JP2587777B2 - Backlight device for liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device for a liquid crystal display. More specifically, the present invention provides:
For example, the present invention relates to a backlight device of a liquid crystal display device having an elongated light source such as a fluorescent lamp.

[0002]

2. Description of the Related Art Liquid crystal display devices have been used as display devices for portable personal computers. Liquid crystal display devices used in portable personal computers must be very small. For this reason, the backlight device has been downsized. FIG.
1 schematically shows a conventional liquid crystal display device. The liquid crystal display device
It has a liquid crystal display unit 1, a backlight device 2, and polarizing plates 7 and 8. The liquid crystal panel 1 has two glass substrates 3 and 4, seals 5 and 6 are provided around these glass substrates, and a liquid crystal material is sealed between the two glass substrates. I have. On the inner surface of the glass substrate 3, a black matrix, a color filter, and the like are formed. On the inner surface of the glass substrate 4, gate lines are provided in the horizontal direction and data lines are provided in the vertical direction.
A liquid crystal display cell is provided at each intersection of the gate line and the data line. A gate line driver and a data line driver are connected to the gate line and the data line, respectively. These details are not shown in the figures as they are well known in the art. Polarizing plates 7 and 8 are provided on both sides of the liquid crystal panel 1 as is well known in the art.

The backlight device 2 includes a light guide 9, for example, fluorescent lamps 10 and 11 such as cold cathode tubes, and a reflector 1.
2 and 13. A light diffusing paint or the like for diffusely reflecting light from a fluorescent lamp is attached to the lower surface of the light guide 9. A diffusion plate 14 is provided between the backlight device 2 and the polarizing plate 8. Light from the light sources, that is, the fluorescent lamps 10 and 11, directly enters the light guide 9, and is reflected by the reflection plates 12 and 13 and enters the light guide 9. The light incident on the light guide 9 is omnidirectionally diffused by the light diffusing paint and travels upward in FIG. By this omnidirectional diffusion, the illuminance of light on the entire upper surface of the light guide 9 is made substantially uniform. The light having the uniform illuminance is further diffused by the diffusion plate 14 and enters the liquid crystal panel.

[0004]

FIG. 2 is a cross-sectional view of FIG.
It is an enlarged view of the part enclosed by 5. Since a low-cost, small-sized and light-weight backlight device has been desired in the past, the reflector 12 must also meet these requirements. Very thin plastic films have been used. At the time of assembling in a factory, the flexible plastic film is kept at a certain distance from the surface of the fluorescent lamp, and both edges of the flexible plastic film are bonded with an adhesive as shown in FIG. Glue to the edges of the upper and lower surfaces. The present invention solves the problems associated with using such flexible plastic films. In particular, because the plastic film is flexible, no measures are taken between the plastic film and the fluorescent lamp to fix the shape after mounting, and the flexible plastic film Since the reflector 12 was manually assembled, the distance between the plastic film and the fluorescent lamp was not kept stable and constant. More specifically, in some backlight devices, the distance between the surface of the fluorescent lamp 10 and the reflective film 12 is shorter than a predetermined distance D, and in other backlight devices, the distance between the two is predetermined distance D. This results in a variation such as being longer than that. Further, even with one backlight device, the predetermined distance D cannot be maintained depending on the position along the axial direction.

As described above, since the distance between the fluorescent lamp 10 and the reflecting plate 12 was not kept constant at the distance D, that is, each time the backlight device was assembled, the fluorescent lamp 10 and the reflecting plate 12 were not changed.
The following problems have arisen due to the variation in the distance between them. First, since the stray capacitance between the fluorescent lamp 10 and the deposited silver film on the surface of the plastic film varies for each backlight device, the same voltage is applied to each backlight device. This also causes a problem that the luminance differs for each backlight device. Second, the reflector 12
Since the shape of the plastic film after being attached cannot be controlled so that the distance between the fluorescent film 10 and the fluorescent lamp 10 becomes uniform in the diameter direction, the light emitted from the fluorescent lamp 10 is opposite to the light guide 9. Effectively guides light emitted to the light guide 9
It is difficult to guide the light to the entrance.

Further, as described above, the use of a very thin plastic film as the reflection plate 12 causes the following new problems. In other words, the life of the fluorescent lamp, that is, the time during which the fluorescent lamp can generate light having a brightness higher than the design value is shorter than the life of the liquid crystal panel, and it is necessary to replace the deteriorated fluorescent lamp. There is a demand for a backlight device capable of replacing a fluorescent lamp. However, since the very thin flexible plastic film is adhered to the light guide 9 by the adhesive as described above, the fluorescent lamp must be replaced after the peeling, and the plastic film must be adhered again. Not
In addition, since the thin fluorescent lamp having a diameter of about 3 to 5 mm is very easily broken, this operation is very troublesome and troublesome, and it is difficult to leave this operation to an end user. Therefore, it is necessary to develop a backlight device capable of replacing a light source, that is, a fluorescent lamp, and it is necessary to solve this problem in the development thereof.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has the following structure.

A backlight device for a liquid crystal display according to the present invention is a light-transmitting member having an elongated light source, an elongated opening for accommodating the light source, and an outer surface extending in a longitudinal direction of the opening and parallel to an inner surface of the opening. And a light guide disposed adjacent to the light transmitting member and having a light receiving surface parallel to the longitudinal direction, and a portion of the outer surface of the light transmitting member facing the light receiving surface of the light guide. A reflection film attached to a region except for the light guide, and a projection formed along the longitudinal direction in a region of the outer surface of the light transmitting member facing the light receiving surface of the light guide, The light receiving surface of the body is formed with a groove that fits into the protrusion.

[0009] The reflection film is attached to the outer surface except for the protrusion.

[0010]

FIG. 3 shows a preferred embodiment of a backlight of a liquid crystal display according to the present invention. The liquid crystal display device includes a liquid crystal display panel as shown in FIG. 1, two polarizing plates, a diffusion plate,
It has a gate line driver and a data line driver, etc.
These are not shown for simplicity. The backlight device 19 includes a light guide 29, a translucent member 20, a cold cathode fluorescent lamp 30 elongated in a longitudinal direction, and a reflection film 2.
5 The material of the light guide 29 is formed of a material having high light transmittance, such as an acrylic resin or an organic glass. Fluorescent light 3
0 may be commercially available and has terminals 24 at both ends. The diameter of the fluorescent lamp 30 is about 5 mm. The translucent member 20 is formed of a material such as an acrylic resin or an organic glass having a high light transmittance. An elongated opening 23 for accommodating the elongated fluorescent lamp 30 is formed in the translucent member 20, and the inner surface of the opening 23 and the outer surface of the translucent member 20 are viewed in the longitudinal direction of the elongated opening 23. Are parallel.

The translucent member 20 functions as a spacer between the fluorescent lamp 30 and the reflective plastic film 25,
Further, by attaching the reflective plastic film 25 to the outer surface of the translucent member 20 functioning as the spacer, the mounting shape of the reflective plastic film 25 can be stably fixed. The opening 23 provided in the translucent member 20 accommodates the fluorescent lamp 30 therein, and has a function of holding the fluorescent lamp 30 and a function of protecting the fragile fluorescent lamp 30.

A portion of the translucent member 20 facing the light guide 29 is integrally formed with a tapered protruding portion 21. The light-transmitting member 20 has a through-hole, that is, an opening 23. The inner diameter of the opening 23 is formed slightly larger than the outer shape of the fluorescent lamp 30 to facilitate insertion of the fluorescent lamp into the opening 23. In the opening 23, the fluorescent light 3
0 is accommodated, and terminals 24 at both ends of the fluorescent lamp 30 protrude from both ends of the opening 23.

On the outer surface of the translucent member 20 which is parallel to the inner surface of the opening 23, except for the surface of the tip of the tapered protruding portion 21, a very thin flexible plastic reflection film of silver is deposited. Reference numeral 25 is attached by an adhesive or the like. That is, as shown in the figure, the reflection film 25 is formed by the lower end of the vertical surface 27 of the light transmitting member 20 and the vertical surface 2.
In addition to the outer surface that ties the top of 8 and surrounds the fluorescent light,
(A) These vertical surfaces 27 and 28 and (b) the slope between this vertical surface and the vertical surface of the protruding portion 21 is attached to the portion close to the surfaces 27 and 28.

In any radial direction of the fluorescent lamp 30, the fluorescent lamp 30 and the translucent member 20 are moved in the longitudinal direction,
, The outer surface of the translucent member 20 along the longitudinal direction and the inner wall of the opening 23 along the longitudinal direction are parallel to each other, so that the inner wall of the opening 23 and the translucent member 2
The distance D between the outer surface of the fluorescent lamp 30 and the reflective film 25 is constant at any position along the longitudinal direction of the fluorescent lamp 30. Become.

A recess 22 is formed on the surface of the light guide 29 facing the light transmitting member 20. The concave portion 22 has a shape corresponding to the shape of the protruding portion 21 of the translucent member 20. That is, it has a slope having substantially the same angle as the slope of the projecting portion 21. Light from the fluorescent lamp is directly reflected on the concave portion 22 with or without being reflected by the reflection film 25.

A frame 33 for accommodating the backlight device 19 is shown below FIG. This frame 33 has walls 34 and 35 and the left part of the side wall 35 has been removed to form an open end.
Then, the frame 33 and the backlight device 19 are assembled so that the fluorescent lamp 30 is pulled out in the direction of the arrow 32 and stored therein through the open end. In this embodiment, when replacing the fluorescent lamp 30, the fluorescent lamp 30 is replaced.
Is exchanged together with the translucent member 20. That is, in order to perform the replacement, the translucent member 20 is pulled out in the direction of the arrow 32 or the arrow 37 through the open end of the side wall 35 while the fluorescent lamp 30 is housed, and the new fluorescent lamp and the translucent member are connected. Is inserted along the direction of the arrow 32 or 37. At the time of insertion, the projecting portion 21 enters the concave portion 22 while loosely fitting, so that the reflection film 25 can be positioned at a correct position with respect to the light guide 29. When the positioning in the direction of the arrow 32 is completed, the translucent member 20 is finally pushed toward the light guide 29 in the direction of the arrow 37 to bring the slopes of the two into close contact. As a result, the light emitted from the fluorescent lamp 30 and passing through the translucent member 20 efficiently enters the light guide 29 without leaking to the outside.

Since the distance between the outer peripheral surface of the fluorescent lamp 30 and the reflection film 25 is a constant distance D at any position along the longitudinal direction of the fluorescent lamp 30, the value of the stray capacitance becomes constant. As a result, it is possible to solve the problem that the stray capacitance value varies for a large number of backlight devices mass-produced, and that the brightness differs for each backlight device even when the same voltage is applied.

If the reflection film 25 is made of the light transmitting member 2
If the vertical surfaces 27 and 28 are not attached to a part of the above-described slope, and if the contact between the translucent member 20 and the light guide 29 is not tight, light leaks, so that the backlight Along with lowering the overall surface brightness of the device, rather intense light impinges directly on the edge of the LCD panel from edge 36, thereby increasing the brightness of the LCD panel edge only compared to the rest. Disadvantages arise. The present invention can avoid these problems by the above-described structure.

FIG. 4 schematically shows a reference example. FIG.
3 shows a cross section in a direction perpendicular to the longitudinal direction of the elongated fluorescent lamp 41. However, diagonal lines representing cross sections are not drawn for simplification of the drawing. The light guide 4 on the surface of the elongated fluorescent lamp 41
In addition to the portion facing the light receiving surface 0, a light-transmitting spacer 42
And a reflection film 43. Light guide 4
0, fluorescent lamp 41, spacer 42 and reflection film 43
Extend in the longitudinal direction of the fluorescent lamp, that is, in the direction perpendicular to the drawing. As in the embodiment of FIG. 3, the reflection film 43 and the spacer 42 are attached beyond the upper and lower edges of the light receiving surface of the light guide 40 so that light does not enter the light receiving surface. The light receiving surface of the light guide 40 has an arc-shaped recess corresponding to the circular surface of the fluorescent lamp 41. The spacer 42 functions as the translucent member 20 shown in FIG. In order to correctly position the exposed surface of the fluorescent lamp 41 on the light receiving surface of the light guide 40, appropriate positioning means (not shown) can be used. A suitable reflection film having a reflection film of silver or the like is provided on the inner surface of the film 43, that is, the surface facing the fluorescent lamp 41. In this reference example, since a member such as the light-transmitting member 20 of FIG. 3 surrounding the fluorescent lamp 41 is not provided, the cost can be reduced.

FIG. 5 shows still another reference example. FIG. 5 also shows a cross section in a direction perpendicular to the longitudinal direction of the elongated fluorescent lamp 51, similarly to FIG. 4, and the hatched lines representing the cross section are not drawn. Further, the structure of FIG. 5 extends in a direction perpendicular to the drawing as in FIG. A translucent member 52 is provided around the elongated fluorescent lamp 51. An opening is formed in the translucent member 52, and an elongated fluorescent lamp 51 is formed in the opening.
Is accommodated, and looking in the longitudinal direction of this elongated opening,
The inner surface of the opening is parallel to the outer surface of the translucent member 52.
An appropriate reflective film 53 having a reflective film of silver or the like is attached to the outer surface of the translucent member 52. As in the reference example of FIG. 3, the reflection film 53 is attached beyond the upper and lower edges of the light receiving surface of the light guide 50 so that light does not enter the edges. Since the cross section of the light transmitting member 52 is rectangular, the light emitting surface of the light transmitting member 52 can be correctly positioned with respect to the light receiving surface of the light guide 50. The cross section of the translucent member 52 is a quadrangle, but other polygonal columns, such as a pentagon or a hexagon, can be used.

FIG. 6 shows another reference example of the backlight device of the liquid crystal display device. The backlight device 60 includes a fluorescent lamp 50, a light guide 51, a holding member 52, a reflective plastic film 53, and a mounting member 59. A reflective plastic film 53 is attached to the inner surface of the holding member 52. The holding member 52 is attached to the light guide 51 so as to surround the fluorescent lamp 50 as shown in the drawing. Since the holding member 52 does not transmit light and functions to hold the reflective plastic film 53 and the fluorescent lamp 50, the material of the holding member 52 does not need to be a translucent material, and a metal or plastic material is used. I can do it.

No matter what radial direction the fluorescent lamp 50 and the holding member 52 are cut in the longitudinal direction, that is, the direction of the arrow 56, the holding member 52 along the longitudinal direction is cut.
The inner surface of the fluorescent lamp 50 and the outer surface of the fluorescent lamp 50 along this longitudinal direction are parallel to each other, so that the distance between the outer surface of the fluorescent lamp 50 and the reflective plastic film 53 is increased.
The distance D is constant at any position along the longitudinal direction of zero.

In order to arrange the fluorescent lamp 50 in parallel with the reflective plastic film 53, mounting members indicated by dotted lines 59 are provided at both ends of the fluorescent lamp 50. The mounting member 59 is provided for transmitting light emitted from the fluorescent lamp 50 to the light guide 5.
1 has a thickness that does not prevent light from entering. In this reference example, the thickness of the mounting member 59 is about 5 mm.
In addition to supporting the fluorescent lamp 50, the mounting member 59 holds the fluorescent lamp 50 in parallel with the light receiving surface of the light guide 51 when the holding member 52 is mounted on the light guide 51 as shown in FIG. Serves to position to keep. To this end, the distance between the vertical edges of the respective mounting members 59 at both ends of the fluorescent lamp 50 and the fluorescent lamp 50 is made equal to each other. A reflective plastic film 53 extends to the edge of the holding member 52 and engages the upper and lower surfaces of the light guide 51 by contact surfaces 57 and 58. Air exists in the space between the fluorescent lamp 50 and the reflective plastic film 53. 6 is housed in the frame 33 shown in FIG.

As described above, the holding member 52 integrally holds the fluorescent lamp 50 and simultaneously holds the fluorescent plastic film 5.
3 functions to correctly space the fluorescent lamp 50 by a certain distance D. When replacing the fluorescent lamp 50 of the backlight device 60, after removing the old fluorescent lamp together with the holding member, a new holding member 52 (including the mounting member 59) is provided.
The new fluorescent lamp 50 is integrally incorporated.
Through the release of the side wall 35 of the frame 33
Then, the mounting member 59 is moved in the direction of arrow 55 until the vertical edge of the mounting member 59 hits the light receiving surface of the light guide 51. In order to fix them at this position and to prevent light from leaking from them, means for pressing the engaging portion of the holding member 52 against the light guide 51 in the direction of arrow 54 can be used. . Instead of using the pressing means, the holding member 52 itself can be formed of an elastic material, and the contact surface can be made dense by the spring force of the holding member itself.

[0025]

According to the present invention, the stray capacitance around the fluorescent lamp of the backlight device of the liquid crystal display device can be controlled to a constant value, so that the emission characteristics of the mass-produced backlight device are made uniform. I can do it. Further, replacement of the fluorescent lamp is facilitated, and the same light emission characteristics as before the replacement can be maintained after the replacement.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a liquid crystal display device targeted by the present invention.

FIG. 2 is a diagram for explaining a problem of a conventional backlight device.

FIG. 3 is a view showing an embodiment of a backlight device of the liquid crystal display device according to the present invention.

FIG. 4 is a diagram showing a reference example of a backlight device of a liquid crystal display device.

FIG. 5 is a diagram showing another reference example of the backlight device of the liquid crystal display device.

FIG. 6 is a diagram showing still another reference example of the backlight device of the liquid crystal display device.

DESCRIPTION OF SYMBOLS 19 ... Backlight device 20 ... Translucent member 21 ... Protrusion 22 ... Indentation 23 ... Opening 24 ... Terminal 25 ... Reflection film 27 28 · · · surface 29 · · · light guide 30 · · fluorescent lamp 33 · · · frame 34, 35 · · side wall 36 · · · edge

Claims (2)

(57) [Claims] 1. A light-transmitting member having an elongated shape light source, an elongated opening for accommodating the light source, and an outer surface extending in a longitudinal direction of the opening and parallel to an inner surface of the opening, and adjacent to the light-transmitting member. A light guide having a light receiving surface parallel to the longitudinal direction, and a reflective film attached to a region of the outer surface of the light transmitting member except for a portion facing the light receiving surface of the light guide. Having, in a region of the outer surface of the translucent member facing the light receiving surface of the light guide, a protrusion is formed along the longitudinal direction,
A backlight device for a liquid crystal display device, wherein a groove is formed on the light receiving surface of the light guide so as to fit into the protrusion. 2. A backlight device for a liquid crystal display device according to claim 1, wherein said reflection film is attached to said outer surface except for said projection.