiment, the backlight unit 40 has the structure in which the pair of light source lamps 42 are arranged so as to face both end surfaces of the light guide plate 41. However, the backlight unit 40 has the same structure as the light guide plate 41. The light source lamp 42 may be arranged to face one side end surface (side end surface along the length direction of the scanning electrode 13 of the liquid crystal display element 10). In that case, scanning of the liquid crystal display element 10 is performed. A predetermined area of the electrode group on the side where the light source lamp 42 is arranged,
In other words, the scanning signal supplied to each scanning electrode 13 in the area heated by the heat from the light source lamp 42 may be a signal having a lower absolute value than the scanning signal supplied to the scanning electrodes 13 in the other areas.

[0062]

According to the liquid crystal display device of the present invention, the light source lamp of the backlight unit is disposed so as to face the side end face of the peripheral end face of the light guide plate along the length direction of the scanning electrode of the liquid crystal display element. A configuration having means for controlling the scanning side drive circuit according to the temperature distribution of the liquid crystal display element, which raises the potential of the scanning signal supplied to each scanning electrode of the liquid crystal display element, by the heat from the light source lamp. Therefore, even though the backlight unit of the edge light system is used, even if the liquid crystal display element is partially heated by the heat from the light source lamp, a high-quality image with no display unevenness can be obtained. Can be displayed.

Moreover, in the present invention, since the voltage applied between the electrodes in the temperature rising region of the liquid crystal display element is changed by controlling the potential of the scanning signal supplied to the scanning electrodes, the voltage is supplied to the signal electrodes. Compared with the case where the potential of the data signal to be controlled is controlled according to the temperature rise of the liquid crystal display element, the potential control of the signal can be easily performed.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of a scanning side drive circuit.

FIG. 3 is a waveform of a scanning signal supplied to a scanning electrode, a waveform of a data signal supplied to a signal electrode, and a voltage applied between the scanning electrode and the signal electrode after the heat generation temperature of the light source lamp is stabilized. And FIG.

FIG. 4 is a temperature distribution diagram at the time when the temperature of the liquid crystal display element is stabilized.

FIG. 5 is a diagram showing the relationship between the drive voltage Vop and the temperature at which the maximum contrast of the liquid crystal display element is obtained.

[Explanation of symbols]

 10 ... Liquid crystal display element 13 ... Scan electrode 14 ... Signal electrode 20 ... Scan side drive circuit 30 ... Signal side drive circuit 40 ... Backlight unit 41 ... Light guide plate 42 ... Light source lamp

Claims (2)

[Claims] 1. A simple matrix type liquid crystal display device having a plurality of scanning electrodes provided on one of a pair of substrates facing each other with a liquid crystal layer interposed therebetween and a plurality of signal electrodes provided on the other substrate, and the liquid crystal display device. A scanning side drive circuit for sequentially supplying a scanning signal to each scanning electrode, a signal side drive circuit for supplying a data signal to each signal electrode of the liquid crystal display element, and a light guide plate facing the back surface of the liquid crystal display element. And a backlight unit including a light source lamp arranged to face a side edge of the light guide plate, wherein the light source lamp is a peripheral end face of the light guide plate.
The scanning side drive circuit is arranged so as to oppose a side end surface along the length direction of the scanning electrodes of the liquid crystal display element, and the scanning side drive circuit sets the potential of the scanning signal supplied to each scanning electrode of the liquid crystal display element to A liquid crystal display device comprising means for controlling according to a temperature distribution of the liquid crystal display element which is heated by heat from a light source lamp. 2. A scanning side driving circuit supplies a scanning signal of a potential whose absolute value is lower than that of a scanning signal supplied to the scanning electrodes of other regions to the scanning electrodes of the temperature rising region of the liquid crystal display element. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.