JPH11184397A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a semihot fluorescent tube with high luminance in daytime and also use an auxiliary light sources in nighttime to make back light low luminance by providing a semihot fluorescent tube and an auxiliary light sources as the light source for the back light. SOLUTION: The back light 2 use one semihot fluorescent tube 3 and two auxiliary electric bulbs 4 as its light source. The semihot fluorescent tube 3 in use is able to emit light with a luminance almost as high as a hot-cathode fluorescent tube and is a small type having a tube nearly as thin and short as a cold-cathode fluorescent tube. The auxiliary electric bulbs 4 are small hot electric bulbs which emit light with lower luminance than the semihot fluorescent tube 3 and arranged in front of both the end parts of the semihot fluorescent tube 3. Further, a reflector 5 which has a concave reflecting surface is arranged behind the semihot fluorescent tube 3. When the semihot fluorescent tube 3 is turned on, the light from the semihot fluorescent tube 3 can efficiently be emitted forward directly or by being reflected by the reflector 5, thereby enabling high-luminance lighting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device mounted on a dashboard or the like of a vehicle and capable of displaying an image on a front background or the like.

[0002]

2. Description of the Related Art As shown in FIG. 5, a display device 1 in which a combiner 11 is arranged on a dashboard 21 of an automobile at an angle and an image reflected by the combiner 11 is displayed to a driver A has been known. Have been. This display device 1
As shown in FIG. 6, a liquid crystal display device 14 is disposed in front of the backlight 2 (above the drawing) via a heat absorbing filter 12 and a light scattering plate 13, and an optical system is provided in front of the liquid crystal display device 14. The combiner 11 is arranged via a lens 15. The backlight 2 is an illumination device that arranges the reflector 5 behind the light source 16 and irradiates the light from the light source 16 directly or by reflecting the light from the reflector 5 and irradiating the light forward. The heat absorbing filter 12 is provided in the light source 1.
6 is a filter for absorbing heat rays from the light scattering plate 13.
Is for converting the light from the light source 16 into a uniform light source without unevenness.

The liquid crystal display device 14 is a display device that displays an image by controlling the transparency / opacity of a liquid crystal layer for each pixel, and displays an image by transmitting or not transmitting light from a light source 16 for each pixel. An image is formed. The image displayed on the liquid crystal display device 14 is reflected by the combiner 11 via the optical lens 15. The combiner 11 is a half mirror formed by coating a curved transparent resin lens or glass lens. The combiner 11 transmits the front background as it is, reflects the image of the liquid crystal display device 14, and They can be displayed in layers. Also, since the image of the liquid crystal display device 14 is displayed as a distant virtual image by the optical lens 15 and the combiner 11, for the driver A shown in FIG. It looks like it is in

[0004] The display device 1 is used as a car navigation system or an instrument necessary for the operation of a motor vehicle by displaying an image informing a driver A of a route or the like. Here, conditions as the light source 16 of the backlight 2 in the display device 1 will be described.

(1) In the daytime, it is necessary to display an image superimposed on a bright external background. Therefore, in order to ensure sufficient visibility, a light source with high luminance is required.

(2) In the nighttime, it is necessary to make the luminance sufficiently low so as not to impair the visibility of a dark background, so that light can be adjusted in a wide range from high luminance to low luminance according to external conditions. There must be.

(3) It must be small enough to be mounted in a narrow space such as the dashboard 21 of an automobile.

(4) Since heat is not easily dissipated in a narrow space such as the dashboard 21, the light source must generate less heat.

A xenon bulb or the like is most suitable for satisfying the above conditions (1) to (3). However, since such a high-luminance bulb generates a lot of heat, it satisfies the condition (4). Can not. There is also a method of attaching a fan or the like to perform forced air cooling, but in this case, the condition (3) cannot be satisfied. For this reason, as the light source 16 of the display device 1, it is desirable to use a fluorescent tube that generates a relatively small amount of heat and meets the condition (4). The fluorescent tubes include a hot cathode fluorescent tube and a cold cathode fluorescent tube. As shown in Table 1, the "brightness" which satisfies the condition (1) and the "dimming range" which satisfies the condition (2). There is a difference in the “size of tube” that is the condition of (3).

[Table 1] That is, the hot-cathode fluorescent tube has high brightness and a wide light control range, and thus satisfies the conditions (1) and (2), but satisfies the condition (3) because the tube diameter is large and the length is long. Absent. On the other hand, the cold cathode fluorescent tube has a wide dimming range, though not as large as the hot cathode fluorescent tube, and can be reduced in diameter to about 2 mm to 5 mm, so that it meets the conditions of (2) and (3). However, the condition (1) is not satisfied because the luminance is low.

Accordingly, semi-hot fluorescent tubes have been developed which combine the features of high brightness of these hot cathode fluorescent tubes and the thinning of cold cathode fluorescent tubes. This semi-hot fluorescent tube operates as a cold cathode fluorescent tube without preheating at the time of startup,
Since the lamp operates as a hot-cathode fluorescent tube by self-heating during lighting, it is possible to obtain the same high brightness as the hot-cathode fluorescent tube, and it is possible to make the same thin tube as the cold-cathode fluorescent tube, as shown in Table 1. In addition, the conditions of (1) and (3) are satisfied.

[0011]

However, when the brightness of the semi-hot fluorescent tube is reduced by dimming, the self-heating becomes insufficient, the operation becomes unstable, and the electrodes are worn and the life is shortened. , (2) cannot satisfy the condition of a wide light control range. For this reason, if a semi-hot fluorescent tube is used for the display device 1, it must be used with high brightness. Therefore, when the outside becomes dark at night, the display brightness becomes too high and the external background becomes difficult to see. there were.

The present invention has been made in view of such circumstances, and a display device that uses a semi-hot fluorescent tube having a high luminance in the daytime and has a low luminance backlight by using an auxiliary light source in the nighttime. It is intended to provide.

[0013]

According to a first aspect of the present invention, a display device includes:
Since the auxiliary light source is provided together with the semi-hot fluorescent tube as a light source for the backlight, the semi-hot tube can be turned on during the daytime when the external background is bright, and a high-luminance display can be performed. In this case, the auxiliary light source can be turned on to further improve the luminance. Also, at night when the background is dark, turning off the semi-hot fluorescent tube and turning on the auxiliary light source with low luminance prevents the display from being too bright and making the background difficult to see.

In the display device according to the second aspect, the semi-hot fluorescent tube and the auxiliary light source are respectively dimmed by separate dimming circuits. In the nighttime, the auxiliary light source can be appropriately adjusted in accordance with external darkness within a low luminance range. In addition, by turning on both the semi-hot fluorescent tube and the auxiliary light source and dimming each of them, dimming can be performed in a wider range.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show one embodiment of the present invention. FIG. 1 is an overall perspective view of a backlight of a display device, and FIG. 2 is an assembly showing a fixing member of the backlight and a lighting circuit board. FIG. 3 is a perspective view, FIG. 3 is an assembled perspective view showing a state in which the lighting circuit board is fixed to a fixing member of the backlight, and FIG.
FIG. 2 is an assembled perspective view showing a reflector of the backlight. Components having the same functions as those of the conventional example shown in FIGS. 5 and 6 are denoted by the same reference numerals.

As for the display device of the present embodiment, the backlight 2 of the display device 1 mounted on the dashboard 21 of an automobile will be described similarly to the conventional example shown in FIGS.
As shown in FIG. 1, the backlight 2 uses one semi-hot fluorescent tube 3 and two auxiliary light bulbs 4 as light sources. The semi-hot fluorescent tube 3 is a fluorescent tube that can emit light with the same high brightness as the hot cathode fluorescent tube, and uses a small tube having a tube diameter as small as the cold cathode fluorescent tube and a short length. The auxiliary light bulb 4 is a small heat light bulb that emits light at a lower luminance than the semi-hot fluorescent lamp 3, and is disposed in front of both ends of the semi-hot fluorescent lamp 3. A reflector 5 having a concave reflecting surface is disposed behind the semi-hot fluorescent tube 3. Therefore, when the semi-hot fluorescent tube 3 is turned on, the backlight 2 reflects light from the semi-hot fluorescent tube 3 directly or by the reflector 5,
It is possible to efficiently irradiate forward, and high-luminance illumination becomes possible. Also, when the auxiliary light bulb 4 is turned on, the light from the auxiliary light bulb 4 can be emitted directly or reflected by the reflector 5 and irradiated forward. However, these auxiliary light bulbs 4 need only be capable of low-brightness illumination, so that there is no need to efficiently irradiate light forward, and therefore, both ends of the side which do not block light from the semi-hot fluorescent tube 3. Located in the department.

The detailed structure of the backlight 2 will be described according to an assembling process. This backlight 2 is shown in FIG.
Is fixed to the main body of the display device 1 (not shown) by a fixing member 6 shown in FIG. The fixing member 6 is a plastic molded product having an arm 6a protruding forward from substantially plate-shaped both sides,
The lighting circuit board 7 is screwed to the front surface of the plate portion. The lighting circuit board 7 is a circuit board on which an inverter circuit, a voltage adjustment circuit, and the like, which serve as a lighting circuit for the semi-hot fluorescent tube 3 and the auxiliary light bulb 4, are formed. Has a function. However, the lighting circuit of the semi-hot fluorescent tube 3 is configured to perform dimming only within a certain high-luminance range because the electrodes deteriorate when the semi-hot fluorescent tube 3 is lit at low luminance. On the other hand, the lighting circuit of the auxiliary light bulb 4 has no limitation on the dimming range because the hot light bulb is used, and at least the luminance is sufficiently lower than the luminance when the semi-hot fluorescent tube 3 is dimmed to the lowest luminance. The light can be adjusted up to the range. The semi-hot fluorescent tube 3 is directly connected to a lead wire drawn from the lighting circuit board 7, and the auxiliary light bulb 4 is mounted on a socket 8 connected to the tip of the lead wire drawn from the lighting circuit board 7. It has become. The socket 8 may be of any type such as a screw type, a plug type, or a wedge type.
If the auxiliary light bulb 4 does not need to be replaced, it may be directly connected to a lead wire as in the case of the semi-hot fluorescent tube 3.

When the lighting circuit board 7 is screwed to the fixing member 6, as shown in FIG. 3, the lead wire connected to the semi-hot fluorescent tube 3 or the auxiliary light bulb 4 is connected to the arm 6a of the fixing member 6. So that it fits in the recess. As shown in FIG. 4, the reflector 5 is a plastic molded product having a concave curved surface 5a mirror-finished forward, and has an arm 5b protruding forward from both sides. Then, washers 9 are fitted into the tips of the arms 5b, respectively.
Since the reflector 5 has a wall surface surrounding the back surface of the curved surface 5a, as shown in FIG.
By attaching this back side to the front surface of the fixing member 6 and attaching it, it becomes a cover that covers the lighting circuit board 7. Also,
The reflector 5 is formed by forming a conductive thin film of aluminum or the like on the entire peripheral surface as well as the curved surface 5a.
The curved surface 5a serves as the reflection surface, and the lighting circuit board 7
Also serves as an electromagnetic shield to shield noise from an inverter circuit or the like.

When attaching the reflector 5 to the fixing member 6, both ends of the semi-hot fluorescent tube 3 are connected to the reflector 5
The washer 9 is inserted into the groove at the tip of the arm 5b. The auxiliary light bulb 4 has a washer 9
From the inside into the socket 8 that has passed through the hole. The arm 5b of the reflector 5 on which the semi-hot fluorescent tube 3 and the auxiliary light bulb 4 are mounted is fitted into the recess of the arm 6a of the fixing member 6. The reflector 5 is fixed to the fixing member 6 by screwing the screws 10 from outside the arm portions 6 a of the fixing member 6 and screwing the screws 10 into the screw holes of the washer 9.

An operation example of the lighting circuit of the lighting circuit board 7 will be described. This lighting circuit controls the lighting of the semi-hot fluorescent tube 3 and the auxiliary light bulb 4 in accordance with an operation of a light sensor (not shown) for detecting external brightness or a user. In other words, the semi-hot fluorescent tube 3 is lit at the highest luminance during the daytime when the external background is extremely bright. At this time, the auxiliary light bulb 4 may also be turned on at the same time with high luminance to supplement the luminance. However,
If the background is not very bright even in the daytime,
Is turned off, and the brightness of the semi-hot fluorescent tube 3 is reduced to some extent. Further, at night or the like when the external background is dark, the semi-hot fluorescent tube 3 is turned off, and only the auxiliary light bulb 4 is turned on. Further, the auxiliary light bulb 4 appropriately adjusts the lighting luminance according to the darkness of the external background.

According to the backlight 2 having the above-described structure, high-brightness illumination can be performed using the semi-hot fluorescent tube 3 in the daytime or the like. In addition, the display brightness of the display device 1 does not become too low to make it difficult to see. In addition, since low-luminance display can be performed using the auxiliary light bulb 4 at night or the like, the display device 1 is used as in the case where the semi-hot fluorescent tube 3 is used alone.
Does not cause the display background to be too high to make a dark background difficult to see. In addition, since the semi-hot fluorescent tube 3 can be as small as a cold cathode fluorescent tube, there is no possibility that the display device 1 becomes large as in the case of using a hot cathode fluorescent tube. Also, since the auxiliary light bulb 4 only needs to be able to emit light with low luminance, an extremely small one is sufficient, and
Not only does not press the space, but also does not cause excessive heat generation at the time of light emission as in the case of using a xenon bulb alone.

Further, according to the backlight 2, since two types of light sources, that is, the semi-hot fluorescent tube 3 and the auxiliary light bulb 4, are used, the emission colors of these can be changed. For example,
A fluorescent material that emits green light is used for the semi-hot fluorescent tube 3,
If the auxiliary light bulb 4 is colored so as to emit orange light, a clear green display is performed during the day, and an orange display without irritating the eyes can be performed at night.

In the backlight 2 of the above embodiment, one semi-hot fluorescent tube 3 and two auxiliary light bulbs 4 are used, but the number thereof is arbitrary. Further, in the above embodiment, the lighting circuits of the semi-hot fluorescent tube 3 and the auxiliary light bulb 4 each have a dimming function, but any one or both of the lighting circuits may have no dimming function. Furthermore, the lighting circuit does not necessarily need to be an inverter circuit, and the dimming can be performed by controlling the phase of a thyristor or the like.

Further, in the above-described embodiment, the auxiliary light bulb 4 is used as the auxiliary light source. However, if the auxiliary light source can emit light at a luminance lower than the minimum luminance of the semi-hot fluorescent tube 3, at least.
Not limited to such a heat bulb, any light source can be used. That is, for example, a cold-cathode fluorescent tube or a hot-cathode fluorescent tube can be used as an auxiliary light source if it is used at a low luminance by a dimming function. In this case, the hot-cathode fluorescent tube is used to supplement the semi-hot fluorescent tube 3, so that the hot-cathode fluorescent tube can be much smaller than that used alone. If an LED (light emitting diode) is used, an auxiliary light source that is smaller than the auxiliary light bulb 4 and generates less heat can be provided.

Furthermore, in the above embodiment, the display device 1 for mounting on a car has been described, but the present invention is not limited to this.
The present invention can be similarly applied to the display device 1 for any use.

[0027]

As is apparent from the above description, according to the display device of the present invention, during the daytime when the external background is bright, the semi-hot fluorescent tube can be turned on to display high brightness, and the background is dark. At night, by turning off the semi-hot tube and turning on the auxiliary light source with low luminance, it is possible to prevent the background from being too bright and making it difficult to see the background.

[Brief description of the drawings]

FIG. 1 illustrates one embodiment of the present invention, and is an overall perspective view of a backlight of a display device.

FIG. 2, showing an embodiment of the present invention, is an assembled perspective view showing a backlight fixing member and a lighting circuit board.

FIG. 3, showing an embodiment of the present invention, is an assembled perspective view showing a state in which a lighting circuit board is fixed to a fixing member of a backlight.

FIG. 4 is a perspective view showing an embodiment of the present invention, and is an assembled perspective view showing a reflector of a backlight.

FIG. 5 is a side view showing an example of use of the display device.

FIG. 6 is a side view illustrating a configuration of a display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 display device 2 backlight 3 semi-hot fluorescent tube 4 auxiliary light bulb 7 lighting circuit board 11 combiner 14 liquid crystal display device

Claims (2)

[Claims] 1. A display device in which light from a backlight passes through a display device and is reflected by a combiner so that an image of the display device is displayed as a distant virtual image on a background of the combiner. A display device comprising: a semi-hot fluorescent tube that emits light at a luminance; and an auxiliary light source capable of at least lighting at a low luminance is additionally provided. 2. The semi-hot fluorescent tube and an auxiliary light source,
The display device according to claim 1, wherein the light is adjusted to each individual luminance by an individual dimming circuit.