CN210270453U - Backlight device and liquid crystal display device - Google Patents

Abstract

The utility model provides an improve backlight device and liquid crystal display device that show the grade. The backlight device of the embodiment includes a light guide plate and a light source that emits light to the light guide plate. The light guide plate has a 1 st main surface forming an emission surface, a 2 nd main surface opposing the 1 st main surface, a 1 st side surface forming an incident surface opposing the light source, a 2 nd side surface opposing the 1 st side surface, and a pair of 3 rd side surfaces connected to the 1 st side surface and the 2 nd side surface, respectively. The 2 nd side surface and the 3 rd side surface are connected by a 1 st corner portion, and the 2 nd side surface has a concave portion located closer to the incident surface side than the 1 st corner portion. The concave part has an inner side surface opposite to the 3 rd side surface and an inner bottom surface opposite to the 1 st side surface, the inner side surface and the inner bottom surface are connected by an arc-shaped 2 nd corner part, and the surface roughness of the 2 nd corner part is larger than that of the inner bottom surface.

Description

Backlight device and liquid crystal display device

Citations to related applications such as priority foundation applications

The present application claims priority from japanese patent application 2018-147613 (application date: 8/6/2018). The present application includes the entire contents of the application by reference to the japanese patent application.

Technical Field

Embodiments described herein relate generally to a backlight device and a liquid crystal display device including the backlight device.

Background

In recent years, liquid crystal display devices have been widely used as display devices of portable terminals such as smartphones and tablet personal computers, or display devices of in-vehicle devices. In general, a liquid crystal display device includes a liquid crystal display panel and a backlight device (illumination device) that is disposed opposite to a back surface side of the liquid crystal display panel and illuminates the liquid crystal display panel.

The backlight device includes: a light guide plate having an emission surface facing the liquid crystal display panel; an optical sheet placed on the light guide plate so as to overlap with the light guide plate; a reflective sheet disposed opposite to the back surface of the light guide plate; and a light source that emits light to an incident surface (end surface) of the light guide plate. The light incident on the light guide plate is repeatedly reflected in the light guide plate and is emitted from the entire emission surface toward the liquid crystal display panel.

A light guide plate is proposed in which a bathtub-shaped or rectangular-shaped recess (notch) is provided on a side surface (light entrance opposite side end surface) of the light guide plate opposite to the light entrance surface. The recess (notch) is utilized as a space for disposing accessories such as a camera, a sensor, and the like. In general, the light guide plate is formed by injection molding using a mold, and the recess is formed by machining, for example, cutting one end surface of a molded product.

In this way, when the recesses are formed by machining, the machined surfaces (inner surfaces) defining the recesses have a surface roughness that is greater by one digit or more than that of the other surfaces and side surfaces of the light guide plate. Therefore, a part of the light incident on the light guide plate is irradiated to the machined surface and diffused or diffusely reflected, and the edge of the concave portion becomes bright. This reduces the display quality of the display screen.

In many light guide plates, each corner portion is rounded into an arc shape having a desired radius of curvature. There are the following cases: the light reflected by such a corner portion and the light reflected by the machined surface of the concave portion are concentrated to a spot near the corner portion, and become a bright spot. The occurrence of such a bright spot also causes a reduction in display quality. Further, in the case where two corner portions on the light source side, i.e., the light incident side of the light guide plate are rounded, the luminance (light amount) at each corner portion may be reduced or insufficient on the light incident side.

SUMMERY OF THE UTILITY MODEL

An object of an embodiment of the present invention is to provide a backlight device and a liquid crystal display device having improved display quality.

The backlight device of the embodiment includes a light guide plate and a light source that emits light to the light guide plate. The light guide plate has a 1 st main surface forming an emission surface, a 2 nd main surface opposing the 1 st main surface, and side surfaces connecting the 1 st main surface and the 2 nd main surface, and the side surfaces have a 1 st side surface forming an incident surface opposing the light source, a 2 nd side surface opposing the 1 st side surface, and a pair of 3 rd side surfaces connecting the 1 st side surface and the 2 nd side surface, respectively. The 2 nd side surface and the 3 rd side surface are connected by a 1 st corner portion, and the 2 nd side surface has a concave portion located closer to the incident surface side than the 1 st corner portion. The concave part is provided with an inner side surface opposite to the 3 rd side surface and an inner bottom surface opposite to the 1 st side surface, the inner side surface and the inner bottom surface are connected by a 2 nd corner part in an arc shape, and the surface roughness of the 2 nd corner part is larger than that of the inner bottom surface.

Drawings

Fig. 1 is a perspective view showing a display surface side of a liquid crystal display device according to an embodiment.

Fig. 2 is an exploded perspective view of the liquid crystal display device.

Fig. 3 is an exploded perspective view of the backlight device.

Fig. 4 is a plan view showing an example of a mold used for injection molding of the light guide plate of the backlight device.

Fig. 5 is a plan view of the mold in a state where the 1 st and 2 nd slides are opened.

Fig. 6 is a perspective view showing the end of the light guide plate opposite to the incident side.

Fig. 7 is a plan view schematically showing an end portion on the opposite side to the light guide plate.

Fig. 8 is a plan view schematically showing an end portion of the light guide plate on the opposite side to the incident side, which has another reflection reducing structure.

Fig. 9 is a plan view schematically showing an end portion of the light guide plate on the opposite side to the incident side, which has yet another reflection reducing structure.

Fig. 10 is a plan view showing the light source and the end portion of the light guide plate on the incident side.

Fig. 11 is a perspective view showing the light source and the end portion of the light guide plate on the incident side.

Fig. 12 is a plan view showing an incident-side end portion of a light guide plate and a light source according to another configuration example.

Fig. 13 is a perspective view showing an incident-side end portion of the light guide plate and the light source according to another configuration example.

Fig. 14 is a plan view showing an incident-side end portion of a light guide plate and a light source according to still another configuration example.

Fig. 15 is a perspective view showing an incident-side end portion of the light guide plate and a light source according to the still another configuration example.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The present invention is not limited to the above embodiments, and can be applied to various fields of a vehicle, a. In order to make the description clearer, the drawings schematically show the width, thickness, shape, and the like of each part as compared with the actual form, but the drawings are always an example and do not limit the explanation of the present invention. In the present specification and the drawings, the same reference numerals are given to the same elements as those described above in the conventional drawings, and detailed description thereof may be omitted as appropriate.

(embodiment mode)

Fig. 1 is a perspective view showing a display surface side of a liquid crystal display device according to an embodiment, and fig. 2 is an exploded perspective view of the liquid crystal display device.

The liquid crystal display device 10 can be incorporated into various electronic devices such as a smart phone, a tablet personal computer terminal, a mobile phone, a portable game machine, and an electronic dictionary television device, or vehicle-mounted devices such as a navigation system and an instrument panel.

As shown in fig. 1 and 2, the liquid crystal display device 10 includes: an active matrix type liquid crystal display panel 12; a cover panel 14 that is disposed so as to overlap the display surface 12a that is one surface of the liquid crystal display panel 12 and covers the entire display surface 12 a; and a backlight device (planar lighting device) 20 disposed to face the rear surface which is the other surface of the liquid crystal display panel 12. The backlight device 20 irradiates the liquid crystal display panel 12 with planar light from the rear side to illuminate the liquid crystal display panel 12.

As shown in fig. 2, the liquid crystal display panel 12 includes: a 1 st substrate SUB1 of a rectangular shape; a 2 nd substrate SUB2 having a rectangular shape, which is disposed to face the 1 st substrate SUB 1; and an unillustrated liquid crystal layer sealed between the 1 st substrate SUB1 and the 2 nd substrate SUB 2. The peripheral edge portion of the 2 nd substrate SUB2 is bonded to the 1 st substrate SUB1 by a seal material SE. A polarizing plate, not shown, is attached to the surface of the 2 nd substrate SUB2, thereby forming the display surface 12a of the liquid crystal display panel 12. In one example, each of 4 corner portions (corner portions) of the liquid crystal display panel 12 is formed in an arc shape rounded with a desired radius of curvature.

In the liquid crystal display panel 12, a rectangular display region (active region) DA is provided in a region inside the seal material SE in a plan view of the display surface 12 a. An image is displayed in the display area DA. A frame region (non-display region) ED having a frame shape is provided around the display region DA. The liquid crystal display panel 12 has a transmissive display function of selectively transmitting light from the backlight device 20 through the display area DA to display an image. The liquid crystal display panel 12 may be a display panel capable of touch input provided with a touch sensor not shown.

In the illustrated example, a flexible printed circuit board (FPC)22 is joined to an end portion of the 1 st substrate SUB1 on the one short side 12b side, and extends outward from the liquid crystal display panel 12. A semiconductor element such as the driver IC chip 21 is mounted on the FPC22 as a signal supply source for supplying a signal necessary for driving the liquid crystal display panel 12.

A rectangular or bathtub-shaped recess (or notch) 30 is formed in the other short side (short side on the opposite side of the light source) 12c of the liquid crystal display panel 12. The substantially central portions of the 1 st substrate SUB1 and the 2 nd substrate SUB2 in the longitudinal direction of the short sides are recessed inward, that is, toward the display area DA, thereby defining a substantially rectangular recessed portion 30. The seal material SE extends along the end edge of the recess 30.

The cover panel 14 is made of, for example, a glass plate or an acrylic transparent resin, and has a rectangular plate shape. The cover panel 14 covers the entire display surface 12a of the liquid crystal display panel 12. A frame-shaped light-shielding layer RS is formed on the peripheral edge of the back surface of the cover panel 14 (the surface on the liquid crystal display panel 12 side, or the surface opposite to the surface facing the viewer). The light-shielding layer RS may be formed on the upper surface (display surface) of the cover panel 14.

The back surface (back surface) of the cover panel 14 is bonded to the polarizing plate of the liquid crystal display panel 12 with an adhesive sheet made of a light-transmitting adhesive or pressure-sensitive adhesive, for example, an optically transparent resin.

Next, a configuration example of the backlight device 20 will be described in detail.

As shown in fig. 2, the backlight device 20 is formed in a rectangular plate shape having a size substantially equal to that of the liquid crystal display panel 12 as a whole. Each of the 4 corners (corner portions) of the backlight device 20 is formed in an arc shape rounded with a desired radius of curvature. A substantially rectangular concave portion 50 that is concave inward is provided on a side surface on one short side of the backlight device 20. The recess 50 is provided corresponding to the recess 30 of the liquid crystal display panel 12.

Fig. 3 is an exploded perspective view of the backlight device. As shown in fig. 2 and 3, the backlight device 20 includes a case (bezel) 24, a plurality of optical members disposed in the case 24, and a light source device 42 that supplies light incident on the optical members. In the present embodiment, the housing 24 has a rectangular-shaped frame 26 and a rectangular-shaped bottom plate 27 fixed to the back of the frame 26. The frame 26 and the bottom plate 27 may be made of resin or metal and integrally formed. Similarly, either one may be made of resin, and the other may be made of metal. In the present embodiment, the frame 26 is formed of resin, and the bottom plate 27 is formed of the reflective sheet RE. The frame 26 and the 4 corners of the reflective sheet RE are formed in a circular arc shape rounded with a desired radius of curvature. Further, a substantially rectangular recess 50A corresponding to the recess 50 is provided at the center of the frame 26 and the short side portion of the reflective sheet RE.

The optical member includes a light guide plate LG disposed on the reflective sheet RE in the frame 26, and a plurality of, for example, two 1 st optical sheets OS1 and 2 nd optical sheets OS2 disposed on the light guide plate LG in a superposed manner.

The light guide plate LG is formed in a rectangular plate shape and has: a 1 st main surface (emission surface) 36a facing the liquid crystal display panel 12; a 2 nd main surface (reflective surface) 36b located on the opposite side of the 1 st main surface and facing the reflective sheet RE; and a plurality of side surfaces (end surfaces) connecting the 1 st main surface 36a and the 2 nd main surface 36 b. That is, each of the plurality of side surfaces has a pair of long side surfaces (3 rd side surfaces) 40a and 40b extending along the long side of the 1 st main surface 36a and a pair of short side surfaces 40c and 40d extending along the short side of the 1 st main surface 36 a. One short-side surface (1 st side surface) 40c forms an incident surface of the light guide plate LG, and the other short-side surface (2 nd side surface) 40d forms an opposite-incident side surface.

The light guide plate LG includes: two 1 st corner portions C1, C2 where the short side surface (2 nd side surface) 40d and the long side surfaces (3 rd side surfaces) 40a, 40b, which are two corner portions on the opposite incident side, are connected; and two corner portions C3 at the incident side, i.e., two 3 rd corner portions C3 where the short side surface (1 st side surface) 40C at the incident side and the long side surfaces 40a and 40b at the incident side are connected. Each of the 4 corners (corner portions) of the light guide plate LG is formed in an arc shape rounded with a desired radius of curvature.

A substantially rectangular recess (or notch) 50B is provided substantially at the center of the short-side surface 40d on the opposite side from the incident side. The recess 50B is recessed toward the inside of the light guide plate LG, i.e., toward the incident surface 40c side. The bottom side portion of the recess 50B is located closer to the incident surface side than the 1 st corner portions C1, C2 of the light guide plate LG. In addition, the recess 50B is formed in a position and size corresponding to the recess 50A of the frame 26.

The optical sheets OS1 and OS2 each have light-transmitting properties and are placed on the emission surface 36a of the light guide plate LG so as to overlap the light guide plate LG. In the present embodiment, as the optical sheets OS1 and OS2, for example, a light diffusion sheet or a prism sheet made of synthetic resin such as polyethylene terephthalate is used. These optical sheets OS1 and OS2 are each formed in a rectangular shape having substantially the same size, and are sequentially stacked on the emission surface 36a of the light guide plate LG. The optical sheets OS1 and OS2 each have a substantially rectangular recess 50C formed in the center of one short side. The recess 50C is formed in a position and a size corresponding to the recess 50B of the light guide plate LG, and is disposed so as to overlap the recess 50B.

As shown in fig. 3, the light source device 42 has an elongated circuit board 44a and a plurality of light sources, for example, light emitting elements (LEDs) 44b, mounted on the circuit board 44 a. The circuit board 44a is attached to the frame 26 and the light guide plate LG by a double-sided tape or the like. The LEDs 44b face the incident surface 40c of the light guide plate LG, respectively. The LEDs 44b are arranged along the incident surface 40c, and emit light substantially over the entire incident surface 40 c. The light emitted from the LED44b enters the light guide plate LG through the entrance surface 40c, repeats reflection in the light guide plate LG, and then is emitted toward the liquid crystal display panel 12 from substantially the entire surface of the emission surface 36 a.

As shown in fig. 2 and 3, the light source device 42 and the peripheral edge portion of the optical sheet OS2 disposed so as to overlap the light guide plate LG and the optical sheet OS1 are attached to the frame 26 by a double-sided tape TP1 having a rectangular frame shape. The center portion of one short side of the double-sided tape TP1 is formed by being bent in a rectangular shape, i.e., recessed, along the recess 50.

An example of the structure of the light guide plate LG will be described in further detail.

The light guide plate LG is formed by injection molding of a synthetic resin. Fig. 4 is a plan view schematically showing an example of a mold used for injection molding, and fig. 5 is a plan view schematically showing a state in which the 1 st slide and the 2 nd slide are slid from the molding position to the take-out position.

In one example, the mold includes a fixed-side mold (1 st mold) 100 shown in the drawing and a movable-side mold (2 nd mold) not shown in the drawing that can be opened and closed with respect to the fixed-side mold 100. The 1 st mold 100 has: a substantially rectangular cavity CH having a shape and a size corresponding to the light guide plate LG; and a sprue 102 and a gate 104 that guide the molten resin to the cavity CH. The 1 st die 100 includes plate-shaped 1 st and 2 nd slides S1 and S2 provided to be movable (slidable) relative to the cavity CH.

The 1 st slider S1 has a formed end face ES1 defining one short side of the cavity CH. A substantially rectangular protrusion 106 is integrally formed at the longitudinal center of the molding end face ES 1. The convex portion 106 has a shape corresponding to the concave portion 50B of the light guide plate LG, and the concave portion 50B is formed in the light guide plate LG during molding. A pair of corner-forming pieces CP1 for forming corner portions of the light guide plate LG are provided at both longitudinal end portions of the forming end face ES1 of the 1 st slider S1. The pair of corner forming pieces CP1 can slide integrally with the 1 st slider S1.

The 1 st slider S1 is provided slidably between the forming position shown in fig. 4 and the removal position shown in fig. 5. At the forming position, the forming end face ES1 of the 1 st slider S1 and the pair of corner forming pieces CP1 are arranged at positions where the short sides of the cavity CH are formed. At the removal position, the forming end face ES1 and the pair of corner forming pieces CP1 of the 1 st slider S1 are separated from the short side of the formed product, that is, the short side of the light guide plate LG, and face the light guide plate LG with a slight gap therebetween.

The 2 nd slider S2 has a formed end face ES2 defining the other short side of the cavity CH. The formed end face ES2 is formed substantially flat. A pair of corner-forming pieces CP2 for forming corner portions of the light guide plate LG are provided at both longitudinal end portions of the formed end face ES 2. The pair of corner forming pieces CP2 can slide integrally with the 2 nd slider S2.

The 2 nd slider S2 is provided slidably between the forming position shown in fig. 4 and the removing position shown in fig. 5. At the forming position, the forming end face ES2 of the 2 nd slider S2 and the pair of corner forming pieces CP2 are arranged at positions where the short sides of the cavity CH are formed. At the removal position, the forming end face ES2 and the pair of corner forming pieces CP2 of the 2 nd slider S2 are separated from the short side of the formed product, that is, the short side of the light guide plate LG, and face the light guide plate LG with a slight gap therebetween.

In injection molding of the light guide plate LG, as shown in fig. 4, the cavity CH is filled with molten resin through the sprue 102 and the gate 104 while the 1 st slider S1 and the 2 nd slider S2 are held at the molding positions, respectively. After the resin solidified due to cooling, the 2 nd mold was opened, and the 1 st slider S1 and the 2 nd slider S2 were moved to the removal position, and they were separated from the molded article. In this state, the light guide plate LG as a molded product is ejected (taken out) from the 1 st mold 100.

By the above injection molding, the light guide plate LG having the concave portion 50B and the rounded 4 corner portions is molded. The concave portion 50B of the light guide plate LG is not formed by machining after molding, but is integrally molded by the convex portion 106 of the mold. Therefore, the inner surface (the pair of inner side surfaces and the inner bottom surface) of the predetermined concave portion 50B has the same surface roughness (for example, surface roughness Ra: 0.018. mu.m) as the other side surfaces and surfaces of the light guide plate LG. In the case where the recess 50B is formed by cutting, the surface roughness of the inner surface of the recess is, for example, Ra: since the thickness is about 0.151 μm, the surface roughness of the inner surface of the concave portion can be reduced by 1 digit or more by molding the concave portion 50B with a mold. Further, by adjusting the processing quality of the mold member, the surface roughness of the inner surface of the concave portion can be controlled.

Fig. 6 is a perspective view showing a short-side portion on the opposite-incidence side of the light guide plate LG. As shown in the drawing, the concave portion 50B of the light guide plate LG is defined by: a pair of inner side surfaces 51a extending from the short side surface 40d toward the incident surface and substantially parallel to the long side of the light guide plate LG; an inner bottom surface 51b extending parallel to the short side of the light guide plate LG between the extending ends of the pair of inner side surfaces 51 a; and two corner portions (corner 2) 51c connecting the inner side surface 51a and the inner bottom surface 51 b. As described above, by forming the concave portion 50B by injection molding, the surface roughness of the inner side surface 51a and the inner bottom surface 51B has the same surface roughness (for example, Ra: 0.018 μm) as the other side surfaces 40a to 40d and the 1 st main surface 36a and the 2 nd main surface 36B of the light guide plate LG. Since the surface roughness of the inner side surface 51a and the inner bottom surface 51B is small, the diffusion of light at the concave portion 50B can be reduced, and the increase in luminance at the edge of the concave portion 50B can be suppressed.

Fig. 7 is an enlarged plan view of a short-side portion on the opposite-to-incident side of the light guide plate LG. As shown in the drawing, in the case of a structure in which corner portions (1 st corner portion) C1, C2 on the opposite side to the incident side of the light guide plate LG are rounded, there are cases in which: among the incident light entering the light guide plate LG, light reflected and refracted by the corner portion C1 (or C2) and light reflected by the corner portion 51C of the concave portion 50B are concentrated to positions near the corner portions C1 and C2 on the short side of the light guide plate LG, and become bright points. Therefore, the light guide plate LG of the present embodiment has a structure for reducing light reflection at the corner 51c of the recess 50B. In one example, as a reduction structure, the curvature radius R of each corner 51c of the recess 50B is set to 0 to 3 mm. The radius of curvature of each corner 51c is set to approximately 0, and the corner is formed to be substantially perpendicular. As R approaches 0, the reflection light reflected from the corner 51C toward the corners C1 and C2 decreases. This can suppress the occurrence of bright spots near the corner portions.

As another example of the reduction structure, as schematically shown in fig. 8, the surface roughness of the corner portion 51c of the recess 50B may be formed to be larger than the surface roughness of the other portions of the recess 50B, i.e., the inner side surface 51a and the inner bottom surface 51B. In this case, too, the light reflection at the corner 51c can be reduced, and the same operational effects as described above can be obtained.

As still another reduction structure, as shown in fig. 9, a black film BP such as a black thin film may be provided by performing black printing on the corner 51c of the recess 50B to suppress light reflection. The black film BP may be provided on the entire inner surface 51a including the corner 51c and the entire inner bottom surface 51 b.

Further, the following configuration may be adopted: in the dot pattern formed on the 2 nd main surface 36b of the light guide plate LG, the pattern formation density of a region opposed to the vicinity of the corner portions C1 and C2 where the above-described bright dots are likely to occur is made lower than that of the other region, and the luminance of the region is positively reduced. By reducing the luminance, the luminance at the corner portions C1 and C2 of the light guide plate LG can be made uniform.

Fig. 10 is a plan view showing an incident-side end portion of the light guide plate LG, and fig. 11 is a perspective view showing the incident-side end portion of the light guide plate LG. When the corner portion C3 on the incident side short side of the light guide plate LG is rounded, it is difficult to dispose the LED44b of the light source device near the corner portion C3, particularly near the long side surfaces 40a and 40 b. Therefore, the amount of incident light at the corner portions of the light guide plate LG is small, and the light guide plate LG is likely to become dark.

Therefore, in the present embodiment, as shown in fig. 10, in the 1 st main surface 36a of the light guide plate LG, a plurality of guide grooves (for example, V-shaped grooves having a triangular cross section) 54 extending from the incident surface 40C toward the long side surface 40a are provided in a region including the corner portion C3 on the incident surface 40C side. That is, a plurality of guide grooves 54 inclined to the long side with respect to the optical axis of the LED44b are provided from the short side to one long side of the region facing the LED44b provided on the side closest to the corner portion C3. A part of light incident on the light guide plate LG from the LED44b provided on the side closest to the corner portion C3 propagates along the plurality of guide grooves 54, and illuminates a region near the corner portion C3 brightly. This can suppress a decrease in luminance at the corner C3 of the light guide plate LG. The other corner portion C3 of the light guide plate LG is also provided with a plurality of guide grooves 54 in the same manner as described above.

Fig. 12 is a plan view of an incident side end of a light guide plate showing another structural example of suppressing a decrease in luminance at a corner portion, and fig. 13 is a perspective view of the incident side end of the light guide plate.

As shown in the drawing, in another configuration example, the incident surface of the light guide plate LG is formed so that the region of the incident surface 40c2 facing the LED44b disposed most adjacent to the corner portion is inclined outward, that is, the long side of the light guide plate LG, and the emission surface of the LED44b is arranged so as to be inclined outward in accordance with the region of the incident surface 40c 2. That is, the incident surface 40c2 region is inclined at a predetermined angle with respect to the direction parallel to the short side of the light guide plate LG, to the opposite incident side and the long side. Thus, the light emitted from the LED44b is emitted toward the corner portion C3 of the light guide plate LG. Therefore, the corner portion C3 is brightly illuminated, and the luminance at the corner portion C3 can be suppressed from being lowered. The other corner portion C3 of the light guide plate LG is also configured in the same manner as described above.

Fig. 14 is a plan view of an incident-side end of a light guide plate showing another structural example for suppressing a decrease in luminance at a corner portion, and fig. 15 is a perspective view of the incident-side end of the light guide plate.

As shown by the two-dot chain line in fig. 15, normally, a plurality of vertical ridges (vertical ribs, vertical grooves) are formed across the entire surface of the 1 st main surface 36a of the light guide plate LG, and a pattern of a plurality of dot-shaped protrusions is formed on the 2 nd surface. Each of the longitudinal ridges extends substantially parallel to the long side from the short side on the incident surface 40c side to the short side on the opposite side to the incident light side in the 1 st main surface 36 a.

In the structural example of the present embodiment shown in fig. 14 and 15, at least the plurality of longitudinal ridges located in the long-side end region of the 1 st main surface 36a are removed, and the long-side end region is a flat mirror surface. Alternatively, all the longitudinal ridges may be omitted, and the entire surface of the 1 st main surface 36a may be a mirror surface.

Further, in the incident surface 40C of the light guide plate LG, a plurality of convex strips (ribs) 58 having a triangular cross section (V-shaped grooves) are provided at least in the incident surface region facing the LED44b provided on the side closest to the corner portion C3. The plurality of ribs 58 extend in the thickness direction of the light guide plate LG, and are arranged at predetermined intervals in the longitudinal direction of the incident surface 40 c. The plurality of ribs 58 may be provided on all the incident surface regions facing the plurality of LEDs 44 b. Further, the following configuration may be adopted: a plurality of ridges (ribs) having a semicircular cross section are provided on the other incident surface region except for the incident surface region facing the LED44b provided on the side closest to the corner portion C3.

According to the above-described configuration example, as shown by the one-dot chain line in fig. 14, the light emitted from the LED44b is diffused by the plurality of ribs (V-grooves) 58, and the light beam incident on the light guide plate LG is maximally spread, that is, the incident angle increases in the width direction of the light guide plate LG. Further, by making the long-side end of the emission surface 36a mirror surface, the emission from the incident emission surface of the light is suppressed. Thus, the light incident on the light guide plate LG from the LED44b is not immediately emitted from the emission surface 36a, but propagates to the corner portion C3 on the incident surface side of the light guide plate LG. This brightly illuminates the corner portion C3, and can suppress a decrease in brightness at the corner portion.

According to the backlight device 20 including the light guide plate LG and the light source device 42 configured as described above, it is possible to prevent the edge of the concave portion 50B provided at the short side portion from becoming excessively bright, and to suppress the occurrence of a bright point at the corner portion on the opposite incident side. Further, according to the backlight device 20, it is possible to suppress a decrease in luminance (light amount) at the corner portion C3 on the incident side of the light guide plate LG, and to emit illumination light of a desired light amount from the entire region of the emission surface 36a of the light guide plate LG. Thus, a backlight device and a liquid crystal display device capable of improving display quality are obtained.

The embodiments and the plurality of configuration examples of the present invention have been described, but these embodiments and configuration examples are provided as examples and are not intended to limit the scope of the present invention. The new embodiment can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. The embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

In the embodiments of the present invention, based on the above-described respective configurations, all configurations that can be implemented by those skilled in the art with appropriate design changes also fall within the scope of the present invention, as long as the gist of the present invention is included. For example, the concave portions provided in the liquid crystal display panel and the light guide plate are not limited to the rectangular shape and the bathtub shape, and various shapes such as a trapezoidal shape, an elliptical shape, and a semicircular shape can be selected. The width and depth of the recess are not limited to the dimensions shown in the drawings, and can be set arbitrarily.

The exit surfaces of the liquid crystal display panel and the light guide plate are not limited to flat surfaces, and may have a shape at least a part of which is curved, a curved surface which is concave in the longitudinal direction, or a curved surface which is convex in the longitudinal direction. The components of the liquid crystal display panel and the backlight device are not limited to rectangular shapes, and may have other shapes such as polygonal shapes having five or more sides, elliptical shapes, racetrack shapes, and the like. The material of the constituent members is not limited to the above examples, and can be variously selected.

As for other operational effects by the above-described embodiment or modification, the operational effects that become clear from the description of the present specification or the operational effects that can be appropriately thought by those skilled in the art are of course understood to be the operational effects by the present invention.

Claims (10)

1. A backlight device is characterized in that a backlight unit,

the backlight device comprises a light guide plate and a light source for emitting light to the light guide plate,

the light guide plate has a 1 st main surface forming an emission surface, a 2 nd main surface opposite to the 1 st main surface, and a side surface connecting the 1 st main surface and the 2 nd main surface,

the side surface has a 1 st side surface forming an incident surface opposed to the light source, a 2 nd side surface opposed to the 1 st side surface, and a pair of 3 rd side surfaces connected to the 1 st side surface and the 2 nd side surface, respectively,

the 2 nd side surface and the 3 rd side surface are connected at a 1 st corner portion,

the 2 nd side surface has a concave portion located closer to the incident surface side than the 1 st corner portion,

the concave part is provided with an inner side surface opposite to the 3 rd side surface and an inner bottom surface opposite to the 1 st side surface, the inner side surface and the inner bottom surface are connected by a 2 nd corner part in an arc shape,

the surface roughness of the 2 nd corner part is larger than the surface roughness of the inner bottom surface.

2. The backlight device according to claim 1,

the radius of curvature of the 2 nd corner part is 0 to 3 mm.

3. The backlight device according to claim 1,

the inner side surface has a surface roughness common to the surface roughness of the 3 rd side surface,

the surface roughness of the 2 nd corner portion is larger than the surface roughness of the 3 rd side surface.

4. The backlight device according to claim 1,

the backlight device has a black film formed at the 2 nd corner portion.

5. The backlight device according to claim 1,

the 1 st side surface and the 3 rd side surface are connected by a 3 rd corner part, and the 3 rd corner parts are respectively rounded into circular arc shapes.

6. The backlight device according to claim 5,

the light source includes a plurality of light emitting elements arranged to face the incident surface of the light guide plate, the plurality of light emitting elements being arranged at predetermined intervals from one end to the other end of the incident surface in the longitudinal direction,

the light guide plate has a plurality of guide grooves formed in the 1 st main surface in the vicinity of the 3 rd corner portion, and the plurality of guide grooves extend obliquely to the 3 rd side surface side with respect to the optical axis of the light emitting element from the vicinity of the light emitting element disposed most adjacent to the 3 rd corner portion to the end edge of the 3 rd side surface.

7. The backlight device according to claim 5,

the light source includes a plurality of light emitting elements arranged to face the incident surface of the light guide plate, the plurality of light emitting elements being arranged at predetermined intervals from one end to the other end of the incident surface in the longitudinal direction,

in the incident surface, an incident surface region facing the light emitting element disposed most adjacent to the 3 rd corner portion is inclined toward the 3 rd side surface with respect to a direction parallel to the 1 st side surface of the light guide plate, and the light emitting element is disposed so as to be inclined toward the 3 rd side surface in accordance with the incident surface region.

8. The backlight device according to claim 5,

the light source includes a plurality of light emitting elements arranged to face the incident surface of the light guide plate, the plurality of light emitting elements being arranged at predetermined intervals from one end to the other end of the incident surface in the longitudinal direction,

the light guide plate integrally has a plurality of ribs having a triangular cross section and provided on the incident surface,

the plurality of ribs extend in a direction intersecting the 1 st main surface and are arranged in a direction parallel to the 1 st main surface,

the light emitting element disposed at least most adjacent to the 3 rd corner portion is disposed so as to face the plurality of ribs.

9. The backlight device according to claim 8,

at least an end region on the 3 rd side surface side of the 1 st main surface of the light guide plate is formed as a flat mirror surface.

10. A liquid crystal display device is characterized in that,

the liquid crystal display device includes:

a liquid crystal display panel; and

the backlight device according to any one of claims 1 to 9, which is provided opposite to a back surface of the liquid crystal display panel.

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