JP2007156014A - Method for manufacturing optical sheet for display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a laminate of sheet-like bodies, which is used in a liquid crystal display element, with steps simpler than conventional ones at a low cost and with high quality. <P>SOLUTION: The method for manufacturing is provided with steps to: laminate two or more optical sheets 12, 14, 18 of which the plane sizes are equal to or larger than the size of the product; suck out air inside the laminate 30 of the optical sheets to a reduced pressure state; bond the laminate of the optical sheets on at least one or more places on the periphery thereof; and cut the periphery of the optical sheet laminate so as to align the size of the laminate with that of the product. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an optical sheet for display, and in particular, for producing a laminate of sheet-like materials used for liquid crystal display elements and the like at a low cost and with high quality by a simpler process than before. The present invention relates to a method for manufacturing a suitable optical sheet for display.

  In recent years, a film that diffuses light from a light source such as a light guide plate, a lens film that condenses light in the front direction, and the like are used for electronic displays such as liquid crystal display elements and organic EL.

  In this case, there are many examples in which various optical films (sheets) are laminated. For example, in Patent Document 1, a reflective polarizing film, a retardation film, and a semi-transmissive semi-reflective layer are laminated in an arbitrary order, and further, an absorptive polarizing film is laminated outside these three layers. A semi-reflective polarizing film is provided. And as many as five layers of films are interposed between the light source device and the liquid crystal cell. With this configuration, it is said that screen luminance is increased or power consumption is suppressed.

Patent Documents 2 to 4 disclose a film in which the functions of one light diffusion film and a lens film are integrated.
JP 2004-184575 A Japanese Patent Laid-Open No. 7-230001 Japanese Patent No. 3123006 JP-A-5-341132

  However, in the above-described conventional configuration, it is required to go through a number of processes in order to laminate a number of layers of film, which complicates the process and inevitably increases the cost.

  Furthermore, since the surface of a flat lens such as a lenticular lens or a prism sheet is easily damaged or dirty, a form in which a protective sheet is attached to the surface is generally delivered.

  However, such a protective sheet is only discarded after being peeled from the flat lens, and is not preferable because it is not only a waste of resources but also increases costs. Moreover, the operation | work which peels a protective sheet from a flat lens is required, and will also reduce productivity by that much. Further, when the protective sheet is peeled off from the flat lens, contamination such as dust is easily attached to the flat lens by peeling charging, and there are many problems in terms of quality.

  Also, when laminating multiple layers of films (sheets), the film tends to be damaged due to rubbing during lamination, rubbing due to thermal expansion / shrinkage, rubbing due to handling, and the like.

  Furthermore, in order to correct defects (distortion, curl, etc.) due to mismatching due to thermal expansion / contraction between multiple films, measures such as increasing the thickness of individual films (such as increasing rigidity) must also be required. There are many demerits such as design restrictions and cost increase.

  The present invention has been made in view of such circumstances, and manufactures a laminate of sheet-like materials used for display applications such as liquid crystal display elements at low cost and high quality by a simpler process than before. An object of the present invention is to provide a method for producing an optical sheet for a display suitable for the purpose.

  In order to achieve the above object, the present invention provides a laminating step for laminating two or more optical sheets having a planar size of the product equal to or larger than the product size, and a vacuum for sucking the inside of the laminate of the optical sheets into a decompressed state A display comprising: a step, a joining step of joining the optical sheet laminate at at least one location on the periphery, and a cutting step of cutting the periphery of the optical sheet laminate into a product size. A method for manufacturing an optical sheet for use is provided.

  According to the present invention, two or more optical sheets having a planar size equal to or larger than the product size are laminated, the inside of the laminated body is sucked into a reduced pressure state, and the laminated body is joined at at least one place on the periphery. Cut the periphery of the product into product sizes.

  Therefore, it is possible to omit the step of cutting a number of films (sheets) into product sizes, and it is possible to omit the step of laminating layers of films (sheets) while positioning them. Further, the above-described problem due to the protective sheet does not occur, and it is advantageous in terms of cost and quality. Furthermore, the above-mentioned problems when laminating several layers of films and the above-mentioned problems due to thermal expansion / contraction between a plurality of films do not occur.

  In particular, since the inside of the laminated body is sucked in a reduced pressure state, even if contamination such as dust adheres to the flat lens by peeling electrification when the protective sheet is peeled from the flat lens, various kinds of dust and the like are caused by this suction. Since contamination is discharged to the outside of the laminate, defects due to dust generation can be effectively suppressed.

  From the above points, according to the present invention, the optical sheet for display can be manufactured at a low cost and with high quality by a simpler process than before.

  The optical sheet (optical film) is a general term for various sheets having optical functions, and is a diffusion sheet, a polarizing plate (diffusion sheet film), various lens sheets (lenticular lenses, fly-eye lenses (amber eye lenses). ), Prism sheet, etc.) are representative, but include a protective sheet (protective film) that hardly performs an optical function.

  In addition, since “the planar size of the sheet is equal to or larger than the product size”, the planar size of the lens sheet or the optical sheet is the same as the product size as well as when the planar size of the lens sheet or the optical sheet is larger than the product size. Is also included. In such a case, in the cutting step, one or more sides of the lens sheet or the optical sheet may not be cut.

  Further, “joining at least one or more spots on the periphery” in the joining process means a peripheral part of the product size to be cut by the cutting process.

  In the present invention, in the decompression step, it is preferable to temporarily fix the optical sheets of the laminate by decompression suction. Thus, if the optical sheets can be temporarily fixed in the decompression step, the subsequent joining step becomes easy.

  In the present invention, the joining step can be performed after the decompression step, and the decompression step and the joining step can be performed simultaneously.

  Moreover, in this invention, it is preferable to attract | suck from the edge part of the said laminated body in the said pressure reduction process. Thus, if it attracts | sucks from the edge part of a laminated body, attracting | sucking is easy. In addition, when the optical sheet is a breathable material, suction from the surface can also be performed.

  Moreover, in this invention, it is preferable to join the said optical sheet in at least 1 side of a periphery in the said joining process. As described above, when bonding is performed on at least one side of the periphery of the stacked body, fixation of the stacked body becomes strong.

  Note that “at least one side of the peripheral edge” in the joining process means a peripheral edge of the product size to be cut by the cutting process.

  Moreover, in this invention, it is preferable to join the said optical sheet in 4 sides of a periphery in the said joining process. Thus, if bonding is performed on the four sides of the periphery of the laminate, the laminate is more firmly fixed, and contamination such as dust can be more effectively prevented.

  Note that “four sides of the periphery” in the joining step means four sides of the product size that are cut in the cutting step.

  In the present invention, the optical sheet preferably includes a diffusion sheet. In the present invention, it is preferable that the optical sheet includes a lens sheet in which convex lenses formed in a uniaxial direction are adjacently arranged on the entire surface. The “lens sheet in which convex lenses formed in one axis direction are adjacently arranged on substantially the entire surface” is typically a lenticular lens or a prism sheet, and also includes a diffraction grating and the like.

  In the present invention, it is preferable that the optical sheet includes two or more sheets having the same optical performance. In the case of including two or more sheets having the same optical performance, for example, two lens sheets in which convex lenses formed in one axial direction are adjacently arranged on substantially the entire surface are formed of convex lenses. An example in which the axes are laminated in a substantially perpendicular direction and an example in which a diffusion sheet is laminated on the front surface and the back surface of the laminated body of lens sheets are given. In addition, although “laminated in a direction in which the lens axis is substantially perpendicular” is described, the angle may be slightly adjusted to prevent moire fringes and the like.

  As described above, according to the present invention, an optical sheet for display can be manufactured at a low cost and with high quality by a simpler process than before.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, the configuration of examples (first to sixth embodiments) of display optical sheets manufactured by the method for manufacturing display optical sheets according to the present invention will be described, and then the method for manufacturing these display optical sheets will be described. To do.

  FIG. 1 is a cross-sectional view showing a configuration of an example (first embodiment) of an optical sheet for display according to the present invention. The optical sheet for display 10 is an optical sheet module in which a first diffusion sheet 12, a first prism sheet 14, a second prism sheet 16, and a second diffusion sheet 18 are laminated in order from the bottom. is there.

  The first diffusion sheet 12 and the second diffusion sheet 18 are sheets in which beads are fixed to the surface (one side) of a transparent film (support) with a binder, and have predetermined light diffusion performance. The first diffusion sheet 12 and the second diffusion sheet 18 have different bead diameters (average particle diameter), and light diffusion performances are also different.

  A resin film can be used for the transparent film (support) used for the first diffusion sheet 12 and the second diffusion sheet 18. As the material of the resin film, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyolefin, acrylic, polystyrene, polycarbonate, polyamide, PET (polyethylene terephthalate), biaxially stretched polyethylene terephthalate, Known materials such as polyethylene naphthalate, polyamideimide, polyimide, aromatic polyamide, cellulose acylate, cellulose triacetate, cellulose acetate propionate, and cellulose diacetate can be used. Of these, polyester, cellulose acylate, acrylic, polycarbonate, and polyolefin can be preferably used.

  The bead diameters of the first diffusion sheet 12 and the second diffusion sheet 18 need to be 100 μm or less, and preferably 25 μm or less. For example, the average particle size can be 17 μm within a predetermined distribution range of 7 to 38 μm.

  The first prism sheet 14 and the second prism sheet 16 are lens sheets in which convex lenses formed in one axial direction are adjacently arranged on substantially the entire surface. For example, the pitch is 50 μm and the height of the unevenness. 25 μm, and the apex angle of the convex portion can be 90 degrees (right angle).

  The first prism sheet 14 and the second prism sheet 16 are arranged in a direction in which the axis of the convex lens (prism) is substantially perpendicular. That is, in FIG. 1, the axis of the convex lens of the first prism sheet 14 is arranged in a direction perpendicular to the paper surface, and the axis of the convex lens of the second prism sheet 16 is arranged in a direction parallel to the paper surface. Yes. In FIG. 1, the second prism sheet 16 is shown in a direction different from the actual direction so that it can be understood that the cross section of the second prism sheet 16 is a convex lens.

  The material and manufacturing method of the first prism sheet 14 and the second prism sheet 16 can take various known modes. For example, a sheet-shaped resin material extruded from a die is placed opposite to the transfer roller that rotates at approximately the same speed as the resin material extrusion speed (a prism sheet reverse type is formed on the surface). A method for producing a resin sheet can be employed in which the pressure is sandwiched between nip roller plates rotating at the same speed and the uneven shape on the surface of the transfer roller is transferred to the resin material.

  In addition, a method of manufacturing a resin sheet in which a transfer mold plate (stamper) on which a reversal type of a prism sheet is formed and a resin plate are laminated by hot pressing and press molding by thermal transfer can be employed.

  As a resin material used in such a manufacturing method, a thermoplastic resin can be used, for example, polymethyl methacrylate resin (PMMA), polycarbonate resin, polystyrene resin, MS resin, AS resin, polypropylene resin, polyethylene resin. , Polyethylene terephthalate resin, polyvinyl chloride resin (PVC), thermoplastic elastomer, or a copolymer thereof, cycloolefin polymer, and the like.

  Further, as another manufacturing method, on the surface of the same transparent film (polyester, cellulose acylate, acrylic, polycarbonate, polyolefin, etc.) used for the first diffusion sheet 12 and the second diffusion sheet 18, A method of manufacturing a resin sheet that transfers and forms unevenness on the surface of the uneven roller (the reverse type of the prism sheet is formed on the surface) can be employed.

  More specifically, a transparent film in which an adhesive layer and a resin layer (for example, UV curable resin) are formed in two or more layers is continuously run by sequentially applying an adhesive and a resin to the surface. The transparent film is wound around a rotating concavo-convex roller, the concavo-convex surface of the concavo-convex roller is transferred to the resin layer, and the resin layer is cured in a state where the transparent film is wound around the concavo-convex roller (for example, UV irradiation). The manufacturing method of a concavo-convex sheet can be adopted. Note that no adhesive is required.

  In addition, the manufacturing method of the 1st prism sheet 14 and the 2nd prism sheet 16 is not necessarily limited to said example, If a desired uneven | corrugated shape can be formed on the surface, another manufacturing method can also be employ | adopted. .

  As shown in FIG. 1, the left and right end portions of the display optical sheet 10 are integrated with each other by a joint portion 10 </ b> A. Details of the joint 10A will be described later.

  The display optical sheet 10 described above is disposed, for example, between a light source device and a liquid crystal cell, and is used so as to form a liquid crystal display element as a whole. In this case, in addition to the various merits already described (the optical sheet for display can be manufactured at a low cost and high quality with a simpler process than before), the assemble work of the liquid crystal display element is also very easy. can get.

  Next, another example (second embodiment) of the optical sheet for display according to the present invention will be described. FIG. 2 is a cross-sectional view showing the configuration of the display optical sheet 20. In addition, the same code | symbol is attached | subjected about the same and similar member as FIG. 1 (1st Embodiment), and the detailed description is abbreviate | omitted.

  The display optical sheet 20 is an optical sheet in which a diffusion sheet 12, a first prism sheet 14, and a second prism sheet 16 are laminated in order from the bottom. The second diffusion sheet 18 is omitted when a wide diffusion performance is not required as in the display optical sheet 10 described above.

  The display optical sheet 20 described above is disposed, for example, between the light source device and the liquid crystal cell, and is used so as to form a liquid crystal display element as a whole, as in the first embodiment.

  Next, still another example (third embodiment) of the optical sheet for display according to the present invention will be described. FIG. 3 is a cross-sectional view showing a configuration of the display optical sheet 30. In addition, the same code | symbol is attached | subjected about the same and similar member as FIG. 1 (1st Embodiment) and FIG. 2 (1st Embodiment), and the detailed description is abbreviate | omitted.

  The optical sheet for display 30 is an optical sheet in which the first diffusion sheet 12, the prism sheet 14, and the second diffusion sheet 18 are laminated in order from the bottom.

  In the display optical sheet 30, the second prism sheet 16 is omitted when the diffusion performance in the direction perpendicular to the paper surface as in the display optical sheet 10 described above is not required.

  The display optical sheet 30 described above is disposed, for example, between the light source device and the liquid crystal cell, and used to form a liquid crystal display element as a whole, as in the first embodiment.

  Next, still another example (fourth embodiment) of the optical sheet for display according to the present invention will be described. FIG. 4 is a cross-sectional view showing a configuration of the display optical sheet 40. In addition, the same code | symbol is attached | subjected about the member similar to FIG. 1 (1st Embodiment), FIG. 2 (2nd Embodiment), etc., and the detailed description is abbreviate | omitted.

  The display optical sheet 40 is an optical sheet in which the diffusion sheet 12 and the prism sheet 14 are laminated in order from the bottom. The second diffusion sheet 18 is omitted when a wide diffusion performance is not required as in the display optical sheet 10 described above, and a diffusion performance in a direction perpendicular to the paper surface as in the display optical sheet 10 described above is required. If not, the second prism sheet 16 is omitted.

  The display optical sheet 40 described above is arranged, for example, between the light source device and the liquid crystal cell and used to form a liquid crystal display element as a whole, as in the first embodiment.

  Next, another example (fifth embodiment) of the optical sheet for display according to the present invention will be described. FIG. 5 is a cross-sectional view showing the configuration of the display optical sheet 50. In addition, the same code | symbol is attached | subjected about the member similar to FIG. 1 (1st Embodiment), FIG. 2 (2nd Embodiment), etc., and the detailed description is abbreviate | omitted.

  The optical sheet for display 50 is an optical sheet in which the first prism sheet 14, the second prism sheet 16, and the diffusion sheet 18 are laminated in order from the bottom. The first diffusion sheet 12 is omitted when a wide diffusion performance is not required as in the optical sheet for display 10 described above.

  The display optical sheet 50 described above is disposed between the light source device and the liquid crystal cell, for example, as in the first embodiment, and used to form a liquid crystal display element as a whole.

  Next, another example (sixth embodiment) of the optical sheet for display according to the present invention will be described. FIG. 6 is a cross-sectional view showing the configuration of the display optical sheet 50. In addition, the same code | symbol is attached | subjected about the member similar to FIG. 1 (1st Embodiment), FIG. 2 (2nd Embodiment), etc., and the detailed description is abbreviate | omitted.

  The display optical sheet 60 is an optical sheet in which the first prism sheet 14 and the diffusion sheet 18 are laminated in order from the bottom. The first diffusion sheet 12 is omitted when a wide diffusion performance like the above-described optical sheet for display 10 is not required, and a diffusion performance in a direction perpendicular to the paper surface like the optical sheet for display 10 described above is required. If not, the second prism sheet 16 is omitted.

  The display optical sheet 60 described above is disposed, for example, between the light source device and the liquid crystal cell, and used to form a liquid crystal display element as a whole, as in the first embodiment.

  Although there is no restriction | limiting in particular in the planar size of each optical sheet 10-60 for display demonstrated above, It can be made to respond | correspond to the size of the backlight unit of various displays (liquid crystal display element etc.). The effect of the present invention is considered to increase as the plane size of the display becomes larger.

  Next, the decompression process (exhaust device 48), which is a characteristic part of the present invention, will be described. FIG. 7 is a plan view showing an outline of the exhaust device 48, and FIG. 8 is a cross-sectional view taken along line AA of FIG. Here, the display optical sheet 30 of FIG. 3 is used as an example of the display optical sheet.

  The exhaust device 48 includes an edge holder 48A, which is a long member having a substantially U-shaped cross section (channel shape), and a suction hose 48B attached to the center of the edge holder 48A so as to communicate with the inside of the edge holder 48A. It comprises pressure reducing means (not shown) for sucking the suction hose 48B in the direction of the thick arrow in the figure.

  The display optical sheet 30 is placed on a display optical sheet manufacturing line 11 (see FIG. 9) described later or a conveyor line (not shown) of the display optical sheet manufacturing line 61 (see FIG. 10). .

  The edge holder 48A is formed of a flexible member such as a rubber material. The inner dimension in the vertical direction of the edge holder 48A in FIG. 8 is formed to be equal to or smaller than the thickness of the display optical sheet 30 (also referred to as the same thickness). As a result, the edge holder 48A urges and sandwiches the display optical sheet 30 in the thickness direction, and there is little air leakage when the exhaust device 48 sucks the inside of the display optical sheet 30. Can be maintained.

  Although the illustration of the length direction of the suction hose 48B is omitted, the other end of the suction hose 48B is connected to a decompression means (not shown). In addition, although illustration is abbreviate | omitted, it is preferable to attach a vacuum degree measurement means (Bourdon tube pressure gauge, mercury manometer, etc.) in the middle of suction hose 48B.

  As the decompression means, various suction means such as a blower and a vacuum pump (rotary vacuum pump) can be employed. In the exhaust device 48, a high-pressure blower can be preferably used in that the suction air volume can be increased.

  The operation of the exhaust device 48 described above can be performed by operating the pressure reducing means. By the operation of the pressure reducing means, the space between the optical sheets of the display optical sheet 30 is reduced, and air is sucked from the left end of the display optical sheet 30 shown in FIG.

  As a result, the optical sheets of the display optical sheet 30 come into close contact with each other, and an air flow from the left end toward the edge holder 48 </ b> A is formed inside the display optical sheet 30. And by this air flow, various contaminations (dust etc.) existing inside the optical sheet for display 30 are sucked and removed.

In the exhaust device 48, a high pressure blower is used as a decompression unit, an air suction pressure (measured pressure by the vacuum degree measurement unit) is set to 100 to 10,000 Pa, and an air suction amount is set to 100 mm per unit length of the optical sheet 30 for display. It is preferable to set it as 1-30 m < ³ > / min.

  Further, in the decompression step or the previous step of the decompression step, it is possible to remove the static electricity by blowing static electricity on each optical sheet by a static elimination means (for example, a static elimination device manufactured by Sicid Electric Co., Ltd., trade name: WINSTAT series). Since the effect of a pressure reduction process is improved, it is preferable.

  When performing static elimination in the previous process, it is only necessary to provide a gap between the optical sheets and blow static electricity to each optical sheet. When performing static elimination in this decompression process, the left side of the display optical sheet 30 in FIG. It is only necessary to supply static electricity to the inside.

  Next, the manufacturing method of the optical sheet for a display is demonstrated. This manufacturing method can be commonly applied to the above-described display optical sheets 10 to 60. However, for the convenience of description, the case where the manufacturing method is applied to a four-layer display optical sheet (first embodiment) will be described. To do.

  FIG. 9 is a configuration diagram of a display optical sheet production line 11 applied to the first production method. The rolls 12B, 14B, 16B, and 18B provided at the left end of the figure are respectively the first diffusion sheet 12, the first prism sheet 14, and the second prism sheet 16 shown in FIG. And a roll around which the second diffusion sheet 18 is wound.

  The rolls 12B, 14B, 16B, and 18B are respectively supported by the rotation shafts of unillustrated feeding means, and the first diffusion sheet 12 and the first prism sheet 14 are provided by the rolls 12B, 14B, 16B, and 18B. The second prism sheet 16 and the second diffusion sheet 18 can be fed out at substantially the same speed.

  The fed first diffusion sheet 12, first prism sheet 14, second prism sheet 16, and second diffusion sheet 18 are supported by guide rollers G, G... They are stacked on the upstream side of the exhaust device 48 described above (stacking step).

  In the exhaust device 48, the inside of the optical sheet laminate is sucked in a reduced pressure state, so that when the protective sheet is peeled off from the flat lens (first prism sheet 14, second prism sheet 16) or the like, dust or the like is caused by peeling charging. Even if this contamination is adhered to the flat lens, various kinds of contamination such as dust are discharged to the outside of the laminated body by this suction, so that defects caused by dust generation can be effectively suppressed.

  A laser head 24 is provided downstream of the exhaust device 48 so that the optical sheet 30 for display can be cut and welded simultaneously.

  As a laser beam irradiation apparatus including the laser head 24, a YAG laser irradiation apparatus having a wavelength of 355 to 1064 nm, a semiconductor laser irradiation apparatus, a carbon dioxide laser irradiation apparatus having a wavelength of 9 to 11 μm, and the like can be employed. The oscillation method may be continuous oscillation or pulse oscillation. However, in order to perform welding at approximately the same time as cutting, doting by pulse oscillation is preferable because the appearance is good.

  The output and frequency required for welding (joining process) almost simultaneously with the cutting (cutting process) vary depending on the material feed speed, laser beam scanning speed, material thickness, etc. Good welding results can be obtained under the conditions of 50 W and a frequency of 100 kHz or less.

  The laser head 24 is attached to an X drive robot axis or an XY drive robot axis that can move in the X direction (sheet width direction) or the XY direction, and can perform positioning to an arbitrary position and arbitrary trajectory movement. The entire laser head 24 may be moved according to the irradiation pattern of the laser beam, but the laser head 24 is separately placed (fixed), and only the laser beam is guided by the optical fiber to simplify the moving mechanism in the XY directions. You can also

  It is also possible to provide a known mechanism (suction device or the like) that sucks smoke generated during cutting by the laser head 24 and during welding.

  Laser light is irradiated from the laser head 24 to the cut and bonded portions on the periphery of the laminate, and the periphery of the laminate is cut into a product size and melted and joined while moving at a constant irradiation spot.

Through the above steps, the optical sheet for display 10 (see FIG. 1) is formed. The cut and joined optical sheet for display 10 is conveyed onto the conveyor 26 and stopped. The optical sheets for display 10 on the conveyor 26 are sequentially stacked on the stacking device 32 by the suction lateral transfer device 28.

  On the other hand, the sheet laminate 34 from which the display optical sheet 10 is punched out by the laser head 24 is wound around a winding roll 36 of a winding device (not shown in detail).

  According to the above-described optical sheet manufacturing method (first manufacturing method), the following effects 1) to 3) can be obtained.

1) Scratch failure reduction effect If the upper and lower surfaces of the lens sheets (the first prism sheet 14 and the second prism sheet 16) are scratched, the scratches are conspicuous because of the lens effect. On the other hand, when the bottom surface of the diffusion sheet (the first diffusion sheet 12 or the second diffusion sheet 18) is scratched, the scratches are not noticeable because the light is diffused. For this reason, preventing damage to the lens sheet leads to reduction of scratch failure. Although scratches are often attached during handling after sheet processing, since the diffusion sheet serves as a protective sheet by combining the lens sheet with the diffusion sheet, failure due to scratches can be reduced. In particular, the effect is great in the optical sheet for display 10 of the first embodiment (see FIG. 1) and the optical sheet for display 30 of the second embodiment (see FIG. 3) in which the lens sheet does not appear on the surface.

2) Effect of reducing assembly man-hour For example, when the optical sheet for display 10 of the first embodiment (see FIG. 1) is used in the assembly of the liquid crystal display element, the assembly man-hour is only one process for incorporating the optical sheet for display 10. On the other hand, when the conventional product is used, the first diffusion sheet is incorporated ⇒ The first lens sheet is peeled off from the back surface protective sheet ⇒ The first lens sheet is peeled off from the surface protective sheet ⇒ The first lens sheet is incorporated ⇒ Eight steps are required: peeling off the back surface protection sheet of the second lens sheet → peeling the surface protection sheet of the second lens sheet → incorporation of the second lens sheet → incorporation of the second diffusion sheet. Thus, according to the first manufacturing method, a significant reduction in assembly man-hours can be achieved, and the product cost can be reduced.

3) Reduction effect of protective sheet In many cases, a protective sheet is attached to the front and back of a lens sheet to prevent scratches. This protective sheet is discarded after the lens sheet is assembled, and is very wasteful. The product of the present invention can save the protective sheet by using the diffusion sheet as a protective sheet.

  Specifically, one protective sheet can be reduced in the display optical sheet 40 (see FIG. 4) of the fourth embodiment and the display optical sheet 60 (see FIG. 6) of the sixth embodiment, and the third embodiment. In the display optical sheet 30 (see FIG. 3), two protective sheets can be reduced, and the display optical sheet 20 (see FIG. 2) of the second embodiment and the display optical sheet 50 of the fifth embodiment (FIG. 5). 3), three protective sheets can be reduced, and four protective sheets can be reduced in the display optical sheet 10 of the first embodiment (see FIG. 1).

  Next, another manufacturing method (second manufacturing method) of the optical sheet for display will be described. FIG. 10 is a configuration diagram of a display optical sheet production line 61 applied to the second production method. In addition, the same code | symbol is attached | subjected about the member similar to the optical sheet manufacturing line 11 for display of FIG. 9 (1st manufacturing method), and the detailed description is abbreviate | omitted.

  In the display optical sheet production line 61, the laser head 78 is a device for fusing two or more stacked sheets. That is, the laser head 78 fuses the laminated body of the first diffusion sheet 12, the first prism sheet 14, the second prism sheet 16, and the second diffusion sheet 18.

  Note that, unlike the laser head 24 in the display optical sheet manufacturing line 11 of FIG. 9 (first manufacturing method), the laser head 78 is used only for the joining process, and the cutting process is performed by the punching press device 49. However, the basic specifications and peripheral configuration of the laser head 78 are substantially the same as those in the first manufacturing method.

  The setting condition of the laser head 78 may be determined within a range in which the fused portion is not melted by heat. If necessary, the bonded portion may be cooled by an air cooling mechanism such as air blowing after bonding (fusion). .

  In the punching press device 49 downstream of the laser head 78, the blade is inserted into the central portion of the bonded fused portion, so that the entire punched sheet (display optical sheets 10 to 60) or any arbitrary A composite sheet in which only the edge portions of the sides are bonded can be obtained.

  Next, regarding the planar arrangement of the sheet (optical sheet for display 10) punched out from the laminate of the first diffusion sheet 12, the first prism sheet 14, the second prism sheet 16, and the second diffusion sheet 18. explain.

  FIG. 11 is a diagram for explaining a planar arrangement of a sheet (display optical sheet 10) punched from a laminate.

  11A shows a state in which cutting is performed in a direction parallel to and orthogonal to the transport direction of the laminate, and FIG. 11B shows a state in which cutting is performed obliquely with respect to the transport direction of the stack. Indicates.

  As described above, according to the present invention, an optical sheet for display can be manufactured at a low cost and with high quality by a simpler process than before.

  Moreover, according to this invention, the following effects are also acquired.

1) Improvement of Product Value by Cost Reduction and Thinning Optical sheets used for large liquid crystal televisions need rigidity, and therefore, the thickness of the support is about twice that of the conventional one. However, since the optical sheet according to the present invention is a composite of the sheets, it can have sufficient rigidity without increasing the thickness of each sheet, and the thickness of each layer can be reduced.

2) Improved performance by preventing reduction of light collection effect Some products have a matte backside to prevent scratches on the lens sheet (to make the scratches less noticeable). The optical sheet according to the present invention is not necessary, and not only the production cost can be reduced, but also the light collection effect can be prevented from being reduced by the mat treatment, and the performance is improved.

  As mentioned above, although each example of embodiment of the optical sheet for a display which concerns on this invention was demonstrated, this invention is not limited to the example of the said embodiment, Various aspects can be taken.

  For example, in the example of the present embodiment, the exhaust device 48 having the configuration shown in FIGS. 7 and 8 is employed, but other types of decompression means may be used. For example, a configuration in which a vacuum chamber that covers the optical sheet laminate in the full width direction is provided and vacuum suction of the optical sheet laminate in the interior can be adopted.

  Moreover, in the example of this embodiment, although the joining process is performed after the decompression process, the decompression process and the joining process can be performed simultaneously. For example, when an adhesive or a double-sided tape is used in the joining step, the optical sheets are sealed with the adhesive or the double-sided tape, making it difficult to secure an air flow path. In such a configuration, if the decompression step and the joining step are performed at the same time, an air flow path in the decompression step can be secured, and no problems occur.

  The adhesive used in the bonding process is preferably an adhesive that is bonded with the aid of heat or a catalyst. Specifically, general adhesives such as silicon adhesives, polyurethane adhesives, polyester adhesives, epoxy adhesives, cyanoacrylate adhesives, and acrylic adhesives can be used.

  Since the display optical sheets 10 to 60 may be used at high temperatures, an adhesive that is stable even at room temperature to 120 ° C. is preferable. Among these, epoxy adhesives are excellent in strength and heat resistance, and can be suitably used. Since the cyanoacrylate adhesive is excellent in immediate effect and strength, it can be used for the production of an efficient optical sheet for display. Polyester adhesives are particularly suitable because they are excellent in strength and processability.

  These adhesives are roughly classified into a thermosetting type, a hot melt type, and a two-component mixed type depending on the bonding method, and a thermosetting type or a hot melt type capable of continuous production is preferably used. Whatever adhesive is used, the coating thickness is preferably 0.5 μm to 50 μm.

  The double-sided tape used in the joining process is one in which an adhesive is applied to both sides. As the adhesive for this double-sided tape, a highly adhesive acrylic copolymer resin can be used, but other adhesives such as silicone, natural rubber and synthetic rubber can be used. It is preferable to use an acrylic pressure-sensitive adhesive in consideration of physical strength such as property, price and the like.

  Further, the layer configuration of the optical sheet for display is not limited to the example of the embodiment, and for example, protective sheets can be laminated on the upper and lower surfaces.

  Even if it is the above structures, it acts similarly to this embodiment and the same effect is acquired.

[Create prism sheet]
Prism sheets used for the first prism sheet 14 and the second prism sheet 16 were prepared. This prism sheet is used in common for the first prism sheet 14 and the second prism sheet 16.
-Preparation of resin solution The compounds shown in the table of Fig. 12 were mixed at the stated weight ratios, heated to 50 ° C and dissolved by stirring to obtain a resin solution. In addition, the name and content of each compound are as follows.

EB3700: Everkrill 3700, manufactured by Daicel UC Corporation,
Bisphenol A type epoxy acrylate,
(Viscosity: 2200 mPa · s / 65 ° C)
BPE200: NK ester BPE-200, manufactured by Shin-Nakamura Chemical Co., Ltd.
Ethylene oxide-added bisphenol A methacrylate,
(Viscosity: 590 mPa · s / 25 ° C)
BR-31: New Frontier BR-31, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Tribromophenoxyethyl acrylate,
(Solid at normal temperature, melting point 50 ° C or higher)
LR8883X: Lucirin LR8883X, a photo radical generator manufactured by BASF Corporation,
Ethyl-2,4,6-trimethylbenzoylethoxyphenyl osphine oxide MEK: methyl ethyl ketone The prism sheet was manufactured using the prism sheet manufacturing apparatus having the configuration shown in FIG.

  As the sheet W, a transparent PET (polyethylene terephthalate) film having a width of 500 mm and a thickness of 100 μm was used.

  As the embossing roller 83, a roller made of S45C having a length (width direction of the sheet W) of 700 mm and a diameter of 300 mm and having a surface material of nickel was used. Grooves with a pitch of 50 μm in the roller axial direction were formed on the entire circumference of the surface of the roller by cutting using a diamond tool (single point). The cross-sectional shape of the groove is a triangular shape with an apex angle of 90 degrees, and the bottom of the groove is a triangular shape with a 90 degree without a flat portion. That is, the groove width is 50 μm and the groove depth is about 25 μm. Since this groove is endless with no seam in the circumferential direction of the roller, the embossing roller 83 can form a lenticular lens (prism sheet) having a triangular cross section on the sheet W. The surface of the roller was plated with nickel after the grooves were processed.

  As the coating means 82, a die coater using an extrusion type coating head 82C was used.

  As the coating solution F (resin solution), a solution having the composition described in the table of FIG. 11 described above was used. The supply amount of each coating liquid F to the coating head 82C was controlled by the supply device 82B so that the wet thickness of the coating liquid F (resin) was 20 μm after drying the organic solvent.

  As the drying means 89, a hot air circulation type drying apparatus was used. The temperature of the hot air was 100 ° C.

  As the nip roller 84, a roller having a diameter of 200 mm and a silicon rubber layer having a rubber hardness of 90 formed on the surface thereof was used. The nip pressure (effective nip pressure) for pressing the sheet W by the embossing roller 83 and the nip roller 84 was 0.5 Pa.

A metal halide lamp was used as the resin curing means 85, and irradiation was performed with an energy of 1000 mJ / cm ² .

As described above, a prism sheet having a concavo-convex pattern was obtained.
[Creation of the first diffusion sheet 12]
A first diffusion sheet 12 (under diffusion sheet) was produced by forming each layer in the order of the undercoat layer, the backcoat layer, and the light diffusion layer by the following method.
・ Undercoat layer A liquid A as an undercoat layer coating solution having the following composition was applied on one side of a polyethylene terephthalate film (support) having a thickness of 100 μm with a wire bar (wire size: # 10), and 2 at 120 ° C. The film was dried for 5 minutes to obtain an undercoat layer having a film thickness of 1.5 μm.

(Coating solution for undercoat layer)
Methanol 4165g
Julimer SP-50T (Nippon Pure Chemicals) 1495g
339 g of cyclohexanone
Julimer MB-1X (Nippon Pure Chemicals Co., Ltd.) 1.85g
(Organic particles: polymethylmethacrylate cross-linked type, spherical ultrafine particles with a weight average particle size of 6.2 μm)
-Back coat layer On the opposite side of the support on which the undercoat layer was applied, the B liquid as the back coat layer coating liquid having the following composition was applied with a wire bar (wire size: # 10), and 120 ° The film was dried at C for 2 minutes to obtain a backcoat layer having a thickness of 2.0 μm.

(Coating solution for back coat layer)
4171g of methanol
Julimer SP-65T (Nippon Pure Chemicals) 1487g
340 g of cyclohexanone
Julimer MB-1X (Nippon Pure Chemicals Co., Ltd.) 2.68g
(Organic particles: polymethylmethacrylate cross-linked type, spherical ultrafine particles with a weight average particle size of 6.2 μm)
-Light diffusing layer C liquid as a light diffusing layer coating solution having the following composition is applied to the undercoat layer side of the support prepared as described above with a light bar (wire size: # 22) and dried at 120 ° C for 2 minutes. To obtain a light diffusion layer. In addition, although mentioned later, this light-diffusion layer obtained what apply | coated immediately after preparing C liquid, and what apply | coated after adjusting C liquid and leaving still for 2 hours, respectively.

(Coating liquid for light diffusion layer)
Cyclohexanone 20.84g
Disparon PFA-230 Solid content 20% by mass 0.74g
(Particle sedimentation inhibitor: fatty acid amide, manufactured by Enomoto Kasei Co., Ltd.)
Acrylic resin (Dianar BR-117, manufactured by Mitsubishi Rayon Co., Ltd.) 20% by mass methyl ethyl ketone solution 17.85 g
Julimer MB-20X (Nippon Pure Chemicals) 11.29g
(Organic particles: polymethylmethacrylate cross-linked type, spherical ultrafine particles with a weight average particle diameter of 18 μm)
F780F (Dainippon Ink Co., Ltd.) 0.03g
(Methyl ethyl ketone 30% by mass solution)
[Creation of Second Diffusion Sheet 18]
The same conditions and the same as those of the first diffusion sheet 12 except that the addition amount of the Jurimer MB-20X in the light diffusion layer of the first diffusion sheet 12 is changed from 11.29 g to 1.13 g. A second diffusion sheet 18 (upper diffusion sheet) was produced by flow.

[Method for producing optical sheet for display and evaluation result]
In Examples 1 and 2 and Comparative Examples 1 to 3 that will be individually described below, display optical sheets were prepared and incorporated into a backlight unit of a liquid crystal display element to evaluate defects.

  In each of the examples and comparative examples, 10 sets of A4-size display optical sheets were prepared and evaluated. The evaluation results are summarized in the table of FIG.

Example 1
An optical sheet for display (optical sheet module) formed by laminating the first diffusion sheet 12 and the second diffusion sheet 18 was prepared.

  Two sheets of the first diffusion sheet 12 and the second diffusion sheet 18 were superposed and subjected to pressure reduction treatment from the side. Thereby, the shift | offset | difference of two layers was prevented and the cutting | disconnection was attained stably. When applied to the backlight unit, the amount of bright spots and dark spots due to dust and scratches decreased, and a stable sample was obtained and the yield increased (defect 0 was 10/10).

(Example 2)
An optical sheet 30 for display (optical sheet module) in which the first diffusion sheet 12, the first prism sheet 14, and the second diffusion sheet 18 are laminated is prepared.

  Three sheets of the first diffusion sheet 12, the first prism sheet 14, and the second diffusion sheet 18 are overlapped, subjected to a decompression process from the side, and continued to be decompressed and cut to cut and integrate the three sheets. went. There was no deviation between the optical sheets, and it was possible to cut stably. Further, after the cutting, the three sheet surfaces were uniformly adhered without bending. Moreover, the amount of bright spots and dark transitions due to dust and scratches was reduced, and a sheet with no brightness unevenness was obtained (defect 0 was 10/10).

(Comparative Example 1)
In Example 1, sheet cutting was performed without suction from the side. There was a sample in which the uppermost sheet slipped during cutting. Furthermore, there were many bright spots, and scratches between sheets considered to be caused by dust were observed (defect 0 was 3/10).

(Comparative Example 2)
In Example 2, after suctioning from the side to bring the three sheets into close contact, the suction was stopped and the sheet was cut. There is no deviation between the sheets, but the cut sheets are separated and are not integrated. In order to make these composite, the outer peripheral part of the sheet was ultrasonically fused and fixed. Deflection occurred in the sheet fusion portion, and uneven brightness occurred (Defect 0 was 4/10).

  From the above evaluation results, the effect of the present invention was confirmed.

Sectional drawing of embodiment of the optical sheet for a display manufactured by the manufacturing method of the optical sheet for a display which concerns on this invention Sectional drawing of other embodiment of the optical sheet for displays Sectional drawing of other embodiment of the optical sheet for a display. Sectional drawing of other embodiment of the optical sheet for a display. Sectional drawing of other embodiment of the optical sheet for a display. Sectional drawing of other embodiment of the optical sheet for a display. Plan view showing the outline of the exhaust system AA line sectional view of FIG. Configuration diagram of optical sheet manufacturing line for display applied to first manufacturing method Configuration diagram of optical sheet production line for display applied to second production method The figure explaining the planar arrangement | positioning of the sheet | seat punched out from a laminated body in the 1st and 2nd manufacturing method. Table showing the composition of the resin liquid used to create the prism sheet Configuration diagram of prism sheet manufacturing equipment Table showing evaluation results of Examples and Comparative Examples

Explanation of symbols

  10, 20, 30, 40, 50, 60 ... optical sheet for display, 12 ... first diffusion sheet, 14 ... first prism sheet, 16 ... second prism sheet, 18 ... second diffusion sheet, 48 ... Exhaust device, 48A ... Edge holder, 48B ... Suction hose

Claims (8)

A laminating step of laminating two or more optical sheets having a planar size of the sheet equal to or larger than the product size;
A depressurizing step of sucking the inside of the optical sheet laminate to a depressurized state;
A bonding step of bonding the laminated body of the optical sheets at at least one place on the periphery;
And a cutting step of cutting a peripheral edge of the laminate of the optical sheets into a product size.   The method for producing an optical sheet for display according to claim 1, wherein, in the decompression step, the optical sheets of the laminate are temporarily fixed by suction under reduced pressure.   The method for producing an optical sheet for display according to claim 1, wherein in the decompression step, suction is performed from an end of the laminate.   The manufacturing method of the optical sheet for a display according to any one of claims 1 to 3, wherein the optical sheet is bonded to at least one side of a peripheral edge in the bonding step.   The method for manufacturing an optical sheet for display according to any one of claims 1 to 3, wherein the optical sheet is bonded at four peripheral edges in the bonding step.   The method for producing an optical sheet for display according to claim 1, wherein the optical sheet includes a diffusion sheet.   The method for manufacturing an optical sheet for a display according to any one of claims 1 to 6, wherein the optical sheet includes a lens sheet in which convex lenses formed in a uniaxial direction are adjacently arranged on substantially the entire surface.   The method for producing an optical sheet for display according to any one of claims 1 to 7, wherein the optical sheet includes two or more sheets having the same optical performance.

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