JP2000310778A - Back light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back light which has no restriction on frame narrowing and screen size. SOLUTION: This back light has at least more than one cylindrical light source arranged at the bottom part in a lamp house having the light reflection body on its bottom surface and a flat top opening and is equipped with a light transmitting diffusion body at the opening part of the lamp house. In this case, at least one cylindrical light source end part which is folded is held on the lamp house bottom part. Cylindrical light source end parts are made adjacent to each other and multiple cylindrical light sources are linearly arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight.

[0002]

2. Description of the Related Art A backlight used mainly for a liquid crystal display device has a thin light source such as a cold-cathode tube or heat source for a light source due to demands for a thin display, a large display screen, a high luminance, and low power consumption. The mainstream is to use a fluorescent tube such as a cathode tube, and the structure is such that an edge light type, in which a fluorescent tube is arranged on the side of the light guide plate and light is led out to the surface, and direct light from a lamp house containing the fluorescent tube It is roughly classified into a direct type that emits light through a transmission diffusion plate.

[0003] The backlight structure is selected according to the required performance of the product. The direct type has a higher light use efficiency than the edge light type, and is suitable for applications requiring high luminance such as monitors, televisions, and car navigation systems. It can be called a structure.

FIG. 9 shows the internal structure of a lamp house, and FIG. 10 shows the appearance of an assembly, for explaining the basic structure of a conventional direct type backlight.

[0005] The lamp house, which is the structural base of the backlight, is formed by processing a sheet metal having a reflecting surface formed by applying a high-reflection paint or pasting a high-reflection film material or a molding resin using a high-reflection grade into a box shape. Get it.

In particular, in the backlight shown in FIG. 9, a closed space is formed by bending an end of a sheet metal to which a high-reflection film is adhered to form a lamp house 2.

The end of the fluorescent tube 1a as a light source is fixed to a fluorescent tube support 5 obtained by injection molding of a high-reflection grade resin so as to be held at a position of about 1 to 2 mm above the lamp house 2. The number of lines to be arranged is determined by the required luminance.

The inverter circuit board 3a disposed on the back of the lamp house 2 to emit light from the fluorescent tube 1a is 50 to 7
An alternating voltage of about 0 kHz and about 1 to 2 kV is generated and applied to the fluorescent tube 1 a by the high-voltage cable 4.

By assembling the above-described components and disposing a light transmitting / diffusing plate 6 using a milky white acrylic material or the like on the upper surface, a backlight having the appearance shown in FIG. 10 is formed, and the backlight emitted radially from the fluorescent tube 1a. The light reaches the diffuser directly or after being reflected by the lamp house 2, and is converted into surface light by the diffuser.

An important factor in determining the display quality of a liquid crystal display device is the uniformity of the brightness of the backlight illuminated surface.

If there is a steep change in luminance on the illuminated surface, that part is visually recognized as luminance unevenness. Need to be designed to put.

First, both ends of the fluorescent tube 1a do not emit light. First, the fluorescent material becomes an impurity when the electrodes are sealed to both ends of the fluorescent tube, and a predetermined sealing strength cannot be secured. The need to exfoliate the body.

Secondly, mercury encapsulated as an ultraviolet ray generating substance necessary for light emission inside the fluorescent tube becomes a compound and adheres to the vicinity of the electrode, and the phosphor in this region loses its light emitting function with time. That is to be done.

For the above reasons, the ordinary fluorescent tube has a non-light emitting region at about 10 mm at each end.

The non-light-emitting area at the end of the fluorescent tube 1a shown in FIGS. 9 and 10 is accommodated within the width of the fluorescent tube support 5, and is designed to be placed outside the display area of the liquid crystal panel.

[0016]

There is a strong demand for a liquid crystal display device to have a small frame size regardless of the screen size and application.

In the conventional backlight shown in FIGS. 9 and 10, the non-light-emitting region at the end of the linear fluorescent tube 1a and the processing size of the high-voltage wire 4 are required to be at least 10 to 15 mm. There was a problem that it could not be reduced.

Further, in response to a demand for a larger screen size, the fluorescent tube cannot be made longer due to the limitation of manufacturing equipment and mechanical strength, and is set to a limit value at which a backlight of about 25 inches can be manufactured. Therefore, there is a problem that it is impossible to keep up with the enlargement of the screen size of the liquid crystal display device.

[0019]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying to solve the above problems, and relates to a method of using a backlight using a fluorescent tube whose end is bent.

First, in order to solve the problem that the non-luminous region of the fluorescent tube and the processing size of the wiring of the high-voltage cable are required and the frame of the liquid crystal display device cannot be reduced, at least one of the ends of the fluorescent tube is bent by a lamp. It is intended to provide a backlight which is held at the bottom of a house.

In order to avoid the problem that the fluorescent tube cannot be lengthened due to the limitation of manufacturing equipment and mechanical strength and cannot follow the enlargement of the screen size of the liquid crystal display, the bent ends of the fluorescent tube are arranged adjacent to each other. Another object of the present invention is to provide a backlight characterized in that a plurality of fluorescent tubes are arranged in a straight line.

[0022]

By introducing the backlight according to the present invention, a structure in which the non-light emitting area of the fluorescent tube and the wiring of the high-voltage cable can be routed on the back of the lamp house can be used, and the frame size of the liquid crystal display device can be reduced.

Further, since a plurality of fluorescent tubes can be connected without limitation without forming a non-light emitting area in the display area of the liquid crystal panel, any screen size can be accommodated.

[0024]

Embodiment 1 The present invention will be specifically described below with reference to the drawings.

Parts having the same functions as those of the conventional backlight shown in FIGS. 9 and 10 are denoted by the same reference numerals.

FIGS. 1 and 2 show an embodiment of a basic structure of the present invention in which a bent fluorescent tube end is held by a lamp house.

In order to obtain a backlight corresponding to a liquid crystal display device having a display area having a diagonal dimension of 18.1 inches, an aluminum material having a thickness of 1 mm is formed into a box shape so that the diagonal dimension at the bottom is 18.1 inches. 0.188m on bottom
The lamp house 2 was obtained by affixing a high-reflection white sheet made of a polyester material with a double-sided tape.

In order to arrange the cold cathode tube 1b having a diameter of 3 mm at a position 2 mm above the bottom surface of the lamp house 2, the end of the cold cathode tube 1b, that is, the electrode portion, having a diameter of 5 mm through which the electrode can penetrate to the rear surface, is previously placed in the lamp house 2. Holes are made by the number of electrodes,
The cold-cathode tube 1b is fixed by fitting a holding rubber 8 having both buffering and insulation properties into this hole.

The cold-cathode tube 1b to be disposed is a 324 mm-length straight tube, which is heated at 17 mm from both ends and bent at a right angle in the same direction to form a central light-emitting region of 290 m.
m, and eight of them were arranged at a pitch of 50 mm in the long side direction of the lamp house 2.

An inverter circuit board 3a is fixed to the back of the lamp house 2 to supply power necessary for lighting the cold cathode tubes 1b.
A plastic protective case 9 is attached to protect the electrode part b.

By arranging a light transmission / diffusion plate on the upper surface of the basic structure described above in the same manner as a conventional backlight, the light transmission / diffusion plate emits surface light, and a backlight having the same optical performance as the conventional one can be obtained. Was.

In the backlight of this embodiment, the frame width of the long side is substantially 1 mm of the thickness of the lamp house from the conventional product of 15 mm.
mm, which is extremely effective in reducing the frame size.

[0033]

Embodiment 2 FIG. 3 shows an embodiment in which a plurality of cold cathode tubes are arranged in a straight line with bent ends of the cold cathode tubes adjacent to each other.

Example 1 In order to obtain a backlight corresponding to a liquid crystal display device having a display area having a diagonal dimension of 32 inches, a 1 mm thick aluminum material was machined into a box shape so that the diagonal dimension at the bottom became 32 inches. Thickness on the bottom is the same as above.
The lamp house 2 was obtained by attaching a high-reflection white sheet of a 188 mm polyester material with a double-sided tape.

The method of holding and lighting the cold cathode tube is also described in the first embodiment.
In order to dispose the cold cathode tube 1b having a diameter of 3 mm at a position 2 mm above the bottom of the lamp house 2, the bottom hole of the lamp house 2 is provided and holding rubber is provided, and the inverter circuit board 3 a is fixed to the back of the lamp house 2. The structure is performed.

The cold-cathode tube 1b to be disposed is a tube having a total length of 354 mm, which is subjected to a heat treatment at 17 mm from both ends and bent at a right angle in the same direction to form a central light-emitting region of 320 m.
m, which were arranged in two rows so that the tube axis was linear in the long side direction and eight rows at a pitch of 68 mm in the short side direction.

The distance between the cold cathode tubes 1b in which the electrode portions are arranged adjacent to each other in the long side direction is 3 mm.
Cold cathode fluorescent lamp 1b due to the diffusion effect of the light transmitting diffusion plate
The joint between the two could not be recognized, and a backlight having the same optical performance as the conventional one was obtained.

The backlight of this embodiment is characterized in that the non-light-emitting region of the light source is placed on the back of the lamp house, and a plurality of light sources are adjacent to each other as one long light source. It has become possible to provide a light-emitting surface of a size that could not be realized conventionally without loss.

[0039]

Embodiment 3 FIG. 4 shows an embodiment in which cold-cathode tubes whose ends are bent are superposed and arranged in the thickness direction of the backlight.

The basic structure is the same as that of the first embodiment,
This embodiment is characterized in that a plurality of cold cathode tubes are stacked.

The luminance of the backlight is determined by the number of light sources to be arranged. When high luminance is required, it is a general means to increase the number of light sources in the plane direction.

However, when the required brightness is not reached even when the light sources are laid, or when the lamp house is mechanically limited in the arrangement of the light sources like a waveform, the light sources are stacked in the thickness direction of the backlight. Need to be placed.

In the present embodiment, the cold cathode fluorescent lamps 1b are set to 3 mm apart from the structure of the first embodiment so that electric interference does not occur.
When the two layers were stacked with an interval of, it was possible to obtain about 1.7 times the luminance on the light transmitting diffusion plate.

The backlight of this embodiment can realize a high-luminance light-emitting surface with a small frame width, and the possibility of coping with ultra-high luminance for special use has been enhanced by increasing the number of steps.

[0045]

Embodiment 4 FIG. 5 shows an embodiment in which cold-cathode tubes emitting a plurality of types of single-wavelength light whose ends are bent are regularly arranged.

A general backlight used for a color liquid crystal display uses a phosphor that emits light of each wavelength of R (red), G (green), and B (blue) so as to react with a color filter formed on the liquid crystal panel side. Mixed three-wavelength fluorescent tubes are used.

The basic structure of this embodiment is similar to that of the second embodiment, in which the bent ends of the cold cathode tubes are adjacent to each other and a plurality of cold cathode tubes are arranged in a straight line. It is characterized in that a cold cathode tube 1c emitting single wavelength light of R, G, B is used instead of a cold cathode tube emitting light of wavelength.

In the present embodiment, R,
The cold-cathode tubes 1c having both ends emitting single-wavelength light of G and B are bent at regular intervals from corners of the lamp house 2 to R, G, B, R, G, B. In the adjacent rows, the arrangement pitch is shifted so that the cold cathode tubes of the same wavelength light are not adjacent to each other, and B, R, G, B, R, G,.
・ ・ It is lined up.

By repeating the above process, the cold cathode tubes 1c are arranged on the entire surface of the lamp house 2 and the light transmission / diffusion plate is disposed on the upper surface. Light is emitted.

By adjusting the power supplied to each cold-cathode tube emitting the same wavelength light by the inverter circuit board 3a,
This makes it possible to adjust the color tone of the illuminated surface of the direct-type backlight, which cannot be handled conventionally, and can contribute to the improvement of the image quality of the liquid crystal display.

[0051]

Embodiment 5 FIG. 6 shows an embodiment in which the lead wires of the cold-cathode tubes whose ends are bent are directly connected to the inverter circuit board.

The basic structure is the same as that of the first embodiment,
This embodiment is characterized in that power is supplied from the inverter circuit board 3a to the cold cathode tubes 1b by connecting lead wires directly to the inverter circuit board without using a high-voltage wire.

A frequency of 50 is used for lighting a general cold-cathode tube.
It is necessary to apply an AC voltage of up to 70 kHz and an effective value of 1 to 2 kV, and the power supply to the cold-cathode tube uses a silicone rubber-coated high withstand voltage wire having a small dielectric constant and excellent withstand voltage.

In order to efficiently transmit the electric power generated by the inverter circuit board to the cold-cathode tubes, it is necessary to connect the cold-cathode tubes and the inverter circuit board in the shortest possible distance. Since the portion faces the side of the backlight, the use of a high-voltage cable was indispensable for connection with the inverter circuit board fixed to the back.

The leakage current, that is, the power loss from the high-withstand-voltage wire is proportional to the wire length, and about 10% of the power may be lost depending on the specification.

In this embodiment, a pattern on the inverter circuit board is formed at a position where the end of the cold-cathode tube is located by using the end of the cold-cathode tube facing the back surface of the backlight. The power supply to the cold-cathode tube was made possible without using the.

In the trial production, when the through-hole was provided so that the lead wire of the cold-cathode tube 1b could be directly soldered to the inverter circuit board 3a and connected, an efficiency improvement of about 4% was realized, and the backlight was sufficiently effective in increasing the efficiency. It was recognized that there was.

[0058]

[Embodiment 6] FIG. 7 shows an embodiment in which a high reflection surface treatment is applied to a surface of an inverter circuit board, which is directly connected to a lead wire of a cold-cathode tube whose end is bent, and which faces the cold-cathode tube.

The basic structure is the same as that of the fifth embodiment.
This embodiment is characterized in that a high-reflection surface treatment is applied to one surface of the inverter circuit board 3a facing the cold cathode tube 1b to remove the lamp house from the constituent members.

In the fifth embodiment, a box-shaped lamp house made of an aluminum material, in which a high-reflection white sheet made of a polyester material is adhered with a double-sided tape, is used. Is highly involved.

Further, since the inverter circuit board fixed to the back of the lamp house generates a high voltage, a distance of 1 to 2 m is provided between the lamp house and the inverter circuit board to prevent discharge.
m is provided, and substantially 3 mm including the thickness of the lamp house is an increase in the product thickness not related to the basic performance.

In this embodiment, as an attempt to eliminate the need for a lamp house, a high-reflection white sheet made of polyester material is adhered to one side of the inverter circuit board facing the cold-cathode tube 1b with a double-sided tape, and the inverter circuit board 3 having a reflection function is used.
b.

In the fifth embodiment, the lamp house is formed in a box shape in order to keep the distance between the light transmitting / diffusing plate disposed on the upper surface and the reflecting surface or the cold cathode tube constant, but this embodiment corresponds to this. A frame 7 having the following dimensions is provided as a separate part.

In the 18.1 inch screen size prototype, the weight can be reduced by about 400 g, the thickness by 3 mm, and the member price by about 800 yen. By applying this, the product can be reduced in weight, thickness and cost. Can be expected.

In this embodiment, a white high-reflection sheet made of a polyester material is used as a means for providing a reflection function to the inverter circuit board. However, similar effects can be obtained by attaching a sheet of another material or printing a reflection material on the inverter circuit board. Needless to say, this is obtained.

[0066]

[Embodiment 7] Fig. 8 shows an embodiment in which the backlight described in Embodiments 1 to 6 is used as one unit and these are connected in a plane.

It has already been described that the conventional backlight cannot be lengthened due to the restrictions on the fluorescent tube manufacturing equipment and mechanical strength, and cannot follow the increase in screen size.

As one means for solving this problem, it is proposed to arrange a plurality of cold-cathode tubes whose ends are bent as described in the second embodiment in a straight line. However, if the screen size exceeds 40 inches, a lamp house or the like is required. However, there arises a problem that the processing of the mechanical parts cannot be handled due to the limitation of the processing equipment.

In this embodiment, the lamp house 2 is provided with a mechanism for connecting the lamp houses to each other, and a plurality of units are connected in a plane, and a frame 7 having a size corresponding to this is provided to cope with an increase in screen size. We propose a mechanism to do this.

For example, a 40-inch backlight can be easily obtained by connecting four 20-inch backlights.

Further, by using a small unit such as one or two cold cathode tubes as a standard part and connecting the required number of units, a member covering from a small screen to a very large screen can be shared.

[0072]

As described above, according to the present invention, the frame size of the liquid crystal display device can be reduced by holding at least one end of the fluorescent tube at the bottom of the lamp house.

Further, it is possible to adapt to any screen size by arranging the bent ends of the fluorescent tubes adjacent to each other and arranging a plurality of fluorescent tubes in a straight line.

[Brief description of the drawings]

FIG. 1 is a structural view of a backlight showing one embodiment of the present invention, and is a basic structural view in which a bent cold-cathode tube end is held at the bottom of a lamp house.

FIG. 2 is a structural view of a backlight showing one embodiment of the present invention, and is a basic cross-sectional structural view in which a bent cold-cathode tube end is held at the bottom of a lamp house.

FIG. 3 is a structural diagram of a backlight showing one embodiment of the present invention, and in particular, is a structural diagram of a backlight in which ends of cold-cathode tubes are adjacent to each other and are linearly arranged.

FIG. 4 is a structural diagram of a backlight showing one embodiment of the present invention, and in particular, is a structural diagram of a backlight in which cold cathode tubes are arranged so as to overlap in a thickness direction of the backlight.

FIG. 5 is a structural view of a backlight showing one embodiment of the present invention, and in particular, is a structural view of a backlight in which cold cathode tubes emitting a plurality of types of single wavelength light are regularly arranged.

FIG. 6 is a structural view of a backlight showing one embodiment of the present invention, and in particular, is a cross-sectional view of a backlight in which a lead wire of a cold cathode tube is directly connected to an inverter circuit board.

FIG. 7 is a structural view of a backlight showing one embodiment of the present invention, and in particular, is a structural view of a backlight in which a surface facing a cold cathode tube of an inverter circuit board is subjected to a high reflection surface treatment.

FIG. 8 is a structural diagram of a backlight showing one embodiment of the present invention, and in particular, is a structural diagram of a backlight in which a plurality of units are connected in a plane.

FIG. 9 is a basic structural diagram of a conventional backlight.

FIG. 10 is an external view of a conventional backlight, in particular, an external view of a backlight in which a light transmission / diffusion plate is disposed on an upper surface.

[Explanation of symbols]

 1a: Straight cold cathode tube 1b: Cold cathode tube with bent end 1c: Cold cathode tube emitting single wavelength light with bent end 2: Lamp house 3a: Inverter circuit board 3b: Provided with a reflection function on one side Inverter circuit board 4: High withstand voltage wire 5: Fluorescent tube support 6: Light transmission / diffusion plate 7: Frame 8: Holding rubber 9: Protective case

Claims (7)

[Claims] 1. A backlight having at least one or more cylindrical light sources disposed at the bottom of a flat lamp house having an upper opening having a light reflector at the bottom and a light transmitting diffuser at the opening of the lamp house. 3. The backlight according to claim 1, wherein the end of the cylindrical light source, at least one of which is bent, is held at the bottom of the lamp house. 2. The backlight according to claim 1, wherein bent ends of the cylindrical light sources are adjacent to each other, and a plurality of the cylindrical light sources are arranged in a straight line. 3. The backlight according to claim 1, wherein said cylindrical light sources are arranged in an overlapping manner. 4. The backlight according to claim 1, wherein cylindrical light sources emitting at least two or more types of single-wavelength light are alternately arranged. 5. The backlight according to claim 1, wherein a lead wire at an end portion of the cylindrical light source is directly connected to a wiring board disposed on a rear surface of the lamp house. 6. The backlight according to claim 5, further comprising: a wiring board in which all or a part of the lamp house is removed and a surface facing the cylindrical light source is subjected to a high reflection surface treatment. Light. 7. The backlight according to claim 1, wherein
A backlight, wherein the lamp house or the high-reflection surface-treated wiring board on which the cylindrical light source is arranged is connected in a plane.