JP2018022593A - Light guide plate, surface light source device, display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate, a surface light source device and a display device capable of increasing the amount of component emitting toward a normal direction of a plate surface out of the light entering from an end surface, and capable of enhancing utilization efficiency of the light.SOLUTION: A light guide plate 12 includes: an incident surface 12a which is one end surface of the light guide plate 12 formed in a tabular shape, and which the light enters; an emission surface 12b which crosses the incident surface 12a and from which the light emits; an observer side surface 12c opposing to the emission surface 12b; and an opposing surface 12d opposing to the incident surface 12a. The light guide plate 12 guides the light which has entered from the incident surface 12a to the opposing surface 12d side and emits it from the emission surface 12b. The light guide plate also includes a plurality of semi-transmissive reflection parts 12g arranged inside the light guide plate 12, and for transmitting a predetermined ratio of the light and for reflecting the remaining light to the emission surface 12b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a light guide plate, a surface light source device, and a display device.

There is known a display device that displays an image by illuminating a display unit such as an LCD (Liquid Crystal Display) panel with a surface light source device.
Surface light source devices are broadly classified into a direct type in which a light source is arranged directly under an optical member such as various optical sheets and an edge light type in which a light source is arranged on an end surface (side surface) of the optical member. Among these, the edge light type surface light source device has the advantage that the surface light source device can be made thinner than the direct type because the light source is disposed on the end face of the optical member such as a light guide plate, It is used.
In addition, the edge light type surface light source device is widely used not only as a backlight of a display device but also as a front light in recent years.

  In the edge light type surface light source device, a light source is arranged on the side surface of an optical member, and the light from the light source is deflected so as to be light directed from the plate surface to the display unit and used as illumination light. . For this reason, as the light guide plate, for example, as disclosed in Patent Document 1, a plate in which fine protrusions are arranged on the light output side is known.

JP 2011-209333 A

  Although the direction of light emitted from the light guide plate varies depending on the application, there is generally a demand for light to be emitted in the normal direction of the plate surface. However, in the light guide plate in the form as in Patent Document 1, it is possible to generate a component that emits light from the end surface in a direction close to the normal direction of the plate surface, but much light is in an unnecessary oblique direction. The light use efficiency was low.

  The problem of the present invention is that a light guide plate, a surface light source device, and a light source plate that can increase the component that emits light in the normal direction of the plate surface out of the light incident from the end face and can improve the light utilization efficiency, It is to provide a display device.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

  1st invention cross | intersects the light-incidence surface (12a, 212a) which is one end surface of the light-guide plate (12,212) comprised by plate shape, and the light injects, and the said light-incidence surface (12a, 212a). A light exit surface (12b, 212b) from which light is emitted, a front surface (12c, 212c) facing the light exit surface (12b, 212b), and a facing surface (12d, 212a) facing the light incident surface (12a, 212a). 212d), and guides light incident from the light incident surfaces (12a, 212a) to the opposing surfaces (12d, 212d) and emits the light from the light exit surfaces (12b, 212b). , 212), which are arranged in the light guide plate (12, 212) and transmit a predetermined proportion of light and reflect the remaining light toward the light exit surface (12b, 212b). Light guide plate (12g) having a portion (12g) 212) is.

  According to a second invention, in the light guide plate (12, 212) according to the first invention, a light output layer (122) including the light output surface (12b, 212b) and a front layer including the front surface (12c, 212c). (121), and the transflective portion (12g) is disposed at an interface between the light output layer (122) and the front layer (121). 12, 212).

  According to a third aspect of the present invention, in the light guide plate (12, 212) according to the second aspect, the light-transmitting layer (122) and the front layer (121) can constitute the transflective portion (12g). A plurality of unit shapes (121a, 122a) having slopes (12e) are continuously arranged along the direction from the light incident surface (12a, 212a) toward the opposing surface (12d, 212d) to form the interface. The light-transmitting plate (12, 212) is characterized in that the transflective portion (12g) is provided only at a specific portion of the inclined surface (12e).

  According to a fourth aspect of the present invention, in the light guide plate (12, 212) according to the third aspect of the present invention, the transflective portion (12g) is arranged in accordance with the distance from the light incident surface (12a, 212a). The light guide plate (12, 212) is characterized in that the density is high.

  According to a fifth aspect of the present invention, in the light guide plate (212) according to any one of the first to fourth aspects of the present invention, an incident light control unit that deflects incident light on the light incident surface (212a) ( 212h) is provided, which is a light guide plate (212).

  A sixth invention is the light guide plate (12, 212) according to any one of the first to fifth inventions, and the light incident surface (12a, 212a) of the light guide plate (12, 212). A surface light source device (10) comprising: a light source unit (11) disposed opposite to and projecting light onto the light incident surfaces (12a, 212a).

  A seventh aspect of the invention is a surface light source device (10) according to the sixth aspect of the invention and a reflective display section (13) disposed on the light exit surface (12b, 212b) side of the surface light source device (10). And a display device (1).

  According to an eighth aspect of the present invention, there is provided the surface light source device (10) according to the sixth aspect of the present invention, and a transmission type display unit disposed on the light exit surface (12b, 212b) side of the surface light source device (10). A display device provided.

  According to the present invention, a light guide plate, a surface light source device, and a light source plate that can increase the amount of light emitted from the end face to the normal direction of the plate surface and increase the light utilization efficiency. A display device can be provided.

It is a figure which shows 1st Embodiment of the display apparatus 1 using the light-guide plate 12 by this invention. 4 is a cross-sectional view of the surface light source device 10 cut in a direction (XZ plane) orthogonal to the plate surface of the light guide plate 12 and orthogonal to the light incident surface in the vicinity of the light source unit 11. FIG. It is the figure which looked at the surface light source device 10 from the front direction (+ Z side). It is a figure which shows the example of the optical path in the surface light source device 10 of 1st Embodiment. It is a figure which shows the example of the optical path in the light-guide plate 500 of a comparative example. It is a perspective view which shows the light-guide plate 212 in 2nd Embodiment of this invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a first embodiment of a display device 1 using a light guide plate 12 according to the present invention.
In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
In the following description, specific numerical values, shapes, materials, and the like are shown and described, but these can be changed as appropriate.
In this specification, terms that specify shape and geometric conditions, for example, terms such as parallel and orthogonal, are strictly meanings, have similar optical functions, and can be regarded as parallel and orthogonal. It also includes a state having an error.
In the present specification, the plate surface refers to a surface in the planar direction of each plate-like member when viewed as the whole plate-like member.

Further, in the following drawings including FIG. 1 and the following description, an XYZ coordinate system is set for easy understanding. In the state of use of the display device 1, the direction orthogonal to the light incident surface 12 a of the light guide plate 12 among the two directions parallel to the screen of the display device 1 and orthogonal to each other is defined as the X direction, and the direction orthogonal to the X direction is defined as Y. The direction. Further, a direction (thickness direction) orthogonal to the screen of the display device 1 is defined as a Z direction. In the thickness direction (Z direction), the + Z side is the observer side, and the −Z side is the back side.
The screen of the display device 1 of this embodiment corresponds to the surface (hereinafter referred to as the display surface) 10a on the most + Z side (observer side) of the surface light source device 10, and the “front direction” of the display device 1 is this It is the normal direction of the display surface 10a, is parallel to the Z direction, and coincides with the normal direction of the plate surface of the light guide plate 12 described later.

  The display device 1 of this embodiment includes a surface light source device 10 and a reflective LCD panel 13. The display device 1 illuminates the reflective LCD panel 13 with the surface light source device 10 from the observer side, and displays video information formed on the reflective LCD panel 13. In addition, you may provide a touch panel, a protection panel, etc. in the observer side further in the surface light source device 10 as needed. The display device 1 of the present embodiment is used as, for example, a large screen advertisement or signboard of 30 inches or more. The present invention is not limited to such a large screen, and may be used for a smaller portable terminal or the like.

  The reflective LCD panel 13 is a reflective display unit that is formed of a liquid crystal display element and forms video information on its display surface. The reflective LCD panel 13 is formed in a substantially flat plate shape. The external shape of the reflective LCD panel 13 is rectangular when viewed from the Z direction, and has two opposing sides parallel to the X direction and two opposing sides parallel to the Y direction.

FIG. 2 is a cross-sectional view of the surface light source device 10 cut in the direction (XZ plane) perpendicular to the light guide plate 12 and perpendicular to the light incident surface in the vicinity of the light source unit 11.
The surface light source device 10 is a device that illuminates the reflective LCD panel 13 from the observer side (+ Z side), and includes a light source unit 11 and a light guide plate (front light guide plate) 12. The surface light source device 10 is an edge light type surface light source device (front light) that receives light from an end surface.

The light source unit 11 emits light that illuminates the reflective LCD panel 13. The light source unit 11 is disposed along the Y direction at a position facing the light incident surface 12a which is one end surface (+ X side) of the light guide plate 12 in the X direction (+ X side).
The light source unit 11 is formed by arranging a plurality of point light sources at predetermined intervals in the Y direction. As this point light source, an LED (Light Emitting Diode) light source is used. The light source unit 11 may be, for example, a line light source such as a cold cathode tube, or may have a form in which a light source is disposed on an end surface of a light guide extending in the Y direction.
Further, from the viewpoint of improving the utilization efficiency of light emitted from the light source unit 11 and shielding unnecessary light, a reflection plate (not shown) or a shielding plate may be provided so as to cover the outside of the light source unit 11. .

The light guide plate 12 constituting the surface light source device 10 has a rectangular shape when viewed from the front direction (Z direction), and has two opposite sides parallel to the X direction and two opposite sides parallel to the Y direction. ing.
The light guide plate 12 has a light incident surface 12a, a light exit surface 12b, an observer side surface 12c, and a facing surface 12d on its outer peripheral surface.

  The light incident surface 12 a is provided on one end surface (+ X side end surface) of the light guide plate 12, and light from the light source unit 11 is incident thereon.

  The light exit surface 12b is provided on a surface intersecting the light entrance surface 12a, and light incident from the light entrance surface 12a is emitted. In the present embodiment, the light exit surface 12b is provided on the −Z side surface.

  The observer side surface (front surface) 12c is disposed on a surface facing the light exit surface, and the observer observes an image displayed on the reflective LCD panel 13 from the observer side surface 12c side.

  The facing surface 12d is disposed at a position facing the light incident surface 12a.

The light guide plate 12 includes two layers, a front layer 121 and a light output layer 122.
The front layer 121 is configured on the side including the observer side surface 12c, and is configured by curing a resin having optical transparency.
The light output layer 122 is configured on the side including the light output surface 12b, and is configured by curing a resin having optical transparency. The front layer 121 and the light emitting layer 122 are preferably made of the same material. For example, both the front layer 121 and the light-emitting layer 122 may be ultraviolet curable resins. For example, one of the front layer 121 and the light output layer 122 may be made of an ultraviolet curable resin, and the other may be a polycarbonate resin.
The interface between the front layer 121 and the light-emitting layer 122 has a shape in which the inclined surface 12e and the vertical surface 12f are continuously combined, as shown by the alternate long and short dash line in FIG.
Moreover, the transflective part 12g is provided in the specific several slope among the slopes 12e of the interface of the front layer 121 and the light emission layer 122. As shown in FIG. In FIG. 12, this transflective portion is indicated by a thick solid line. A plurality of transflective portions 12g are arranged inside the light guide plate 12, and reflect the remaining light after transmitting a predetermined proportion of the light incident from the light incident surface 12a toward the light exit surface 12b. It is configured as follows.

When the light guide plate 12 is manufactured, either the front layer 121 or the light-emitting layer 122 is first manufactured, and a film that becomes the semi-transmissive reflection portion 12g is formed only on the predetermined inclined surface 12e. The other layer can be formed by applying and curing a softened resin to the layer prepared.
For example, when the front layer 121 is first produced, the front layer 121 is produced by resin molding using a molding die having a mold shape corresponding to the shape of the inclined surface 12e and the vertical surface 12f. And in the produced front layer 121, it will be in the state by which the unit shape 121a provided with the inclined surface 12e and the vertical surface 12f was arrange | positioned continuously. Of these many slopes 12e, only a specific slope 12e determined in advance is formed with a metal thin film by a method such as sputtering or vapor deposition to produce a transflective portion 12g. By adjusting the film thickness at this time, it is possible to arbitrarily set the light quantity ratio between the light transmitted through the transflective portion 12g and the reflected light. After the transflective portion 12g is manufactured, a light-emitting layer 122 having a unit shape 122a having a reverse shape corresponding to the unit shape 121a is formed by applying and curing a softened resin that becomes the light-emitting layer 122 thereon. Thus, the light guide plate 12 is completed. Note that the light-emitting layer 122 may be formed first.

FIG. 3 is a view of the surface light source device 10 as viewed from the front direction (+ Z side). In FIG. 3, the position where the transflective portion 12g is provided is indicated by hatching.
The transflective portion 12g is provided only for a predetermined specific portion of the large number of inclined surfaces 12e. FIG. 3 shows an arrangement example of the transflective portion 12g.
For example, in the arrangement example of FIG. 3A, the transflective portions 12g are not provided on all of the inclined surfaces 12e, but are arranged in a thinned form according to a predetermined rule. Further, the closer to the light source unit 11, the lower the density of the transflective part 12 g, and the higher the density of the transflective part 12 g as the distance from the light source unit 11 increases. In the example of FIG. 3A, on the inclined surface 12e provided with the semi-transmissive reflecting portion 12g, the semi-transmissive reflecting portion 12g is uniformly arranged in the direction parallel to the light incident surface 12a (Y direction). ing.

Further, for example, as in the arrangement example shown in FIG. 3B, the transflective portion 12g also has a specific position with respect to the arrangement in the direction (Y direction) parallel to the light incident surface 12a. May be provided only for.
Furthermore, although both FIG. 3A and FIG. 3B are arranged according to a predetermined rule, they may be arranged more randomly.

FIG. 4 is a diagram illustrating an example of an optical path in the surface light source device 10 of the first embodiment. Since FIG. 4 exaggerates the size of each part, the optical path also exaggerates the deflection due to refraction and the like rather than the actual optical path.
In the surface light source device 10 of the present embodiment, among the light incident on the light incident surface 12a from the light source unit 11, the light that obliquely reaches the observer side surface 12c is air on the outside of the observer side surface 12c and has a refractive index. Is lower than the light guide plate 12, the light is totally reflected by the inner surface of the observer side surface 12 c and proceeds to the left side in FIG. 4 (the direction of −X: the light guide direction).
On the other hand, the light that reaches the light exit surface 12b diagonally is air outside and has a refractive index lower than that of the light guide plate 12. Therefore, the light is totally reflected by the inner surface of the light exit surface 12b, and the left side in FIG. Direction: the light guiding direction).

In this way, the light incident from the light incident surface 12a is guided through the light guide plate 12 from the light incident surface 12a toward the opposing surface 12d (-X direction: light guide direction).
At this time, when the guided light reaches the transflective portion 12g, a predetermined proportion of the light (for example, half) is reflected by the transflective portion 12g and travels toward the light exit surface 12b. The remaining light passes through the transflective part 12g and continues in the light guide direction. The light traveling toward the light exit surface 12b is emitted from the light exit surface 12b if the incident angle on the light exit surface 12b is an angle that does not satisfy the total reflection condition (an angle that does not exceed the critical angle).
Further, for light traveling in parallel to the plate surface of the light guide plate 12 from the light incident surface 12a, when a light reaches the semi-transmissive reflective portion 12g, a predetermined proportion of the light (for example, half) is transmitted by the semi-transmissive reflective portion. Reflected by 12g and directed to the light exit surface 12b, the remaining light passes through the transflective portion 12g and continues in the light guiding direction.

Here, the operation and effect of the light guide plate 12 of the present embodiment will be described below, using as a comparative example the light guide plate 500 conventionally used for a front light and provided with a plurality of fine protrusions on the light output side.
FIG. 5 is a diagram illustrating an example of an optical path in the light guide plate 500 of the comparative example.
In the light guide plate 500 of the comparative example, a large number of fine protrusions 501 protrude from the light output surface side. The light that has entered the light guide plate 500 from the light source unit 11 travels through the light guide plate 500 while repeating total reflection, and when reaching the protrusion 501, the light does not satisfy the total reflection condition and is emitted from the protrusion 501. However, in the light guide plate 500 of the comparative example, the light component that emits light in a direction close to the normal direction (Z-axis direction) of the light guide plate 500 is small, and the light component that forms a large angle with the Z-axis direction. Is increasing.

Thus, it can be seen that the surface light source device 10 including the light guide plate 12 of the present embodiment can use light very efficiently as compared with the comparative example.
As described above, the surface light source device 10 including the light guide plate 12 of the first embodiment includes the transflective portion 12g, so that the normal of the plate surface out of the light incident from the light incident surface 12a. The number of components that emit light toward the direction can be increased, and the light utilization efficiency can be increased.

(Second Embodiment)
FIG. 6 is a perspective view showing the light guide plate 212 in the second embodiment of the present invention.
The light guide plate 212 of the second embodiment has the same form as the light guide plate 12 of the first embodiment, except that the incident light control unit 212h is provided on the light incident surface 212a. Therefore, the overlapping description is appropriately omitted with respect to the portion that performs the same function as that of the first embodiment described above.

The light guide plate 212 of the second embodiment has a light incident surface 212a, a light outgoing surface 212b, an observer side surface 212c, and a facing surface 212d on its outer peripheral surface. Among these, the light output surface 212b, the observer side surface 212c, and the opposing surface 212d are the same as the light output surface 12b, the observer side surface 12c, and the opposing surface 12d of the first embodiment, respectively. The light guide plate 212 of the second embodiment includes a transflective portion 12g similar to the light guide plate 12 of the first embodiment.
Here, an incident light control unit 212h that deflects light incident from the light source unit 11 is provided on the light incident surface 212a of the second embodiment. The incident light control unit 212h of the present embodiment is configured in a single convex lens shape that protrudes toward the light source unit 11 side.

  According to the second embodiment, since the incident light control unit 212h is further provided, the traveling direction of light can be controlled in the extending direction (Y-axis direction) of the light source unit 11.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.

(1) In each embodiment, although the material which comprises a light-guide plate is described concretely, not only this but material can be selected suitably. For example, the light guide plate may be configured by curing an ultraviolet curable resin.

(2) In each embodiment, the inclined surface 12e provided with the semi-transmissive reflecting portion 12g has been described with an example of a flat inclined surface. For example, the slope may be a curved slope.

(3) In the second embodiment, the incident light control unit 212h has been described with an example in which the incident light control unit 212h is configured in one convex lens shape protruding toward the light source unit 11 side. For example, the incident light control unit may be configured by arranging a plurality of minute lens shapes, prism shapes, and the like.

(4) In each embodiment, the example which uses the surface light source device 10 as a front light which illuminates the reflection type LCD panel 13 which is a reflection type display apparatus from the front was given and demonstrated. For example, the surface light source device 10 may be used as a backlight that illuminates a transmissive display device from the back.

  In addition, although 1st Embodiment-2nd Embodiment and modification can also be used in combination suitably, detailed description is abbreviate | omitted. Further, the present invention is not limited by the embodiments described above.

DESCRIPTION OF SYMBOLS 1 Display apparatus 10 Surface light source device 10a Display surface 11 Light source part 12 Light guide plate 12a Light incident surface 12b Light exit surface 12c Observer side surface 12d Opposite surface 12e Slope 12f Vertical surface 12g Transflective part 13 Reflective LCD panel 121 Front layer 121a Unit Shape 122 Light exit layer 122a Unit shape 212 Light guide plate 212a Light incident surface 212b Light exit surface 212c Observer side surface 212d Opposing surface 212h Incident light control unit 500 Light guide plate 501 Projection

Claims (8)

A light incident surface on one end surface of the light guide plate configured in a plate shape, on which light is incident;
A light exit surface that intersects the light entrance surface and emits light;
A front surface facing the light exit surface;
A facing surface facing the light incident surface;
A light guide plate that guides light incident from the light incident surface to the opposite surface side and emits the light from the light exit surface,
A light guide plate including a transflective portion that is disposed in a plurality in the light guide plate and reflects the light remaining after transmitting a predetermined ratio of light toward the light exit surface. The light guide plate according to claim 1,
A light-emitting layer including the light-emitting surface;
A front layer including the front,
With
The transflective portion is disposed at an interface between the light-emitting layer and the front layer;
A light guide plate characterized by The light guide plate according to claim 2,
In the light-emitting layer and the front layer, a plurality of unit shapes having slopes capable of forming the transflective portion are continuously arranged along the direction from the light incident surface toward the facing surface to constitute the interface. Has been
The transflective part is provided only in a specific part of the slope;
A light guide plate characterized by The light guide plate according to claim 3,
The semi-transmissive reflection portion has a dense density as the distance from the light incident surface increases.
A light guide plate characterized by In the light-guide plate of any one of Claim 1- Claim 4,
An incident light control unit for deflecting incident light is provided on the light incident surface;
A light guide plate characterized by The light guide plate according to any one of claims 1 to 5,
A light source unit disposed opposite to the light incident surface of the light guide plate and projecting light onto the light incident surface;
A surface light source device comprising: A surface light source device according to claim 6;
A reflective display unit disposed on the light exit surface side of the surface light source device;
A display device comprising: A surface light source device according to claim 6;
A transmissive display unit disposed on the light exit surface side of the surface light source device;
A display device comprising:

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