JP2010033772A - Light guide plate, light-emitting device, liquid crystal display, and manufacturing method of light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate capable of improving utilization efficiency of light propagating inside a substrate, to provide a light-emitting device, to provide a liquid crystal display, and to provide a manufacturing method of the light guide plate. <P>SOLUTION: The light guide plate is provided with a substrate for propagating light incident from a light source, and conversion part fitted in adjacency to one of the main faces of the substrate and equipped with a diffraction grating on a face opposed to the face adjacent to the main face of the substrate. A refraction index of the conversion part is to be higher than that of the substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide plate, a light emitting device, a liquid crystal display device, and a method for manufacturing the light guide plate.

  In recent years, a high-luminance light-emitting device has been demanded. For example, liquid crystal display devices and the like are required to have high luminance display characteristics, and light emitting devices (backlight units) provided in the liquid crystal display devices and the like are required to have high luminance. It is coming.

  Here, a planar light emitting device (backlight unit) provided in a liquid crystal display device or the like is provided on the back side of the display surface of the liquid crystal display panel, that is, opposed to the main surface of the array substrate, and has a light emission surface. A light guide plate, and a light source disposed opposite to the side edge of the light guide plate. In such a light emitting device, high luminance is achieved by using a high luminance light emitting diode or the like as a light source. In addition, a technique for increasing the luminance of the light emitting device by improving the light use efficiency in the light guide plate has been proposed (see Patent Documents 1 and 2).

For example, Patent Document 1 discloses a technique in which a diffusion film and a prism sheet are stacked on a light exit surface of a substrate provided on a light guide plate. In the technique disclosed in Patent Document 1, light that has propagated inside the substrate is diffused by a diffusion film, and the optical path of the diffused light is controlled by a prism sheet, thereby improving the light utilization efficiency. I am doing so.
However, since the diffusion film and the prism sheet are provided by being laminated, the configuration is complicated and the cost is increased.

Therefore, a technique that does not use a diffusion film and a prism sheet, such as the technique disclosed in Patent Document 2, has been proposed.
In the technique disclosed in Patent Document 2, a thin film layer having a refractive index higher than that of the substrate is formed on the light exit surface of the substrate provided on the light guide plate. The light utilization efficiency is improved by preventing the light propagating through the substrate from being totally reflected by the light exit surface of the substrate.
However, according to Snell's law, in the case of only the substrate (when a thin film layer having a high refractive index is not provided), when light propagating inside the substrate is totally reflected at the interface between the substrate and air When a thin film layer with a high refractive index is provided, light propagating through the substrate enters the thin film layer with a high refractive index and changes its angle by refraction. The original propagation angle inside the substrate when reflected is equal. For this reason, there is no change in the conditions when the light propagating through the substrate is totally reflected by the light emitting surface, and there is a possibility that the light use efficiency cannot be improved.
JP 2006-119411 A JP 2005-251655 A

  The present invention provides a light guide plate, a light emitting device, a liquid crystal display device, and a method for manufacturing the light guide plate that can improve the utilization efficiency of light propagating through the inside of the substrate.

  According to one aspect of the present invention, a substrate that propagates light incident from a light source and a surface that is provided adjacent to one main surface of the substrate and that faces the surface adjacent to the main surface of the substrate are diffracted. There is provided a light guide plate comprising: a conversion portion having a grating, wherein the refractive index of the conversion portion is higher than the refractive index of the substrate.

  According to another aspect of the present invention, there is provided a light emitting device comprising: the light guide plate described above; and a light source provided to face the light incident surface of the light guide plate. .

  According to another aspect of the present invention, the light emitting device includes the above light emitting device, and a liquid crystal display panel provided to face the light emitting surface of the light guide plate included in the light emitting device. A liquid crystal display device is provided.

  According to another aspect of the present invention, the diffraction grating is formed on one main surface of the conversion unit using a mold in which an uneven part for transferring the shape of the diffraction grating is formed, and the conversion unit There is provided a method of manufacturing a light guide plate, characterized in that a substrate having a refractive index lower than the refractive index of the converter is provided on a surface facing the surface on which the diffraction grating is formed.

  Further, according to another aspect of the present invention, an uneven portion for transferring the shape of the diffraction grating is formed by bonding the conversion portion and a substrate having a refractive index lower than the refractive index of the conversion portion. There is provided a method of manufacturing a light guide plate, wherein a diffraction grating is formed on a main surface of the conversion unit using a mold.

  According to the present invention, a light guide plate, a light emitting device, a liquid crystal display device, and a method for manufacturing the light guide plate that can improve the utilization efficiency of light propagating through the substrate are provided.

  Hereinafter, embodiments of the present invention will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.

FIG. 1 is a schematic view for illustrating a light guide plate and a light emitting device according to the present embodiment.
FIG. 2 is a schematic view for illustrating a light guide plate and a light emitting device according to a comparative example.
First, a light guide plate and a light emitting device according to a comparative example illustrated in FIG. 2 will be described.
As shown in FIG. 2, the light emitting device 100 is provided with a light guide plate 101 and a light source 102. The light guide plate 101 is formed of a transparent material so that light incident from the light source 102 can be propagated. A light exit surface 103 is provided on one main surface of the light guide plate 101, and a diffraction grating 104 is provided on the light exit surface 103. A light incident surface 105 is provided on one end surface of the light guide plate 101 in a direction substantially orthogonal to the light emitting surface 103. The light incident surface 105 is polished as necessary so that the incidence of light is not hindered. A light source 102 is provided so as to face the light incident surface 105.

  Examples of the material of the light guide plate 101 include transparent organic materials such as acrylic resin and polycarbonate resin, and transparent inorganic materials such as glass. Further, as the diffraction grating 104 provided on the light emitting surface 103, one having a rectangular cross-sectional shape as illustrated in FIG. 2 can be exemplified. However, the cross-sectional shape of the diffraction grating 104 is not limited to this, and can be changed as appropriate. If the period (pitch) of the diffraction grating 104 is about 400 to 500 nm, light can be emitted in a direction (front side) substantially orthogonal to the light emission surface 103.

  Examples of the light source 102 include an LED (light emitting diode) and a CCFL (cold cathode ray tube). The light source 102 may emit white light, or may emit red, green, blue, or a mixed color thereof. Further, only one light source 102 may be provided, or a plurality of light sources 102 may be provided.

  As shown in FIG. 2, the light emitted from the light source 102 enters the light guide plate 101 from the light incident surface 105. If light is emitted from the light source 102 in all directions and the light incident surface 105 is flat, the propagation angle θ2 of light propagating through the light guide plate 101 is determined by the refractive index of the light guide plate 101 and the outside air (air). And the refractive index. That is, the propagation angle θ2 is determined according to Snell's law. For example, when the refractive index of the light guide plate 101 is about 1.45 (for example, glass), the propagation angle θ2 is about 46 ° to 90 °. As described above, the propagation angle θ2 of the light propagating through the light guide plate 101 is relatively wide. The propagation angle θ <b> 2 is an angle with respect to a direction orthogonal to the light exit surface 103. Further, the propagation angle θ <b> 2 is also an incident angle when entering the diffraction grating 104. Note that the light may be incident on the inside of the light guide plate 101 by changing the light distribution angle with a lens or the like as necessary.

  The light propagating through the light guide plate 101 is totally reflected at the interface between the surface of the light guide plate 101 facing the light exit surface 103 and the outside air (air). Then, the light is incident on the diffraction grating 104 at an angle θ 2 at the interface between the light emitting surface 103 and the outside air (air), and a part of the light is extracted into the air by the diffraction effect, and the remaining light enters the light guide plate 101. Reflected. Note that the efficiency when a part of light is extracted by the diffraction effect is the diffraction efficiency. That is, if the diffraction efficiency can be improved, light can be extracted efficiently.

  Here, if light can be emitted from the light exit surface 103 over the entire range of the propagation angle θ2 (incident angle to the diffraction grating 104), the light utilization efficiency can be improved. However, according to the knowledge obtained by the present inventors, it has been found that the diffraction efficiency decreases as the propagation angle θ2 (incident angle to the diffraction grating 104) increases.

  FIG. 3 is a graph for illustrating the relationship between the incident angle (propagation angle θ2) to the diffraction grating and the diffraction efficiency. In this case, the light guide plate 101 has a refractive index of 1.45, a light wavelength of 530 nm, a diffraction grating 104 having a rectangular cross section, and a period (pitch) of 500 nm. As shown in FIG. 3, the diffraction efficiency decreases as the incident angle (propagation angle θ2) on the diffraction grating 104 increases. In addition, even in the above-described range of 46 ° to 90 °, if the incident angle (propagation angle θ2) increases, the diffraction efficiency further decreases.

  That is, only light having a small propagation angle θ2 out of light propagating through the light guide plate 101 can be efficiently emitted. For this reason, if the entire range of the propagation angle θ2 is considered, the light utilization efficiency is lowered.

FIG. 4 is a graph for illustrating the diffraction efficiency. The horizontal axis represents the emission angle from the light emission surface 103. In this case, “0 °” on the horizontal axis represents the direction orthogonal to the light emitting surface 103 of the light guide plate 101, that is, the front direction of the light guide plate 101. In addition, the light guide plate 101 has a refractive index of 1.45, a light wavelength of 530 nm, a diffraction grating 104 having a rectangular cross section, and a period (pitch) of 500 nm. Further, “A” in the graph represents an average value of incident angles (propagation angle θ2) to the diffraction grating 104 in the range of 50 ° to 69 °, and “B” represents the incident angle (propagation to the diffraction grating 104). The angle θ2) represents an average value in the range of 70 ° to 90 °.
As shown in FIG. 4, in the case where the incident angle (propagation angle θ2) to the diffraction grating 104 is large (in the case of B), the diffraction efficiency is reduced to about 1/3 as compared with the case where the incident angle is small (in the case of A). It turns out that it falls.

FIG. 5 is a schematic view for illustrating a light guide plate and a light emitting device according to another comparative example.
As shown in FIG. 5, a light guide plate 101a and a light source 102 are provided in the light emitting device 100a. In this case, the refractive index of the light guide plate 101a is different from that illustrated in FIG. That is, this is a case where the refractive index of the light guide plate 101a is about 2 (for example, translucent ceramics or high refractive index resin).

  As described above, the propagation angle θ3 of light propagating through the light guide plate 101a is determined by the refractive index of the light guide plate 101a and the refractive index of the outside air (air). Therefore, in the case illustrated in FIG. 5 (when the refractive index is about 2), the propagation angle θ3 is about 60 ° to 90 °.

FIG. 6 is a graph for illustrating the relationship between the incident angle (propagation angle θ3) to the diffraction grating and the diffraction efficiency in the light guide plate illustrated in FIG. In this case, the refractive index of the light guide plate 101a is 2, the wavelength of light is 530 nm, the cross-sectional shape of the diffraction grating 104 is rectangular, and the period (pitch) is 500 nm.
As shown in FIG. 6, the diffraction efficiency decreases as the incident angle (propagation angle θ3) to the diffraction grating 104 increases. In addition, even in the range of 60 ° to 90 ° described above, the diffraction efficiency further decreases as the incident angle (propagation angle θ3) increases.

  That is, only light having a small propagation angle θ3 out of light propagating through the light guide plate 101a can be efficiently emitted. Therefore, it can be seen that the light utilization efficiency cannot be improved simply by changing the refractive index of the light guide plate.

Next, returning to FIG. 1, the light guide plate and the light emitting device according to this embodiment will be illustrated.
As shown in FIG. 1, the light emitting device 1 is provided with a light guide plate 11 and a light source 2.
The light guide plate 11 includes a substrate 12 that propagates light incident from the light source 2, and a conversion unit 13 that is provided on one main surface of the substrate 12 and converts the range of the propagation angle of light incident through the substrate 12. I have. Further, the light exit surface 3 is provided on the surface of the conversion unit 13 that faces the surface provided on the substrate 12, and the diffraction grating 4 is provided on the light exit surface 3. A light incident surface 5 is provided on one end surface of the substrate 12 in a direction substantially orthogonal to the light emitting surface 3. The light incident surface 5 is polished as necessary so that the incidence of light is not hindered. The light source 2 is provided so as to face the light incident surface 5.

  The substrate 12 is made of a transparent material so that light incident from the light source 2 can be propagated. The conversion unit 13 is also formed of a transparent material so that light incident through the substrate 12 can be transmitted.

  Here, the conversion unit 13 has a function of converting the propagation angle of light incident through the substrate 12 into a range that can be efficiently emitted to the outside. That is, it has a function of converting so that the propagation angle of light incident through the substrate 12 is reduced.

In the present embodiment, by making the refractive index of the conversion unit 13 higher than the refractive index of the substrate 12, the light propagating through the conversion unit 13 from the propagation angle θ <b> 1 of the light propagating through the substrate 12 is obtained. Conversion is performed so that the propagation angle θ1a becomes smaller. The conversion of the light propagation angle will be described later.
In this case, for example, the refractive index of the substrate 12 can be 1.45 or more and 1.55 or less, and the refractive index of the conversion unit 13 can be higher than this. As a material having a refractive index of 1.45 or more and 1.55 or less, for example, a transparent organic material such as acrylic resin (refractive index of about 1.49) or polycarbonate resin (refractive index of about 1.53), A transparent inorganic material such as glass (having a refractive index of about 1.45) can be exemplified.
Moreover, since the conversion part 13 is provided in order to convert the propagation angle of light, the thickness can also be made thin. For example, the thickness of the substrate 12 can be about 500 μm, and the thickness of the conversion unit 13 can be about 5 μm.
As the diffraction grating 4 provided on the light emitting surface 3, one having a rectangular cross-sectional shape as illustrated in FIG. 1 can be exemplified. However, the cross-sectional shape of the diffraction grating 4 is not limited to this, and can be appropriately changed.

  Moreover, it is preferable that the diffraction grating 4 emit light in a direction (front side) substantially orthogonal to the light emitting surface 3. Here, the emission angle θ4 of light into the air can be obtained by the following equation (1).

n2sinθ1a ± mλ / p = n1sinθ4 (1)

Here, λ is the wavelength, p is the period (pitch) of the diffraction grating, n2 is the refractive index of the converter 13, n1 is the refractive index of the outside air (air), and m is an integer.
Therefore, in order to emit light in a direction (front side) substantially orthogonal to the light emitting surface 3, the period p of the diffraction grating 4 may be determined so that θ4 becomes a value near zero. For example, when the wavelength is 530 nm and n2 = 1.45, the light is emitted in a direction (front side) substantially orthogonal to the light emitting surface 3 if the period (pitch) of the diffraction grating 4 is about 400 to 500 nm. Can do.

  Examples of the light source 2 include an LED (light emitting diode) and a CCFL (cold cathode ray tube). The light source 2 may emit white light, or may emit red, green, blue, or a mixed color thereof. However, the light emission method and light emission color of the light source 2 are not limited to those illustrated, and can be changed as appropriate. Moreover, only one light source 2 can be provided, or a plurality of light sources 2 can be provided.

  As shown in FIG. 1, the light emitted from the light source 2 enters the inside of the substrate 12 from the light incident surface 5. If light is emitted from the light source 2 in all directions and the light incident surface 5 is flat, the propagation angle θ1 of the light propagating through the substrate 12 is determined by the refractive index of the substrate 12 and the refraction of the outside air (air). Determined by the rate. That is, the propagation angle θ1 is determined according to Snell's law. For example, when the refractive index of the substrate 12 is about 1.45 (for example, glass), the propagation angle θ1 is about 46 ° to 90 °. In addition, the light may be incident on the inside of the substrate 12 by changing the light distribution angle with a lens or the like as necessary. In this case, the light propagating through the inside of the substrate 12 is totally reflected at the interface between the surface of the substrate 12 facing the side where the conversion unit 13 is provided and the outside air (air).

The light propagating through the substrate 12 is refracted at the interface between the substrate 12 and the conversion unit 13 according to Snell's law and is incident on the conversion unit 13. The propagation angle θ1a of light propagating inside the conversion unit 13 is determined by the refractive index of the substrate 12, the refractive index of the conversion unit 13, and the refractive index of the outside air (air). For example, when the refractive index of the substrate 12 is about 1.45 (for example, glass) and the refractive index of the conversion unit 13 is about 2 (for example, translucent ceramics or high refractive index resin). The propagation angle θ1a is about 31 ° to 47 °.
Then, the light propagating inside the conversion unit 13 enters the diffraction grating 4 at an angle θ1a at the interface between the conversion unit 13 and the outside air (air), and a part of the light is extracted into the air by the diffraction effect, and the rest Is reflected toward the inside of the conversion unit 13.

  Thus, the range of the propagation angle can be converted by causing the light propagating through the substrate 12 to enter the conversion unit 13. In this case, conversion can be performed so that the propagation angle becomes smaller by making the refractive index of the converter 13 higher than the refractive index of the substrate 12. The propagation angle θ <b> 1 of light propagating through the substrate 12 is also an incident angle when entering the conversion unit 13. In addition, the propagation angle θ1a of the light propagating through the conversion unit 13 is also an incident angle when entering the diffraction grating 4.

That is, if the substrate 12 and the conversion unit 13 are provided, it is possible to separate the propagation angle θ1 of the light propagating inside the substrate 12 and the incident angle θ1a to the diffraction grating 4, and the conversion unit 13 By changing the refractive index, it is possible to convert the incident angle θ1a to the diffraction grating 4 into a range in which the diffraction efficiency is high.
For example, in the case of the illustrated example, the propagation angle θ1 (about 46 ° to 90 °) can be converted into the propagation angle θ1a (about 31 ° to 47 °).

  Since the propagation angle θ1a in the converter 13 can be reduced, light can be efficiently emitted over the entire range of the propagation angle θ1a (incident angle on the diffraction grating 4). Therefore, the diffraction efficiency can be improved and the light utilization efficiency can be improved. This also means that the light emitting device 1 with high luminance can be obtained.

FIG. 7 is a graph for illustrating the diffraction efficiency. The horizontal axis represents the exit angle from the light exit surface 3. In this case, “0 °” on the horizontal axis represents the direction orthogonal to the light emitting surface 3, that is, the front direction of the light guide plate 11. Further, the refractive index of the substrate 12 is 1.45, the refractive index of the conversion unit 13 is 2, the wavelength of light is 530 nm, the sectional shape of the diffraction grating 4 is rectangular, and the period (pitch) is 500 nm.
For comparison with the comparative example shown in FIG. 4, “C” in the graph represents an average value of light having a propagation angle θ <b> 1 of light propagating through the substrate 12 in the range of 50 ° to 69 °. “D” represents the average value of the propagation angle θ1 in the range of 70 ° to 90 °. That is, as for the propagation angle of the light emitted from the light source, “C” in FIG. 7 and “A” in FIG. 4, and “D” in FIG. 7 and “B” in FIG. .

According to the present embodiment, the propagation angle θ1 can be converted into the propagation angle θ1a by the action of the conversion unit 13. That is, a large propagation angle θ1 can be converted into a small propagation angle θ1a.
Therefore, as shown in FIG. 7, the case where the propagation angle θ1 of the light propagating inside the substrate 12 is large (in the case of D) is the same regardless of whether it is small (in the case of D). Diffraction efficiency can be obtained. As a result, the light utilization efficiency can be improved over the entire range of the propagation angle θ1 of the light propagating through the substrate 12. This also means that the light emitting device 1 with high luminance can be obtained.

  FIG. 8 is a graph for illustrating the effect of the combination of the refractive index of the substrate and the refractive index of the conversion unit. FIG. 8A is a graph for illustrating the diffraction efficiency, and FIG. 8B is a graph for illustrating the relationship between the refractive index of the conversion unit and the diffraction efficiency in the front direction. Further, in the case illustrated in FIG. 8, the refractive index of the substrate 12 is set to 1.45, and the refractive index of the conversion unit 13 is changed. “X” in FIG. 8A is the case of the light guide plate 101 according to the comparative example illustrated in FIG. 2, and the refractive index of the light guide plate 101 is 1.45. In addition, the dotted line in Fig.8 (a) represents the value (about 6%) of the diffraction efficiency of the light-guide plate 101 which concerns on a comparative example.

  As shown in FIG. 8A, if the conversion unit 13 is provided, the diffraction efficiency can be improved as compared with the light guide plate 101 (x mark) according to the comparative example. Further, the diffraction efficiency can be improved as the refractive index of the converter 13 is increased.

  Further, as shown in FIG. 8B, in order to improve the diffraction efficiency in the front direction, the refractive index of the conversion unit 13 is preferably set to 1.9 or more and 3 or less. In this case, considering the degree of freedom of material selection, it is preferable that the refractive index at which the material selection is relatively easy is 1.9 or more and 2.5 or less.

  FIG. 9 is a graph for illustrating the effect of the combination of the refractive index of the substrate and the refractive index of the conversion unit. FIG. 9A is a graph for illustrating the diffraction efficiency, and FIG. 9B is a graph for illustrating the relationship between the refractive index of the conversion unit and the diffraction efficiency in the front direction.

  Further, in the case illustrated in FIG. 9, the refractive index of the substrate 12 is set to 1.5, and the refractive index of the conversion unit 13 is changed. “X” in FIG. 9A is the case of the light guide plate 101 according to the comparative example illustrated in FIG. 2, and the refractive index of the light guide plate 101 is 1.5. In addition, the dotted line in Fig.9 (a) represents the value (about 6%) of the diffraction efficiency of the light-guide plate 101 which concerns on a comparative example. That is, what is illustrated in FIG. 9 is an example in which the refractive index 1.45 of the substrate 12 in FIG. 8 is changed to 1.5.

  As shown in FIG. 9A, if the conversion unit 13 is provided, the diffraction efficiency can be improved as compared with the light guide plate 101 (x mark) according to the comparative example. Further, the diffraction efficiency can be improved as the refractive index of the converter 13 is increased.

Further, as shown in FIG. 9B, in order to improve the diffraction efficiency in the front direction, the refractive index of the conversion unit 13 is preferably set to 1.9 or more and 3 or less. In this case, considering the degree of freedom of material selection, it is preferable that the refractive index at which the material selection is relatively easy is 1.9 or more and 2.5 or less.
Further, from FIGS. 8 and 9, even if the refractive index of the substrate 12 is changed by a width of about 1.45 to 1.5, there is no significant difference in the combination relationship with the refractive index of the conversion unit 13. Recognize. For example, when an acrylic resin (refractive index of about 1.5) or glass (refractive index of about 1.45) is selected as the material of the substrate 12, the refractive index of the conversion unit 13 is 1.9 or more, 3 What is necessary is just to select the transparent material which becomes the following. In this case, if the refractive index of the conversion unit 13 is 1.9 or more and 2.5 or less, material selection can be made relatively easy. For example, examples of the material of the conversion unit 13 include translucent ceramics (having a refractive index of about 2) and a high refractive index resin.

  Also, from FIGS. 8B and 9B, if the refractive index of the conversion unit 13 is 1.9 or more and 3 or less, or 1.9 or more and 2.5 or less, the guide according to the comparative example is obtained. It can be seen that the diffraction efficiency in the front direction can be improved by about 4 to 5.5 times compared to the value of the optical plate 101 (the value of the dotted line in the figure).

  As described above, according to the present embodiment, since the conversion unit 13 is provided on one main surface of the substrate 12, the propagation angle θ <b> 1 of the light propagating inside the substrate 12 and the diffraction grating 4. Can be separated from the incident angle θ1a. Then, by changing the refractive index of the conversion unit 13, the incident angle θ1a to the diffraction grating 4 can be converted into a range in which diffraction efficiency is high. Therefore, diffraction efficiency can be improved and light utilization efficiency can be improved. This also means that the light emitting device 1 with high luminance can be obtained.

Next, the liquid crystal display device according to this embodiment is illustrated.
FIG. 10 is a schematic diagram for illustrating the liquid crystal display device according to this embodiment. As shown in FIG. 10, the liquid crystal display device 50 is provided with the light emitting device 1 (light guide plate 11) and the liquid crystal display panel 53 according to the present embodiment. The light emitting device 1 (light guide plate 11) is provided inside a box-shaped housing 54. In addition, the liquid crystal display panel 53 is provided so as to face the light emitting surface 3 of the light guide plate 11 included in the light emitting device 1, and can receive light emitted from the light emitting device 1 (light guide plate 11). . In addition, a light reflecting sheet, a prism, a diffraction grating, and the like (not shown) can be provided on the surface of the light guide plate 11 on the side facing the light emitting surface 3 as necessary.
Note that components other than the light-emitting device 1 (light guide plate 11) according to the present embodiment can be applied with known techniques, and thus description thereof is omitted.
According to the liquid crystal display device according to the present embodiment, high luminance display characteristics can be obtained. Next, the method for manufacturing the light guide plate according to the present embodiment will be illustrated.
FIG. 11 is a schematic process diagram for illustrating the method of manufacturing the light guide plate according to the first embodiment.
In the present embodiment, the substrate 12 is provided in the conversion unit 13 after the conversion unit 13 having the diffraction grating 4 is formed. That is, the diffraction grating 4 is formed on one main surface of the conversion unit 13 using the mold 60 on which the uneven part (uneven shape pattern 60a) for transferring the shape of the diffraction grating 4 is formed. A substrate 12 having a refractive index lower than the refractive index of the converter 13 is provided on the surface facing the surface on which the diffraction grating 4 is formed.

  First, as shown in FIG. 11A, a mold 60 is created using an electron beam lithography method or machining. An uneven pattern 60 a is formed on the main surface of the mold 60 so that the shape of the diffraction grating 4 provided in the conversion unit 13 can be transferred.

  Next, as shown in FIG. 11B, the pattern 60 a is transferred to a resin material having a high refractive index using a mold 60. For the transfer, an imprint method, an injection molding method, or the like can be used. The transferred pattern 60 a becomes the conversion unit 13, and the transferred pattern 60 a becomes the diffraction grating 4.

  Next, as shown in FIG. 11C, the light guide plate 11 is formed by providing the substrate 12 on the surface opposite to the surface on which the diffraction grating 4 of the conversion unit 13 is provided. An adhesive method or the like can be used to form the light guide plate 11 (joining between the conversion unit 13 and the substrate 12).

Next, as shown in FIG. 11D, the light guide plate 11 is released from the mold 60.
Next, as shown in FIG. 11E, the reflection sheet 14 may be provided on the surface of the substrate 12 that faces the surface on which the conversion unit 13 is provided. Moreover, a prism, a diffraction grating, etc. can also be patterned as needed in the surface facing the surface in which the reflection sheet 14 and the conversion part 13 of the board | substrate 12 were provided.

FIG. 12 is a schematic process diagram for illustrating the light guide plate manufacturing method according to the second embodiment.
In the present embodiment, the diffraction grating 4 is provided in the conversion unit 13 after the conversion unit 13 and the substrate 12 are joined. That is, the gold on which the concavo-convex portion (concave / convex pattern 60a) for transferring the shape of the diffraction grating 4 is formed by bonding the conversion portion 13 and the substrate 12 having a refractive index lower than the refractive index of the conversion portion 13. The diffraction grating 4 is formed on the main surface of the conversion unit 13 using the mold 60.

First, in the same manner as illustrated in FIG. 11A, a mold 60 is created using an electron beam lithography method or machining.
On the other hand, as shown in FIG. 12A, the plate-like material 12 a that becomes the substrate 12 and the plate-like material 13 a that becomes the conversion unit 13 are joined. An adhesive method or the like can be used for the joining.

  Next, as shown in FIG. 12B, the pattern 60 a is transferred to the plate-like material 13 a using a mold 60. An imprint method or the like can be used for the transfer. The transferred pattern 60 a becomes the conversion unit 13, and the transferred pattern 60 a becomes the diffraction grating 4. Further, the plate-like material 12 a becomes the substrate 12. The light guide plate 11 is formed by the substrate 12 and the conversion unit 13.

Next, as shown in FIG. 12C, the light guide plate 11 is released from the mold 60.
Next, as shown in FIG. 12 (d), the reflection sheet 14 may be provided on the surface of the substrate 12 that faces the surface on which the conversion unit 13 is provided. Moreover, a prism, a diffraction grating, etc. can also be patterned as needed in the surface facing the surface in which the reflection sheet 14 and the conversion part 13 of the board | substrate 12 were provided.

Heretofore, the present embodiment has been illustrated. However, the present invention is not limited to these descriptions.
As long as the features of the present invention are provided, those skilled in the art appropriately modified the design of the above-described embodiments are also included in the scope of the present invention.
For example, the shape, size, material, arrangement, and the like of each element included in the light emitting device 1, the light guide plate 11, the liquid crystal display device 50, and the like are not limited to those illustrated, and can be changed as appropriate.

  Moreover, each element with which each embodiment mentioned above is combined can be combined as much as possible, and what combined these is also included in the scope of the present invention as long as the characteristics of the present invention are included.

It is a schematic diagram for illustrating the light-guide plate and light-emitting device which concern on this Embodiment. It is a schematic diagram for illustrating the light-guide plate and light-emitting device which concern on a comparative example. It is a graph for demonstrating the relationship between the incident angle (propagation angle) to a diffraction grating, and diffraction efficiency. It is a graph for demonstrating diffraction efficiency. It is a schematic diagram for illustrating the light-guide plate and light-emitting device which concern on another comparative example. FIG. 6 is a graph for illustrating the relationship between the incident angle (propagation angle) to the diffraction grating and the diffraction efficiency in the light guide plate illustrated in FIG. 5. It is a graph for demonstrating diffraction efficiency. It is a graph for demonstrating the effect by the combination of the refractive index of a board | substrate, and the refractive index of a conversion part. It is a graph for demonstrating the effect by the combination of the refractive index of a board | substrate, and the refractive index of a conversion part. It is a schematic diagram for demonstrating about the liquid crystal display device which concerns on this Embodiment. It is a schematic process diagram for illustrating about the manufacturing method of the light guide plate concerning a 1st embodiment. It is a schematic process diagram for illustrating about the manufacturing method of the light-guide plate which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Light-emitting device, 2 Light source, 3 Light emission surface, 4 Diffraction grating, 5 Light incident surface, 11 Light guide plate, 12 Substrate, 13 Conversion part, 50 Liquid crystal display device, 53 Liquid crystal display panel, (theta) 1 propagation angle, (theta) 1a propagation angle, θ4 Output angle

Claims (9)

A substrate that propagates light incident from a light source;
A conversion unit provided adjacent to one main surface of the substrate and having a diffraction grating on a surface facing the surface adjacent to the main surface of the substrate;
With
The light guide plate characterized in that a refractive index of the conversion unit is higher than a refractive index of the substrate.   The light guide plate according to claim 1, wherein a propagation angle of light propagating through the conversion unit is smaller than a propagation angle of light incident from the light source and propagating through the substrate.   The light guide plate according to claim 1, wherein the conversion unit has a refractive index of 1.9 or more and 3 or less.   The light guide plate according to claim 1, wherein a refractive index of the substrate is 1.45 or more and 1.55 or less. The light guide plate according to any one of claims 1 to 4,
A light source provided facing the light incident surface of the light guide plate;
A light-emitting device comprising:   The light emitting device according to claim 5, wherein a light emitting surface is provided in a direction substantially orthogonal to the light incident surface of the light guide plate. A light emitting device according to claim 5 or 6,
A liquid crystal display panel provided facing the light exit surface of the light guide plate of the light emitting device;
A liquid crystal display device comprising: Using the mold on which the concavo-convex part for transferring the shape of the diffraction grating is formed, the diffraction grating is formed on one main surface of the conversion part,
Providing a substrate having a refractive index lower than the refractive index of the conversion unit on the surface of the conversion unit facing the surface on which the diffraction grating is formed;
A method of manufacturing a light guide plate characterized by the above. Bonding the conversion part and a substrate having a refractive index lower than the refractive index of the conversion part;
Forming a diffraction grating on the main surface of the conversion unit using a mold in which an uneven part for transferring the shape of the diffraction grating is formed;
A method of manufacturing a light guide plate characterized by the above.

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