TWI427330B - An optical element having a light source unit and a liquid crystal display device - Google Patents

Description

Optical element, light source unit having the same, and liquid crystal display device

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

Previously, it has been known that there is a so-called direct type backlight. In the direct type backlight, a plurality of light sources are arranged below the light exit surface. Therefore, on the light exit surface of the backlight, there is a tendency that the luminance directly above the light source is higher than other portions. That is, there is a tendency to easily visualize a so-called lamp image.

Conventionally, for example, Patent Documents 1 to 5 and the like have proposed various methods for eliminating the unevenness in brightness. For example, Patent Document 1 discloses a method of arranging a light diffusing plate using a light diffusing material on a light source.

Further, Patent Document 6 discloses an optical sheet having a microlens array having a microlens having a diameter of 10 μm or more and less than 100 μm. Patent Document 6 describes that the optical sheet can be made to have high luminance in the front direction and uniform brightness. Further, Patent Document 6 also discloses that when the diameter of the microlens is less than 10 μm, the influence of diffraction is increased, and the visual quality is lowered. Therefore, the diameter of the microlens is preferably 10 μm or more, especially Good is 20μm or more.

[Patent Document 1] Japanese Patent Laid-Open No. 54-155244

[Patent Document 2] Patent No. 2852824

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2000-338895

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2002-352611

[Patent Document 5] U.S. Patent No. 5,161,041

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2004-145329

When the light diffusing plate using the light diffusing material is disposed on the direct type backlight as disclosed in Patent Document 1, absorption of light due to the light diffusing material or light is directed in an unnecessary direction. diffusion. Therefore, for a light diffusing plate using a light diffusing material, light emission efficiency is low. Therefore, only the light diffusing plate using the light diffusing material is disposed on the backlight, and although unevenness in brightness can be eliminated, there is a problem that the utilization efficiency of light emitted from the backlight is lowered.

Further, in the methods disclosed in Patent Documents 2 to 5, it is possible to eliminate the luminance unevenness of the backlights having the linear light sources arranged in parallel with each other, but it is difficult to sufficiently eliminate the brightness of the backlight of the dot-shaped light source in a matrix form. The problem of both. In detail, although the luminance unevenness of the backlight in a specific direction can be eliminated, there is a problem that it is difficult to sufficiently eliminate the luminance unevenness of the backlight in the direction perpendicular to the specific direction.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical element having high light emission efficiency, and further capable of eliminating a matrix in which a backlight of a dot-shaped light source is arranged in two orthogonal directions. Uneven brightness.

The optical element of the present invention includes an optical sheet having a light incident surface and a light exit surface, and a light diffusing sheet disposed on the light exit surface side of the optical sheet and diffused by refracting the incident light. A microlens array is formed on at least one of the light incident surface and the light exit surface. In the microlens array, a plurality of microlens systems formed in a convex shape or a concave shape are periodically arranged in a matrix shape with a distance of less than 10 μm.

In a specific aspect of the invention, the microlenses are formed in a convex shape, and the microlens array is formed on the light exit surface.

In the present invention, the distance between the microlens arrays is preferably 5 μm or less, more preferably 3 μm or less.

In another specific aspect of the invention, the light diffusing sheet has a microlens array in which a plurality of microlenses are arranged at a distance of 10 μm or more.

In another specific aspect of the invention, the microlens of the optical sheet is slightly rounded in plan view, and the diameter of the microlens of the optical sheet in plan view is more than 50% of the distance between the microlens arrays of the optical sheets. Preferably, it is more than 80%.

In still another specific aspect of the present invention, the occupation ratio of the microlens on the side of the light incident surface and the light exit surface on which the microlens array is formed is 80% or more, and the distance between the microlens arrays is (μm). 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 is set to the Y axis, (the distance between the microlens arrays, the aspect ratio of the microlens) ) is located in a straight line with 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) Connected in the formed area in this order.

In still another specific aspect of the present invention, the aspect ratio of the microlens obtained by dividing the distance between the microlens arrays (μm) as the X axis and dividing the height of the microlens by the diameter of the microlens is set to the Y axis. In the coordinate system shown in Fig. 17, (the distance between the microlens arrays, the aspect ratio of the microlens) is located at a point G (1.0, 0.75), a point H (1.5, 0.5), a point I (2.0, 0.5) and Point J (1.5, 0.75) is connected in the area formed in this order.

In still another specific aspect of the present invention, the microlens array is formed in such a manner that the optical sheet has a transmittance at a diffusion angle other than 0 degrees and a transmittance higher than a transmittance of a diffusion angle of 0 degrees. The peak.

In still another specific aspect of the present invention, the plurality of microlenses are regularly and periodically arranged in the first direction and the second direction orthogonal to the first direction.

In still another specific aspect of the present invention, the plurality of microlenses of the optical sheet are arranged in a plan view such that the pattern formed by the centers of the adjacent microlenses is an equilateral triangle.

The light source unit of the present invention includes the optical element of the present invention described above 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 also be a plurality of point light sources.

A liquid crystal display device of the present invention includes the light source unit of the present invention and a liquid crystal display unit disposed on a light emitting surface side of the light diffusion sheet.

[Effects of the Invention]

According to the invention, the optical sheet has a microlens array having a pitch of less than 10 μm, and the light diffusion sheet which is refracted by the incident light is disposed on the light exit surface side of the optical sheet, thereby improving the light. The emission efficiency is also eliminated, and it is also possible to eliminate the luminance unevenness in the two directions orthogonal to the backlight of the dot-shaped light source arranged in a matrix.

Hereinafter, a liquid crystal display device 1 shown in Fig. 1 will be described as an example of a preferred embodiment of the present invention. However, the liquid crystal display device 1 is merely illustrative, and the present 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 unit 40, a pair of polarizing plates 41a and 41b, and a light source unit 2. The liquid crystal display unit 40 is disposed between the pair of polarizing plates 41a and 41b. The polarizing plate 41a and the polarizing plate 41b are arranged such that the polarization directions are orthogonal to each other.

The light source unit 2 includes a light source device 30 and an optical element 3.

In the present invention, the light source device 30 is not particularly limited. The light source device 30 may have a plurality of point light sources such as LEDs (Light Emitting Diodes). Further, the light source device 30 may be a linear light source such as a plurality of cold cathode tubes.

In the present 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. A recess 31a is formed in the outer casing 31. A plurality of point light sources 32 are disposed in the recess 31a. As shown in FIG. 6, a plurality of point light sources 32 are arranged periodically and in a matrix. In addition, illustration of the transparent substrate 33 is abbreviate|omitted by FIG.

The recess 31a of the outer casing 31 is covered by the transparent substrate 33. The light of the point light source 32 is emitted from the light-transmitting substrate 33.

Further, the light-transmitting substrate 33 may be, for example, a diffusion plate having a function of diffusing light. Further, a light diffusion plate may be further disposed on the light-transmitting substrate 33.

As shown in FIG. 1, the optical element 3 is disposed on the light emitting surface 30a side of the light source device 30. The optical element 3 includes a light transmissive optical sheet 20 and a light transmissive light diffusing sheet 10. The optical sheet 20 is disposed above the light exit surface 30a of the light source device 30.

The light diffusion sheet 10 is disposed on the light emitting 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 is diffused by refracting incident light incident from the side of the optical sheet 20.

In the present invention, the light-diffusing sheet is not particularly limited as long as it is refracted by the incident light. In the present embodiment, a case where the light diffusion sheet 10 has a microlens array will be described as an example. However, the light diffusion sheet 10 may be, for example, a bead type light diffusion sheet, a ruthenium sheet, a reflective polarizing function sheet, or the like.

Further, in the present embodiment, an example in which one light diffusion sheet 10 is disposed will be described, but a plurality of light diffusion sheets 10 may be disposed. When a plurality of light diffusion sheets 10 are disposed, a plurality of light diffusion sheets of the same type may be disposed, and 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 exit surface 10b. The light diffusion sheet 10 includes a microlens array 11 formed on the light exit surface 10b. As shown in FIG. 2, the microlens array 11 includes a plurality of microlenses 12 arranged periodically and in a matrix.

The arrangement of the plurality of microlenses 12 is not particularly limited. The plurality of microlenses 12 are, for example, regularly and periodically arranged in the first direction and in the second direction orthogonal to the first direction. That is, the plurality of microlenses 12 can be arranged in a so-called square lattice pattern. Further, as shown in FIG. 2, the plurality of microlenses 12 can be formed such that the pattern formed by the centers of the adjacent microlenses 12 is a triangle (preferably an equilateral triangle) in a plan view, that is, a so-called triangular lattice pattern. (preferably a regular triangular lattice pattern) and arranged.

Specifically, in the present embodiment, as shown in FIG. 2, the pattern T _{1 in which} the centers C ₁ to C _{3 of} the adjacent microlenses 12 are connected is an equilateral triangle, that is, a so-called equilateral triangle lattice. Arranged in a pattern. As described above, by arranging the plurality of microlenses 12 in a so-called equilateral triangular lattice pattern in plan view, the number of microlenses 12 arranged per unit area can be increased. That is, the occupancy rate of the microlens 12 can be increased. Therefore, a higher diffusion function can be achieved.

As shown in FIGS. 2 and 3, in the present embodiment, the shape of the microlens 12 is hemispherical. However, in the present invention, the shape of the microlens 12 is not particularly limited. The microlens 12 may be formed in a shape such as a dome shape, a cone shape, a truncated cone shape, a pyramid shape, or a truncated cone shape.

The plurality of microlenses 12 are arranged at a distance of 10 μm or more. It is preferable that the distance between the microlens arrays 11 is, for example, 20 μm or more.

In the present specification, the "microlens array pitch" means the shortest distance among the centers of adjacent microlenses. Specifically, in the case shown in FIG. 2, the plurality of microlenses 12 are arranged such that the pattern formed by the centers of the adjacent microlenses 12 is an equilateral triangle. Therefore, the distance P ₁ shown in FIG. Equal to the pitch P ₂ . Therefore, the distance P between the microlens arrays 11 in the present 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 in accordance with the distance P between the microlens arrays 11 and the occupancy ratio. For example, the diameter D _{1 of the} microlens 12 may be about 15 to 100 μm.

The material of the light diffusion sheet 10 is not particularly limited. The light diffusion sheet 10 can be formed by, for example, a synthetic resin. Specific examples of the synthetic resin include polyethylene terephthalate and the like.

Further, the average thickness of the light diffusion sheet 10 is also not particularly limited. It is preferable that the average thickness of the light-diffusing sheet 10 is, for example, about 50 to 400 μm.

As shown in FIG. 1, the optical sheet 20 is disposed on the light source device 30. However, the optical sheet 20 is not necessarily disposed directly above the light source device 30. Other optical elements may be disposed between the light source device 30 and the optical sheet 20. For example, a light diffusion plate, a cymbal sheet or the like may be disposed between the optical sheet 20 and the light source device 30. Further, an air layer may be interposed between the light source device 30 and the optical sheet 20.

The optical sheet 20 includes a light incident surface 20a and a light exit surface 20b. The light incident surface 20a faces the light source device 30. The light exit surface 20b faces the light diffusion sheet 10.

As shown in FIGS. 4 and 5, the optical sheet 20 includes a microlens array 21.

The microlens array 21 is formed on at least one of the light incident surface 20a and the light exit surface 20b. Specifically, in the present embodiment, as shown in FIGS. 1 and 5, the microlens array 21 is formed on the light emitting surface 20b of the optical sheet 20.

The microlens array 21 includes a plurality of microlenses 22. Each of the plurality of microlenses 22 is formed in a convex shape or a concave shape. In the present embodiment, the microlens array 21 includes a plurality of microlenses 22 formed in a convex shape. More specifically, in the present embodiment, the microlens 22 is formed in a hemispherical shape. However, the shape of the microlens 22 in the present invention is not limited thereto. The microlens 22 may be formed in a shape such as an elliptical shape, a conical shape, a truncated cone shape, a pyramid shape, or a truncated cone shape.

The plurality of microlenses 22 are arranged periodically and in a matrix. The plurality of microlenses 22 may be arranged, for example, regularly and periodically in the first direction and the second direction orthogonal to the first direction. That is, the plurality of microlenses 22 may be arranged, for example, in a so-called square lattice pattern. Further, as shown in FIG. 4, the plurality of microlenses 22 can be arranged such that the patterns T _{2 obtained} by connecting the centers C ₄ to C _{6 of} the adjacent microlenses 22 are triangular. That is, the plurality of microlenses 22 can be arranged in a so-called triangular lattice pattern. Preferably, the plurality of microlenses 22 are arranged in an equilateral triangle lattice pattern in which the pattern T ₂ is an equilateral triangle among the triangular lattice patterns.

In the present embodiment, the distance P (= P ₃ = P ₂ ) between the microlens arrays 21 is set to be less than 10 μm. The distance between the microlens arrays 21 is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2.5 μm or less.

The distance P between the microlens arrays 21 is preferably 0.3 μm or more, more preferably 0.7 μm or more. When the distance P between the microlens arrays 21 becomes small, the formation of the microlens array 21 tends to be difficult.

In the present embodiment, since the distance P between the microlens arrays 21 is set to less than 10 μm, diffracted light is generated in the microlens array 21. When the light is incident on the microlens array 21 from the normal direction, the diffracted light is enhanced at an angle 0 satisfying the following formula (1).

P‧sinθ=nλ ......(1)

among them,

P: the distance between the microlens arrays 21,

n: natural number,

λ: the wavelength of the light incident on the microlens array 21.

In the present embodiment, the diameter D _{2 of the} microlens 22 is not particularly limited. Among them, it is preferable that the diameter D ₂ of the microlens 22 is 50% or more, more preferably 80% or more, of the distance P between the microlens arrays 21. By setting the diameter D _{2 of the} microlens 22 to be larger than the distance P between the microlens arrays 21, the microlens 22 in the region where the microlens 22 is formed in the light exit surface 20b of the optical sheet 20 can be formed. The occupancy rate is relatively high. The occupation ratio of the microlens 22 is preferably 20% or more, more preferably 50% or more.

In the present specification, the occupation ratio of the microlens refers to the ratio of the area of the microlens to the area of the surface on which the microlens is formed in plan view. Specifically, as shown in FIG. 4, the area of the microlens 22 located in the equilateral triangle T ₂ is relative to the area of the equilateral triangle T ₂ surrounded by the centers C ₄ to C _{6 of} the microlens 22 . proportion.

The material of the optical sheet 20 is not particularly limited as long as it has light transmissivity. The optical sheet 20 can be formed by, for example, a translucent synthetic resin. Specific examples of the synthetic resin include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. Energy-hardening resin, etc. Specific examples of the energy curing resin include an ultraviolet curable resin and an electron beam curable resin. Among these, an energy-hardening resin represented by an ultraviolet curable resin or an electron beam curable resin is particularly preferable. The microlens array 21 can be formed relatively easily by using an energy hardening type resin.

Furthermore, the optical sheet 20 may be integrally formed, or a plurality of optical members may be bonded together. Specifically, the optical sheet 20 is attached to an optical film such as a polyethylene terephthalate film or a polyethylene naphthalate film or a polycarbonate film, and is attached with an ultraviolet curing resin or the like. The resulting microlens is obtained.

Further, the optical sheet 20 may contain at least one of various fillers, plasticizers, stabilizers, anti-deterioration agents, and dispersing agents.

The thickness of the optical sheet 20 is not particularly limited. The average thickness of the optical sheet 20 can be, for example, 10 μm or more and 3000 μm or less. 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, more preferably 50 μm or more and 250 μm or less.

On the other hand, in consideration of the mechanical strength of the optical sheet 20, the average thickness of the optical sheet 20 is preferably in the range of 1000 μm or more and 2500 μm or less, and more preferably in the range of 1200 μm or more and 2000 μm or less.

When the thickness of the optical sheet 20 is too thin, the shape of the optical sheet 20 changes due to heat or the like of the light source device 30 or the like. On the other hand, when the thickness of the optical sheet 20 is too thick, the light transmittance of the optical sheet 20 tends to decrease.

The method of producing the optical sheet 20 is also not particularly limited. The optical sheet 20 can be manufactured by various known manufacturing methods. As a method of producing the optical sheet 20, for example, a method of forming a synthetic resin layer on a molding die, and then peeling the synthetic resin layer from the molding die, and subjecting the sheet-formed resin to hot pressing using a molding die is exemplified. Method, etc.

As described above, the optical element 3 of the present embodiment includes the microlens array 21 having a pitch P of less than 10 μm and the light diffusion sheet 10 which is diffused by refracting incident light. Therefore, for example, it is possible to achieve higher light emission efficiency and higher light diffusibility than in the case of using a light diffusing plate that diffuses light by refracting the optical element 3 instead of the optical element 3.

As described in Patent Document 6, the distance between the microlens arrays 21 is usually set to 10 μm or more from the viewpoint of suppressing the color dispersion to be small. However, when the distance between the microlens arrays 21 is set to 10 μm or more, it is difficult to sufficiently diffuse light.

On the other hand, in the present embodiment, the light diffusion sheet 10 that diffuses incident light by refracting it is combined with the microlens array 21 having a high light diffusion function. Therefore, while achieving high light diffusibility in the microlens array 21, the color dispersion generated in the microlens array 21 can be effectively eliminated in the light diffusion sheet 10. Therefore, while achieving high light diffusibility, it is possible to effectively suppress the rainbow pattern caused by the color dispersion.

Further, a plurality of minute microlenses 22 are arranged in a matrix in the microlens array 21. Therefore, the light is dispersed not only in one direction but also in two directions orthogonal to each other. Therefore, by using the optical element 3, it is possible to eliminate the luminance unevenness in the two orthogonal directions of the backlight in which the dot-shaped light source is arranged in a matrix.

Hereinafter, the effects of the present embodiment will be described in further detail.

Fig. 7 is a graph showing the relationship between the diffusion angle of the outgoing light and the transmittance in the microlens array having a pitch of 50 μm. In the case of a microlens array having a pitch of 50 μm, diffracted light is not substantially generated in the microlens array. Therefore, as shown in Fig. 7, in the case of a microlens array having a pitch of 50 μm, the transmitted light is concentrated at a position where the diffusion angle is 0 degree. Therefore, for example, in the case where the microlens array having a pitch of 50 μm is disposed on the light source device 30, the brightness of the position corresponding to the point light source 32 is higher than that of the other portions. As a result, a relatively large brightness unevenness is visually observed.

In addition, the graphs shown in FIG. 7 to FIG. 12 are graphs when the wavelength of incident light is 550 nm.

Fig. 8 is a graph showing the relationship between the diffusion angle of the outgoing light and the transmittance in the microlens array 21 having a pitch of 9.9 μm. In the case of the microlens array 21 having a pitch of 9.9 μm, diffracted light is generated in the microlens array 21. Therefore, in a region where the diffusion angle is -30 to 30 degrees, a plurality of peaks of transmitted light caused by the diffracted light are generated. Therefore, compared with the case where the distance between the microlens arrays 21 is 50 μm, the transmittance of the diffusion angle of 0 degrees becomes low, and the transmittance of the diffusion angles of -30 to 0 degrees and 0 to 30 degrees becomes high. Therefore, it is possible to reduce unevenness in brightness.

Further, even when the distance between the microlens arrays is 10 μm or more, diffracted light is sometimes generated. However, as shown in Fig. 12, when the distance between the microlens arrays is 10 μm or more, the obtained diffusion angle is very small. Therefore, when the distance between the microlens arrays is 10 μm or more, the light cannot be sufficiently diffused. As a result, it is difficult to sufficiently suppress luminance unevenness.

As shown in FIG. 12, when the distance between the microlens arrays 21 is less than 10 μm, the diffusion angle is remarkably increased. Therefore, a large diffusion angle can be obtained by setting the distance between the microlens arrays 21 to less than 10 μm. As a result, uneven brightness can be effectively reduced.

9 to 11 are graphs showing the relationship between the diffusion angle of the outgoing light and the transmittance in the microlens array 21 having the distance between the microlens arrays 21 of 5 μm, 3 μm, and 1.8 μm, respectively. Specifically, as shown in FIG. 8, when the distance between the microlens arrays 21 is 9.9 μm, although a plurality of peaks of transmitted light appear, the peaks of the plurality of transmitted lights are close to each other. As shown in FIG. 9 to FIG. 11, when the distance between the microlens arrays 21 is 5 μm or less, the distance between the peaks of the adjacent transmitted light becomes wider, and most of the transmitted light is except for the direct upper side of the point light source 32. The peak is scattered.

For example, in the case where no diffracted light is generated, the peak of the transmitted light exists at substantially the same interval from the interval of the point source 32. Therefore, the peaks of the adjacent transmitted light are relatively long. On the other hand, when the distance between the microlens arrays 21 is 5 μm or less, as described above, most of the peaks of the transmitted light are dispersed except for the direct upper side of the point light source 32. As a result, the distance between the peaks of the adjacent transmitted light is relatively short. Therefore, it is difficult to visually detect uneven brightness. Therefore, it is preferable that the distance between the microlens arrays 21 is 5 μm or less.

Further, as shown in Fig. 12, when the distance between the microlens arrays 21 is 3 μm, the diffusion angle suddenly increases sharply. Therefore, it is more preferable that the distance between the microlens arrays 21 is 3 μm or less.

From the viewpoint of not visually observing the point light source 32, it is preferable that the transmitted light intensity directly above the point light source 32 is small. In other words, it is preferred that the transmittance of the diffusion angle of 0 degrees is small.

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

Specifically, it is preferable that the ratio (occupation ratio) of the microlens 22 to the light exit surface 20b of the optical sheet 20 is large. More specifically, the occupation ratio of the microlens 22 in the region where the microlens array 21 is formed in the light exit surface 20b is preferably 20% or more, more preferably 50% or more. By providing in this manner, the amount of light that is transmitted through the optical sheet 20 without being diffused can be reduced, and the diffracted light can be increased.

Further, as shown in the present embodiment, when the shape of the microlens 22 is slightly circular in plan view, it is preferable that the diameter of the microlens 22 is 50% or more of the distance between the microlens arrays 21, and more preferably More than 80%.

From the viewpoint of increasing the occupation ratio of the microlenses 22, it is preferable that the microlenses 22 have a pattern in which the centers of the adjacent microlenses 22 are connected in a triangular shape in a plan view as shown in FIG. And arranged. Further, it is particularly preferable that the microlenses 22 are arranged such that the patterns formed by the centers of the adjacent microlenses 22 are equilateral triangles in plan view. This is because the occupation ratio of the microlens 22 can be maximized.

Moreover, from the viewpoint of reducing the transmittance of the diffusion angle of 0 degrees, the occupation ratio of the microlenses 12 in the light exit surface 20b is 80% or more, and the distance (μm) between the microlens arrays 11 is set to the X axis, and the micro In the coordinate system shown in FIG. 17 in which the aspect ratio of the microlens 12 obtained by dividing the height of the lens 12 by the diameter of the microlens 12 is set to the Y axis, it is preferable that (the distance between the microlens arrays and the aspect ratio of the microlens) ) is located in a straight line with 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) is connected in the formed region X1 in this order. Further, in the coordinate system shown in FIG. 17, it is more preferable that (the distance between the microlens arrays and the aspect ratio of the microlens) is located at a point G (1.0, 0.75), a point H (1.5, 0.5), Point 1 (2.0, 0.5) and point J (1.5, 0.75) are connected in the formed region X2 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 distance between the microlens arrays 21 is preferably 1.25 to 2.0 μm, more preferably 1.5 to 2.0 μm. According to this configuration, the transmittance at a diffusion angle of 0 degrees can be 30% or less, and the transmittance at a diffusion angle 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, as in the present embodiment, the light-diffusing sheet 10 preferably has a microlens array 11 having a microlens array 11 having a distance of 10 μm or more.

When a sheet having the microlens array 11 is used as the light diffusion sheet, it is possible to suppress a phenomenon in which, for example, in the case where a light diffusion sheet using a light diffusion material is used, light is diffused toward an unnecessary direction or Absorption of light due to light diffusing material. Therefore, it is possible to achieve higher light emission efficiency.

Further, in the present embodiment, the minimum function required for the light diffusion sheet 10 is only a function of eliminating the color dispersion generated in the optical sheet 20. Therefore, for example, the light diffusing sheet required for the light diffusing sheet 10 is relatively low in comparison with the light diffusing plate in the case where only the light diffusing plate that refracts light is diffused instead of the optical element 3 is disposed. Thus, for example, when the light diffusion sheet 10 is formed by using a light diffusion sheet having a light diffusion material, the concentration of the light diffusion material in the light diffusion sheet 10 can be lowered. Therefore, even in the case of using a light-diffusing sheet having a light-diffusing material, the light-diffusing sheet phase in the case where only the light-diffusing sheet which refracts light is diffused instead of the optical element 3 is disposed. In contrast, it is possible to suppress the diffusion of light toward the unnecessary direction of the light diffusion sheet 10 or light absorption. As a result, it is possible to achieve a higher light emission efficiency.

Preferably, the microlens 22 is formed in a convex shape, and the microlens array 21 is formed on the light exit surface 20b of the optical sheet 20. Thereby, the light diffusion performance of the optical sheet 20 can be further improved.

(Modification 1)

In the above embodiment, an example in which the microlenses 22 are arranged in a so-called equilateral triangular lattice has been described. However, in the present invention, the arrangement of the microlenses 22 is not limited to the so-called equilateral triangular lattice arrangement. As shown in FIG. 13, the microlenses 22 may be regularly and periodically arranged in the respective directions 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 the respective directions of the x direction and the y direction orthogonal to each other, the distance between the microlens array 21 in the x direction and the y direction can be made substantially the same. Therefore, the light diffusing performance of the optical sheet 20 in the x direction can be made substantially the same as the light diffusing performance of the optical sheet 20 in the y direction.

(Modification 2)

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

(Modification 3)

In the above embodiment, an example in which the microlens array 21 having a plurality of microlenses 22 formed in a convex shape is formed on the light exit surface 20b of the optical sheet 20 has been described. However, in the present invention, the microlens 22 may also be concave. Further, the microlens array 21 may be formed on the light incident surface 20a of the optical sheet 20. The microlens array 21 may also be formed on both sides of the light exit surface 20b and the light incident surface 20a of the optical sheet 20.

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

(Other variants)

At least one of the optical sheet 20 and the light diffusion sheet 10 may be provided with a plurality of sheets. In other words, the number of sheets of the optical sheet 20 and the light diffusion sheet 10 is not limited to one.

The microlens array 21 may also be covered with a light transmissive member. That is, the microlens array 21 may be formed on the interface between the optical sheet 20 and the light transmissive member.

Further 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 diffusing sheet 10. Specifically, for example, another light diffusion sheet may be disposed between the optical sheet 20 and the light source device 30.

The microlens array 21 can also be formed on the surface of other optical components. For example, it may be formed on the surface of the light-transmitting substrate 33 as shown in FIG.

The surface of at least one of the optical sheets 20 may be roughened. Further, an anti-adhesive layer in which the bead particles are dispersed in the binder may be formed on at least one surface of the optical sheet 20. That is, the surface roughness of the surface of at least one of the optical sheets 20 is roughened. Thereby, adhesion of the optical sheet 20 to the light-transmitting substrate 33 or the like can be suppressed.

Hereinafter, the present invention will be further specifically described based on examples. However, the following examples are merely illustrative. The invention is not limited by the following examples.

(Example 1)

First, by rolling a polycarbonate film (manufactured by Teijin Chemical Co., Ltd., product name: panlite 1225LL) having a length of 10 cm, a width of 10 cm, and a thickness of 200 μm, the following optical sheet 20 is obtained, that is, the optical sheet 20 is obtained. A substantially hemispherical microlens 22 having a diameter of 9.4 μm was formed by an equilateral triangle lattice pattern having a distance of 9.9 μm as shown in FIG. The occupation ratio of the microlens 22 was 81.8%.

A light diffusing sheet (product number: 100DX2 manufactured by Kimoto Co., Ltd.) is used as the light diffusing sheet 10, and the light diffusing sheet with the beads is a light diffusing film in which styrene beads are dispersed in an acrylic adhesive. The layer was formed on a polyethylene terephthalate (PET) substrate having a thickness of 100 μm.

As the point light source 32, an LED light source (product number: E1S27*M1F7-03 manufactured by Toyota Synthetic Co., Ltd.) was used. The 25 LED light sources were arranged on the circuit board at intervals of 1.9 cm in the vertical and horizontal directions, and the circuit board was wired. A white polyester film (manufactured by Toray Co., Ltd., product number: lumiler E6SL, thickness: 250 μm) was attached to the circuit board to remove the LED light source and the inner side of the outer casing 31, and further spread by Asahi Kasei Chemical Co., Ltd. A plate (grade MS, thickness: 2 mm) was disposed as the light-transmitting substrate 33, whereby a light source device 30 having a square of 100 mm square and a height of 13.5 mm was produced.

The light source unit 30, the light diffusion sheet 10, and the optical sheet 20 produced in the above manner are laminated in the order shown in Fig. 1 to fabricate the light source unit 2.

With respect to the obtained light source unit 2, luminance and luminance unevenness were measured in the following manner. In other words, the viewing angle characteristic measuring device (product name EZContrast 80 manufactured by ELDIM Co., Ltd.) is fixed at 1.2 mm above the light emitting surface of the light diffusing sheet 10 of the light source unit 2 disposed on the displaceable platform. While the light source unit 2 and the stage are moved in the respective directions of the x direction and the y direction, the front side luminance is measured every 5 mm in each of the x direction and the y direction by the viewing angle characteristic measuring apparatus. Based on the measurement results, the maximum value, the minimum value, the average value, and the brightness unevenness of the front luminance were calculated. Here, the maximum value of the front luminance is the highest luminance in the measurement. The minimum value of the front brightness is the lowest brightness in the measurement. The average value is the average of the front luminances measured. The luminance unevenness is calculated by the following equation (2). Furthermore, the standard for the upper limit of the luminance unevenness of the lamp image cannot be visually observed to be about 2.5%.

(uneven brightness) = ((maximum front brightness) - (minimum front brightness)) / (average of front brightness) (2)

Further, by observing the obtained light source unit 2, it is confirmed whether or not the rainbow pattern is visually observed.

(Example 2)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that the distance between the microlens arrays 21 was 5 μm and the diameter of the microlenses 22 was 4.8 μm, and measurement of brightness unevenness and visual inspection were performed. Furthermore, the occupation ratio of the microlens 22 in this embodiment is 80.3%.

(Example 3)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that the distance between the microlens arrays 21 was 3 μm and the diameter of the microlenses 22 was 2.8 μm, and measurement of brightness unevenness and visual inspection were performed. Furthermore, the occupation ratio of the microlens 22 in this embodiment is 79%.

(Example 4)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that the distance between the microlens arrays 21 was 1.8 μm and the diameter of the microlenses 22 was 1.7 μm, and measurement of brightness unevenness and visual inspection were performed. Furthermore, the occupation ratio of the microlens 22 in this embodiment is 80.9%.

(Example 5)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that the distance between the microlens arrays 21 was 1.5 μm and the diameter of the microlenses 22 was 1.4 μm, and measurement of brightness unevenness and visual inspection were performed. Furthermore, the occupation ratio of the microlens 22 in this embodiment is 79%.

(Example 6)

The light source unit 2 was fabricated in the same manner as in the above-described first embodiment except that the microlenses 22 were arranged in a square lattice pattern as shown in Fig. 13, and measurement of brightness unevenness and visual inspection were performed.

(Example 7)

The light source unit 2 was fabricated in the same manner as in the above-described second embodiment except that the microlenses 22 were arranged in a square lattice pattern as shown in Fig. 13, and measurement of brightness unevenness and visual inspection were performed.

(Example 8)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that a sheet having the microlens array 11 shown in Figs. 2 and 3 was used as the light diffusion sheet 10, and measurement of unevenness in brightness and visual inspection were performed. In the present embodiment, the microlenses 12 are formed in a substantially hemispherical shape having a diameter of 9.4 μm, and the distance between the microlens arrays 11 is set to 9.9 μm.

(Example 9)

The light source unit 2 was produced in the same manner as in the above-described Example 8 except that the distance between the microlens arrays 21 was 5 μm and the diameter was 4.8 μm, and measurement of brightness unevenness and visual inspection were performed.

(Embodiment 10)

The light source unit 2 was produced in the same manner as in the above-described Example 8 except that the distance between the microlens arrays 21 was 3 μm and the diameter was 2.8 μm, and measurement of brightness unevenness and visual inspection were performed.

(Example 11)

The light source unit 2 was fabricated in the same manner as in the above-described first embodiment except that the light source device 30 was provided with the linear light source 34 shown in FIG. 14 and the size of the optical sheet 20 was 30 cm in length and 40 cm in width. Uneven measurement and visual inspection. Specifically, in the present embodiment, the liquid crystal television (product name: AQUOS LC-20S1) manufactured by Sharp Corporation is decomposed, the backlight is taken out, and the backlight is used as the light source device 30. The size of the light source device 30 is 395 mm in width, 285 mm in length, and 17.8 mm in thickness.

(Embodiment 12)

The light source unit 2 was produced in the same manner as in the above-described Example 11 except that the distance between the microlens arrays 21 was 5 μm and the diameter was 4.8 μm, and measurement of brightness unevenness and visual inspection were performed.

(Example 13)

The light source unit 2 was fabricated in the same manner as in the above-described second embodiment except that the distance between the microlens arrays 21 was 5 μm, the diameter was 4.4 μm, and the occupation ratio of the microlenses 22 was 70%. Uneven measurement and visual inspection.

(Example 14)

The light source unit 2 was fabricated in the same manner as in the above-described second embodiment except that the distance between the microlens arrays 21 was 5 μm, the diameter was 4.1 μm, and the occupation ratio of the microlenses 22 was 60%. Uneven measurement and visual inspection.

(Example 15)

The light source unit 2 was fabricated in the same manner as in the above-described second embodiment except that the distance between the microlens arrays 21 was 5 μm, the diameter was 3.7 μm, and the occupation ratio of the microlenses 22 was 50%. Uneven measurement and visual inspection.

(Comparative Example 1)

The light source unit 2 was produced in the same manner as in the above-described first embodiment except that the distance between the microlens arrays was 21.2 μm and the diameter of the microlens was 20 μm, and measurement of brightness unevenness and visual inspection were performed.

(Comparative Example 2)

The light source unit 2 was fabricated in the same manner as in the above-described first embodiment except that only the light diffusion sheet 10 was disposed without the optical sheet 20, and measurement of brightness unevenness and visual inspection were performed.

(Comparative Example 3)

The light source unit 2 was fabricated in the same manner as in the above-described first embodiment except that only the optical sheet 20 was disposed without the light diffusion sheet 10, and measurement of brightness unevenness and visual inspection were performed.

Tables 1 and 2 below show the measurement results and inspection results of Examples 1 to 15 and Comparative Examples 1 to 3.

As shown in Tables 1 and 2, in Examples 1 to 4 in which the microlens array 21 was less than 10 μm apart, a lower luminance unevenness of 3.8% or less was measured. On the other hand, in Comparative Example 1, a high brightness unevenness of 4.9% was measured. Further, in Comparative Example 2 in which only the light-diffusing sheet 10 was used, a high luminance unevenness of 9.9% was also measured.

Further, in Comparative Example 3 in which only the optical sheet 20 was used, as shown in Table 2, the luminance unevenness was as low as 4.0%, but a rainbow pattern was observed. On the other hand, in the first to fourth embodiments in which the optical sheet 20 and the light diffusion sheet 10 were disposed, the rainbow pattern was not observed even when the distance between the microlens arrays 21 was reduced.

According to the results, it is understood that by providing the optical sheet 20 and the light diffusion sheet 10 which are less than 10 μm apart between the microlens arrays 21, unevenness in brightness can be effectively reduced, and rainbow patterns are not visually observed.

Comparing the results of Examples 1 to 4, it is understood that the unevenness in brightness is reduced as the distance between the microlens arrays 21 is reduced. By setting the distance between the microlens arrays 21 to 5 μm, it is possible to achieve a low luminance unevenness of 3.1%, and by setting the distance between the microlens arrays 21 to 3 μm, it is possible to achieve a luminance unevenness of 2.7%. From this result, it is understood that the distance between the microlens arrays 21 is preferably 5 μm or less, more preferably 3 μm or less.

In Examples 8 to 10 in which the light-diffusing sheet 10 having the microlens array 11 was used, it was possible to obtain higher average brightness than Examples 1 to 3 using the bead type light-diffusing sheet 10. From this result, it is understood that the light diffusion sheet 10 is preferably provided with the microlens array 11.

As shown in Table 2, in the eleventh embodiment and the twelfth embodiment using the linear light source as the light source, as in the first embodiment and the second embodiment, the luminance unevenness was measured. From this result, it is understood that the optical element 3 of the present invention can be used not only in a point light source but also in a linear light source.

As shown in the second embodiment and the third to the fifteenth embodiments, the occupation ratio of the microlens 22 is increased, and the luminance unevenness is reduced. It is understood that the luminance unevenness can be made particularly small by setting the occupation ratio of the microlens 22 to 80% or more.

(Embodiment 16)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 1, except that the conditions shown in the following Table 3 were measured, and the average luminance and luminance unevenness were measured in the same manner as in the above-described Example 1, and performed. Visual inspection of rainbow patterns. Further, by the combination of the beam light source and the light distribution measuring device (manufactured by Sigma Optical Co., Ltd., a polarization analyzer), the transmittance in the normal direction (0 degree) when the light beam having a wavelength of 550 nm is incident on the optical sheet 20 is measured. And the transmittance of the diffracted light once. The results are shown in Table 3 below.

(Example 17)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Embodiment 18)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Embodiment 19)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Embodiment 20)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Example 21)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Example 22)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

(Example 23)

The optical sheet 20 and the light source unit 2 were produced in the same manner as in the above-described Example 16, except that the conditions shown in the following Table 3 were used, and the average brightness and brightness unevenness were measured in the same manner as in the above Example 16. The transmittance in the normal direction (0 degree) and the transmittance of the first diffracted light (1 diffracted light transmittance), and a visual inspection of the rainbow pattern was performed. The results are shown in Table 3 below.

As shown in the above Table 3, in Examples 17, 19, 20, and 22 in which the 0-degree transmittance was 30% or less and the primary diffracted light transmittance was 2% or more, the transmittance was less than 30% or 1 in comparison with the 0-degree transmittance. In Examples 16, 18, 21, and 23 in which the sub-diffracted light transmittance was less than 2%, the luminance unevenness was particularly small, 2.5% or less, and the average luminance was particularly high, and was 6200 cd/m ² or more. From this result, it is understood that when the transmittance at 0 degree is 30% or less and the transmittance of the primary diffracted light is 2% or more, high front luminance and small luminance unevenness can be simultaneously achieved.

Further, according to the results shown in the above Table 3, in order to simultaneously achieve higher front luminance and less luminance unevenness, it is preferable that (the distance between the microlens arrays 21 and the aspect ratio of the microlens 22) is located in the figure. 17 is a straight line with 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) is connected in the formed region X1 in this order. Further, it is better understood that (the distance between the microlens arrays 21 and the aspect ratio of the microlenses 22) is located in a straight line in Fig. 17 at points G (1.0, 0.75), points H (1.5, 0.5), and points I (2.0). , 0.5) and point J (1.5, 0.75) are connected in the formed region X2 in this order.

1. . . Liquid crystal display device

2. . . Light source unit

3. . . Optical element

10. . . Light diffuser

10a. . . Light incident surface

10b. . . Light exit surface

11. . . Microlens array

12. . . Microlens

20. . . Optical sheet

20a. . . Light incident surface

20b. . . Light exit surface

twenty one. . . Microlens array

twenty two. . . Microlens

25. . . Microlens

30. . . Light source device

30a. . . Light exit surface

31. . . shell

31a. . . Concave

32. . . Point light source

33. . . Light transmissive substrate

34. . . Linear light source

40. . . Liquid crystal display unit

41a. . . Polarizer

41b. . . Polarizer

Fig. 1 is a schematic cross-sectional view showing a liquid crystal display device which is an example of a preferred embodiment of the present invention.

Figure 2 is a plan view showing a portion of a light diffusing sheet.

Figure 3 is a view of the arrow III-III in Figure 2.

Figure 4 is a plan view showing a portion of an optical sheet.

Figure 5 is a view of the V-V arrow in Figure 4.

Figure 6 is a plan view of a light source device. Here, the illustration of the light-transmitting substrate 33 is omitted.

Fig. 7 is a graph showing the relationship between the diffusion angle and the transmittance when the distance between the microlens arrays is 50 μm.

Fig. 8 is a graph showing the relationship between the diffusion angle and the transmittance when the distance between the microlens arrays is 9.9 μm.

Fig. 9 is a graph showing the relationship between the diffusion angle and the transmittance when the distance between the microlens arrays is 5 μm.

Fig. 10 is a graph showing the relationship between the diffusion angle and the transmittance when the distance between the microlens arrays is 3 μm.

Fig. 11 is a graph showing the relationship between the diffusion angle and the transmittance when the distance between the microlens arrays is 1.8 μm.

Fig. 12 is a graph showing the relationship between the distance between the microlens arrays and the diffusion angle when n = 2 and λ = 550 nm in the formula (1).

Fig. 13 is a plan view showing a part of an optical sheet in Modification 1.

Fig. 14 is a plan view showing a light source device in a second modification.

Figure 15 is a view showing the XV-XV arrow in Figure 14.

Figure 16 is a cross-sectional view showing a part of an optical sheet in Modification 3.

Figure 17 is a graph showing the relationship between the distance between the microlens arrays and the aspect ratio of the microlenses.

1. . . Liquid crystal display device

2. . . Light source unit

3. . . Optical element

10. . . Light diffuser

20. . . Optical sheet

20a. . . Light incident surface

20b. . . Light exit surface

twenty one. . . Microlens array

twenty two. . . Microlens

30. . . Light source device

30a. . . Light exit surface

31. . . shell

31a. . . Concave

32. . . Point light source

33. . . Light transmissive substrate

40. . . Liquid crystal display unit

41a. . . Polarizer

41b. . . Polarizer

Claims (15)

An optical element comprising: an optical sheet having a light incident surface and a light exit surface; and a light diffusing sheet disposed on the light exit surface side of the optical sheet to refract incident light to thereby diffuse And forming a microlens array on at least one of the light incident surface and the light emitting surface, wherein the plurality of microlenses formed in a convex or concave shape in the microlens array are periodically arranged at intervals of less than 10 μm It is a matrix. The optical element according to claim 1, wherein the microlens is formed in a convex shape, and the microlens array is formed on the light exit surface. The optical element of claim 1 or 2, wherein the distance between the microlens arrays is 5 μm or less. The optical element of claim 1 or 2, wherein the distance between the microlens arrays is 3 μm or less. The optical element according to claim 1 or 2, wherein the light-diffusing sheet has a microlens array in which a plurality of microlenses are arranged at a distance of 10 μm or more. The optical element of claim 1 or 2, wherein the microlens of the optical sheet is slightly circular in plan view, and the diameter of the microlens of the optical sheet in plan view is 50 of the distance between the microlens arrays of the optical sheet. %the above. An optical component of claim 6, wherein The diameter of the microlens of the optical sheet in plan view is 80% or more of the distance between the microlens arrays of the optical sheets. The optical element according to claim 1 or 2, wherein a ratio of the light incident surface to the surface of the light exit surface on which the microlens array is formed is 80% or more, and the microlens array is used. a pitch (μm) is an 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 of the coordinate system shown in FIG. 17 (the distance between the microlens arrays, The aspect ratio of the microlens is located at 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) In this order, the areas formed by the straight lines are connected. The optical element according to claim 8, wherein the aspect ratio of the microlens obtained by dividing the height of the microlens by the diameter of the microlens by the distance (μm) between the microlens arrays is the Y axis In the coordinate system shown in Fig. 17, (the distance between the above microlens arrays, the aspect ratio of the above microlens) is located at a point G (1.0, 0.75), a point H (1.5, 0.5), a point I (2.0, 0.5), and a point J. (1.5, 0.75) In this order, the areas formed by the straight lines are connected. The optical element according to claim 1 or 2, wherein the microlens array of the optical sheet is formed such that the optical sheet has a transmittance at a diffusion angle other than 0 degrees and a transmittance higher than a transmittance of a diffusion angle of 0 degrees. Peak. An optical component as claimed in claim 1 or 2, wherein The plurality of microlenses of the optical sheet are regularly and periodically arranged in the first direction and in the second direction orthogonal to the first direction. The optical element of claim 1 or 2, wherein the plurality of microlenses of the optical sheet are arranged in a plan view in such a manner that the pattern formed by the centers of adjacent microlenses is an equilateral triangle. A light source unit comprising: the optical element according to any one of claims 1 to 12; and a light source device disposed on a light incident surface side of the optical element to emit light toward the light incident surface. The light source unit of claim 13, wherein the light source device has a plurality of point light sources. A liquid crystal display device comprising: a light source unit according to claim 13 or 14; and a liquid crystal display unit disposed on a light exit surface side of the light diffusion sheet.