JP2009175239A - Optical element and light source unit - Google Patents

Abstract

Provided are an optical element and a light source unit that have good color reproducibility and can prevent occurrence of color unevenness.
SOLUTION: Columnar protrusions 4 are arranged on a substrate 2 in a square lattice pattern in a first direction (X-axis direction) and a second direction (Y-axis direction) intersecting each other. The columnar protrusions 4 are arranged in the first direction at an interval d1 corresponding to the wavelength of the first light Lr incident from the direction, and the columnar protrusions 4 are arranged at the interval d2 corresponding to the wavelength of the second light Lg incident from the second direction. The distance d3 between the rows L3 of the columnar protrusions 4 arranged in the second direction and arranged in the third direction intersecting both the first direction and the second direction is incident from the direction orthogonal to the third direction. It corresponds to the wavelength of the third light Lb.
[Selection] Figure 2

Description

  The present invention relates to an optical element and a light source unit.

  A photonic crystal is a structure whose refractive index changes periodically in the wavelength region of light. Providing this photonic crystal on the light exit surface of a light emitter such as a light emitting diode has been proposed to improve the efficiency of extracting light generated by the light emitter (for example, Patent Document 1). reference). Here, the photonic crystal is composed of a plurality of columnar columnar protrusions arranged in a lattice pattern on the exit surface, and the columnar protrusions and the air layer, which are two substances having different refractive indexes, are spaced apart from each other by a predetermined distance. The structure is regularly arranged. Therefore, the light emitted from the exit surface at a normal angle larger than the critical refraction angle with respect to the exit surface is diffracted by the periodically formed columnar protrusions and the air layer, and the exit direction is set to be larger than the critical refraction angle. It can be made smaller. Thereby, the ratio of the light incident on the photonic crystal that is totally reflected on the exit surface is reduced, and the light extraction efficiency is improved.

By the way, a liquid crystal display device is used for a display unit of an electronic device such as a mobile phone.
This liquid crystal display device is usually provided with a backlight unit for improving display visibility. The backlight unit includes a light guide plate that guides illumination light from a light source and emits the light toward a liquid crystal panel.
Therefore, in such a light guide plate, in order to improve the extraction efficiency of illumination light, it is conceivable to provide the above-described photonic crystal on the exit surface.
In particular, in the case of medium / small-sized backlights, in order to reduce the thickness of the light guide plate, a so-called edge method in which light is incident from a side end surface perpendicular to the light exit surface of the light guide plate is mainly employed.
JP 2006-49855 A

  However, the following problems remain in the conventional optical element. An LED is mainly used as a light source for causing light to enter an optical element. However, when a white LED is used, the white light does not include the wavelengths of light of RGB colors in a well-balanced manner, so that the color reproducibility is deteriorated. There is. In addition, when the RGB LEDs are used as light sources in order to improve color reproducibility in the edge method described above, there is a problem in that light of each color emitted from the emission surface is biased and color unevenness occurs. .

  Accordingly, the present invention provides an optical element and a light source unit that have good color reproducibility and can prevent the occurrence of color unevenness.

  In order to solve the above-described problems, an optical element of the present invention is an optical element that includes a substrate and a plurality of columnar protrusions provided on one surface of the substrate, and conducts light therein. The protrusions are arranged in a grid pattern in a first direction and a second direction intersecting each other, and are arranged at intervals corresponding to the wavelength of the first light incident from the first direction in the first direction. In the second direction, the third direction is arranged at an interval corresponding to the wavelength of the second light incident from the second direction and intersects both the first direction and the second direction. The columns of the columnar protrusions arranged in the direction are arranged at intervals corresponding to the wavelength of the third light incident from a direction orthogonal to the third direction.

  With this configuration, each light incident on the substrate from each direction can be emitted from one surface of the substrate at substantially the same angle, and each light can be efficiently synthesized. Therefore, each light can be uniformly emitted from one surface of the substrate, and the balance of wavelengths contained in the synthesized light emitted from the substrate can be improved. Accordingly, it is possible to provide an optical element that has good color reproducibility and prevents the occurrence of color unevenness.

  In the optical element of the present invention, the distance between the columnar protrusions in the first direction is d1, the distance between the columnar protrusions in the second direction is d2, and the distance between the columnar protrusions in the third direction. D3, the wavelength of the first light is λ1, the wavelength of the second light is λ2, the wavelength of the third light is λ3, and is incident on one surface of the substrate. The angle is α1, the incident angle of the second light is α2, the incident angle of the third light is α3, and the emission angle of the first light emitted from one surface of the substrate is β1, the second light When the light emission angle is β2, the third light emission angle is β3, the refractive index of the substrate is n, the refractive index of air is a, and N1, N2, and N3 are integers, the distance d1 , D2, and d3 satisfy the relationships of the following equations (1), (2), and (3), respectively, and correspond to the wavelengths λ1, λ2, and λ3. Outgoing angle .beta.1, .beta.2, characterized in that it is adjusted to the β3 a predetermined value.

d1 · (n · sin α1−a · sin β1) = N1 · λ1 (1)
d2 · (n · sin α2−a · sin β2) = N2 · λ2 (2)
d3 · (n · sin α3-a · sin β3) = N3 · λ3 (3)

  With this configuration, light of each wavelength can be emitted from one surface of the substrate in a predetermined direction and synthesized. Thereby, the prism sheet conventionally used for emitting light in the front direction becomes unnecessary. Therefore, the number of members of the optical element can be reduced as compared with the conventional art, and the optical element can be reduced in thickness, the material cost can be reduced, and the environmental load can be reduced.

  The optical element of the present invention is characterized in that the distances d1, d2, and d3 are adjusted so that each of the emission angles β1, β2, and β3 approaches 0 °.

  By comprising in this way, the light of each wavelength can be radiate | emitted perpendicularly | vertically from one surface of a light-guide plate, and each light can be synthesize | combined uniformly.

  In the optical element of the present invention, the first direction is orthogonal to the second direction, and the third direction is parallel to a diagonal line of a unit cell in which the four columnar protrusions are arranged in a rectangle. It is characterized by.

  With this configuration, the columnar protrusions are arranged in a vertical grid pattern. And when satisfy | filling the relationship of said Formula (1)-Formula (3), each light source which inject | emits the light of each wavelength (lambda) 1, (lambda) 2, (lambda) 3 should be selected so that the following formula (4) may be satisfy | filled. Thus, the intervals d1, d2, and d3 corresponding to the wavelengths λ1, λ2, and λ3 can be easily selected.

λ3 = λ1 · λ2 / √ (λ1 ² + λ2 ² ) (4)

  Further, the optical element of the present invention is characterized in that a plurality of columnar protrusion units having a plurality of the unit lattices are arranged on one surface of the substrate, and the arrangement density of the columnar protrusion units varies depending on the position in the one surface of the substrate. To do.

  By configuring in this way, even if the brightness varies depending on the position in one surface of the substrate, the amount of light emitted in a desired direction is adjusted by increasing or decreasing the density of the columnar protrusion units, and The brightness can be made uniform.

  In the optical element of the present invention, the columnar protrusion has a parabolic shape in a cross-sectional shape perpendicular to one surface of the substrate.

  With such a configuration, the refractive index is gradually and relatively uniformly changed from the base end side to the tip end side of the columnar protrusion, so that the diffraction efficiency is improved.

  Moreover, the optical element of the present invention is characterized in that the columnar protrusion has an elliptical cross-sectional shape parallel to one surface of the substrate.

  With this configuration, the diffraction efficiency of the columnar protrusion can be made different for each light incident on the substrate from each direction.

  In the optical element of the present invention, a light diffusion layer is provided on the columnar protrusion side of the substrate.

  With this configuration, even when the incident angle of each light fluctuates and the emission angle is no longer perpendicular to the one surface of the substrate, the light is diffused in a direction perpendicular to the one surface of the substrate. The emitted light can be increased.

  In the optical element of the present invention, the first light is red light, the second light is green light, and the third light is blue light.

  With this configuration, it is possible to combine the light of each color and obtain white light with high color reproducibility that includes a balanced wavelength of the light of each color of RGB.

  The light source unit of the present invention includes any one of the light source elements described above, a first light source that makes the first light incident on the substrate from the first direction, and the second light on the substrate. And a third light source for causing the third light to enter the substrate from a direction perpendicular to the third direction.

  With this configuration, each light emitted from each light source enters the optical element, is emitted from one surface of the substrate, and is uniformly synthesized. Therefore, it is possible to provide a light source unit that has good color reproducibility and prevents occurrence of color unevenness.

<First embodiment>
Next, a first embodiment of the present invention will be described based on the drawings. In each drawing used in the following description, the scale is appropriately changed to make each member a recognizable size.

(Backlight unit, light guide plate)
1A and 1B show an overall configuration of a backlight unit according to the present embodiment. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line AA ′ in FIG. 2 is an enlarged view of a part of the light guide plate of the backlight unit of FIG. 1, wherein (a) is a plan view and (b) is a cross-sectional view.

  The optical unit of the present embodiment shown in FIGS. 1A and 1B is, for example, a backlight unit (optical unit) 100 of a liquid crystal display device, and a light guide plate (optical element) that conducts light therein. ) 1 and a plurality of light sources R, G, B for irradiating the light guide plate 1 with light. The light guide plate 1 includes a substrate 2 and a plurality of columnar protrusions 4 formed in the diffraction region 3 on the surface (one surface) 2a of the substrate 2. These columnar protrusions 4 are formed so as to protrude substantially vertically from the surface 2 a of the substrate 2. The substrate 2 is formed of a material having translucency in the wavelength region used for the light sources R, G, and B, such as polycarbonate (PC). Further, the light sources R, G, and B are configured by LEDs, for example.

As shown in FIG. 1A, the light guide plate 1 of the present embodiment is substantially rectangular in plan view, and has a pentagonal shape with one corner chamfered. The side surface 2b of the chamfered portion is formed in parallel with a column L3 (see FIG. 2A) of columnar protrusions 4 to be described later.
Here, as shown in FIG. 1A, when an XYZ orthogonal coordinate system having an XY plane parallel to the surface 2a of the substrate 2 is set, red light (first light is applied to the side surface 2y parallel to the Y axis of the substrate 2). The red light source R for irradiating the light Lr in the X-axis direction in plan view is disposed. A green light source G that irradiates green light (second light) Lg in the Y-axis direction in plan view is disposed on a side surface 2x parallel to the X-axis of the substrate 2. A blue light source B that irradiates blue light (third light) Lb in a direction perpendicular to the column L3 of columnar protrusions 4 to be described later is disposed on the side surface 2b of the chamfered portion of the substrate 2.

  That is, the side surface 2y parallel to the Y axis of the substrate 2 is an incident surface on which the red light Lr is incident, and the side surface 2x parallel to the X axis of the light guide plate 1 is an incident surface on which the green light Lg is incident. . Further, the side surface 2b of the chamfered portion described above is an incident surface on which the blue light Lb is incident. And the diffraction area | region 3 in which the columnar protrusion 4 of the surface 2a of the board | substrate 2 was formed becomes the emission surface of light Lr, Lg, Lb of each color.

Further, on the surface 2a of the substrate 2, as shown in FIG. 2A, a plurality of columnar protrusions 4 are arranged in the X-axis direction (first direction) and the Y-axis direction (second direction) orthogonal to each other. They are arranged in a square lattice at equal intervals d1 and d2. That is, the columnar protrusions 4 are arranged in a vertical grid pattern. In other words, the columnar protrusions 4 are arranged such that the columns L1 of the columnar protrusions 4 arranged in the Y-axis direction are arranged in the X-axis direction at a constant interval d1, and the columns L2 of the columnar protrusions 4 arranged in the X-axis direction are also arranged. They are arranged in the Y-axis direction at a constant interval d2.
Further, the columnar protrusions 4 arranged in the direction intersecting both the X-axis direction and the Y-axis direction, for example, the diagonal direction (third direction) of the unit cell U including the four columnar protrusions 4 arranged in a rectangular shape. The row L3 is also arranged at a constant interval d3.

  In this embodiment, the distance d1 between the columnar protrusions 4 in the X-axis direction, the distance d2 between the columnar protrusions 4 in the Y-axis direction, and the distance d3 between the rows L3 of the columnar protrusions 4 are expressed by the following equations (1), The relationship of Formula (2) and Formula (3) is satisfied. Here, the intervals d1 and d2 are respectively the center intervals of the columnar protrusions 4, and the interval d3 is the interval between the center lines of the row L3.

d1 · (n · sin α1−a · sin β1) = N1 · λ1 (1)
d2 · (n · sin α2−a · sin β2) = N2 · λ2 (2)
d3 · (n · sin α3-a · sin β3) = N3 · λ3 (3)

Here, λ1 is the wavelength of the red light Lr, λ2 is the wavelength of the green light Lg, and λ3 is the wavelength of the blue light Lb. Further, as shown in FIG. 2B, α1 is an incident angle of the red light Lr incident on the surface 2a of the substrate 2, α2 is an incident angle of the green light Lg incident on the surface 2a of the substrate 2, and α3 is the substrate 2 This is the incident angle of the blue light Lb incident on the surface 2a. Β1 is an emission angle of the red light Lr emitted from the surface 2a of the substrate 2, β2 is an emission angle of the green light Lg emitted from the surface 2a of the substrate 2, and β3 is an emission angle of the blue light Lb emitted from the surface 2a of the substrate 2. The exit angle. Further, n is the refractive index of the substrate 2, a is the refractive index of air, and N1, N2, and N3 are integers.
The intervals d1, d2, and d3 are adjusted so that the emission angles β1, β2, and β3 approach 0 ° corresponding to the wavelengths λ1, λ2, and λ3, respectively.

  In the present embodiment, the wavelengths λ1, λ2, and λ3 of the light beams Lr, Lg, and Lb of each color are selected so as to substantially satisfy the following formula (4).

λ3 = λ1 · λ2 / √ (λ1 ² + λ2 ² ) (4)

  For example, the following combinations (5) to (7) can be given as examples of combinations of wavelengths λ1, λ2, and λ3 that substantially satisfy Expression (4).

(Λ1, λ2, λ3) = (400 nm, 520 nm, 620 nm) (5)
(Λ1, λ2, λ3) = (410 nm, 530 nm, 650 nm) (6)
(Λ1, λ2, λ3) = (420 nm, 550 nm, 650 nm) (7)

In the present embodiment, for example, the above combination (7) is adopted.
Further, since the refractive index a of air is 1.0 and the light guide plate 1 is made of polycarbonate, the refractive index n of the substrate 2 in the above wavelength region is about 1.59.
In addition, each of the light sources R, G, and B described above has light Lr, Lg, and Lb of each color emitted from the light sources R, G, and B with respect to the surface 2a of the substrate 2 as shown in FIG. The angle with respect to the Z axis is adjusted so as to be incident at an incident angle α1, α2, α3 of about 50 °, and the substrate 2 is installed on each side surface 2y, 2x, 2b.

  The distance d1 between the centers of the columnar protrusions 4 in the X-axis direction is N1 = 1 in the above formula (1), and the wavelength λ1 of the red light Lr so that the emission angle β1 of the red light Lr is approximately 0 °. Is set to about 337 nm. That is, the interval d1 between the columnar protrusions 4 in the X-axis direction is about 0.82 times the wavelength λ1.

  Further, the distance d2 between the centers of the columnar protrusions 4 in the Y-axis direction is N2 = 1 in the above formula (2), and the wavelength λ2 of the green light Lg so that the emission angle β2 of the green light Lg is approximately 0 °. Is set to about 520 nm. That is, the interval d2 between the columnar protrusions 4 in the Y-axis direction is about 0.82 times the wavelength λ2 of the green light Lg.

  Further, the distance d3 between the centers of the columns L3 of the columnar protrusions 4 arranged in the diagonal direction of the unit cell U is N3 = 1 in the above equation (3), and the emission angle β3 of the blue light Lb is approximately 0 °. Thus, the wavelength is set to about 533 nm corresponding to the wavelength λ3 of the blue light Lb. That is, the distance d3 between the rows L3 of the columnar protrusions 4 arranged in the diagonal direction of the unit cell U is about 0.82 times the wavelength λ3 of the blue light Lb.

  Here, the distance d1 between the columnar protrusions 4 in the X-axis direction, the distance d2 between the columnar protrusions 4 in the Y-axis direction, and the distance d3 between the columns L3 of the columnar protrusions 4 are the wavelengths λ1 of the light beams Lr, Lg, and Lb of the respective colors. , Λ2 and λ3 are desirably about 0.5 times or more and about 10 times or less. If it is this range, the characteristic of the light-guide plate 1 will not deteriorate beyond the allowable range.

  Thus, the columnar protrusions 4 are arranged in the X-axis direction at an interval d1 corresponding to the wavelength λ1 of the red light Lr incident on the light guide plate 1 from the X-axis direction. The columnar protrusions 4 are arranged in the Y-axis direction at an interval d2 corresponding to the wavelength λ2 of the green light Lg incident on the light guide plate 1 from the Y-axis direction. In addition, the wavelength d of the blue light Lb incident from the direction orthogonal to the diagonal direction in which the distance d3 between the columns L3 of the columnar protrusions 4 arranged in the diagonal direction of the unit cell U that intersects both the X-axis direction and the Y-axis direction. This corresponds to λ3.

Next, the operation of this embodiment will be described.
As shown in FIG. 1A, the red light Lr is irradiated from the red light source R, and is incident on the side surface 2y parallel to the Y axis of the substrate 2 from the X axis direction in plan view. At the same time, green light Lg is emitted from the green light source G and is incident on the side surface 2x parallel to the X axis of the substrate 2 from the Y axis direction in plan view. At the same time, blue light Lb is emitted from the blue light source B and is incident on the chamfered side surface 2b of the substrate 2 of the light guide plate 1 from a direction perpendicular to the column L3 of the columnar protrusions 4 in plan view. At this time, since the irradiation angles of the light beams Lr, Lg, and Lb with respect to the Z-axis of the light sources R, G, and B are adjusted as described above, the light beams Lr, Lr, of each color irradiated from the light sources R, G, and B are adjusted. As shown in FIG. 2B, Lg and Lb are incident on the surface 2a of the substrate 2 mainly at incident angles α1, α2, and α3 of about 50 °, respectively.

  Here, as described above, the distances d1 and d2 between the columnar protrusions 4 and the distance d3 between the columns L3 of the columnar protrusions 4 shown in FIG. 2A are respectively the above expressions (1), (2), and ( 2 are satisfied so that the emission angles β1, β2, and β3 shown in FIG. 2 are approximately 0 ° corresponding to the wavelengths λ1, λ2, and λ3 of the light beams Lr, Lg, and Lb of the respective colors. Has been. Therefore, each color light Lr, Lg, Lb incident on the surface 2 a of the substrate 2 is diffracted in a direction substantially perpendicular to the surface 2 a of the substrate 2 and emitted from the substrate 2. As a result, the light beams Lr, Lg, and Lb that are incident on the side surfaces 2x, 2y, and 2b of the light guide plate 1 from different directions in a plan view from the surface 2a of the substrate 2 in a substantially vertical direction (Z-axis direction). It can be synthesized by injection.

  This eliminates the need for a prism sheet conventionally used for emitting light in the front direction perpendicular to the surface 2a of the substrate 2. Therefore, it is possible to reduce the number of members of the light guide plate 1 and the backlight unit 100 as compared with the conventional case, and not only can the light guide plate 1 and the backlight unit 100 be made thinner, but also the material cost and the environmental load are reduced. can do.

  Further, the red light source R, the green light source G, and the blue light source B are used as the light sources, and the red light Lr, the green light Lg, and the blue light Lb are used as the illumination light, so that the surface 2a of the substrate 2 is substantially perpendicular (Z-axis direction). ) Can be irradiated with white combined light with high color reproducibility including the wavelengths λ1, λ2, and λ3 of RGB light Lr, Lg, and Lb in a well-balanced manner.

  Further, the columnar protrusions 4 are arranged in a lattice pattern perpendicular to the X-axis direction and the Y-axis direction, and the diagonal direction of the unit cell U is a third direction that intersects both the X-axis and the Y-axis. Accordingly, the wavelengths λ1, λ2, and λ3 of the light beams Lr, Lg, and Lb of each color can be selected so as to satisfy the above formula (4), and the relationships of the above formulas (1) to (3) are satisfied. The distances d1 and d2 between the columnar protrusions 4 and the distance d3 between the columns L3 of the columnar protrusions 4 can be easily determined.

  As described above, according to the light guide plate 1 of the present embodiment, the lights Lr, Lg, and Lb incident on the side surfaces 2x, 2y, and 2b of the substrate 2 from the respective directions are substantially perpendicular to the surface 2a of the substrate 2. The light Lr, Lg, and Lb of each color can be efficiently synthesized by emitting in the direction. Therefore, light Lr, Lg, and Lb of each color can be uniformly emitted from the surface 2a of the substrate 2 and the balance of the wavelengths λ1, λ2, and λ3 included in the combined light emitted from the substrate 2 can be improved. Therefore, it is possible to provide the light guide plate 1 that has good color reproducibility and prevents the occurrence of color unevenness.

  Further, according to the backlight unit 100 of the present embodiment, the light beams Lr, Lg, and Lb emitted from the light sources R, G, and B are incident on the light guide plate 1 and emitted from the surface 2 a of the substrate 2. And evenly synthesized. Therefore, it is possible to provide the backlight unit 100 that has good color reproducibility and prevents the occurrence of color unevenness.

  In the present embodiment, as described above, the intervals d1 and d2 of the columnar protrusions 4 and the interval d3 of the columnar protrusions in the diagonal line L3 are set so that the emission angles β1, β2, and β3 approach 0 °, respectively. However, the emission angles β1, β2, and β3 may be adjusted to be equal to 0 °. Thereby, the light Lr, Lg, Lb of each color can be emitted from the surface 2a of the light guide plate 1 more perpendicularly, and the light Lr, Lg, Lb of each color can be uniformly synthesized.

  Further, in this embodiment, as shown in FIGS. 2A and 2B, the columnar protrusion 4 having a columnar shape is used, but instead of the columnar protrusion 4 having a columnar shape, FIG. ) And a columnar protrusion 4b having a parabolic contour shape in a cross-sectional view parallel to the Z-axis, as shown in FIG. Accordingly, since the refractive index of the light guide plate 1 gradually and relatively uniformly changes from the base end side to the front end side of the columnar protrusion 4b, the diffraction efficiency of the light guide plate 1 can be improved.

  Further, as shown in FIG. 3 (a) and FIG. 3 (b), by using columnar protrusions 4b having an elliptical cross-sectional shape parallel to the surface 2a of the substrate 2, each incident on the substrate 2 from each direction. The diffraction efficiencies of the columnar protrusions 4b with respect to light can be varied, and the diffraction efficiencies in the respective directions of the light guide plate 1 can be adjusted.

(Manufacturing method of light guide plate)
Next, an example of a method for manufacturing the light guide plate 1 of the present embodiment will be described.
First, a mold substrate (not shown) formed of silicon or the like is prepared in order to form the mold of the columnar protrusions 4 described above, and a photolithography method, an etching method, or the like is applied to one surface of the mold substrate by FIG. A plurality of cylindrical recesses corresponding to the columnar protrusions 4 shown in FIG. In this case, when the columnar protrusion 4b having a parabolic shape as shown in FIGS. 3A and 3B forms a parabolic projection 4b, the shape of the columnar protrusion 4b is appropriately determined using a gray mask. A recess having a shape corresponding to is formed.
Next, the concave portions on the mold substrate are filled with an ultraviolet curable resin. As the ultraviolet curable resin, for example, a resin that cures mainly at a wavelength of 365 nm is used.

Next, the substrate 2 of the light guide plate 1 is disposed on the mold substrate, and the positional relationship between the side surfaces 2x, 2y, 2b of the substrate 2 and the recesses of the mold substrate is determined according to the side surfaces 2x, 2y, 2b of the substrate 2 described above. The substrate 2 and the mold substrate are aligned so as to satisfy the positional relationship between the columnar protrusions 4 and 4b.
Next, the ultraviolet curable resin filled in the concave portions of the mold substrate through the substrate 2 is irradiated with ultraviolet rays to be cured, and the ultraviolet curable resin and the substrate 2 are integrated. At this time, a silane coupling agent may be applied to the surface of the substrate 2 on the mold substrate side in order to improve the adhesion between the ultraviolet curable resin and the substrate 2.

And the light-guide plate 1 provided with the above-mentioned columnar protrusion 4 and 4b is manufactured by peeling the board | substrate 2 from a type | mold board | substrate.
At this time, in order to improve the releasability between the mold substrate and the ultraviolet curable resin, a fluorine-based molecular film may be formed on the surface of the mold substrate including the inside of the recess by using a fluorine-based solvent. In this case, the thickness of the molecular film is preferably about the size of the solvent molecule.

<Second embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. 4A and 4B with reference to FIGS. The present embodiment is different from the first embodiment described above in that the columnar protrusions 4 are not uniformly arranged over the entire diffraction region 3 of the substrate 2 of the light guide plate 1B. Since the other points are the same as in the first embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 4A, the backlight unit 100 </ b> B of the present embodiment includes a light guide plate 1 </ b> B in which a plurality of columnar protrusion units 40 are arranged in the diffraction region 3 of the surface 2 a of the substrate 2.
As shown in FIG. 4B, the columnar protrusion unit 40 is a rectangular region including, for example, about several hundred to several thousand columnar protrusions 4 arranged in the same manner as in the first embodiment. Here, the number of the columnar protrusions 4 of the columnar protrusion unit 40 is not particularly limited as long as it is a range that causes diffraction in incident light.

  As shown in FIG. 4A, the columnar protrusion units 40 are arranged with different densities depending on the positions in the diffraction region 3 on the surface 2 a of the substrate 2. Specifically, the closer to each light source R, G, B, the lower the arrangement density of the columnar projection units 40, and the farther from each light source R, G, B, the higher the arrangement density of the columnar projection units 40.

  Generally, in the diffraction region 3 of the substrate 2, the closer to the light sources R, G, B, the more light Lr, Lg, Lb from the light sources R, G, B is diffracted. The closer to the light source, the higher the luminance, and the farther from the light sources R, G, B, the lower the luminance. However, according to the present embodiment, the amounts of the light Lr, Lg, and Lb that are diffracted and emitted in the direction perpendicular to the surface 2a (Z-axis direction) of the substrate 2 are adjusted by the density of the columnar protrusion units 40, and the diffraction region 3 The brightness inside can be made uniform.

<Third embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. In this embodiment, light Lr, Lg, Lb from each light source R, G, B is reflected in the direction of each light source R, G, B on the opposite side across the diffraction region 3 of each light source R, G, B. This is different from the first and second embodiments described above in that the mirrors Mr, Mg, and Mb are arranged. Since the other points are the same as those of the first and second embodiments, the same portions are denoted by the same reference numerals and the description thereof is omitted.

  As shown in FIG. 5, the backlight unit 100C of this embodiment includes a light guide plate 1C having an octagonal planar shape. Similarly to the first embodiment, a red light source R is provided on a side surface 2y parallel to the Y axis of the substrate 2C of the light guide plate 1C, and a red color is provided on the opposite side surface 2y ′ across the diffraction region 3 of the substrate 2C. A red light reflecting mirror Mr that reflects the light Lr is provided. The red light reflecting mirror Mr is installed with the angle adjusted so that the reflected red light Lr ′ is reflected in the X-axis direction in plan view.

  Similarly, a green light reflecting mirror Mg for reflecting the green light Lg in the Y-axis direction in plan view is provided on the opposite side of the green light source G with the diffraction region 3 interposed therebetween. On the opposite side, a blue light reflecting mirror Mb that reflects the blue light Lb in a direction perpendicular to the row L3 of the columnar protrusions 4 is provided.

According to the present embodiment, the light Lr, Lg, and Lb irradiated from the light sources R, G, and B and passed through the diffraction region 3 without being diffracted in the Z-axis direction in the diffraction region 3 are converted into the reflection mirrors Mr, Mg. , Mb can be reflected in the opposite direction and can be incident on the diffraction region 3 again. Therefore, the light Lr, Lg, Lb diffracted in the Z-axis direction in the diffraction region 3 can be increased, and the luminance can be improved.
As a modification of the present embodiment, the light sources R, G, and B are arranged in place of the reflecting mirrors Mr, Mg, and Mb, and the light Lr, Lg, and Lb are irradiated from both sides of the diffraction region 3. May be. Thereby, the same effect as the case where each reflection mirror Mr, Mg, and Mb is installed can be acquired.

(Liquid crystal display device)
Next, a liquid crystal display device including the backlight unit 100 described in the above embodiment will be described.
FIG. 6 is a schematic cross-sectional view showing a liquid crystal display device. The liquid crystal display device 50 includes an element substrate 51, a counter substrate 52 disposed opposite to the element substrate 51, a liquid crystal layer 53 disposed between the element substrate 51 and the counter substrate 52, and an outside of the element substrate 51 (liquid crystal And a backlight unit 100 disposed on the opposite side of the layer 53. In the liquid crystal display device 50, the element substrate 51 and the counter substrate 52 are bonded together with a sealing material 55, and the liquid crystal layer 53 is sealed between the element substrate 51 and the counter substrate 52 by the sealing material 55. Yes.

  The element substrate 51 has a substantially rectangular shape in plan view and uses a glass substrate as a base. Various metal films, insulating films, semiconductor layers, impurity layers, and the like are formed on the glass substrate. The element substrate 51 includes a pixel portion including a pixel electrode, a thin film transistor (TFT) and a storage capacitor formed on a glass substrate using a technique such as a photolithography technique or an inkjet method, and a pixel. Wiring portions for supplying electrical signals and the like. Further, an alignment film that controls the alignment of liquid crystal molecules constituting the liquid crystal layer 53 is formed on the inner surface of the element substrate 51 (the surface on the liquid crystal layer 53 side).

  Similar to the element substrate 51, the counter substrate 52 has a substantially rectangular shape in plan view and has a glass substrate as a base, and a black matrix, a color filter layer, a protective film, an electrode, and the like are formed on the glass substrate. . An alignment film is formed on the inner surface of the counter substrate 52. This alignment film is formed so that the alignment direction of the liquid crystal molecules is orthogonal to the alignment direction of the alignment film formed on the element substrate 51.

The reflection plate 57 is disposed outside the light guide plate 1 (side away from the surface 2 a of the substrate 2), and reflects the light Lr, Lg, Lb transmitted through the light guide plate 1 toward the light guide plate 1. It has become.
In the backlight unit 100, the light guide plate 1 is disposed between the liquid crystal display device 50 and the reflection plate 57, and the diffraction region 3 and the image display region of the liquid crystal display device 50 are disposed so as to overlap in a plane. Yes.

  The liquid crystal display device 50 configured as described above includes the backlight unit 100 that has good color reproducibility and prevents occurrence of color unevenness, so that the display performance of the liquid crystal display device 50 can be improved. it can.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the columnar protrusions have been described as being arranged in a vertical grid pattern. However, as long as the columnar protrusions are arranged in a square grid pattern in the first direction and the second direction intersecting each other. The arrangement of the columnar protrusions may not be a vertical grid.
Further, the planar shape of the light guide plate is not limited to the shape described in the above embodiment.

  Moreover, you may arrange | position the light-diffusion film (light-diffusion layer) which diffuses light to the front end side of a columnar protrusion. As a result, even when the incident angle of each light fluctuates and the emission angle is no longer perpendicular to the one surface of the substrate, the light is diffused to emit the light emitted in the direction perpendicular to the one surface of the substrate. Can be increased. Accordingly, light of each color can be uniformly synthesized on one surface of the substrate, and color unevenness due to a difference in position within the one surface of the substrate can be prevented.

In the second embodiment described above, by adjusting the arrangement density of the columnar protrusion units in the diffraction region to adjust the luminance in the diffraction region to be uniform, the luminance adjustment is performed by adjusting the diameter of the columnar protrusion. You may carry out by changing, changing the height of a columnar protrusion, or changing the shape of a columnar protrusion.
Further, the columnar protrusions may be formed of a thermosetting resin.

Moreover, as a resin material which comprises a light-guide plate, other than the polycarbonate (PC) demonstrated in the above-mentioned embodiment, for example, polyethylene, polypropylene, an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer (EVA) Such as polyolefin, cyclic polyolefin, modified polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide (for example, nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 6-12, nylon 6-66), polyimide, polyamideimide, poly- (4-methylpentene-1), ionomer, acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-styrene copolymer (A Resin), butadiene-styrene copolymer, polyoxymethylene, polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT) Polyester, polyether, polyetherketone (PEK), polyetheretherketone (PEEK), polyetherimide, polyacetal (POM), polyphenylene oxide, modified polyphenylene oxide, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate , Aromatic polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluororesins, styrene, poly Various thermoplastic elastomers such as olefin, polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene, trans polyisoprene, fluoro rubber, chlorinated polyethylene, epoxy resin, phenol resin, urea resin, melamine Resins, unsaturated polyesters, silicone resins, urethane resins, and the like, and copolymers, blends, polymer alloys, etc. mainly composed of these, and combinations of one or more of these (for example, , Blend resins, polymer alloys, laminates, etc.).
Note that the light guide plate is not limited to the resin material, and may be made of other materials as long as it shows translucency in the wavelength region to be used.

  Further, the transmittance of the optical element is preferably 85% or more, and more preferably 90% or more, in the wavelength region of light to be used. Thereby, the extraction efficiency of light incident on the light guide plate is improved.

  The refractive index of the optical element is preferably 1.4 or more and 1.7 or less. Thereby, the utilization efficiency of the light incident on the light guide plate can be further improved, and the emitted light can have high directivity. Moreover, it can prevent that the function as a photonic crystal is not fully demonstrated by the temperature, humidity, etc. of the surrounding environment of a light-guide plate.

  In the above-described embodiment, the example in which the optical element of the present invention is applied to the light guide plate has been described, but it goes without saying that the optical element of the present embodiment can be applied to other than the light guide plate. Moreover, although the edge system was demonstrated in the above-mentioned embodiment, you may arrange | position the optical element of this invention directly on light sources, such as organic EL and a semiconductor laser, for example.

It is a figure which shows the structure of the backlight unit in 1st embodiment of this invention, (a) is a top view, (b) is arrow sectional drawing which follows the A-A 'line of (a). It is a figure which shows the arrangement | sequence of the columnar protrusion in 1st embodiment of this invention, (a) is a top view, (b) is sectional drawing. It is a figure which shows the modification of the columnar protrusion in 1st embodiment of this invention, (a) is a top view, (b) is a perspective view of a columnar protrusion. It is a figure which shows the structure of the backlight unit in 2nd embodiment of this invention, (a) is a top view, (b) is an enlarged plan view of a columnar projection unit. It is a top view which shows the structure of the backlight unit in 3rd embodiment of this invention. It is sectional drawing which shows schematic structure of the liquid crystal display device in embodiment of this invention.

Explanation of symbols

1, 1B, 1C Light guide plate (optical element), 2, 2C substrate, 2a surface (one surface), 2b, 2x, 2y side surface, 3 diffraction region, 4, 4b columnar projection, 40 columnar projection unit, 50 liquid crystal display device, 51 element substrate, 52 counter substrate, 53 liquid crystal layer, 55 sealing material, 57 reflector, 100, 100B, 100C backlight unit (light source unit), α1, α2, α3 incident angle, β1, β2, β3 emission angle, λ1 , Λ2, λ3 wavelength, d1, d2, d3 spacing, a, n refractive index, B blue light source (third light source), G green light source (second light source), L1, L2, L3 rows, Lb blue light ( Third light), Lg green light (second light), Lr red light (first light), Mb, Mg, Mr mirror, N1, N2, N3 integer, R red light source (first light source), U unit cell

Claims (10)

An optical element having a substrate and a plurality of columnar protrusions provided on one surface of the substrate, and conducting light inside,
The columnar protrusions are arranged in a grid pattern in a first direction and a second direction intersecting each other, and in the first direction, an interval corresponding to the wavelength of the first light incident from the first direction. Arranged in the second direction at an interval corresponding to the wavelength of the second light incident from the second direction,
The columnar projections arranged in a third direction intersecting both the first direction and the second direction have a wavelength of the third light incident from a direction orthogonal to the third direction. An optical element characterized by being arranged at corresponding intervals. The interval between the columnar protrusions in the first direction is d1, the interval between the columnar protrusions in the second direction is d2, and the interval between the columnar protrusions in the third direction is d3,
The wavelength of the first light is λ1, the wavelength of the second light is λ2, the wavelength of the third light is λ3,
The incident angle of the first light incident on one surface of the substrate is α1, the incident angle of the second light is α2, the incident angle of the third light is α3,
The emission angle of the first light emitted from one surface of the substrate is β1, the emission angle of the second light is β2, the emission angle of the third light is β3,
The refractive index of the substrate is n, the refractive index of air is a,
When N1, N2, and N3 are integers,
The intervals d1, d2, and d3 satisfy the relationships of the following formulas (1), (2), and (3), respectively, and the emission angles β1, β2, and β3 correspond to the wavelengths λ1, λ2, and λ3, respectively. The optical element according to claim 1, wherein the optical element is adjusted to a predetermined value.
d1 · (n · sin α1−a · sin β1) = N1 · λ1 (1)
d2 · (n · sin α2−a · sin β2) = N2 · λ2 (2)
d3 · (n · sin α3-a · sin β3) = N3 · λ3 (3)   3. The optical element according to claim 2, wherein the distances d1, d2, and d3 are adjusted so that each of the emission angles β1, β2, and β3 approaches 0 °. The first direction is orthogonal to the second direction;
4. The optical element according to claim 1, wherein the third direction is parallel to a diagonal of a unit cell in which the four columnar protrusions are arranged in a rectangular shape. 5.   5. The optical element according to claim 4, wherein a plurality of columnar protrusion units having a plurality of the unit lattices are arranged on one surface of the substrate, and the arrangement density of the columnar protrusion units varies depending on a position in the one surface of the substrate.   The optical element according to any one of claims 1 to 5, wherein the columnar protrusion has a parabolic shape in a cross-sectional shape perpendicular to one surface of the substrate.   The optical element according to any one of claims 1 to 6, wherein the columnar protrusion has an elliptical cross-sectional shape parallel to one surface of the substrate.   The optical element according to claim 1, wherein a light diffusion layer is provided on the columnar protrusion side of the substrate.   9. The first light according to claim 1, wherein the first light is red light, the second light is green light, and the third light is blue light. The optical element described. The optical element according to any one of claims 1 to 9, comprising:
A first light source that makes the first light incident on the substrate from the first direction;
A second light source that makes the second light incident on the substrate from the second direction;
A third light source that makes the third light incident on the substrate from a direction perpendicular to the third direction;
A light source unit comprising:

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