JP2002357812A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device obtaining excellent visibility by providing adequate driving voltage to a liquid crystal display element irrespective of an installed position of a temperature sensor. SOLUTION: The liquid crystal display device is provided with a liquid crystal display element 1, a circuit board 4 electrically connected to the liquid crystal display element 1 via an electrode lead 12, a panel 8 disposed on the front surface side of the liquid crystal display element 1 having a display window 7 to make a display part of the liquid crystal display element 1, not depicted in the figure, visually observable and a thermistor 9 to detect ambient temperature of the liquid crystal display element 1. A lighting window part 15 is provided on the panel 8 corresponding to the thermistor 9.

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 provided with a liquid crystal display element or a temperature sensor for detecting an ambient temperature thereof.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view of a motorcycle instrument to which a liquid crystal display device is applied. A synthetic resin cell case 2 holding a liquid crystal display element 1 for displaying a traveling speed, a traveling distance, a remaining fuel amount, and the like of the motorcycle is attached and fixed to a circuit board 4 using screws 3. The cell case 2 holds the liquid crystal display element 1 and receives light from an LED 5 as a light source mounted on the circuit board 4.
It also serves as a light guide member for illuminating the liquid crystal display element 1 from behind, and is colorless and transparent. On the front side of the liquid crystal display device 1, a panel 8 having a display window 7 for allowing a display unit (not shown) of the liquid crystal display device 1 to be visually recognized is provided. The panel 8 has a hollow portion where the display window 7 is formed, and the other portions are opaque.

Although not shown, the circuit board 4 is equipped with control means such as a microcomputer, a drive circuit, and a power supply circuit for causing the liquid crystal display element 1 to perform a display operation. A thermistor 9 as a temperature sensor is mounted on the circuit board 4 located behind the liquid crystal display element 1 in order to detect the ambient temperature of the liquid crystal display element 1. The liquid crystal display device thus configured is housed in a synthetic resin, for example, a white case 10, and the front opening side of the case 10, that is, the front side of the panel 8 is a colorless transparent see-through plate 11 made of synthetic resin. It is covered with.

In the liquid crystal used for the liquid crystal display element 1, even if the applied driving voltage is the same, the contrast changes depending on the temperature, and the display may be difficult to see. Therefore, it is important to apply a drive voltage suitable for the temperature in displaying the liquid crystal display element 1 with an appropriate contrast. Therefore, the ambient temperature of the liquid crystal display element 1 is set to the thermistor 9.
The liquid crystal display element 1 is detected based on the detected temperature.
Is adjusted to apply an appropriate drive voltage to the liquid crystal display element 1.

FIG. 4 shows an example of "temperature-liquid crystal drive voltage characteristics". The relationship between the temperature and the drive voltage differs depending on the liquid crystal. In particular, in the case of a liquid crystal having a large number of pixels in the dot matrix drive method, the drive voltage (dot-dash line) at which the display of the liquid crystal display element 1 can be visually recognized with respect to a change in ambient temperature. (The range between the upper limit a and the lower limit b indicated by) is not linear, and the drive voltage tends to decrease and the range tends to narrow as the temperature increases. Therefore, the optimum drive voltage for the temperature is set at the center value of the range of the drive voltage, that is, in FIG. 4, the solid line X is set below 50 ° C. and the solid line Y is set above 50 ° C. Therefore, the temperature compensation of the liquid crystal display element 1 can be achieved by selecting a drive voltage having an optimal drive voltage characteristic represented by the solid lines X and Y according to the detection result of the ambient temperature by the thermistor 9 and applying the drive voltage to the liquid crystal display element 1. .

[0006]

However, as shown in FIG. 3, the position for detecting the ambient temperature of the liquid crystal display element 1 is on the circuit board 4 (where the thermistor 9 is mounted). And the temperature on the circuit board 4 may be different. In particular, when used in an instrument of a farm work machine such as a motorcycle or a tractor that is easily exposed to direct sunlight, even if the temperature of the liquid crystal display element 1 rises due to the direct sunlight passing through the see-through plate 11 and the liquid crystal display device. The temperature on the circuit board 4 that is not exposed to direct sunlight does not rise, and the temperature difference may actually be about 20 ° C. In some cases, the temperature is detected by mounting a temperature sensor on the liquid crystal display element 1 itself. However, the mounting position of the temperature sensor is usually covered by the panel 8 so as not to receive direct sunlight. A temperature difference may occur with a portion located in the display window 7 which receives the temperature.

Then, a driving voltage different from the driving voltage in the optimum driving voltage characteristic Y at the time of high temperature shown in FIG. 4 is applied to the liquid crystal display element 1, and the driving voltage out of the range of the driving voltage described above. A voltage may be applied to the liquid crystal display element 1. For example, if the temperature of the liquid crystal display element 1 is 80 ° C. but the temperature detected by the thermistor 9 is 60 ° C., Is applied to the liquid crystal display element 1. As a result, there has been a problem in that the parts other than the display part are darkened, the contrast is reduced, and the display is difficult to see.

The present invention has been made in view of the above-described circumstances, and provides a liquid crystal display device which provides a proper driving voltage to a liquid crystal display element irrespective of a mounting position of a temperature sensor to obtain good visibility. The purpose is to:

[0009]

According to the present invention, there is provided a liquid crystal display element, a circuit board electrically connected to the liquid crystal display element, and a liquid crystal display element provided on a front side of the liquid crystal display element. A panel having a display window through which a display portion of the liquid crystal display element can be visually recognized, and a temperature sensor for detecting the temperature of the liquid crystal display element or its surroundings, wherein the panel has a lighting window corresponding to the temperature sensor. Part is provided.

Further, a cylindrical wall is provided around the temperature sensor.

Further, the window portion is provided with a light-transmissive colored layer having a color similar to that of the ground color layer of the panel.

Further, the temperature sensor is close to the panel.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described by way of an embodiment of a liquid crystal display device used for an instrument for a motorcycle as in the prior art. The same or corresponding parts as those in the conventional example are denoted by the same reference numerals, and the details thereof will be described. Description is omitted.

FIG. 1 shows a first embodiment of the present invention. A liquid crystal display element 1 for displaying a traveling speed, a traveling distance, a remaining fuel amount, and the like is held in a cell case 2 and fixed to a circuit board 4 while being fixed. Are electrically connected to the circuit board 4 by the electrode leads 12. On the front side of the liquid crystal display element 1, there is provided a panel 8 having a display window 7 through which a display (not shown) of the liquid crystal display element 1 can be visually recognized. These are housed in, for example, a white case 10 made of a synthetic resin, and the front side of the panel 8 is a transparent and colorless transparent plate 1.
1 covered.

The panel 8 is a colorless and transparent substrate 1 made of synthetic resin.
3 is provided with an opaque black ground color layer 14, and a portion to be the display window 7 is hollowed out. In addition, round windows 15 for lighting are provided at eight places of the panel adjacent to the liquid crystal display element 1. Window 15 in the present embodiment
Is formed by not applying the black ground color layer 14 at that location. That is, the surface of the transparent substrate 13 is exposed in a round shape.

The surface of the panel 8 is provided with a transparent matting layer 16. By applying the matting layer 16, the surface of the panel 8 is less likely to be damaged, and the ground color layer 14 is in a matte state. In addition, the window 15 is also in a matte state.
5 is hard to see. The display window 7 may be in a transparent state in which the ground color layer 14 is not applied similarly to the window portion 15 without hollowing the location. If there is no inconvenience in design, the window 15 may be hollowed out and the matte layer 16 may not be provided. Further, the shape is not limited to a round shape, but may be any shape.

The cell case 2 holds the liquid crystal display element 1 as in the conventional case, and also has a role as a light guide member for illuminating the liquid crystal display element 1 from behind by taking in the light of the LED 5 from the light receiving section 6, It is colorless and transparent. Further, two cell cases corresponding to the windows 15 provided in the panel 8 include:
A cylindrical wall 17 is provided.

The circuit board 4 is mounted with control means such as a microcomputer, a drive circuit, and a power supply circuit (not shown) for causing the liquid crystal display element 1 to perform a display operation, in addition to the LEDs 5. A thermistor 9 for detecting the ambient temperature of the liquid crystal display element 1 is mounted on the circuit board 4 corresponding to the window 15 provided on the panel 8. As described above, the window 1
A cylindrical wall 17 is provided at two locations of the cell case corresponding to the cell wall 5. Therefore, the cylindrical wall 17 is provided around the thermistor 9. Note that the microcomputer calculates the temperature of the liquid crystal display element 1 based on the temperature detected by the thermistor 9.
The optimum driving voltage value (see FIG. 4) to be applied to the liquid crystal display element 1 is obtained and applied to the liquid crystal display element 1.

When the liquid crystal display thus constructed is irradiated with sunlight, the liquid crystal display element 1 receives direct sunlight through the see-through plate 11 and also directly enters the window 15 provided on the panel 8. . Then, sunlight enters through the window 15 into the cylindrical chamber 18 surrounded by the cylindrical wall 17, and the temperature around the circuit board 4 on which the thermistor 9 is mounted is detected by the thermistor 9. Therefore, even if the temperature is not the same as that of the liquid crystal display element 1, a temperature close to the temperature of the liquid crystal display element 1 can be detected (the temperature difference between the liquid crystal display element 1 and the place where the thermistor 9 is mounted is small). The drive voltage applied to the display element 1 hardly deviates from the above-described range of the drive voltage, so that the display section can be visually recognized well.

As shown in FIG. 4, the optimum driving voltage of 50 ° C. or more is brought closer to the lower limit b of the driving voltage in advance and the broken line Y ′
With such characteristics, when the temperature difference becomes large on the high temperature side, it becomes more difficult to deviate from the upper limit a of the driving voltage. Therefore, it is better to set such characteristics.

Further, since the cylindrical wall 17 is provided around the thermistor 9, even if the sunlight does not irradiate from directly above the thermistor 9 (even if the light is slightly oblique), the light that has entered the cylindrical chamber 18 can be reduced. The temperature detected by the thermistor 9 is closer to the liquid crystal display element 1 as compared with the related art, because it is reflected on the cylindrical wall 17 and reaches the thermistor 9 or heat is accumulated in the cylindrical chamber 18 by the cylindrical wall 17. Since the temperature can be detected, the liquid crystal display element 1
Is hard to deviate from the range of the driving voltage at which the display of the liquid crystal display element 1 can be visually recognized.
The display part can be visually recognized well.

FIG. 2 shows a second embodiment of the present invention. It differs from the first embodiment only in the window 15 provided in the panel 8. In the present embodiment, a light-black light-transmitting smoke layer (colored layer) 19 of the same color or a similar color to the ground color layer 14 is applied to the window 15 where the transparent substrate 13 surface in the first embodiment is exposed. It was done. The ground color layer 1
For example, when the color 4 is white, a white light-transmitting colored layer is applied.

With this configuration, although the amount of light entering the cylindrical chamber 18 is reduced as compared with the first embodiment, it can be detected at a temperature closer to the liquid crystal display element 1 as compared with the prior art. The driving voltage applied to the element 1 is hardly out of the range of the driving voltage at which the display of the liquid crystal display element 1 can be visually recognized, and therefore, the display unit can be visually recognized well. Further, by applying a smoke layer 19 of the same color or a similar color to the ground color layer 14 of the panel 8 on the surface of the window 15, the presence of the window 15 can be made inconspicuous.

In each of the above embodiments, since the cell case 2 is made of a transparent member, the light of the LED 5 reaches the cylindrical wall 17 to cause a problem (for example, the light of the LED 5 leaks from the window 15). Then, a measure for preventing light from leaking may be taken. Alternatively, the cell case 2 may be opaque white, and the LED 5 may be arranged directly behind the liquid crystal display element 1 for illumination. Further, the cylindrical wall 17 is provided with the panel 8
And may be separated from the cell case 2 or the panel 8.

The circuit board 4 does not need to be a single sheet. For example, two boards connected by flexible lead wires are arranged, and one of them is arranged close to the panel 8, and If the thermistor 9 is mounted on the
Since the thermistor 9 is close to the panel 8, it is easy for sunlight to directly hit the thermistor 9, and a temperature closer to the temperature of the liquid crystal display element 1 can be detected. A good visibility is obtained because the temperature difference is less generated.

Although the thermistor 9 is mounted on the circuit board 4 in each of the above embodiments, the mounting position of the thermistor 9 can be freely selected as long as it is a position corresponding to the window 15. Further, the thermistor 9 is used as the temperature sensor, but the temperature sensor is not limited to this.

[0027]

According to the first aspect of the present invention, since a temperature close to the temperature of the liquid crystal display element can be detected, the drive voltage applied to the liquid crystal display element is such that the display voltage of the liquid crystal display element can be visually recognized. , And the display portion can be visually recognized well.

According to the second aspect of the present invention, the drive voltage applied to the liquid crystal display element can be detected at a temperature close to the liquid crystal display element even if the light illuminating the window is oblique. It is difficult to deviate from the range of the driving voltage at which the display is visible, and the display portion can be visually recognized well.

According to the third aspect of the present invention, the display portion can be viewed well and the presence of the window can be made inconspicuous.

According to the fourth aspect of the present invention, the temperature difference between the liquid crystal display element and the temperature detection point is less likely to occur, and good visibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a motorcycle instrument to which a first embodiment of the present invention is applied.

FIG. 2 is a partial cross-sectional view showing the panel of the second embodiment.

FIG. 3 is a cross-sectional view of a motorcycle instrument to which a conventional liquid crystal display device is applied.

FIG. 4 is a graph showing a relationship between a temperature of a liquid crystal display element and a liquid crystal driving voltage.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 liquid crystal display element 4 circuit board 7 display window 8 panel 9 thermistor (temperature sensor) 14 ground color layer 15 window section 17 cylindrical wall 19 smoke layer (colored layer)

Claims (4)

[Claims] 1. A liquid crystal display element, a circuit board electrically connected to the liquid crystal display element, and a display disposed on a front side of the liquid crystal display element so that a display portion of the liquid crystal display element can be visually recognized. A liquid crystal display device, comprising: a panel having a window; and a temperature sensor for detecting the liquid crystal display element or its ambient temperature, wherein the panel is provided with a lighting window corresponding to the temperature sensor. 2. The liquid crystal display device according to claim 1, wherein a cylindrical wall is provided around the temperature sensor. 3. The liquid crystal display according to claim 1, wherein a light-transmissive colored layer having a color similar to that of the ground color layer of the panel is provided on the window portion. apparatus. 4. The liquid crystal display device according to claim 1, wherein the temperature sensor is close to the panel.