JP2014058145A - Method for manufacturing optical pattern sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical pattern sheet capable of transferring a pattern of a pattern roll in a high precision based on an extrusion molding method.SOLUTION: The method for manufacturing an optical pattern sheet comprises a step of extruding a sheet from a T die of an extrusion molder, a pattern sheet molding step of molding an optical pattern sheet by transferring a pattern of a pattern roll onto the sheet extruded from the T die by nipping the sheet with a press roll and the pattern roll, and a step of conveying and taking up the molded pattern sheet; the optical pattern sheet is manufactured by using, at the pattern sheet molding step, a pattern roll constituted as a plate following the passage of a roll through a tube onto which an advanced pattern has been provided.

Description

  The present invention relates to a plastic sheet used for a liquid crystal television, illumination, and the like, and an optical pattern sheet manufacturing method and apparatus for providing a three-dimensional pattern on the surface of a film.

  Conventionally, a sheet and a film having a prism shape on the surface for the purpose of improving the brightness of a liquid crystal television (hereinafter, the sheet and the film are collectively referred to as a sheet) (Patent Document 1), and a microlens for preventing moire An optical pattern sheet (Patent Document 2) provided with a shape has been used as a backlight member of a liquid crystal television. On the other hand, the use of an optical pattern sheet provided with a pattern is being studied in order to improve the light extraction efficiency in illumination using organic EL, which is expected to spread in the future (Patent Document 3).

  As a method for producing these optical pattern sheets, two methods of an ultraviolet molding method and an extrusion molding method have been proposed.

  In the UV molding method, the pattern of the pattern roll can be transferred by uniformly applying UV curable resin to a substrate made of polyethylene terephthalate, etc., and irradiating the pattern roll with an arbitrary pattern while irradiating with UV light. it can. At present, optical pattern sheets having prism and microlens shapes are mainly manufactured by this ultraviolet molding method.

  When manufactured by this UV molding method, it is possible to transfer the pattern of the pattern roll with high accuracy (the transfer rate is 99% to 100%), but the manufacturing cost becomes high, and the annual rate decreases at 10%. It is impossible to follow the cost trend of LCD TVs. Reasons for the high cost of the UV molding method include the use of an expensive UV curable resin, the process of extruding a base material made of polyethylene terephthalate, etc., the process of applying and curing the UV curable resin to transfer the pattern For example, the number of steps increases.

  On the other hand, the extrusion molding method is a method in which pellet-shaped resin is kneaded with an extruder, discharged from a T-die, and supplied between a pressing roll and a pattern roll arranged in parallel to each other, and the pattern of the pattern roll is transferred with the narrow pressure. It is. When manufactured by the extrusion molding method, the extruded sheet is an optical pattern sheet, so it is possible to avoid the use of expensive materials as in the ultraviolet molding method, and the number of processes is one process of extrusion molding. Therefore, the manufacturing cost can be reduced.

  However, although this extrusion method can be manufactured at low cost, it is difficult to transfer the pattern from the pattern roll (about 90% at best), and the sharp shape represented by the prism is transferred with high accuracy. It is difficult to do. Therefore, manufacturers who are considering entering into backlight members for liquid crystal televisions that require optical pattern sheets and light extraction sheet members for organic EL lighting are developing methods that can achieve high transfer rates in extrusion molding. .

  The reason why a high transfer rate cannot be obtained by this extrusion molding method is due to the fluidity of the extruded sheet. In the process where the extruded sheet discharged at a high temperature from the T-die is narrowly pressed by the press roll and the pattern roll having a shape such as a prism and the pattern shape is transferred, the heat of the extruded sheet is instantaneously absorbed by the pattern roll, Its fluidity decreases rapidly. Therefore, even if pattern transfer is attempted at a high narrow pressure, a high transfer rate cannot be obtained due to its low fluidity.

  Therefore, it is conceivable to maintain the fluidity of the extruded sheet in order to obtain a high transfer rate. As a method for this, it is considered to use a heat insulating material (a material having low thermal conductivity) on the surface or inside of the pattern roll. ing. By using this heat insulating material, the transfer of heat from the extruded sheet to the pattern roll is delayed, and a high transfer rate is obtained.

  In patent document 4, the delay of heat transfer is tried by the following three methods.

  As method 1, the surface of the roll is covered with polyimide, epoxy, or the like, and a pattern is imparted to the roll to form a pattern roll. As a result, it has been reported that the transfer rate was higher than that of the metal pattern roll surface.

  As method 2, a part of the inside of the pattern roll is filled with polyimide, epoxy, or the like to form a pattern roll. As a result, even if the surface of the pattern roll is made of metal, it has been reported that a high transfer rate was obtained compared to the case where the inside of the pattern roll was made of only metal.

  As the method 3, a pattern roll is formed by sticking a sheet made of polyimide to which a pattern is provided to a roll. As a result, it has been reported that the transfer rate was higher than that of the metal pattern roll surface.

Japanese Patent Laid-Open No. 9-80209 JP 2006-301582 A JP 2008-230114 A JP-A-9-141757

  The use of a material having low thermal conductivity for the pattern roll is advantageous for pattern transfer, but Patent Document 4 has the following drawbacks.

  When the surface of the roll proposed in Method 1 is covered with low thermal conductivity polyimide and epoxy, there is a problem in pattern application. Since high accuracy is required for the pattern shape of a sheet used for an optical member or the like, it is generally obtained by cutting a roll surface made of copper or the like using a diamond bite. However, polyimide, epoxy, and the like are soft and cannot be cut using a diamond tool. Therefore, in Patent Document 4, a pattern is given using sandblasting, but with this method, the accuracy required for the optical member cannot be obtained.

  When a part of the inside of the roll proposed in the method 2 is filled with low thermal conductivity polyimide and epoxy, there is a problem in the target heat transfer delay. Since the heat of the extruded sheet moves instantaneously when it comes into contact with the material constituting the surface of the pattern roll, a large effect cannot be obtained if it is inside.

  When a sheet proposed in method 3 is pasted, the joint between the sheets becomes a problem. The size of the sheet required as an optical member depends on the product in which it is used. Therefore, the yield is low in the pasting method in which there is a periodic joint defect. Moreover, since it has a joint, a sheet larger than the roll diameter cannot be produced. Furthermore, a high-precision pattern cannot be imparted to the polyimide and the epoxy sheet by cutting or sandblasting as in the method 1.

  The present invention provides a method for producing an optical pattern sheet capable of transferring a pattern of a pattern roll with high accuracy in an extrusion molding method.

  The first invention as means for solving the above-mentioned problems is a step of discharging a sheet with a T-die of an extruder, and the sheet discharged from the T-die is narrowed with a pressing roll and a pattern roll. A pattern sheet forming step of transferring the pattern of the pattern roll and forming the optical pattern sheet; and a method of manufacturing an optical pattern sheet comprising a step of conveying and winding the formed pattern sheet, In the pattern sheet forming step, an optical pattern sheet is manufactured by using a pattern roll formed as a plate by passing a tube provided with a high-level pattern through the roll.

  Moreover, 2nd invention is a manufacturing method of the optical pattern sheet | seat characterized by obtaining the said pattern tube by transferring the surface shape of the metal pattern roll which has an advanced pattern in 1st invention. .

  Moreover, 3rd invention is a manufacturing method of the optical pattern sheet | seat characterized by the said pattern tube consisting of the organic material of low heat conductivity in 1st invention.

  According to the present invention, it is possible to manufacture an optical pattern sheet in which the pattern roll pattern is transferred at a high transfer rate by using a pattern tube made of a material having a low thermal conductivity.

Schematic of an extrusion molding machine equipped with a pattern roll comprising a pattern tube according to the present invention Schematic of peeling pattern tube from metal roll with pattern Schematic of pattern roll with pattern tube inserted

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  As shown in FIG. 1, the extrusion molding apparatus according to the present embodiment includes an extruder 12 for heating and kneading a thermoplastic resin raw material supplied from a raw material hopper 11, a T die 13 for discharging a sheet-like molten resin, and a pattern. It comprises a molding machine comprising a pattern roll 14 and a pressing roll 15 for transferring, a plurality of guide rolls 16 for transporting the optical pattern sheet thus formed, and a winder 17 for winding up the optical pattern sheet. As shown in FIG. 3, the pattern roll 14 is a pattern roll in which a pattern tube 21, which is a tube provided with a pattern, is passed (that is, covered) through a mirror surface metal roll 23 to form a plate.

  As the thermoplastic resin used in the present invention, a resin suitable for manufacturing an optical sheet is selected. For this purpose, it must be a transparent resin and provided with such a degree that heat resistance and moisture resistance can be practically used, for example, in order to increase reliability during use of the incorporated liquid crystal display device. Desired. As such a thermoplastic resin, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), methacrylstyrene (MS), acrylonitrile styrene (AS), and cyclic polyolefin are suitable.

  When the pattern tube 21 is passed through the mirror surface metal roll 23 to form the pattern roll 14, the heat transfer from the extruded sheet to the pattern roll 14 surface is performed from the extruded sheet to the pattern roll made of the metal surface. This is slower than the heat transfer. As a result, high fluidity can be maintained for a long time, and the pattern of the pattern roll 14 is completely transferred to the surface of the extruded sheet.

  The cause of the delay in heat transfer is influenced by the thermal conductivity of the material constituting the pattern tube 21. In general, the thermal conductivity of metal is on the order of 10 W / (m · K) or more. On the other hand, the pattern tube 21 used in the present invention is made of an organic material, and its thermal conductivity is as low as 0.1 W / (m · K) or less. As a result, heat transfer is delayed.

  As shown in FIG. 2, the manufacturing method of this pattern tube 21 can be obtained by transferring the surface shape of the patterned metal roll 22 which is a metal roll having a high-level pattern made of a three-dimensional pattern. First, the pattern is transferred to the surface of the patterned metal roll 22 and a tube material is attached. At this time, it is important to carry out with sufficient care so that air and foreign matter do not enter.

  Moreover, the metal roll 22 with a pattern to be used may be obtained by a known processing method. That is, it is a roll obtained by plating copper on a core such as a steel material and cutting the copper surface into a target shape with a diamond tool.

  Furthermore, the surface of the patterned metal roll 22 may be processed with plating (chromium, nickel, nickel phosphorus, etc.), diamond-like carbon (DLC), or the like for the purpose of improving the peelability of the pattern tube 21.

  Second, the surface of the cured material is polished. Since the mirror metal roll 23 is inserted into the pattern tube 21 obtained in the present invention in the following steps and used, macroscopic surface irregularities may occur on the surface of the pattern roll 14. Therefore, it is preferable to grind to a cylindricity of 50 μm or less, which is the same as that of a normal rubber roll.

  Third, the pattern tube 21 is peeled from the patterned metal roll 22. At this time, it is important not to cut the pattern tube 21 but to peel the pattern tube 21 upside down. Even if the pattern tube 21 is cut and attached to the mirror surface metal roll 23 with an adhesive tape, a joint is formed, and the dimensions of the obtained optical pattern sheet are limited.

  The material constituting the pattern tube 21 may be an organic substance having a low thermal conductivity, and preferably a thermosetting resin (eg, silicone) or an ultraviolet curable resin (eg, acrylic) having excellent moldability. Is to use. The thermosetting resin can be selected depending on the surface roughness and hardness.

  Since the surface roughness is caused by the filler added to the thermosetting resin, it is necessary to add the surface roughness so as not to exceed the required surface roughness. The surface roughness is preferably less than Ra 0.2 μm. If the surface roughness is Ra 0.2 μm or more, light is scattered due to surface irregularities, and the desired optical characteristics may not be obtained.

  The hardness (dilometer type A) is preferably 20 or more and 90 or less. If it is less than 20, the pattern shape of the pattern tube 21 changes due to the narrow pressure of the pressing roll 15. On the other hand, if it is larger than 90, the pattern tube 21 may be wrinkled or broken when it is passed through the mirror surface metal roll 23.

  In order to improve the moldability and workability of the pattern tube 21, the resin in contact with the patterned metal roll 22 has a surface roughness of less than Ra 0.2 μm and a hardness of 20 to 90. It is preferable to increase the strength of the pattern tube 21.

  The thickness of the pattern tube 21 is preferably 100 μm or more and 1000 μm or less. When the pattern tube 21 is passed through the mirror surface metal roll 23, it is not preferable that the thickness is less than 100 μm because wrinkles and breakage occur. Further, the effect of delaying the heat transfer from the extruded sheet to the pattern roll 14 is also low. On the other hand, when the thickness is larger than 1000 μm, when the pattern tube 21 is peeled from the patterned metal roll 22, the difference between the inner diameter and the outer diameter is increased, and the end is warped, which is not preferable.

  The inner diameter of the pattern tube 21 is preferably 0 to -0.5% with respect to the outer diameter of the mirror surface metal roll 23 to be inserted. If it is slightly larger than the outer diameter, the pattern tube 21 is displaced during extrusion, which is not preferable. If only the pattern tube 21 that is slightly larger than the outer diameter of the mirror surface metal roll 23 is obtained, it is preferable to use a sleeve type in which the pattern tube 21 is passed through two rolls.

  On the other hand, if it is smaller than the outer diameter, the pattern of the pattern tube 21 is extended and the shape changes. However, since deformation of ± 1% or less does not significantly affect the optical characteristics, it is preferable to use it while fully considering the target optical characteristics.

  Although the dimension of the pattern tube 21 is not particularly defined, a diameter of 400 mm or less and a length of 1500 mm or less are preferable in consideration of peeling and insertion. If it becomes too large, the tube may sag, wrinkle or break during peeling or insertion.

  In addition, the three-dimensional pattern sheet and film of the optical pattern sheet produced in the present invention are used as optical members for liquid crystal televisions and lighting.

[Example 1]
A polycarbonate resin (Teijin Chemicals Co., Ltd., model number “L-1250Z”), a heat-resistant transparent high-performance resin, is dehumidified and dried at 140 ° C. and 250 Torr for 24 hours, and then a single screw extruder (caliber 32, L / D = 24) A T-die (effective width 330 mm) was attached to and discharged into a sheet. The sheet was discharged from the T die so that the sheet thickness was 250 μm. The pattern roll according to the present invention is obtained by passing a pattern tube through a mirror surface metal roll having a diameter of 300 mm and a width of 400 mm. The pattern tube is made of silicone, and has a thickness of 500 μm, and the pattern shape is an isosceles triangle having a cross-sectional shape of an apex angle of 90 °, a pitch of 50 μm, and a height of 25 μm. The molten resin was narrowed by a pattern roll (temperature 80 to 120 ° C.) and a pressing roll (temperature 60 to 120 ° C.) at a linear pressure of 20 kg / cm to form an optical pattern sheet. The extrusion molding apparatus was operated so that the speed of the operation line was 1.5 m / min.

[Comparative Example 1]
An optical pattern sheet was molded under the same conditions as in Example 1 except that the pattern material of the pattern roll was copper.

  About each optical pattern sheet of Example 1 and Comparative Example 1, the pattern transfer rate was evaluated. The results are shown in Table 1.

  In the above evaluation, the pattern depth was measured about the center of the optical pattern sheet, and the value obtained by multiplying the value obtained by dividing the pattern depth by the pattern depth of the pattern roll by 100 was taken as the pattern transfer rate.

  According to the present embodiment, by using a pattern tube made of a material having a low thermal conductivity, it is possible to transfer the pattern of the pattern roll at a high transfer rate, and to manufacture an optical pattern sheet having an advanced pattern. .

  It can be applied to sheets, films, etc. used for liquid crystal televisions and lighting.

11 Raw material hopper 12 Extruder 13 T die 14 Pattern roll 15 Holding roll 16 Guide roll 17 Winder 21 Pattern tube 22 Patterned metal roll 23 Mirror surface metal roll

Claims (3)

Discharging the sheet with a T-die of an extrusion molding machine;
A pattern sheet forming step of transferring the pattern of the pattern roll by forming the sheet discharged from the T die with a pressing roll and a pattern roll, and forming the pattern into an optical pattern sheet,
A method of manufacturing an optical pattern sheet comprising a step of conveying and winding the molded pattern sheet,
In the said pattern sheet formation process, the manufacturing method of an optical pattern sheet | seat which manufactures an optical pattern sheet | seat using the pattern roll made into the plate by letting the tube which provided the advanced pattern passed to a roll.   2. The method of manufacturing an optical pattern sheet according to claim 1, wherein the pattern tube is obtained by transferring a surface shape of a metal pattern roll having an advanced pattern.   The method for producing an optical pattern sheet according to claim 1, wherein the pattern tube is made of an organic material having low thermal conductivity.