JPH1031212A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to supply a bright TV image with less luminance unevenness, to facilitate the light source exchange, and to make it possible to use a light source easy to obtain, by setting up a circular fluorescent lamp as a light source for backlight. SOLUTION: This device consists of a liquid crystal display panel 11, a frame body part 12, a base part and a back surface part 14. The liquid crystal display panel 11 is a liquid crystal display body of a light transmission type, and performs a picture display by transmitting the light of the light source consisting of the circular fluorescent lamp provided on the back surface part 14. The back surface part 14 is attached pivotally to the base part below the frame body part 12 attachably/detachably, and is constituted so as to be opened/closed in the arrow direction as shown by a broken line in figure. Plural pieces of circular fluorescent lamps 15 with different sizes are arranged concentrically opposite to the back surface of the panel 11. Respective fluorescent lamps are fixed by a back surface cover 16 having a function of a white or silver reflection plate. A power source 17 of a circular fluorescent lamp lighting stabilizer is arranged below the back surface part 14. Although the power source 17 adopts an inverter type, the center of gravity of the device is lowered because of lower arrangement and the base part is stabilized since a heavy transformer is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display, and more particularly to a backlight.

[0002]

2. Description of the Related Art In recent years, as liquid crystal display devices, display devices such as word processors and personal computers have been frequently used. It has also been used as a display of a TV receiver, and the capacity of the display screen has been increased as in a conventional TV receiver of a Bran tube.

In a liquid crystal display device, an optical shutter is provided by a liquid display panel in which a liquid crystal layer is sandwiched between two sheets of glass.

As a light source, a cold cathode discharge tube is often used for OA because of its long life. Since the cold cathode discharge tube has a lower light emission brightness than a hot cathode tube called a normal fluorescent lamp, it is not suitable for a liquid crystal display device for TV use. Therefore, there is a liquid crystal display device provided with a hot cathode tube, which is a fluorescent lamp for general household use, on the back surface.

[0005] However, the life of the hot cathode tube is short, and the life of the cold cathode tube is 10,000 hours (average value from the initial state to a half reduction in brightness at normal temperature continuous lighting), while that of the hot cathode is 3000 hours under the same conditions. Assuming that the lighting is performed for 8 hours a day, the life of the cold cathode is 3 years and 3 months, and the life of the hot cathode is 1 year. Conventional CRT TV receivers are generally used for more than 10 years, so the life of the liquid crystal display device depends on the light source, and the light source needs to be replaced.

Further, in a backlight in which straight tube fluorescent lamps are arranged, as shown in FIG. 3B, vertical (horizontal) luminance unevenness 22b is generated on the screen, making it difficult to see, and even slight luminance unevenness is noticeable. Was the current situation.

[0007]

SUMMARY OF THE INVENTION T using a liquid crystal display
In the V image receiver, the luminance is deteriorated by the life of the light source, and the light source needs to be replaced. An object of the present invention is to provide a liquid crystal display device that includes a bright light source, supplies a TV image with less bright luminance unevenness, facilitates light source replacement in ordinary households, and uses a light source that is easily available.

[0008]

According to the present invention, there is provided a liquid crystal display device having a backlight on the back side of a screen of a liquid crystal display panel, wherein a ring type fluorescent lamp is installed as a light source of the backlight. Get the device.

In the case where a plurality of conventional straight tube fluorescent lamps are used, uneven brightness due to variations in each fluorescent lamp and uneven brightness due to uneven life are eliminated. The brightness unevenness caused by the straight tube fluorescent lamp is such that only a part of the screen becomes dark, and when the fluorescent tube is replaced due to the life of one fluorescent lamp, the brightness unevenness must be made unless all other fluorescent tubes are newly renewed. Occurs. However, in the case of a ring-type fluorescent tube, since brightness unevenness occurs in a ring from almost the center of the rain surface, the conventional cathode ray tube T
As in the case of the curved display surface of V, luminance unevenness is less likely to be perceived.

Further, the present invention provides a liquid crystal display device characterized in that a power supply for lighting a ring-shaped fluorescent lamp is installed in a lower part of a screen of a liquid crystal display panel.

[0011] The brightness unevenness caused by the straight tube fluorescent lamp is such that only a part of the screen becomes dark, and when the fluorescent tube is replaced due to the life of one fluorescent lamp, all other fluorescent tubes are not renewed. And uneven brightness. However, in the case of a ring-type fluorescent tube, luminance unevenness occurs annularly from substantially the center of the rain surface, so that it becomes difficult to feel the luminance unevenness like the curved display surface of a conventional cathode ray tube TV.

Further, a liquid crystal display device is provided in which a plurality of ring-shaped fluorescent lamps are installed in substantially concentric circles so that the sockets of the ring-shaped fluorescent lamps are not overlapped on the concentric circles. As a result, unevenness in brightness due to variations in the fluorescent lamps of the plurality of ring-shaped fluorescent lamps and variations in the life can be made less likely to be felt as described above. Further, even when replacing the fluorescent lamp due to deterioration of one lamp, it is possible to provide a screen without a sense of incongruity without changing other lamps.

Further, the present invention provides a liquid crystal display device characterized in that the annular fluorescent lamp is fixed to a back cover of a liquid crystal display panel. By installing a power source such as a ballast for lighting on the leg portion of the liquid crystal display device or the lower portion of the screen instead of the back surface of the liquid crystal display screen, the weight and center of gravity of the liquid crystal display device itself is reduced to prevent the liquid crystal display device from overturning. Since the liquid crystal display panel made of glass occupies a majority of the weight of the liquid crystal display device, it is a countermeasure against breakage due to overturning and scattering of glass.

Further, the liquid crystal display device is characterized in that the back cover is detachable from the panel, can be washed with water, and reflects the light of the fluorescent lamp toward the liquid crystal screen.
By fixing the ring-shaped fluorescent lamp to the back cover of the liquid crystal display device, the backlight as the liquid crystal display device can be easily replaced, and the lifetime of the liquid crystal display device caused by the backlight can be ignored.

Since the back cover can be detached independently of the liquid crystal display panel, the fluorescent lamp can be replaced separately from the liquid crystal display device. Also, since the back cover is a light reflection plate, it is easy to replace only the cover due to dirt or the like. If the back cover can be removed, it can be washed in water, and by turning the fluorescent lamp side white or silver to reflect the light of the fluorescent lamp toward the liquid crystal screen,
Since it is used as a reflector, much of the total light emitted from the fluorescent lamp can be radiated toward the front liquid crystal display panel, and efficient power consumption can be achieved.

Further, the power supply is an inverter, and a liquid crystal display device characterized by having means for adjusting synchronization with the driving frame frequency of the screen of the liquid crystal display panel is obtained.

Since the synchronization between the driving frame frequency of the liquid crystal display device and the lighting frequency of the fluorescent lamp can be adjusted, flickering and wavy display called flicker due to frequency moire can be eliminated. For dimming with backlight of brightness,
The frequency can be set so as to avoid moiré due to the synchronization.

Still another object of the present invention is to provide a liquid crystal display device characterized in that a power source can individually adjust the brightness of a plurality of ring-shaped fluorescent lamps. By this. The luminance variation of each ring-shaped fluorescent lamp due to deterioration can be adjusted.

Further, in the liquid crystal display device according to the present invention, the replacement of the light source at home is facilitated, and the replacement light source is easily available.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

FIG. 1 shows an embodiment of the present invention.
As shown in FIG. 1A, the liquid crystal display device 10 includes a liquid crystal display panel 11, a frame 12, a base 13 and a back surface 14.

The liquid crystal display panel 11 is a light transmissive liquid crystal display, and performs screen display by transmitting light from a light source composed of an annular fluorescent lamp provided on the back surface portion 14.

The back portion 14 is provided on the base 13 below the frame 12.
, So that it can be opened and closed in the direction of the arrow as shown by the broken line in the figure.

A plurality of ring-shaped fluorescent lamps 15 of different sizes are concentrically arranged facing the back of the panel 11.
Each fluorescent lamp is fixed by a back cover 16 also serving as a white or silver reflector. The size of the fluorescent lamp is, for example, 40
W type 151, 32W type 152, and 30W type 153 are arranged in order from the outer periphery. Since the socket 15A formed in a part of the ring-shaped fluorescent lamp creates a local shadow on the backlight,
As shown in (b), the socket positions of the three lamps are dispersed and arranged at intervals of, for example, 90 °. Further, the light quality of the ring-shaped fluorescent lamp is preferably a three-wavelength type having at least red, purple and blue colors so as to be suitable for color display.

A power supply 17 for a ring-shaped fluorescent lamp lighting ballast is disposed below the rear portion 14. The power supply is an inverter type,
Due to the heavy transformer, the lower arrangement lowers the center of gravity of the device and stabilizes the platform 13.

FIG. 2 shows three types of fluorescent lamps 1 shown in FIG.
5 shows a configuration of the inverter type power supply 17 for the fifth embodiment.

The power supply 17 for each lamp converts a direct current into a high frequency of 10 KHz or more and supplies it to the fluorescent lamp, and comprises a rectifier 18 for converting a commercial power into a direct current and an inverter 19. The inverter is composed of the transistor 191 and the transformer 19
2 which receives a horizontal or vertical synchronizing signal from the TV circuit 20 and oscillates at a synchronized high frequency in accordance with an output from an adjuster 21 which outputs a pulse signal whose pulse frequency can be adjusted.

Thus, the light is turned off during the blanking period of the TV signal, thereby eliminating the difficulty of viewing the panel screen due to the flicker of the luminance of the light source. This is the same for the power supplies of other fluorescent lamps.

Further, when the luminance of the ring-shaped fluorescent lamp varies due to replacement of individual fluorescent lamps, or when there is a relative change in the luminance between each lamp in use, the output of each power supply is changed. Adjust to balance the brightness so as to prevent uneven brightness.

FIG. 3A shows a tendency of uneven brightness 22a generated when a plurality of annular fluorescent lamps are arranged concentrically.
As with the curved screen on the cathode-ray tube display surface, uneven brightness is not easily felt.

Further, by molding the back cover with a synthetic resin such as polycarbonate so as to be washable with water, it is possible to prevent luminance deterioration due to dirt on the reflecting wall.

FIG. 4 shows another embodiment of the present invention. The light diffusion plate 22 is disposed between the rear surface of the liquid crystal display panel 11 and the ring-shaped fluorescent lamp 15, and the reflection wall 16 </ b> A of the rear cover 16 is disposed apart from each fluorescent lamp 15, and the light in front of the fluorescent lamp is The light 23 is sufficiently diffused by the light diffusing plate 22, and the light 23 radiated behind the fluorescent lamp 15 is condensed and reflected on a low-luminance region by using the uneven surface 16B of the reflecting wall 16A. This arrangement can further reduce the luminance unevenness.

[0033]

According to the present invention, a bright light source can be provided, a display screen of a TV or a computer with less bright luminance unevenness can be supplied, and the light source can be easily replaced in a general home. A liquid crystal display device to be used can be obtained.

[Brief description of the drawings]

FIG. 1 shows a liquid crystal display device according to an embodiment of the present invention,
(A) is a cross-sectional view, (b) is a plan view of an f-back portion, (c) is a cross-sectional view taken along line AA of (b),

FIG. 2 is a schematic circuit diagram showing a power supply of a ring-shaped fluorescent lamp according to an embodiment of the present invention;

FIGS. 3A and 3B are plan views illustrating luminance unevenness of the present invention and a conventional liquid crystal display panel, respectively.

FIG. 4 is a sectional view of another embodiment of the present invention.

[Explanation of symbols]

 10: liquid crystal display device 11: liquid crystal display panel 12: frame 13: base 14: back 15: ring-shaped fluorescent lamp 16: back cover 17: power supply

Claims (7)

[Claims] 1. A liquid crystal display device having a backlight on the back side of a screen of a liquid crystal display panel, wherein a ring-type fluorescent lamp is installed as a light source of the backlight. 2. The liquid crystal display device according to claim 1,
A liquid crystal display device, wherein a power supply for lighting a ring-shaped fluorescent lamp is provided at a lower portion of a screen of a liquid crystal display panel. 3. The liquid crystal display device according to claim 1,
A liquid crystal display device comprising: a plurality of ring-shaped fluorescent lamps installed in substantially concentric circles such that sockets of the ring-shaped fluorescent lamps are not overlapped on the concentric circles. 4. The liquid crystal display device according to claim 1,
A liquid crystal display device wherein a ring-shaped fluorescent lamp is fixed to a back cover of a liquid crystal display panel. 5. The liquid crystal display device according to claim 4,
A liquid crystal display device wherein the back cover is washable and reflects light of a fluorescent lamp toward a liquid crystal screen. 6. The liquid crystal display device according to claim 2,
A liquid crystal display device comprising: an inverter as a power source; and means for adjusting synchronization with a driving frame frequency of a screen of a liquid crystal display panel. 7. The liquid crystal display device according to claim 2,
A liquid crystal display device wherein a power supply is capable of individually adjusting the brightness of a plurality of ring-shaped fluorescent lamps.