JP3000560U - Color liquid crystal display - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a color liquid crystal display device capable of suppressing a decrease in contrast ratio without causing a change in color tone even when used in a bright place such as outdoors in the daytime. [Structure] A light source for a backlight of a color liquid crystal panel 1 is configured by a combination of two types of three-wavelength fluorescent lamps 2 and 3 having emission wavelength characteristics different from each other, and the two types of three-wavelength fluorescent lamps 2 and 3 are selected. A selection means 4 for driving the color liquid crystal panel 1 is provided so that the color liquid crystal panel 1 can be irradiated with a backlight having a wavelength spectrum according to the usage environment.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a so-called transmissive color liquid crystal display device including a color liquid crystal panel and a light source for backlight.

[0002]

[Prior art]

 In a transmissive color liquid crystal display device that includes a color liquid crystal panel and a backlight light source that illuminates the backlight from behind, a three-wavelength fluorescent lamp is generally used as the backlight light source.

The three-wavelength fluorescent lamp is a fluorescent lamp having a narrow strong emission band in each wavelength region of blue, green, and red, and is a light source excellent in color rendering when used indoors. The emission wavelength characteristics are set.

[0004]

[Problems to be solved by the device]

 By the way, the three-wavelength fluorescent lamp used as the light source for the backlight of the conventional color liquid crystal display device as described above places importance on the color rendering property in a relatively dark room. If a color liquid crystal display device that uses as a light source for a backlight is used outdoors as it is during the daytime, the display will differ from the color tone inside the room due to changes in the sensitivity characteristics of the human eye. There is also a problem that the brightness becomes low and the light utilization efficiency as a backlight deteriorates.

That is, FIG. 4 is a graph showing the relationship between the human eye's visual sensitivity and wavelength, where the broken line shows scotopic vision and the solid line shows photopic vision. The sensitivity characteristics to the wavelength of light change in a bright place. Therefore, a color liquid crystal display device that uses the output light from a conventional three-wavelength fluorescent lamp as a backlight, which emphasizes the sensitivity characteristics of the human eye in a relatively dark place, was used in a bright place such as outdoors in the daytime. In this case, the brightness of the blue color is relatively reduced and the color tone is greatly changed compared with the case of viewing in a dark room, etc., and the overall brightness is also reduced.

[0006] In addition, there is a problem that the external (sun) light is reflected on the screen in the daytime and the contrast ratio of the screen is deteriorated. That is, the contrast ratio is represented by {(display light brightness + background light brightness) / background light brightness}, but the contrast ratio deteriorates due to an increase in background light brightness due to reflection of external light on the display screen. At the same time, in the conventional display device, assuming that the brightness of white is 1, the ratio of red, green and blue is 0.3: 0.6: 0.1, which is more red and blue than green. Since the brightness of the image is originally low, the contrast ratio of red and blue decreases significantly in the daytime. For this reason, the appearance of red and blue becomes much worse in the daytime than in green, and that tendency is especially noticeable for blue, and blue is barely visible outside during the daytime.

The present invention has been made in view of the above circumstances, and a color liquid crystal display capable of suppressing a decrease in contrast ratio without causing a large change in color tone even when used outdoors in the daytime. The purpose is to provide the device.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the color liquid crystal display device of the present invention uses light sources for backlight of the color liquid crystal panel 1 having different emission wavelength characteristics, as shown in FIG. It is characterized in that it is configured by a combination of three kinds of three-wavelength fluorescent lamps 2 and 3, and that a selection means (for example, a manual changeover switch 4) for selectively driving the two kinds of three-wavelength fluorescent lamps 2 and 3 is provided. .

Here, all of the three strong emission bands of blue, green and red of the three-wavelength fluorescent lamp 2 of one of the two three-wavelength fluorescent lamps 2 and 3 are set to the other three-wavelength fluorescent lamp. It is desirable to shift to the longer wavelength side than the three strong emission bands of 3.

More specifically, the strong emission wavelength band of one of the three-wavelength fluorescent lamps 2 is set within the ranges of 450 to 500 mμ, 530 mμ to 580 mμ and 600 to 650 mμ, and the strong wavelength band of the other three wavelength fluorescent lamp 3 is set. The emission wavelength band is preferably in the range of wavelengths 400 to 450 mμ, 490 to 550 mμ and 580 to 620 mμ.

Further, it is more preferable that the total brightness of one of the three-wavelength fluorescent lamps 2 is higher than the total brightness of the other three-wavelength fluorescent lamp 3. Furthermore, the conventional luminance ratio of red: green: blue is 0. It is even better to increase the luminance ratio of red and aono relatively from 3: 0.6: 0.1.

As the drive selection means for the two types of three-wavelength fluorescent lamps 2 and 3, in addition to the manual changeover switch 4 operated by the user, as shown in FIG. 2, a switch near the display surface of the liquid crystal display panel 1 is used. Based on the output from the external light sensor 6 provided, a function of turning on one of the three-wavelength fluorescent lamps 2 which is a fluorescent lamp having a long-wavelength side emission characteristic is provided only when the intensity of external light is a predetermined value or more. An automatic selection circuit that has can be adopted.

Further, when the automatic selection circuit is adopted, when the external light intensity based on the output of the external light sensor 6 becomes equal to or higher than a predetermined value, only one of the three-wavelength fluorescent lamps 2 is turned on and the other of the three-wavelength fluorescent lamps is turned on. In addition to the operation of turning off the light lamp 3, the lighting circuit of each of the three-wavelength fluorescent lamps 2 and 3 is of an inverter type, and based on the output from the outside light sensor 6, the other of the other lights until the outside light intensity reaches a predetermined value. The brightness of the three-wavelength fluorescent lamp 3 is increased substantially in proportion to the intensity of outside light, and after reaching a predetermined value, one of the three-wavelength fluorescent lamps 2 is turned on while the other three-wavelength fluorescent lamp 3 is turned on. Then, it is preferable to control each lighting circuit so that its intensity is increased substantially in proportion to the intensity of outside light, because the optimum display can be performed according to the usage environment of the display device.

According to the present invention, the backlight light source is not one of the two types of three-wavelength fluorescent lamps but one type of three-wavelength fluorescent lamp, and the strong emission wavelength band is 450 to 500 mμ. Including those having respective ranges of 530 mμ to 580 mμ and 600 to 650 mμ, this configuration is also effective for a color liquid crystal display device mainly used in the daytime.

[0015]

[Action]

 The present invention makes it possible to use a backlight having wavelength characteristics suitable for the environment in which the display device is used, in consideration of changes in luminosity in the dark and bright places of the human eye.

That is, the three-wavelength fluorescent lamps 2 and 3 having two types of emission wavelength characteristics are provided as the light source for the backlight, and the three-wavelength fluorescent lamps can be selectively turned on and driven, so that the operating environment of the display device can be changed. It is possible to display more excellently in color rendering, brightness and contrast ratio.

As shown in FIG. 4, the wavelength-luminous sensitivity characteristics of the human eye in the daytime and the nighttime are moved parallel to the long wavelength side as a whole in the daytime as compared with the nighttime. It is preferable to shift each of the three strong emission bands of one of the three-wavelength fluorescent lamps 2 as a light source for light to a longer wavelength side than each of the strong emission bands of the other three-wavelength fluorescent lamp 3 for night light. Specifically, by setting each strong emission wavelength band of each three-wavelength fluorescent lamp within each of the above-mentioned ranges, optimum display is possible both during the day and at night.

If the total brightness of one of the three-wavelength fluorescent lamps 2 selected in the daytime is made higher than the total brightness of the other three-wavelength fluorescent lamp 3, deterioration of the contrast ratio during the daytime is suppressed. Has an effect on.

Then, one of these two types of three-wavelength fluorescent lamps 2 and 3 is selected based on the magnitude of the output of the ambient light sensor 6 arranged near the liquid crystal display panel. Alternatively, if the brightness of each of the three-wavelength fluorescent lamps 2 and 3 is continuously changed, the backlight is automatically adjusted so that a good display is always performed according to the intensity of the ambient light in which the display device is placed. The wavelength characteristics of will change.

In a color liquid crystal display device that is mainly used outdoors during the daytime, as a light source for a backlight, there is a daytime light source having the above-mentioned wavelength characteristic in which the strong emission band is shifted to a relatively long wavelength side. It is sufficient to use only the three-wavelength fluorescent lamp 2.

[0021]

【Example】

 FIG. 1 is a schematic view showing the structure of the main part of an embodiment of the present invention, and is an exploded perspective view of the structure of the main part of the apparatus and a block diagram showing the circuit structure of the main part.

The color liquid crystal panel 1 is, for example, a known one mainly including a liquid crystal cell and a mosaic filter of three primary colors. Behind it, two types of three-wavelength fluorescent lamps for daytime and nighttime are used as a light source for backlight. Alternating twos and twos are supported in a suitable case (not shown).

The strong emission wavelength band of the three-wavelength fluorescent lamp 2 for daytime is within each range of 450 to 500 mμ, 530 mμ to 580 mμ and 600 to 650 mμ, and the strong emission of the three-wavelength fluorescent lamp 3 for nighttime is used. The wavelength band is in each range of 400 to 450 mμ, 490 to 550 mμ and 580 to 620 mμ. Further, the total brightness of each of the three-wavelength fluorescent lamps 2 for the daytime is higher than the total brightness of each of the three-wavelength fluorescent lamps 3 for the nighttime.

The daytime and nighttime three-wavelength fluorescent lamps 2 and 3 are respectively connected to separate lighting circuits 20 to 30, and each of the lighting circuits 20 and 30 includes a manual changeover switch 4 The power from the power supply circuit 5 is supplied only to the side selected by.

When using the embodiment of the present invention as described above, when used outdoors in the daytime, the three-wavelength fluorescent lamp 2 for the daytime is turned on, and the intensity of external light at night or in a relatively dark room is low. When flying in the state, the switch 4 is operated so that the three-wavelength fluorescent lamp 3 for night is turned on. As a result, the emission wavelength of the backlight is shifted to the long wavelength side in the daytime as compared to that in the nighttime, and the light of the wavelength corresponding to the difference in the sensitivity characteristics of the human eye between the bright and dark places shown in FIG. As a result of the irradiation of the color liquid crystal panel 1, the change in color tone between daytime and nighttime is suppressed, and at the same time, the light utilization efficiency is improved. Further, since the total brightness of the backlight in the daytime is higher than that in the nighttime, it is possible to suppress the decrease in the contrast ratio due to the increase in the background light due to the reflection of the external light on the display surface.

FIG. 2 is a schematic view showing the configuration of the main part of another embodiment of the present invention. In this example, the color liquid crystal display panel 1, the three-wavelength fluorescent lamps 2 and 3 for daytime and nighttime are exactly the same as those in the example of FIG. 1, but the three-wavelength fluorescent lamps 2 and 3 for daytime and nighttime are used. The lighting method and the selection method are characterized.

That is, in this example, as the lighting circuits of the three-wavelength fluorescent lamps 2 and 3, the inverter lighting circuits 21 and 31 respectively connected to the power supply circuit (not shown) are adopted, and An external light sensor 6 for monitoring the intensity of external light is arranged near the display screen of the liquid crystal panel 1. Then, the output of the external light sensor 6 is taken into the controller 7, and the controller 7 controls each inverter lighting circuit 21 and 31 based on the output of the external light sensor 6 to show the following. As described above, the three-wavelength fluorescent lamps 2 and 3 for daytime and nighttime are driven and controlled.

FIG. 3 is a graph showing an example of controlling the turning on / off of the three-wavelength fluorescent lamps 2 and 3 for daytime and nighttime and the total brightness by the controller 7, and showing the external light intensity based on the output of the external light sensor 6. Accordingly, the brightness of each of the three-wavelength fluorescent lamps 2 and 3 in the on / off state and the lit state is controlled. In this control example, only the three-wavelength fluorescent lamp 3 for night is turned on until the external light intensity reaches the predetermined value A, and the total brightness is increased substantially in proportion to the external light intensity. After reaching a predetermined value A, in addition to this, the three-wavelength fluorescent lamp 2 for daytime is turned on, and the total brightness thereof is increased substantially in proportion to the external light intensity. The total brightness of the nighttime three-wavelength fluorescent lamp 3 reaches the maximum brightness immediately before the outside light intensity reaches the predetermined value A.

According to the control method as described above, the wavelength characteristic of the backlight changes automatically in accordance with the sensitivity change of the human eye according to the external light intensity in the environment where the color liquid crystal display device is placed. In addition, the total brightness of the backlight changes according to the intensity of external light. Therefore, whether it is used in an extremely dark place, a place with some outside light such as indoors, or a place where sunlight is present such as outdoors during the day, the change in color tone is suppressed and In comparison, the change in contrast ratio is smaller.

It should be noted that it is also possible to adopt a method of automatically driving and controlling the three-wavelength fluorescent lamps 2 and 3 for daytime and nighttime by the external light sensor 6 and the controller 7 so as not to control the brightness. it can. In this case, for example, until the outside light intensity reaches the predetermined value A, only the three-wavelength fluorescent lamp 3 for night is turned on, and after reaching the predetermined value A, the three-wavelength fluorescent lamp 2 for daytime is additionally used. It may be turned on, or only the three-wavelength fluorescent lamp 2 for daytime may be turned on.

Further, in a color liquid crystal display device which is mainly used in a bright place, only the three-wavelength fluorescent lamp 2 for daytime having the above-mentioned wavelength characteristic can be provided as a light source for back light. In this case, only the backlight that matches the photopic luminosity will be available, and the light utilization efficiency will decrease when used in a dark place such as indoors, but a color liquid crystal display that is used outdoors during the daytime, etc. Effective for equipment.

[0032]

[Effect of device]

 As described above, according to the present invention, two kinds of three-wavelength fluorescent lamps having different wavelength characteristics are provided as the light source for the backlight in the color liquid crystal display device, and they are selectively turned on. This means that it is possible to select a backlight that is more suitable for the sensitivity characteristics of the human eye, depending on the external light conditions in the environment where the display device is placed. Compared with other display devices, it is possible to suppress changes in color tones in dark and bright places, improve the efficiency of using light as a backlight, and to obtain the same visibility in the daytime. The required backlight power can be reduced.

In addition, by setting the total brightness of one of the two types of three-wavelength fluorescent lamps having a long-wavelength emission characteristic for daytime to be higher than that of the other side, sunlight or the like can be displayed on the screen. Even when used in a reflective environment, deterioration of the contrast ratio can be suppressed.

Furthermore, if an external light sensor is provided in the vicinity of the display surface and a circuit for selectively turning on two types of three-wavelength fluorescent lamps based on the magnitude of the output thereof is provided, the external light sensor automatically operates according to the usage environment. A color liquid crystal display device capable of performing optimal display can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main configuration of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a main part configuration of another embodiment of the present invention.

FIG. 3 is a graph showing an example of control of the three-wavelength fluorescent lamps 2 and 3 by a controller 7 in the embodiment of FIG.

FIG. 4 is a graph showing the relationship between the visual sensitivity of human eyes and the wavelength in a dark place and a bright place.

[Explanation of symbols]

 1 Color liquid crystal panel 2 Three-wavelength fluorescent lamp for daytime 3 Three-wavelength fluorescent lamp for nighttime 4 Manual changeover switch 5 Power circuit 6 External light sensor 7 Controller 20,30 Lighting circuit 21,31 Inverter lighting circuit

Claims (6)

[Scope of utility model registration request] 1. A transmission type color liquid crystal display device comprising a color liquid crystal panel and a light source for backlight, wherein the light source for backlight is constituted by a combination of two kinds of three-wavelength fluorescent lamps having emission wavelength characteristics different from each other. In addition, the color liquid crystal display device is provided with selection means for selectively driving the two types of fluorescent lamps. 2. Each of the three strong emission bands of blue, green, and red of one three-wavelength fluorescent lamp of the two types of three-wavelength fluorescent lamps is three strong emission bands of the other three-wavelength fluorescent lamp. The color liquid crystal display device according to claim 1, wherein the color liquid crystal display device is deviated to a longer wavelength side. 3. The strong emission wavelength band of the one three-wavelength fluorescent lamp is in each range of 450 to 500 mμ, 530 mμ to 580 mμ and 600 to 650 mμ, and the strong emission wavelength band of the other three wavelength fluorescent lamp is 400-450mμ, 4
The color liquid crystal display device according to claim 2, wherein the color liquid crystal display device is in the range of 90 to 550 mμ and 580 to 620 mμ. 4. The color liquid crystal display device according to claim 2, wherein the total brightness of the one three-wavelength fluorescent lamp is higher than the total brightness of the other three-wavelength fluorescent lamp. 5. The selection means is an automatic selection circuit,
This automatic selection circuit turns on the one of the three-wavelength fluorescent lamps only when the intensity of the external light is a predetermined value or more based on the output from the external light sensor provided near the display surface of the liquid crystal panel. The color liquid crystal display device according to claim 1, 2, 3, or 4. 6. The lighting circuit of each of the three-wavelength fluorescent lamps is an inverter type, and the automatic selection circuit is configured to perform the other operation until the external light intensity reaches the predetermined value based on the output from the external light sensor. While increasing the brightness of the three-wavelength fluorescent lamp of the above mentioned in proportion to the intensity of external light, after reaching the above predetermined value,
While the other three-wavelength fluorescent lamp is turned on, the other three
6. The color liquid crystal display device according to claim 5, wherein each of the lighting circuits is controlled so that the wavelength fluorescent lamp is turned on and the intensity thereof is increased substantially in proportion to the intensity of external light.