JP2011255618A - Method for manufacturing molding die of microlens sheet, molding die of microlens sheet and microlens sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a molding die which is used for manufacturing a microlens sheet having a lens of an unsymmetrical shape.SOLUTION: A resist is applied onto a matrix 51 to form a mask 65 (a step S2). A shape setting process for setting a shape of an opening 66 formed in the mask 65 is carried out (a step S3). The mask 65 is irradiated with laser beams based on the set shape to form two or more openings 66 in the mask 65 (a step S4 and a step S5). The opening 66 set in the step S3 has a first region 66R and a second region 66L which are partitioned by a virtual partitioning line 66y. The virtual partitioning line 66y perpendicularly crosses a virtual bisector 66x which partitions the opening 66 in line symmetry. An area of the first region 66R is smaller than the area of the second region 66L. Since etching speed in the first region 66R becomes smaller than etching speed in the second region 66L, a recessed part 62 of left-right asymmetry is formed in a copper plated layer 64.

Description

  The present invention relates to a method for manufacturing a mold used for manufacturing a microlens sheet. More specifically, the present invention relates to a method for manufacturing a mold used for manufacturing a microlens sheet by embossing.

  A display device represented by a liquid crystal display is required to have high front luminance. Therefore, a microlens sheet for improving the front luminance is laid on the backlight device constituting the display device.

  A plurality of hemispherical convex lenses (microlenses) are arranged in a matrix on one surface (hereinafter referred to as a main surface) of the microlens sheet. Diffused light from the light source is incident on the other surface of the microlens sheet. The microlens collects and emits diffused light incident from the other surface in a direction perpendicular to the main surface.

  The manufacturing method of a microlens sheet is disclosed in the following Patent Documents 1 and 2. The microlens sheet manufacturing method disclosed in Patent Documents 1 and 2 manufactures a microlens sheet by embossing using a roll-shaped mold. However, Patent Documents 1 and 2 below do not disclose a method of manufacturing a mold used for manufacturing an optical sheet having a microlens having an asymmetric shape.

JP 2008-58494 A JP 2010-44229 A

  An object of the present invention is to provide a method of manufacturing a mold used for manufacturing a microlens sheet in which lenses having an asymmetric shape are arranged.

Means for Solving the Problems and Effects of the Invention

  The method for manufacturing a mold for forming a microlens sheet according to the present invention includes an application process, an opening forming process, an etching process, and a shape setting process. In the applying step, a resist is applied to the surface of the mold base material to form a mask made of a resist layer. In the opening forming step, the mask is irradiated with laser to form a plurality of openings in the mask. In the etching step, wet etching is performed on a base material on which a mask having a plurality of openings is formed, and a plurality of recesses corresponding to the plurality of openings are formed on the surface of the base material. In the shape setting step, the shape of the plurality of openings is set before forming the plurality of openings in the mask. The opening set by the shape setting step includes first and second regions. The first and second regions are separated by a virtual dividing line that passes through the center of a virtual bisector that divides the opening in line symmetry and is orthogonal to the virtual bisector. The area of the first region is smaller than the area of the second region.

  Since the area of the first region is smaller than the area of the second region, the etching rate of the base material surface corresponding to the first region is smaller than the etching rate of the base material surface corresponding to the second region. Thereby, since the shape of the recessed part formed in a shaping | molding die can be made asymmetrical, it becomes possible to manufacture the optical sheet by which the micro lens which has an asymmetrical shape is arrange | positioned.

  Preferably, in the opening forming step, virtual bisectors corresponding to the plurality of openings are parallel to each other.

  In this case, the direction of the first region viewed from the second region in each opening is aligned with the direction of the virtual bisector. Since the orientation of the microlens can be controlled, the optical characteristics of the microlens sheet can be controlled.

  Preferably, when one of the directions indicated by the virtual bisector is defined as the first direction, the first region is arranged on the first direction side as viewed from the virtual dividing line.

  In this case, since the direction of the first region viewed from the second region in each opening can be aligned with the first direction, the optical characteristics of the microlens sheet can be controlled.

  Preferably, the opening has a triangular shape. Preferably, in the opening forming step, the opening is set so that a part of the mask remains in the first region. The mold for forming a microlens sheet according to the present invention is manufactured by the above-described manufacturing method.

  The microlens sheet according to the present invention includes a base material portion and a plurality of optical elements. The base material portion has a main surface and a back surface opposite to the main surface. The plurality of optical elements are formed on the main surface side. Each of the plurality of optical elements has an asymmetric shape with respect to an imaginary plane that passes through a vertex having the maximum height from the main surface and is perpendicular to the main surface.

It is a top view of the optical sheet which concerns on 1st Embodiment by this invention. It is KK sectional drawing of the optical sheet shown in FIG. It is an enlarged view of the lens shown in FIG. FIG. 4 is a side view of the lens shown in FIG. 3. It is a schematic diagram which shows the structure of the backlight apparatus using an optical sheet. It is a graph which shows the luminance characteristic of a backlight apparatus. It is a perspective view of the metal mold | die roll used for manufacture of an optical sheet. It is an expanded view of the roll surface of a mold roll. It is MM sectional drawing of the roll surface shown in FIG. It is an enlarged view of the roll surface shown in FIG. It is a flowchart which shows the manufacturing procedure of a shaping | molding die. It is sectional drawing of the preform | base_material of a shaping | molding die. It is a figure which shows the opening formed in a mask. It is an enlarged view of the opening shown in FIG. It is a schematic diagram which shows the structure of the manufacturing apparatus of an optical sheet. It is a figure which shows the opening formed in a mask in 2nd Embodiment by this invention. It is an enlarged view of the opening shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

{First embodiment}
[Structure of optical sheet 1]
FIG. 1 is a plan view of an optical sheet 1 according to the first embodiment of the present invention. 2 is a cross-sectional view taken along the line KK shown in FIG. With reference to FIGS. 1 and 2, the optical sheet 1 is a microlens sheet including a base material portion 11 and a plurality of lenses 12. In FIG. 1 and FIG. 2, the display of reference numerals for some lenses 12 is omitted.

  Hereinafter, the direction indicated by the arrow X shown in FIG. 1 is referred to as a horizontal direction, and the direction indicated by the arrow Y is referred to as a vertical direction. The direction indicated by the arrow Z shown in FIG.

  The base material part 11 is a sheet form or a film form, and is transparent with respect to visible light. The base material part 11 has a main surface 13 and a back surface 14. A plurality of lenses 12 are formed on the main surface 13. The back surface 14 is disposed on the side opposite to the main surface 13. The base material part 11 consists of resin. Examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, acrylic, polyvinyl chloride, and the like.

  The lens 12 is formed at a random position on the main surface 13. The lens 12 has an asymmetric shape. In the present embodiment, the lens 12 has a shape in which an egg is divided in half (hereinafter referred to as a half egg shape). The lens 12 is made of, for example, active energy ray curable resin. The active energy ray-curable resin is cured with active energy rays typified by ultraviolet rays, electron beams, and visible light. The active energy ray curable resin is, for example, a polyester acrylate resin, a urethane acrylate resin, a polyether acrylate resin, an epoxy acrylate resin, a polyester methacrylate resin, a urethane methacrylate resin, or a polyether methacrylate resin.

  FIG. 3 is an enlarged view of the area AR1 shown in FIG. FIG. 4 is a side view of the lens 12 shown in FIG. With reference to FIGS. 3 and 4, in the lens 12, a point having the maximum height from the main surface 13 is defined as a vertex 12a. Here, a horizontal axis 12x, a vertical axis 12y, and a height axis 12z of the lens 12 are defined. The height axis 12z is a straight line that passes through the vertex 12a and is perpendicular to the main surface 13. The horizontal axis 12x is a straight line on the main surface 13 parallel to the arrow X and intersects the height axis 12z. In the plan view of the lens 12, the horizontal axis 12 x is a virtual bisector that divides the lens 12 in line symmetry. The vertical axis 12y is a straight line on the main surface 13 parallel to the arrow Y, and intersects the height axis 12z.

  The lens 12 has an egg shape in plan view. The lens 12 is symmetrical with respect to a virtual plane including the horizontal axis 12x and the height axis 12z. The lens 12 has an asymmetric shape with respect to a virtual plane including the vertical axis 12y and the height axis 12z. That is, the lens 12 has an asymmetric shape with respect to the vertical axis 12y in plan view. Of the edge portion where the lens 12 is in contact with the base material portion 11, the portions that intersect the horizontal axis 12x are referred to as end portions 12b and 12c. The end 12b is located on the right side (the direction of the arrow X) of the paper with respect to the vertex 12a. The end 12c is located on the left side of the paper surface (the direction opposite to the arrow X) from the vertex 12a. A direction in which the end portion 12 b is viewed from the end portion 12 c is a forward direction of the lens 12. Referring to FIG. 1, it is preferable that the forward direction of lens 12 coincides with the direction indicated by arrow X.

  3 and 4, the surface of the lens 12 is divided into a surface 12L and a surface 12R by a virtual surface including the vertical axis 12y. The surface 12L is disposed on the end 12c side. The surface 12R is disposed on the end 12b side. The surface 12R has a gentler curved surface than the surface 12L. And the surface area of the surface 12R is larger than the surface area of the surface 12L. Therefore, the amount of light refracted on the front surface 12R out of the light incident from the back surface 14 of the optical sheet 1 is larger than the amount of light refracted on the front surface 12L.

[Optical characteristics of optical sheet 1]
FIG. 5 is a schematic diagram illustrating a configuration of a backlight device 100 using the optical sheet 1. The backlight device 100 is an edge light type lighting device. The backlight device 100 includes a light source 101, a light guide plate 102, a reflection sheet 103, a prism sheet 2, and an optical sheet 1. The arrow Z direction is the front direction of the backlight device 100.

  The configuration of the prism sheet 2 will be briefly described. The prism sheet 2 includes a base material portion 21 and a plurality of optical elements 22. The base material portion 21 is a transparent film or sheet. A plurality of optical elements 22 extending in the back direction (Y direction) from the front side of the paper surface are formed on the base material portion 21. The transverse shape of the optical element 22 in the XZ plane is asymmetric with respect to the Z-axis direction. The optical element 22 has ridge portions 30 and 40. The ridge portion 30 is disposed on the end 2 a side on the left side of the sheet of the prism sheet 2. The ridge portion 40 is disposed on the right end portion 2 b side of the prism sheet 2 and is lower than the ridge portion 30.

  The ridge portion 30 includes a pair of inclined surfaces 31 and 32. The ridge portion 40 includes a pair of inclined surfaces 41 and 42. The inclined surface 31 is disposed on the end 2 a side and extends to the base material portion 21. The inclined surface 32 is disposed on the end 2b side. The inclined surface 41 is disposed on the end 2a side. The lower end of the inclined surface 32 and the lower end of the inclined surface 41 are connected. The inclined surface 42 is disposed on the end portion 2 b side and extends to the base material portion 21.

  The optical sheet 1 is disposed on the prism sheet 2 so that the surface 12L of the lens 12 is closer to the light source 101 than the surface 12R.

  A light path in the backlight device 100 will be described. The light guide plate 102 guides the light emitted from the light source 101 to the prism sheet 2. The light emitted from the light source 101 enters from the end face of the light guide plate 102. Incident light from the end face travels through the light guide plate 102 and exits from the exit face 102a as outgoing light 54. The outgoing light 54 enters the lower surface of the prism sheet 2. The prism sheet 2 emits outgoing light 54 incident from the lower surface as outgoing light 52 by refracting it in the Z direction on the surface of the optical element 22 (inclined surfaces 32, 41, 42). The optical sheet 1 radiates the outgoing light 52 incident from the back surface 14 in the arrow Z direction by refracting the outgoing light 52 in the arrow Z direction.

  The luminance peak direction of the emitted light 54 is inclined at an angle A54 from the Z-axis direction to the right side of the drawing (the side opposite to the light source 101). Similarly, the luminance peak direction of the emitted light 52 is inclined by an angle A52 from the Z-axis direction to the right side of the drawing (the side opposite to the light source 101). The luminance peak direction of the emitted light 53 is inclined at an angle A53 from the Z-axis direction to the right side of the drawing. The peak direction of each of the emitted lights 54 to 53 approaches the direction indicated by the arrow Z as it proceeds to the optical sheet 1 side. That is, the relationship between the angles A52 to A54 is angle A53 <angle A52 <angle A54.

  FIG. 6 is a graph showing the luminance characteristics of the backlight device 100 having the configuration shown in FIG. Referring to FIG. 6, the solid line indicates the luminance distribution of outgoing light 53 and corresponds to the luminance characteristics of backlight device 100. A broken line is a luminance characteristic of a backlight device using a conventional microlens sheet instead of the optical sheet 1. The luminance characteristic peak of the backlight device 100 using the optical sheet 1 (the luminance peak of the emitted light 53) is closer to the front direction (viewing angle 0 °) than the luminance characteristic peak of the conventional backlight device.

  As described above, the optical sheet 1 is disposed such that the surface 12L of the lens 12 is closer to the light source 101 than the surface 12R. Therefore, the optical sheet 1 can receive the incident light 52 inclined by the angle A52 and can make the outgoing light 53 close to the Z direction.

  Further, the plurality of lenses 12 of the optical sheet 1 are randomly arranged. For this reason, the viewing angle can be kept wide to some extent. Furthermore, the generation of moire is suppressed.

  As described above, by using the optical sheet 1 of the present embodiment for an illumination device such as the backlight device 100, the luminance characteristics are improved as described above.

[Structure of mold for optical sheet 1]
The optical sheet 1 is manufactured by embossing using a mold. Hereinafter, the structure of the shaping | molding die used for manufacture of the optical sheet 1 is demonstrated.

  FIG. 7 is a perspective view of a mold 50 used for manufacturing the optical sheet 1. With reference to FIG. 7, the mold 50 is a roll-shaped mold. The mold 50 includes a roll body 60 and a roll shaft 70. The roll body 60 is cylindrical. The roll shaft part 70 is arranged coaxially with the roll body part 60. The roll body 60 has a roll surface 61. An arrow C indicates the circumferential direction of the roll body 60. An arrow A indicates the axial direction of the roll body 60. An arrow R indicates the radial direction of the roll body 60.

  FIG. 8 is a development view of the roll surface 61 and corresponds to a view of the roll surface 61 as viewed from the direction of the arrow R. Arrows C and A correspond to arrows X and Y (see FIG. 1), respectively. A plurality of recesses 62 corresponding to the shape of the lens 12 are formed on the roll surface 61 at random positions. Two to three recesses 62 are formed so as to be connected. This is because, as shown in FIG. 1, in the optical sheet 1, two or more lenses 12 may be connected to each other.

  FIG. 9 is a cross-sectional view of the roll surface 61 shown in FIG. FIG. 10 is an enlarged view of the area AR2 shown in FIG. Referring to FIG. 9, a copper plating layer 64 is formed on the surface of roll body 60. The roll surface 61 corresponds to the exposed surface of the copper plating layer 64. The recess 62 is formed in the copper plating layer 64.

  With reference to FIGS. 9 and 10, the recess 62 is a recess corresponding to the shape of the lens 12. The deepest point in the recess 62 is defined as the deepest point 62a. In the recess 62, a horizontal axis 62x and a vertical axis 62y are defined. The horizontal axis 62x is a straight line parallel to the arrow C arranged on the roll surface 61, and passes right above the deepest point 62a.

  The vertical axis 62y is a straight line parallel to the arrow A arranged on the roll surface 61, and passes directly above the deepest point 62a. The horizontal axis 62x and the vertical axis 62y correspond to the horizontal axis 12x and the vertical axis 12y of the lens 12, respectively. The recess 62 has an asymmetrical shape with respect to a virtual plane that includes the longitudinal axis 62 y and is perpendicular to the roll surface 61.

  Of the contour corresponding to the boundary between the roll surface 61 and the recess 62, the intersections with the horizontal axis 62x are defined as end portions 62b and 62c. The end portion 62b corresponds to the end portion 12b of the lens 12, and is located on the right side of the drawing surface from the deepest point 62a. The end portion 62c corresponds to the end portion 12c of the lens 12, and is located on the left side of the drawing with respect to the deepest point 62a. The direction in which the end 62b is viewed from the end 62c is the forward direction of the recess 62. The forward direction of the recess 62 and the forward direction of the lens 12 coincide.

  Referring to FIGS. 9 and 10, the surface of recess 62 is divided into a surface 62R and a surface 62L by a virtual surface including a longitudinal axis 62y. The surface 62R is a curved surface, and is disposed on the right side of the drawing surface from the deepest point 62a. The surface 62L is a curved surface, and is disposed on the left side of the drawing from the deepest point 62a. The surface 62R has a gentler curved surface than the surface 62L. The surface area of the surface 62R is larger than the surface area of the surface 62L.

[Method for Manufacturing Mold 50]
Hereinafter, a method for manufacturing the mold 50 will be described. FIG. 11 is a flowchart showing the manufacturing procedure of the mold 50. FIG. 12 is a cross-sectional view of a base material 51 that is a material of the mold 50. FIG. 12 shows a cross section of the base material 51 after the development process (step S5, see FIG. 11), and corresponds to the MM cross section of the roll body 60 of the mold 50.

  With reference to FIG.11 and FIG.12, the column-shaped base material 51 is prepared first (step S1). The base material 51 includes a roll body 60 and a roll shaft 70. A copper plating layer 64 is already formed on the circumferential surface of the roll body 60.

  In the coating process (step S2), a resist is applied to the surface of the base material 51 to form a mask 65 made of a resist layer. That is, the mask 65 is formed on the copper plating layer 64. As the resist, for example, tetramethylammonium hydroxide can be used. At the stage where the coating process in step S2 is completed, the recess 62 and the opening 66 are not formed.

  In the shape setting step (step S3), the shape of the opening 66 formed in the mask 65 is set. That is, a region for irradiating the mask 65 with the laser is set for a laser irradiation apparatus (not shown).

  In the exposure step (step S4), the mask 65 is irradiated with laser based on the shape of the opening 66 set in the shape setting step (step S3).

  Next, in the developing process (step S5), the resist in the region irradiated with the laser in the mask 65 is removed. Thereby, the opening 66 is formed (see FIG. 12). A developer corresponding to the material used for the resist is used to remove the resist. That is, the exposure process (step S4) and the development process (step S5) are opening forming processes in which the mask 65 is irradiated with laser to form a plurality of openings 66 in the mask 65.

  When laser ablation exposure is used for exposure of the mask 65, the exposed area becomes the opening 66. In this case, the developing process (step S5) can be omitted.

  Referring to FIG. 13, an opening 66 formed in mask 65 is shown. For convenience of explanation, the position of the recess 62 is indicated by a broken line. The openings 66 have a triangular shape and are arranged at random positions on the mask 65.

  FIG. 14 is an enlarged view of the opening 66. For convenience of explanation, FIG. 14 shows the recess 62 and each part of the recess 62. Referring to FIG. 14, the opening 66 has a triangular shape. More specifically, a part of the three sides of the triangle is stepped. In this specification, the triangle shape includes those having stepped sides. The step-shaped side is formed because the resolution of a laser irradiation apparatus (not shown) is limited to a rectangular shape. Each side of the opening 66 may be a straight line or a curved line.

  The opening 66 includes a first region 66R and a second region 66L. The first region 66R and the second region 66L are separated by a virtual dividing line 66y. The virtual dividing line 66y passes through the midpoint 66M of the virtual bisector 66x and is orthogonal to the virtual bisector 66x. The virtual bisector 66x divides the opening 66 in line symmetry. The virtual bisector 66x is a part of the horizontal axis 62x that connects the end 62b and the end 62c (see FIG. 10).

  The area of the first region 66R is smaller than the area of the second region 66L. More specifically, the first region 66R has a triangular shape, and the second region 66R has a trapezoidal shape. The opening 66 is divided asymmetrically by a virtual dividing line 66y.

  The virtual bisector 66x in each opening 66 is parallel to each other. The direction indicated by the arrow C is the first direction. The first region 66R is disposed on the first direction side of the opening 66. The second region 66L is disposed on the opposite side of the opening 66 from the first direction side. That is, the vertex 66A is arranged on the right side of the drawing with respect to the virtual dividing line 66y. The bottom side 66S is arranged on the left side of the drawing with respect to the virtual dividing line 66y. Thereby, it becomes possible to align the forward direction of each recessed part 62. FIG.

  After the development process (step S5), an etching process is performed (step S6). In the etching step, wet etching is performed on the base material 51 on which the mask 65 having the plurality of openings 66 is formed, and a plurality of recesses 62 corresponding to the plurality of openings 66 are formed on the surface of the base material 51. A copper plating layer 64 is formed on the surface of the base material 51. Therefore, as the etching solution, for example, a cupric chloride solution, a ferric chloride solution, a sulfuric acid / hydrogen peroxide etching solution, or the like is used.

  By wet etching, not only the copper plating layer 64 exposed through the opening 66 but also the copper plating layer 64 under the mask 65 around the opening 66 is etched. Therefore, even if the opening 66 is triangular, an egg-shaped recess 62 (see FIG. 8) is formed in plan view.

  Referring to FIG. 14, the deepest point 62a and the midpoint 66M of the virtual bisector 66x do not necessarily match. Since the area of the first region 66R is smaller than that of the second region 66L, the etching rate of the copper plating layer 64 corresponding to the second region 66L is larger than the etching rate of the copper plating layer 64 corresponding to the first region 66R. It is to become. Further, due to the difference in etching rate between the first region 66R and the second region 66L, a left-right asymmetrical recess 62 having a surface 62R having a gentle slope and a surface 62L having a steep slope is formed (FIG. 9). reference).

  Finally, as a removing process (step S7), the mask 65 formed on the surface of the base material 51 is removed. Thereby, all the manufacturing processes of the shaping | molding die 50 are complete | finished. Note that a nickel layer may be formed on the copper plating layer 64 by an electroless plating method after the removing step (step S7). The nickel layer has a role of surface protection.

  Through the above steps, the mold 50 is easily manufactured using the mask 65 having the opening 66.

[Manufacturing process of optical sheet 1]
The optical sheet 1 is manufactured by embossing using the mold 50 described above. Referring to FIG. 15, the optical sheet 1 manufacturing apparatus 320 includes a base film roll 321, a take-up roll 302, a nip roll 303, a backup roll 304, a shielding plate 305, an irradiation device 306, and a forming mold. 50 and a coating device 308. The base film roll 321 has a cylindrical shape, and a base film corresponding to the base part 11 (hereinafter referred to as the base film 11) is wound around the roll surface.

  The manufacturing method of the optical sheet 1 using the manufacturing apparatus 320 is as follows. First, a base film roll 321 around which the base film 11 is wound is prepared and placed at a predetermined position. And liquid active energy ray hardening resin is prepared. The active energy ray curable resin is a material of the lens 12.

  The substrate film 11 is unwound from the disposed substrate film roll 321, and the substrate film 11 is conveyed toward the mold 50.

  The coating device 308 is a die coater or the like. A liquid active energy ray curable resin is applied onto the roll surface 61 from the coating device 308. The applied active energy ray curable resin spreads on the roll surface 61 to form the active energy ray curable resin layer 200. The active energy ray cured resin layer 200 is uncured.

  When the base film 11 passes between the nip roll 303 and the mold 50, the base film 11 is pressed against the mold 50 by the nip roll 303. At this time, the base film 11 contacts the active energy ray-curable resin layer 200 on the roll surface 61. As a result, the active energy ray curable resin layer 200 is sandwiched between the base film 11 and the roll surface 61 of the mold 50. At this time, the active energy ray curable resin is filled in each recess 62.

  Next, the active energy ray curable resin layer 200 is irradiated from below the mold 50 by the irradiation device 306. The active energy ray-curable resin layer 200 sandwiched between the base film 11 and the roll surface 61 is cured, and the lens 12 is formed. The shielding plate 305 diffuses the active energy rays so that the active energy rays are irradiated onto the active energy ray curable resin layer 200 after the unevenness of the roll surface 61 is reliably transferred to the active energy ray curable resin layer 200. To prevent.

  The optical sheet 1 manufactured by the above steps is peeled off from the mold 50 and conveyed toward the take-up roll 302 via the backup roll 304. And it winds with the winding roll 302. FIG. The optical sheet 1 is manufactured through the above steps.

  As described above, in the present embodiment, the opening 66 including the first region 66R and the second region 66L is formed in the mask 65 by the exposure process (step S4) and the development process (step S5). The area of the first region 66R is smaller than the area of the second region 66L. In the etching step (step S6), the etching rate in the first region 66R is smaller than the etching rate in the second region 66L. Thereby, the shaping | molding die 50 which has the recessed part 62 of an asymmetrical shape can be manufactured.

{Second Embodiment}
A second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the shape of the opening set by the shape setting step (see step S3, FIG. 11) in the manufacturing process of the mold 50 is different from that of the first embodiment. Hereinafter, the present embodiment will be described in detail with a focus on differences from the first embodiment.

  FIG. 16 is a diagram showing an opening 67 formed in the mask 65 in the present embodiment. Referring to FIG. 16, the opening 67 has a circular shape unlike the first embodiment. The openings 67 are arranged at random positions on the mask 65.

  FIG. 17 is an enlarged view of the opening 67. Referring to FIG. 17, the periphery of the opening 67 has a stepped shape in order to receive the limitation of the resolution of the laser device. Thus, the shape of the opening 67 may not be an accurate circle. The “circular shape” referred to in this specification includes a step whose circumference is as shown in FIG.

  A virtual bisector 67x and a virtual dividing line 67y at the opening 67 are defined. The virtual bisector 67x is a straight line parallel to the arrow C, and divides the opening 67 line-symmetrically. The virtual bisector 67x is a part of the horizontal axis 62x. The virtual dividing line 67y is a straight line that passes through the midpoint 67M of the virtual bisector 67x and is orthogonal to the virtual bisector 67x. Similar to the first embodiment, the opening 67 is divided into a first region 67R and a second region 67L by a virtual dividing line 67y.

  In FIG. 17, the mask 65 remaining inside the opening 67 is shown in a lattice pattern. A part of the mask 65 remains in the first region 67R. On the other hand, the mask 65 does not remain in the second region 67L. For this reason, the area of the first region 67R is smaller than the area of the second region 67L. That is, in the shape setting step (step S3), the laser irradiation pattern is set so that a part of the mask 65 remains in the first region 67R.

  Similar to the first embodiment, since the area of the first region 67R is smaller than the area of the second region 67L, the etching rate in the first region 67R is smaller than the etching rate in the second region 67L. For this reason, even when the concave portion 62 is formed based on the opening 67, the position of the deepest point 62a and the position of the midpoint 66M are not necessarily coincident. In addition, since the etching rate is different between the first region 67R and the second region 67L, the recesses 62 are formed in the base material 51 even when a mask having the opening 67 is used. That is, the opening 67 forms a recess 62 having a surface 62R having a gentle slope and a surface 62L having a steep slope.

  As described above, in the present embodiment, the first region 67R in which part of the mask 65 remains and the second region 67L in which the mask 65 does not remain are formed. Thereby, since the etching rate of the copper plating layer 64 corresponding to each of the first region 67R and the second region 67L can be controlled, it is possible to create the mold 50 having the left and right asymmetric recesses 62. .

  In the present embodiment, the shape of the opening 67 is circular, but is not limited thereto. The shape of the opening 67 can be appropriately changed according to the shape of the lens 12. In the above-described embodiment, the example in which the roll-shaped mold 50 is used for manufacturing the optical sheet 1 has been described. However, the optical sheet 1 may be manufactured using a flat plate-shaped mold 50 instead of the roll-shaped mold 50.

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

DESCRIPTION OF SYMBOLS 1 Optical sheet 11 Base material part 12 Lens 12a Vertex 13 Main surface 14 Back surface 50 Mold 51 Base material 60 Roll body part 61 Roll surface 62 Recessed part 62a Deepest point 65 Mask 66, 67 Opening 66R, 67R 1st area | region 66L, 66R 1st area | region 2-region 66x, 67x Virtual bisector 66y, 67y Virtual dividing line 70 Roll shaft part

Claims (7)

A method of manufacturing a mold for forming a microlens sheet,
An application step of applying a resist to the surface of the base material of the mold and forming a mask made of a resist layer;
An opening forming step of irradiating the mask with a laser to form a plurality of openings in the mask;
Etching to perform wet etching on the base material on which the mask having the plurality of openings is formed, and to form a plurality of recesses corresponding to the plurality of openings on the surface of the base material,
A shape setting step of setting the shapes of the plurality of openings before forming the plurality of openings in the mask;
The opening set by the shape setting step is
Including first and second regions separated by a virtual dividing line that passes through the center of a virtual bisector that divides the opening in line symmetry and is orthogonal to the virtual bisector,
The manufacturing method of the shaping | molding die of the micro lens sheet whose area of the said 1st area | region is smaller than the said 2nd area | region. A method for producing a mold for a microlens sheet according to claim 1,
In the opening forming step, the plurality of virtual bisectors corresponding to each of the plurality of openings are parallel to each other, and the method of manufacturing a microlens sheet mold. A method for producing a mold for a microlens sheet according to claim 2,
When one of the directions indicated by the virtual bisector is defined as a first direction, the first region is disposed on the first direction side when viewed from the virtual dividing line. A method for producing a mold for a microlens sheet according to claim 3,
The method for manufacturing a mold for forming a microlens sheet, wherein the opening has a triangular shape. A method for producing a mold for a microlens sheet according to claim 3,
In the opening forming step, the opening is set so that a part of the mask remains in the first region.   A mold used for manufacturing a microlens sheet manufactured by the manufacturing method according to any one of claims 1 to 5. A microlens sheet manufactured using the mold according to claim 6,
A base material portion having a main surface and a back surface opposite to the main surface;
A plurality of the optical elements formed on the main surface side,
The plurality of optical elements are:
A microlens sheet that has an asymmetric shape with respect to a virtual plane that passes through a vertex having a maximum height from the main surface and is perpendicular to the main surface.

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