JP2011098479A - Method for manufacturing optical sheet having rugged shape on surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical sheet having rugged shape on a surface, capable of performing highly precise quality control of the optical sheet, and excellent in productivity. <P>SOLUTION: The method for manufacturing the optical sheet 2 includes an extruding process for extruding thermoplastic resin from an extruder in order to obtain a resin sheet 1, and a surface-forming process for obtaining the optical sheet 2 having a rugged surface and a flat surface on the surface by pressure contacting a forming roll 12 having a rugged shape part 30a and a flat part 30b on a forming surface to at least one surface of the resin sheet 1. The flat surface part of the obtained optical sheet 2 is cut off, the optical characteristic of the flat surface part is measured, and the obtained measurement value is fed back, and the manufacturing conditions are adjusted, and thus, highly precise quality control of the optical sheet 2 can be performed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical sheet having an uneven shape such as a triangular cross section on the surface.

  In this specification, the surface roughness Ra and the ten-point average roughness Rz are both values measured in accordance with JIS B0601-1994.

  In recent years, as an optical sheet (light diffusion plate, light guide plate, etc.) used for a backlight for a liquid crystal display device, a cross-sectional shape is formed on the surface of the optical sheet in order to improve optical characteristics such as luminance and luminance uniformity. Is imparted with an irregular shape such as a triangular shape. As a method for imparting such a concavo-convex shape, a fine pattern of concavo-convex is formed on the surface of the resin sheet by sandwiching a resin sheet extruded from a T-die between a molding roll (transfer roll) and a mirror roll. The technique (conventional manufacturing method) is known (see Patent Document 1).

Japanese Patent Laid-Open No. 9-11328

  By the way, as the optical sheet, in order to further improve optical characteristics such as luminance and luminance uniformity, a configuration in which the constituent material of the optical sheet itself has light diffusibility may be adopted. Examples of the means for imparting light diffusibility to the resin as the constituent material of the optical sheet include means for mixing a light diffusing agent with a translucent resin, employing a resin that can be microcrystallized such as propylene resin, and the like. .

  In the case where an optical sheet provided with the light refraction / diffusion effect due to the uneven shape of the surface and the light diffusion effect of the constituent material itself is manufactured by the above-described conventional manufacturing method, the quality control of the obtained optical sheet is performed with high accuracy. For this, it is important to individually perform the quality control of the light diffusion effect of the constituent material itself and the quality control of the light diffusion effect due to the uneven shape of the surface. However, since the surface of the obtained optical sheet has a concavo-convex shape, the obtained optical sheet is used to evaluate the light diffusing effect of the constituent material itself and the light diffusing effect due to the concavo-convex shape of the surface. Can not be done separately.

  Therefore, conventionally, in order to individually perform quality control of the light diffusion effect of the constituent material itself, it is completely separated from the optical sheet production line, and separately used in the production of the optical sheet in a separate process. Test piece sheet for measuring optical properties that is sandwiched between a pair of mirror rolls and does not have an uneven shape on the surface (the surface is a flat surface) (that is, a test piece sheet that can eliminate the influence of the light diffusion effect due to the uneven shape on the surface) ), And the haze and total light transmittance of the test piece sheet were measured, and the quality control of the light diffusion effect of the constituent material itself of the optical sheet as a product was performed based on the measurement data.

  However, the manufacturing conditions such as the heat history (heating temperature, heating time, temperature unevenness) of the test piece sheet preparation are sufficiently the same as the manufacturing conditions such as the heat history (heating temperature, heating time, temperature unevenness) in the production line of the above products. Therefore, the measurement data of the test piece sheet does not accurately reflect the light diffusion performance of the constituent material of the optical sheet itself, and therefore the quality control of the optical sheet is highly accurate. There was a problem that could not be done.

  The present invention has been made in view of such a technical background, and can manufacture an optical sheet having a concavo-convex shape on the surface, capable of performing quality control of the optical sheet with high accuracy and excellent in productivity. It aims to provide a method.

  In order to achieve the above object, the present invention provides the following means.

  [1] A surface molding step for obtaining an optical sheet having a concavo-convex surface and a flat surface formed by molding a synthetic resin using a mold having a concavo-convex portion and a flat portion on the molding surface. The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface characterized by including.

[2] An extrusion process for obtaining a resin sheet by extruding a thermoplastic resin from an extruder;
A surface molding step of obtaining an optical sheet having a concavo-convex shape surface and a flat surface formed on a surface thereof by pressing a forming roll having a concavo-convex shape portion and a flat portion on a molding surface against at least one surface of the resin sheet. The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface characterized by including.

  [3] The method for producing an optical sheet having a concavo-convex shape on the surface according to the item 1 or 2, wherein the flat portion is provided on at least a part of the edge of the molding surface.

  [4] The method for producing an optical sheet having a concavo-convex shape on the surface according to the item 2, wherein the flat portion is provided over the entire circumference of at least one edge of the molding surface of the molding roll.

  [5] The method for producing an optical sheet having a concavo-convex shape on the surface according to any one of items 1 to 4, wherein the flat portion of the molding surface has a width of 5 to 500 mm.

  [6] The manufacturing method of the optical sheet which has uneven | corrugated shape on the surface of any one of the preceding clauses 1-4 whose width | variety of the flat part of the said molding surface is 20-500 mm.

  [7] The flat portion of the molding surface has an uneven shape on the surface according to any one of items 1 to 6 above, wherein the surface roughness Ra is 0.3 μm or less and Rz is 1.0 μm or less. Sheet manufacturing method.

[8] The following formula (1) and the following formula (2) are satisfied when the concave / convex depth of the concave / convex shape portion of the molding surface is “D” and the pitch interval of the concave / convex shape portion is “W”. 8. A method for producing an optical sheet having a concavo-convex shape on the surface according to any one of items 1 to 7 above.
D / W ≧ 0.2 Formula (1)
D ≧ 10 μm (2)

  [9] The method for producing an optical sheet having a concavo-convex shape on the surface according to any one of items 1 to 8, wherein the internal haze of the optical sheet is 3% or more.

  [10] The optical sheet has an internal haze, and the internal haze is developed by the optical sheet containing a light diffusing agent. A method for producing an optical sheet having a shape.

  [11] The optical sheet has an internal haze, and the internal haze is generated by microcrystallization of a resin constituting the optical sheet. A method for producing an optical sheet having a shape.

[12] After the surface molding step, comprising a step of cutting at least a part of the flat surface of the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
The optical sheet having an uneven shape on the surface according to any one of the preceding items 1 to 11, further comprising a feedback adjustment step of adjusting manufacturing conditions based on a measured value of the optical characteristics obtained in the measurement step. Manufacturing method.

[13] In the extrusion step, as the thermoplastic resin, a master batch resin containing at least one resin selected from the group consisting of a styrene resin, an acrylic resin, a polycarbonate, and a cyclic polyolefin, and a light diffusing agent; Using a mixture containing a base resin made of the same resin as the resin constituting the masterbatch resin,
After the surface molding step, comprising a step of cutting at least a part of the flat surface in the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
Any of the preceding items 2 to 11, further comprising a feedback adjustment step of adjusting a mixing ratio of the masterbatch resin and the base resin in the extruder based on the measured value of the optical property obtained in the measurement step. The manufacturing method of the optical sheet which has uneven | corrugated shape on the surface of 1 item | term.

[14] Using a propylene resin as a thermoplastic resin in the extrusion step,
After the surface molding step, comprising a step of cutting at least a part of the flat surface in the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
Based on the measured value of the optical property obtained in the measurement step, one or more production conditions selected from the group consisting of the extrusion port temperature of the die of the extruder, the temperature of the molding roll, and the extrusion speed are adjusted. 12. A method for producing an optical sheet having a concavo-convex shape on the surface according to any one of items 2 to 11, further comprising a feedback adjustment step.

  [15] The method for producing an optical sheet having a concavo-convex shape on the surface according to any one of the above items 12 to 14, wherein the optical characteristic measured in the measurement step is total light transmittance or / and haze.

  [16] The method for producing an optical sheet having a concavo-convex shape on the surface according to any one of the above items 12 to 15, wherein in the cutting step, at least a part of a flat surface of the optical sheet is cut by laser light irradiation.

  [17] A molding roll for producing an optical sheet having a concavo-convex shape on a surface, wherein a concavo-convex shape portion and a flat portion are provided on a forming surface on an outer periphery of the forming roll.

  [18] The molding roll for producing an optical sheet having a concavo-convex shape on the surface thereof, wherein the flat portion is provided over the entire circumference of at least one edge of the molding surface.

  The term “internal haze” means haze measured as follows. That is, an optical sheet is cut into a size of 5 cm × 5 cm to prepare a measurement test piece, the test piece is put in a glass cell having an optical path length of 5 mm, and the refractive index is substantially the same as the test piece (the difference in refractive index is 0 or more). After filling the glass cell with a colorless and transparent liquid (preferably 0.01 or less) (eg, tricresyl phosphate / tri-n-butyl phosphate equal mass mixture if the specimen is made of PMMA) The glass cell was set in a haze meter ("HR-100" manufactured by Murakami Color Research Laboratory Co., Ltd.), and the total light transmittance and diffuse light transmittance were measured in accordance with JIS K7136-2000. The haze value is obtained from the ratio. This value is the internal haze.

  In the invention of [1], an optical sheet having a concavo-convex surface and a flat surface is obtained by molding a synthetic resin using a mold having a concavo-convex portion and a flat portion on the molding surface. Since the manufacturing conditions such as heat history (heating temperature, heating time, temperature unevenness) are the same on the uneven surface and the flat surface of the optical sheet, the flat surface portion of the optical sheet is cut out, By measuring the optical characteristics (haze or / and total light transmittance, etc.) of the flat surface portion, the quality control of the light diffusion effect of the constituent material itself of the optical sheet can be performed with high accuracy. That is, the quality control of the light diffusing effect of the constituent material itself and the quality control of the light diffusing effect due to the uneven shape of the surface can be individually performed with high accuracy. In addition, both the concavo-convex shape portion and the flat portion are provided on the molding surface of the mold, and at the time of manufacturing the optical sheet, a flat surface portion (measurement test piece) for measuring optical characteristics can be simultaneously manufactured in the same process. So it is excellent in productivity.

  In the invention of [2], an optical sheet having a concavo-convex surface and a flat surface formed on its surface is obtained by pressing a forming roll having a concavo-convex portion and a flat portion on the molding surface against at least one surface of the resin sheet. Since the manufacturing conditions such as the heat history (heating temperature, heating time, temperature unevenness) are the same in the uneven surface and the flat surface in the optical sheet, the flat surface portion of this optical sheet is cut out, By measuring the optical characteristics (haze or / and total light transmittance, etc.) of the flat surface portion, the quality control of the light diffusion effect of the constituent material itself of the optical sheet can be performed with high accuracy. That is, the quality control of the light diffusing effect of the constituent material itself and the quality control of the light diffusing effect due to the uneven shape of the surface can be individually performed with high accuracy. In addition, both the concavo-convex shape portion and the flat portion are provided on the forming surface of the forming roll, and at the time of manufacturing the optical sheet, a flat surface portion (measurement test piece) for measuring optical properties can be simultaneously manufactured in the same process. So it is excellent in productivity.

  In the invention of [3], since the flat portion is provided on at least a part of the edge of the molding surface, an optical sheet having a flat surface formed on at least a part of the edge can be obtained. Therefore, it is easy to cut a flat surface portion (test piece for measurement).

  In the invention of [4], since the flat portion is provided over the entire circumference of at least one edge of the forming surface of the forming roll, the flat surface of the optical sheet edge (for measurement) in the continuous flow of the extrusion line. There is an advantage that the cutting operation of the test piece) can be performed.

  In the invention of [5], since the width of the flat portion of the molding surface is 5 to 500 mm, the width of the product portion of the optical sheet can be sufficiently secured, which is economical.

  In the invention of [6], since the width of the flat portion of the molding surface is 20 to 500 mm, the width of the product portion of the optical sheet can be sufficiently secured, and the width of the flat surface portion for measuring optical properties (test piece) ) Can be sufficiently secured, and the measurement of optical characteristics is facilitated.

  In the invention of [7], since the flat portion of the molding surface has a surface roughness Ra of 0.3 μm or less and Rz of 1.0 μm or less, that is, a state close to a mirror surface, the constituent material of the optical sheet When evaluating the light diffusion effect of itself, the influence of light diffusion due to the uneven shape of the surface can be sufficiently eliminated, so the quality control of the light diffusion effect of the constituent material of the optical sheet itself should be performed with higher accuracy. Can do.

  In the invention of [8], when the unevenness depth of the uneven portion of the molding surface is “D” and the pitch interval of the uneven portion is “W”, the relational expression of D / W ≧ 0.2 and D ≧ Since the optical sheet has a structure in which the relational expression of 10 μm is established, the light diffusion performance of the obtained optical sheet is not only the contribution of the light diffusion effect of the constituent material of the optical sheet itself, but also the light diffusion effect due to the uneven shape on the surface of the optical sheet Therefore, when the quality control of the light diffusion effect of the constituent material itself of the optical sheet is performed, the technical significance of applying the manufacturing method of the present invention is extremely large. That is, in the invention of [8], although the relational expression of D / W ≧ 0.2 and the relational expression of D ≧ 10 μm are satisfied, the quality control of the light diffusion effect of the constituent material itself of the optical sheet is achieved. Can be performed with high accuracy.

  In the invention of [9], since the internal haze of the optical sheet is 3% or more, the light diffusion performance of the obtained optical sheet is not limited to the contribution of the light diffusion effect due to the uneven shape of the surface of the optical sheet, but also the optical sheet. The contribution of the light diffusing effect of the component material itself is also large (not negligible), and therefore the technical significance of applying the manufacturing method of the present invention in quality control of the light diffusing effect due to the uneven shape of the surface of the optical sheet. Is extremely large. That is, according to the invention [9], although the internal haze of the optical sheet is 3% or more, the quality control of the light diffusion effect due to the uneven shape on the surface of the optical sheet can be performed with high accuracy. .

  In the invention of [10], since the optical sheet has an internal haze, and the internal haze is expressed by the optical sheet containing a light diffusing agent, the light diffusion performance of the obtained optical sheet is: Not only the contribution of the light diffusion effect due to the uneven shape on the surface of the optical sheet, but also the contribution of the light diffusion effect of the constituent material itself of the optical sheet is large (not negligible), so the light due to the uneven shape on the surface of the optical sheet. When performing the quality control of the diffusion effect, the technical significance of applying the manufacturing method of the present invention is extremely large. That is, according to the invention [10], although the internal haze of the optical sheet is a structure expressed by the optical sheet containing a light diffusing agent, the light diffusion due to the uneven shape on the surface of the optical sheet. The quality control of the effect can be performed with high accuracy.

  In the invention of [11], since the optical sheet has an internal haze, and the internal haze is expressed by microcrystallization of a resin constituting the optical sheet, the light diffusion performance of the obtained optical sheet is Not only the contribution of the light diffusion effect due to the uneven shape on the surface of the optical sheet, but also the contribution of the light diffusion effect of the constituent material itself of the optical sheet is large (not negligible), so the light due to the uneven shape on the surface of the optical sheet. When performing the quality control of the diffusion effect, the technical significance of applying the manufacturing method of the present invention is extremely large. That is, in the invention of [11], although the internal haze of the optical sheet is expressed by the microcrystallization of the resin constituting the optical sheet, the light diffusion due to the uneven shape on the surface of the optical sheet. The quality control of the effect can be performed with high accuracy.

  In the invention of [12], after the surface molding step, the method includes a step of cutting at least a part of the flat surface of the optical sheet, a measurement step of measuring the optical characteristics of the cut flat surface portion, and obtained by the measurement step. Since the feedback adjustment process of adjusting the manufacturing conditions based on the measured values of the optical characteristics is provided, it is possible to manufacture an optical sheet having a concavo-convex shape on the surface, quality-controlled with high accuracy.

  In the invention of [13], after the surface molding step, the method includes a step of cutting at least a part of the flat surface of the optical sheet, a measurement step of measuring optical characteristics of the cut flat surface portion, and obtained by the measurement step. Since it is equipped with a feedback adjustment process that adjusts the mixing ratio of the masterbatch resin and the base resin in the extruder based on the measured values of the optical properties, the surface has an uneven shape that is quality controlled with high accuracy. The styrene resin optical sheet can be produced.

  In the invention of [14], a propylene resin is used as the thermoplastic resin in the extrusion step, and a step of cutting at least a part of the flat surface of the optical sheet is provided after the surface molding step, and the optical characteristics of the cut flat surface portion are obtained. 1 or 2 types selected from the group consisting of the extrusion port temperature of the die of the extruder, the temperature of the forming roll, and the extrusion speed, based on the measured value of the optical properties obtained in the measurement step. Since the feedback adjustment process for adjusting the above manufacturing conditions is provided, it is possible to manufacture a propylene resin-based optical sheet having a concavo-convex shape on the surface, quality-controlled with high accuracy.

  In the invention of [15], since the optical characteristic measured in the measurement step is the total light transmittance or / and haze, the light diffusion effect of the constituent material itself of the optical sheet can be evaluated with higher accuracy.

  [16] In the invention of [16], at least a part of the flat surface of the optical sheet is cut out by laser light irradiation. Therefore, the flat surface of the obtained optical sheet can be obtained regardless of the position of the flat portion on the molding surface. The flat surface portion can be cut out without any trouble at any position.

  In the invention (17) (molding roll), since the concave and convex portion and the flat portion are provided on the molding surface on the outer periphery of the roll, if the optical sheet is produced using this molding roll, the concave and convex surface in the optical sheet is produced. Since the manufacturing conditions such as thermal history (heating temperature, heating time, temperature unevenness) and the like are the same for the flat surface, the flat surface portion of this optical sheet is cut out and the optical characteristics (haze or / and / or) of the flat surface portion are cut out. By measuring the total light transmittance, etc., the quality control of the light diffusion effect of the constituent material itself of the optical sheet can be performed with high accuracy. That is, the quality control of the light diffusing effect of the constituent material itself and the quality control of the light diffusing effect due to the uneven shape of the surface can be individually performed with high accuracy.

  In the invention of [18], since the flat portion is provided over the entire circumference of at least one edge of the molding surface, the flat surface of the edge of the optical sheet (test specimen for measurement) in the continuous flow of the extrusion line There is an advantage that the cutting operation can be performed.

It is a side view which shows the outline of the manufacturing method of the optical sheet which concerns on this invention. It is a perspective view which shows the outline of the manufacturing method of the optical sheet which concerns on this invention. It is a perspective view which shows the forming roll used with the manufacturing method of the optical sheet which concerns on this invention. It is sectional drawing of the YY line in FIG. It is sectional drawing (sectional drawing of an optical sheet) of the XX line in FIG. It is a schematic side view which shows the other example of the manufacturing method of the optical sheet which concerns on this invention.

  The manufacturing method of the optical sheet 2 having a concavo-convex shape on the surface according to the present invention is performed by molding a synthetic resin using the molding die 12 having the concavo-convex shape portion 30a and the flat portion 30b provided on the molding surface 30. It includes a surface molding step for obtaining an optical sheet 2 having an uneven surface 2a and a flat surface 2b.

  According to this manufacturing method, the uneven surface 2a and the flat surface 2b of the optical sheet 2 have the same manufacturing conditions such as heat history (heating temperature, heating time, temperature unevenness), and so on. By cutting out the portion and measuring the optical characteristics (such as haze or / and total light transmittance) of the flat surface portion, the light diffusion effect of the constituent material itself of the optical sheet 2 can be evaluated with high accuracy. Moreover, the light diffusion effect by the uneven | corrugated shape of the surface of the optical sheet 2 evaluates the light diffusion effect as the said optical sheet 2, and subtracts the contribution of the light diffusion effect of the constituent material itself of the optical sheet 2 from this. That can be evaluated. Therefore, according to the present manufacturing method, the quality control of the light diffusing effect of the constituent material itself and the quality control of the light diffusing effect due to the uneven shape of the surface can be individually performed with high accuracy.

  The mold 12 is not particularly limited, and examples thereof include a molding roll, an injection mold, a hot press mold, and a photopolymer mold.

  Although it does not specifically limit as said synthetic resin, For example, a thermoplastic resin, a thermosetting resin, etc. are mentioned.

  A suitable example of a manufacturing method in the case where a molding roll is used as the molding die 12 will be described. First, the configuration of the manufacturing apparatus will be described. As shown in FIGS. 1 and 2, three rolls 11, 12, and 13 are arranged vertically in front of the extruder 10 in the extrusion direction. A first pressure contact roll 11 is disposed above the forming roll 12, and a second pressure contact roll 13 is disposed below the forming roll 12. The outer peripheral surface of the first press-contacting roll 11 is formed as a mirror surface, and the outer peripheral surface of the second press-contacting roll 13 is also formed as a mirror surface.

  On the forming surface (outer peripheral surface) 30 of the forming roll 12, as shown in FIGS. 3 and 4, an uneven portion 30 a having a triangular cross section and a flat portion 30 b having a flat surface are formed. In the present embodiment, the flat portion 30 b is formed over the entire circumference of one edge portion of the forming surface 30 of the forming roll 12. In addition, the uneven portion 30 a is formed in the entire area of the forming surface 30 of the forming roll 12 except for the flat portion 30 b. The concavo-convex shape portion 30a contacts the surface of the resin sheet 1 extruded from the extruder 10 to form a concavo-convex shape surface 2a having a triangular cross section on the contacted surface, and the flat portion 30b is formed by extrusion. The surface of the resin sheet 1 extruded from the machine 10 is contacted, and a flat surface 2b is formed on the contacted surface.

  A laser cutting device 14 is arranged at a further forward position of the three rolls 11, 12, 13 in the forward direction of the extruder 10 (see FIG. 1). This laser cutting device 14 is a boundary position between the uneven surface 2a and the flat surface 2b in the optical sheet 2 after being extruded from the extruder 10 and subjected to molding by the molding roll 12, that is, a position indicated by L in FIG. Are arranged so that the laser beam 15 can be irradiated.

  The optical sheet 2 and the optical member (product) 3 are manufactured as follows using the manufacturing apparatus.

[Extrusion process]
A thermoplastic resin is extruded from the extruder 10 to obtain a resin sheet 1 (see FIG. 1). The thermoplastic resin is not particularly limited, and examples thereof include styrene resin, propylene resin, acrylic resin, polycarbonate, and cyclic polyolefin.

[Surface forming process]
Next, as shown in FIGS. 1 and 2, the resin sheet 1 is inserted between the forming roll 12 and the first press-contacting roll 11 disposed at the front position in the extrusion direction of the extruder 10, and subsequently By inserting the resin sheet 1 between the molding roll 12 and the second press-contacting roll 13 disposed below the molding roll 12, the molding roll 12 is pressed against one surface of the resin sheet 1. At this time, since the forming surface 30 of the forming roll 12 is provided with the flat portion 30b and the concavo-convex shape portion 30a having a triangular cross section, the flat surface 2b and the concavo-convex shape surface 2a having a triangular cross section are formed on the surface. The formed optical sheet 2 is obtained (see FIG. 5). That is, the optical sheet 2 is obtained in which the flat surface 2b is formed on one edge and the uneven portion 30a is formed in a region excluding the flat surface 2b of the edge (see FIG. 5).

[Cut process]
At least a part of the flat surface 2b of the optical sheet 2 obtained through the surface molding step is cut out. For example, the laser beam 15 from the laser cutting device 14 is applied to the position indicated by L in FIG. 2 (the boundary position between the uneven surface 2a and the flat surface 2b) in the optical sheet 2 obtained through the surface molding step. By doing so, the flat surface portion 2b in the optical sheet 2 is cut out to obtain the cut piece 4, and the optical member (product) 3 having the uneven surface 2a on the surface is obtained (see FIGS. 1 and 2). In addition, you may make it cut off at the position of an edge side (outside) further from the boundary position of uneven | corrugated shaped surface 2a and flat surface 2b, or may be cut inward from the boundary position of uneven | corrugated shaped surface 2a and flat surface 2b. You may make it cut off at a position (position from a center). Further, the cutting means is not particularly limited to the laser cutting apparatus, and any means can be used as long as it can cut.

[Measurement process]
The optical characteristics of the cut flat surface portion 2b, that is, the cut piece (measurement test piece) 4 are measured. As the optical characteristics, it is preferable to select one or two optical characteristics selected from the group consisting of total light transmittance (Tt) and haze (Hz). In this case, the constituent material of the optical sheet 2 itself The light diffusion effect can be evaluated with higher accuracy. The total light transmittance (Tt) is a value measured according to JIS K7361-1997. The haze (Hz) is a value measured in accordance with JIS K7136-2000.

[Feedback adjustment process]
Manufacturing conditions are adjusted based on the measured values of the optical characteristics obtained in the measurement step. Hereinafter, the feedback adjustment process will be described with two specific examples, but is not particularly limited to such a configuration.

(First embodiment)
This first embodiment is a masterbatch comprising at least one resin selected from the group consisting of a styrene resin, an acrylic resin, a polycarbonate and a cyclic polyolefin as a thermoplastic resin and a light diffusing agent in the extrusion step. An example of application in the case of using a mixture containing a resin and a base resin made of the same resin as that constituting the masterbatch resin is obtained in the feedback adjustment step and obtained in the measurement step. Based on the measured optical properties (for example, total light transmittance or / and haze), the mixing ratio of the master batch resin and the base resin in the extruder 10 is adjusted. For example, when the total light transmittance is smaller than a predetermined value or / and when the haze is larger than a predetermined value, the mixing ratio of the master batch resin is reduced to perform feedback adjustment.

(Second embodiment)
This second embodiment shows an application example in the case of using a propylene resin as a thermoplastic resin in the extrusion step, and in the feedback adjustment step, optical characteristics (for example, total light transmittance) obtained in the measurement step. 1 or 2 or more production conditions selected from the group consisting of the extrusion port temperature of the die of the extruder, the temperature of the forming roll, and the line speed of the extrusion (related to the cooling rate). Manufacturing conditions). The production conditions are factors that affect the degree of microcrystallization of the propylene resin. For example, when the total light transmittance is smaller than a predetermined value or / and when the haze is larger than a predetermined value, the extrusion port temperature of the extruder die is increased, the molding roll temperature is decreased, and the extrusion line speed is increased. The feedback adjustment is performed by adjusting at least one of the manufacturing conditions.

  By performing such a feedback adjustment process, it is possible to manufacture the high-quality optical sheet 2 and the optical member 3 that are quality-controlled with high accuracy.

  In the present invention, the styrene resin contains 50% by mass or more, preferably 70% by mass or more of styrene units as a structural unit, and a part of the styrene resin is styrene as long as it contains 50% by mass or more of styrene units. A copolymer substituted with a copolymerizable monofunctional unsaturated monomer unit may also be used.

  Examples of the copolymerizable monofunctional unsaturated monomer include, for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid 2 -Methacrylic acid esters such as hydroxyethyl; acrylic acid such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate Esters; unsaturated acids such as methacrylic acid and acrylic acid; α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. Moreover, this copolymer may further contain a glutaric anhydride unit and a glutarimide unit. Furthermore, what blended diene rubber, acrylic rubber, etc. as a rubber-like polymer to the above-mentioned polymer and copolymer may be used.

  The propylene resin may be a homopolypropylene obtained by polymerizing propylene alone, or may be a copolymer of propylene and a copolymerizable component that can be copolymerized therewith. Among these, the propylene resin is preferably a polymer containing 50% by mass or more of propylene units. Furthermore, the content of the propylene unit in the propylene resin is particularly preferably 98% by mass or more in that sufficient rigidity is obtained. The copolymer component is not particularly limited, and examples thereof include α-olefins such as ethylene and 1-butene.

  As the light diffusing agent, particles (including powder) that are incompatible with the resin, have a refractive index different from that of the resin, and have a function of diffusing transmitted light that passes through the light diffusing plate may be used. It is not limited. For example, the particles may be inorganic particles such as glass particles, glass fibers, silica particles, aluminum hydroxide particles, calcium carbonate particles, barium sulfate particles, titanium oxide particles, talc, styrene polymer particles, acrylic polymers. Organic particles such as particles and siloxane polymer particles may be used.

  In this invention, it is preferable that the width (M) of the flat portion 30b on the molding surface 30 of the molding die (molding roll or the like) 12 is in the range of 5 to 500 mm. Since the width (M) of the flat surface portion for measuring the optical characteristics can be sufficiently ensured by being 5 mm or more, the measurement of the optical characteristics becomes easy. Moreover, the width | variety of the product part of the optical sheet 2 can fully be ensured because it is 500 mm or less. Especially, it is preferable that the width | variety (M) of the flat part 30b in the said molding surface 30 is the range of 20-500 mm.

  The flat portion 30b of the molding surface 30 of the molding die (molding roll or the like) 12 preferably has a surface roughness Ra of 0.3 μm or less and a ten-point average roughness Rz of 1.0 μm or less. In the case where the flat portion 30b has flatness that satisfies such conditions, when evaluating the light diffusion effect of the constituent material itself of the optical sheet, the influence of light diffusion due to the uneven shape of the surface of the optical sheet is affected. Since it can be sufficiently eliminated, the quality control of the light diffusion effect of the constituent material itself of the optical sheet can be performed with higher accuracy.

  The cross-sectional shape of the concavo-convex shape portion 30a of the molding die (molding roll or the like) 12 is not particularly limited, but for example, a triangular shape, a semicircular shape, a semi-elliptical shape, a trapezoidal shape, a rectangular shape, and other concavo-convex shapes Examples include shape.

When the concave / convex depth of the concave / convex shape portion 30a of the molding surface 30 of the molding die (molding roll, etc.) 12 is “D” and the pitch interval of the concave / convex shape portion 30a is “W” (see FIG. 4), In the case of a configuration in which the formula (1) and the following formula (2) hold,
D / W ≧ 0.2 Formula (1)
D ≧ 10 μm (2)
The light diffusion performance of the obtained optical sheet is not only the contribution of the light diffusion effect of the constituent material of the optical sheet itself, but also the contribution of the light diffusion effect due to the uneven shape of the surface of the optical sheet (to a degree that cannot be ignored) Therefore, when performing the quality control of the light diffusion effect of the constituent material itself of the optical sheet, the technical significance of applying the manufacturing method of the present invention is particularly great. In particular, when the configuration satisfies D / W ≧ 0.5 and D ≧ 10 μm, the technical significance of applying the manufacturing method of the present invention is even greater.

In addition, when at least one of the following configurations c), d) and e) is adopted, the light diffusion performance of the obtained optical sheet is based on the light diffusion effect due to the uneven shape on the surface of the optical sheet. Not only the contribution, but also the contribution of the light diffusion effect of the optical sheet component itself (to a degree that cannot be ignored) is large, so when performing quality control of the light diffusion effect due to the uneven shape of the surface of the optical sheet, In particular, the technical significance of applying the manufacturing method of the present invention is extremely great.
c) The internal haze of the optical sheet is 3% or more. d) The optical sheet has an internal haze, and the internal haze is expressed by the optical sheet containing a light diffusing agent. e) The optical sheet is It has an internal haze, and the internal haze is expressed by microcrystallization of the resin constituting the optical sheet.

  The thickness T of the optical sheet 2 is preferably set in the range of 0.01 to 5 mm, but is not particularly limited to such thickness.

  In the above embodiment, the flat portion 30b is formed at the edge of the molding surface 30 of the mold 12, but the arrangement position of the flat portion 30b is not particularly limited to such a position (edge). Absent. For example, you may employ | adopt the structure by which the flat part 30b was provided in the center part of the width direction of the molding surface 30 of the said forming roll 12 over the perimeter. In this case, in the cutting step, if both sides in the width direction of the flat surface at the center position of the optical sheet (that is, the boundary position between the left and right uneven surfaces) are cut by irradiating laser light, the optical Two members 3 on the left and right sides can be taken.

  Another example of the manufacturing apparatus used in the manufacturing method of the present invention is shown in FIG. Reference numeral 10 denotes an extruder. Three press-contact rolls (mirror rolls) 17, 17 and 17 are arranged at the extrusion front position of the extruder, and the forming roll 12 (see FIGS. 3 and 4) is arranged downstream of these. In other words, the forming roll 12 and the press-contact roll 18 having a mirror surface on the outer peripheral surface are arranged in a pair on the downstream side of the triple press-contact roll (see FIG. 6). The laser cutting device 14 is disposed on the downstream side of the forming roll 12. You may implement the manufacturing method of this invention using the manufacturing apparatus of such a structure.

  The manufacturing method of the optical sheet according to the present invention is not particularly limited to that of the above-described embodiment, and any design change can be allowed as long as it does not depart from the spirit of the present invention as long as it is within the scope of the claims. It is.

  The optical sheet manufactured by the manufacturing method of the present invention is suitably used as an optical member such as a prism sheet, a light diffusing plate, a light deflecting structure plate, and a light guide plate, but is not particularly limited to such applications. Absent. Among them, it is particularly suitable as an optical member for an image display device such as a liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 ... Resin sheet 2 ... Optical sheet 2a ... Uneven shape surface 2b ... Flat surface 10 ... Extruder 12 ... Molding roll (molding die)
DESCRIPTION OF SYMBOLS 14 ... Laser cutting device 15 ... Laser beam 30 ... Molding surface 30a ... Uneven shape part 30b ... Flat part D ... Uneven depth of uneven part W ... Pitch interval M of uneven shape part ... Flat part width

Claims (18)

  Including a surface molding step of obtaining an optical sheet having a concavo-convex shape surface and a flat surface formed on the surface by molding a synthetic resin using a mold having a concavo-convex shape portion and a flat portion on the molding surface. A method for producing an optical sheet having an uneven shape on a characteristic surface. An extrusion process of extruding a thermoplastic resin from an extruder to obtain a resin sheet;
A surface molding step of obtaining an optical sheet having a concavo-convex shape surface and a flat surface formed on a surface thereof by pressing a forming roll having a concavo-convex shape portion and a flat portion on a molding surface against at least one surface of the resin sheet. The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface characterized by including.   The manufacturing method of the optical sheet which has the uneven | corrugated shape on the surface of Claim 1 or 2 with which the said flat part is provided in at least one part of the edge part of the said molding surface.   The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of Claim 2 with which the said flat part is provided over the perimeter of the at least one edge part of the molding surface of the said forming roll.   The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of any one of Claims 1-4 whose width | variety of the flat part of the said molding surface is 5-500 mm.   The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of any one of Claims 1-4 whose width | variety of the flat part of the said molding surface is 20-500 mm.   The flat portion of the molding surface has a surface roughness Ra of 0.3 μm or less and an Rz of 1.0 μm or less. The optical sheet having an uneven shape on the surface according to claim 1. Production method. The following formula (1) and the following formula (2) are satisfied when the concave / convex depth of the concave / convex shape portion of the molding surface is “D” and the pitch interval of the concave / convex shape portion is “W”. The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of any one of Claims 1-7 to do.
D / W ≧ 0.2 Formula (1)
D ≧ 10 μm (2)   The method for producing an optical sheet having an uneven shape on a surface according to any one of claims 1 to 8, wherein an internal haze of the optical sheet is 3% or more.   The surface of any one of claims 1 to 9, wherein the optical sheet has an internal haze, and the internal haze is expressed by the optical sheet containing a light diffusing agent. The manufacturing method of the optical sheet which has.   The surface of any one of claims 1 to 10, wherein the optical sheet has an internal haze, and the internal haze is expressed by microcrystallization of a resin constituting the optical sheet. The manufacturing method of the optical sheet which has. After the surface molding step, comprising a step of cutting at least a part of the flat surface in the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
It has the feedback adjustment process which adjusts manufacturing conditions based on the measured value of the optical characteristic obtained by the said measurement process, The optical which has uneven | corrugated shape on the surface of any one of Claims 1-11 characterized by the above-mentioned. Sheet manufacturing method. In the extrusion step, as the thermoplastic resin, a master batch resin containing at least one resin selected from the group consisting of styrene resin, acrylic resin, polycarbonate and cyclic polyolefin and a light diffusing agent, and the master batch resin Using a mixture containing a base resin made of the same resin as the resin constituting
After the surface molding step, comprising a step of cutting at least a part of the flat surface in the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
12. The method according to claim 2, further comprising a feedback adjustment step of adjusting a mixing ratio of the master batch resin and the base resin in the extruder based on the measured value of the optical property obtained in the measurement step. The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of any one. In the extrusion process, using a propylene resin as a thermoplastic resin,
After the surface molding step, comprising a step of cutting at least a part of the flat surface in the optical sheet,
Comprising a measuring step of measuring the optical characteristics of the cut flat surface portion,
Based on the measured value of the optical property obtained in the measurement step, one or more production conditions selected from the group consisting of the extrusion port temperature of the die of the extruder, the temperature of the molding roll, and the extrusion speed are adjusted. It has a feedback adjustment process, The manufacturing method of the optical sheet which has an uneven | corrugated shape on the surface of any one of Claims 2-11 characterized by the above-mentioned.   The method for producing an optical sheet having a concavo-convex shape on the surface according to any one of claims 12 to 14, wherein the optical property measured in the measurement step is total light transmittance or / and haze.   The method for producing an optical sheet having a concavo-convex shape on a surface according to any one of claims 12 to 15, wherein in the cutting step, at least a part of a flat surface of the optical sheet is cut by laser light irradiation.   A molding roll for producing an optical sheet having a concavo-convex shape on a surface, wherein a concavo-convex shape portion and a flat portion are provided on a molding surface on the outer periphery of the molding roll.   The forming roll for manufacturing an optical sheet having a concavo-convex shape on the surface according to claim 17, wherein the flat portion is provided over the entire circumference of at least one edge of the forming surface.

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