JP2011206934A - Roll die for processing plastic sheet including optical function, method of manufacturing optical sheet using the roll die, the optical sheet obtained in the manufacturing method, backlight unit for liquid crystal display device using the optical sheet and the liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding roll die for processing to efficiently obtain optical sheets capable of achieving high front surface luminance, reducing uneven luminance and individually adjusting a high luminance view angle region even when the number of the optical sheets is reduced, the optical sheet, a method of manufacturing the sheet, an edge light type backlight or a direct backlight using the sheet, and a liquid crystal display device.SOLUTION: In the molding roll die 1 for processing a plastic sheet, a processing layer 4 comprising metal is provided on a cylinder base material, and the processing layer 4 includes recessed groove groups extended to two or more directions intersecting with each other and repeatedly arranged to form ridge shapes. The depth of one recessed groove group is set deeper than that of the other recessed groove groups, and the extension direction forms an angle of -60 to 60° with respect to the rotating direction of the cylinder. Moreover, this invention relates to the method of manufacturing the optical sheet using the roll die 1, the optical sheet obtained in the manufacturing method, the backlight for the liquid crystal display device using the optical sheet, and the display device.

Description

  The present invention is a light diffusion sheet that diffuses light from a light source and smoothes the brightness for use in a liquid crystal display element, a display such as an organic EL display, etc. Molding roll mold for processing a plastic sheet having an optical function such as, a method for producing an optical sheet using the molding roll mold for plastic sheet processing, an optical sheet obtained by the production method, and the optical The present invention relates to a backlight unit of a liquid crystal display device using a sheet, and further to a liquid crystal display device using the optical sheet.

  As a thin display device, liquid crystal display devices are widely used for notebook computers, various monitors, televisions, information displays, etc., and from the viewpoint of reducing environmental burden and power consumption, as a backlight light source for display devices, The replacement of light-emitting diodes (LEDs) from cold-cathode tubes, which has been the mainstream so far, is increasing.

  There are two types of light source arrangement methods, the edge light type arranged on the end face of the display device and the direct type installed behind the display surface, but the edge light type capable of reducing the thickness of the entire display device has become widespread.

  However, in the edge light type, since the light from the light source is once introduced into the light guide plate and emitted at a wide angle in the display screen direction by the reflection pattern, the uniformity of the luminance distribution on the entire light emitting surface is relatively high. The brightness in the front direction is lowered. Therefore, in order to increase the brightness in the front direction of the display screen, the light with a condensing cylindrical lens group extending in the horizontal direction of the display screen in order to refract and collect the light emitted at various angles in the front direction of the screen A sheet and an optical sheet having a condensing cylindrical lens group extending in the vertical direction of the display screen are used in an overlapping manner (see Patent Document 1). However, with this method, the brightness in the front direction of the screen can be increased significantly, but the viewing angle in the horizontal or vertical direction that can maintain high brightness is narrowed, and the brightness suddenly decreases just a little away from the front direction. Therefore, there is a problem in screen quality depending on the use of the display device.

  Also, in the direct type, if a point light source LED is used, the backlight light source can be turned on and off for each screen area according to the display image, improving the image quality, but the directivity of light from the LED light source In order to achieve luminance uniformity across the entire surface, after reducing the light source image with a diffuser plate with a reflection pattern corresponding to the position of the light source, a diffusion sheet for achieving uniform luminance over the entire surface, It is necessary to superimpose a light collecting sheet for increasing the brightness in the front direction of the display screen (see Patent Document 2). These not only hinder the thinning of the display device, but also lead to an increase in member costs and assembly costs.

  On the other hand, in order to improve the luminance in the front direction of the display screen and reduce the luminance unevenness and color unevenness even when the number of optical sheets used is reduced, in the edge light type backlight, the two extending directions of the condensing lens are different. Instead of superimposing the optical sheet, a concave shape of an inverted quadrangular pyramid made of ultraviolet and / or radiation curable resin is arranged on a transparent substrate, that is, a solid having ridge lines extending in two orthogonal directions It has been proposed to use an optical sheet having a shape (see Patent Document 3).

  An optical sheet having a three-dimensional shape having ridge lines in two directions extending in a direction intersecting with the arrangement direction of each point light source even in a direct type backlight in which LEDs of three primary colors are used as light sources and arranged behind the display surface Has been proposed (see Patent Document 4).

  However, it has the appropriate thickness (150μ or more) and rigidity necessary to suppress the wrinkling and deflection of the optical sheet that leads to the deterioration of the display screen quality even in the temperature rising atmosphere due to the heat from the LED as the light source. In addition, a specific example of manufacturing an optical sheet having a three-dimensional shape having a ridge line group consisting of two or more extending directions intersecting each other on the surface by extrusion molding of a thermoplastic resin having high productivity There is no known method.

JP 10-506500 Gazette JP 2005-1117023 A JP-A-8-271888 JP 2009-49895 A

  An object of the present invention is to solve the above-described conventional problems and achieve the following objects. That is, the present invention is a liquid crystal display device using an edge-light type backlight or a direct type backlight with a highly directional light source, and the front luminance is high and the luminance is reduced even when the number of optical sheets used is reduced. Molding roll mold for optical sheet processing that can reduce unevenness and can individually adjust the high brightness range in the horizontal and vertical viewing angles of the display screen, and optical sheet by extrusion molding using the molding roll mold for processing The manufacturing method of this, the optical sheet obtained by the manufacturing method of this optical sheet, the backlight for liquid crystal display devices using this optical sheet, and a display apparatus are provided.

  The present invention solves such a problem, and one of the inventions is a plastic sheet processing molding roll mold comprising a processing layer made of metal on the cylinder substrate, and the processing layers intersect with each other 2 A groove group that is repeatedly arranged in a bowl shape extending in one or more directions, and one of the groove groups is deeper than the other groove group, and the extending direction is An angle of −60 to 60 ° is formed with respect to the rotation direction of the cylinder.

  Furthermore, in the molding roll mold for processing a plastic sheet, any groove group formed in the processed layer is repeatedly arranged in a bowl shape without a flat gap portion between the groove grooves.

  Furthermore, in the molding roll mold for plastic sheet processing, the depth of the deepest groove in the processed layer is 10 to 500 μm, and the ratio to the depth of the other groove group is 100: 5 to 100: 95. It is a range, and the crossing angle (narrow angle) of each groove group extending direction is 45 ° to 90 ° with respect to each other.

  Furthermore, in the molding roll mold for plastic sheet processing, the cross-sectional shape of the groove forming the groove group extending in two or more directions in the processed layer is an isosceles triangle, an unequal triangle, a quadratic curve, two It is a shape of a combination of a secondary curve and an isosceles triangle or an unequal polygon.

  Further, by using a molding die for plastic sheet processing, the concave grooves formed in the processing layer of the molding roll mold for plastic processing are reversely transferred to at least one surface of the thermoplastic resin sheet by extrusion molding of the thermoplastic resin. It is characterized by making it.

  Further, the optical sheet is obtained by reversely transferring the groove group on at least one surface of the thermoplastic resin sheet by the specific manufacturing method.

  Furthermore, in the backlight unit of the liquid crystal display device, the specific optical sheet is used.

  Furthermore, in the liquid crystal display device, the specific backlight unit is used.

  According to the present invention, when manufacturing an optical sheet having a three-dimensional shape having two or more fine ridge lines having extending directions intersecting each other on at least one surface, one groove group is formed in a processed layer. The plastic sheet processing molding roll in which the depth of the groove is deeper than the depth of the other groove groups, and the groove grooves are repeatedly arranged in a bowl shape extending in two or more directions intersecting each other By using a mold, the concave groove pattern of the processed layer is reversely transferred to at least one surface of the optical sheet, and the reversely transferred uneven shape causes light condensing and diffusibility as an optical sheet. Can do. At this time, by adjusting the depth difference and the crossing angle between intersecting concave grooves within a specific range, the enhancement direction of these optical function characteristics and the strength of the optical function characteristics between directions can be adjusted. Become. That is, the viewing angle dependence of the luminance in the horizontal and vertical directions of the screen can be adjusted with a single optical sheet while increasing the luminance in the front direction of the liquid crystal screen, which is optimal for each liquid crystal display device. Light condensing and diffusing properties can be achieved with only a few optical sheets, and the liquid crystal display device can be reduced in thickness, member cost, and assembly cost can be reduced.

  Further, the extending direction of the deepest groove group formed in the processed layer of the roll mold is oriented at an angle of −60 to 60 ° with respect to the rotation direction of the cylinder of the roll mold. As the roll rotates, when the grooves in the processing layer are sequentially filled with molten thermoplastic resin, the air in the grooves is successively changed from the shallow grooves to the deep grooves with high openness. As a result, the air is hardly trapped between the resin and the mold. Thereby, an optical sheet having desired optical characteristics can be produced efficiently.

Conceptual diagram of molding roll mold for plastic sheet processing of the present invention Explanatory drawing which expanded the concept of the ditch pattern on the surface of the mold roll for plastic sheet processing of the present invention Explanatory drawing which expanded the concept of the surface where the optical element of the optical sheet of the present invention was formed Method for producing optical sheet of the present invention by extrusion molding

(Figure 1)
1: Roll mold 2: Roll holding unit 3: Holding layer 4: Processing layer 5: Rotating shaft (FIG. 2)
1: Die 2: First roll 3: Second roll A: Surface shaping roll B: Winding roll 6: Take-off roll

Hereinafter, the present invention will be specifically described.
FIG. 1 is an external view of an embodiment of a molding roll mold for processing a plastic sheet according to the present invention. FIG. 2 is an explanatory view showing an example of a groove pattern on the surface of the molding roll mold for plastic sheet processing of the present invention. FIG. 3 is an enlarged view illustrating an example of the surface on which the optical element of the optical sheet of the present invention is molded. FIG. 4 is an explanatory view showing an example of a method for producing the optical sheet of the present invention by extrusion molding.

  The forming roll mold 1 includes a roll holding portion 2 and a holding layer 3 made of metal around the roll holding portion 2, and a processed layer 4 having a concave groove formed outside thereof. The holding layer 3 is required to have sufficient mechanical strength and rigidity, and when iron or an alloy thereof is used as a material, it is preferable that the holding layer 3 has a thickness of approximately 13 mm or more. The outer diameter tolerance of the roll is preferably ± 0.5 mm or less from the viewpoint of manufacturing an optical sheet. In order to exhibit the function as an optical sheet, it is necessary to reversely transfer the dense groove shape of the processed layer on the cylinder base material to the surface of the thermoplastic resin sheet, and temperature management in the transfer process is important. Therefore, in order to adjust the roll temperature to a constant level, it is preferable that the roll holding part has a double structure and a pipe for circulating the heat medium is installed inside. The roll support 5 may be made of a material and a structure that obtains sufficient strength to support the roll.

  The processing layer 4 on the roll surface needs to be able to accurately process dense concave grooves, and also requires a processing step at a high temperature when reversely transferring the concave grooves to the thermoplastic resin sheet surface. Further, it is preferably made of a copper material or a phosphorus-nickel material, and the thickness of the processed layer is preferably 0.3 to 3 mm.

  In actual use, it is preferable to provide a protective layer 6 in order to maintain durability and productivity as a mold, and chrome plating is suitable for a protective layer made of copper or phosphorus-nickel. is there.

  As a method of forming a groove group repeatedly arranged in a bowl shape extending in two or more directions intersecting each other in the processed layer, a precision lathe is used and a groove groove in one extending direction is formed by a diamond tool. Then, the groove groups in the extending direction different from the extending direction of the first groove group are sequentially cut. The groove shape and the cutting depth are different for each groove group having a different extending direction. Different diamond tools may be used, or the depth of the groove group in each extending direction may be adjusted by changing only the feed depth with the same diamond tool.

  First, a parent die is prepared by cutting a group of concave grooves that are repeatedly arranged in a bowl shape extending in two or more directions intersecting each other on a precision lathe, and then using the parent die, the unevenness of the parent die is formed. It is also possible to employ a method in which an inverted reversing die is fabricated, and this reversing die is reversely transferred to the copper plating layer of the roll processing layer to produce a forming roll processing mold having a desired shape.

  The processing layer of the molding roll mold for plastic sheet processing of the present invention has a groove group repeatedly arranged in a bowl shape extending in two or more directions intersecting each other, and the depth of one groove group is included. Is deeper than the depth of the other groove group, and it is essential that the extending direction forms an angle of −60 to 60 ° with respect to the rotation direction of the cylinder. Two or more directions different from each other are provided on at least one surface of the optical sheet obtained by reverse transfer using the molding roll mold for processing a plastic sheet by being different from each other in the extending directions of these groove groups. Inverted shape extending to the end of this is formed. In addition, an optical element with a reversed three-dimensional surface area that has a great influence on the development of optical characteristics such as light collecting properties and light diffusibility can be formed for each extending direction, so that it can be used as an optical sheet for backlights of liquid crystal display devices. In such a case, it becomes possible to adjust the enhancement direction of the optical function characteristics and the strength of the optical functionality between the directions.

  In addition, since the extending direction of the deepest groove group forms an angle of −60 to 60 ° with respect to the rotation direction of the cylinder, the thermoplastic resin melted or softened in the groove groove of the processed layer is formed. When filling, the air that existed in the groove is smoothly removed, and the transfer of optical elements onto the surface of the optical sheet is improved, giving the optical characteristics as designed. It becomes easy to do.

  It is preferable that any concave groove group of the processed layer is repeatedly arranged in a bowl shape without a flat gap between the concave grooves, whereby the surface of the optical sheet obtained by the molding roll mold for plastic sheet processing can be obtained. Can form optical elements at a high density, and can further enhance the efficiency of optical performance.

  When the depth of the deepest groove group in the working layer of the plastic sheet processing molding roll mold of the present invention exceeds 500 μm, optical homogeneity due to the optical element obtained by reversing and transferring one groove group is present. If the thickness is less than 10 μm, the reversal transferability by the roll mold is lowered, so 10 to 500 μm is preferable. More preferably, it is 15-300 micrometers.

  Further, when the ratio of the deepest groove group to the depth of the other groove group is less than 100: 5 or 100: 95 or more, the optical sheet obtained by reversal transfer with the roll mold is used for the liquid crystal display device. When used as an optical sheet for a backlight, it becomes difficult to adjust the direction of emphasis of optical function characteristics and the strength of optical functionality between directions, and the range is from 100: 5 to 100: 95. Is preferred. Furthermore, when the ratio exceeds 100: 95, that is, when the difference in depth between the groove groups becomes small, each groove group passing through the deepest groove group described above at the time of reverse transfer to the thermoplastic resin sheet surface. This will hinder the elimination of the air in the interior, and the transfer rate may decrease.

  The cross-sectional shape of the groove forming the groove group extending in two or more directions in the processing layer of the molding roll mold for plastic sheet processing is that of the optical element formed on the surface of the optical sheet obtained by reverse transfer. From the viewpoint of light collecting property, light diffusibility, etc., it is preferably an isosceles triangle, an unequal triangle, a quadratic curve, a quadratic curve and a combination of an isosceles triangle or an unequal polygon, and these The cross-sectional shape may be different or the same depending on the groove group. In the same case, the ratio of depth to width may be the same or different.

  An optical sheet obtained by forming an optical element by using the molding roll mold for processing a plastic sheet of the present invention and transferring the groove group pattern of the processed layer of the roll mold to at least one surface of a thermoplastic resin sheet. The production method is particularly preferably an extrusion method in terms of productivity.

  As an example of the manufacturing method of the optical sheet by extrusion molding, as shown in FIG. 4, the sheet-like molten thermoplastic resin extruded from the die (1) of the extruder is used as the first roll (2) and the second roll ( The step of 3) passing the gap between the two rolls to obtain a rolled sheet-like molten thermoplastic resin, the rolled sheet-like molten thermoplastic resin as it is to the second roll (3), then 3 A process of sequentially circumscribing and transporting the third roll (4) to the main roll, and subsequently peeling the surface-formed sheet-like molten thermoplastic resin from the third roll (4) by the winding rolls (5a, 5b). It consists of the process of transferring.

  The molding roll mold for processing a plastic sheet of the present invention is used as the second roll (2) or the third roll (3), and is a fine material that is important for expression of optical properties formed in the processed layer of the roll mold. In order to obtain an optical sheet with high accuracy and a high reversal transfer rate, it is particularly preferable to use a group of concave grooves as the third roll (3).

  Since the first roll (2) is an important roll for determining the thickness of the sheet, a mirror-finished roll is preferably used instead of a surface-processed roll. Further, when the thickness accuracy is insufficient due to the influence of the linear pressure, a drum-shaped crowning roll can be used. The 2nd roll (3) can also use the embossing roll for transferring the mirror surface roll for creating a smooth surface, a mat | matte, embossing other than the roll metal mold | die of this invention. Furthermore, it is more preferable to install a take-off roll as a fourth roll in front of the vicinity of the peeling line so that the thermoplastic resin sheet formed with a fine uneven shape can be more smoothly peeled off from the third roll if necessary. .

  In the present invention, the thermoplastic resin used in the production of the optical sheet is not particularly limited as long as it is transparent and has an appropriate strength as a main component of the optical sheet. For example, polycarbonate resin; acrylic resin such as polymethyl methacrylate; styrene resin such as polystyrene, polyvinyl toluene, and poly (p-methylstyrene); MS resin (copolymer of methyl methacrylate and styrene); norbornene resin; poly An arylate resin; a polyethersulfone resin; a mixed resin of two or more of these can be used. A polycarbonate resin, a styrene resin, or a norbornene resin is preferably used. Among these, polycarbonate resin is particularly preferable as a resin for an optical sheet because it is excellent in transparency, heat resistance, and workability and has a good balance.

  The thermoplastic resin used in producing the optical sheet of the present invention includes tris (2,4-di-tert-butylphenyl) phosphite, tetrakis to prevent a decrease in molecular weight and a deterioration in hue during molding. Phosphorus-containing thermal stabilizers such as (2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite and bis (2,4-di-tert-butylphenyl) -biphenylphosphonite, rolls Incorporates a release agent represented by a fatty acid ester compound such as stearic acid monoglyceride, stearic acid triglyceride, sorbitan monostearate, pentaerythritol tetrastearate, etc. be able to.

  In the optical sheet of the present invention, an ultraviolet absorber, an antistatic agent, a lubricant, and a near infrared absorber can be used within a range that does not impair the gist of the present invention. It is preferable that a layer containing an absorber, a layer containing an antistatic agent, or both an ultraviolet absorber-containing layer and an antistatic agent-containing layer are formed.

  Conventionally known UV absorbers and antistatic agents can be used. For example, as a UV absorber, a salicylic acid phenyl ester UV absorber; a benzophenone UV absorber; a triazine UV absorber; a benzotriazole UV absorber; a cyclic imino ester UV absorber; and a hindered phenol structure in the molecule Low molecular ultraviolet absorbers such as hybrid ultraviolet absorbers having a hindered amine structure; triphenylcyanoacrylate ultraviolet absorbers; oxalic anilide ultraviolet absorbers; malonic ester ultraviolet absorbers; and these low molecular ultraviolet absorbers Can be used, such as a polymer ultraviolet absorber (eg, Halus Hybrid (registered trademark) manufactured by Nippon Shokubai Co., Ltd.). Of these, triphenylcyanoacrylate ultraviolet absorbers; oxalic anilide ultraviolet absorbers; malonic ester ultraviolet absorbers are preferred because they absorb less light in the visible light region. When used for a polycarbonate resin, an oxalic anilide ultraviolet absorber; a malonic ester ultraviolet absorber is more preferable.

  Antistatic agents include alkyl sulfonic acids, alkyl benzene sulfonic acids, esters thereof, or metal salts such as Li, Na, Ca, Mg, and Zn salts; anionic surfactants such as phosphate esters of higher alcohols; Cationic surfactants such as tertiary amines, quaternary ammonium salts, cationic acrylic ester derivatives, cationic vinyl ether derivatives; amphoteric salts of alkylamine betaines, amphoteric salts of alanine carboxylates or sulfonates, alkylimidazolines Amphoteric surfactants such as amphoteric salts; Nonionic surfactants such as polyoxyethylene adducts of fatty acid polyhydric alcohol esters and alkyls (amines); Polyamide elastomers such as polyether ester amides and polyester amides can be used . In addition, conductive resins such as polyvinyl benzyl type cationic resins and polyacrylic acid type cationic resins can also be used as an antistatic agent.

  Although the usage-amount of a ultraviolet absorber and an antistatic agent can be suitably adjusted according to each function, Usually, it is about 1-50 mass parts with respect to 100 mass parts of resin which comprises each layer.

  These layers having different functions can be obtained by bonding a sheet in which a UV absorber or an antistatic agent is uniformly dispersed in the same resin as the thermoplastic resin constituting the sheet to the optical sheet or the like by thermocompression bonding or an adhesive. Good. Or you may dry or cool, after apply | coating the paste containing an ultraviolet absorber etc. on an optical sheet. Moreover, you may coextrude the thermoplastic resin which comprises a sheet | seat, and the thermoplastic resin which mix | blended the ultraviolet absorber and the antistatic agent. The thickness of the layer having these different functions may be appropriately adjusted according to each function, etc., but is usually preferably about 1 to 50 μm.

  The thickness of the optical sheet is not particularly limited as long as it is about 0.10 to 10 mm. However, when used as an optical sheet for a flat panel display such as a liquid crystal display device, it is desired to reduce the weight and thickness of the display device itself. The sheet thickness is preferably 6 mm or less, more preferably 5 mm or less, and still more preferably 4 mm or less.

  Moreover, although various optical sheets may be comprised only with transparent resin, in order to adjust light diffusibility, you may provide the light-diffusion layer based on the light-scattering effect | action of a light diffusable particle. The light diffusion layer is the entire sheet, only the thickness of the optical element formed by reversal transfer of the groove group of the processed layer of the roll mold, the entire surface other than the thickness where the optical element is formed, the surface of the light emitting surface Only on the surface of the light incident surface, or may be arranged uniformly or randomly on the intermediate layer.

  The thickness in the case of providing the light diffusion layer can be appropriately adjusted according to the thickness of the optical sheet and is not particularly limited, but is usually 0.001 mm or more. If it is less than 0.001 mm, the light diffusing action cannot be exhibited sufficiently.

  Examples of the material of the light diffusing particles used include thermoplastic resins such as (meth) acrylic resins, styrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins, amino resins, and thermosetting. Glass; clay compounds such as smectite and kaolinite; inorganic oxides such as silica and alumina; and composites of the above resins and inorganic compounds. Of these materials, (meth) acrylic resins, silicone resins, and silica are particularly suitable.

  The blending amount of the light diffusing fine particles in the light diffusing layer needs to be appropriately adjusted depending on the thickness of the light diffusing layer to be formed, the size of the light diffusing fine particles, the refractive index difference from the thermoplastic resin constituting the sheet, and the like. However, the amount is usually 0.005 parts by mass or more and 20 parts by mass or less, more preferably 0.01 parts by mass or more and 10 parts by mass or less, with respect to 100 parts by mass of the thermoplastic resin constituting the optical sheet. If the amount used is less than 0.005 parts by mass, the light diffusion effect may not be sufficiently exerted even when the entire optical sheet is used as a light diffusion layer. On the other hand, when the amount used exceeds 20 parts by mass, it may be difficult to extrude the optical sheet, or the amount of transmitted light may be reduced, resulting in a decrease in luminance.

  The optical sheet obtained by using the molding roll mold for processing a plastic sheet of the present invention is particularly suitable for various optical sheets of a flat panel display, and diffuses light from a light source constituting a backlight of a liquid crystal display device. It is useful for condensing light in a specific direction. More specifically, in a direct type backlight, light from a linear light source composed of cold cathode fluorescent lamps or LED arrays arranged in a line or point light sources such as dispersed LEDs is uniformly distributed over the entire display screen. In an edge light type backlight in which the light source is arranged on the end face of the display device as a light diffusing plate arranged to have luminance or a lens sheet for increasing the luminance in the front direction of the display screen, the end face Is used to deflect the light from the light source arranged in the front of the display screen and to superimpose it on the light guide plate installed for the purpose of equalizing the brightness of the display screen, thereby improving the brightness in the front direction of the screen It can be used effectively for lens sheets.

  When obtaining a light diffusing plate for a direct type backlight using the molding roll mold for plastic sheet processing of the present invention, the depth of the deepest groove group of the roll processing layer depends on the arrangement of the light source and the light output characteristics. And the depth of each groove group and the crossing angle (narrow angle) of each groove group extending direction can be optimized so as to obtain a uniform luminance distribution. Is reverse-transferred so that the crossing angle (narrow angle) of the convex extending direction obtained by reversing and transferring the deepest groove group with respect to the extending direction of the light source can be set to -30 ° to 30 °. Is particularly preferable in terms of improving the uniformity of luminance.

  In addition, when obtaining a lens sheet to be superimposed on the light guide plate of the edge light type backlight, a normal image is obtained within the fixed viewing angle range in the horizontal direction and the vertical direction of the screen, respectively, while improving the luminance in the front direction of the display screen. It is required to secure a luminance level for obtaining the above. Therefore, according to the application and specifications of each display device, the ratio of the depth of the deepest groove group of the roll processing layer to the depth of other groove groups, and the crossing angle (narrow angle) of each groove group extending direction However, in a normal display screen, the horizontal direction requires a certain level of brightness over a wider viewing angle range than the vertical direction. It is preferable to perform reverse transfer so that the crossing angle (narrow angle) in the extending direction of the convex shape obtained by reverse transfer of the deep groove group on the processed surface can be set to -30 ° to 30 °.

  The optical sheet obtained by using the molding roll mold for plastic sheet processing of the present invention is used as a diffusion plate and / or a lens sheet of a direct type backlight to form a backlight unit of a liquid crystal display device, and further the backlight When forming a liquid crystal display device using a unit, in order to further improve the optical characteristics of the optical sheet of the present invention, a known microlens sheet, a lenticular lens formed with a convex shape extending only in one direction It is preferable to appropriately select and combine a sheet, a prism sheet, a light diffusion sheet, and a reflective polarizing film. Similarly, when used as a lens sheet on a light guide plate of an edge light type backlight, a known microlens sheet, a lenticular lens sheet or prism sheet having a convex shape extending only in one direction, light, It is preferable to appropriately select and combine a diffusion sheet and further a reflective polarizing film.

Hereinafter, the present invention will be described based on examples.
<Example 1>
A roll holding portion 2 and a holding layer 3 made of stainless steel are formed around the roll holding portion 2. A copper plating layer having a thickness of 500 μm is formed outside the roll holding portion 2, and a precision lathe is used. Parallel to the direction, the groove shape of an inverted isosceles triangle having a 90 ° apex angle and a depth of 40 μm is sequentially applied to the entire surface without a gap, and then the cross-sectional shape is in a direction intersecting the groove groove at 90 °. An inverted isosceles triangular groove group having an apex angle of 90 ° and a depth of 50 μm was formed on the entire surface without any gaps. Finally, a chrome plating layer with a thickness of 1 μm is applied as a protective layer, and it has a group of grooves repeatedly arranged in two or more directions intersecting each other, and the depth of one groove group However, the molding roll mold (I) for processing a plastic sheet was obtained which is deeper than the depth of the other groove group and whose extending direction forms an angle of 0 ° with the rotation direction of the cylinder.

<Example 2>
Similarly to Example 1, a copper plating layer having a thickness of 500 μm was formed, and a cross-sectional shape in the direction of 45 ° with respect to the rotation direction of the roll was first set to a vertical angle of 90 ° on the copper plating layer using a diamond lathe using a precision lathe. Concave groove group of inverted isosceles triangle with a depth of 25μm is applied to the entire surface sequentially without any gaps, and then the inverted isosceles with a 90 ° apex angle and a depth of 50μm in a direction intersecting the groove group at 90 ° Triangular grooves were formed on the entire surface without any gaps. Finally, a chrome plating layer with a thickness of 1 μm is applied as a protective layer, and has a group of grooves repeatedly arranged in two or more directions crossing each other, and the depth of one groove group is Thus, a molding roll mold (II) for processing a plastic sheet was obtained, which was deeper than the depth of the other groove group and the extending direction formed an angle of 45 ° with the rotation direction of the cylinder.

<Example 3>
100 parts by weight of polycarbonate resin (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics) and 0.1 part by weight of a phosphorus-based heat stabilizer (“Irgaphos 168”: manufactured by Ciba Specialty Chemicals) are provided with a vent and a gear pump. The cooling sheet is supplied to an extruder and comprises three cooling roll arrangements and one take-off roll as shown in FIG. 4. The first and second rolls are mirror flat rolls, and the third roll is the plastic sheet of Example 1. Using the molding roll mold (I) for processing, respectively, the extruder outlet temperature is 265 ° C, the first roll temperature is 140 ° C, the second roll temperature is 180 ° C, and the third roll temperature is 195 ° C. Optical sheet (A) having a thickness of 1.0 mm in which convex isosceles triangle groups having a vertical angle of 90 ° in a cross section with different heights perpendicular to the extending direction are formed It was produced.

<Example 4>
Sections with different heights perpendicular to each other on the surface under the same extrusion molding conditions as in Example 3, except that the third roll is the molding roll mold (II) for plastic sheet processing of Example 2 Produced an optical sheet (B) having a thickness of 0.5 mm in which convex isosceles triangles having an apex angle of 90 ° were formed.

<Example 5>
100 parts by mass of polycarbonate resin (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.1 part by mass of a phosphorus-based heat stabilizer (“Irgaphos 168”: manufactured by Ciba Specialty Chemicals), and crosslinked methacryl as a light diffusing agent Except that 0.5 parts by mass of resin fine particles (Epaster MA1002, manufactured by Nippon Shokubai Co., Ltd.) are blended, the cross-sections having different heights perpendicular to each other in the extending direction are perpendicular to the surface. An optical sheet (C) having a thickness of 1.0 mm in which isosceles triangle groups were formed was produced.

<Comparative Example 1>
A roll holding portion 2 and a holding layer 3 made of stainless steel are formed around the roll holding portion 2. A copper plating layer having a thickness of 500 μm is formed outside the roll holding portion 2, and a precision lathe is used. A groove with an inverted isosceles triangle with an apex angle of 90 ° and a depth of 50 μm parallel to the direction is applied to the entire surface without any gap, and then the apex angle is 90 ° and the depth in a direction intersecting the groove groove at 90 °. A 40 μm inverted isosceles triangular groove group is formed on the entire surface without any gaps, and finally a 1 μm thick chrome plating layer is applied as a protective layer, and is repeatedly arranged in a bowl shape extending in two or more directions intersecting each other The depth of one of the groove groups is deeper than the depth of the other groove group, and the extending direction forms an angle of 90 ° with the rotation direction of the cylinder. A molding roll mold (I) for processing a comparative plastic sheet was obtained.

<Comparative example 2>
100 parts by weight of polycarbonate resin (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics) and 0.1 part by weight of a phosphorus-based heat stabilizer (“Irgaphos 168”: manufactured by Ciba Specialty Chemicals) are provided with a vent and a gear pump. The three cooling roll arrangements shown in FIG. 2 are supplied to the extruder. The first and second rolls are mirror flat rolls, and the third roll is a molding roll metal for comparative plastic sheet processing of Comparative Example 1. Using the mold (I), the extruder outlet temperature is 265 ° C., the first roll temperature is 140 ° C., the second roll temperature is 180 ° C., and the third roll temperature is 195 ° C., and the extending directions are orthogonal to each other on the surface. An optical sheet (D) having a thickness of 1.0 mm in which convex isosceles triangles having a cross section of different heights and an apex angle of 90 ° was formed was manufactured. Deflated in the recessed groove of the layer becomes insufficient, defect occurs in the transferred shape on the sheet surface.

<Examples 6 to 10>
As a light source, a plurality of LED arrays are arranged on the upper end surface in the horizontal direction of the screen, and a 24 type edge light comprising a 4 mm-thick light guide plate installed to deflect light from the LEDs in the front direction and to diffuse the entire surface. The optical sheet (A), the optical sheet (B), and the optical sheet (C) obtained in Example 3 and Example 4 were superposed on the light guide plate using a type backlight, and the front luminance (optical sheet) Brightness in the normal direction) and horizontal and vertical viewing angles with a luminance of 1500 cd / cm 2 or less were measured with a surface luminance meter made by Konica Minolta, and the light collection effect in the front direction of the optical sheet was Table 1 shows the results of measuring the effect of adjusting the viewing angle that can ensure a constant luminance in the horizontal and vertical directions of the screen.

<Comparative Example 3>
In the same manner as in Examples 5 to 8, the light collection effect in the front direction of the optical sheet (C) obtained in Comparative Example 2 and the viewing angle that can ensure a constant luminance in the horizontal and vertical directions of the screen, respectively. The adjustment effect was measured and the results are shown in Table 1.

<Comparative example 4>
In the same manner as in Examples 5 to 8, the prism portion has an apex angle of 90 °, a pitch of 50 μm, and a height of 25 μm. In the vertical direction, the effect of adjusting the viewing angle capable of ensuring a constant luminance was measured, and the results are shown in Table 1.

<Comparative Example 5>
In the same manner as in Examples 5 to 8, two prism sheets of Comparative Example 4 were overlapped so that the extending directions of the prisms were orthogonal to each other, the light collection effect in the front direction, and the horizontal and vertical directions of the screen Thus, the viewing angle adjustment effect capable of ensuring a constant luminance was measured, and the results are shown in Table 1.

  By using the molding die for plastic sheet processing and molding of the present invention, it becomes possible to obtain an optical sheet in which optical characteristics such as light condensing property and light diffusing property can be controlled for each viewing direction with high production efficiency. By using this optical sheet for a display device, etc., it is possible to achieve optimum light condensing and diffusing properties according to the specifications of the device with only a few optical sheets, and the liquid crystal display device can be reduced in thickness, member cost, and assembly cost. Reduction effect is achieved.

Claims (8)

  The cylinder base material is provided with a processing layer made of metal, and the processing layer has a groove group repeatedly arranged in a bowl shape extending in two or more directions intersecting each other, and one of the groove groups A forming roll for plastic sheet processing, characterized in that the depth is deeper than the depth of the other groove group and the extending direction forms an angle of -60 to 60 degrees with respect to the rotation direction of the cylinder. Mold.   2. The molding roll mold for plastic sheet processing according to claim 1, wherein any of the concave groove groups of the processed layer is repeatedly arranged in a bowl shape without a flat gap portion between the concave grooves.   The depth of the deepest groove in the processed layer is 10 to 500 μm, the ratio to the depth of other groove groups is in the range of 100: 5 to 100: 95, and each groove group extends. The molding roll mold for plastic sheet processing according to claim 1, wherein crossing angles (narrow angles) of directions are 45 ° to 90 ° with respect to each other.   The cross-sectional shape of the groove forming the groove group extending in two or more directions in the processed layer is an isosceles triangle, an unequal triangle, a quadratic curve, a quadratic curve and an isosceles triangle or an unequal polygon. The molding roll mold for processing a plastic sheet according to any one of claims 1 to 3, wherein the molding roll mold is any one of a combination.   Using the molding roll mold for processing a plastic sheet according to claims 1 to 4, the concave groove of the processed layer is reversely transferred to at least one surface of the thermoplastic resin sheet by extrusion molding of a thermoplastic resin. A method for manufacturing an optical sheet.   An optical sheet obtained by the manufacturing method according to claim 5.   A backlight unit of a liquid crystal display device, wherein the optical sheet according to claim 6 is used.   A liquid crystal display device comprising the backlight unit according to claim 7.

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