JPH10133177A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To temp. control both of a drive voltage of a transmission type liquid crystal panel and drive of a fluorescent tube heater being its light source by a detection temp. of a single temp. detection element without adding an excess contrivance to the drive circuit constitution of the liquid crystal panel. SOLUTION: A thermistor 90 is placed in the vicinity of both of a cold cathode tube 50 and the liquid crystal panel 60, and this thermistor 90 detects environmental temp. in the vicinity of both of the tube 50 and panel 60. A microcomputer 80 performs the temp. control of the cold cathode tube 50 by the heater 53 and the temp. control of the drive voltage of the panel 60 based on the detection temp. of the thermistor 90.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive display panel and a display device having a fluorescent tube such as a cold cathode tube as a light source thereof.

[0002]

2. Description of the Related Art Conventionally, as this type of display device, there is an instrument device in which an instrument panel is illuminated by a cold cathode tube as disclosed in Japanese Patent Publication No. 8-14500. In this instrument device, a heater is attached to the cold cathode tube, and at a low temperature, the cold cathode tube is heated by the heater so that the cold cathode tube is always operated in an appropriate operating temperature range.

In Japanese Patent Application Laid-Open No. 61-122630, the circuit configuration is devised. At low temperatures, the liquid crystal driving voltage is increased, and the liquid crystal is operated within an appropriate operating temperature range without using a heater. A liquid crystal driving circuit adapted to cause the above is shown.

[0004]

[Problems to be solved by the invention]
In Japanese Patent No. 4500, when a liquid crystal panel is employed as an instrument panel, the temperature of the cold cathode tube can be controlled at a low temperature, but the temperature of the liquid crystal panel cannot be controlled.
For this reason, at a low temperature, display failure of the liquid crystal panel is caused.

[0005] Further, in the case of Japanese Patent Application Laid-Open No. 61-122630, when a cold cathode tube is employed as a backlight for projecting a liquid crystal, only the above-mentioned contrivance of the liquid crystal driving circuit requires the cold cathode tube at a low temperature. Temperature control cannot be performed. Further, in the case of this publication, although a heater is not required, as described above, a device must be devised to increase the liquid crystal driving voltage at a low temperature, and the liquid crystal driving circuit becomes complicated.

In order to address the above, the present invention provides a display device, in which both the driving voltage of a transmissive liquid crystal panel and the driving of a fluorescent tube heater, which is a light source thereof, are driven by a liquid crystal panel driving circuit. It is an object of the present invention to control the temperature based on the detected temperature of a single temperature detecting element without adding an extra measure to the temperature.

[0007]

According to the present invention, when the ambient temperature of the liquid crystal panel and the fluorescent tube is low, the liquid crystal is controlled according to the temperature detected by the temperature detecting means. The control unit controls the liquid crystal panel driving unit and the heater such that the panel driving unit increases the driving voltage and the heater warms the fluorescent tube.

Accordingly, only a single temperature detecting means is used as a detecting means for detecting the ambient temperature between the liquid crystal panel and the fluorescent tube, and the liquid crystal panel and the fluorescent tube are provided with independent temperature detecting means, or the liquid crystal panel is driven. At low temperatures, the fluorescent tube can be warmed to the normal operating temperature range and the liquid crystal panel can be operated in the normal operating temperature range without any extra improvement to increase the driving voltage to the circuit configuration of the means. .

Here, according to the invention described in claim 3,
A liquid crystal panel is provided on a movable body such as a vehicle in a vertical shape in front of the operator, and a fluorescent tube is disposed on the movable body in front of the liquid crystal panel. Then, in addition to the display operation, the liquid crystal panel transmits light representing a view from the front of the moving body. Thus, a display device that can achieve the above-described effects can be provided as a head-up display for a moving object.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show an example in which the present invention is applied to a display device as a vehicular head-up display. The display device is disposed on an upper wall of a dashboard extending from a lower edge of a front windshield of the vehicle into a vehicle cabin, and the display device includes a driver M seated in a driver's seat of the vehicle. In the line of sight.

The display device includes a casing 30, as shown in FIGS. This casing 3
Reference numeral 0 denotes a lower casing member 30a and an upper casing member 30b, and the lower casing member 30a is attached to an upper wall of the dashboard at a bottom wall thereof. Also, the upper casing member 30b
Are assembled to the lower casing member 30a to form the casing 30.

The lid member 40 is provided with two bearings 43 (one bearing 4 in FIG. 2) on the front side of the upper surface of the casing member 30b through the opening 42a of the auxiliary cover 42 with the rotating shaft 41.
(Only 3 is shown). The cover member 40 is provided with a half mirror 4 on the back of the transparent cover 44.
The cover member 40 is positioned by the half mirror 45 in front of the driver M in the line of sight. Note that the rotating shaft 41 is formed integrally with the half mirror 45 as shown in FIG.

In the cover member 40, the half mirror 45 displays a reflection virtual image of a later-described reflection mirror 70 as a display image D through the transparent cover 44 in front of the half mirror 45 as shown in FIG. Also, the half mirror 45
Receives light representing the scene in front of the vehicle through the transparent cover 44 and causes the light to enter the eyes of the driver M. Here, since the cover member 40 is rotatable about the rotation shaft 41 as described above, the position of the half mirror 45 can be adjusted according to the position of the eyes of the driver M. When the display device is not used, the casing member 30 is
The opening 31 of b may be closed.

The half mirror 45 and the reflection mirror 7
If 0 is a magnifying mirror such as a concave mirror, the reflection virtual image of the reflection mirror 70 may be enlarged and displayed as a display image by the half mirror 45 in front of the vehicle.
In the casing 30, a cold cathode tube 50, a transmission type liquid crystal panel 60, and a reflection mirror 70 are arranged from the front to the rear as shown in FIG.
Driven by a drive circuit 52 (see FIG. 3) described later,
Light is projected on the liquid crystal panel 60 through the light diffusion plate 51.

A heater 53 (see FIG. 3) is attached to the surface of the cold-cathode tube 50 along the longitudinal direction thereof in the form of a string.
(See FIG. 3), and serves to heat the cold cathode tube 50. In FIG. 2, reference numeral 55 denotes a reflector. The liquid crystal panel 60 has liquid crystal sealed between the two electrode substrates.
Is driven by a driving circuit 61 (see FIG. 3) described below under the light projection from the cold cathode tube 50 through the mirror mirror 70, and display data from a control circuit 110 (see FIG. 3) described later is used as display light as a reflection mirror 70. Incident on.

The reflecting mirror 70 is, as shown in FIG.
The reflection mirror 70 is inclinedly supported by the support wall 32 of the casing member 30a, and reflects the display light from the liquid crystal panel 60 and enters the half mirror 45 through the transparent cover 33 as reflected light representing a virtual image. . The transparent cover 33 is fitted in the opening 31 of the casing member 30b.

Next, an electric circuit configuration for controlling the driving of the cold cathode tube 50, the heater 53 and the liquid crystal panel 60 will be described with reference to FIGS. The microcomputer 80 includes a thermistor 90 and driving circuits 52, 54,
61 and the printed circuit board 1 housed in the casing 30
00 is mounted and connected. The printed circuit board 10
0 is supported above the bottom wall of the casing member 30a in front of the cold cathode tube 50, and each connection terminal of the printed circuit board 100 is connected to the control circuit 11 through a cable 100a.
Connected to 0.

The microcomputer 80 executes the computer program according to the flowchart shown in FIG. 4 and, based on the detected temperature of the thermistor 90 and the display data from the control circuit 110, via each of the driving circuits 52, 54 and 61, the cold cathode fluorescent lamp. An arithmetic process for driving and controlling the heater 50, the heater 53, and the liquid crystal panel 60 is performed. The computer program is stored in the ROM of the microcomputer 80.
Is stored in advance.

The thermistor 90 is located near both the cold cathode tube 50 and the liquid crystal panel 60, and detects the ambient temperature near both the cold cathode tube 50 and the liquid crystal panel 60. In the present embodiment, the cold cathode tube 50, the heater 53, the liquid crystal panel 60, the driving circuits 52, 54, 61, the microcomputer 80, and the thermistor 90 constitute a circuit unit U of the display device.

The control circuit 110 provides vehicle speed information of the vehicle,
The navigation information and the rotation speed information of the engine are output to the microcomputer 80 as display data. However, since the circuit unit U and the casing 30 are arranged on the upper wall of the dashboard, it is desired that the circuit unit U and the casing 30 be as small as possible. For this reason, the control circuit 110 is provided at an appropriate place of the vehicle, separately from the circuit unit U and the casing 30.

In this embodiment configured as described above,
When the display device is activated, the microcomputer 8
0 executes the computer program according to the flowchart of FIG. 4 as follows. In step 200, the temperature detected by the thermistor 90 is input to the microcomputer 80 and A / D converted. Hereinafter, this AD
The temperature after the conversion is called the ambient temperature T.

Next, at step 210, the ambient temperature T
Is compared to a predetermined low temperature of 20 ° C. However, the prescribed
The low temperature of 20 ° C is normal operation of the liquid crystal in the liquid crystal panel 60.
This corresponds to the lower limit of the temperature range. In addition, this predetermined low temperature
The temperature is not limited to 20 ° C.
May be appropriately changed according to the conditions. And around
If the temperature T is lower than 20 ° C.,
Is NO. Then, to step 211
And the driving voltage V of the liquid crystal panel 60 _ODrive to increase to 7V
The command is output to the drive circuit 61.

Next, at step 220, the ambient temperature T is compared with a predetermined low temperature of 10 ° C. However, the predetermined low temperature of 10 ° C. corresponds to the lower limit temperature of the normal operating temperature range of the cold cathode tube 50. The predetermined low temperature is
Not limited to 10 ° C., the temperature characteristics of the cold-cathode tube 50 may be considered, and the temperature may be appropriately changed as needed. If the ambient temperature T is lower than 10 ° C., step 220
Is NO, and in step 221,
A drive command for the heater 53 is output to the drive circuit 54.

As described above, each drive command is transmitted to each drive circuit 5
4 and 61, the heater 53 is driven by the drive circuit 54 to heat the cold-cathode tube 50 to 20 ° C. or higher, and the liquid crystal panel 60 is driven by the drive circuit 6 at a drive voltage of 7V.
1 driven. Thereby, both the cold cathode tube 50 and the liquid crystal panel 60 (that is, liquid crystal) can operate within the respective normal operating temperature ranges. As a result, even when the ambient temperature T is low as described above, the liquid crystal panel 60 shows a good display quality under a good light quantity from the cold cathode tube 50.

In such a state, if the determination in step 220 is YES, in step 222,
A drive stop command for the heater 53 is output to the drive circuit 54. Thus, the operation of the heater 53 to warm the cold cathode tube 50 is stopped. In step 210, YE
If the determination is S, a drive stop command for the heater 53 is output to the drive circuit 54 in step 212. Thus, the operation of the heater 53 to warm the cold cathode tube 50 is stopped.

Next, in step 213, a drive command to reduce the drive voltage V _O of the liquid crystal panel 60 to 5 V is output to the drive circuit 61. Note that the driving voltage V _O = 5V
Is the value when the liquid crystal is in the normal operating temperature range. At this time, the cold cathode tube 50 and the liquid crystal panel 6
Since both 0 are maintained within the respective normal operating temperature ranges, both the cold-cathode tube 50 and the liquid crystal panel 60 can operate normally. As a result, the liquid crystal panel 60 shows a good display quality under a good light quantity from the cold cathode tube 50.

When the processing in step 221, 222 or 213 is completed as described above, the display data from the control circuit 110 is taken into the microcomputer 80 in step 230. Accordingly, display data from the control circuit 110 is output to the drive circuit 61.
Then, the drive circuit 61 drives the liquid crystal panel 60 to display the display data at a drive voltage of 7 V or 5 V.

Thus, the liquid crystal panel 60 allows the light representing the display data to be incident on the reflection mirror 70 under a favorable light quantity from the cold-cathode tube 50 in accordance with the ambient temperature. When the reflection mirror 70 reflects the light representing the display data from the liquid crystal panel 60 and makes the light enter the half mirror 45, the half mirror 45 converts the display data into a display image D.
Display as Further, light representing a scene in front of the vehicle passes through the lid member 40 and enters the eyes of the driver M. Thereby, the driver M can visually recognize the scene in front of the vehicle together with the display image.

In this case, as described above, with the use of the single thermistor 90, the cold cathode tube 50 and the liquid crystal panel 6 can be used.
The ambient temperature of both 0 is detected, and the temperature control of the heater 53 of the cold cathode tube 50 and the temperature control of the driving voltage of the liquid crystal panel 60 are performed based on the detected temperatures. Therefore, without providing a thermistor independently for the liquid crystal panel and the cold-cathode tube, or adding extra improvement for increasing the drive voltage to the circuit configuration of the drive circuit 61, the cold-cathode tube 50
To a normal operating temperature range and the liquid crystal panel 60.
Can be operated in a normal operating temperature range.

As a result, even if the ambient temperature is low, it is possible to obtain a good display quality of the liquid crystal panel while securing a good light quantity of the cold cathode tube 50. Incidentally, there is an example as shown in FIG. 5 in the display by the liquid crystal panel 60 of the display device. That is, FIGS. 5A and 5B show examples of the vehicle speed display of the vehicle. In this case, the vehicle speed becomes equal to the set vehicle speed (for example, 100
km / h), the display color in FIG. 5A is inverted to the display color in FIG.

FIGS. 5 (c) and 5 (d) show examples of direction indication display of the vehicle. FIGS. 5E to 5H
Shows a navigation display example of the vehicle. This navigation display is a display example at the time of route guidance of the vehicle,
When the intersection is near, the display is as shown in FIGS. The display in FIG. 5 (g) indicates “diagonally right 500 m ahead”, and the display in FIG. 5 (h) indicates “diagonally right in corner of convenience store”.

FIGS. 5E and 5F show the vehicle speed of the vehicle on the right side. FIG. 5E shows that the vehicle is traveling on a route when there is a left vehicle mark. FIG. 5F shows that the vehicle is off the route when there is no mark for the vehicle. Here, FIG.
In (e) and (f), when the vehicle is running, scroll display may be performed so that the center line L moves toward the front.

The present invention is not limited to a thermistor, but may be implemented by employing various temperature detecting elements instead. Further, in the above embodiment, an example in which the present invention is applied to a display device as a head-up display for a vehicle has been described. However, the present invention is not limited to this. The present invention may be applied to (including a panel), and not limited to a head-up display, various display devices (including a cold cathode tube and a transmission type liquid crystal panel)
The present invention may be applied to the present invention.

In practicing the present invention, the light source of the liquid crystal panel is not limited to a cold cathode tube, but may be a fluorescent tube.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 in FIG.

FIG. 3 is a circuit configuration diagram for driving and controlling a heater, a cold cathode tube, and a liquid crystal panel.

FIG. 4 is a flowchart showing the operation of the microcomputer of FIG.

FIGS. 5A to 5J are exemplary display diagrams of a liquid crystal panel.

[Explanation of symbols]

M: driver, 50: cold cathode tube, 52, 61: drive circuit,
53: heater, 60: transmissive liquid crystal panel, 80: microcomputer, 90: thermistor.

Claims (3)

[Claims] 1. A transmissive liquid crystal panel (60); a fluorescent tube (50) driven by fluorescent tube driving means (52) to project light onto the liquid crystal panel; A liquid crystal panel driving means (61) for applying a driving voltage to the liquid crystal panel so as to perform a display operation, a heater (53) for heating the fluorescent tube, and a unit for detecting an ambient temperature between the liquid crystal panel and the fluorescent tube. One temperature detecting means (90), wherein when the ambient temperature is low, the liquid crystal panel driving means increases the driving voltage in accordance with the detected temperature of the temperature detecting means, and the heater warms the fluorescent tube. Control means for controlling the liquid crystal panel driving means and the heater (2
10, 211, 220, 221). 2. At least one of the fluorescent tube driving means and the liquid crystal panel driving means is a driving circuit provided on a circuit board (100), and the temperature detecting means is a temperature detecting element provided on the circuit board. The display device according to claim 1, wherein: 3. The liquid crystal panel is provided on a moving body such as a vehicle in a vertical shape in front of a driver (M), and the fluorescent tube is arranged on the moving body in front of the liquid crystal panel. 3. The display device according to claim 1, wherein the liquid crystal panel transmits light representing a view from the front of the moving body in addition to the display operation. 4.