JP2002245826A - Lighting unit and liquid crystal display using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of uneven brightness and uneven white part caused by the contact of a reflective sheet with a protection member. SOLUTION: A space H is arranged between a light source side end section 3a of a reflective sheet 3 and a protection member 5 so as to avoid their mutual contact. This space H can be arranged either by shortening a protruding part of the light source side end section 3a of the reflective sheet 3, by moving the position of a light source 2 or by reducing the diameter of the light source 2 or of the protection member 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination unit having a light source disposed on a side surface of a light guide plate and a liquid crystal display using the same.

[Prior art]

In recent years, display devices for information devices such as notebook personal computers and word processors, and display devices for video devices such as portable televisions, video movies, and car navigation systems have been reduced in weight, size and thickness. In addition, liquid crystal display devices have come to be widely used, taking advantage of the feature of low power consumption. Many of these liquid crystal display devices have a configuration in which illumination light is applied from behind a display element by a built-in illumination unit in order to realize a bright display screen.

In this lighting unit, an edge light system (also called a light guide plate system) in which a light guide plate is placed on the back surface of a display element and a light source is disposed on an end face of the light guide plate is required to reduce the thickness and uniformity of luminance of a light emitting surface. It has a feature of being excellent, and an edge light method is often adopted as a method of a liquid crystal unit of a liquid crystal display device used for a notebook type personal computer or the like, giving priority to thinness. In liquid crystal display devices used in portable televisions and car navigation systems, etc., in order to achieve both thinness and brightness,
In many cases, an edge light method using two or more fluorescent discharge tubes, or an edge light method using an L-shaped fluorescent discharge tube or a U-shaped fluorescent discharge tube is used.

FIG. 3 shows a liquid crystal display device L using an edge light type illumination unit using a conventional fluorescent discharge tube 2.
It shows an example of D, and is composed of a lighting unit UT and a liquid crystal display device LD in which a liquid crystal panel or the like is mounted on the lighting unit UT. The certification unit UT is a liquid crystal panel 7
A light guide plate 1 for illuminating the light guide plate, a reflection sheet 3 arranged along the back surface of the light guide plate 1 to reflect light from the fluorescent discharge tube 2 toward the liquid crystal panel 7, and a protection provided around the fluorescent discharge tube 2. And a member 5.

[0005] The reflection sheet 3 returns the light that goes out from the back surface of the light guide plate 1 back into the light guide plate 1 and increases the illumination light that goes out of the light exit surface, and is made of a white resin film having a high reflectivity. Many are used. The light source side end 3 a of the reflection sheet 3 protrudes from the light guide plate 1 toward the fluorescent discharge tube 2. If the incident end surface 1a of the light guide plate 1 and the light source side end 3a of the reflection sheet 3 are flush, light concentrates on the side surface of the light source side end 3a to generate a bright line. This is for preventing the bright line by protruding the end 3a.

The reflector 4 returns the light from the fluorescent discharge tube 2 back to the light guide plate 1 and efficiently enters the light into the incident end face 1a of the light guide plate 1. The reflector 4 has a U-shaped cross section so as to surround the fluorescent discharge tube 2. It is bent. In addition, as the reflection sheet 3, a part around the fluorescent discharge tube 2 (this part is a “reflector”) and a part on the back side of the light guide plate 1 are separated, and both parts are bonded with an adhesive such as a double-sided tape. Some configurations have

The protection member 5 is for preventing the fluorescent discharge tube 2 from coming into contact with the reflector 4, and is of a ring shape attached to the outer periphery of the fluorescent discharge tube 2 (also called an O-ring). As the protection member 5, a rubber member having elasticity for absorbing a shock due to contact is generally used, and is provided at a predetermined interval in the fluorescent discharge tube 2.

[0008]

However, if the protection member 5 is simply attached to the fluorescent discharge tube 2, the protection member 5 may come into contact with the light source side end 3a of the reflection sheet 3. That is, the reflection sheet 3 is provided so as to slightly protrude from the light guide plate 1 toward the fluorescent discharge tube 2 to prevent bright lines. Therefore, the protection member 5 may come into contact with the light source side end portion 3a of the reflection sheet 3, but when they come into contact with each other, the reflection sheet 3 is distorted or deficient 8, and the brightness of the portion locally changes. There is a problem in that uneven brightness occurs on the irradiation surface (on the screen), and "white unevenness" due to distortion or loss 8 occurs. The term “white unevenness” refers to a state in which the image looks whiter on the screen than the surroundings, and may cause defective products.

Accordingly, an object of the present invention is to solve the problem of uneven brightness and uneven whiteness caused by the reflection sheet coming into contact with the protective member, and to provide a highly reliable lighting unit and a liquid crystal display device using the same. It is in.

[0010]

According to a first aspect of the present invention, there is provided an illumination unit, comprising: a light source; a light guide plate disposed in close proximity to the light source to guide light from the light source; And a reflector that includes the light source and reflects the light of the light source toward the incident end face, and the light source side end of the reflective sheet is arranged so as to protrude from the incident end face of the light guide plate, In a lighting unit in which a protection member is provided on the outer periphery of the light source to protect the light source, the light source side end of the reflection sheet and the protection member are provided at intervals so as to avoid contact with each other. And here,
The interval for avoiding contact with each other means that the projecting length of the light source side end of the reflection sheet may be shortened, the arrangement position of the light source may be shifted, and the diameter of the light source or the protection member may be changed. May be reduced.

According to the present invention, since the light source side end of the reflection sheet does not come into contact with the protective member, the reflective sheet is not distorted or lost due to the contact between the protective member and the reflective sheet.

A lighting unit according to a second aspect of the present invention comprises:
The interval at which the light source side end of the reflection sheet and the protection member avoid contact with each other is up to five times the diameter of the light source.

According to the present invention, the occurrence of a bright line can be prevented. That is, if the interval exceeds five times the diameter of the light source, a bright line is generated, which causes luminance unevenness.
When the upper limit of the interval is five times the diameter of the light source, the generation of bright lines can be prevented.

According to a third aspect of the present invention, there is provided a lighting unit.
The protection member is characterized in that a concave portion is formed in a portion of the outer periphery thereof facing the light source side end of the reflection sheet.

According to the present invention, since the concave portion is formed on the outer periphery of the protective member, an interval is provided at the concave portion to avoid mutual contact, and the reflection caused by the contact between the protective member and the reflective sheet is provided. It is possible to prevent the sheet from being distorted or broken.

According to a fourth aspect of the present invention, there is provided a liquid crystal display device using the illumination unit according to any one of the first to third aspects, and a liquid crystal panel disposed above the illumination unit. It is characterized by having.

According to the present invention, it is possible to prevent the reflection sheet from being distorted due to contact between the light source side end of the reflection sheet and the liquid crystal display device using a highly reliable lighting unit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the present embodiment comprises a lighting unit UT and a liquid crystal display device LD in which a liquid crystal panel or the like is mounted on the lighting unit UT. The illumination unit UT is an illumination unit of an edge light system, and is arranged so as to be along a light source 2, a light guide plate 1 that is arranged close to the light source 2 and guides light from the light source 2, and along a back surface of the light guide plate 1. And a reflector 4 that contains the light source 2 and reflects light from the light source 2 toward the incident end face.

The light source 2 is a high-frequency alternating current (40 to 100 k
(Hz), and a fluorescent discharge tube 2 that emits light when driven at (Hz) is used. The diameter of the light source 2 of the present embodiment is 1.8 mm.

A protective member 5 for protecting the light source 2 is arranged at a predetermined interval on the outer periphery of the light source 2. Protection member 5
Is an annular shape attached to the outer periphery of the fluorescent discharge tube 2 (also referred to as an "O-ring"), and is made of rubber having elasticity to absorb a shock due to contact. Note that the thickness of the protection member 5 is 0.2 mm. As shown in FIG. 2, the protective member 5 has a concave portion 5 at a portion of the outer periphery of the reflective sheet 3 which faces the light source side end 3a.
What formed a may be sufficient. As long as at least one concave portion 5a is formed in a portion of the reflection sheet 3 facing the light source side end portion 3a, the concave portion 5a may be formed at a predetermined interval over the entire outer periphery. However, in that case, the reflection sheet 3
The distance H between the light source side end portion 3a and the protective member 5 to avoid contact with each other must be designed with an upper limit of five times the diameter of the light source 2 as described later. If the interval H is too large, light leaking through the interval H becomes a bright line, and if the light actually exceeds five times the light source 2, a bright line starts to be generated. Therefore, the interval H should not touch (0 <interval H), but the interval H is preferably as small as possible.

The light guide plate 1 is arranged close to the fluorescent discharge tube 2 and guides the light from the fluorescent discharge tube 2, and has optimal optical characteristics represented by transmittance and refractive index necessary for light transmission. It is formed of a material such as natural acrylic.

The reflection sheet 3 is made of a white resin film having a high reflectance, and is bent in a U-shaped cross section so as to surround the fluorescent discharge tube 2. Reflective sheet 3
Has a role of returning the light going out from the back surface of the light guide plate 1 back into the light guide plate 1 and increasing the illumination light emitted from the light emitting surface. On the irradiation surface side of the light guide plate 1, a light correction sheet 6 is arranged. The light correction sheet 6 is used to equalize the light emitted from the illumination unit UT and increase the brightness, and is made of a diffusion sheet, a prism sheet, or the like. Then, above such a lighting unit UT (on the irradiation surface of the light correction sheet 6),
The liquid crystal panel 7 is mounted to form a liquid crystal display device LD.

Here, the light source side end 3a of the reflection sheet 3 and the protection member 5 are arranged with an interval H for avoiding mutual contact. The interval H for avoiding mutual contact may be such that the length of the light source side end 3a of the reflection sheet 3 protruding may be shortened, the arrangement position of the fluorescent discharge tube 2 may be shifted, The diameters of the fluorescent discharge tube 2 and the protective member 5 may be reduced. That is, some reflectors 4 have a semicircular cross section. However, at present, the position of the reflector 4 is slightly shifted along the inner peripheral side or the diameter of the fluorescent discharge tube 2 is being reduced. Alternatively, the diameter of the protection member 5 may be reduced. Further, at the time of attachment, the protection member 5 is prevented from contacting the light source side end 3 a of the reflection sheet 3.

When the protective member 5 having the concave portion 5a formed on the outer periphery thereof is used, the protective member 5 is provided with a reflective sheet both when the protective member 5 is mounted on the fluorescent discharge tube 2 and after mounting. 3 can be prevented from coming into contact. Therefore, distortion or loss of the reflection sheet 3 due to contact between the protection member 5 and the reflection sheet 3 is reliably prevented.

Here, the distance H between the light source side end 3a of the reflection sheet 3 and the protective member 5 to avoid contact with each other needs to be designed with an upper limit of five times the diameter of the light source. Judging only from the viewpoint of preventing contact between the reflection sheet 3 and the protective member 5, it is desirable that the interval H is wide. On the other hand, if the interval H is too wide, light leaking through the interval H becomes a bright line, and the appearance is deteriorated. As a result of an experiment, it has been found that when the interval H exceeds 5 times the diameter of the light source, a bright line is generated, which causes luminance unevenness. Further, in a liquid crystal display device required to be miniaturized, there is naturally a limit in increasing the interval H. Accordingly, in order to prevent the contact between the reflection sheet 3 and the protective member 5 and to maintain good display accuracy and reduce the size, the interval H needs to have an upper limit of 5 times the diameter of the light source. is there. In the present embodiment, since the diameter of the fluorescent discharge tube 2 is 1.8 mm, the upper limit of the interval H is 9.0 mm, which is five times as large, and therefore, 0 <interval H ≦
9.0.

In the above embodiments, the case where the straight tube-type fluorescent discharge tube 2 is used has been described. However, the case where the L-type fluorescent discharge tube or the U-shaped fluorescent discharge tube is used is described. For example, the present invention can be generally applied to an edge light system.

[0028]

According to the illumination unit of the present invention, since the light source side end of the reflection sheet and the protection member are provided with an interval for avoiding contact with each other, the protection member and the reflection sheet are in contact with each other. A reliable lighting unit and a liquid crystal display using the same solve the problem of uneven brightness and uneven whiteness caused by the reflecting sheet coming into contact with the protective member, and reliably eliminate distortion and loss of the reflecting sheet due to A device can be provided.

[0029]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a liquid crystal display device including a lighting unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a liquid crystal display device including a lighting unit according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a conventional lighting unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 1 a incident end face of light guide plate 2 fluorescent discharge tube (light source) 3 reflective sheet 3 a light source side end of reflective sheet 4 reflector 5 protective member 5 a concave portion of protective member 6 light correction sheet 7 liquid crystal panel 8 distortion or reflection sheet Defective UT Lighting unit LD Liquid crystal display

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // F21Y 103: 00 F21Y 103: 00

Claims (4)

[Claims] 1. A light source, a light guide plate disposed in close proximity to the light source to guide light from the light source, a reflection sheet disposed along a back surface of the light guide plate, and a light source including the light source and transmitting light from the light source. A reflector for reflecting light toward the incident end face, wherein the light source side end of the reflection sheet is disposed so as to protrude from the incident end face of the light guide plate, and a protection member is disposed on the outer periphery of the light source to protect the light source. In the lighting unit, the light source side end of the reflection sheet and the protection member are provided with an interval for avoiding contact with each other. 2. The lighting unit according to claim 1, wherein an interval between the light source side end of the reflection sheet and the protective member to avoid contact with each other is limited to an upper limit of five times the diameter of the light source. 3. The lighting unit according to claim 1, wherein the protective member has a concave portion formed in a portion of the outer periphery thereof facing the light source side end of the reflective sheet. 4. A liquid crystal display device comprising: the lighting unit according to claim 1; and a liquid crystal panel disposed above the lighting unit.