JP3489201B2 - Liquid crystal display - Google Patents

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 particular, the present invention relates to a liquid crystal display device including a bright adjustment circuit for setting a bright voltage applied to a liquid crystal display panel.

[0002]

2. Description of the Related Art A liquid crystal display device such as a liquid crystal television has a bright adjusting circuit for setting a bright voltage applied to a liquid crystal display panel. Such a brightness adjustment circuit includes a temperature compensation circuit section, and by changing the bright voltage according to the temperature characteristic (change of the threshold voltage of the liquid crystal display panel with respect to temperature), an appropriate bright voltage is constantly displayed on the liquid crystal display. The voltage is applied to the panel so that the viewing angle of the liquid crystal display panel is kept constant.

FIGS. 7A and 7B show an example of such a conventional liquid crystal display device. In this liquid crystal display device, a liquid crystal display panel 1, a U-shaped fluorescent tube 2 for a backlight, a reflector 3 and a circuit board 4 are provided in this order from the front surface side to the back surface side. Of these, the liquid crystal display panel 1 includes two transparent substrates 1 made of glass or the like.
A liquid crystal (not shown) is enclosed between a and 1b. In this case, one end of the upper transparent substrate 1a is projected from the lower transparent substrate 1b, and the semiconductor chips 5 are mounted on two predetermined places on the lower surface of the projecting portion. Further, a predetermined one end of the lower transparent substrate 1b is projected from the upper transparent substrate 1a, and a semiconductor chip 6 is mounted at a predetermined one position on the upper surface of the projecting portion. These semiconductor chips 5 and 6 are for driving the liquid crystal display panel 1. One end of the flexible wiring board 7 is connected to the tip of the lower surface of the protruding portion of the upper transparent substrate 1a via an anisotropic conductive adhesive (not shown). A substantially L-shaped branch wiring board 7a is provided at a predetermined portion of the flexible wiring board 7. The branch wiring board 7a is bent 180 ° on the way, and its tip is connected to the tip of the upper surface of the protruding portion of the lower transparent substrate 1b through an anisotropic conductive adhesive (not shown). The other end of the flexible wiring board 7 is connected to the upper surface of one end of the circuit board 4. The circuit board 4 includes a bright adjusting circuit (not shown) including a temperature detecting thermistor 8 of the temperature compensating circuit portion provided on the lower surface thereof. The flexible wiring board 7 has an upper surface in FIG. 7A and a branch wiring board 7a continuous to the upper surface.
Although not shown, a wiring for applying a bright voltage to the liquid crystal display panel 1 from the bright adjusting circuit of the circuit board 4 is provided on one predetermined surface of the above. Then, in the bright adjusting circuit, a bright voltage according to the temperature detected by the thermistor 8 is applied to the liquid crystal display panel 1.

[0004]

By the way, in such a conventional liquid crystal display device, even if the ambient temperature changes, if the change is gradual, the liquid crystal display panel 1 and the thermistor 8 are provided between them. There is no temperature difference, an appropriate bright voltage set in the bright adjusting circuit is applied to the liquid crystal display panel 1, and the viewing angle of the liquid crystal display panel 1 becomes as expected, so there is no problem. However, for some reason, for example, when the ambient temperature changes abruptly due to the thermal influence of heat-generating components such as the fluorescent tube 2 or the start of use of the cooling / heating equipment, the arrangement position of the liquid crystal display panel 1 and the thermistor 8 Since the fluorescent tube 2 and the reflection plate 3 are separated from each other by the arrangement position, a temperature difference occurs between the liquid crystal display panel 1 and the thermistor 8, and the bright voltage applied to the liquid crystal display panel 1 has an optimum value. There is a problem that the viewing angle of the liquid crystal display panel 1 is changed due to the deviation. An object of the present invention is to provide a liquid crystal display device capable of preventing a temperature difference from occurring between a temperature detection element such as a thermistor and a liquid crystal display panel even if the ambient temperature changes suddenly for some reason. To do.

[0005]

The present invention relates to a liquid crystal display device having a bright adjusting circuit for setting a bright voltage applied to a liquid crystal display panel, wherein a temperature detecting element of a temperature compensating circuit section of the bright adjusting circuit is provided. Is provided on the liquid crystal display panel, and a temperature detecting resistance wiring is provided on at least one predetermined side outside the display area of the liquid crystal display panel so as to be connected in parallel with the temperature detecting element.

[0006]

According to the present invention, a temperature detecting element such as a thermistor is provided in the liquid crystal display panel, and a temperature detecting resistance wiring is provided on at least one predetermined side outside the display area of the liquid crystal display panel, and the temperature detecting element is arranged in parallel with the temperature detecting element. Since it is connected to the liquid crystal display panel, the temperature detecting means including the temperature detecting element such as the thermistor and the temperature detecting resistance wiring and the liquid crystal display panel can be arranged at substantially the same position. It is possible to prevent a temperature difference from easily occurring between the liquid crystal display panel and the temperature detecting means such as a thermistor even if the temperature changes rapidly.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential parts of a liquid crystal display device according to an embodiment of the present invention. In this figure, FIG.
The same names as those in (A) are designated by the same reference numerals, and the description thereof will be appropriately omitted. In this liquid crystal display device, the same material as the display electrodes (not shown) formed in the display area 11 is provided on a predetermined side outside the display area 11 on the upper surface of the transparent substrate 1b below the liquid crystal display panel 1. ITO (Indium Ti
A temperature detection resistance wiring 12 made of n oxide) is provided. The temperature detecting resistance wiring 12 has a structure in which the left ends of two linear resistance wirings are connected to each other, and the right ends of the two resistance wirings extend to the protruding end of the protruding portion of the lower transparent substrate 1b. It has been postponed. Then, connection pads (not shown) provided at two predetermined locations on the lower surface of the thermistor 8 are provided at predetermined locations on the temperature detecting resistance wiring 12 provided on the upper surface of the protruding portion of the lower transparent substrate 1b. It is connected via solder (not shown). The right end portion of the temperature detection resistance wiring 12 is connected to a circuit board (not shown) via a wiring 13 provided on a predetermined surface of the branch wiring board 7a. That is, for example, as shown in FIG. 7B, since the other end portion of the flexible wiring board 7 is connected to the upper surface of the one end portion of the circuit board 4, the temperature detection resistance wiring 12 is connected to the wiring 13.
It is connected to the circuit board 4 via. In this case, the temperature detection resistance wiring 12 and the wiring 13 are the same as the branch wiring substrate 7a.
Are connected to each other via an anisotropic conductive adhesive for connecting the tip of the to a predetermined portion on the upper surface of the protruding portion of the lower circuit board 1b. Then, in this state, as shown in FIG. 2, the temperature detection resistance wiring 12 is connected in parallel to the thermistor 8.

As described above, in this liquid crystal display device, since the thermistor 8 is provided at a predetermined position on the upper surface of the protruding portion of the transparent substrate 1b below the liquid crystal display panel 1, the thermistor 8 is provided.
The liquid crystal display panel 1 and the liquid crystal display panel 1 can be arranged at substantially the same position, and therefore, even if the ambient temperature suddenly changes for some reason, a temperature difference is less likely to occur between the thermistor 8 and the liquid crystal display panel 1. be able to. Moreover,
Since the temperature detection resistance wiring 12 is provided in parallel with the thermistor 8 on the transparent substrate 1b itself below the liquid crystal display panel 1, the temperature change of the temperature detection resistance wiring 12 follows the temperature change of the entire liquid crystal display panel 1. Can be made. In this case, the resistance-temperature characteristic of the temperature detection resistance wiring 12 made of ITO has a negative temperature coefficient as shown in FIG. 3, for example. On the other hand, a general thermistor also has a negative temperature coefficient.
Therefore, the matching of the resistance-temperature characteristics of the thermistor 8 and the temperature detection resistance wiring 12 can be obtained. As a result, in accordance with the temperature detected by the thermistor 8 and the temperature detecting resistance wiring 12, an appropriate bright voltage set in the bright adjusting circuit of the circuit board is always applied to the liquid crystal display panel 1 and the liquid crystal display panel 1 The viewing angle can always be as expected. Further, since the thermistor 8 and the temperature detecting resistance wiring 12 are connected to the circuit board through the wiring 13 provided on the branch wiring board 7a or the like, there is no need for a dedicated flexible wiring board for temperature detection, Therefore, the number of parts can be prevented from increasing.

In the above embodiment, the liquid crystal display panel 1
The temperature detection resistance wiring 12 is provided on a predetermined side outside the display area 11 on the upper surface of the lower transparent substrate 1b, but as shown in FIG. It may be provided. Further, in the above embodiment, the thermistor 8 and the temperature detection resistance wiring 12 are provided on the lower transparent substrate 1b, but they may be provided on the upper transparent substrate 1a as shown in FIG. 5, for example. In this case, the temperature detecting resistance wiring 12 and the thermistor 8 are provided on a predetermined side outside the display area 11 on the lower surface of the upper transparent substrate 1a, and the wiring 13 is provided at a predetermined position on the upper surface of the flexible wiring board 7. It is connected to the circuit board via.
Further, in the above embodiment, the temperature detecting resistance wiring 12 has a structure in which the left ends of two linear resistance wirings are connected, but the present invention is not limited to this. For example, as shown in FIG. 6, a structure may be adopted in which the left end portions of two resistance wirings having a rack tooth shape with a substantially square tooth shape are connected. In this case, for example, the length of one resistance wiring can be doubled with respect to the length of one side of the display area 11. Further, the material of the temperature detecting resistance wiring 12 may be platinum or the like, but if ITO is used as in the above embodiment, a display electrode made of ITO is patterned in the display region 11 of the lower transparent substrate 1b. At the same time, the temperature detection resistance wiring 12 can be patterned. When the material of the temperature detecting resistance wiring 12 is platinum, since it has a positive temperature coefficient, the thermistor 8 having the same positive temperature coefficient may be used. Further, in the above-mentioned embodiment, the flexible wiring board dedicated to the temperature detection is not used, but it may be used.

[0010]

As described above, according to the present invention, a temperature detecting element such as a thermistor is provided in a liquid crystal display panel, and a temperature detecting resistance wiring is provided on at least one predetermined side outside the display area of the liquid crystal display panel. Since the temperature detecting element is provided and connected in parallel with the temperature detecting element, the temperature detecting means including the temperature detecting element such as the thermistor and the temperature detecting resistance wiring and the liquid crystal display panel can be arranged at substantially the same position. Therefore, even if the ambient temperature suddenly changes for some reason, it is possible to prevent a temperature difference from easily occurring between the temperature detection means such as the thermistor and the liquid crystal display panel, and thus the brightness adjustment circuit is set. A proper voltage is always applied to the liquid crystal display panel, and the viewing angle of the liquid crystal display panel can always be kept as intended.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a partial circuit diagram of the liquid crystal display device.

FIG. 3 is a diagram showing resistance-temperature characteristics of resistance wiring for temperature detection of the liquid crystal display device.

FIG. 4 is a plan view of a main part of a liquid crystal display device according to another embodiment of the present invention.

FIG. 5 is a plan view of a main part of a liquid crystal display device according to still another embodiment of the present invention.

FIG. 6 is a diagram for explaining another example of the temperature detecting resistance wiring according to the present invention.

7A is a plan view of a part of an example of a conventional liquid crystal display device, and FIG. 7B is a cross-sectional view taken along the line BB.

[Explanation of symbols]

1 Liquid crystal display panel 7 Flexible wiring board 7a Branch wiring board 8 thermistor 12 Temperature detection resistance wiring

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Claims (4)

(57) [Claims] 1. A liquid crystal display device comprising a bright adjustment circuit for setting a bright voltage applied to a liquid crystal display panel, wherein a temperature detection element of a temperature compensation circuit section of the bright adjustment circuit is provided in the liquid crystal display panel, A liquid crystal display device characterized in that a temperature detecting resistance wiring is provided on at least one predetermined side outside the display area of the liquid crystal display panel and is connected in parallel with the temperature detecting element. 2. The liquid crystal display device according to claim 1, wherein the resistance wiring for temperature detection is composed of two resistance wirings, one end of which is connected. 3. The liquid crystal display according to claim 2, wherein the temperature detection element comprises a thermistor having a connection pad, and the connection pad of the thermistor is connected to the other end of the resistance wiring for temperature detection. apparatus. 4. The liquid crystal display device according to claim 1, wherein the resistance wiring for temperature detection is made of the same material as a display electrode of the liquid crystal display panel.