JP2003168311A - Surface light source device and flat display device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device 10 provided with a rectangular light guiding plate 4 and a tubular light source 3 disposed along its incident end surface 4a, wherein a prescribed positioning relation between the tubular light source 3 and the incident end surface 4a can be easily kept, and the light guiding plate 4 can be prevented from being cracked initiating from the engagement part of the light guiding part 4 and a frame 2 when receiving an impact. <P>SOLUTION: When positioning the light guiding plate 4 relative to the frame 2 by making an ear part 41 protruding from the right and left sides of the light guiding plate 4 engaged with a receiving recessed part 21 on the peripheral surface of the frame 2, a rubber cap 1 is put on the tip part of the ear part 41. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device having a light guide plate, and a liquid crystal display device and other flat display devices using the surface light source device as a backlight.

[0002]

2. Description of the Related Art A surface light source device comprises a tubular light source and a light guide plate which transmits the light incident from the tubular light source and emits the light from a main surface. A general surface light source device is an edge light (side light) type in which a tubular light source is arranged along an end surface of a light guide plate, and the light guide plate is positioned and held from a frame (for example, Japanese Patent Laid-Open No. 2000- 27563
5, JP 2001-133781).

A conventional surface light source device will be described with reference to FIG.

The surface light source device is a backlight of a liquid crystal display device, and includes a rectangular light guide plate 4, a frame 2 for housing the light guide plate 4, and one side end surface 4a of the light guide plate 4. And a tubular light source 3 that is arranged in the same manner. The tubular light source 3 is
The light guide plate 4 is held from the frame 2 via the rubber cap 35, and the light guide plate 4 is also brought into contact with the inner peripheral surface of the frame 4 or the like to be positioned. In this way, the light guide plate 4 and the tubular light source 3 are both positioned and supported by the frame 2, so that a predetermined positional relationship is maintained between them. In particular, in order to achieve sufficient light utilization efficiency and light emission uniformity, it is necessary to keep the distance between the incident end surface 4a of the light guide plate 4 and the tubular light source 3 within a predetermined range.

However, the light guide plate 4 is made of an acrylic resin or the like in order to impart necessary transparency and rigidity, whereas the frame 2 is made of polyprene resin or the like containing a filler in order to impart strength and toughness. Therefore, the coefficient of thermal expansion is different. In addition, it is necessary to absorb misalignment of dimensions because the molding is performed separately.

Therefore, a certain amount of clearance is provided between the light guide plate 4 and the frame 2 that houses it. Further, in order to keep the distance between the light guide plate 4 and the tubular light source 2 constant, the ear portion 41 provided on the light guide plate 4 engages with the receiving recess 21 on the inner peripheral surface of the frame 2, so that Positioning is performed. More specifically, rectangular tab-shaped ears 41 are projected from the left and right sides of the rectangular light guide plate 4 when viewed from the incident end surface, at locations near the electrode portions at both ends of the tubular light source 3. The ears 41 are received in the corresponding receiving recesses 21 of the rectangular frame 2, and the front and rear end faces 4 (left and right when viewed from the protruding direction) of the ears 41 when viewed from the incident end face 4a.
1a and 41b respectively regulate the positional deviation of the light guide plate 4 toward the side closer to the tubular light source 3 and the side away from the tubular light source 3.

[0007]

However, in the conventional surface light source device as described above, as shown in FIG. 4, when the surface light source device receives a strong mechanical impact, the light guide plate 4 is The crack 49 sometimes entered from the corner 43 of the ear 41.

Since the frame 2 is molded from a resin material that is softer than the light guide plate 4, some amount of impact is absorbed by the frame 2. However, when the surface light source device and the flat display device in which the surface light source device is incorporated are used for carrying and the like, there is a case where a considerably strong impact is applied due to a drop or a collision with a concrete surface. In such a case, the peaks 23 of the frame 2 may abut the valleys 13 of the light guide plate 4 violently, which may give intense stress to the light guide plate 4, and the light guide plate 4 is seriously cracked 5. It will end up.

On the other hand, when a strong impact is applied, the light guide plate 4
The ears 41 may be disengaged from the engagement recesses 21 of the frame 2 due to the shake in the thickness direction. Even if it is not a very strong impact, under the condition that distortion due to heating or cooling is applied at the same time, the ear portion 41 and the receiving concave portion 21 are thus formed.
There was a case that the engagement with was disengaged. When the ear 41 and the receiving recess 21 are disengaged from each other, the position of the incident end surface 4a of the light guide plate 4 with respect to the tubular light source 3 is largely displaced from the designed position. Will be done.

The present invention has been made in view of the above problems, and in a surface light source device including a light guide plate and a tubular light source disposed on the incident end surface thereof, and a flat display device including the planar light source device, the tubular light source and the incident end surface are provided. It is possible to easily and surely maintain a predetermined positional relationship with and to prevent cracks from entering the light guide plate from the engaging portion between the light guide plate and the frame when a shock is applied. is there.

[0011]

According to another aspect of the surface light source device of the present invention, a light guide plate having a substantially rectangular flat plate shape, a frame for holding the light guide plate, and a frame positioned and supported by the frame are incident on the light guide plate. A tubular light source arranged along the end face, projections protruding outward from the left and right end faces of the substantially rectangular flat plate-shaped light guide plate at locations near the left and right ends of the incident end face, and provided on the inner peripheral surface of the frame. And a receiving recess for positioning the light guide plate by engaging with the protrusion, and the protrusion has a tubular light source side positioning member for restricting displacement of the light guide plate in a direction approaching the tubular light source. In a surface light source device including a contact surface and a facing positioning contact surface that regulates a positional deviation of the light guide plate in a direction away from the tubular light source, the tubular light source side positioning contact surface and the inner surface of the receiving recess. In the surface light source device, in which the elastic body is sandwiched between the opposing positioning contact surface and the inner surface of the receiving recess, the elastic body is sandwiched between the protrusion and the inner surface of the receiving recess. It is characterized by

With the above structure, the predetermined positional relationship between the tubular light source and the incident end face can be maintained easily and reliably, and
It is possible to prevent the light guide plate from cracking from the engaging portion between the light guide plate and the frame when receiving an impact.

In the surface light source device according to claim 3, the elastic body is
It is formed in a cap shape that covers the tip of the protrusion,
A sandwiching portion sandwiched between the protrusion and the inner surface of the receiving recess, and a beam (beam) extending from an edge of the sandwiching portion and contacting the protrusion from at least one main surface side of the light guide plate. It consists of and.

With such a structure, the elastic body can be easily incorporated, and moreover, it can be surely arranged at a predetermined position.

According to another aspect of the flat display device of the present invention, a substantially rectangular flat plate-shaped display panel main body in which pixels are arranged in a matrix, and a substantially rectangular flat plate-shaped light guide plate disposed so as to be superposed on the display panel main body are provided. A frame that holds the light guide plate, a tubular light source that is positioned and supported by the frame, and is arranged along the incident end face of the light guide plate, and a substantially rectangular flat plate shape at a position close to the left and right ends of the incident end face. In the flat display device, a projection protruding outward from the left and right end surfaces of the light guide plate and a receiving recess provided on the inner peripheral surface of the frame for positioning the light guide plate by engagement with the projection are provided. An elastic body is sandwiched between and the inner surface of the receiving recess.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface light source device of an embodiment will be described with reference to FIGS.

The surface light source device 10 of the embodiment is a backlight of a liquid crystal display device, and has a rectangular light guide plate 4, a frame 2 for accommodating the light guide plate 4, and a light guide plate 4 held by the frame 2. The tubular light source 3 is arranged along one side end surface 15.

FIG. 1 is a schematic broken perspective view showing an essential part of the assembled surface light source device, and FIG. 2 is a schematic view for further explaining the essential part of the surface light source device shown in FIG. FIG.

The tubular light source 3 is held in a predetermined positional relationship with respect to the frame 2 by fixing the electrode portions at both ends with a part of the frame 2 via the rubber caps 35.

On the other hand, the positional relationship between the light guide plate 4 and the frame 2, particularly the positional relationship in the direction perpendicular to the incident end face 4a, is as described in detail below. 41 is the receiving recess 2 of the inner peripheral surface 2 c of the frame 2.
By being fitted in the rubber sheet 1 via the rubber cap 1, it is reliably held with high positional accuracy. That is, rattling and disengagement due to the required clearance are prevented.

The ears 41 of the light guide plate 4 are rectangular in shape.
Then, it protrudes outward from the left and right end faces 4c when viewed from the incident end face 4a. In particular, in the illustrated example in which the ears 41 project outwardly symmetrically from a position close to the incident end surface 4a, the ear portion 41 has a flat rectangular tab shape. That is,
The protruding size of the ears 41 is smaller than the size in which the ears 41 extend along the left and right end surfaces 4c of the light guide plate 4, and is uniform. The top and bottom surfaces of the ear portion 41 when the thickness direction of the light guide plate 4 is the vertical direction are continuous with the emission surface 4d and the back surface of the corresponding light guide plate 4, respectively, and the thickness is substantially uniform throughout. is there. The end surfaces that surround the ear portion 41 from the horizontal direction, that is, the side end surfaces 41 a, 41 b, and 41 c at the front and rear and protruding ends of the ear portion 41 are similar to the left and right end surfaces 4 c of the light guide plate 4 of the light guide plate 4. It forms a wall surface perpendicular to the emission surface 4d and the back surface.

The valley corner portions 43 formed in front of and behind the ear portion 41 when viewed from the incident end face 4a form a smooth curved surface with rounded corners. That is, the side end faces 41 before and after the ear portion 41
The a and 41b are smoothly connected to the end face 4c of the other part of the light guide plate 4 via a concave curved surface having a relatively large radius of curvature (R).

On the other hand, in the mountain corner portion 44 formed before and after the ear portion 41, the side end surfaces 41a and 41b before and after the ear portion 41,
The side end surface 41c forming the protruding end of the ear portion 41 is fitted at a right angle.

The light guide plate 4 is made of a transparent resin such as an acrylic resin, and typically has a wedge-shaped cross section whose thickness decreases as the distance from the incident end face increases. In the illustrated example, light reflecting tapes 48 for preventing light leakage are attached to the left and right end surfaces of the light guide plate 4.

The frame 2 for accommodating the light guide plate 4 is made of a resin such as polypropylene and is arranged along the peripheral wall portion 25 surrounding the four circumferences of the light guide plate 4 and the back surface of the light guide plate 4 (the surface opposite to the emission surface). And a bottom surface supporting portion 26. Bottom support 26
May cover the entire back surface of the light guide plate 4, or may be provided at the peripheral portion of the light guide plate 4 and other specific places.

The peripheral wall portion 25 of the frame 2 is formed to have a size capable of accommodating the display panel body in the example shown in FIGS. That is, the display panel body is formed so as to be housed in an overlapping manner on the light guide plate 4, and when the surface light source device and the display panel are combined, the display panel body is placed inside the resin frame 2. In the housed state, it is sandwiched between the frame 2 and a metal bezel cover.
Here, the display panel body means a rectangular plate-shaped portion excluding accessories such as a flexible substrate for drive input.

The inner peripheral surface 2c of the frame 2, that is, the inner surface of the peripheral wall portion 25 forms a wall surface perpendicular to the light guide plate 4 at a position along the left and right end surfaces 4c of the light guide plate 4.

On the inner peripheral surface of the frame 2, the receiving concave portion 2 for receiving the ear portion 41 corresponding to the ear portion 41 of the light guide plate 4.
1 is provided. The receiving concave portion 21 is formed so that the contour in the plan view is substantially similar to the contour of the ear portion 41 and has a dimension slightly larger than this. That is, the inner surface of the receiving recess 21 has the side end surfaces 41 a, 41 b, 4 of the ear portion 41.
Inner wall surfaces 21a, 21b, 21c respectively corresponding to 1c
Consists of. Further, the side end surfaces 41a, 41b, 4 of the ear portion 41 are
1c and inner wall surfaces 21a, 21b, 21c of the receiving recess 21
Are parallel to each other and form a predetermined clearance.

In the receiving recess 21, the valley corner 43 of the ear 41 is formed.
Corresponding to the mountain corner portion 23 having substantially the same radius of curvature,
Corresponding to the mountain corner portion 44 of the ear portion 41, the valley angle portion 24 forming a ridge angle (subjective) at a substantially right angle are provided at the front and rear portions as viewed from the incident end face 4a.

As shown, the ears 41 and the receiving recess 21
The rubber cap 1 is inserted from above and is sandwiched in the gap between and. The rubber cap 1 has a shape in which an elongated rectangular rubber plate is provided with a bead portion having an angular cross section over both short sides and one long side thereof, that is, over the entire circumference excluding the long side which is located below. . In the state where the rubber cap 1 is sandwiched in the gap between the ear portion 41 and the receiving recess 21, the rubber cap 1 has the tip portion of the ear portion 41 on the side of the side end surfaces 41a, 41b, 41c and the emission surface. 4d
Cover from the side.

More specifically, the rubber cap 1 has a rectangular plate-like portion 1c elongated in the front-rear direction, vertical prismatic portions 1a and 1b connected to both front and rear ends thereof, and a lower end thereof connected to an upper end thereof. It is composed of a beam-shaped portion 1d having a rectangular cross section that extends in the front-rear direction. The surface of the rubber cap 1 that faces the outside in the assembled state (the right surface in FIGS. 1 and 2) forms one flat surface.

The rectangular plate-shaped portion 1c is sandwiched between the flat rectangular side end surface 41c forming the protruding end of the ear portion 41 and the corresponding inner wall surface 21c of the receiving recess 2. In addition, the front and rear prismatic portions 1 a and 1 b have the front and rear side end surfaces 41 of the ear portion 41.
It is sandwiched between a and 41b and the corresponding inner wall surfaces 21a and 21b. On the other hand, the square beam-shaped portion 1d is not sandwiched between the ear portion 41 and the receiving concave portion 21, but the light guide plate 4 is formed.
Of the ear 41, and the lower surface of this portion abuts the upper surface of the tip of the ear 41.

The front and rear prismatic portions 1a and 1b are formed by the light guide plate 4.
The positional shift in the front-back direction is controlled, and thereby the incident end surface 4a of the light guide plate 4 and the tubular light source 3 are maintained in a predetermined positional relationship. That is, the rubber cap 1
Is the most essential part of. In addition, the rectangular plate-shaped portion 1c mainly serves to regulate the positional deviation of the light guide plate 4 in the direction along the incident end surface 4a.

Since the rubber cap 1 is formed in the above-mentioned shape, when the surface light source device is assembled, the light guide plate 4 is housed in the frame 2 and then pushed in from above to be easily assembled. it can. Moreover, as long as the square beam-shaped portion 1d is pushed to the position where it engages with the upper surface of the ear portion 41, the rubber cap 1 is vertically moved (thickness direction of the light guide plate 4).
Will also be positioned and can be reliably placed at a predetermined position.

In the example shown in FIG. 2, a clearance is provided between the lower end surface of the rubber cap 1 and the bottom surface supporting portion 26 of the frame 2, whereby the rubber cap 1 is pressed by the downward pressure. It prevents the unwanted distortion.

The upper end surface of the rubber cap 1 is designed so as not to contact the lower surface of the display panel body. That is, it is designed to be positioned sufficiently below the shelf-shaped surface of the frame 2 that supports the display panel body or the upper surface of the rubber member that is sandwiched between the light guide plate 4 and the display panel body. This prevents undesired strain from being applied to the rubber cap 1 as in the lower end surface side.

In addition to such pressing from above and below, the rectangular beam-shaped portion 1d is subjected to undesired bending (deflection) or strain (distortion) in the rubber cap 1 before or during the assembling operation. It has the effect of preventing That is, the presence of the rectangular beam-shaped portion 1d not only facilitates the assembling operation, but also causes an undesired distortion in the portion sandwiched between the ear portion 41 and the receiving recess 21, particularly the rectangular plate-shaped portion 1c. It is prevented from occurring.

The reflection sheet 2 is provided on the back surface of the light guide plate 4.
6 are arranged, and on the emission surface 4d of the light guide plate 4, a three-layer optical sheet 47 including a diffusion sheet and two prism sheets is arranged. The lead wire 36 for the lamp 3 is housed in the recess of the frame 2 at a location along the lamp 3.

The rubber cap 1 is made of, for example, silicone rubber, but can be made of a durable rubber material such as fluorine rubber, urethane rubber, ethylene propylene rubber, and thermoplastic polyester elastomer. The rubber cap 1 can be integrally molded from these rubber materials. That is, the rubber cap 1 is an elastic body obtained by molding or the like from a material having appropriate rubber elasticity and durability.

The hardness of the rubber material constituting the rubber cap 1 is preferably in the range of 80 to 90 in hardness (HS) according to JIS K 6301 A-type spring hardness test, for example, around 85. With such a range of hardness,
This is advantageous in that the pushing operation is easy, the displacement of the light guide plate 4 is prevented, and the effect of shock absorption is sufficiently exhibited.

FIG. 3 shows two modified examples of the shape of the rubber cap 1.

In the first modification, a rectangular beam-shaped portion 1e similar to the rectangular beam-shaped portion 1d on the upper end surface side is also provided on the lower end surface side. With such a shape, when assembling the surface light source device,
Before the light guide plate 4 is fitted into the frame 2, it is necessary to fit the rubber cap 1 to the ear portion 41 of the light guide plate 4, and the burden of the assembling work is somewhat increased. But the shock absorption effect,
Also, it is possible to further increase the effect of preventing positional deviation.

In the second modification, the rectangular beam portion 1d is omitted in the rubber cap similar to that of the embodiment. Even with such a shape, it is possible to exhibit almost the same impact absorbing effect and positional deviation preventing effect as those of the embodiment. In particular, such a shape can be adopted when there is no dimensional margin between the light guide plate 4 and the display panel body.

According to the above-described embodiments and modifications, the light guide plate 4 can be positioned more reliably and highly accurately, and the engaging portion between the light guide plate and the frame when a strong impact is received. Therefore, it is possible to sufficiently prevent the light guide plate from cracking. Further, when a strong impact or the like is received, it is possible to sufficiently prevent the engagement from being disengaged and a large positional deviation. Moreover, the member cost and the assembly cost are hardly increased.

In the above-mentioned embodiments and modifications, the rubber cap is described as a molded body of a rubber material, but it may be formed of a foam material such as a polyolefin resin. Also in this case, it is preferable that the hardness is within the above range.

In some cases, even an elastic body made of a three-dimensional woven fabric made of filaments having a large diameter,
Alternatively, the elastic member may be a combination of leaf springs made of metal or resin.

Although the surface light source device has been described as the backlight of the transmissive liquid crystal display device in the above-mentioned embodiments and modifications, the same applies to the case of the front light of the reflective liquid crystal display device.

Further, in the above-mentioned embodiment and modification,
Although the ear portion as the engaging projection provided on the light guide plate is described as a rectangular tab shape, it may be trapezoidal or may be a curved bulge shape without a ridge corner portion. It may have a saw-tooth shape having two side end faces.

[0049]

The predetermined positional relationship between the tubular light source and the incident end face can be easily maintained, and the light guide plate can be prevented from being cracked from the engaging portion between the light guide plate and the frame when a shock is applied. You can

[Brief description of drawings]

FIG. 1 is a schematic cutaway perspective view showing a main part of an assembled surface light source device according to an embodiment.

FIG. 2 is a schematic vertical sectional view for further explaining a main part of the surface light source device of FIG.

FIG. 3 is a schematic perspective view showing a shape of a rubber cap according to a surface light source device of a modified example.

FIG. 4 is a plan view schematically showing a main part of a conventional surface light source device.

[Explanation of symbols]

1 Rubber cap that covers the ears 41 of the light guide plate 10 Surface light source device 2 frames 21 Receiving recess for receiving the ear 41 of the light guide plate 3 Tubular light source (lamp) 4 Light guide plate 41 Ears for positioning the light guide plate

Claims (5)

[Claims] 1. A substantially rectangular flat light guide plate, a frame for holding the light guide plate, a tubular light source positioned and supported by the frame and arranged along an incident end face of the light guide plate, and the incident light. Protrusions protruding outward from the left and right end faces of the substantially rectangular flat plate-shaped light guide plate at locations close to the left and right ends of the end face, and the light guide plate provided on the inner peripheral surface of the frame and engaged with the protrusions. And a receiving concave portion for positioning, wherein the projection has a tubular light source side positioning contact surface that regulates a positional deviation of the light guide plate in a direction approaching the tubular light source,
In a surface light source device provided with an opposing side positioning contact surface that regulates the positional deviation of the light guide plate in a direction away from the tubular light source, between the tubular light source side positioning contact surface and the inner surface of the receiving recess, And an elastic body sandwiched between the facing positioning contact surface and the inner surface of the receiving recess. 2. The surface light source device according to claim 1, wherein the elastic body is a rubber molded body. 3. The elastic body is formed in a cap shape that covers a tip portion of the protrusion, and a sandwiching portion sandwiched between the protrusion and an inner surface of the receiving recess, and extending from an edge of the sandwiching portion. 3. The surface light source device according to claim 1, further comprising a beam portion that is present and abuts on the protrusion from at least one main surface side of the light guide plate. 4. The elastic body is A of JIS K 6301.
Shape hardness (HS) by spring hardness test is 80 ~ 90
3. The surface light source device according to claim 1, wherein the surface light source device is made of a material within the range. 5. A substantially rectangular flat plate-shaped display panel main body in which pixels are arranged in a matrix, a substantially rectangular flat plate-shaped light guide plate which is arranged so as to overlap the display panel main body, and a frame which holds the light guide plate. A tubular light source which is positioned and supported by the frame and is arranged along the incident end face of the light guide plate; and left and right end faces of the substantially rectangular flat plate-like light guide plate at locations close to the left and right ends of the incident end face. In a flat display device including a protrusion protruding outward from the inner peripheral surface of the frame, and a receiving concave portion that positions the light guide plate by engaging with the protrusion, the inner surface of the protrusion and the receiving concave portion A flat panel display device characterized in that an elastic body is sandwiched between and.