JP5515543B2 - Optical sheet manufacturing apparatus and optical sheet manufacturing method - Google Patents

Description

  The present invention relates to a liquid crystal backlight device having a light source such as a fluorescent tube, LED, EL, or the like, an optical sheet mounted on a lighting device and used for illumination light path control, a backlight unit, and a display device. In particular, the present invention relates to an improvement in an optical sheet manufacturing apparatus used for illumination optical path control in an image display apparatus typified by a flat panel display.

In recent years, display devices using TFT-type liquid crystal panels and STN-type liquid crystal panels have been commercialized mainly in color notebook PCs (personal computers) in the OA field, for example.
Such a display device employs a so-called backlight system in which a light source is arranged on the back side of the liquid crystal panel and the liquid crystal panel is illuminated with light from the light source.

  The backlight units used in this type of backlight system can be broadly divided into multiple light sources such as cold cathode fluorescent lamps (CCFL) within a flat light guide plate made of acrylic resin with excellent light transmission. There are a “light guide plate light guide method” (so-called edge light method) and a “direct type method” that does not use a light guide plate.

As a display device on which a light guide plate light guide type backlight unit is mounted, for example, the one shown in FIG. 7 is generally known.
This display device includes a liquid crystal panel 131 sandwiched between polarizing plates 130 and 132, and a light guide plate 134 made of a transparent base material such as a substantially rectangular plate-like PMMA (polymethylmethacrylate) or acrylic on the back side thereof. A diffusion film (diffusion layer) 133 is provided between the upper surface (light emitting side) of the light guide plate 134 and the polarizing plate 132 on the rear side.

  Also, on the back side of the light guide plate 134, a scattering reflection pattern portion (not shown) for scattering and reflecting the light introduced into the light guide plate 134 so as to be uniform in the direction of the liquid crystal panel 131 is printed. A reflective film (reflective layer) 137 is provided on the further back side of the scattering reflection pattern portion.

  Further, a light source lamp 136 is attached to one side end of the light guide plate 134 so as to cover the back side of the light source lamp 136 in order to make the light of the light source lamp 136 enter the light guide plate 134 efficiently. A high-reflectance lamp reflector 135 is provided. The scattering reflection pattern portion is formed by printing a mixture of white titanium dioxide (TiO 2) powder in a transparent adhesive or the like in a predetermined pattern, for example, a dot pattern, and drying and forming the light guide plate 134. A directivity is imparted to the light incident on the inside of the light to guide it to the light exit surface side, thereby increasing the brightness.

  Recently, prism films (prism layers) 138 and 139 having a light condensing function are provided between the diffusion film 133 and the liquid crystal panel 131 in order to improve the light utilization efficiency and increase the luminance. Has been proposed. The prism films 138 and 139 are for emitting the light emitted from the light emitting surface of the light guide plate 134 and diffused by the diffusion film 133 to the effective display area of the liquid crystal panel 131 with high efficiency.

  On the other hand, the direct type backlight unit is used in a display device such as a large liquid crystal TV in which it is difficult to use a light guide plate. As an example using this backlight unit, for example, a display as shown in FIG. Devices are generally known.

  In this display device, a liquid crystal panel 131 sandwiched between polarizing plates 130 and 132 is provided, and a light source 136 made of a fluorescent tube or the like is provided on the back side thereof. And the light radiate | emitted from the light source 136 is diffused with the diffusion film 133, and is condensed on the effective display area of the liquid crystal panel 131 with high efficiency. In order to efficiently use the light from the light source 136 as illumination light, a reflector 139 is disposed on the back surface of the light source 136.

  In a display device equipped with such a direct type backlight unit, light scattering particles are blended to prevent the occurrence of uneven brightness by preventing the light source image (lamp image) from being seen on the display screen. The formed resin plate is provided as a light diffusion plate for diffusing light emitted from the light source.

This light diffusing plate is required to have a high transmission and high diffusion function of preventing the lamp image from being visually recognized by diffusing the light while transmitting the light. Trial and error is performed by changing the type, particle size, and blending amount. In this regard, in the case of a light diffusing plate uniformly dispersed at a certain concentration by using spherical particles as light scattering particles to be blended with the resin, it has been confirmed that the light diffusing characteristic widens the viewing angle. Yes. Therefore, since the lamp image is visually recognized in a state where only the bright part is spread, stripe-like luminance unevenness occurs between the wide bright part and the narrow dark part.
Therefore, in order to suppress this luminance unevenness, it is necessary to reduce the light transmittance so that the difference between light and dark becomes difficult to be visually recognized. As a result, there is a problem that the front luminance becomes insufficient.

  Further, in the liquid crystal display device shown in FIG. 8, since the control of the viewing angle is entrusted only to the diffusibility of the diffusion film 133, the control is difficult, and the central portion in the front direction of the liquid crystal display screen is bright, The characteristic that becomes darker toward the periphery cannot be avoided. For this reason, when the liquid crystal display screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

  Therefore, as one method for solving such a problem, a brightness enhancement film (BEF), which is a registered trademark of 3M USA, is disposed above the backlight illumination light source 136, and further, BEF There has been proposed a method of improving the front luminance by arranging a light diffusion film (not shown) on the light emitting surface side above (see, for example, Patent Documents 1 to 5). BEF is a film in which unit prisms having a triangular cross section are arranged at a constant pitch in one direction on the upper surface of a transparent substrate. This unit prism has a large size (pitch) compared to the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” to the viewer, or “recycle”. To do.

  When using the display device (when observing), the BEF increases the on-axis brightness by reducing the off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the viewer, and is generally on the normal direction side with respect to the display screen. When this BEF is used alone, the repetitive array structure of unit prisms is arranged in only one direction, so that only the direction change or recycling in the parallel direction is possible. Therefore, in order to control the luminance of the display light in the horizontal and vertical directions, generally, two sheets are combined and used so that the parallel directions of the unit prism groups are substantially orthogonal to each other.

  However, when the BEF is used together with the light diffusing plate as described above, the front luminance can be improved by increasing the light intensity in the viewer's visual direction, but the light component due to refraction acts in the viewer's visual direction. There is a problem that the side lobe light is unnecessarily emitted in the lateral direction without traveling.

  For this reason, the luminance distribution emitted from the BEF has the highest front luminance at an angle of 0 ° with respect to the visual direction of the viewer, while a small light intensity peak occurs in the vicinity of ± 90 ° from the front, and the luminance distribution is efficiently collected. There was a problem that light could not be performed.

  In addition, when only the luminance in the front direction is excessively improved, the peak width of the curve of the luminance distribution becomes extremely narrow, and the viewing area is extremely limited. Therefore, in order to increase the peak width appropriately, it is necessary to newly provide a light diffusion film which is a separate member from BEF (prism sheet), which increases the number of parts. Therefore, not only does it lead to an increase in material cost, but the operation for assembling the display becomes complicated, which is not preferable.

  Therefore, recently, for the purpose of cost reduction as in Patent Document 6, the optical control element having the diffusion function, the optical control element having the light collecting function, and the function of the rigid light-transmitting substrate are integrated, Inventions that reduce the number of parts have also been made. By consolidating functions in this way, it is possible to simplify the manufacturing process, reduce costs, and reduce the thickness.

Japanese Patent No. 3374316 Japanese Patent No. 3684587 Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2006-106197 A

  As described above, conventionally, resin sheets having respective functions such as diffusion and light collection are laminated or integrated via an adhesive layer to satisfy desired conditions such as improvement of luminance and elimination of luminance unevenness. Resin plates and resin sheets were created.

However, due to the recent demand for reducing the number of components for the purpose of further thinning and cost reduction of liquid crystal TVs, it has become necessary to integrally form resin plates and resin sheets with various functions thinner and cheaper. ing.
As a method of integrally molding, there is a method of molding a diffusion plate or a diffusion sheet by an injection method such as an extrusion molding method or an injection molding method using an apparatus in which the distance from the die to the molding roll (air gap) is set short. In this case, there is a problem that deformation or damage such as warpage or deflection occurs in the molded product due to residual stress at the time of molding.

The present invention was made in view of such problems, an optical sheet manufacturing apparatus and method without deformation or damage is caused by the warpage and deflection of the molded article, as well as to provide the optical sheet manufacturing how For the purpose.

In order to solve the above problems, the present invention proposes the following means.
That is, the optical sheet manufacturing apparatus according to the present invention is an optical sheet manufacturing apparatus that continuously manufactures an optical sheet that has fine irregularities on both sides and is used for illumination optical path control by extrusion molding. An extrusion die that extrudes the discharged resin into a sheet shape and discharges, and an uneven forming portion that forms the fine uneven shape on both sides by sandwiching the sheet-shaped resin, and between the extrusion die and the uneven forming portion An internal stress relaxation section through which the sheet-like resin extruded from the extrusion die passes for a predetermined time is provided, and a heating facility for heating the internal stress relaxation section is provided.

According to the optical sheet manufacturing apparatus having such characteristics, it is possible to prevent the sheet-like resin discharged from the extrusion die from solidifying in a state having an internal stress.
That is, the sheet-like resin discharged from the extrusion die moves through the internal stress relaxation heated by the heating equipment over a predetermined time. As a result, the sheet-like resin is left in a molten state without being solidified for a predetermined time, so that the stress remaining inside can be relieved. Accordingly, it is possible to avoid the occurrence of residual stress in the manufactured optical sheet.

  The optical sheet manufacturing apparatus according to the present invention is characterized in that the internal stress relaxation section is linear.

Here, when the sheet-shaped resin discharged from the extrusion die is configured to be conveyed in a curved shape while being held on the outer peripheral surface of the conveyance roll, for example, the sheet-shaped resin is bent in an arc shape. Therefore, a new stress is generated in the resin, and the stress remains in the manufactured optical sheet.
In this regard, in the present invention, since the sheet-like resin discharged from the extrusion die passes through the linear internal stress relaxation section, the sheet-like resin is not bent, and the internal stress is renewed. It will never happen.

  Furthermore, in the optical sheet manufacturing apparatus according to the present invention, the length between the front end and the rear end of the internal stress relaxation section is preferably set in a range of 3 cm or more and 254 cm or less.

  Moreover, in the optical sheet manufacturing apparatus according to the present invention, the internal stress relaxation section is arranged to be inclined.

  According to the optical sheet manufacturing apparatus having such characteristics, the pressure of the resin itself acts on the sheet-like resin passing through the internal stress relaxation section toward the lower side in the inclination direction of the internal stress relaxation section. Become. That is, since a uniform pressure can be applied along the extending direction of the sheet-like resin, internal stress in the sheet-like resin can be removed.

  Furthermore, in the optical sheet manufacturing apparatus according to the present invention, it is preferable that the inclination of the internal stress relaxation section is an upward gradient or a downward gradient with an inclination angle of 45 ° or less with respect to the horizontal plane.

When the inclination angle of the internal stress relaxation section exceeds 45 °, an excessive pressure is applied to the sheet-like resin along the extending direction of the sheet-like, and new internal stress is generated. Further, the sheet-shaped resin may slide down and be folded over.
In this regard, the inconvenience can be corrected by setting the inclination angle of the internal stress relaxation section to 45 ° or less.

  Moreover, in the optical sheet manufacturing apparatus according to the present invention, the heating equipment is configured to reduce the internal stress so that a temperature difference of the sheet-like resin between a front end and a rear end of the internal stress relaxation section is within 5 ° C. It is preferable to heat the section.

According to the optical sheet manufacturing apparatus having such characteristics, the internal stress can be reliably relaxed without solidifying the sheet-like resin in the internal stress relaxation zone.
Also, if the temperature difference before and after the internal stress relaxation section exceeds 5 ° C, the melt viscosity of the resin W will change greatly, the viscosity will decrease due to the high temperature, the resin will leak before molding, Is low, the viscosity is lowered, and the problem of solidifying at a low temperature while keeping the internal stress occurs, but this problem can be avoided.

  Furthermore, the optical sheet manufacturing apparatus according to the present invention is characterized in that an arrangement interval between the rear end of the internal stress relaxation section and the concavo-convex molded portion is set within 10 cm.

  According to the optical sheet manufacturing apparatus having such a feature, the sheet-shaped resin that has passed through the internal stress relaxation section can reach the concavo-convex molded portion without solidifying. Thereby, it becomes possible to shape | mold a fine uneven | corrugated shape reliably on both surfaces of a sheet-like resin.

  Moreover, the optical sheet manufacturing apparatus according to the present invention includes a first plate having a first mold shape that is opposite to the fine unevenness shape of one surface of the optical sheet, and the fine surface of the other surface of the optical sheet. A second plate having a second mold shape opposite to the concavo-convex shape, and the sheet-like resin is sandwiched between the first plate and the second plate in the concavo-convex molding portion, thereby forming the sheet shape The fine concavo-convex shape is transferred onto both surfaces of the resin.

  Thereby, a fine uneven | corrugated shape can be shape | molded reliably on both surfaces of a sheet-like resin.

  In the optical sheet manufacturing apparatus of the present invention, the first plate forms a belt shape having the first mold shape on a belt surface, and the sheet-like resin is discharged onto the belt surface to cause the internal stress. The second plate is moved to move through the relaxation section and the concavo-convex molded portion, and the second plate forms a roll shape having the second mold shape on the roll surface, and is arranged in the concavo-convex molded portion.

  According to the optical sheet manufacturing apparatus having the above characteristics, the sheet-like resin extruded from the extrusion die is discharged onto the belt surface of the first plate, and the first plate moves through the internal stress relaxation section to move the sheet. The internal stress of the resin is relieved. Then, after passing through the internal stress relaxation section, the first plate reaches the concave-convex molded portion, and in this case, the sheet-like resin on the belt surface of the first plate contacts the roll surface of the second plate. By doing so, the sheet-like resin is sandwiched between the first plate and the second plate. As a result, the fine uneven shape can be reliably transferred to both surfaces of the sheet-like resin.

  Furthermore, in the optical sheet manufacturing apparatus of the present invention, it is preferable that the belt surface of the first plate is heated before the sheet-like resin is discharged.

  According to the optical sheet manufacturing apparatus having such characteristics, when the sheet-like resin is discharged onto the belt surface of the first plate belt, the heat of the sheet-like resin is taken away by the belt surface and the resin is solidified. Can be prevented.

  In the optical sheet manufacturing apparatus according to the present invention, at least one of the first mold shape and the second mold shape has a 10-point average roughness Rz of 50 μm to 200 μm and an arithmetic average roughness Ra of 3.0 μm or more. It is preferable that it is set in the range of 1000 μm or less.

  Furthermore, in the optical sheet manufacturing apparatus according to the present invention, at least one of the first mold shape and the second mold shape has a prism shape inverse shape, and the prism apex angle of the inverse shape is 40 to 70 °, The prism interval may be set within a range of 20 to 200 μm.

  In the optical sheet manufacturing apparatus according to the present invention, at least one of the first mold shape and the second mold shape is a polygonal pyramid shape, a conical shape, a polygonal frustum shape, a truncated cone shape, a polygonal columnar shape, a cylinder. Shape, rectangular parallelepiped shape, hemispherical shape, ellipsoidal shape, cylindrical shape, or the reverse shape of any combination of these shapes

  Furthermore, in the optical sheet manufacturing apparatus according to the present invention, it is preferable that at least one of the first mold shape and the second mold shape is regularly arranged.

  Moreover, in the optical sheet manufacturing apparatus according to the present invention, at least one of the first mold shape and the second mold shape may be non-uniformly arranged.

  An optical sheet manufacturing method according to the present invention is an optical sheet manufacturing method for continuously manufacturing an optical sheet having fine irregularities on both sides and used for illumination optical path control by extrusion, and is heat-melted resin An extrusion process for extruding the sheet-like resin, and an uneven forming process for forming the fine uneven shape on both sides by sandwiching the sheet-like resin, and between the extrusion process and the uneven forming process, by the extrusion process An internal stress relaxation step for moving the extruded sheet-like resin linearly over a predetermined time is provided, and at the same time as the internal stress relaxation step, the sheet-like resin is brought to substantially the same temperature as during the heating and melting. A heating step for heating is provided.

According to the optical sheet manufacturing method having such characteristics, it is possible to prevent the sheet-like resin extruded by the extrusion process from solidifying in a state having internal stress.
In other words, the sheet-like resin moves over the heated internal stress relaxation over a predetermined time. As a result, the sheet-like resin is allowed to stand for a predetermined time in a molten state without solidifying, so that the stress remaining inside can be relieved. Accordingly, it is possible to avoid the occurrence of residual stress in the manufactured optical sheet.

  According to the optical sheet manufacturing apparatus, the optical sheet, the backlight unit, the display device, and the optical sheet manufacturing method of the present invention, it is possible to prevent the molten sheet-like resin from solidifying in a state having internal stress. it can. Therefore, it is possible to avoid the deformation and breakage due to warping or bending of the optical sheet which is a molded product.

It is a schematic block diagram of the optical sheet manufacturing apparatus which concerns on embodiment. It is sectional drawing orthogonal to the 1st plate belt in an internal stress relaxation area. It is a flowchart of the optical sheet manufacturing method which concerns on embodiment. It is a schematic block diagram of the optical sheet manufacturing apparatus of a comparative example. It is a longitudinal cross-sectional view which shows schematic structure of the optical sheet which concerns on embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the backlight unit and display apparatus which concern on embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the display apparatus by which the backlight unit of a light-guide plate light guide system is mounted. It is a longitudinal cross-sectional view which shows schematic structure of the display apparatus by which the direct type backlight unit is mounted. It is a figure explaining the deflection amount of the optical sheet in an Example.

  Hereinafter, embodiments of an optical sheet manufacturing apparatus, an optical sheet, a backlight unit and a display device, and an optical sheet manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings.

(Optical sheet manufacturing apparatus, optical sheet manufacturing method)
First, an optical sheet manufacturing apparatus and an optical sheet manufacturing method according to the embodiment will be described. The optical sheet manufacturing apparatus 1 according to the present embodiment is used when an optical sheet 100 having fine uneven shapes 101 and 102 on both sides is manufactured by extrusion molding.

  As shown in FIG. 1, the optical sheet manufacturing apparatus 1 includes an extrusion die 10, a first plate belt (first plate) 20 that is driven by a guide roll 23, and a second plate roll that is disposed in the concavo-convex forming portion 30. (2nd edition) 31 and the press roll 33, and the conveyance roll 40 arrange | positioned in the downstream of the uneven | corrugated shaping | molding part 30 are provided. Further, an internal stress relaxation section 50 is provided between the extrusion die 10 and the concavo-convex molded portion 30, and an external heating equipment (heating equipment) 51 is provided in the internal stress relaxation section 50.

The extrusion die 10 is a stack of an extruder 11 that heats and melts the resin W and extrudes it, and a feed block die and a manifold die that form the resin W extruded from the extruder 11 into a sheet shape and discharge it downward. It consists of a die 12 of the mold. As a result, the resin that is the material of the optical sheet 100 is heated and melted by the extruder 11, and the resin W is extruded through the die 12, whereby the sheet-shaped resin W is discharged downward. become.
In the present embodiment, the resin W is heated and melted in the extruder 11 at a temperature of 260 ° C., for example, and the melting temperature is preferably set in a range of 240 to 280 ° C.

  The first plate belt 20 is a belt-like belt having a loop shape, and a belt surface 20a which is one surface of the belt-like shape has a fine uneven shape 101 formed on one surface of the optical sheet 100. A mold shape 21 having an inverse shape is formed.

  The first plate belt 20 is supported by a total of three guide rolls 23 (23a, 23b, 23c) arranged on the inner side of the loop shape with the belt surface 20a facing the outer side of the loop shape. .

  Each of these guide rolls 23 has a cylindrical shape, and a belt back surface 20b (back surface of the belt surface 20a) of the first plate belt 20 is wound around the outer peripheral surface of the guide roll 23 and can be driven around central axes parallel to each other. ing.

Of these three guide rolls 23, the first guide roll 23 a is disposed on one side in the horizontal direction on the lower side of the die 12 (left side in FIG. 1). The first guide roll 23 a is disposed at a position close to the die 12.
Further, the second guide roll 23b is disposed at a position spaced apart from the first guide roll 23a by a predetermined distance on the other side in the horizontal direction (the right side in FIG. 2) opposite to the one side in the horizontal direction. ing.
Further, the third guide roll 23c is disposed on one side in the horizontal direction at the same horizontal height as the second guide roll 23b. The third guide roll 23c is disposed on the lower side and the other side in the horizontal direction when viewed from the first guide roll 23a.

  When the first plate belt 20 is wound around the first to third guide rolls 23 having the above-described arrangement relationship, the first guide roll 23a and the second guide roll 23b have a first gap between them. An inclined section in which a part of the plate belt 20 is arranged to be inclined is formed. In the present embodiment, the inclined section has a downward slope with an inclination angle of 45 ° or less with respect to the horizontal plane. Note that the inclined section may have an upward gradient with an inclination angle of 45 ° or less with respect to the horizontal plane.

  Further, when the first to third guide rolls 23 are driven to rotate clockwise in the drawing, the first plate belt 20 is driven along the rotational drive of the guide rolls 23. Thereby, in the said inclination area, the 1st plate belt 20 moves so that it may progress toward the downward direction from the upper direction of inclination.

  The die 12 is located immediately above the upper end of the inclined section of the first plate belt 20. Therefore, the sheet-shaped resin W is continuously discharged from the die 12 onto the belt surface 20a of the first plate belt 20 traveling in the inclined section, and the resin W is placed on the belt surface 20a in the first state. The first plate belt 20 is transferred along with the movement.

The mold shape 21 of the first plate belt 20 has, for example, a mold uneven shape in which a ten-point average roughness Rz is set in a range of 50 μm to 200 μm and an arithmetic average roughness Ra is set in a range of 3.0 μm to 1000 μm. It is preferable.
Further, the mold shape 21 may be an inverse shape of the prism shape, the prism apex angle of the inverse shape being set in the range of 40 to 70 °, and the prism interval being in the range of 20 to 200 μm.

Furthermore, the mold shape 21 may have a reverse shape of any one of a cylindrical lens array shape, a prism lens array shape, and a microlens array shape extending in the depth direction of the drawing, or a lens array formed by combining these shapes. The shape may be reversed.
Furthermore, in addition to the reverse shape of the lens array shape, columnar shapes such as polygonal cones, cones, polygonal truncated cones, circular truncated cones, polygonal columns, and cylinders that are substantially the same or asymmetrical, or rectangular parallelepipeds, spheres, hemispheres, ellipsoids However, at least one kind may be formed in the reverse shape of the concave-convex shape that is formed by being arranged regularly or irregularly in stripes or dots.

  As a method of creating the mold shape 21 on the first plate belt 20, it may be molded using UV or radiation curable resin on a translucent substrate, or may be pretreated by corona treatment or easy adhesion treatment. You may shape | mold by apply | coating UV resin to a process surface, and pressing the metal mold | die of a desired lens shape to UV resin after that, and irradiating and hardening | curing UV.

As a material of the first plate belt 20 in the present embodiment, a transparent base material well known in the art such as PET (polyethylene terephthalate), PC (polycarbonate), PS (polystyrene), or the like can be used.
Moreover, as UV resin which shape | molds a mold shape, UV curable resin well known in the said fields, such as an acryl type and an epoxy type, can be used.
Thermoplastic resins include PC (polycarbonate), PS (polystyrene), PMMA (polymethyl methacrylate (polymethyl methacrylate, acrylic resin)), MS (styrene methacrylate copolymer), AS (acrylonitrile styrene copolymer). A thermoplastic resin well known in the art can be used.
As the thermosetting resin, a thermosetting resin well known in the art such as a phenol resin or a melamine resin can be used.

  Or, besides general-purpose plastics such as PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, PBT (polybutylene terephthalate), POM (poly Oxymethyl), PA (polyamide), PPS (polyphenylsulfide) and other well-known engineering plastics and super engineering plastics are used to make known extrusion molding, injection molding, or hot pressing. The first plate belt 20 may be integrally formed by a molding method.

  The concavo-convex forming portion 30 is disposed in the inclined section formed by the first plate belt 20, that is, between the first guide roll 23a and the second guide roll 23b, and more specifically in the inclined section. It is disposed at a position below the center, that is, a position closer to the second guide roll.

  The second plate roll 31 disposed in the concave-convex forming portion 30 is a member that is formed in a cylindrical shape and can be rotationally driven around a central axis parallel to the guide roll 23. On the roll surface 31a, which is the outer peripheral surface, a mold shape 32 is formed that is opposite to the fine uneven shape 102 formed on the other surface of the optical sheet 100.

  Such a second plate roll 31 has the roll surface 31a and the belt surface 20a spaced apart from each other so that the roll surface 31a faces the belt surface 20a of the first plate belt 20 in the concavo-convex molded portion 30. It is installed in a state.

The mold shape 32 of the second plate roll 31 has, for example, a mold uneven shape in which the ten-point average roughness Rz is set in a range of 50 μm to 200 μm and the arithmetic average roughness Ra is set in a range of 3.0 μm to 1000 μm. It is preferable.
Further, the mold shape 32 may be an inverse shape of the prism shape, the prism apex angle of the inverse shape being set in the range of 40 to 70 °, and the prism interval being in the range of 20 to 200 μm.

Further, the mold shape 32 may be a reverse shape of any one of a cylindrical lens array shape, a prism lens array shape, and a microlens array shape extending in the depth direction of the drawing, or a lens array formed by combining these shapes. The shape may be reversed.
Furthermore, in addition to the reverse shape of the lens array shape, columnar shapes such as polygonal cones, cones, polygonal truncated cones, circular truncated cones, polygonal columns, and cylinders that are substantially the same or asymmetrical, or rectangular parallelepipeds, spheres, hemispheres, ellipsoids However, at least one kind may be formed in a reverse shape of the uneven shape formed by being arranged regularly or irregularly in stripes or dots.

  As a method of creating the mold shape 32 on the second plate roll 31, it may be molded using UV or radiation curable resin on a translucent substrate, or may be pretreated by corona treatment or easy adhesion treatment. You may shape | mold by apply | coating UV resin to a process surface, and pressing the metal mold | die of a desired lens shape to UV resin after that, and irradiating and hardening | curing UV.

As a material of the second plate roll 31 in the present embodiment, a transparent base material well known in the art such as PET (polyethylene terephthalate), PC (polycarbonate), PS (polystyrene) can be used.
Moreover, as UV resin which shape | molds a mold shape, UV curable resin well known in the said fields, such as an acryl type and an epoxy type, can be used.
Thermoplastic resins include PC (polycarbonate), PS (polystyrene), PMMA (polymethyl methacrylate (polymethyl methacrylate, acrylic resin)), MS (styrene methacrylate copolymer), AS (acrylonitrile styrene copolymer). A thermoplastic resin well known in the art can be used.
As the thermosetting resin, a thermosetting resin well known in the art such as a phenol resin or a melamine resin can be used.

  Or, besides general-purpose plastics such as PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, PBT (polybutylene terephthalate), POM (poly Oxymethyl), PA (polyamide), PPS (polyphenylsulfide) and other well-known engineering plastics and super engineering plastics are used to make known extrusion molding, injection molding, or hot pressing. The second plate roll 31 may be integrally formed by a molding method.

  The pressing roll 33 is a member that is cylindrical and is rotatable around a central axis parallel to the central axis of the second plate roll 31, and is opposed to the second plate roll 31 and the first plate belt 20. It is installed on the belt back surface 20b side of the first plate belt 20 at the location. The pressing roll 33 is configured to be able to press the belt back surface 20b of the first plate belt 20, and thereby, the interval between the first plate belt 20 and the second plate roll 31 can be appropriately changed. .

  With such a configuration, the sheet-like resin W placed on the belt surface 20 a of the first plate belt 20 is sandwiched between the first plate belt 20 and the second plate roll 31 in the concave-convex forming portion 30. Pressed. As a result, the fine uneven shapes 101 and 102 formed by the mold shape 21 of the first plate belt 20 and the mold shape 32 of the second plate roll 31 are transferred to both surfaces of the sheet-like resin W.

  The transport roll 40 is a member that is cylindrical and rotatable about a central axis parallel to the guide roll 23, and is disposed on the other horizontal side of the second guide roll 23 b. The transport roll 40 has a role of transporting the sheet-like resin W in which the fine concavo-convex shapes 101 and 102 are formed in the concavo-convex forming portion 30 by being moved in the inclined section by the movement of the first plate belt 20 to the next process. Have.

An internal stress relaxation section 50 is disposed between the extrusion die 10 and the concave / convex forming portion 30, that is, between the vicinity of the upper end of the inclined section in the inclined section and the concave / convex forming portion 30.
The internal stress relaxation section 50 is linear along the inclined section. Therefore, the internal stress relaxation section 50 is in a state where the internal stress relaxation section 50 has a downward slope with an inclination angle of 45 ° or less with respect to the horizontal plane, like the inclined section. Has been placed.

  Further, in the present embodiment, the front end (end on the first guide roll 23a side into which the sheet-like resin W enters) and the rear end (concave-projection into which the sheet-like resin W advances) of the internal stress relaxation section 50. It is preferable that the length between the portion 30 and the end portion on the part 30 side is set in a range of 3 cm or more and 254 cm or less. From the viewpoint of stress relaxation, it is preferable that the stress relaxation section is long. However, when the stress relaxation section exceeds 254 cm, no further internal stress relaxation effect can be expected, resulting in wasted power consumption.

  Furthermore, the arrangement interval between the rear end of the internal stress relaxation section 50 and the concave-convex forming portion 30 (a portion where the sheet-shaped resin W is pinched by the first plate belt 20 and the second plate roll) is set within 10 cm. It is preferable.

  By providing such an internal stress relaxation section 50, the sheet-like resin W discharged from the extrusion die 10 passes through the internal stress relaxation section 50 over a predetermined time according to the moving speed of the first plate belt 20. After passing, it is introduced into the concavo-convex molded part 30.

  Furthermore, in this embodiment, the external heating equipment 51 which heats the said internal stress relaxation area 50 is provided. The external heating equipment 51 includes a cylindrical casing 51a surrounding the entire internal stress relaxation section 50 from the periphery. As shown in FIG. 2, a coiled heating wire 51b is provided inside the casing 51a. It is arranged. By energizing this heating wire, the internal stress relaxation section 50 located inside the external heating equipment 51 can be heated from its surroundings.

Further, the external heating equipment 51 heats the internal stress relaxation section 50 with an output such that the temperature difference of the sheet-like resin W at the front end and the rear end of the internal stress relaxation section 50 is within 5 ° C. It is preferable that it is comprised.
The external heating equipment 51 may be configured to heat the first plate belt 20 in the internal stress relaxation section 50 at a temperature substantially equal to that at the time when the resin W is heated and melted, that is, about 260 ° C. in the present embodiment.

  In addition to the heating method described above, various methods such as a method of circulating heated oil and a heating method of generating a magnetic field by applying a current can be used as the external heating equipment 51.

The optical sheet manufacturing method by the optical sheet manufacturing apparatus 1 having the above configuration will be described with reference to FIG.
First, as step S <b> 1, the resin W that is the material of the optical sheet 100 is heated and melted in the extruder 11 in the extrusion die 10.
Next, as step S <b> 2, the resin W heated and melted is extruded from the extrusion die 10 and is passed through the die 12 to form the resin W into a sheet shape.

The resin W thus formed into a sheet shape is discharged onto the belt surface 20 a in the inclined section of the first plate belt 20 located below the die 12.
Then, the sheet-like resin W is moved downward along the inclined section along with the movement of the first plate belt 20, and is passed through the internal stress relaxation section 50 as step S3. Since the internal stress relaxation section 50 is heated by the external heating equipment 51, the sheet-like resin W passes through the internal stress relaxation section 50 while being heated at a temperature substantially equal to that at the time of heating and melting.

As described above, the sheet-like resin W that has passed through the internal stress relaxation section 50 is transferred with the fine concavo-convex shapes 101 and 102 on both surfaces thereof in the concavo-convex forming portion 30 as step S4.
That is, both sides of the sheet-like resin W are sandwiched between the first plate belt 20 and the second plate roll 31 in the concave-convex forming portion 30, so that the first plate belt is placed on one surface of the sheet-like resin W. The fine uneven shape 101 is formed by the 20 mold shapes 21, and the fine uneven shape 102 is formed by the mold shape 32 of the second plate roll 31 on the other surface of the sheet-like resin W.

  The pressure when the sheet-like resin W is sandwiched between the first plate belt 20 and the second plate roll 31 is preferably set to a linear pressure of 0.1 to 30 kgf / cm. When deviating, desired fine uneven | corrugated shape 101,102 cannot be obtained.

  And the sheet-like resin W in which the fine uneven | corrugated shape 101,102 was formed in this way is conveyed by the conveyance roll 40 to the next process as step S5.

  Next, the effects of the optical sheet manufacturing apparatus 1 and the optical sheet manufacturing method of the present embodiment described above will be described in comparison with comparative examples described below.

FIG. 4 shows a schematic configuration of the optical sheet manufacturing apparatus 60 of the comparative example.
The optical sheet manufacturing apparatus 60 includes an extruder 61 that melts and extrudes the resin W, extrudes the resin W extruded from the extruder 61 into a sheet shape, and discharges the resin W downward. , The first roll 63 and the second roll 64 that are disposed opposite to each other in the horizontal direction through the air gap, the third roll 65 and the fourth roll 66 that are disposed on the side of the second roll 64, and the fourth Four transport rolls 67 and a pair of upper and lower transport rolls 68 arranged in the horizontal direction on the side of the roll 66 are provided.

  In such an optical sheet manufacturing apparatus 60, the following extrusion process is performed. That is, the resin W melted by the extruder 11 by the die 62 is discharged downward in a sheet shape and sent to the air gap between the first roll 63 and the second roll 64. At this time, the sheet-shaped resin W Is pressed against the second roll 64 by the first roll 63.

As a result, the sheet-like resin W is held in close contact with the second roll 64 and bent into a curved shape along the outer peripheral surface of the second roll 64.
The resin that has passed through the second roll 64 is sent to the third roll 65 and the fourth roll 66 for the purpose of air cooling and annealing. Again, the sheet-like resin W is bent into a curved shape along the third roll 65 and the fourth roll 66. And the sheet-like resin W which passed through the 4th roll 66 is conveyed by the conveyance rolls 67 and 68, and an extrusion molding process is complete | finished.

  When an optical sheet is manufactured by the optical sheet manufacturing apparatus 60 of such a comparative example, since the annealing effect of the sheet-like resin W discharged from the die 62 becomes insufficient, the internal stress cannot be removed, and the molded sheet There is a drawback that the product is warped or bent. That is, since the resin W is cooled before the internal stress of the discharged sheet-like resin W is relaxed, the internal stress remains in the molded product.

On the other hand, according to the optical sheet manufacturing apparatus 1 of the present embodiment, it is possible to prevent the sheet-like resin W discharged from the extrusion die 10 from solidifying in a state having an internal stress.
That is, the sheet-like resin W discharged from the extrusion die 10 moves in the internal stress relaxation section 50 heated by the external heating equipment 51 over a predetermined time. As a result, the sheet-like resin W is allowed to stand for a predetermined time in a melted state without being solidified to obtain an annealing effect, so that the stress remaining inside can be relieved. Therefore, it is possible to avoid the occurrence of residual stress in the manufactured optical sheet 100. Thereby, it becomes possible to avoid that the optical sheet 100 which is a molded product is deformed or damaged due to warping or bending.

  By providing the internal stress relaxation section 50, there is an advantage that static electricity and air inside the resin W can be easily removed, and dimples due to static electricity and air hardly occur inside the product.

  Further, in the optical sheet manufacturing apparatus 1 of the present embodiment, the sheet-like resin W discharged from the extrusion die 10 passes through the linear internal stress relaxation section 50, so that the sheet-like resin W is bent. The internal stress is not newly generated in the resin W.

  Further, since the internal stress relaxation section 50 is arranged to be inclined, the sheet-like resin W passing through the internal stress relaxation section 50 has a resin toward the lower side in the tilt direction of the internal stress relaxation section 50. The pressure due to the weight of W acts. That is, since uniform pressure can be applied along the extending direction of the sheet-like resin W, it is possible to remove internal stress in the sheet-like resin W.

Here, when the inclination angle of the internal stress relaxation section 50 exceeds 45 °, excessive pressure is applied to the sheet-like resin W along the extending direction of the sheet-like, and new internal stress is generated. End up. Moreover, there exists a possibility that the sheet-like resin W may slide down and be folded over.
In this regard, in the present embodiment, since the inclination of the internal stress relaxation section 50 is set to an inclination angle of 45 ° or less, the above inconvenience can be corrected.

Further, since the external heating equipment 51 heats the internal stress relaxation section 50 so that the temperature difference of the sheet-like resin W between the front end and the rear end of the internal stress relaxation section 50 is within 5 ° C., the internal stress relaxation section concerned In the section 50, the internal stress can be reliably relaxed without solidifying the sheet-like resin W.
In addition, when the temperature difference before and after the internal stress relaxation section 50 exceeds 5 ° C., the melt viscosity of the resin W changes greatly, the viscosity decreases due to the high temperature, and leaks from the first plate belt 20, If the temperature is low, there is a problem that the viscosity is lowered and the resin is solidified at a low temperature while keeping the internal stress, but the problem can be avoided.

  Furthermore, since the arrangement | positioning space | interval of the rear end of the internal stress relaxation area 50 and the uneven | corrugated shaping | molding part 30 is set within 10 cm, uneven | corrugated shaping | molding is carried out, without solidifying the sheet-like resin W which passed the internal stress relaxation area 50. Part 30 can be reached. This makes it possible to reliably mold the fine uneven shapes 101 and 102 on both surfaces of the sheet-like resin W.

  Further, in the present embodiment, the sheet-like resin W extruded from the extrusion die 10 is discharged onto the belt surface 20a of the first plate belt 20, and the first plate belt 20 moves through the internal stress relaxation section 50. Thereby, the internal stress of the sheet-like resin W is relieved. Then, after passing through the internal stress relaxation section 50, the first plate belt 20 reaches the concave-convex molded portion 30, and at this time, in the concave-convex molded portion 30, the sheet-like resin W on the belt surface 20a of the first plate belt 20 is obtained. Comes into contact with the roll surface 31 a of the second plate roll 31, so that the sheet-like resin W is sandwiched between the first plate belt 20 and the second plate roll 31. Accordingly, the fine uneven shapes 101 and 102 can be reliably transferred onto both surfaces of the sheet-like resin W.

  In addition, when the time difference arises in the contact with the discharged resin W, the 1st plate belt 20, and the 2nd plate roll 31, it becomes possible to match the shaping of a product front and back.

Further, since the first plate belt 20 has a loop shape, the first plate belt 20 heated through the internal stress relaxation section 50 moves in a high temperature state. That is, since the first plate belt 20 is heated before the sheet-shaped resin W is discharged, when the sheet-shaped resin W is discharged onto the belt surface 20a of the first plate belt 20, the first plate belt 20 is heated. It is possible to prevent the heat of the sheet-like resin W from being taken by the belt surface 20a and the resin W to be solidified.
Further, the same effect can be obtained by applying a hot air such as a blower or a heater before the resin W is discharged onto the first plate belt 20 or by bringing it into contact with a heat medium. Further, a similar effect can be obtained by a method in which a heated guide roll that follows the first plate belt 20 is installed and conveyed with the first plate belt 20.

  The time for the sheet-like resin W to pass through the internal stress relaxation section is preferably set in the range of 30 seconds to 3 minutes. This time can be easily adjusted by changing the feed speed of the guide roll 23. By setting the passage time within the above range, productivity can be ensured while the internal stress of the sheet-like resin W is reliably relaxed.

(Optical sheet)
Next, the optical sheet 100 of this embodiment will be described. The optical sheet 100 is formed by the optical sheet manufacturing apparatus 1 and the optical sheet manufacturing method described above.
As shown in FIG. 5, the optical sheet 100 controls the optical path of light incident from one side of the light source and emits it from the other side. The optical sheet 100 has both sides of one side and the other side. Are provided with fine irregularities 101 and 102. The optical sheet 100 may be a single layer or a laminated structure in which a plurality of layers are laminated.

  By providing the fine concavo-convex shapes 101 and 102 on both surfaces of the optical sheet 100, light can be scattered on the surface, so that effects such as improvement in luminance and reduction in lamp image can be obtained. In addition, since the voids can be obtained by the fine concavo-convex shapes 101 and 102 when brought into contact with other members, for example, it is possible to prevent optical influences such as Newton rings due to the close contact between the optical sheet 100 and the diffusion sheet. It becomes.

The fine irregularities 101 and 102 on at least one of the one surface and the other surface of the optical sheet 100 have a ten-point average roughness Rz of 50 μm to 200 μm and an arithmetic average roughness Ra of 3.0 μm to 1000 μm. It is preferable that it is set to.
Further, even if the fine uneven shapes 101 and 102 have a reverse prism shape, the prism apex angle of the reverse shape is set in the range of 40 to 70 °, and the prism interval is set in the range of 20 to 200 μm. Good.
Furthermore, the fine uneven shapes 101 and 102 are any one of a polygonal pyramid shape, a conical shape, a polygonal frustum shape, a truncated cone shape, a polygonal columnar shape, a cylindrical shape, a rectangular parallelepiped shape, a hemispherical shape, an ellipsoidal shape, and a cylindrical shape. Or a shape that is an inverse combination of these shapes may be used.
Moreover, these fine uneven | corrugated shape 101,102 may be arranged regularly, and may be arranged unevenly.
In any case, the fine uneven shapes 101 and 102 depend on the mold shapes 21 and 32 of the first plate belt 20 and the second plate roll 31 of the optical sheet manufacturing apparatus 1 that manufactures the optical sheet 100.

  The resin W used in the optical sheet 100 may be a transparent resin, a colored resin, or an opaque resin. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, an epoxy acrylate resin, In addition to general-purpose plastics such as thermoplastic resins such as polystyrene resins, acrylonitrile styrene resins, cycloolefin polymers, methyl styrene resins, fluorene resins, PET (polyethylene terephthalate), polypropylene, phenol resins, melamine resins, and thermosetting resins, Engineer plastics such as PBT (polybutylene terephthalate), POM (polyoxymethyl), PA (polyamide), PPS (polyphenyl sulfide), and other well-known engineering plastics and Super Engineer Plus A click can be used.

As the light scattering particle 103 dispersed and mixed in such a resin, a spherical or irregular shaped particle is used.
The value of the difference in refractive index between the light scattering particles 103 and the resin W is set to 0.02 or more. Within this range, light diffusibility can be obtained, and viewing angle distribution can be adjusted appropriately.

Furthermore, the average particle diameter of the light scattering particles 103 is set in the range of 0.5 to 12 μm. When the average particle diameter of the light scattering particles 103 is less than 0.5 μm or more than 12 μm, the light diffusibility is not sufficient and the viewing angle distribution cannot be adjusted, which is not preferable. In this regard, if the average particle diameter of the light scattering particles 103 is in the range of 0.5 to 12 μm, sufficient light scattering properties can be obtained.
The average particle diameter of the light scattering particles 103 is more preferably 2 to 6 μm or less.

  The optical sheet 100 has very high light transmittance while maintaining a certain degree of light diffusivity when the mixing amount of light scattering particles in each resin W is in the range of 0.1 to 30% by weight. Thus, the light can be propagated without loss due to the fine uneven shapes 101 and 102 on the front and back sides. Therefore, it is possible to obtain the effect of improving the front luminance while reducing the lamp image by making the light uniform with very high light diffusivity while maintaining a certain degree of light transmittance.

  As the material of the light scattering particles 103, particles made of inorganic fine particles or organic fine particles are used. Examples of this include acrylic particles, styrene particles, styrene acrylic particles and crosslinked products thereof, melamine-formalin condensate particles, polyurethane particles, polyester particles, silicone particles, fluorine particles, copolymers thereof, Clay compound particles such as smectite, kaolinite, talc, inorganic oxide particles such as silica, titanium oxide, alumina, silica alumina, zirconia, zinc oxide, barium oxide, strontium oxide, calcium carbonate, barium carbonate, magnesium carbonate, barium chloride , Barium sulfate, barium nitrate, barium hydroxide, aluminum hydroxide, strontium carbonate, strontium chloride, strontium sulfate, strontium nitrate, strontium hydroxide, inorganic particles such as glass particles, zinc sulfide metal particles, aluminum Mention may be made of metal particles such as Umm and silver. One kind of these high refractive index transparent particles and metal particles may be used, or a plurality of kinds may be used in combination.

  In addition, when creating a fine cavity containing air instead of the light scattering particle 103, it may be created by foaming a foaming agent contained in a main material in advance.

  The functions required of the integrated optical sheet 100 include a function of diffusing light from a light source and a function of adjusting the diffused light to a desired light distribution. These functions may be imparted to different layers, or may be imparted to a plurality of members in an overlapping manner. Furthermore, the integrated optical sheet 100 is also required to have rigidity that does not generate wrinkles in a self-supporting state. This rigidity may be imparted to a specific layer or may be imparted to each layer when the integrated optical sheet 100 is composed of a plurality of layers. Even if the rigidity of each layer is insufficient, the integrated optical sheet 100 may have rigidity.

  The optical sheet 100 may have a sheet shape, a plate shape, or a plate shape, and the total thickness is desirably 200 μm or more and 3000 μm or less. When the total thickness is 200 μm or less, there is a problem that bending and wrinkling occur because of thinness and lack of stiffness. On the other hand, when the total thickness is 3000 μm or more, the amount of light from the light source that passes through the optical sheet 100 is reduced, and thus there is a problem that the practicality is poor.

The optical sheet 100 as described above is preferably used for a backlight using only the optical sheet 100. Note that. If desired optical performance and appearance cannot be obtained, a diffusion sheet may be used in combination. That is, the optical sheet 100 may be used alone, or may be used in combination with at least one or more of a diffusion plate, a condensing film, a diffusion film, and the like.
Further, when the light source is not linear, a hole may be made in at least a part of the optical sheet 100 so as not to cover the light from the light source.

In addition, the optical sheet 100 may be an at least one layer disposed on the light source side or a surface irregularity shape to which an ultraviolet absorber is added. Thereby, deterioration of the optical sheet 100 itself due to ultraviolet rays irradiated from the light source can be suppressed, and the life can be extended. Furthermore, it is possible to suppress deterioration due to ultraviolet rays, such as a lens sheet, a diffusion film, and a condensing sheet that are disposed to face the light emission surface of the optical sheet 100.
Examples of the ultraviolet absorber include benzotriazole compounds such as 2- (2′-Hydrogen-5′-methylphenyl) benzotriazole, benzophenone compounds such as 2-hydroxy-4-methoxybenzophenone, 4- Salicylic acid ester compounds such as t-butylphenyl salicylate, oxalic acid anilide compounds such as 2-ethoxy-2′-ethyl oxalic acid bisanilide, ethyl-2-cyano-3,3-diphenyl acrylate, etc. A cyanoacrylate or the like can be used.

  In addition, it is also possible to acquire the diffusion effect by the said space | gap by forming a space | gap (air layer) between the fine uneven | corrugated shape 101,102 of the front and back, and a diffusion sheet as mentioned above.

(Backlight unit, display device)
Next, the backlight unit and display device of this embodiment will be described.
As shown in FIG. 6, the display device 110 according to the embodiment is a liquid crystal display device configured by overlapping an image display element 112 on the light emission side of a backlight unit 111 that emits light upward. In addition, an image is displayed by emitting display light whose display is controlled by an image signal from the image display element 112 toward the viewer.

  The image display element 112 is preferably an element that displays an image by transmitting / blocking light in pixel units. An image with high image quality can be displayed as long as the image is displayed by transmitting / blocking light in pixel units.

  As the image display element 112, a liquid crystal display element is used in the present embodiment. A liquid crystal display element is a typical element that transmits / shields light in pixel units and displays an image, and can improve image quality and reduce manufacturing cost compared to other display elements. Can do.

  The liquid crystal panel as the image display element 112 includes, for example, a back surface side of a liquid crystal cell (display element or panel) that controls a light transmission state according to an image signal for each of a plurality of pixel regions formed in a rectangular lattice shape. A polarizing plate for controlling the polarization direction of light is laminated on the viewer side. The liquid crystal cell includes a pair of glass substrates and a liquid crystal layer sandwiched between them.

  The image display element 112 is a so-called transmissive display panel in the present embodiment, but may be a transflective display panel. Alternatively, instead of the image display element 112 as a liquid crystal panel including a liquid crystal cell, another display panel such as a display panel that displays a still image with a light-transmitting coloring pattern may be used.

The backlight unit 111 is a light emitting device having a light emitting surface having substantially the same area as the display screen of the image display element 112, and the optical sheet 100, the lens sheet 114, and the diffusion are disposed on the light emission direction side of the light source unit 113. A sheet 115, a condensing sheet 116 such as BEF, and a diffusion sheet 117 are stacked in this order.
Instead of the diffusion sheet 117, a polarization separation sheet may be adopted.

The light source unit 113 employs a direct type that is configured by surrounding a lamp house 113b on the back side and the side surface on which a plurality of light sources 113a are arranged.
As the light source 113a, in addition to a cold cathode fluorescent lamp, an LED, an EL, a semiconductor laser, or the like that has recently been attracting attention as a light source for display can be used.

  When an LED is used as the light source 113a, an array of red, green, and blue LEDs is used, and light from the array of red, green, and blue LEDs is mixed and emitted uniformly as white light using a light guide plate or the like. Alternatively, it is possible to use an optical control element having a diffusing function that can mix light from an array of red, green, and blue LEDs and emit uniformly as white light.

  It is preferable that the distance between the optical sheet 100 laminated on the front side of the light source unit 113 and the light source 113a is set to 20 mm or less. The distance between the optical sheet 100 and the image display element 112 is preferably set to 40 mm or less. When the distance is longer than this, the backlight unit 111 becomes thick, and it becomes impossible to create a thin display device 110.

  Note that the backlight unit 111 is becoming thinner and thinner, and accordingly, the distance between the light source 113a and the optical sheet 100 is shortened. However, if the optical sheet 100 of the above embodiment is used, a direct type or Even in the side-edge type backlight unit, there is no influence of visibility such as a dark spot between the light sources 113a, and the backlight unit can be used sufficiently.

  Furthermore, the size of the optical sheet 100 is also increasing along with the increase in the size of the display device 110. However, since the optical sheet 100 of the above embodiment is an integrated type, it is thin and strong, Since the display quality is excellent, it can be sufficiently used for such a large display device 110.

Next, operations of the backlight unit 111 and the display device 110 having the above-described configuration will be described.
The light emitted from the light source 113a directly enters the optical sheet 100 or enters the optical sheet 100 through reflection at the lamp house 113b. Then, the light incident on the optical sheet 100 is refracted by the fine concavo-convex shape 101 on one surface (incident surface) of the optical sheet 100 and has a spread angle in an appropriate angle range while being repeatedly scattered inside the optical sheet 100. The light is propagated as diffused light and is refracted and emitted by the fine uneven shape 102 on the other surface (exit surface) of the optical sheet 100.

  The light passing through the optical sheet 100 in this manner passes through the lens sheet 114, the diffusion sheet 115, the condensing sheet 116 such as BEF, and the diffusion sheet 117, and finally passes through the image display element 112, thereby displaying an image. As viewed by an observer.

In this way, the effect of the diffusion and refraction causes an optical path difference in the propagating light, so that the light can reach a position separated from immediately above the light source 113a. That is, it is possible to reduce the lamp image by widening the bright place.
In addition, since a high diffusion function can be obtained only by the optical sheet 100 as described above, a sufficient effect can be obtained even if it is not necessary to separately provide a diffusion film or the like. Therefore, it is possible to reduce the number of parts and reduce the manufacturing cost.

  Furthermore, since the optical sheet 100 includes the fine uneven shapes 101 and 102 having a light collecting function in the front direction (observer side), the light collecting function by the fine uneven shapes 101 and 102 can be obtained. Therefore, it is possible to obtain a very high front luminance while reducing the lamp image.

  Note that the optical sheet 100 may have a single-layer structure or a multilayer structure, and any of the fine uneven shapes 101 and 102 may be disposed on the light source unit 113 side.

  A light diffusion film may be disposed on the front side of the optical sheet 100. Thereby, in addition to the effect | action of the optical sheet 100, since the condensing function by a light-diffusion film can be obtained, it becomes possible to obtain high front luminance, reducing a lamp image.

  Furthermore, since the optical sheet 100 can maintain high strength even when the optical sheet 100 is formed thin, and the image display quality of the display device 110 can be excellent, a large display It is suitable to use for.

The optical sheet 100 can be used for controlling the viewing angle of the display device 110 and for improving the contrast, in addition to the application used for improving the luminance of light from the light source unit 113. .
Furthermore, for example, it is also possible to improve the brightness of the light projected on the projection screen or to use for controlling the light for solar cells. Moreover, since the optical sheet 100 can uniformly diffuse and collect light from the illumination light source, it can also be used for illumination covers, signboards, building materials, and the like.

According to the backlight unit 111 of the present embodiment using such an optical sheet 100, the optical characteristics relating to light diffusibility and light transmission are optimized, and light with improved brightness in the front direction is supplied to the liquid crystal panel. It becomes possible to make it enter.
Therefore, the display device 110 can display an image with high brightness and reduced lamp image.
In addition, since the lamp image reduction effect and the luminance are high, the number of light sources 113a of the light source unit 113 can be reduced, so that energy saving of the backlight unit 111 and the display device 110 can be achieved.

  The optical sheet 100 according to the embodiment was produced and the physical properties thereof were evaluated. Hereinafter, a specific configuration, a test method, and a test result of the manufactured optical sheet 100 will be described.

(How to create the first version)
A UV curable resin is applied to a PET (polyethylene terephthalate) sheet as a base material, UV is irradiated while pressing a desired convex mold, and a first mold having a concave cylindrical shape with a pitch of 50 μm is formed. A plate belt 20 was produced.

(Installation of external heating equipment)
Cover the inside with a 3 mm thick stainless steel plate so that the first plate belt 20 and the resin W can pass inside the gap of 1200 mm in width, 30 mm in height, and 1200 mm in the flow direction. Equipment 51 was configured.

(How to create the second edition)
A second plate roll 31 was produced by cutting a concave mold shape with a pitch of 75 μm on the surface of the metal roll and subjecting the surface to a chrome plating treatment.

(Create a resin laminate)
A resin in which a polycarbonate resin (PC) and a polymethyl methacrylate resin filler were mixed at 0.5 wt%, 0 wt%, and 25 wt% was melted at 260 ° C. and discharged from the die 12 of the extrusion die 10 into a sheet by coextrusion. .
The internal stress relaxation zone where the discharged resin is received by the first plate belt 20 that has been heated to 260 ° C. in advance, and the internal stress relaxation zone 50 of 1200 mm heated to 260 ° C. is transferred at a speed of 2 m / min. After passing 50, the linear pressure is set to 0.95 kgf / cm, and the first plate belt 20 and the second plate roll 31 narrow the pressure so as to sandwich the resin W, and fine uneven shapes 101 and 102 are formed on both surfaces of the sheet-like resin W. Was shaped.

(Verification of deflection)
The prepared optical sheet 100 was cut into a 37-inch size, and then placed flat on a flat surface, and the amount of floating at the center of the square and the four sides was measured from the installation surface.

(Manufacturing method of backlight unit and liquid crystal display device)
The produced optical sheet 100 was cut into a 37-inch size, and the surface unevenness was opposed to the cold cathode tube, and in the case of a cylindrical lens array, it was arranged in the backlight unit 111 so as to be parallel to the light source.

(Evaluation of product deflection with or without stress relaxation zone)
Table 1 shows the result of comparison with an optical sheet molded without providing a stress relaxation section. In addition, as shown in FIG. 9, the amount of bending in Table 1 indicates the distance of the outer peripheral edge from the horizontal plane when the optical sheet is placed on the horizontal plane, and (1) to (8) are The measurement location is shown.
From this result, it has been found that the occurrence of bending of the product can be suppressed by providing the stress relaxation section.

(Diffusion evaluation of backlight unit and display device)
The diffusion performance was evaluated by comparison with a commercially available diffusion plate. The evaluation results are shown in Table 2.
In the optical sheet 100 according to the example, when the commercially available diffusion plate is 1, the integrated light quantity is 0.8, the diffusion effect is 3.0 on the front, and the diagonal is 3.5, which is sufficient as compared with the conventional diffusion plate. Diffusivity could be obtained. However, the total light transmittance was low, and the displayed image was extremely dark. On the other hand, the film pressure can be greatly reduced compared to commercially available products, luminance unevenness between the light sources is greatly reduced, and the occurrence of moire due to light interference is also suppressed.

DESCRIPTION OF SYMBOLS 1 Optical sheet manufacturing apparatus 10 Extrusion die 11 Extruder 12 Die 20 1st plate belt 20a Belt surface 20b Belt back surface 21 Mold shape 23 Guide roll 23a 1st guide roll 23b 2nd guide roll 23c 3rd guide roll 30 Unevenness Forming part 31 Second plate roll 31a Roll surface 32 Mold shape 33 Press roll 40 Transport roll 50 Internal stress relaxation section 51 External heating equipment (heating equipment)
60 Optical sheet manufacturing apparatus 61 Extruder 62 Die 63 1st roll 64 2nd roll 65 3rd roll 66 4th roll 67 Transport roll 68 Transport roll 100 Optical sheet 101 Fine uneven shape 102 Fine uneven shape 103 Light scattering particle 110 Display device 111 Backlight unit 112 Image display element 113 Light source unit 113a Light source 113b Lamp house 114 Lens sheet 115 Diffusion sheet 116 Condensing sheet 117 Diffusion sheet

Claims (16)

An optical sheet manufacturing apparatus for continuously manufacturing an optical sheet having fine uneven shapes on both sides and used for illumination optical path control by extrusion molding,
An extrusion die for extruding and discharging the heat-melted resin into a sheet,
An uneven forming part for forming the fine uneven shape on both sides by sandwiching the sheet-like resin,
An internal stress relaxation section through which the sheet-like resin extruded from the extrusion die passes for a predetermined time is provided between the extrusion die and the concavo-convex molded portion, and heating for heating the internal stress relaxation section An optical sheet manufacturing apparatus provided with equipment.   The optical sheet manufacturing apparatus according to claim 1, wherein the internal stress relaxation section is linear.   The optical sheet manufacturing apparatus according to claim 1 or 2, wherein a length between a front end and a rear end of the internal stress relaxation section is set in a range of 3 cm or more and 254 cm or less.   The optical sheet manufacturing apparatus according to any one of claims 1 to 3, wherein the internal stress relaxation section is inclined.   The optical sheet manufacturing apparatus according to claim 4, wherein an inclination of the internal stress relaxation section is an ascending slope or a descending slope having an inclination angle of 45 ° or less with respect to a horizontal plane.   The heating equipment heats the internal stress relaxation section so that the temperature difference of the sheet-like resin between the front end and the rear end of the internal stress relaxation section is within 5 ° C. The optical sheet manufacturing apparatus according to claim 5.   The optical sheet manufacturing apparatus according to any one of claims 1 to 6, wherein an arrangement interval between the rear end of the internal stress relaxation section and the concave-convex molded portion is set within 10 cm. A first plate having a first mold shape that is opposite to the fine irregularities on one surface of the optical sheet;
A second plate having a second mold shape opposite to the fine irregularities on the other surface of the optical sheet;
2. The fine concavo-convex shape is transferred to both surfaces of the sheet-like resin by sandwiching the resin between the first plate and the second plate in the concavo-convex molded portion. The optical sheet manufacturing apparatus as described in any one of 7 to 7. The first plate forms a belt shape having the first mold shape on the belt surface, and the sheet-like resin is discharged onto the belt surface to move through the internal stress relaxation section and the concavo-convex molded portion,
The optical sheet manufacturing apparatus according to claim 8, wherein the second plate has a roll shape having the second mold shape on a roll surface, and is disposed in the concave-convex forming portion.   The optical sheet manufacturing apparatus according to claim 9, wherein the belt surface of the first plate is heated before the sheet-like resin is discharged. At least one of the first mold shape and the second mold shape is
11. The optical according to claim 8, wherein the ten-point average roughness Rz is set in a range of 50 μm to 200 μm, and the arithmetic average roughness Ra is set in a range of 3.0 μm to 1000 μm. Sheet manufacturing equipment. At least one of the first mold shape and the second mold shape is
The reverse of the prism shape,
The optical sheet manufacturing apparatus according to any one of claims 8 to 10, wherein the inverted prism apex angle is set in a range of 40 to 70 ° and a prism interval is set in a range of 20 to 200 µm. At least one of the first mold shape and the second mold shape is
Polygonal pyramid shape, conical shape, polygonal pyramid shape, circular truncated cone shape, polygonal columnar shape, cylindrical shape, rectangular parallelepiped shape, hemispherical shape, ellipsoidal shape, cylindrical shape, or any combination thereof The optical sheet manufacturing apparatus according to any one of claims 8 to 10, wherein the optical sheet manufacturing apparatus has an inverse shape.   The optical sheet manufacturing apparatus according to any one of claims 8 to 13, wherein at least one of the first mold shape and the second mold shape is regularly arranged.   The optical sheet manufacturing apparatus according to any one of claims 8 to 13, wherein at least one of the first mold shape and the second mold shape is non-uniformly arranged. An optical sheet manufacturing method for continuously manufacturing an optical sheet having fine uneven shapes on both sides and used for illumination optical path control by extrusion molding,
An extrusion process for extruding the heat-melted resin into a sheet,
An uneven forming step of forming the fine uneven shape on both sides by sandwiching the sheet-like resin,
Between the extruding step and the concavo-convex forming step, an internal stress relaxation step is provided for moving the sheet-like resin extruded by the extruding step linearly over a predetermined time,
An optical sheet manufacturing method comprising a heating step of heating the sheet-like resin to substantially the same temperature as that during the heating and melting simultaneously with the internal stress relaxation step.

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