KR20100126393A - Optical element, and light source unit and liquid crystal display device provided with the optical element - Google Patents

Abstract

The present invention provides an optical element having high light extraction efficiency and capable of eliminating luminance unevenness in two orthogonal directions of a backlight in which point light sources are arranged in a matrix. According to the present invention, the optical element 3 includes a light transmissive optical sheet 20 and a light diffusion sheet 10. The optical sheet 20 has a light incident surface 20a and a light exit surface 20b. On at least one of the light incident surface 20a and the light exit surface 20b, a plurality of micro lenses 22 formed convexly or concavely are arranged in a cyclic or matrix form at a pitch of less than 10 m. ) Is formed. The light diffusion sheet 10 is disposed on the light exit surface 20b side of the optical sheet 20. The light diffusion sheet 10 diffuses by refracting incident light.

Description

Optical element, light source unit and liquid crystal display having the same {OPTICAL ELEMENT, AND LIGHT SOURCE UNIT AND LIQUID CRYSTAL DISPLAY DEVICE PROVIDED WITH THE OPTICAL ELEMENT}

The present invention relates to an optical element, a light source unit having the same, and a liquid crystal display device.

Background Art Conventionally, a so-called direct backlight is known. In a direct backlight, a plurality of light sources are arranged below the light exit surface. For this reason, in the light emission surface of a backlight, the brightness | luminance just above a light source tends to become higher than other parts. That is, the so-called lamp image tends to be easily visible.

Conventionally, for example, in patent documents 1-5 etc., the method of eliminating this luminance nonuniformity is proposed variously. For example, Patent Document 1 discloses a method of arranging a light diffusion plate using a light diffusion material on a light source.

In addition, Patent Document 6 discloses an optical sheet having a microlens array having a diameter of the microlenses of 10 µm or more and less than 100 µm. Patent Document 6 discloses that the optical sheet can achieve high luminance in the front direction and uniformity in luminance. In addition, Patent Document 6 discloses that when the diameter of the microlenses is smaller than 10 mu m, the influence of diffraction increases and the visual quality decreases, so that the diameter of the microlenses is preferably 10 mu m or more, particularly preferably 20 mu m or more. The purpose is described.

Japanese Patent Laid-Open No. 54-155244 Japanese Patent No. 2852424 Japanese Patent Laid-Open No. 2000-338895 Japanese Patent Laid-Open No. 2002-352611 US Patent No. 5161041 Japanese Patent Laid-Open No. 2004-145329

When the light diffusing plate using the light diffusing material as disclosed in Patent Document 1 is disposed on the backlight of the direct system, absorption of light by the light diffusing material and light diffusion in an unnecessary direction occur. For this reason, the light diffusion plate using the light diffusion material has low light extraction efficiency. Therefore, simply disposing the light diffusion plate using the light diffusing material on the backlight can solve the luminance unevenness, but there is a problem that the utilization efficiency of the light emitted from the backlight is lowered.

In addition, in the methods disclosed in Patent Literatures 2 to 5, although the luminance nonuniformity of the backlight having the linear light sources arranged in parallel with each other can be solved, it is sufficient to sufficiently resolve the luminance nonuniformity of the backlight provided with the point light sources arranged in a matrix. There is a problem that is difficult. In detail, although the luminance nonuniformity of the backlight in the predetermined direction can be solved, there is a problem that it is difficult to sufficiently eliminate the luminance nonuniformity of the backlight in the direction perpendicular to the predetermined direction.

This invention is made | formed in view of such a point, The objective is providing the optical element which is high in the light extraction efficiency and can eliminate the brightness nonuniformity in two orthogonal directions of the backlight in which a point light source was arrange | positioned in matrix form. It is in doing it.

The optical element which concerns on this invention is equipped with the optical sheet which has a light incidence surface and a light emission surface, and the light-diffusion sheet arrange | positioned at the light emission surface side of an optical sheet and refracting incident light. On at least one of the light incident surface and the light exit surface, a micro lens array is formed. In the microlens array, a plurality of microlenses formed in a convex shape or a concave shape is arranged periodically and in a matrix at a pitch of less than 10 m.

In one particular aspect of the present invention, the microlenses are formed convexly, and the microlens array is formed on the light exit surface.

In the present invention, the pitch of the microlens array is preferably 5 μm or less, more preferably 3 μm or less.

In another particular aspect of the present invention, the light diffusion sheet has a micro lens array in which a plurality of micro lenses are arranged at a pitch of 10 m or more.

In another particular aspect of the invention, the microlenses of the optical sheet are approximately circular in plan view, and the diameter of the microlenses of the optical sheet in plan view is at least 50% of the pitch of the microlens array of the optical sheet. Preferably it is 80% or more.

According to another specific aspect of the present invention, the microlens occupies 80% or more of the light incidence plane and the light outgoing plane on the side where the microlens array is formed. In the coordinate system shown in FIG. 17 in which the aspect ratio of the microlens obtained by dividing the height of the microlens by the diameter of the microlens as the Y axis, (the pitch of the microlens array and the aspect ratio of the microlens) are points A (1.0, 0.875). ), Points B (1.0, 0.625), points C (1.5, 0.375), points D (2.0, 0.375), points E (2.0, 0.625), and points F (1.5, 0.875) formed in this order by connecting them in a straight line It is located in the area which becomes.

In another specific aspect of the present invention, in the coordinate system shown in Fig. 17, the pitch (μm) of the microlens array is the X axis, and the aspect ratio of the microlens obtained by dividing the height of the microlens by the diameter of the microlens is the Y axis. , (The pitch of the microlens array, the aspect ratio of the microlens) are linear in this order to point G (1.0, 0.75), point H (1.5, 0.5), point I (2.0, 0.5) and point J (1.5, 0.75) It is located in the area formed by connecting.

In another specific aspect of the present invention, the microlens array is formed such that the optical sheet has a peak of transmitted light having a transmittance higher than the transmittance at the diffusion angle of 0 ° at a diffusion angle other than 0 °.

In another particular aspect of the present invention, the plurality of micro lenses are regularly and periodically arranged in both the first direction and the second direction orthogonal to the first direction.

In another particular aspect of this invention, the several microlens of an optical sheet is arrange | positioned so that the figure formed by connecting the center of the adjacent microlens in planar view may become an equilateral triangle.

A light source unit according to the present invention includes the optical element according to the present invention and a light source device. The light source device is disposed on the light incident surface side of the optical element. The light source device emits light toward the light incident surface.

The light source device may be one having a plurality of point light sources.

The liquid crystal display device which concerns on this invention is equipped with the light source unit which concerns on the said invention, and the liquid crystal display cell arrange | positioned at the light emission surface side of the light-diffusion sheet.

According to the present invention, since the optical sheet has a microlens array having a pitch of less than 10 m and a light diffusing sheet for diffusing the incident light to be diffused is arranged on the light exit surface side of the optical sheet, the light extraction efficiency can be increased. In addition, luminance unevenness in two orthogonal directions of the backlight in which the point light sources are arranged in a matrix can be eliminated.

1 is a schematic cross-sectional view of a liquid crystal display device according to an example of a preferred embodiment of the present invention.
FIG. 2 is a plan view showing a part of the light diffusion sheet. FIG.
FIG. 3 is a diagram illustrating a part indicated by the III-III arrow in FIG. 2.
FIG. 4 is a plan view showing a part of an optical sheet. FIG.
FIG. 5 is a diagram illustrating a portion indicated by the VV arrow in FIG. 4.
FIG. 6 is a plan view of the light source device. However, illustration of the translucent substrate 33 is omitted.
FIG. 7 is a graph showing the relationship between the diffusion angle and the transmittance when the pitch of the microlens array is 50 µm.
FIG. 8 is a graph showing the relationship between the diffusion angle and the transmittance when the pitch of the micro lens array is 9.9 µm.
9 is a graph showing the relationship between the diffusion angle and the transmittance when the pitch of the microlens array is 5 µm.
10 is a graph showing the relationship between the diffusion angle and the transmittance when the pitch of the microlens array is 3 µm.
FIG. 11 is a graph showing the relationship between the diffusion angle and the transmittance when the pitch of the microlens array is 1.8 µm.
FIG. 12 is a graph showing the relationship between the pitch and the diffusion angle of the microlens array when n = 2 and lambda = 550 nm in the equation (1).
FIG. 13: is a top view which shows a part of optical sheet in the modification 1. As shown in FIG.
FIG. 14 is a plan view of the light source device in Modification Example 2. FIG.
FIG. 15 is a diagram illustrating a portion indicated by an XV-XV arrow in FIG. 14.
FIG. 16: is sectional drawing which shows a part of optical sheet in the modification 3. As shown in FIG.
FIG. 17 is a graph showing the relationship between the pitch of the micro lens array and the aspect ratio of the micro lens. FIG.
<Description of the code>
One… Liquid crystal display
2… Light source unit
3 ... Optical element
10... Light diffusion sheet
10a, 20a... Light incident surface
10b, 20b, 30a... Light exit surface
11, 21... Micro lens array
12, 22, 25... Micro lens
20... Optical sheet
30... Light source device
31... Casing
31a... Recess
32... Point light source
33 ... Translucent substrate
34... Linear light source
40 ... Liquid crystal display cell
41a, 41b... Polarizer

Hereinafter, an example of the preferable form which implemented this invention is demonstrated taking the liquid crystal display device 1 shown in FIG. 1 as an example. However, the liquid crystal display device 1 is a mere illustration, and this invention is not limited to the liquid crystal display device 1.

As shown in FIG. 1, the liquid crystal display device 1 includes a liquid crystal display cell 40, a pair of polarizing plates 41a and 41b, and a light source unit 2. The liquid crystal display cell 40 is disposed between the pair of polarizing plates 41a and 41b. The polarizing plate 41a and the polarizing plate 41b are arrange | positioned so that a polarization direction may orthogonally cross.

The light source unit 2 is provided with the light source device 30 and the optical element 3.

In the present invention, the light source device 30 is not particularly limited. The light source device 30 may, for example, have a plurality of point light sources such as a light emitting diode (LED). The light source device 30 may also have a plurality of linear light sources such as a cold cathode tube.

In this embodiment, as shown in FIG. 1, the light source device 30 includes a casing 31, a plurality of point light sources 32, and a light-transmitting substrate 33. The casing 31 is formed with a recess 31a. The plurality of point light sources 32 are disposed in the recess 31a. As shown in Fig. 6, the plurality of point light sources 32 are arranged periodically and in matrix. In addition, drawing of the translucent board | substrate 33 is abbreviate | omitted in FIG.

The recessed part 31a of the casing 31 is covered with the light transmissive substrate 33. Light of the point light source 32 is emitted from the translucent substrate 33.

The light transmissive substrate 33 may be, for example, a diffuser plate having a function of diffusing light. In addition, a light diffusion plate may be further disposed on the light-transmitting substrate 33.

As shown in FIG. 1, the optical element 3 is arrange | positioned at the light emission surface 30a side of the light source device 30. As shown in FIG. The optical element 3 is provided with the light transmissive optical sheet 20 and the light transmissive light diffusion sheet 10. The optical sheet 20 is arrange | positioned on the light emission surface 30a of the light source device 30. As shown in FIG.

The light diffusion sheet 10 is disposed on the light exit surface 20b side of the optical sheet 20. Specifically, in the present embodiment, the light diffusion sheet 10 is disposed above the light exit surface 20b. The light diffusion sheet 10 diffuses by refracting incident light incident on the optical sheet 20 side.

In the present invention, the light diffusion sheet is not particularly limited as long as it diffuses by refracting incident light. In this embodiment, the case where the light-diffusion sheet 10 has a micro lens array is demonstrated as an example. However, the light diffusion sheet 10 may be, for example, a bead coated light diffusion sheet, a prism sheet, a reflective polarizing function sheet, or the like.

In addition, although the example which arrange | positions one light-diffusion sheet 10 is demonstrated in this embodiment, multiple light-diffusion sheet 10 can also be arrange | positioned. In the case where a plurality of light diffusion sheets 10 are disposed, a plurality of light diffusion sheets of the same kind may be disposed, or a plurality of light diffusion sheets may be disposed.

As shown in FIG. 3, the light diffusion sheet 10 includes a light incident surface 10a and a light emitting surface 10b. The light diffusion sheet 10 is provided with the micro lens array 11 formed in the light emission surface 10b. The microlens array 11 is provided with the some microlens 12 arrange | positioned periodically and matrix form as shown in FIG.

The arrangement of the plurality of micro lenses 12 is not particularly limited. The plurality of micro lenses 12 may be regularly and periodically arranged in each of the first direction and the second direction orthogonal to the first direction, for example. That is, the plurality of micro lenses 12 may be arranged in a so-called square lattice pattern. As shown in Fig. 2, the plurality of microlenses 12 are so-called triangles so that the figure formed by connecting the centers of adjacent microlenses 12 in a plan view becomes a triangle (preferably an equilateral triangle). It may be arranged in a grid pattern (preferably an equilateral triangle grid pattern).

Specifically, in the present embodiment, as shown in FIG. 2, the so-called equilateral triangle lattice pattern is arranged so that the figure T ₁ formed by connecting the centers C ₁ to C ₃ of the adjacent microlenses 12 becomes an equilateral triangle. Thus, by arranging the plurality of micro lenses 12 in a so-called equilateral triangle lattice pattern in plan view, the number of micro lenses 12 arranged per unit area can be increased. That is, the occupancy rate of the microlens 12 can be made high. Therefore, it is possible to realize a high diffusion function.

As shown in FIG.2 and FIG.3, in this embodiment, the shape of the micro lens 12 is hemispherical. However, in the present invention, the shape of the microlens 12 is not particularly limited. The microlens 12 may be formed, for example, in the shape of an elliptic sphere, a cone, a cone, a cone, or a cone.

The plurality of micro lenses 12 are arranged at a pitch of 10 μm or more. It is preferable that the pitch of the micro lens array 11 is 20 micrometers or more, for example.

In addition, in this specification, the "pitch of a micro lens array" means the shortest distance among the distances between the centers of adjacent micro lenses. Specifically, the plurality of micro lenses 12, the case shown in Figure 2 is, since the shape formed by connecting the centers of the microlenses 12 which are adjacent are arranged such that an equilateral triangle, and also the pitch P ₁ in Fig. 2 Pitch P ₂ is equal. Therefore, the pitch P of the micro lens array 11 in this embodiment is equal to the pitch P ₁ and the pitch P _2.

In the present embodiment, the diameter D ₁ of the microlens 12 is not particularly limited. The diameter D ₁ of the microlens 12 can be appropriately set according to the pitch P and the occupancy rate of the microlens array 11. For example, the diameter D ₁ of the micro lens 12 can be about 15-100 micrometers.

The material of the light diffusion sheet 10 is not particularly limited. The light diffusion sheet 10 may be formed of a synthetic resin, for example. As a specific example of synthetic resin, polyethylene terephthalate etc. are mentioned, for example.

Moreover, the average thickness of the light-diffusion sheet 10 is not specifically limited, either. It is preferable that the average thickness of the light-diffusion sheet 10 is about 50-400 micrometers, for example.

As shown in FIG. 1, the optical sheet 20 is disposed on the light source device 30. However, the optical sheet 20 does not necessarily need to be disposed directly above the light source device 30. Another optical element may be disposed between the light source device 30 and the optical sheet 20. For example, a light diffusion plate, a prism sheet, or the like may be disposed between the optical sheet 20 and the light source device 30. In addition, an air layer may be interposed between the light source device 30 and the optical sheet 20.

The optical sheet 20 is provided with the light incident surface 20a and the light emitting surface 20b. The light incident surface 20a faces the light source device 30. The light exit surface 20b faces the light diffusion sheet 10.

The optical sheet 20 is equipped with the micro lens array 21 as shown to FIG. 4 and FIG.

The micro lens array 21 is formed on at least one of the light incident surface 20a and the light emitting surface 20b. Specifically, in this embodiment, as shown to FIG. 1 and FIG. 5, it is formed in the light output surface 20b of the optical sheet 20. As shown in FIG.

The micro lens array 21 includes a plurality of micro lenses 22. Each of the plurality of micro lenses 22 is formed in a convex or concave shape. In the present embodiment, the micro lens array 21 includes a plurality of micro lenses 22 formed in a convex shape. More specifically, in this embodiment, the micro lens 22 is formed in hemispherical shape. However, in the present invention, the shape of the micro lens 22 is not limited to this. The microlens 22 may be formed in the shape of, for example, an elliptical sphere, a cone, a cone, a cone or a cone.

The plurality of micro lenses 22 are arranged periodically and in matrix. The plurality of micro lenses 22 may be regularly and periodically arranged in both the first direction and the second direction orthogonal to the first direction, for example. In other words, the plurality of micro lenses 22 may be arranged in a so-called square lattice pattern, for example. Further, the plurality of micro lenses 22, as shown in Figure 4, connecting the center C ₄ to C ₆ of the micro-lens 22 adjacent to the formed shapes T ₂ may be arranged such that the triangle. That is, the plurality of micro lenses 22 may be arranged in a so-called triangular lattice pattern. A plurality of micro lenses 22, it is preferable that among the triangular lattice pattern, a figure T ₂ are arranged in a regular triangle lattice pattern is a regular triangle.

In the present embodiment, the pitch P (= P ₃ = P ₂ ) of the micro lens array 21 is set to less than 10 μm. It is preferable that the pitch of the micro lens array 21 is 5 micrometers or less, It is more preferable that it is 3 micrometers or less, It is further more preferable that it is 2.5 micrometers or less.

It is preferable that pitch P of the microlens array 21 is 0.3 micrometer or more, and it is more preferable that it is 0.7 micrometer or more. This is because formation of the micro lens array 21 tends to be difficult when the pitch P of the micro lens array 21 becomes small.

In this embodiment, since the pitch P of the micro lens array 21 is set to less than 10 micrometers, diffracted light generate | occur | produces in the micro lens array 21. As shown in FIG. With respect to the microlens array 21, when light rays are incident in the normal direction, the diffracted light is intensified with each other at an angle θ that satisfies the following expression (1).

only,

P: pitch of the micro lens array 21,

n: natural number,

λ: The wavelength of light rays incident on the micro lens array 21.

In the present embodiment, the diameter D ₂ of the microlens 22 is not particularly limited. However, the diameter D ₂ of the microlenses 22 is preferably not less than 50% of the pitch P of the micro lens array 21, and is preferably not less than 80%. By making the diameter D ₂ of the micro lens 22 relatively large with respect to the pitch P of the micro lens array 21, the micro lens in the region where the micro lens 22 of the light exit surface 20b of the optical sheet 20 is formed. The share of (22) can be made relatively high. It is preferable that it is 20% or more, and, as for the occupancy rate of the microlens 22, it is more preferable that it is 50% or more.

In addition, in this specification, the occupancy rate of a microlens is a ratio of the area of the microlens to the area of the surface where the microlens is formed in plan view. Specifically, a rear 4, the case shown in, refers to the proportion of the area of the micro lens 22 which is located within a regular triangle T ₂ to the area of an equilateral triangle T ₂ surrounded by the center C ₄ to C ₆ of the microlens 22.

The material of the optical sheet 20 is not particularly limited as long as it has light transmittance. The optical sheet 20 can be formed, for example with the light transmissive synthetic resin. Specific examples of the synthetic resin include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride, energy curable resin, and the like. Specific examples of the energy curable resins include ultraviolet curable resins and electron beam curable resins. Among these, the energy curable resin represented by ultraviolet curable resin, electron beam curable resin, etc. is especially preferable. This is because the microlens array 21 can be formed relatively easily by using an energy curable resin.

In addition, the optical sheet 20 may be formed integrally, and the some optical member may be joined. Specifically, the microlens formed by ultraviolet curable resin etc. may be affixed on optical films, such as a polyethylene terephthalate film, a polyethylene naphthalate film, or a polycarbonate film.

In addition, the optical sheet 20 may include at least one of various fillers, plasticizers, stabilizers, deterioration inhibitors and dispersants.

The thickness of the optical sheet 20 is not particularly limited. The average thickness of the optical sheet 20 may be 10 micrometers or more and 3000 micrometers or less, for example. In consideration of the light transmittance of the optical sheet 20, the average thickness of the optical sheet 20 is preferably 35 µm or more and 300 µm or less, and more preferably 50 µm or more and 250 µm or less.

On the other hand, when the mechanical strength of the optical sheet 20 is considered, the preferable range of the average thickness of the optical sheet 20 is 1000 micrometers or more and 2500 micrometers or less, and 1200 micrometers or more and 2000 micrometers or less are more preferable.

If the thickness of the optical sheet 20 is too thin, there is a fear that the shape of the optical sheet 20 changes due to heat such as the light source device 30 or the like. On the other hand, when the thickness of the optical sheet 20 is too thick, there exists a tendency for the light transmittance of the optical sheet 20 to fall.

The manufacturing method of the optical sheet 20 is not specifically limited, either. The optical sheet 20 can be manufactured by various known manufacturing methods. As a manufacturing method of the optical sheet 20, after forming a synthetic resin layer on a shaping | molding die, for example, the method of peeling the synthetic resin layer from a shaping | molding die, and heat-pressing sheeted resin using a shaping | molding die The method etc. are mentioned.

As explained above, the optical element 3 of this embodiment is equipped with the microlens array 21 whose pitch P is less than 10 micrometers, and the light-diffusion sheet 10 which diffuses by refracting incident light. Therefore, compared with the case where only the light diffusing plate which diffuses by refracting light, for example instead of the optical element 3, both high extraction efficiency and high light diffusivity are implement | achieved.

As also described in Patent Document 6, from the viewpoint of suppressing the color dispersion small, the pitch of the microlens array 21 is usually set to 10 µm or more. However, when the pitch of the micro lens array 21 is set to 10 micrometers or more, it becomes difficult to diffuse light sufficiently.

In contrast, in the present embodiment, the light diffusing sheet 10 which diffuses by refracting incident light is combined with the micro lens array 21 having high light diffusing ability. For this reason, the color dispersion generated in the microlens array 21 can be effectively canceled by the light diffusing sheet 10 while realizing high light diffusivity in the microlens array 21. Therefore, while realizing high light diffusivity, it is possible to effectively suppress the visibility of the rainbow color pattern due to color dispersion.

In addition, in the microlens array 21, a plurality of minute microlenses 22 are arranged in a matrix. For this reason, light can be disperse | distributed not only in one direction but in two directions orthogonal to each other. Therefore, by using the optical element 3, it becomes possible to eliminate the luminance nonuniformity in two orthogonal directions of the backlight in which the point light source was arrange | positioned in matrix form.

Hereinafter, the effect in this embodiment is demonstrated in detail.

7 is a graph showing the relationship between the diffusion angle and the transmittance of the emitted light in the microlens array having a pitch of 50 µm. In the case of a micro lens array having a pitch of 50 mu m, diffracted light does not substantially occur in the micro lens array. For this reason, as shown in FIG. 7, in the case of a microlens array having a pitch of 50 mu m, transmitted light concentrates at a position of diffusion angle = 0 degrees. Thus, for example, when a microlens array having a pitch of 50 mu m is disposed on the light source device 30, the luminance at the position corresponding to the point light source 32 becomes higher than other portions. As a result, relatively large luminance nonuniformity is visually recognized.

7 to 12 are graphs in the case where the wavelength of incident light is 550 nm.

8 is a graph showing the relationship between the diffusion angle of the emitted light and the transmittance in the microlens array 21 having a pitch of 9.9 µm. In the case of the micro lens array 21 having a pitch of 9.9 占 퐉, diffracted light is generated in the micro lens array 21. For this reason, in the area | region whose diffusion angle is -30-30 degree, several peaks of the transmitted light resulting from diffracted light generate | occur | produce. Therefore, compared with the case where the pitch of the microlens array 21 is 50 µm, the transmittance at the diffusion angle of 0 degrees is lowered, and the transmittance at the diffusion angle of -30 to 0 degrees and 0 to 30 degrees is increased. Therefore, luminance unevenness can be reduced.

Further, diffraction light may be generated even when the pitch of the micro lens array is 10 μm or more. However, as shown in FIG. 12, when the pitch of a micro lens array is 10 micrometers or more, the diffusion angle obtained will become very small. Therefore, if the pitch of a micro lens array is 10 micrometers or more, light cannot fully diffuse. As a result, it becomes difficult to fully suppress luminance nonuniformity.

As shown in FIG. 12, when the pitch of the micro lens array 21 is less than 10 micrometers, a diffusion angle becomes remarkably large. For this reason, a large diffusion angle is obtained by setting the pitch of the micro lens array 21 to less than 10 micrometers. As a result, the luminance nonuniformity can be effectively reduced.

9 to 11 are graphs showing the relationship between the diffusion angle and the transmittance of the emitted light in the micro lens array 21 having the pitches of the micro lens array 21 having 5 µm, 3 µm and 1.8 µm, respectively. Specifically, as shown in FIG. 8, when the pitch of the microlens array 21 is 9.9 μm, a plurality of peaks of transmitted light appear, but the peaks of the plurality of transmitted light are close to each other. 9 to 11, when the pitch of the microlens array 21 is 5 μm or less, the distance between peaks of adjacent transmitted light is enlarged, and a large number of transmitted light is used in addition to just above the point light source 32. Peaks are scattered.

For example, when diffracted light does not occur, the peak of transmitted light exists at an interval substantially equal to the interval of the point light source 32. Therefore, the distance between peaks of adjacent transmitted light becomes relatively long. On the other hand, when the pitch of the microlens array 21 is 5 micrometers or less, as mentioned above, the peak of many transmitted light is scattered besides just above the point light source 32. As shown in FIG. As a result, the distance between peaks of adjacent transmitted light becomes relatively short. Therefore, the luminance nonuniformity becomes difficult to be visually recognized. Accordingly, the pitch of the micro lens array 21 is preferably 5 μm or less.

As shown in Fig. 12, the pitch of the microlens array 21 is particularly large when the pitch is 3 m. For this reason, it is more preferable that the pitch of the micro lens array 21 is 3 micrometers or less.

From the viewpoint of preventing the point light source 32 from being visually recognized, it is preferable that the transmitted light intensity immediately above the point light source 32 is small. In other words, it is preferable that the transmittance at the diffusion angle of 0 degrees is small.

9 to 11, it is more preferable that the transmittance of the peak of the transmitted light at the diffusion angle of 0 degrees is lower than that of the peak of the transmitted light at the diffusion angle other than 0 degrees. In other words, it is more preferable that the optical sheet 20 has a peak of transmitted light having a transmittance higher than the transmittance at the diffusion angle of 0 degrees at a diffusion angle other than 0 degrees.

Specifically, it is preferable that the ratio (occupancy) of the microlens 22 to the light exit surface 20b of the optical sheet 20 is large. More specifically, the occupancy ratio of the microlenses 22 in the region where the microlens array 21 of the light exit surface 20b is formed is preferably 20% or more, and more preferably 50% or more. By doing in this way, the quantity of light which permeate | transmits without diffusing the optical sheet 20 can be reduced, and diffraction light can be increased.

In addition, as in the present embodiment, when the shape in the plan view of the microlens 22 is substantially circular, the diameter of the microlens 22 is preferably 50% or more of the pitch of the microlens array 21. It is more preferable that it is 80% or more.

In view of increasing the occupancy rate of the microlenses 22, the microlenses 22 are arranged so that a figure formed by connecting the centers of the adjacent microlenses 22 becomes a triangle as shown in FIG. It is desirable to have. In addition, it is particularly preferable that the microlenses 22 are arranged so that a figure formed by connecting the centers of adjacent microlenses 22 is an equilateral triangle in plan view. This is because the largest share of the microlenses 22 can be obtained.

In addition, from the viewpoint of reducing the transmittance at the diffusion angle of 0 degrees, the occupancy ratio of the microlenses 12 on the light exit surface 20b is 80% or more, and the pitch (μm) of the microlens array 11 is represented by the X axis. In the coordinate system shown in FIG. 17 in which the aspect ratio of the microlens 12 obtained by dividing the height of the microlens 12 by the diameter of the microlens 12 is Y-axis, the pitch of the microlens array and the Aspect ratio) is point A (1.0, 0.875), point B (1.0, 0.625), point C (1.5, 0.375), point D (2.0, 0.375), point E (2.0, 0.625) and point F (1.5, 0.875) Is preferably located in the region X1 formed by connecting in a straight line in this order. In addition, in the coordinate system shown in FIG. 17, (the pitch of the micro lens array and the aspect ratio of the microlens) are represented by points G (1.0, 0.75), points H (1.5, 0.5), points I (2.0, 0.5), and points J ( It is more preferable to locate in the area | region X2 formed by connecting 1.5 and 0.75) linearly in this order. That is, when the aspect ratio of the microlens 22 is 0.5, that is, when the shape of the microlens 22 is hemispherical, the pitch of the microlens array 21 is preferably 1.25 to 2.0 mu m, preferably 1.5 to 2.0 mu m. More preferred. According to this configuration, the transmittance at the diffusion angle of 0 degrees can be 30% or less, and the transmittance at the diffusion angles other than 0 degrees can be 2% or more.

As described above, the kind of the light diffusion sheet 10 is not particularly limited. However, it is preferable that the light diffusion sheet 10 has the microlens array 11 whose pitch of the microlens array 11 is 10 micrometers or more similarly to this embodiment.

In the case of using the sheet having the microlens array 11 as the light diffusion sheet, for example, in the case of using the light diffusion sheet using the light diffusion material, the diffusion of light in an unnecessary direction and the absorption of light by the light diffusion material are suppressed. can do. Therefore, higher light extraction efficiency can be realized.

In addition, in this embodiment, the minimum function required for the light-diffusion sheet 10 is only a function which cancels the color dispersion which generate | occur | produced in the optical sheet 20. As shown in FIG. For this reason, compared with the light diffuser plate in the case where only the light diffuser plate which changes, for example, changes to the optical element 3 and refracts light, and changes it to the optical element 3 is arrange | positioned, The required light diffusivity is relatively low. Therefore, when the light-diffusion sheet 10 is comprised by the light-diffusion sheet which used the light-diffusion material, for example, the density | concentration of the light-diffusion material in the light-diffusion sheet 10 can be made low. Therefore, even when it is comprised by the light-diffusion sheet which used the light-diffusion material, compared with the light-diffusion plate in the case of changing and arrange | positioning only the light-diffusion plate which diffuses by refracting light into the optical element 3, a light-diffusion sheet ( Light diffusion in the unnecessary direction in 10) and light absorption can be suppressed. As a result, high light extraction efficiency can be realized.

It is preferable that not only the microlenses 22 are formed in a convex shape, but also the microlens array 21 is formed in the light exit surface 20b of the optical sheet 20. According to this, the light diffusion performance of the optical sheet 20 can be made higher.

(Modification 1)

In the above embodiment, an example in which the microlenses 22 are arranged so-called equilateral triangle lattice has been described. However, in the present invention, the arrangement of the microlenses 22 is not limited to the so-called equilateral triangle lattice arrangement. As shown in FIG. 13, the microlens 22 may be regularly and periodically arranged in each of the x direction and the y direction orthogonal to each other. As shown in FIG. 13, when the microlenses 22 are regularly and periodically arranged in each of the x and y directions orthogonal to each other, the pitches of the microlens arrays 21 are approximately equal in the x and y directions. can do. For this reason, the light-diffusion performance of the optical sheet 20 in the x direction and the light-diffusion performance of the optical sheet 20 in the y direction can be made substantially the same.

(Modification 2)

In the said embodiment, the example in which the light source device 30 has the some point light source 32 was demonstrated. However, in the present invention, the kind of the light source provided in the light source device 30 is not limited to the point light source. For example, the light source device 30 may have a plurality of linear light sources 34 arranged in parallel, for example, as shown in FIGS. 14 and 15. The kind of linear light source 34 is not specifically limited. The linear light source 34 may be, for example, a Cold Cathode Fluorescent Lamp (CCFL) or the like.

(Modification 3)

In the said embodiment, the example in which the microlens array 21 which has the some microlens 22 formed in convex form in the light output surface 20b of the optical sheet 20 is formed was demonstrated. However, in the present invention, the microlens 22 may be concave. In addition, the microlens array 21 may be formed in the light incident surface 20a of the optical sheet 20. The micro lens array 21 may be formed on both the light exit surface 20b and the light incident surface 20a of the optical sheet 20.

Specifically, for example, as shown in FIG. 16, the microlens array 21 having the plurality of microlenses 25 formed in a concave shape is formed on the light incident surface 20a of the optical sheet 20. It may be.

(Other modifications)

At least one of the optical sheet 20 and the light diffusion sheet 10 may be disposed in plural. That is, the number of arrangement | positioning of each of the optical sheet 20 and the light-diffusion sheet 10 is not limited to one sheet.

The micro lens array 21 may be covered with a light transmitting member. That is, the micro lens array 21 may be formed at the interface between the optical sheet 20 and the light transmitting member.

Additional optical elements may be disposed between the optical sheet 20 and the light source device 30, or between the optical sheet 20 and the light diffusion sheet 10. Specifically, for example, an additional light diffusion sheet may be disposed between the optical sheet 20 and the light source device 30.

The micro lens array 21 may be formed on the surface of another optical element. For example, it may be formed on the surface of the light transmissive substrate 33 shown in FIG. 1 or the like.

At least one surface of the optical sheet 20 can also be subjected to mat processing. Moreover, the sticking prevention layer which disperse | distributed the bead particle in the binder can also be formed in at least one surface of the optical sheet 20. FIG. That is, the surface roughness of at least one surface of the optical sheet 20 can also be roughened. By doing in this way, sticking to the translucent board | substrate 33 etc. of the optical sheet 20 can be suppressed.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated further more concretely based on an Example. However, the following examples are merely illustrative. This invention is not limited at all by the following example.

(Example 1)

First, a roughly hemispherical microlens 22 having a diameter of 9.4 μm by roll pressing a polycarbonate film (made by Daijin Kasei Co., Ltd., product name: Panlite 1225LL) having a length of 10 cm, a width of 10 cm, and a thickness of 200 μm. The optical sheet 20 formed in the equilateral triangular grating pattern of 9.9 micrometers of pitch shown in FIG. The microlens 22 had a share of 81.8%.

A light-diffusion sheet (manufactured by Kimoto, product number: 100DX2) having a bead formed with a light diffusion layer in which styrene beads were dispersed in an acrylic binder on a polyethylene terephthalate (PET) substrate having a thickness of 100 μm is called a light diffusion sheet (10). It was.

As the point light source 32, an LED light source (Toyo Kosei Co., Ltd. product number: E1S27 * M1F7-03) was used. Twenty-five LED light sources were placed on the circuit board at intervals of 1.9 cm in length and width, and wired to the circuit board. A white polyester film (Toray Co., Ltd. make, product number: Lumirror E6SL, thickness: 250 micrometers) is affixed on the part except an LED light source of a circuit board, and the inner surface of the casing 31, and further Asahi Kasei The light source device 30 of 100 mm square and 13.5 mm in height was produced by arrange | positioning the diffuser plate (grade MS, thickness 2mm) by Chemicals Corporation as the light transmissive substrate 33. As shown in FIG.

The light source device 30, the light diffusion sheet 10, and the optical sheet 20 produced as described above were laminated in the order shown in FIG. 1 to produce a light source unit 2.

About the obtained light source unit 2, brightness and brightness nonuniformity were measured with the following method. That is, the viewing angle characteristic measuring device (ELDIM Co., Ltd. product name, EZContrast 80) is fixed to 1.2 mm above the light exit surface of the light diffusion sheet 10 of the light source unit 2 disposed on the displaceable stage. The front luminance was measured at 5 mm intervals in each of the x and y directions by the viewing angle characteristic measuring device while moving the light source unit 2 in each of the x direction and the y direction for each stage. From the measurement result, the maximum value, minimum value, average value, and luminance nonuniformity of front brightness were computed. Here, the maximum value of the front luminance is the highest luminance among the measurements. The minimum value of the front luminance is the lowest luminance among the measurements. The average value is the average value of the measured front luminances. The luminance nonuniformity was computed by following formula (2). In addition, the target of the upper limit of the luminance nonuniformity at which the lamp image becomes invisible is about 2.5%.

In addition, by observing the obtained light source unit 2 visually, it was confirmed whether the rainbow color pattern was visually recognized.

(Example 2)

A light source unit 2 was fabricated in the same manner as in Example 1 except that the pitch of the microlens array 21 was 5 탆 and the diameter of the microlens 22 was 4.8 탆. Was performed. Further, the microlens 22 occupied in this embodiment was 80.3%.

(Example 3)

The light source unit 2 was produced in the same manner as in Example 1 except that the pitch of the microlens array 21 was 3 탆 and the diameter of the microlens 22 was 2.8 탆. Was performed. Incidentally, the microlens 22 had a 79% occupancy rate in this embodiment.

(Example 4)

A light source unit 2 was fabricated in the same manner as in Example 1 except that the pitch of the microlens array 21 was 1.8 µm and the diameter of the microlens 22 was 1.7 µm, and the luminance non-uniformity was measured and visually inspected. Was performed. In addition, the microlens 22 occupied occupied 80.9% of the present embodiment.

(Example 5)

A light source unit 2 was fabricated in the same manner as in Example 1 except that the pitch of the microlens array 21 was 1.5 µm and the diameter of the microlens 22 was 1.4 µm. Was performed. Incidentally, the microlens 22 had a 79% occupancy rate in this embodiment.

(Example 6)

Except that the microlenses 22 were arranged in a square lattice pattern as shown in Fig. 13, the light source unit 2 was produced in the same manner as in Example 1, and the luminance unevenness was measured and the visual inspection was performed.

(Example 7)

A light source unit 2 was fabricated in the same manner as in Example 2 except that the microlenses 22 were arranged in a square lattice pattern as shown in FIG. 13, and luminance unevenness was measured and visual inspection was performed.

(Example 8)

As the light diffusion sheet 10, except that the sheet having the microlens array 11 shown in Figs. 2 and 3 was used, the light source unit 2 was produced in the same manner as in the first embodiment, and the luminance unevenness was measured and The visual inspection was done. In the present Example, the microlens 12 was made into substantially hemispherical shape with a diameter of 9.4 micrometers, and the pitch of the microlens array 11 was 9.9 micrometers.

(Example 9)

The light source unit 2 was produced similarly to Example 8 except having set the pitch of the microlens array 21 to 5 micrometers, and the diameter to 4.8 micrometers, and the luminance nonuniformity was measured and visually examined.

(Example 10)

The light source unit 2 was produced similarly to Example 8 except having set the pitch of the microlens array 21 to 3 micrometers, and the diameter to 2.8 micrometers, and the luminance nonuniformity was measured and visually examined.

(Example 11)

It is assumed that the light source device 30 has the linear light source 34 shown in FIG. 14, and the optical source unit 20 has the dimensions of 30 cm and 40 cm, except that the light source unit ( 2) was produced and the measurement of the luminance nonuniformity and the visual inspection were performed. Specifically, in the present embodiment, a liquid crystal television (trade name: AQUOS LC-20S1 manufactured by Sharp Co., Ltd.) was disassembled to extract a backlight, and the backlight was used as the light source device 30. The dimensions of the light source device 30 were 395 mm in width, 285 mm in length, and 17.8 mm in thickness.

(Example 12)

The light source unit 2 was produced similarly to Example 11 except having set the pitch of the microlens array 21 to 5 micrometers, and the diameter to 4.8 micrometers, and the luminance nonuniformity was measured and visually examined.

(Example 13)

A light source unit 2 was produced in the same manner as in Example 2 except that the pitch of the microlens array 21 was 5 탆 and the diameter was 4.4 탆, and the occupancy rate of the microlenses 22 was 70%. The measurement of nonuniformity and visual inspection were done.

(Example 14)

A light source unit 2 was produced in the same manner as in Example 2 except that the pitch of the microlens array 21 was 5 탆 and the diameter was 4.1 탆, and the share of the microlenses 22 was 60%. The measurement of nonuniformity and visual inspection were done.

(Example 15)

A light source unit 2 was produced in the same manner as in Example 2 except that the pitch of the microlens array 21 was 5 탆 and the diameter was 3.7 탆, and the occupancy rate of the microlens 22 was 50%. The measurement of nonuniformity and visual inspection were done.

(Comparative Example 1)

A light source unit 2 was produced in the same manner as in Example 1 except that the pitch of the microlens array was 21.2 µm and the diameter of the microlens was 20 µm, and luminance unevenness was measured and visual inspection was performed.

(Comparative Example 2)

A light source unit was produced in the same manner as in Example 1 except that only the light diffusion sheet 10 was disposed and the optical sheet 20 was not disposed, and the luminance nonuniformity was measured and the visual inspection was performed.

(Comparative Example 3)

A light source unit was produced in the same manner as in Example 1 except that only the optical sheet 20 was disposed and the light diffusion sheet 10 was not disposed, and luminance unevenness was measured and visual inspection was performed.

In Table 1 and Table 2, the measurement results and the test results of Examples 1 to 15 and Comparative Examples 1 to 3 are shown.

As shown in Table 1 and Table 2, in Examples 1 to 4 in which the pitch of the microlens array 21 was less than 10 m, low luminance unevenness of 3.8% or less was measured. In contrast, in Comparative Example 1, high luminance nonuniformity of 4.9% was measured. Moreover, the high luminance nonuniformity of 9.9% was measured also in the comparative example 2 which used only the light-diffusion sheet 10. FIG.

In addition, in the comparative example 3 using only the optical sheet 20, although the luminance nonuniformity was low as 4.0% as shown in Table 2, the rainbow-colored pattern was observed. In contrast, in Examples 1 to 4 in which the light diffusion sheet 10 was disposed together with the optical sheet 20, no rainbow-colored shape was observed even when the pitch of the microlens array 21 was small.

From this result, by providing the optical sheet 20 and the light diffusing sheet 10 having a pitch of the micro lens array 21 of less than 10 m, not only the luminance unevenness can be effectively reduced, but also the rainbow color pattern is not visually recognized. You can see what you can do.

Comparing the results of Examples 1 to 4, it can be seen that the luminance unevenness becomes smaller as the pitch of the micro lens array 21 becomes smaller. By setting the pitch of the micro lens array 21 to 5 mu m, a low luminance nonuniformity of 3.1% can be realized, and by setting the pitch of the micro lens array 21 to 3 mu m, a lower luminance nonuniformity of 2.7% can be realized. From this result, it is understood that the pitch of the microlens array 21 is preferably 5 µm or less, and more preferably 3 µm or less.

In Examples 8 to 10 using the microlens array 11 in the light diffusion sheet 10, an average brightness higher than those in Examples 1 to 3 using the bead type thing in the light diffusion sheet 10 was obtained. From this result, it turns out that it is preferable to make the light-diffusion sheet 10 have the microlens array 11.

As shown in Table 2, also in Example 11 and Example 12 which used the linear light source as a light source, the low luminance nonuniformity was measured similarly to Example 1 and Example 2. From this result, it turns out that the optical element 3 which concerns on this invention can be used suitably not only for a point light source but a linear light source.

As shown in Example 2 and Example 13-Example 15, it turns out that the luminance nonuniformity becomes small at the same time as the occupancy rate of the microlens 22 becomes large. It turns out that luminance nonuniformity can be made especially small by making the occupancy rate of the microlens 22 into 80% or more.

(Example 16)

Except having made the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 1, and the average brightness and the brightness nonuniformity were measured similarly to the said Example 1, The rainbow colored poet test was done. Moreover, the normal line direction (0 degree) when the light beam of wavelength 550nm is made to inject into the optical sheet 20 with the combination (beam sigma company make, polarization analyzer) of a beam light source and a Goniophotometer. The transmittance at and the transmittance of the first diffracted light were measured. The results are shown in Table 3 below.

(Example 17)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 18)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, the brightness nonuniformity, and the normal direction (0 degree | times) are similar to the said Example 16. ), And the transmittance of the first diffraction light (first diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 19)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 20)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 21)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 22)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

(Example 23)

Except having made into the conditions shown in following Table 3, the optical sheet 20 and the light source unit 2 were produced similarly to the said Example 16, and the average brightness, a brightness nonuniformity, and a normal direction (0 degree) similarly to the said Example 16 The transmittance at and the transmittance of the first-order diffracted light (first-order diffraction light transmittance) were measured, and a rainbow colored visual test was performed. The results are shown in Table 3 below.

As shown in Table 3, Examples 17, 19, 20, and 22 having a zero degree transmittance of 30% or less and a first diffraction light transmittance of 2% or more have a zero degree transmittance of less than 30% or a first order diffracted light. The luminance nonuniformity was especially small at 2.5% or less, and the average luminance was particularly high at 6200 cd / m 2 or more than Examples 16, 18, 21, and 23 having a transmittance of less than 2%. From this result, when 0 degree transmittance is 30% or less and 1st diffraction light transmittance is 2% or more, it turns out that high front brightness and a small brightness nonuniformity are compatible.

In addition, from the results shown in Table 3 above, in order to make both high front luminance and small luminance nonuniformity compatible, (the pitch of the micro lens array 21 and the aspect ratio of the micro lens 22) are the points A (1.0, 0.875) of FIG. ), Points B (1.0, 0.625), points C (1.5, 0.375), points D (2.0, 0.375), points E (2.0, 0.625), and points F (1.5, 0.875) formed in this order by connecting them in a straight line It can be seen that it is preferable to be located in the area X1. In addition, (the pitch of the micro lens array 21, the aspect ratio of the micro lens 22) is the point G (1.0, 0.75), the point H (1.5, 0.5), the point I (2.0, 0.5) and the point J of FIG. It can be seen that it is more preferable to position (1.5, 0.75) in the region X2 formed by connecting the straight lines in this order.

Claims (15)

An optical sheet having a light incident surface and a light exit surface,
An optical element comprising a light diffusion sheet disposed on the light exit surface side of the optical sheet to diffuse by refracting incident light,
A microlens array is formed on at least one of the light incident surface and the light emitting surface,
The microlens array is an optical element in which a plurality of microlenses formed in a convex shape or a concave shape is arranged periodically and in a matrix form at a pitch of less than 10 μm. The method of claim 1, wherein the micro lens is formed in a convex shape,
And the microlens array is formed on the light exit surface. The optical element according to claim 1 or 2, wherein the microlens array has a pitch of 5 µm or less. The optical element according to any one of claims 1 to 3, wherein the pitch of the micro lens array is 3 µm or less. The optical element according to any one of claims 1 to 4, wherein the light diffusion sheet has a micro lens array in which a plurality of micro lenses are arranged at a pitch of 10 m or more. The microlens of claim 1, wherein the microlenses of the optical sheet are approximately circular in plan view,
The diameter of the microlens of the said optical sheet in planar view is 50% or more of the pitch of the microlens array of the said optical sheet. The optical element according to claim 6, wherein the diameter of the microlenses of the optical sheet in plan view is 80% or more of the pitch of the microlens array of the optical sheet. The microlens according to any one of claims 1 to 7, wherein a share of the microlens on the surface of the light incidence surface and the light emission surface on the side where the microlens array is formed is 80% or more,
In the coordinate system shown in FIG. 17 in which the pitch (μm) of the microlens array is the X axis, and the aspect ratio of the microlens obtained by dividing the height of the microlens by the diameter of the microlens is the Y axis, (the microlens The pitch of the array, the aspect ratio of the microlens) is point A (1.0, 0.875), point B (1.0, 0.625), point C (1.5, 0.375), point D (2.0, 0.375), point E (2.0, 0.625) And an optical element positioned in a region formed by connecting points F (1.5, 0.875) in a straight line in this order. The coordinate system according to claim 8, wherein an aspect ratio of the microlens obtained by dividing the height of the microlens by the diameter of the microlens as the X-axis and the pitch (μm) of the microlens array is the X-axis. Where (the pitch of the micro lens array, the aspect ratio of the micro lens) is the point G (1.0, 0.75), point H (1.5, 0.5), point I (2.0, 0.5) and point J (1.5, 0.75) An optical element positioned in an area formed by connecting in a straight line in sequence. The microlens array of the optical sheet according to any one of claims 1 to 9, wherein the optical lens has a peak of transmitted light having a transmittance higher than the transmittance at a diffusion angle of 0 degrees at a diffusion angle other than 0 degrees. An optical element formed to have. The optical element according to any one of claims 1 to 10, wherein the plurality of micro lenses of the optical sheet are regularly and periodically arranged in both a first direction and a second direction orthogonal to the first direction. . The optical element according to any one of claims 1 to 10, wherein the plurality of micro lenses of the optical sheet are arranged so that a figure formed by connecting centers of adjacent micro lenses in a plan view becomes an equilateral triangle. The optical element according to any one of claims 1 to 12,
And a light source device arranged on the light incident surface side of the optical element to emit light toward the light incident surface. The light source unit according to claim 13, wherein said light source device has a plurality of point light sources. The light source unit according to claim 13 or 14,
And a liquid crystal display cell arranged on the light exit surface side of the light diffusion sheet.

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