JP2011133822A - Optical sheet, surface light source device, and transmission type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet which can exhibit an excellent optical function and can be stably produced. <P>SOLUTION: The optical sheet 40 includes: a sheet-shaped body part 45; a plurality of first unit shape elements 50 arranged on one side 46 of the body part; a plurality of second unit shape elements 55 arranged on one side of the body part and extending in parallel with one direction on the sheet face of the body part; and a connection part 42 of covering at least a part of the connection part between one first unit shape element and one second unit shape element connected to the one first unit shape element from the one direction. Each of the plurality of first unit shape elements is projected from one side of the body part to a position higher than each of the plurality of second unit shape elements and the connection part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical sheet that changes the traveling direction of light, and more particularly to an optical sheet that can exhibit an excellent optical function and can be stably manufactured. The present invention also relates to a surface light source device and a transmissive display device including such an optical sheet. Furthermore, the present invention relates to a method for manufacturing such an optical sheet and a mold for manufacturing.

  A surface light source device used for a transmissive display device includes a light source and a large number of optical sheets (optical films) for changing the traveling direction of light from the light source. Among many optical sheets, a light diffusing sheet that normally diffuses light from the light source to hide the image of the light source (makes it inconspicuous), and narrows the traveling direction of the light to the front direction to improve the luminance in the front direction. A light collecting sheet. And by combining the light-diffusion sheet | seat in which light-diffusion performance was adjusted, and the condensing sheet | seat in which condensing performance was adjusted suitably, while having a desired front direction brightness | luminance, desired A transmissive display device having a viewing angle and in which an image of a light source is not conspicuous has been manufactured.

  As the light diffusion sheet, an optical sheet containing light diffusing particles for isotropically diffusing light, an optical sheet having an uneven surface (mat surface), and the like are widely used.

  On the other hand, as the condensing sheet, an optical sheet formed by arranging linearly extending unit shape elements (unit optical elements) in a direction orthogonal to the longitudinal direction (so-called linear arrangement) is widely used. Such a condensing sheet not only has a function of intensively improving the brightness in the front direction, but also a function of reducing the in-plane variation of the brightness in the front direction caused by the configuration of the light source and making the image of the light source inconspicuous, and It also has a function of smoothly changing the angular distribution of luminance around the front direction. However, the optical action of such a light collecting sheet exerts a strong directivity and is mainly exerted on a light component traveling in the arrangement direction of the unit shape elements. For this reason, usually, by incorporating two condensing sheets into the surface light source device so that the arrangement directions of the unit shape elements are orthogonal to each other, two orthogonal directions on the display surface (typically the vertical direction and The luminance distribution is adjusted along the horizontal direction.

  Recently, an optical sheet having unit shape elements (unit optical elements) scattered on a plane, that is, a two-dimensional array of unit shape elements, for example, a fly eye lens sheet having a fly-eye lens (amber eye lens) is also attracting attention. (For example, Patent Document 1). According to such an optical sheet, in principle, without using a plurality of optical sheets, an optical sheet such as a condensing action or a diffusing action with respect to light components traveling in various directions by a single optical sheet. Thus, the optical characteristics in both the vertical direction and the horizontal direction of the display surface can be adjusted. As a result, it can be expected that the number of optical sheets incorporated in the surface light source device is reduced. A reduction in the number of optical sheets used is very preferable in that it directly leads to a reduction in the manufacturing cost of the surface light source device.

  However, neither the light collection function nor the light diffusion function of the fly-eye lens sheet actually used has reached a sufficient level. As a result, two or more fly-eye lens sheets are incorporated in the surface light source device, and the manufacturing cost of the surface light source device cannot be reduced.

  The optical sheet is usually made from a radiation curable resin (typically a UV curable resin) by molding using a mold. When molding an optical sheet in which unit shape elements are two-dimensionally arranged, in the molding die, the concave portions corresponding to the unit shape elements have a closed shape in the entire circumferential direction. Therefore, when the radiation curable resin is filled, air often does not escape from the recess and air frequently remains between the mold and the radiation curable resin. In this case, bubbles are formed in the molded unit shape element, or a concave portion is formed on the surface of the molded unit shape element, so that the optical sheet cannot exhibit the planned optical function. . Somewhere, such an inconvenience may even be visually recognized by an observer when the optical sheet is incorporated into a display device.

JP 2006-301582 A

  The present invention has been made in consideration of such points, and an object thereof is to provide an optical sheet that can exhibit an excellent optical function and can be stably manufactured. Another object of the present invention is to provide a surface light source device and a transmissive display device including such an optical sheet. Furthermore, this invention aims at providing the method for manufacturing such an optical sheet, and the type | mold for manufacturing.

  A mold for producing a fly-eye lens sheet in which unit shape elements are arranged in two different directions is more expensive than a mold for producing an optical sheet in which unit shape elements are linearly arranged. turn into. In connection with this, the manufacturing cost of the fly-eye lens sheet in which unit shape elements are arranged in two different directions is also increased. Therefore, an optical sheet that can exhibit an excellent optical function is manufactured without significantly increasing the manufacturing cost as compared with a fly-eye lens sheet in which conventional unit shape elements are arranged in two different directions. If you can, it is very convenient.

An optical sheet according to an aspect of the present invention is provided.
A sheet-like body,
A plurality of first unit shape elements arranged on one surface of the main body;
A plurality of second unit-shaped elements arranged on the one surface of the main body, each extending in parallel with one direction on the sheet surface of the main body;
One first unit shape element, and one second unit shape element connected to the one first unit shape element from the one direction, and a connection portion that covers at least a part of the connection portion, and
Each of the plurality of first unit shape elements protrudes from the one surface of the main body portion to a position higher than each of the plurality of second unit shape elements and the connection portion.

  In the optical sheet according to one aspect of the present invention, the connection portion may extend in the one direction on the one second unit shape element from the at least part of the connection portion.

  Moreover, in the optical sheet according to one aspect of the present invention, the connection point between the first unit shape element and the second unit shape element that is at least partially covered by the connection portion is the second unit shape element, Only the connection location connected to the first unit shape element from one side in the one direction may be used.

Alternatively, in the optical sheet according to one aspect of the present invention,
A first connecting portion that covers at least a part of a connection portion between the first unit shape element and the second unit shape element connected to the first unit shape element from one side in the one direction;
And a second connecting portion that covers at least a part of a connection portion between the first unit shape element and the second unit shape element connected to the first unit shape element from the other side in the one direction. And
The second unit shape element provided with the first connection portion and the second unit shape element provided with the second connection portion are different positions in the arrangement direction of the second unit shape elements. May be arranged.

  Furthermore, in the optical sheet according to one aspect of the present invention, the first unit shape elements are arranged with a gap on the one surface of the main body portion, and the second unit shape elements are arranged on the main body portion. You may arrange | position between the said 1st unit shape elements on said one surface.

  Furthermore, in the optical sheet according to an aspect of the present invention, the second unit shape element may be provided in a region on the one surface where the first unit shape element is not provided.

  Furthermore, in the optical sheet according to one aspect of the present invention, a partial region of the one surface of the main body is covered with the first unit shape element, and the one of the one surfaces of the main body is All other areas other than the partial area may be covered with the second unit shape element.

  Furthermore, in the optical sheet according to one aspect of the present invention, the first unit shape element is a part of an ellipse or a circle in a cross section that is parallel to a normal direction to the sheet surface of the main body and orthogonal to the one direction. It may include a shape corresponding to a part of.

  Furthermore, in the optical sheet according to an aspect of the present invention, the second unit shape element has a triangular shape in a cross section that is parallel to a normal direction to the sheet surface of the main body and orthogonal to the one direction. Also good.

  Furthermore, in the optical sheet according to one aspect of the present invention, the first unit shape element may have a shape corresponding to a part of a spheroid or a shape corresponding to a part of a sphere.

  Furthermore, in the optical sheet according to an aspect of the present invention, there is one first unit shape element and another one of the first unit shape elements that is disposed closest to the first unit shape element along the sheet surface of the main body. An average minimum interval of the first unit shape elements that represents an average of the separation distance along the sheet surface of the main body portion between the first unit shape elements is in the one direction on the sheet surface of the main body portion. You may make it more than the arrangement pitch of the said 2nd unit shape element to the orthogonal direction. In such an optical sheet according to the present invention, the plurality of first unit shape elements are arranged at a constant pitch along a first direction on the sheet surface of the main body, and the sheet surface of the main body. The first direction is also arranged along the second direction, and the first direction is orthogonal to the one direction and is inclined by 60 ° with respect to the second direction. May be. Alternatively, in such an optical sheet according to the present invention, the first unit shape element may be randomly arranged on the one surface of the main body.

  A surface light source device according to an aspect of the present invention includes a light source and any one of the above-described optical sheets according to an aspect of the present invention that receives light from the light source.

  The surface light source device according to an aspect of the present invention may further include a polarization separation film disposed on the light output side of the optical sheet.

  A first display device according to the present invention includes a transmissive display unit and any one of the above-described surface light source devices according to an aspect of the present invention, which is disposed to face the transmissive display unit.

The method for producing the first optical sheet according to the present invention comprises:
A method for producing any of the optical sheets according to one aspect of the present invention described above by molding using a mold,
Supplying a flowable material into the mold;
Curing the material supplied in the mold in the mold;
Removing the cured material from the mold,
In the step of supplying the material having fluidity, the material is filled in the mold along a direction corresponding to the one direction of the optical sheet manufactured by the mold.

The method for producing the second optical sheet according to the present invention comprises:
The optical sheet according to one aspect of the present invention described above, in which only the connection portion where the second unit shape element connects to the first unit shape element from one side in the one direction is covered by the connection portion, is applied using a mold. A method of manufacturing by mold,
Supplying a flowable material into the mold;
Curing the material supplied in the mold in the mold;
Removing the cured material from the mold,
In the step of supplying the material having fluidity, the material is placed in the mold in a direction and direction corresponding to the direction from the other side to the one side in the one direction of the optical sheet produced by the mold. It will be filled.

  In the first or second optical sheet manufacturing method according to the present invention, in the step of removing the material from the mold, the cured material is gradually separated from the mold along the one direction. Also good.

  Further, in the method of manufacturing an optical sheet according to the present invention, the mold is formed as a roll mold having a cylindrical mold surface, the step of supplying the material, the step of curing the material, and the step of removing the material May be carried out sequentially on the mold surface while the mold rotates once around its central axis.

The first mold according to the present invention is:
A mold for producing any of the optical sheets according to one aspect of the present invention described above by molding,
It is configured as a roll mold with a cylindrical mold surface,
A plurality of recesses corresponding to the first unit shape elements, grooves corresponding to the second unit shape elements,
A notch portion formed at a connection portion between the recess and the groove and corresponding to the connection portion is formed on the mold surface;
The groove extends circumferentially around the central axis of the mold surface, or spirally extends around the central axis of the mold surface.

The second mold according to the present invention is:
Of the optical sheet according to one aspect of the present invention described above, a mold for producing an optical sheet having a first connection portion and a second connection portion by molding,
It is configured as a roll mold with a cylindrical mold surface,
A plurality of recesses corresponding to the first unit shape element, a plurality of spiral grooves corresponding to the second unit shape element, and one groove included in the plurality of grooves and a connection portion between the recesses are formed. And a second notch corresponding to the second connection portion formed at a connection portion between the first recess and the recess and the other groove included in the plurality of grooves. Are formed on the mold surface.

The first mold manufacturing method according to the present invention comprises:
A method of manufacturing the first mold of the present invention described above,
Forming the recess in a cylindrical mold base;
Forming the groove and the notch in the mold substrate in which the recess is formed by cutting the mold substrate, and in the cutting step, The notch is formed together with the groove by cutting with a cutting means that keeps the cut amount constant.

The second mold manufacturing method according to the present invention comprises:
A method of manufacturing the second mold of the present invention described above,
Forming the recess in a cylindrical mold base;
Forming the groove and the notch in the mold substrate in which the recess is formed by cutting the mold substrate, and in the cutting step, By the cutting with a cutting means that keeps the cutting amount constant, the notch is formed together with the groove,
In the cutting step, a plurality of parallel grooves are formed, the cutting direction when forming one of the plurality of grooves, and the formation of another of the plurality of grooves. The direction of cutting is opposite.

  According to the present invention, an excellent optical function is exhibited by an optical sheet that can be manufactured stably.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a transmissive display device and a surface light source device, for explaining an embodiment according to the present invention. FIG. 2 is a partial perspective view showing an optical sheet incorporated in the surface light source device of FIG. FIG. 3 is a top view showing the optical sheet. FIG. 4 is a diagram for explaining the operation of the optical sheet, and is a cross-sectional view of the optical sheet along the line IV-IV in FIG. 3. FIG. 5 is a diagram for explaining the operation of the unit shape element included in the optical sheet in the cross section corresponding to FIG. 4. FIG. 6 is a schematic diagram for explaining an optical sheet manufacturing method and an optical sheet molding apparatus. FIG. 7A is a partial perspective view showing a mold surface of a molding die incorporated in the molding apparatus of FIG. FIG. 7B is a cross-sectional view of the mold along the line VII-VII in FIG. 7A. FIG. 8 is a view for explaining a method of molding the optical sheet, and is a cross-sectional view of the molding apparatus. FIG. 9A is a diagram for explaining a method of manufacturing the molding die of FIGS. 7A and 7B. FIG. 9B is a diagram for explaining a method of manufacturing the molding die of FIGS. 7A and 7B. FIG. 10A is a partial perspective view showing the mold being manufactured shown in FIG. 9A in the same field of view as FIG. 7A. 10B is a view showing the mold being manufactured shown in FIG. 9A in the same field of view as FIG. 7B, and is a cross-sectional view of the mold along the line XX in FIG. 10A. FIG. 11A is a partial perspective view showing the mold being manufactured shown in FIG. 9B in the same field of view as FIG. 7A. FIG. 11B is a view showing the mold being manufactured shown in FIG. 9B in the same field of view as FIG. 7B, and is a cross-sectional view of the mold along the line XI-XI in FIG. 11A. FIG. 12 is a diagram corresponding to FIG. 3 and illustrating a modified example of the optical sheet. FIG. 13 is a view corresponding to FIG. 7A and for explaining a modification of the molding die that can be used to manufacture the optical sheet of FIG. FIG. 14A is a diagram corresponding to FIG. 9B and is a diagram for explaining a method of manufacturing the molding die of FIG. 14B is a diagram corresponding to FIG. 9B and is a diagram for explaining a method of manufacturing the molding die of FIG. FIG. 15 is a cross-sectional view illustrating a modification of the second unit shape element included in the optical sheet. FIG. 16 is a diagram corresponding to FIG. 1 and is a diagram for explaining the configuration of the transmissive display device according to the example.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

  1 to 11B are diagrams for explaining an embodiment according to the present invention. 1 is a cross-sectional view showing a schematic configuration of a transmissive display device and a surface light source device, FIG. 2 is a perspective view of the optical sheet, FIG. 3 is a top view of the optical sheet, and FIGS. 5 is a cross-sectional view along the normal direction to the sheet surface of the optical sheet.

  The transmissive display device 10 shown in FIG. 1 includes a transmissive display unit 15, a surface light source device 20 that is disposed on the back side of the transmissive display unit 15 and illuminates the transmissive display unit 15 in a planar shape from the back side, It has. The transmissive display unit 15 is composed of, for example, a liquid crystal display panel (LCD panel). In this case, the transmissive display device 10 functions as a liquid crystal display device. Here, the LCD panel includes a pair of support plates made of glass or the like, a liquid crystal disposed between the support plates, and an electrode for controlling the orientation of liquid crystal molecules by an electric field for each region forming one pixel. It is a panel. The orientation of the liquid crystal between the support plates can be changed for each region where one pixel is formed. As a result, the liquid crystal display panel 15 functions as a shutter for forming an image by transmitting or blocking the surface light having a uniform in-plane luminance distribution from the surface light source device 20 for each pixel.

  On the other hand, as shown in FIG. 1, the surface light source device 20 includes a light source 25, an optical sheet 40 that transmits light from the light source 25 with its traveling direction deflected, and polarized light disposed on the light output side of the optical sheet 40. And a separation film 35. A light diffusion sheet 38 that diffuses light is provided on the light incident side of the optical sheet 40. The surface light source device 20 may be configured in various forms such as an edge light (side light) type, but is configured as a direct type backlight unit in the present embodiment. Therefore, the light source 25 is disposed so as to face the optical sheet 40 on the light incident side of the optical sheet 40. The light source 25 is covered from the back side by a box-shaped reflecting plate 28 having an opening (window) formed on the optical sheet 40 side.

  Note that the “light exit side” refers to the downstream side in the traveling direction of light from the light source 25 toward the observer through the optical sheet 40 or the like without turning back the traveling direction (observer side, in FIGS. 1, 4, and 5). Is the upstream side in the traveling direction of light from the light source 25 to the observer through the optical sheet 40 and the like without being folded back.

  Further, in the present case, the terms “sheet”, “film”, and “plate” are not distinguished from each other based only on the difference in names. Therefore, for example, a “sheet” is a concept including a member that can also be called a film or a plate.

  Furthermore, in the present case, the “sheet surface (film surface, plate surface)” is a surface that coincides with the planar direction of the target sheet-like member when the target sheet-like member is viewed as a whole and globally ( In the case of an uneven surface, it is also equivalent to the envelope surface). In the present embodiment, the sheet surface of the optical sheet 40, the film surface of the polarization separation film 35, the sheet surface of the light diffusion sheet 38, the light emitting surface of the surface light source device 15, and the display surface of the transmissive display device 10. Are parallel to each other. Further, the “front direction” is a normal direction nd (see FIG. 3) with respect to the sheet surface of the optical sheet 40, and also coincides with the normal direction of the light emitting surface of the surface light source device 20.

  The light source 25 can be configured in various modes such as a fluorescent lamp such as a linear cold cathode tube, a spot LED (light emitting diode), an incandescent lamp, and a planar EL (electroluminescent element). In the present embodiment, as shown in FIG. 1 and FIG. 4 (two-dot chain line), the light source 25 has a plurality of cold-cathode tubes extending linearly. The reflecting plate 28 is a member for directing light from the light source 25 toward the optical sheet 40, and at least the inner surface of the reflecting plate 28 is made of a material having a high reflectivity such as metal.

  The polarized light separating film 35 is a sheet-like member having a function of transmitting a specific polarized component of incident light based on the polarization state of the incident light, and reflecting other polarized components to return to the light source side again. is there. “DBEF” (registered trademark) available from 3M USA can be used as the polarized light separating film 35 that can help improve the luminance. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS” available from Shinwha Intertek, Korea, a wire good polarizer, or the like can be used as the polarization separation film 35.

  The light diffusing sheet 38 diffuses incident light, preferably isotropically diffuses incident light, alleviates luminance unevenness (also referred to as a light source image or tube unevenness) according to the configuration of the light source 25, and distributes in-plane luminance. It is a sheet-like member for equalizing. As such a light diffusion sheet 38, a sheet including a base portion and light diffusing particles dispersed in the base portion and having a light diffusion function may be used. As an example, by configuring the light diffusing particles from a material having a high reflectance, or by configuring the light diffusing particles from a material having a refractive index different from the material forming the base, A light diffusion function can be imparted.

  Next, the optical sheet 40 will be described.

  As shown in FIGS. 2 to 5, the optical sheet 40 includes a sheet-like main body 45 and a large number of first unit shape elements (first elements) two-dimensionally arranged on one surface 46 of the sheet-like main body 45. 1 unit optical element, point unit optical element) 50 and a number of second unit shape elements (second unit optical element, linear unit optical element) arranged on one surface 46 of the sheet-like main body 45 55 and a plurality of connection portions 42 arranged so as to cover a connection portion between the first unit shape element and the second unit shape element. As shown in FIG. 2, the first unit shape elements 50 are arranged with a gap on one surface 46 of the main body 45. On the other hand, the second unit shape element 55 is disposed between the first unit shape elements 50 on the one surface 46 of the main body 45.

  In the present embodiment, the entire region of the one surface 46 of the main body 45 is covered with the first unit shape element 50 and the second unit shape element 55. More specifically, a part of one surface 46 of the main body 45 is covered with the first unit shape element 50, and other than the one part of the one surface 46 of the main body 45. Is covered with the second unit shape element 55. According to such an arrangement of the first unit shape element 50 and the second unit shape element 55, the light incident on the optical sheet 40 is emitted from the light exit surface of the optical sheet 40 without being optically affected. In other words, so-called “elemental omission” can be prevented.

  In the present embodiment, as shown in FIGS. 3 and 4, the main body 45 has a smooth surface that forms the light incident side surface 41 of the optical sheet 40 as the other surface 47 facing the one surface 46. Have. As used herein, “smoothing” means smoothing in an optical sense. That is, here, it means the degree that a certain percentage of visible light is refracted while satisfying Snell's law on the light incident side surface 41 (the other surface 47 of the main body 45) of the optical sheet 40. Yes. Therefore, for example, if the ten-point average roughness Rz (JISB0601) of the other surface 47 of the main body 45 (the light incident side surface 41 of the optical sheet 40) is equal to or shorter than the shortest visible light wavelength (0.38 μm), It is sufficiently smooth.

  Next, the first unit shape element 50 will be described. A large number of first unit shape elements 50 are scattered on one surface 46 of the main body portion 45 to constitute a fly-eye lens. A fly-eye lens is also called a fly-eye lens, and is a lens member having a large number of unit lenses arranged at regular intervals or irregular (random) intervals in different directions on a plane. It means that.

  In the present embodiment, as shown in FIG. 3, the arrangement of a large number of first unit shape elements 50 in the plane is a congruent equivalent to the projection onto the surface 46 of each first unit shape element 50. The circles are arranged on one surface 46 of the main body 45 with an arrangement in which the circles are slightly separated from the structure in which the planes are closely packed. That is, one first unit shape element 50 is surrounded from the periphery by six first unit shape elements 50 that are arranged symmetrically six times circumferentially at equal intervals. This corresponds to an arrangement in which each unit element is slightly separated from a hexagonal close-packed structure in a so-called crystal. In other words, the multiple first unit-shaped elements 50 are arranged at two common different pitches on one surface 46 of the main body 45 inclined at an angle of 60 ° with a common constant pitch. That is, as shown in FIG. 3, a large number of first unit shape elements 50 are arranged at a constant pitch along the first direction d1 on the sheet surface of the main body 45 and the sheet surface of the main body 45. The first direction d1 and the second direction d2 are inclined at an angle of 60 ° with respect to each other along the second direction d2. In other words, the arrangement centers 51 of the three closest first unit shape elements 50 on one surface 46 of the main body 45 are respectively placed on the vertices of an equilateral triangle on the one surface 46 of the main body 45. A large number of first unit shape elements 50 are arranged so as to be positioned.

  As described above, the light source 25 is composed of a plurality of cold cathode tubes extending linearly. On the other hand, the fly-eye lens composed of the first unit shape element 50 has a unit lens (first unit shape element 50) that is circularly symmetric and isotropic within the surface 46, and therefore is on the sheet surface of the optical sheet 40. In the plane along the arbitrary direction, the traveling direction of the light can be similarly changed. Therefore, even if the arrangement direction of the first unit shape elements 50 is set without considering the longitudinal direction da (see FIG. 3) of the elongated light source 25 and the arrangement direction of the light source 25 (direction orthogonal to da), the light source 25 It is possible to similarly and isotropically change the traveling direction of light within a plane along the arrangement direction. Thereby, in-plane variation (tube unevenness) of luminance caused by the arrangement configuration of the light sources 25 is reduced, and an image of the light source (light image) that becomes visible according to the arrangement configuration of the light sources 25 is inconspicuous. Can be made.

  Further, in the present embodiment, as shown in FIG. 4, each first unit shape element 50 is a circle protruding to the light exit side in a cross section parallel to the normal direction nd to the sheet surface of the optical sheet 40. Or a part corresponding to a part of an ellipse protruding to the light output side. That is, each first unit shape element 50 is formed as a unit lens. In the case where the cross-sectional shape of the first unit shape element 50 corresponds to a part of an ellipse, either the long axis or the short axis of the cross-sectional elliptical shape is the optical sheet 40 from the viewpoint of intensively improving the luminance in the front direction. It is preferable to extend in parallel with the normal direction (that is, the front direction) nd to the sheet surface.

  As a specific example of the first unit shape element 50, the arrangement pitch P <b> 1 (see FIG. 3) of the first unit shape elements 50 on the one surface 46 of the main body 45 can be 10 μm to 400 μm. Further, the width W1 (see FIG. 3) of the bottom surface of the first unit shape element 50 along the arrangement direction of the first unit shape elements 50 on the one surface 46 of the main body 45 may be 10 μm to 200 μm. it can. Furthermore, the protrusion height H1 (see FIG. 5) of the first unit shape element 50 from the one surface 46 of the main body 45 along the normal direction nd to the sheet surface of the optical sheet 40 is set to 5 μm to 100 μm. Can do. In the illustrated example, the multiple first unit shape elements 50 are configured identically.

  Next, the second unit shape element 55 will be described. The multiple second unit elements 55 constitute a linear array prism portion. In the present embodiment, each second unit shape element 55 extends linearly with a constant cross-sectional shape along one direction on one surface 46 of the main body 45. In the present embodiment, as shown in FIG. 3, a large number of second unit shape elements 55 are arranged side by side in the other direction on one surface 46 perpendicular to the longitudinal direction (the one direction) without any gap. Has been. In the illustrated example, the second unit shape elements 55 are arranged in one arrangement direction (first direction) of the first unit shape elements 50 when observed from the normal direction nd to the sheet surface of the optical sheet 40. d1 and the light source 25 extend in a straight line parallel to the longitudinal direction da.

  In the present embodiment, as shown in FIG. 4 and FIG. 5, a cross section that is parallel to the arrangement direction of the second unit shape elements 55 and is also parallel to the normal direction nd to the sheet surface of the optical sheet 40 ( Each second unit shape element 55 has a triangular shape protruding toward the light output side. That is, each second unit shape element 55 is formed as a so-called unit prism. And from the viewpoint of intensively improving the brightness in the front direction, the cross-sectional shape is particularly an isosceles triangle shape, and the apex angle located between the equilateral sides extends from one surface 46 of the main body 45 to the light output side. It is preferable that each 2nd unit shape element 55 is comprised so that it may protrude.

  As a specific example of the second unit shape element 55, the width W2 of the bottom surface of the second unit shape element 55 along the arrangement direction of the second unit shape elements 55 on one surface 46 of the main body 45 (see FIG. 4). ) Can be 1 μm to 200 μm. Further, the protrusion height H2 (see FIG. 5) of the second unit shape element 55 from the one surface 46 of the main body 45 along the normal direction nd to the sheet surface of the optical sheet 40 is 0.5 μm to 50 μm. can do. In the illustrated example, the multiple second unit shape elements 55 are configured identically. Furthermore, when the cross-sectional shape of the second unit shape element 55 is an isosceles triangle, the angle of the apex angle that is located between the equilateral sides and protrudes toward the light output side from the viewpoint of intensively improving the luminance in the front direction. θ (see FIG. 5) is preferably 80 ° or more and 120 ° or less, and more preferably 90 °.

  The “triangular shape” in this specification is not only a triangular shape in a strict sense, but also an optical function similar to a triangular shape including limitations in manufacturing technology, errors during molding, and the like. Examples include a substantially triangular shape that can be expected, that is, a shape in which a vertex of the triangle is rounded, a shape in which the head of the triangle is cut (a truncated triangle), and the like. Similarly, terms used in the present specification to specify other shapes and geometric conditions, for example, terms such as “circle”, “ellipse”, “parallel”, “orthogonal”, etc. are also bound to the strict meaning. Without being interpreted, the interpretation should include an error to the extent that a similar optical function can be expected.

  Further, as shown in FIGS. 2, 4, and 5, the protrusion height of the second unit shape element 55 from one surface 46 of the main body 45 along the normal direction nd to the sheet surface of the optical sheet 40. H2 is lower than the protrusion height H1 of the first unit shape element 50 from one surface 46 of the main body 45 along the normal direction nd to the sheet surface of the optical sheet 40. That is, on one surface 46 of the main body 45, each second unit shape element 55 is divided by the first unit shape element 50, and two adjacent second unit shape elements 55 along the longitudinal direction of the second unit shape element 55. It extends between the first unit shape elements 50. Specifically, in expectation of the effects described later, the protrusion height H2 of the second unit shape element 55 is 9/10 or less of the protrusion height H1 of the first unit shape element 50, and is 1/10 or more. It is preferable that

  In general, when the top part of the unit prism that extends linearly while maintaining a triangular cross section comes into contact with another sheet-like member, various problems such as the top part of the unit prism being scraped and interference fringes being easily visible. Occurs. On the other hand, as in the present embodiment, the protrusion height H2 of the second unit shape element 55 made of a linear prism is higher than the protrusion height H1 of the first unit shape element 50 constituting the fly-eye lens. When it is low, such a problem can be solved.

  Next, the connection part 42 is demonstrated. As shown in FIGS. 2 and 3, each connecting portion 42 includes one first unit shape element 50 and the longitudinal direction of the second unit shape element with respect to the one first unit shape element 50 (the one direction). ) And the second unit shape element 55 connected to each other at least a part of the connection portion. In the present embodiment, particularly as shown in FIGS. 2 and 3, each connecting portion 42 is connected to the first unit shape element 50 and the second unit shape element 55 from the connection portion with the length of the second unit shape element 55. It is mainly disposed on the outer surfaces 56a and 56b of the second unit shape element 55 so as to extend in the direction.

  As shown in FIG. 2, in the present embodiment, the connection portion 42 extends flat on the second unit shape element 55. That is, the outer shape of the portion constituted by the connection portion 42 in the light exit surface of the optical sheet 40 is constituted by the second unit shape element 55 that is not covered by the connection portion 42 in the light exit surface of the optical sheet 40. It is not greatly different from the outer shape of the part, and has the same configuration. However, the shapes of the plurality of connection portions 42 included in the optical sheet 40 are irregular and not constant.

  In the present embodiment, the arrangement of the connecting portions 42 is not regular, and the connecting portions 42 are all the second units that are connected to the first unit shape element 50 from the longitudinal direction (the one direction). It is not formed on the shape element 55. In particular, as shown in FIG. 3, the connecting portion 42 is connected to the first unit shape element 50 from one side in the longitudinal direction (the one direction) (left side in the left-right direction in FIG. 3). It is formed only on a part of the second unit shape element 55. In other words, the second unit shape element 55 that covers at least a part of the connection portion with the first unit shape element 50 by the connection portion 42 is the first in the longitudinal direction (the one direction) from the left side in FIG. It is connected to the 1 unit shape element 50.

  In the illustrated optical sheet, the first unit shape element 50, the second unit shape element 55, and the connection portion 42 are integrally molded from the same resin material due to the manufacturing method described later.

  By the way, as described above, the protrusion height H1 of the first unit shape element 50 from the one surface 46 of the main body 45 along the normal direction nd to the sheet surface of the optical sheet 40 is the sheet of the optical sheet 40. The protrusion height H2 of the second unit shape element 55 from the one surface 46 of the main body 45 along the normal direction nd to the surface is higher. Moreover, each connection part 42 has covered the 2nd unit shape element 55 flatly, and the thickness of the connection part 42 is not so thick. Therefore, as shown in FIGS. 2, 4, and 5, the first unit shape element 50 protrudes from one surface 46 of the main body 45 to a position higher than the second unit shape element 55 and the connection portion 42. Yes. In other words, the top of the first unit shape element 50 is closer to the sheet surface of the optical sheet 40 than the top of the second unit shape element 55 and the outer surface of the connecting portion 42 located on the second unit shape element 55. It is located far (high position) from one surface 46 of the main body 45 along the normal direction nd. That is, when the optical sheet 40 comes into contact with another sheet-like member disposed on the light output side of the optical sheet 40, the first unit shape element 50 comes into contact with the sheet-like member.

  Next, an example of a method for manufacturing the optical sheet 40 having the above configuration will be described. In the following example, the first unit shape element 50, the second unit shape element 55, and the connection portion 42 are integrally formed on the sheet material 48 by molding using the molding apparatus 60 as shown in FIG. 6. can do. As a material used for forming the first unit shape element 50, the second unit shape element 55, and the connection portion 42, a resin (as an example, which has good moldability and is easily available and has excellent light transmittance. A cured cured product of a composition of a transparent polyfunctional urethane acrylate oligomer having a refractive index of 1.57 and a dipentaerythritol hexaacrylate monomer) is preferably used.

  First, the molding apparatus 60 will be described. As shown in FIG. 6, the molding device 60 has a molding die 70 having a substantially columnar (cylindrical) outer contour. As shown in FIG. 6, a cylindrical mold surface (uneven surface) 72 is formed in a portion corresponding to the outer peripheral surface (side surface) of the column of the molding die 70. The molding die 70 having a cylindrical shape has a central axis CA that passes through the center of the outer peripheral surface of the cylinder, in other words, a central axis CA that passes through the center of the cross section of the cylinder. And the shaping | molding type | mold 70 is comprised as a roll type | mold which shape | molds the optical sheet 40 as a molded article, rotating center axis line CA as a rotating shaft line (refer FIG. 6).

As shown in FIGS. 7A and 7B, the mold surface 72 has a recess 74 corresponding to the first unit shape element 55 of the optical sheet 40, a groove 76 corresponding to the second unit shape element 55, and a connection portion 42. Corresponding notches 78 are formed. The groove 76 extends circumferentially around the central axis CA of the mold surface 72, or extends spirally around the central axis CA of the mold surface 72. In any case, the groove 76 extends in a direction substantially perpendicular to the central axis CA of the mold surface 72 (the angle of the groove 76 with respect to the central axis is about 90 ° ± 1 × 10 ⁻² ). 7A and 7B and FIGS. 8, 10A, 10B, 11A, 11B, and 13 to be referred to later, the outer contour of the mold surface that is actually a curved surface is flat for convenience of understanding. This is shown as an important aspect.

  Here, an example of a method for producing the molding die 70 having the mold surface 72 shown in FIGS. 7A and 7B will be described. The mold manufacturing method described below includes a step of preparing a mold base 80, a step of forming a recess 74 in the mold base 80 (see FIG. 9A), and cutting the mold base 80. And a step (see FIG. 9B) of forming the groove 76 and the notch 78 in the mold base 80 in which the recess 74 is formed. In particular, the method described below is characterized in that the connecting portion 78 is formed together with the groove 76 by cutting with a cutting means that keeps the amount of cut into the mold substrate 80 constant.

  In the present embodiment, as can be understood from FIGS. 9A and 9B, a mold substrate (columnar substrate) 80 having a substantially cylindrical outer contour is prepared. As a material for forming the mold base material 80, various known materials that can be used as the base material of the molding mold 70, such as steel, can be used.

  Next, as shown in FIGS. 9A, 10A, and 10B, a recess 74 having a shape complementary to the first unit shape element 50 is formed at a desired position on the outer peripheral surface 82 of the mold base 80. Form. In the example shown in FIGS. 10A and 10B, a recess 74 having a shape corresponding to a part of a sphere or a part of a spheroid is formed in the mold base material 80. The recess 74 can be formed by, for example, etching using a photolithography technique. Further, as another method, the thermal energy is concentrated on a part of the object to be processed (for example, local irradiation with laser light), and the part is melted and vaporized to remove the part by thermal removal. 74 can also be formed.

  Next, the outer peripheral surface 82 of the mold base 80 having a cylindrical shape is cut using, for example, a lathe. Specifically, first, the mold substrate 80 is held from both ends, and as shown in FIG. 9B, the mold substrate 80 is rotated so that the center axis CA of the mold substrate 80 is the rotation axis. Let Then, the cutting tool 88 for cutting is cut into the rotating mold base material 80 by a predetermined cutting amount. Next, as shown in FIG. 9B, the cutting tool 88 is rotated with respect to the mold substrate 80 with the cutting edge 88a of the cutting tool 88 cut into the rotating mold substrate 80. Relative movement is performed in a direction parallel to the axis CA. In this way, as shown in FIGS. 9B, 11A, and 11B, a groove 76 having a shape complementary to the second unit shape element 55 is formed in the mold base 80 in which the recess 74 is formed. To go.

  By the way, when the inventor repeated earnest research, when the groove 76 having a constant cross-sectional shape is formed by cutting on the outer peripheral surface of the mold base material 80 in which the concave portion 74 is formed in this way, the groove being manufactured. When 76 connects with the recessed part 74, it discovered that the notch part 78 which had a shape complementary to the connection part 42 was formed in many of the said connection locations. More specifically, when forming the groove 76 for producing the second unit shape element 55 having the above-described dimensions, a cutting condition on a lathe for producing an optical sheet molding die is described as a specific example, such as Vickers. The cutting speed is kept constant under the condition that the rotational speed of a cylindrical (roll-shaped) substrate 80 made of hard copper made of hard copper having a hardness of 180 to 230 is 50 ppm to 400 ppm and is cut with a cutting tool 88 made of diamond. The groove 76 was formed by the cutting means thus formed, and in the vicinity of the location where the groove 76 was connected to the recess 74, the side wall of the groove 76 dropped into the recess and a notch 78 was formed.

  Thus, when the groove 76 is formed by cutting in the mold base material 80 in which the concave portion 74 is formed, the position where the groove 76 being formed is connected to the concave portion 74, that is, the groove 76 of the concave portion 74. The reason why the notch 78 can be formed at a position on the one side in the longitudinal direction (upstream side in the formation process of the groove 76) is unknown in detail. explain. However, the present invention is not limited to the following estimation.

  When the cutting tool 88 reaches the recess 74 that is already formed, a change occurs in the flow of chips. For example, the flow direction of the chips changes or the flow of the chips is greatly disturbed, and the continuously connected chips are interrupted. In addition, the force applied to the cutting edge 88a of the cutting tool 88 is released. That is, deformation such as bending of the cutting tool 88 is released, and at the same time, subtle deformation of the mold base 80 in the vicinity of the groove 76 being manufactured is also released. As a result, a portion that is to become chips or burrs is pushed out or scraped out by the cutting edge portion 88 of the cutting tool 88 in a different manner from that until now. It is expected that the periphery of the portion that comes into contact with the concave portion 74 of the groove 76 will be scraped off by such a portion that should become chips or burrs, even though it is not intended for cutting.

  In the illustrated example, a single spiral groove 76 is formed in the mold base material 80, but the present invention is not limited to this. For example, a plurality of spiral grooves may be formed in the mold base material 80, or many circumferential grooves 76 are formed in the mold base material 80 by so-called parting-off processing. Also good. In this case, the depth of the groove 76 may be changed for each line. It has been confirmed that the notch 78 can be formed even when such various grooves 76 are formed by cutting. The parting-off process is to stop the relative movement of the cutting tool 88 relative to the mold base material 80 by repeating the cutting movement of the cutting tool 88 into the mold base material 80 and the retreating movement of the cutting tool 88 from the mold base material 80. In this process, a large number of circumferential grooves 76 formed in this state are produced along the central axis CA of the mold substrate 80.

  As described above, the molding die 70 can be manufactured by forming the recess 74, the groove 76, and the notch 78 in the mold substrate 80. In the molding die 70 produced as described above, the groove 76 extends substantially perpendicular to the rotation axis CA. That is, the groove 76 extends along the moving direction of the mold surface 72 of the molding die 70 during rotation about the axis CA of the molding die 70. In particular, in the molding die 70 manufactured as described above, the notch portion 78 is one side in the longitudinal direction of the groove 76 with respect to the concave portion 74 in the circumferential connection portion between the concave portion 74 and the groove 76. It is located only (upstream side in the process of forming the groove 76). The molding die 70 is placed on the molding device 60 so that the notch 78 adjacent to the recess 74 is positioned behind the recess 74 in the movement path of the mold surface 72 during the rotation of the molding die 70. It has been incorporated.

  Returning to FIG. 6, the configuration of the molding apparatus 60 other than the molding die 70 will be described. As shown in FIG. 6, the molding device 60 includes a molding base material supply device 62 that supplies a sheet material (molding base material sheet) 48 that extends in a strip shape, and a sheet material 48 to be fed and a mold 70 for molding. A material supply device 64 that supplies a fluid material 49 between the surface 72 and a curing device 66 that cures the material 49 between the sheet material 48 and the uneven surface 72 of the molding die 70; Have. The curing device 66 can be appropriately configured according to the curing characteristics of the material 49 to be cured.

  Next, a method for producing the optical sheet 40 using such a molding apparatus 60 will be described. First, a sheet material 48 made of, for example, a transparent resin is supplied from the molding substrate supply device 62. As shown in FIG. 6, the supplied sheet material 48 is fed into the molding die 70 so that the molding die 70 and the pair of rollers 68 are opposed to the concavo-convex surface (mold surface) 72 of the die 70. To be held.

  Further, as shown in FIG. 6, with the supply of the sheet material 48, a material 49 having fluidity is supplied from the material supply device 64 between the sheet material 48 and the mold surface 72 of the molding die 70. Here, “having fluidity” means that the material 49 supplied to the mold surface 72 of the mold 70 has such fluidity that it can enter the recess 74 and the groove 76 of the mold surface 72. To do. As the material 49 to be supplied, various known materials that can be used for molding can be used. Hereinafter, an example in which ionizing radiation curable resin is supplied from the material supply device 64 will be described. As the ionizing radiation curable resin, for example, a UV curable resin that is cured by being irradiated with ultraviolet rays (UV) or an EB curable resin that is cured by being irradiated with an electron beam (EB) may be selected. it can.

  As described above, the groove 76 formed in the mold surface 72 extends in a direction substantially perpendicular to the central axis CA of the molding die 60 on the mold surface 72. Therefore, as shown in FIG. 8, the material 49 supplied from the material supply device 64 is the longitudinal direction (in the one direction) of the second unit shape element 55 of the optical sheet 40 to be produced by the molding die 70. Thus, the molding die 70 is filled in a direction corresponding to the direction corresponding to the right and left direction in FIG. That is, the material 49 is supplied along the groove 76 for forming the second unit shape element 55. Further, in the present embodiment, a notch 78 is formed on one side (the right side in FIG. 8) of the recess 74 connected to the groove 76 in the longitudinal direction of the groove 76. As shown in FIG. 8, the notch 78 is adjacent to the recess 74 from the rear side in the supply direction of the material 49. Then, when the present inventors conducted an experiment, according to such a method, bubbles are formed in the first unit shape element 50 of the optical sheet 40 or on the surface of the first unit shape element 50. It was possible to effectively prevent the formation of the recessed portion.

  The mechanism that can effectively suppress the formation of bubbles and depressions in the two-dimensionally arranged point-like unit lenses is not clear, but the mechanism that can be considered as one of the causes is as follows. Will be described. However, the present invention is not limited to the following estimation.

  As described above, the groove 76 extends through the recess 74 for forming the first unit shape element 50. For this reason, when the material 49 enters the recess 74 of the mold 70, the gas (typically air) that has been filled in the recess 74 until that time is supplied from the recess 74 to the groove 76 as the material is supplied. It is easy to move to. That is, when the material 49 is filled in the concave portion 74 of the mold 70, the bubbles in the concave portion 74 tend to escape from the concave portion 74 along a specific path. In addition, a notch 78 between the recess 74 and the groove 76 is formed on the rear side of the recess 74 in the material supply direction (longitudinal direction of the groove 76). The notch 78 can alleviate a sudden change in height between the recess 74 and the groove 76. For this reason, the movement path of the bubbles traveling from the recess 74 to the groove 76 is stably secured via the notch 78. As a result, it is assumed that bubbles can be effectively prevented from being mixed into the material 49 filled in the mold surface 72.

  Thereafter, the molding sheet material 48 passes through a position facing the curing device 66 in a state where the sheet material 48 is filled with the ionizing radiation curable resin between the mold surface 72 of the mold 70. At this time, ionizing radiation corresponding to the curing characteristics of the ionizing radiation curable resin 49 is emitted from the curing device 66, and the ionizing radiation passes through the sheet material 48 and is irradiated onto the ionizing radiation curable resin 49. As a result, the ionizing radiation curable resin filled in the recess 74, the groove 76 and the notch 78 of the mold surface 72 is cured, and the first unit shape element 50 made of the cured ionizing radiation curable resin, The second unit shape element 55 and the connecting portion 42 are formed on the sheet material 48.

  By the way, when the present inventors repeated experiments, in order to promote the discharge of gas from the inside of the mold 70, the protrusion height H2 of the second unit shape element 55 is set to be the same as that of the first unit shape element 50. It has been found that it is effective to set the protrusion height H1 to 1/10 or more.

  Thereafter, as shown in FIG. 6, the sheet material 48 is separated from the mold 70, and accordingly, the unit shape elements 50, molded into the recess 74, the groove 76, and the notch 78 of the mold surface 72, respectively. 55 and the connecting portion 42 are separated from the mold 70 together with the sheet material 48. As a result, the optical sheet 40 described above is obtained.

  In the step of removing the molded unit shape elements 50 and 55 and the connection portion 42 (cured material 49) from the mold 70, the unit shape elements 50 and 55 and the connection portion 42 (cured material 49) were molded. The second unit shape element 55 is gradually pulled away from the mold 70 along the longitudinal direction (the one direction). As described above, the second unit shape element 55 is formed integrally with the first unit shape element 50 and the connecting portion 42 and extends elongated. Therefore, according to such a method, the mold release of the second unit shape element 55, the first unit shape element 50, and the connecting portion 42 is performed smoothly, and the molded second unit shape element 55, the first unit shape element 50 and the connection portion 42 are cracked, the molded second unit shape element 55, the first unit shape element 50 and the connection portion 42 are peeled off from the sheet material 48, etc. Can be effectively prevented.

  In the example shown in FIG. 8, the sheet material 48 is not in contact with the surface of the mold 70. As a result, the main body portion 45 of the optical sheet 40 manufactured as shown in FIG. 8 is composed of the sheet material 49 and the material 48 cured into a sheet shape. According to such a method, it is effective that the molded second unit shape element 55, first unit shape element 50, and connection portion 42 partially remain in the mold 70 at the time of mold release. Can be prevented.

  As described above, while the molding die 70 configured as a roll die is rotated around its central axis CA, the material 49 having fluidity is supplied into the die 70; The process of curing the material 49 supplied into the mold 70 in the mold 70 and the process of removing the cured material 49 from the mold 70 are sequentially performed on the mold surface 72 of the mold 70, whereby the optical sheet 40 is obtained. It is done. Since the mixing of bubbles in the obtained optical sheet 40 and the formation of holes in the surface of the optical sheet 40 are effectively suppressed, the obtained optical sheet 40 exhibits the expected desired optical characteristics. Will be able to. Further, since the discharge of bubbles from the mold 70 is promoted, the optical sheet 40 can be produced more efficiently at a higher speed than the conventional fly-eye lens sheet. Thereby, the manufacturing cost of the optical sheet 40 including a fly-eye lens can be greatly reduced. Note that the manufacturing cost of the mold 70 for molding the optical sheet 40 does not significantly increase from the manufacturing cost of the mold for molding the conventional fly-eye lens sheet.

  The above-described method for manufacturing the optical sheet 40 is merely an example. Therefore, the molding method is not limited to the above, and for example, a molding method such as an extrusion molding method or a transfer molding method, or other manufacturing methods can be used.

  Next, operations of the optical sheet 40, the surface light source device 20, and the transmissive display device 10 as described above will be described.

  First, the overall operation of the transmissive display device 10 and the surface light source device 20 will be described.

  The light emitted from the light source 25 travels to the viewer side either directly or after being reflected by the reflecting plate 28. The light traveling toward the observer side is isotropically diffused by the light diffusion sheet 38 and then enters the optical sheet 40. In the optical sheet 40, the light is collected so that the angle formed by the light traveling direction and the front direction (normal direction to the sheet surface of the optical sheet 40) nd is mainly close to 0 °. In the optical sheet 40, the light diffuses so that the angular distribution of luminance changes smoothly and the in-plane distribution of luminance becomes uniform. The operation of the optical sheet 40 will be described in detail later.

  The light emitted from the optical sheet 40 is then transmitted through the polarization separation film 35, and the luminance in the front direction is further increased. The transmissive display unit 15 selectively transmits the light from the surface light source device 20 for each pixel. Thereby, the observer of the transmissive display apparatus 10 can observe an image.

  Next, the operation of the optical sheet 40 will be further described in detail.

  First, the operation of the first unit shape element (point unit shape element, unit lens) 50 that forms a fly-eye lens will be described. As shown in FIGS. 4 and 5, the light L41 and L51-L54 emitted from the first unit shape element 50 of the optical sheet 40 is refracted on the light exit side surface (lens surface) of the first unit shape element (unit lens) 50. To do. Due to this refraction, the traveling direction (outgoing direction) of the light L41, L51-L54 traveling in the direction inclined from the front direction nd is mainly compared with the traveling direction of the light when entering the optical sheet 40. Is bent toward the side where the angle with respect to the normal direction nd to the sheet surface becomes smaller (see L41 in FIG. 4, L51 in FIG. 5, etc.). By such an action, as described above, the first unit shape element 50 can narrow the traveling direction of the transmitted light to the front direction nd side. That is, the first unit shape element 50 has a light collecting effect on the transmitted light.

  In addition, the light directly incident from the light source 25 to the region of the optical sheet 40 away from the light source 25, in other words, the region of the optical sheet 40 that faces the midpoint between the two adjacent light sources 25 is the front direction nd. (See the light L41 in FIG. 4). And the condensing effect | action of the 1st unit shape element 50 mentioned above exerts effectively with respect to the light which advances in this way largely inclined from the front direction nd. As a result, it is possible to improve the luminance in a region away from the light source that tends to decrease the luminance.

  As shown in FIG. 4, the region located directly above the light source 25 in the optical sheet 40 mainly has a small incident angle depending on the degree of diffusion between the light source 25 and the optical sheet 40. A large amount of light L42 enters. And such a part L42 of light repeats total reflection in the light emission side surface (lens surface) of the 1st unit shape element 50, and changes the advancing direction to the light incident side (light source side). As a result, it is possible to prevent the luminance at the position directly above the light emitting portion of the light source 25 from becoming too high.

  Depending on the distance from the light source 25 as described above, the optical action mainly exerted on the transmitted light from the first unit shape element 50 is different, so that it occurs according to the arrangement of the light emitting portions of the light source 25. Luminance unevenness (tube unevenness) can be effectively reduced, and an image of a light source (light image) can be made inconspicuous. As described above, the first unit shape elements 50 form a fly-eye lens and are arranged in different directions on the one surface 46 of the main body 45. That is, the first unit shape elements 50 are two-dimensionally arranged on the one surface 46 of the main body 45. Therefore, the fly-eye lens composed of the first unit shape element 50 can effectively exert an optical action on a light component along an arbitrary direction on the sheet surface of the optical sheet 40. As a result, even if the optical sheet 40 is disposed on the light source 25 without considering the arrangement direction of the light sources 25, the light collecting function and the light diffusing function by the first unit shape element 50 are effectively exhibited. .

  Next, the operation of the second unit shape element (linear unit shape element, unit prism) 55 forming the linear array prism portion will be described. As shown in FIGS. 4 and 5, the lights L46 and L55 to L59 emitted from the second unit shape element 55 of the optical sheet 40 are also refracted on the light output side surface (prism surface) of the second unit shape element (unit prism) 55. To do. Due to this refraction, the traveling direction of the light L46, L55-L58 traveling in the direction inclined from the front direction nd is mainly toward the sheet surface of the optical sheet 40 as compared to the traveling direction of the light when entering the optical sheet 40. Is bent toward the side where the angle with respect to the normal direction nd becomes smaller. By such an action, as described above, the second unit shape element 55 can narrow the traveling direction of the transmitted light to the front direction nd side. That is, the second unit shape element 55 exerts a condensing action on the transmitted light.

  On the other hand, as in the first unit shape element 50, the light L47 traveling in the direction not largely inclined from the front direction nd is entirely on the light exit side surface (prism surface) of the second unit shape element 55, as shown in FIG. The reflection is repeated and the traveling direction is changed to the light incident side (light source side).

  As described above, in the present embodiment, the arrangement direction of the second unit shape elements 55 is parallel to the arrangement direction of the light sources 25. Therefore, the light is incident on the region of the optical sheet 40 centered on the position facing the midpoint between the two adjacent light sources 25 and the light from the light source 25 is incident at a large incident angle. The direction of travel of the light to be transmitted is changed by refraction at the light exit side surface (prism surface) of the second unit shape element 55 so that the angle formed by the travel direction of the light and the front direction nd approaches 0 °. Can do. As a result, it is possible to prevent the luminance from becoming too low in the region of the optical sheet 40 centered on the position facing the midpoint between the two adjacent light sources 25.

  In addition, the light incident on the region of the optical sheet 40 that is located immediately above the light source 25 and in which a large amount of light from the light source 25 is incident at a small incident angle is converted into the second unit shape element. The light can be returned to the light source side by total reflection at the light exit side (prism surface) 55 (see the light L47 in FIG. 4). As a result, it is possible to prevent the luminance from becoming excessively high in the region of the optical sheet 40 located immediately above the light source 25.

  As a result, in the present embodiment, the second unit shape element 55 also effectively reduces the luminance unevenness (tube unevenness) that occurs according to the arrangement of the light emitting portions of the light source 25, and the light source image (light image). ) Can be made inconspicuous.

  By the way, as shown in FIG. 5, the light incident on the second unit shape element 55 configured to have a triangular cross-sectional shape is based on the front direction nd when the traveling direction is inclined from the front direction nd. As a result, a large amount of light enters the light exit side surface (one side prism surface) 56a inclined to the opposite side to the traveling direction of the light L55-L58. If the inclination angle of the traveling direction of the light L55-L58 with respect to the front direction nd is constant, the position where the light L55-L58 is incident on the light exit side surface (one side prism surface) 56a. Regardless of the angle of inclination, the inclination angle of the emission direction of the light L55 to L58 with respect to the front direction nd when emitted from the second unit shape element 55 is also constant. That is, the traveling direction of the light emitted from the second unit shape element 55 is generally determined due to the configuration (for example, shape, refractive index, etc.) of the second unit shape element 55.

  In addition, the inclination angle with respect to the front direction nd of the traveling direction in the optical sheet of light L51-L59 in FIG. 5 is the same.

  With respect to such optical characteristics of the second unit shape element 55, as shown in FIG. 5, light L51-L54 incident on the first unit shape element 50 configured to have a circular cross section or an elliptical cross section. Even if the inclination angle of the traveling direction of the light with respect to the front direction nd is constant, the first light depends on the position on the light emission side surface (lens surface) of the first unit shape element 50 depending on which position the light enters. When the light is emitted from the unit shape element 50, the inclination angle of the light emission direction with respect to the front direction nd is different. Therefore, the traveling direction of the light emitted from the first unit shape element 50 is not only the configuration (for example, the shape and refractive index) of the first unit shape element 55 but also the incident position on the first unit shape element 55. Will also be greatly affected.

  The arrangement pitch P1 (see FIG. 3) of the first unit shape elements 50 and the arrangement pitch P2 (see FIG. 3) of the second unit shape elements are very short compared to the arrangement interval of the light sources 25. . Therefore, the inclination angles of the light incident from the light source 25 toward the single unit shape elements 50 and 55 are substantially the same. As a result, the second unit shape element (unit prism) 55 can narrow the angle of the light traveling direction with respect to the front direction nd within a relatively narrow angle range centered on the front direction nd. That is, the 2nd unit shape element 55 comes to be able to exhibit the very outstanding condensing function by designing the structure suitably.

  On the other hand, the first unit shape element (unit lens) 50 narrows the angle of the light traveling direction with respect to the front direction nd within a relatively wide angle range, and smoothly changes the luminance distribution within the narrowed angle range. It is possible to make it. That is, the second unit shape element (unit prism) 55 can exhibit a stronger condensing function as compared with the first unit shape element (unit lens) 50, and the first unit shape element (unit lens). ) 50 can exhibit a stronger light diffusion function than the second unit shape element (unit prism) 55.

  According to the optical sheet 40 having the first unit shape element 50 and the second unit shape element 55 as described above, the transmitted light can be condensed and the front direction luminance can be effectively improved. Can be appropriately diffused to make the in-plane distribution of luminance uniform, and the angular distribution of luminance can be smoothly changed. Therefore, according to the surface light source device 20 and the transmissive display device 10 in which such an optical sheet 40 is incorporated, the front luminance can be increased by effectively using the light source light, and an image can be visually recognized. The angle range (viewing angle) with respect to the front direction nd can be widened. That is, extremely ideal energy saving is realized. Further, it is possible to prevent the occurrence of luminance unevenness (tube unevenness) due to the configuration (arrangement) of the light source 25 and display an image with excellent image quality.

  The optical sheet 40 has a connection portion 42 that is disposed so as to cover the connection location of the first unit shape element 50 and the second unit shape element 55. However, in the optical sheet 40 manufactured using the molding die 70 described above, the connection portion 42 is second from the connection portion between the first unit shape element 50 and the second unit shape element 55 as described above. The unit shape element 55 extends flatly. Therefore, as shown by the dotted line in FIG. 4, the connection portion 42 exerts a light diffusion effect slightly stronger than the second unit shape element 55, but substantially has the same optical effect. It will be affected. That is, in the optical sheet 40 in the present embodiment, the connection portion 42 is extremely effective for eliminating bubbles and holes from the first unit shape element 50, and imparts a desired optical function to the first unit shape element 50. It contributes to this and does not adversely affect the light collecting action and light diffusion action of the entire optical sheet 40. Rather, the shape of the connecting portion 42 is positively and appropriately designed by changing the manufacturing conditions in the above-described manufacturing method of the molding die 70 or further changing to a method different from the above-described manufacturing method of the molding die 70. Accordingly, it is possible to impart an excellent optical function to the optical sheet 40.

  Moreover, when the present inventors repeated earnest experiments, by adjusting the distance between the two adjacent first unit shape elements 50 and the arrangement pitch P2 of the second unit shape elements 55, the front direction Improvement in luminance and suppression of in-plane variation in luminance (light source image concealment) could be realized at the same time. Specifically, the average minimum interval Sa of the first unit shape elements 50 is perpendicular to one direction (that is, the longitudinal direction of the second unit shape element 55) on the sheet surface of the main body 45 (that is, the second unit shape element 50). The arrangement pitch P2 of the second unit shape elements 55 along the arrangement direction of the unit shape elements 55 is preferably greater than or equal to P2. Preferably, the average minimum interval Sa of the first unit shape elements 50 is preferably at least twice the arrangement pitch P2 of the second unit shape elements 55.

  Here, the average minimum distance Sa is a first unit shape element 50 that is arbitrarily selected, and is disposed closest to the first unit shape element 50 along the sheet surface of the main body 45. It means the average value of the separation distance along the sheet surface of the main body 45 between the other first unit shape element 50. In the embodiment described above, the first unit shape elements 50 having the same width (in the illustrated example, the diameter on the one surface 46 of the main body 45) W1 have the same arrangement pitch P1 and the main body 45 Are distributed on one side 46 of the substrate. Therefore, the average minimum interval Sa is a difference (= P1−W1) between the arrangement pitch P1 and the width W1 (see FIG. 3). As another example, when the first unit shape elements 50 are arranged randomly (irregularly) on one surface 46 of the main body 45, one arbitrarily selected first unit shape element 50 and A large number of spacings between the first unit shape element 50 and the other first unit shape elements 50 arranged closest to the first unit shape element 50 along the sheet surface of the main body 45, for example, 20 to 100 The average minimum interval Sa can be obtained by measuring points and taking the average of the measured values.

  On the other hand, in the present embodiment, the second unit shape elements 55 are arranged without a gap therebetween. Accordingly, the arrangement pitch P2 of the second unit shape elements 55 along the direction orthogonal to one direction on the sheet surface of the main body 45 corresponds to the width W2 of the second unit shape elements 55.

  When the average minimum interval Sa of the first unit shape elements 50 is equal to or greater than the arrangement pitch P2 of the second unit shape elements 55, it is possible to achieve both improvement in front direction luminance and suppression of in-plane variation in luminance. It is not clear about the mechanism. However, according to the results of experiments conducted by the present inventors, the optical function of the first unit shape element 50 is not impaired by the second unit shape elements 55 arranged between the first unit shape elements 50, and at the same time. It is presumed that the second unit shape element 55 exhibits an optical function. On the other hand, when the above condition is satisfied, at least one of the two first unit shape elements 50 adjacent to each other along the arrangement direction of the second unit shape elements 55 (the direction orthogonal to the one direction) is surely provided. Two second unit shape elements 55 exist (see FIG. 3). In other words, as well shown in FIG. 2, one first extension extending between two first unit shape elements 50 adjacent in one direction without being covered by the other first unit shape elements 50. The two unit shape elements 55 (strictly speaking, the light emission side surface corresponding to one second unit shape element 50) extends. That is, the second unit shape element 55 is disposed between the first unit shapes 50 so as to effectively exhibit an optical function. Such structural features are consistent with the above estimation.

  Note that when the average minimum interval Sa of the first unit shape elements 50 becomes very large, the optical function of the fly-eye lens constituted by the first unit shape elements 50 is degraded. In consideration of the size of unit-shaped elements forming a fly-eye lens that is normally used, the size of linear prisms, and the like, the average minimum interval Sa of the first unit-shaped elements 50 is the arrangement pitch of the second unit-shaped elements 55. It is preferably 10 times or less of P2.

  By the way, as described above, most of the light incident on the second unit shape element 55 configured to have a triangular cross-sectional shape is based on the front direction nd when the traveling direction is inclined from the front direction nd. As a result, a large amount of light enters the light exit side surface (one side prism surface) 56a inclined to the opposite side to the traveling direction of the light L55-L58. However, as shown in FIG. 5, a part L59 of the light incident on the second unit shape element 55 has a light emitting side surface on the other side (the other side inclined to the same side as the traveling direction of the light L59 with respect to the front direction nd. Side prism surface) 56b. Most of the light incident on the light exit side surface 56b on the other side is totally reflected by the light exit side surface 56b. A part L59 of the light may be emitted from the second unit shape element (unit prism) 55 at a very large emission angle after being totally reflected. Such light is so-called side lobe and is not effectively used in the transmissive display device 10, but rather deteriorates the image quality of the video.

  On the other hand, according to the present embodiment, not only the second unit shape element portion 55 but also the first unit shape element portion 50 is provided on one surface 46 of the main body portion 45. As shown in FIG. 5, the protrusion height H <b> 1 of the first unit shape element 50 from the main body 45 is higher than the protrusion height H <b> 2 of the second unit shape element 55 from the main body 45. Therefore, the light L59 emitted from the second unit shape element (unit prism) 55 at an extremely large emission angle can enter the first unit shape element 50 (see the light L59a), or the first unit shape element 50. Can be reflected from the light exit side (see light L59b).

  The light L59a incident on the first unit shape element 50 can be totally reflected once or more on the light exit side surface of the first unit shape element 50, and the traveling direction thereof can be changed to the opposite side (light source side, light incident side). That is, the first unit shape element 50 collects the light once emitted from the optical sheet 40 as unnecessary light forming side lobes in the optical sheet 40 and reuses it as light that can contribute to improvement of the luminance in the front direction. To work. On the other hand, the light L <b> 59 b reflected from the light exit side surface of the first unit shape element 50 changes the traveling direction due to reflection by the first unit shape element 50. When the width of the first unit shape element 50 gradually decreases from the base end side (light incident side) of the first unit shape element 50 toward the tip end side (light output side) as in the example shown in the drawing, By the reflection at the first unit shape element 50, the traveling direction of the light L59b is bent so that the angle formed by the traveling direction with respect to the front direction nd becomes small. That is, the light L59 once emitted from the optical sheet 40 as unnecessary light forming a side lobe can be condensed by the light exit side surface of the first unit shape element 50 and can be converted into light in the vicinity of the normal direction nd. .

  In addition, when the present inventors repeated experiments, in order to effectively exhibit such a side lobe suppressing action, the protrusion height H2 of the second unit shape element 55 is set to the first unit shape. It has been found that it is effective to set the protrusion height H1 of the element 50 to 9/10 or less, and it is more effective to set it to 2/3 or less.

  According to the present embodiment as described above, the optical sheet 40 is arranged on the main body 45 by the plurality of first unit shape elements (dot unit shape elements) 50 two-dimensionally arranged on the main body 45. A plurality of second unit shape elements (linear unit shape elements) 55 extending in parallel with one direction, one first unit shape element 50 and one first unit shape element 50 connected from the one direction. And a connecting portion 42 that covers at least a part of the connecting portion of the second unit shape element 55. When such an optical sheet 40 is produced by molding using the molding die 70 so that the longitudinal direction (the one direction) of the second unit shape element 55 is along the machine direction, the first dot-like shape is formed. Air bubbles in the recess 74 of the molding die 70 corresponding to the unit shape element 50 correspond to the linear second unit shape element 55 via the notch 78 of the molding die 70 corresponding to the connection portion 42. It is guided to the groove 76 of the molding die 70. That is, it is possible to make it difficult for air to accumulate in the recess 74 of the mold 70 for molding the first unit shape element 55, thereby forming bubbles in the optical sheet 40 including the first unit shape element 50. , And the formation of a recessed portion on the surface of the optical sheet 40 can be prevented. As a result, it is possible to stably produce the optical sheet 40 capable of exhibiting a desired desired optical function. Further, since the discharge of bubbles from the mold 70 is promoted, the optical sheet 40 can be produced more efficiently at a higher speed than the conventional fly-eye lens sheet. Thereby, the manufacturing cost of the optical sheet 40 including the first unit shape elements 50 that are two-dimensionally distributed and arranged on the main body 45 can be greatly reduced. Further, the manufacturing cost of the mold 70 for molding the optical sheet 40 does not significantly increase from the manufacturing cost of the mold for molding the conventional fly-eye lens sheet.

  In particular, in the optical sheet 40 according to the present embodiment, the second unit shape element 55 is connected to the first unit shape element 50 and the second unit shape element 55 covered by the connection portion 42. It is only the connection location which is connected to the 1st unit shape element 50 from one side in the longitudinal direction (the above-mentioned one direction) of 55. In such an optical sheet 40, the second unit shape element 55 has a longitudinal direction (the one direction) along the machine direction, and the other side in the longitudinal direction of the second unit shape element 55 is the front. When produced by shaping with the side being the rear, the bubbles in the recess 74 corresponding to the point-shaped first unit shape element 50 pass through the notch 78 corresponding to the connection portion 42 to form a line. It is more stably guided to the groove 76 corresponding to the second unit shape element 55 having a shape. As a result, it is possible to more effectively prevent air bubbles from being mixed into the optical sheet 40 and formation of holes in the surface of the optical sheet 40.

  Further, according to the present embodiment, the second unit shape element 55 is formed in the gap between the adjacent first unit shape elements 50 on the one surface 46 of the main body 45. In many conventional fly-eye lens sheets, a gap is inevitably formed between the adjacent first unit-shaped elements 50 due to manufacturing problems, and the area of the gap is a flat surface. Then, it is estimated that the light source light incident on the flat surface area travels straight, and as a result, the inconvenience that the image of the light source 25 becomes easy to be visually observed has occurred. Thus, in the optical sheet 40 of the present invention, the light traveling toward the region between the first unit shape elements 50 on the one surface 46 of the main body 45 has a light diffusing function and a condensing function. The course direction is changed by the obtained second unit shape element 55. That is, light is emitted from between the first unit-shaped elements 50 on the one surface 46 of the main body 45 in the same traveling direction without changing the traveling direction, so-called “elementary omission” is prevented. can do. Therefore, compared to the conventional fly-eye lens sheet, it is possible to improve the other while maintaining at least one of the light collecting function and the light diffusion function of the optical sheet 40. As a result, the optical characteristics of the surface light source device 20 (the transmissive display device 10), for example, the front luminance and the viewing angle can be improved. Furthermore, it is expected that the number of optical sheets 40 incorporated in the surface light source device 20 can be reduced. In this case, the manufacturing cost of the surface light source device 20 can be effectively reduced, and the surface light source device 20 Fabrication can be facilitated.

  Furthermore, according to the present embodiment, the first unit shape element 50 and the second unit shape element 55 are formed as elements having different optical characteristics. Therefore, the configurations of the first unit shape element 50 and the second unit shape element 55 are appropriately designed, and the range of the region where the first unit shape element 50 is formed on one surface 46 of the main body 45 and the second Desired optical characteristics can be imparted to the optical sheet 40 by appropriately adjusting the range of the region where the unit shape elements 55 are formed.

  Further, according to the present embodiment, the first unit shape elements 50 are arranged on the one surface 46 of the main body portion 45 by an arrangement in which the respective elements are slightly separated from the close-packed structure. ing. According to this embodiment, it is possible to densely arrange the first unit shape elements 50 on the one surface 46 of the main body 45. Thereby, the optical action by the first unit shape element 50 can be effectively exerted on the transmitted light. Further, by densely arranging the first unit shape elements 50, the area where the first unit shape elements 50 are not arranged on the one surface 46 of the main body 45 can be reduced to the minimum necessary. This can more effectively prevent “striking”.

  Note that various modifications can be made to the above-described embodiment. Hereinafter, an example of modification will be described with reference to the drawings. In the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant descriptions are omitted.

  For example, in the above-described embodiment, the first unit shape element 50 is connected to the first unit shape element 50 from one side in the longitudinal direction (the one direction) of the second unit shape element 55. Although the example which the connection part 42 covers only the connection location of the 2 unit shape element 55 was shown, it is not restricted to this. For example, as shown in FIG. 12, a first connection portion 43 a is provided on one side in the longitudinal direction of the second unit shape element 55 of one first unit shape element 50, and You may make it the 2nd connection part 43b be provided in the other side in the longitudinal direction of the 2nd unit shape element 55. FIG. That is, in the example shown in FIG. 12, the first unit shape element 50 and the second unit connected to the first unit shape element 50 from one side in the longitudinal direction (the one direction) of the second unit shape element 55. A first connecting portion 43 a is provided so as to cover at least a part of the connecting portion between the shape element 55 and the second unit shape element 55 with respect to the first unit shape element 50 and the first unit shape element 50. The second unit shape element 55 connected from the other side in the longitudinal direction (the one direction) and the second connection portion 43b covering at least a part of the connection portion are provided. According to such an optical sheet 40, the angular distribution of the luminance on the light exit surface of the optical sheet 40 measured in the plane along the longitudinal direction of the second unit shape element 55 is more strict across the front direction. It can be made to have symmetry.

  The optical sheet 40 shown in FIG. 12 can be manufactured by molding using a molding die having the mold surface 72 shown in FIG. In the example shown in FIG. 13, the first cutout portion covers at least a part of the connection portion between the recess 74 and the groove 76 connected to the recess 74 from one side in the longitudinal direction of the groove 76. 79a is formed, and the second notch 79b covering at least a part of the connection portion between the recess 74 and the groove 76 connected to the recess 74 from the other side in the longitudinal direction of the groove 76, Is formed.

  Further, the molding die 70 including the mold surface 72 shown in FIG. 13 can be manufactured as follows. First, in the same manner as the method for manufacturing the mold 70 described in the above-described embodiment, a mold base material 80 is prepared, and then the recess 74 is formed in the prepared mold base material 80. Further, the groove 76 is formed in the mold base material 80 in which the recess 74 is formed by cutting. However, unlike the manufacturing method of the mold 70 described in the above embodiment, a plurality of grooves 76 are formed in the mold base 80 as shown in FIGS. 14A and 14B. Then, when cutting the plurality of grooves 76, the cutting direction is changed between the grooves 77a and 77b. In the example shown in FIGS. 14A and 14B, two grooves 77 a and 77 b are formed in the mold base material 80. As shown in FIG. 14A, first the first groove 77a is formed while rotating the mold base member 80 in one direction and feeding the cutting tool 88 in one direction. Thereafter, as shown in FIG. 14B, the first groove 77b is formed while rotating the mold base member 80 in the reverse direction and feeding the cutting tool 88 in the reverse direction. As a result, as shown by an arrow in FIG. 13, the advancing direction of the cutting tool 88 when forming the groove 76 is opposite between the adjacent grooves 77 a and 77 b of the produced molding die 70. Then, as shown in FIG. 13, when the advancing direction of the cutting tool 88 is reversed between the adjacent grooves 76, the notch portions formed on the grooves 76 as the grooves 76 are formed by cutting. 42 is also located between the adjacent grooves 76 on the opposite side in the longitudinal direction of the groove 76 with the recess 74 interposed therebetween.

  Moreover, although the example which forms the groove | channel 76 and the notch part 78 by cutting in the embodiment mentioned above was shown, it is not restricted to this. For example, the recess 74 and the groove 76 are formed by thermally removing a part of the workpiece to be concentrated by applying thermal energy (for example, local irradiation of laser light) and removing the part by dissolving and vaporizing the part. The notched portion 78 may be formed in the mold base 80 after being formed. It is possible to give a desired shape to the notch 78 of the mold 70 manufactured by such a method. In this case, the optical sheet 40 manufactured using the mold 70 can exert a desired optical action on the light incident on the connection portion 42. For example, a monitor placed on the street may not be required to actively emit light upward from the front direction because it is placed at a high place. For such a monitor, the angular distribution of luminance at the light exit surface of the optical sheet 40 measured in the plane along the longitudinal direction of the second unit shape element 55 is asymmetric with respect to the front direction. In addition, the optical sheet 40 to which directivity is imparted by the shape of the connecting portion 42 can be used.

  Further, in the above-described embodiment, the first unit shape element 50 has a shape corresponding to a part of a circular shape or a part of an elliptical shape in a cross section (in a three-dimensional shape, a part of a sphere or a spheroid). Although an example was shown, it is not restricted to this. For example, the first unit shape element 50 may have a triangular cross section (in terms of a three-dimensional shape, a cone). Besides, the cross-sectional shape is hyperbola, parabola, cycloid, cardioid, normal distribution curve, sine curve, hyperbolic sine curve, elliptic function curve (sn function, cn function, etc.), Bessel function curve, or Rankine egg shape A three-dimensional shape corresponding to a part of the above can also be appropriately adopted according to desired optical characteristics (condensing function, light diffusion function, convergence, retroreflectivity, etc.). In the above-described embodiment, an example in which the bottom surface (surface connected to the main body portion 45) of the first unit shape element 50 is circular (see FIG. 3, ie, the normal nd of the sheet surface of the optical sheet 40 is rotated) Although an example of a rotating body having a shaft is shown, the present invention is not limited to this. For example, the bottom surface of the first unit shape element 50 may be formed as an ellipse or a polygonal shape such as a triangle, a quadrangle, a pentagon, a hexagon, an octagon, or the like. Furthermore, in the above-described embodiment, the example in which the first unit shape elements 50 of the optical sheet 40 all have the same configuration has been described, but the present invention is not limited thereto. The optical sheet 40 may include a plurality of types of first unit shape elements 50 that are different from each other in at least one of height, cross-sectional shape, bottom surface shape, and the like.

  Furthermore, in the above-described embodiment, the first unit shape elements 50 are arranged on the one surface 46 of the main body 45 side by side at a constant pitch along two directions inclined by 60 ° from each other. An example is shown, but the present invention is not limited to this. For example, the first unit shape elements 50 may be arranged on the one surface 46 of the main body 45 so as to be arranged at a constant pitch (arranged in a square lattice pattern) along two orthogonal directions. Further, the first unit shape elements 50 may be randomly arranged on one surface 46 of the main body 45. As an example of a method of randomly arranging the first unit shape elements 50 on the one surface 46 of the main body 45, the following method can be given. First, for example, as in the above-described embodiment, temporary reference positions serving as references for a number of first unit shape elements are set so that the spacing between two adjacent first unit shape elements is constant. Determine regularly. Next, as an example, within a range in which the two adjacent first unit shape elements do not overlap, between the two adjacent first unit shape elements in the case where the first unit shape elements are arranged at a temporary provisional position as a reference Each of the first unit shape elements is positioned on one surface 46 of the main body 45 by shifting from the temporary provisional position as a reference, with various lengths equal to or less than half of the separation interval. When the first unit shape elements 50 are randomly arranged on the one surface 46 of the main body portion 45 in this way, the first unit shape elements 50 are unevenly arranged on the main body portion 45. While preventing the occurrence of in-plane variation in luminance, it is possible to prevent the moire (interference fringes) due to the arrangement of the first unit shape elements 50 from being noticeable.

  Further, in the above-described embodiment, the example in which the second unit shape element 55 has an isosceles triangular shape in the cross section is shown, but the present invention is not limited thereto. For example, the cross-sectional shape of the second unit shape element 55 may be a shape obtained by modulating or deforming a triangular shape for the purpose of imparting various characteristics. As a specific example, in order to adjust the optical function appropriately, the cross-sectional shape of the second unit shape element 55 is either a shape in which one or more sides of a triangle are bent (bent) as shown in FIG. It may be a shape in which one or more sides are curved (so-called fan shape), a shape in which the vicinity of the apex of the triangle is curved and rounded, or a shape in which minute irregularities are provided on one or more sides of the triangle. Further, the cross-sectional shape of the second unit shape element 55 may have a shape other than a triangular shape, for example, various polygonal shapes such as a quadrangle such as a trapezoid, a pentagon, or a hexagon. Furthermore, the second unit shape element 55 may have a shape corresponding to a part of a circle or an ellipse in the cross section.

  Furthermore, in the above-described embodiment, the example in which all the second unit shape elements 55 of the optical sheet 40 have the same configuration has been described, but the present invention is not limited thereto. The optical sheet 40 may include a plurality of types of second unit shape elements 55 that differ in at least one of height, cross-sectional shape, and the like.

  Furthermore, in the above-described embodiment, the example in which the adjacent second unit shape elements 55 are arranged adjacent to each other without a gap has been shown. However, the present invention is not limited to this, and the optical characteristics such as the omission are caused. In a non-existing range, adjacent second unit shape elements 55 are arranged with a gap, and a region where neither the first unit shape element 50 nor the second unit shape element 55 is arranged is one of the main body portions 45. The surface 46 may be provided.

  Further, the optical sheet 40 may have a diffusion function for diffusing light. For example, the main body 45 may have a light diffusion layer (intermediate mat layer) between one surface 46 and the other surface 47. Such a light diffusion layer (intermediate mat layer) can be configured as a layer having a base and a light diffusing agent dispersed in the base. The light diffusing layer containing the light diffusing agent can be provided with the light diffusing function, for example, when the light diffusing agent has a light reflecting function, or when the light diffusing agent has a refractive index different from that of the base. As another example, the other surface 47 of the main body 45 may be formed of a light diffusion layer (back surface mat layer). Such a light diffusing layer (back surface mat layer) is configured as a layer having a light diffusing agent similar to the above-described intermediate mat layer, or a layer having an uneven surface formed by embossing or hairline processing. obtain.

  Furthermore, the optical sheet 40 may include an antistatic layer. By adding an antistatic layer to the optical sheet 40, the antistatic function can be expressed in the entire main body 45. According to this modification, adhesion of foreign matter such as dust can be reduced, and adverse effects on optical characteristics can be suppressed. The light diffusion layer described above may have an antistatic function.

  Furthermore, the optical sheet 40 may be formed so as to include an antireflection layer forming the most incident light side surface (light incident surface 41). Since the most incident side surface of the optical sheet 40 is formed by the antireflection layer, the light use efficiency can be improved. The antireflection layer may be formed as a single layer of a layer (low refractive index layer) having a lower refractive index than a layer adjacent to the light output side (for example, the main body 45). Alternatively, the antireflection layer includes a plurality of layers in which layers having a low refractive index (low refractive index layer) and layers having a higher refractive index than those having a low refractive index (high refractive index layer) are alternately arranged. These layers may be formed as a plurality of layers in which the most incident light side is a low refractive index layer (low refractive index layer). Further, the antireflection layer is a plurality of projections protruding on the light incident side arranged at a pitch equal to or less than the light wavelength, as described in JP-A-50-70040, each facing the light incident side. It may be formed as a moss-eye type layer having a plurality of protrusions that gradually reduce the cross-sectional area.

  Further, in the above-described embodiment, the example in which the arrangement direction of the elongated second unit shape elements 55 and the arrangement direction of the elongated light sources 25 are parallel is shown, but the present invention is not limited thereto. The arrangement direction of the elongated second unit shape elements 55 and the arrangement direction of the elongated light sources 25 may cross each other, and may be orthogonal as an example.

  Furthermore, in the above-described embodiment, an example in which the light emitting unit of the light source 25 of the surface light source device 20 is formed of a cold cathode tube that extends linearly has been described, but the present invention is not limited thereto. As the light source 25, it is also possible to use a light emitting unit made up of a dot-like LED (light emitting diode), a planar EL (electroluminescent element), or the like. In the above-described embodiment, an example in which the optical sheet 40 is applied to the direct-type surface light source device 20 has been described, but the present invention is not limited thereto. It is also possible to apply the optical sheet 40 described above to, for example, an edge light type (also referred to as a side light type) surface light source device. In such a case as well, the optical sheet 40 is a direct type surface light source device 20. The effect similar to the case where it is applied to can be produced.

  Furthermore, in the above-described embodiment, an example of the overall configuration of the surface light source device 20 and the transmissive display device 10 in which the optical sheet 40 is incorporated has been described, but is not limited thereto. The polarization separation film 35 and the light diffusion sheet 38 may be deleted or replaced with another member, or another sheet-like member such as a light collecting sheet may be added and incorporated in the surface light source device 20 and the transmissive display device 10. May be.

  In addition, although the some modification with respect to embodiment mentioned above was demonstrated above, naturally, it is also possible to apply combining several modifications suitably.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to this Example.

<Evaluation 1>
[Optical sheet]
The optical sheet according to Examples A to D described below and the optical sheet according to Comparative Example 1 are the same as the above-described manufacturing method using an apparatus having the same configuration as the molding apparatus illustrated in FIG. Produced by the method. At this time, different molds were used for each optical sheet, but the other conditions related to the production of the optical sheet were the same.

(Examples A to D)
The optical sheets according to Examples A to D are a plurality of first units that are two-dimensionally arranged on one surface of the main body, similarly to the optical sheets in the above-described embodiment illustrated in FIGS. Shape elements (dot unit shape elements) and a plurality of second unit shape elements (linear shapes) arranged on one surface of the main body and extending in a certain cross-sectional shape parallel to one direction on the sheet surface of the main body Unit shape element) and a connection portion that at least partially covers a connection portion of the first unit shape element and the second unit shape element that are connected to each other from the one direction.

  The first unit shape element of each optical sheet has a shape corresponding to a part of a sphere, and the second unit shape element of each optical sheet has a right isosceles triangle shape on the main cutting plane. Further, the arrangement of the first unit shape elements and the arrangement of the second unit shape elements in each optical sheet are the same as those in the above-described embodiment described mainly with reference to FIG. However, the arrangement pitch P1 of the first unit shape elements was changed between the optical sheets. As shown in Table 1, the dimensions other than the arrangement pitch P1 of the first unit shape elements were the same between the optical sheets.

  Moreover, the mold for manufacturing the optical sheets according to Examples A to D was manufactured in the same manner as the manufacturing method in the above-described embodiment illustrated in FIGS. 9A to 11B. Therefore, in the optical sheets according to Examples A to D manufactured using such a mold, the second unit shape element is connected to the first unit shape element and the second unit shape element that are covered by the connection portion. It became only the connection location connected to the 1st unit shape element from the one side in the longitudinal direction (said one direction).

(Comparative Example A)
The optical sheet according to Comparative Example A was a normal fly-eye lens sheet. That is, the second unit shape element and the connection portion were not provided in the optical sheet according to Comparative Example A. The configuration (shape, arrangement method, etc.) of the unit lens constituting the fly-eye lens of the optical sheet according to Comparative Example A was the same as the configuration of the first unit shape element of the optical sheet according to Examples A to D. However, the unit lenses in the optical sheet according to Comparative Example A were arranged on one surface of the main body portion with the highest possible filling rate by a conventional fly eye lens manufacturing method. Specifically, due to manufacturing limitations, as shown in Table 1, two adjacent unit lenses were not adjacent to each other, and an average gap of about 4 μm was generated between the two adjacent unit lens elements.

〔Evaluation methods〕
It was confirmed whether or not defects such as bubbles and holes were formed for each optical sheet produced by molding. As shown in Table 1, many bubbles and holes were visually recognized in the optical sheet according to Comparative Example A, but no bubbles or holes were confirmed in the optical sheets according to Examples A to D.

<Evaluation 2>
[Transparent display device]
Using the optical sheet according to Examples A to D and the optical sheet according to Comparative Example A, a transmissive display device as shown in FIG. 16 was produced. The configuration other than the optical sheet is the same between the transmissive display devices. Further, the components other than the optical sheet of the transmissive display device used members of a commercially available 32-inch liquid crystal display device.

  As shown in FIG. 16, the transmissive display device includes a surface light source device and a liquid crystal display panel (transmissive display unit). Further, the surface light source device is disposed on the light output side of the light diffusion sheet, a light source composed of a plurality of cold cathode tubes extending in a slender shape, a reflection plate surrounding the light source, a light diffusion sheet disposed on the light output side of the light source, and And an optical sheet. In each transmissive display device, the arrangement direction of the second unit shape elements of the optical sheet and the arrangement direction of the light sources (cold cathode tubes) were made parallel.

〔Evaluation methods〕
(Evaluation method 1)
The brightness in the front direction (cd / m ² ) was measured in a state where white was displayed on the entire surface by each transmissive display device. For the measurement of luminance, BM-7 manufactured by Topcon was used. The luminance measurement results are shown in Table 1. In Table 1, the measurement result is expressed as a ratio of measured values for each transmissive display device.

(Evaluation method 2)
Each transmissive display device was arranged such that the light emitting surface (sheet surface of the optical sheet) of the surface light source device was along the vertical direction, and the longitudinal direction of the light source was extended in the horizontal direction. In a state where white is displayed by the transmissive display device, the luminance is measured from various measurement directions on the horizontal plane by changing the angle with respect to the front direction, and the luminance angle in the horizontal plane (the plane including the longitudinal direction of the light source) Distribution was obtained. Similarly, the measurement direction was also changed in the vertical direction, and an angular distribution of luminance in a vertical plane (a plane perpendicular to the longitudinal direction of the light source) was obtained. For the measurement, EZ-contrast manufactured by ELDIM, France was used. From the angular distribution of luminance, an angle (half-value angle) at which half of the front luminance that was the highest luminance was measured was measured. Table 1 shows the average value of the angle values measured on both sides with the front direction as the center.

(Evaluation method 3)
Whether or not the image of the light source is visually recognized in a state where white is displayed by each transmissive display device was visually confirmed. The confirmation results are shown in Table 1. In Table 1, “◯” is marked for display devices in which the image of the light source could not be visually recognized. Δ was marked on a display device in which the image of the light source was visually observed by staring, although the image of the light source was not noticeable when observed with normal attention.

DESCRIPTION OF SYMBOLS 10 Transmission type display device 15 Transmission type display part 20 Surface light source device 25 Light source 28 Reflector 35 Polarization separation film 38 Light diffusion sheet 40 Optical sheet 41 Light incident side surface 42 Connection part 43a Connection part (1st connection part)
43b connection part (second connection part)
45 Main body 46 One surface 47 The other surface 50 First unit shape element 51 Arrangement center 55 Second unit shape element 60 Molding device 70 Mold 72 Mold surface (uneven surface)
74 Concave portion 76 Groove 77a Groove (first groove)
77b Groove (second groove)
78 Notch 79a Notch (first notch)
79b Notch (second notch)

Claims (15)

A sheet-like body,
A plurality of first unit shape elements arranged on one surface of the main body;
A plurality of second unit-shaped elements arranged on the one surface of the main body, each extending in parallel with one direction on the sheet surface of the main body;
One first unit shape element, and one second unit shape element connected to the one first unit shape element from the one direction, and a connection portion that covers at least a part of the connection portion, and
Each of the plurality of first unit shape elements protrudes from the one surface of the main body portion to a position higher than each of the plurality of second unit shape elements and the connection portion.
An optical sheet characterized by that. The connection portion extends in the one direction on the one second unit shape element from the at least part of the connection portion.
The optical sheet according to claim 1. The connection point between the first unit shape element and the second unit shape element that is at least partially covered by the connection portion is such that the second unit shape element is on one side in the one direction with respect to the first unit shape element. It is only the connection point to connect from,
The optical sheet according to claim 1 or 2, wherein A first connecting portion that covers at least a part of a connection portion between the first unit shape element and the second unit shape element connected to the first unit shape element from one side in the one direction;
And a second connecting portion that covers at least a part of a connection portion between the first unit shape element and the second unit shape element connected to the first unit shape element from the other side in the one direction. And
The second unit shape element provided with the first connection portion and the second unit shape element provided with the second connection portion are different positions in the arrangement direction of the second unit shape elements. Located in the
The optical sheet according to claim 1 or 2, wherein The first unit shape element has a shape corresponding to a part of a spheroid or a shape corresponding to a part of a sphere.
The optical sheet according to any one of claims 1 to 4, wherein: A light source;
The optical sheet according to any one of claims 1 to 5, which receives light from the light source,
A surface light source device. Further comprising a polarized light separating film disposed on the light exit side of the optical sheet,
The surface light source device according to claim 6. A transmissive display;
The surface light source device according to claim 6, wherein the surface light source device is disposed to face the transmissive display unit.
A transmissive display device characterized by that. A method for producing an optical sheet according to any one of claims 1 to 5, by molding using a mold,
Supplying a flowable material into the mold;
Curing the material supplied in the mold in the mold;
Removing the cured material from the mold,
In the step of supplying the fluid material, the material is filled in the mold so as to be along a direction corresponding to the one direction of the optical sheet produced by the mold.
An optical sheet manufacturing method characterized by the above. A method for producing the optical sheet according to claim 3 by molding using a mold,
Supplying a flowable material into the mold;
Curing the material supplied in the mold in the mold;
Removing the cured material from the mold,
In the step of supplying the material having fluidity, the material is placed in the mold in a direction and direction corresponding to the direction from the other side to the one side in the one direction of the optical sheet produced by the mold. Filling,
An optical sheet manufacturing method characterized by the above. In the step of removing the material from the mold, the cured material is gradually pulled away from the mold along the one direction.
The method for producing an optical sheet according to claim 9 or 10, wherein: A mold for producing the optical sheet according to any one of claims 1 to 5 by molding,
It is configured as a roll mold with a cylindrical mold surface,
A plurality of recesses corresponding to the first unit shape elements, grooves corresponding to the second unit shape elements,
A notch portion formed at a connection portion between the recess and the groove and corresponding to the connection portion is formed on the mold surface;
The groove extends circumferentially around the center axis of the mold surface, or spirally extends around the center axis of the mold surface,
A type characterized by that. A mold for producing the optical sheet according to claim 4 by molding,
It is configured as a roll mold with a cylindrical mold surface,
A plurality of recesses corresponding to the first unit shape element, a plurality of spiral grooves corresponding to the second unit shape element, and one groove included in the plurality of grooves and a connection portion between the recesses are formed. And a second notch corresponding to the second connection portion formed at a connection portion between the first recess and the recess and the other groove included in the plurality of grooves. Part is formed on the mold surface,
A type characterized by that. A method for producing a mold according to claim 12, comprising:
Forming the recess in a cylindrical mold base;
Forming the groove and the notch in the mold substrate in which the recess is formed by cutting the mold substrate, and in the cutting step, The notch is formed together with the groove by cutting with a cutting means that keeps the cut amount constant.
A method for manufacturing a mold characterized by the above. A method for manufacturing a mold according to claim 13, comprising:
Forming the recess in a cylindrical mold base;
Forming the groove and the notch in the mold substrate in which the recess is formed by cutting the mold substrate, and in the cutting step, By the cutting with a cutting means that keeps the cutting amount constant, the notch is formed together with the groove,
In the cutting step, a plurality of parallel grooves are formed, the cutting direction when forming one of the plurality of grooves, and the formation of another of the plurality of grooves. The direction of cutting is opposite.
A method for manufacturing a mold characterized by the above.

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