JP6090384B2 - Optical sheet and image display device - Google Patents

Description

  The present invention relates to an optical sheet having a fine concavo-convex shape on the surface, and an image display device provided with the optical sheet.

  In an image display device that emits an image to an observer, such as a plasma television or a liquid crystal display device, an image light source and an optical sheet having various functions for improving the quality of image light from the image light source and transmitting the image light to the observer And are provided.

  Such an optical sheet is usually configured by laminating a plurality of layers. In addition, as one of the layers, a layer having a fine uneven shape on the surface may be provided. In order to manufacture a sheet having fine irregularities on such a surface, a roll mold having grooves and protrusions that can transfer a shape corresponding to the irregularities is usually used.

  Patent Document 1 discloses a method for manufacturing a roll mold applied to an optical sheet. Here, a technique relating to a bite shape for manufacturing a mold for manufacturing an optical sheet capable of suppressing the occurrence of point defects and linear defects is described.

JP 2003-21457 A

  The grooves and protrusions formed on the surface of the roll mold need not be formed on the roll mold, but a very large number of grooves and protrusions must be formed on the roll mold. From the viewpoint of ensuring the quality of the optical sheet that is transferred from the roll mold and manufactured, it has been considered that the infinite number of grooves and protrusions need to be as uniform as possible in any part on the roll mold.

  However, in the process of forming grooves and protrusions on the surface of a roll mold for manufacturing an optical sheet, the cutting tool is worn out by wear, and the protrusions gradually fall down as cutting continues with the cutting tool. A bending phenomenon occurred. As a result, there is a problem that the shape of the groove and the protrusion is different between the part where the cutting is started and the part where the cutting is finished. Moreover, if an optical sheet is manufactured with such a roll mold, the shape of the groove and the protrusion of the roll mold is transferred to the optical sheet, which may affect the optical performance of the optical sheet.

  Therefore, the present invention provides an optical sheet in which the protrusions produced as described above are less likely to be tilted, and an image display device including the optical sheet.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

The invention described in claim 1 has an optical functional layer (12) having a light transmission part (13) formed so as to be able to transmit light and a light absorption part (14) formed so as to be able to absorb light. and, an optical sheet (10) disposed on the viewer's side of the image light source, the light transmitting portion comprises a trapezoidal cross-section, parallel rows along the sheet surface at equal intervals in a short upper base side of trapezoid cross-section In addition, the light absorbing portion is formed between the light transmitting portions, and the light transmitting portions are inclined toward the adjacent light absorbing portions at both ends in the parallel direction of the light transmitting portions, and one side of the light transmitting portions in the parallel direction. The optical sheet is characterized in that the direction in which the light transmission portion is inclined is opposite between the end portion of the first and the other end portion.

  According to a second aspect of the present invention, in the optical sheet (10) according to the first aspect, the light transmission part is inclined toward the outside of the optical sheet at both ends in the parallel direction of the light transmission part (13). It is characterized by.

  According to a third aspect of the present invention, in the optical sheet (10) according to the first or second aspect, the optical sheet (10) further includes a layer capable of adjusting a color tone of light emitted from the image light source, and the optical functional layer (12) is the most observable. It arrange | positions at the side used as a person side, It is characterized by the above-mentioned.

The invention according to claim 4 is an image display device (100) comprising an image light source and an optical sheet (10) disposed on the viewer side of the image light source, wherein the optical sheet can transmit light. The optical function layer (12) having a light transmission part (13) formed in the light absorption part and a light absorption part (14) formed so as to be able to absorb light, the light transmission part having a trapezoidal cross section, while being parallel along the sheet surface at equal intervals in a short upper base side of the trapezoidal cross-section, the light absorbing portion is formed between the light transmitting portion, one end of the parallel direction of the light transmitting portion and the other The image display device is characterized in that the light transmission portion is inclined in the opposite direction from the end portion.

  According to the present invention, it is possible to provide an optical sheet in which the protrusions generated as described above are less likely to be tilted, and an image display device including the optical sheet.

2 is a perspective view schematically showing the appearance of a roll mold 20. FIG. 3 is an enlarged view of a part of a roll mold 20. FIG. It is the figure which expanded and showed a part of roll metal mold | die 20 further. 3 is a diagram schematically showing the shape of a cutting tool 30. FIG. It is a figure explaining the usage example of the cutting tool. FIG. 4 is a diagram illustrating a part of a process of a method for manufacturing a roll mold 20. 2 is a diagram schematically showing a part of a cross section of an optical sheet 10. FIG. It is the figure which expanded a part of optical function layer 12. FIG. 3 is a diagram illustrating a part of a process of a method for manufacturing an optical sheet 10. FIG. 1 is an exploded perspective view schematically showing a video display device 100. FIG. It is the figure which showed the evaluation result of the optical sheet concerning an Example and a comparative example.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments. Each drawing is simplified by changing the scale and the like as appropriate for convenience of illustration and understanding. Moreover, in each drawing, the same code | symbol is attached | subjected to the thing of the same structure, and the code | symbol which becomes repeated may be abbreviate | omitted partially.

1. Mold FIG. 1 is a perspective view schematically showing the appearance of a roll mold 20. 2 shows a part of the cross-section of the annular protrusion 22 and the groove 23 formed on the outer peripheral surface of the roll mold 20 shown in FIG. 1 (both ends and the center in the direction parallel to the rotation axis of the roll mold 20). It is the figure which expanded and showed. FIG. 3 is an enlarged view of a part of the cross-section of the annular protrusion 22 and the groove 23 formed on the outer peripheral surface of the roll mold 20 (the center part of the roll mold 20). The cross section shown in FIGS. 2 and 3 is a cross section orthogonal to the direction in which the annular protrusion 22 and the groove 23 extend, and is a cross section in the direction along the rotation axis of the roll mold 20. Further, in FIGS. 1 to 3, the cutting tool feed direction is from the right side to the left side of the drawing. Accordingly, in FIGS. 1 to 3, the right side of the drawing is the rear side in the feeding direction, that is, the side where cutting is started, and the left side of the drawing is the front side in the feeding direction, that is, the side where cutting is finished.

  The roll mold 20 has alternately the grooves 23 and the annular protrusions 22 for molding the concavo-convex portions of the optical sheet having the concavo-convex shape in a direction parallel to the rotation axis. In other words, as shown in FIG. 1, the roll mold 20 is a so-called roll-shaped mold having a columnar shape, and a plurality of annular protrusions 22 projecting from the outer peripheral surface of the columnar roll base 21, and the annular protrusions 22. It has a groove 23 formed between them. Here, the annular protrusion 22 and the groove 23 are very fine themselves, and extend in the circumferential direction of the roll mold 20 and are arranged over the entire length in the width direction (roll rotation axis direction) of the roll mold 20. It is densely formed. Further details are as follows.

  The annular protrusion 22 and the groove 23 have a shape corresponding to a light transmitting portion 13 and a concave portion 13a (see FIG. 8) of the optical function layer 12 described later. That is, the annular protrusion 22 has the shape of the concave portion 13 a and the groove 23 has the shape of the light transmitting portion 13. Accordingly, A to D shown in FIG. 3 have dimensions corresponding to A 'to D' in FIG. However, considering that there is expansion and contraction when molding the material constituting the light transmission part, A to D in FIG. 3 are not necessarily the same dimensions as A ′ to D ′ in FIG. 8. It goes without saying that there is nothing.

  Further, as shown in FIG. 2, in the roll mold 20, the annular protrusions 22 are inclined toward the adjacent groove 23 at both ends in the direction parallel to the rotation axis (left and right direction in FIG. 2). The direction in which the annular protrusion 22 is inclined is opposite between one end and the other end in the direction parallel to the 20 rotation axis. More specifically, the annular protrusions 22 are inclined inward in the direction parallel to the rotation axis of the roll mold 20 at both ends in the direction parallel to the rotation axis of the roll mold 20. Further, in the vicinity of the center of the roll mold 20, the annular protrusion 22 is not inclined or is small. In the conventional roll mold, the inclination of the annular protrusion gradually increases as it goes from the part where the cutting is started to the part where the cutting is finished. Compared with such a conventional roll mold, the roll mold 20 is less inclined to the annular protrusion 22 as a whole. A method for manufacturing such a roll mold 20 will be described later.

A roll base 21 provided in the roll mold 20 has a base serving as a base and a layer to be processed laminated on the outer surface of the base.
The base is a part for securing the rigidity of the roll base 21 and occupies most of the roll base 21. From this point of view, the base is preferably made of an iron-based material for mechanical structure. Further, from the viewpoint of reducing the weight while ensuring the necessary rigidity, the base may have a bottomed cylindrical shape having bottoms at both ends. In addition, the roll mold 20 generally has a double structure so that cold water, hot water, steam or high-temperature oil can be circulated inside the roll base 21 so that the surface temperature can be adjusted.
On the other hand, the layer to be processed is a layer laminated so as to cover the outer surface of the substrate. Since the material of the substrate is selected from the viewpoint of structure as described above, it is often difficult to process. Therefore, since it is only necessary to actually process the vicinity of the surface of the roll base 21, a layer to be processed that is relatively easy to process is provided in the processed portion. Therefore, the layer to be processed is preferably a plating layer made of a material that can be easily processed, such as a copper plating layer or a nickel plating layer. The thickness of the layer to be processed is determined by the shape to be processed due to its nature. For example, the thickness of the copper plating layer is not a problem as long as it is equal to or higher than the required shape, but is usually 0.3 mm to 1.0 mm.

  Next, a method for manufacturing the roll mold 20 will be described. First, after describing a conventional method for producing a mold roll, a method for producing the roll mold 20 will be described in contrast to the production method.

  When forming grooves and annular protrusions on the surface of the roll mold, the annular protrusions adjacent to the feed direction rear side of the grooves cut by the cutting tool are already formed on the groove side (feed direction rear side). ). When the annular protrusion is pushed in this way, the annular protrusion is inclined to bend. In the conventional roll mold manufacturing method, the left and right target grooves in the cross section in the direction along the rotation axis are to be formed from the portion where the cutting is started. When such a cutting tool is used, since the annular protrusion is difficult to tilt at the site where cutting is started, a right and left target groove (a groove having a desired shape) can be formed in a cross section in the direction along the rotation axis. However, as the cutting progresses, the cutting performance of the cutting tool deteriorates, so that the shape is as intended at the site where the cutting is started, but the cutting tool pushes the annular protrusion as described above toward the site where the cutting is finished. The force becomes strong, and the annular protrusion is easily inclined backward in the feeding direction. The amount of inclination of the annular protrusion increases as it goes to the part where the cutting is finished. Therefore, in the conventional roll mold, there is a large difference in the amount of inclination of the annular protrusion between the portion where the cutting is started and the portion where the cutting is finished.

  On the other hand, according to the method for manufacturing the roll mold 20, the annular protrusion 22 is intentionally formed on the side opposite to the direction in which the annular protrusion 22 is assumed to be inclined at the portion where the cutting is to be finished. The formation of the groove 23 is started so as to fall down. That is, according to the method for manufacturing the roll mold 20, the groove 23 is formed by using a cutting tool in which the annular protrusion 22 is formed to be inclined forward in the feed direction at a site where cutting is started. More specifically, when the groove 23 is formed using a cutting tool, the angle of inclination of the lateral flank on the front side in the feed direction with respect to the rotational axis of the mold roll 20 is greater than the side flank on the rear side in the feed direction. Use a cutting tool in such a way as to reduce. Hereinafter, the manufacturing method of the mold roll 20 will be described more specifically.

  First, the roll base | substrate 21 with which the to-be-processed layer was laminated | stacked on the base | substrate is prepared, and this is rotated with a roll rotating shaft. First, as a pre-processing for obtaining a reference surface, mirror processing is performed by a predetermined cutting tool (R bite) with a necessary cutting depth and feed. The R bit is a bit having an arcuate tip, and a diamond bit having a radius of curvature of 2 mm to 10 mm is often used. The feed pitch is generally 0.1 mm to 0.4 mm. Here, the diameter of the roll base 21 is not particularly limited, but is preferably 300 mm or more and 500 mm or less.

  Thereafter, the groove 23 is formed by a cutting tool while rotating the roll base 21 based on the obtained reference surface. Here, the cutting tool has, for example, the following shape. A schematic view of a cutting tip 30 as an example of the cutting tool used in FIG. 4 is shown. In FIG. 4, the rake face is indicated by reference numeral 31, the front flank face is indicated by reference numeral 32, and the lateral flank faces are indicated by reference numerals 33a and 33b. The lateral clearance surface 33a is a lateral clearance surface on the rear side in the feeding direction, and the lateral clearance surface 33b is a lateral clearance surface on the front side in the feeding direction. 4A is a perspective view, FIG. 4B is a view from the rake face 31 side, FIG. 4C is a view from the front flank face 32 side, and FIG. It is the figure seen from the side.

  The bite angles θa1 and θa2, the side clearance angle θb, and the front clearance angle θc shown in FIG. 4 are as follows.

  In the cutting tip 30, the cutting tool angle θa2 is larger than the cutting tool angle θa1. Therefore, the side flank 33b which is the front side in the feed direction with respect to the rotation axis of the mold roll 20 is obtained by applying the cutting tip 30 to the roll mold 20 so that the front flank 32 is parallel to the rotation axis of the roll mold 20. The inclination angle θ2 (see FIG. 6A) is smaller than the inclination angle θ1 (see FIG. 6A) of the lateral relief surface 33a on the rear side in the feed direction with respect to the rotation axis of the mold roll 20. Thus, the cutting tip 30 can be used.

  As described above, the annular protrusion formed on the roll die is likely to be inclined rearward in the feed direction (the side where the cutting is started) as the cutting tool for cutting the groove wears. Here, as described above, the cutting tip 30 is configured such that the side flank 33b on the front side in the feed direction has a smaller inclination angle with respect to the rotation axis of the mold roll 20 than the side flank 33a on the rear side in the feed direction. By using this, the annular protrusion 22 is inclined and formed forward in the feed direction. For this reason, the annular protrusion 22 is easily formed to be inclined forward in the feed direction due to the difference between the cutting tool angle θa1 and the cutting tool angle θa2, and the cutting tip 30 is worn and deteriorated in sharpness. Due to the synergy with the effect that the protrusion 22 is easily inclined backward in the feeding direction, the inclination of the annular protrusion 22 disappears or becomes smaller in the central portion of the roll mold 20, and the inclination of the annular protrusion 22 at the portion where the cutting is finished is Smaller than conventional roll molds. According to such a manufacturing method of the roll mold 20, the inclination of the annular protrusion 22 is generated even at the portion where the cutting is started, but when viewed from the entire roll mold 20, the inclination of the annular protrusion 22 is the conventional roll mold. Smaller.

  In addition, as described above, the method of using the cutting tip so that the lateral flank on the front side in the feed direction has a smaller inclination angle with respect to the rotation axis of the roll mold than the side flank on the rear side in the feed direction, It is not limited to the method using the cutting tip in which the cutting tool angle θa1 and the cutting tool angle θa2 are different. FIG. 5 is a diagram illustrating an example of use of the cutting tip 130. FIG. 5A and FIG. 5B are views of the cutting tip 130 as viewed from the rake face side. For example, as shown in FIG. 5A, even if the cutting tool angle 130 is the same as the cutting tool angle θa3 and the cutting tool angle θa4, as shown in FIG. By inclining, the lateral flank 133b on the front side in the feed direction can be used such that the tilt angle with respect to the rotation axis of the roll mold is smaller than the lateral flank 133a on the rear side in the feed direction.

Returning to FIG. 4, the explanation of the lateral clearance angle θb and the like will be continued. The lateral clearance angle θb is preferably 2 degrees or more and 5 degrees or less. By setting the side clearance angle θb to 2 degrees or more, the cutting performance of the cutting tip 30 is improved and the burden on the cutting tip is reduced, so that wear can be reduced and processing can be performed with a single cutting tip with high accuracy. be able to. That is, it is possible to increase the number of cuttings by increasing the depth of the groove 23 or decreasing the pitch. Therefore, the roll die of the optical sheet can be manufactured without replacing the cutting tip or suppressing the number of replacements. That is, it is possible to improve the manufacturing efficiency and accuracy of the roll mold 20 and to manufacture the uneven shape of the optical sheet 10 that is the final product with high accuracy. Further, if the lateral clearance angle θb is larger than 5 degrees, it is necessary to increase the front clearance angle, and there is a concern that the strength of the cutting tip 30 is lowered.
The front clearance angle θc is usually 5 degrees or more and 20 degrees or less in many cases. If the angle is less than 5 degrees, the cutting performance tends to be deteriorated as with the side clearance angle. On the other hand, if it is greater than 20 degrees, the cutting tip tip is not rigid enough to cause chipping or chipping.

  In addition, w of FIG.4 (b) is a byte | tip tip width. The tool tip width w is appropriately changed depending on the shape of the groove to be formed.

  The material of the cutting tip can be appropriately selected depending on the material of the layer to be processed, the processing shape, and the like. Examples thereof include cemented carbide, CBN (cubic boron nitride), diamond and the like. Among these, diamond is preferable from the viewpoint of obtaining high accuracy. There are natural and synthetic diamonds, but there is no particular limitation.

  The rotational speed of the roll base 21 at the time of cutting is not particularly limited, but is preferably 300 rpm or more and 600 rpm or less. Although depending on the diameter of the roll base 21, for example, when the diameter is 400 mm, if it is less than 300 rpm, the cutting speed is slow, so that the burden on the cutting tip becomes large and it may not be possible to process with high accuracy. 600 rpm is approximately the maximum turning speed of the lathe. As the rotational speed of the roll base 21 is increased, the roll base tends to be shaken. From this viewpoint, about 400 rpm is preferable.

  Using the cutting tip 30 described above, the grooves 23 and the annular protrusions 22 can be formed as follows. A schematic diagram is shown in FIG. Cutting is performed in the order of FIG. 6A, FIG. 6B, and FIG. 6C.

  As shown in FIG. 6A, so-called cutting is performed by the cutting tip 30 from the outer peripheral surface of the roll base 21 toward the rotation axis of the rotation axis of the roll base 21. At this time, it is preferable that the cutting direction is an oblique direction that goes in the feed direction (left direction in the drawing) while moving in the direction of the rotation axis of the roll base 21. More specifically, as indicated by VI in FIG. 6A, the cutting tip 30 has the same angle as the cutting tool angle θa1 that is opposite to the feed direction (rightward in the drawing) during cutting. While feeding, it cuts in the direction of the rotation axis of the rotation axis. Then, as shown in FIG. 6B, one groove 23 is formed.

  By making an oblique cut in this way, the force from the cutting tip 30 that tries to tilt the annular protrusion 22 being formed in the direction indicated by E in FIG. It is possible to suppress falling down so as to bend in the direction of. In particular, as the cutting progresses, the cutting force of the cutting tip 30 decreases, and the force to be applied to the annular protrusion 22 tends to increase. On the other hand, by performing the incision as described above, it is possible to suppress the force to try to fall over the entire region from the start portion to the end portion of the cutting. , Shape stability can be improved.

Next, the cutting tip 30 is retracted from the groove 23 in the radial direction of the roll base 21 from the state shown in FIG. And it feeds by the half pitch of the pitch of the groove | channel 23, and cuts in the radial direction of the roll base | substrate 21 to the outer peripheral part position of the cyclic | annular protrusion 22 as shown in FIG.6 (b). Thereby, the outer peripheral part of the annular protrusion 22 is formed.
After that, the cutting tip 30 is retracted in the radial direction of the roll base 21, and the cutting tip 30 is sent to cut the next groove 23. The cutting tip 30 is cut in the same manner as described with reference to FIG. The next groove 23 is formed as shown in c).

  Here, the cutting speed is preferably 2 (μm / rotation) or more and 5 (μm / rotation) or less. Further, when the cutting tip (cutting tool) reaches the cutting depth, it is preferable that the cutting tip 30 is retracted after the roll base 21 is rotated one or more times in the same posture. Thereby, it becomes the predetermined cutting depth over the circumference direction circumference of the roll base 21. If the cutting tip 30 is retracted in less than one rotation, there may be a portion that does not reach the predetermined cutting depth partially in the circumferential direction, and the appearance defect and the optical performance may vary.

  As described above, the annular protrusion 22 and the groove 23 can be formed so as to extend in the circumferential direction of the roll base 21 and to be arranged in parallel over the entire length of the roll base 21 in the rotation axis direction (width direction).

  In this manufacturing method, as described above, the side flank 33b on the front side in the feed direction has a smaller inclination angle with respect to the rotation axis of the mold roll 20 than the side flank 33a on the rear side in the feed direction. A chip 30 is used. Therefore, although the inclination of the annular protrusion 22 occurs even at the site where cutting is started, as described above, the inclination of the annular protrusion 22 is smaller than that of the conventional roll mold as viewed in the roll mold 20 as a whole.

  From the viewpoint of preventing the surface of the roll mold from corroding after the annular protrusions 22 and the grooves 23 are formed by the above cutting, or improving the releasability of the light transmitting portion constituting composition described later, The surface of the roll mold is preferably plated with chromium or the like.

2. Optical Sheet FIG. 7 is a diagram schematically showing a layer structure of a part of a cross section in the thickness direction of the optical sheet 10 (both ends and a central portion in the parallel direction of the light transmitting portion 13). The optical sheet 10 is provided on the viewer side with respect to the video light source when placed on the video display device, and can appropriately shield the light (so-called external light) irradiated from the viewer side and improve the contrast. It is a sheet-like member.

  The optical sheet 10 includes a base material layer 11 and an optical functional layer 12 formed on the base material layer 11. The base material layer 11 and the optical function layer 12 will be described below.

  The base material layer 11 is a layer serving as a base material for forming the optical functional layer 12 described in detail later. The base material layer 11 is preferably composed of a material mainly composed of polyethylene terephthalate (PET). When the base material layer 11 has PET as a main component, the base material layer 11 may contain other resins. Various additives may be added as appropriate. Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like. Here, “main component” means that the PET is contained in an amount of 50% by mass or more with respect to the entire material forming the base material layer (hereinafter the same).

However, the main component of the material constituting the base material layer 11 is not necessarily PET, and other materials may be used. Examples thereof include polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, polyester resins such as terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer, and polyamide resins such as nylon 6. , Polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymer, cellulose resins such as triacetyl cellulose, imide resins and polycarbonate resins Etc. Moreover, you may add additives, such as a ultraviolet absorber, a filler, a plasticizer, an antistatic agent, suitably in these resin as needed.
In addition to performance, from the viewpoints of mass productivity, price, availability, etc., it is preferable that the base material layer 11 is composed of a resin mainly composed of PET.

  The optical functional layer 12 is a layer having a function of appropriately absorbing stray light and external light while controlling the optical path of the image light from the image light source side. The optical functional layer 12 has a cross section shown in FIG. 7 and a shape extending to the back / near side of the drawing. That is, in the cross section shown in FIG. 7, the light absorption formed between the light transmitting portion 13 having a substantially trapezoidal cross section and the concave portion 13 a (see FIG. 8) having a substantially trapezoidal cross section. Part 14.

  Further, the optical functional layer 12 is inclined in the direction in which the light transmissive portions 13 are arranged in the parallel direction of the light transmissive portions 13 (left and right direction in FIG. 7). The direction in which the light transmitting portion 13 is inclined is opposite between the one end and the other end. More specifically, the light transmission part 13 is inclined toward the outside of the optical sheet 10 at both ends in the parallel direction of the light transmission part 13. Furthermore, the light transmission part 13 is not inclined near the center of the optical function layer 12. Therefore, as for the optical function layer 12 as a whole, the light transmission portion 13 is less inclined than the conventional one. Such an optical functional layer 12 can be molded using the roll mold 20 described above.

  FIG. 8 shows an enlarged view of one light absorbing portion 14 near the center and the light transmitting portion 13 adjacent thereto in the optical functional layer 12 shown in FIG.

  The light transmitting portion 13 is a portion that transmits light, and in the cross section shown in FIG. 7 and FIG. 8, the surface on the base material layer 11 side has a lower base, and the opposite surface is shorter than the lower base. It is an element with a substantially trapezoidal cross section having an upper base. The light transmitting portions 13 are arranged in parallel at a predetermined interval along the sheet surface, and a recess 13a having a substantially trapezoidal cross section is formed therebetween. The concave portion 13a has a trapezoidal cross section having a lower base on the upper base side of the light transmitting portion 13 and an upper base on the lower base side of the light transmitting portion 13, and is filled with necessary materials described later. The light absorption part 14 is formed.

  The interval at which the light transmitting portions 13 are arranged in parallel (the interval between one light transmitting portion 13 and the light transmitting portion 13 adjacent thereto, the pitch) is not particularly limited, but may be 20 μm or more and 100 μm or less. preferable.

In FIG. 8, each dimension of the recessed part 13a was represented by AD. In FIG. 8, A is the length of the bottom of the recess 13a. Similarly, B is the length of the upper base, C is the height, and D is the angle between the hypotenuse and the sheet normal. Each of the dimensions A to D is designed to have performance required as an optical sheet, and its value is not particularly limited, but A is preferably 5 μm or more and 20 μm or less. Similarly, B is preferably the same as or smaller than A, 2 μm to 20 μm, C is 50 μm to 150 μm, and D is 0 ° to 5 °.
As will be described later, a roll mold corresponding to each dimension required here is manufactured.

  The light transmitting portion 13 has a refractive index of Np and has light transmittance. Such a light transmission part 13 can be formed by hardening the light transmission part structure composition mentioned later, for example. Details will be described later. The value of the refractive index Np is not particularly limited, but is preferably 1.49 to 1.56 from the viewpoint of the availability of the applied material.

  Next, the light absorption unit 14 will be described. The light absorbing portion 14 is formed in the concave portion 13a between the light transmitting portions 13 described above, and is configured to be able to absorb light as a whole. Therefore, the shape is generally along the recess 13a.

  The light absorbing portion 14 is made of a predetermined material having a refractive index Nb that is the same as or smaller than the refractive index Np of the light transmitting portion 13. When the refractive index Np of the light transmission part 13 and the refractive index Nb of the light absorption part 14 are Np> Nb, the difference in refractive index and the light incident on the interface at the interface between the light absorption part 14 and the light transmission part 13 Based on the relationship with the corner, a part of the image light can be appropriately reflected at this interface and emitted to the viewer side. Thereby, in addition to the image light transmitted through the light transmission part 13 without being reflected on the interface, the image light reflected in this way is provided to the observer, and a bright image can be obtained. Further, a part of the external light and stray light is incident on the light absorbing portion 14 without being reflected at the interface and absorbed, thereby improving the image quality. The difference in refractive index between Np and Nb is not particularly limited, but is preferably 0 or more and 0.07 or less. The greater the difference in refractive index, the easier it is to reflect at the interface.

  In the present embodiment, the light absorbing portion 14 has light absorbing performance by containing the light absorbing particles 16. That is, the concave portion 13a is filled with a binder (light absorbing portion constituting composition) in which the light absorbing particles 16 are dispersed. Therefore, in this case, the binder is a substance having a refractive index Nb. The material and method for forming the light absorbing portion 14 will be described in detail later.

  The means for absorbing light is not limited to the method using light absorbing particles as in this embodiment. In addition, for example, the entire light absorbing portion can be colored with a pigment or a dye.

  According to such an optical sheet 10, it is possible to appropriately shield outside light. FIG. 7 schematically shows an example of an optical path of external light incident on the optical sheet 10. In this description, the viewer side is on the paper surface of FIG. That is, as shown in FIG. 7, the external light L <b> 1 incident on the optical sheet 10 at a predetermined angle is absorbed by the light absorbing unit 14 while being transmitted through the optical sheet 10. Thereby, contrast can be improved. Further, the image light L2 incident on the optical sheet 10 at a predetermined angle is reflected at the interface between the light transmission part 13 and the light absorption part 14 and is emitted to the observer side. Such optical performance of the optical sheet 10 is affected by the inclination of the interface between the light transmission part 13 and the light absorption part 14 with respect to the sheet surface, that is, the inclination of the light transmission part 13. According to the optical sheet 10, as described above, the light transmission part 13 is inclined toward the adjacent light absorption part 14 at both ends in the parallel direction of the light transmission part 13, and one end part of the light transmission part 13 in the parallel direction. And the other end are inclined in the direction in which the light transmitting portion 14 is inclined. Therefore, when the optical sheet 10 is used for an image display device, the viewing angles can be easily equalized at both end portions (for example, the top and bottom of the screen) of the light transmission portion 13 in the parallel direction.

  Next, a method for manufacturing the optical sheet 10 using the roll mold 20 will be described. FIG. 9 shows a schematic diagram. First, the light transmission part 13 is formed on the substrate 11. That is, as can be seen from FIG. 9, the base material 11 ′ to be the base material layer 11 is inserted between the roll mold 20 and the nip roll 41 disposed so as to face the roll mold 20. At this time, the roll mold 20 and the nip roll 41 are rotated as shown by the arrows in FIG. 9 while supplying the light transmitting portion constituting composition 13 ′ between the base material 11 ′ and the roll mold 20. Thereby, the light transmitting portion constituting composition 13 ′ is filled in the groove 23 formed on the surface of the roll die 20, and the light transmitting portion constituting composition 13 ′ is along the surface shape of the roll die 20. Become.

  Here, as the light transmission part constituting composition 13 ′, for example, a photocurable resin composition in which a reactive dilution monomer (M1) and a photopolymerization initiator (S1) are blended with a photocurable prepolymer (P1). Is preferably used.

  Examples of the photocurable prepolymer (P1) include epoxy acrylate-based, urethane acrylate-based, polyether acrylate-based, polyester acrylate-based, and polythiol-based prepolymers.

  Examples of the reactive dilution monomer (M1) include vinyl pyrrolidone, 2-ethylhexyl acrylate, β-hydroxy acrylate, and tetrahydrofurfuryl acrylate.

  Examples of the photopolymerization initiator (S1) include hydroxybenzoyl compounds (2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzoin alkyl ether, etc.), benzoyl Formate compounds (such as methylbenzoylformate), thioxanthone compounds (such as isopropylthioxanthone), benzophenones (such as benzophenone), phosphate compounds (1,3,5-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-) Trimethylbenzoyl) -phenylphosphine oxide and the like, and benzyldimethyl ketal and the like. Among these, the irradiation device for curing the photocurable resin composition and the curability of the photocurable resin composition can be arbitrarily selected. From the viewpoint of preventing coloring of the light transmitting portions 13, 13,..., 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone and bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide.

  The amount of the photopolymerization initiator (S1) contained in the photocurable resin composition is based on the total amount of the light transmission part constituent composition (100% by mass) from the viewpoint of curability and cost of the photocurable resin composition. 0.5 mass% or more and 5.0 mass% or less is preferable. Generally, the photoinitiator is at least partially soluble (eg, at the processing temperature of the resin) and is substantially colorless after polymerization. The photopolymerization initiator may be colored (for example, colored yellow), provided that it is substantially colorless when the light transmissive part constituent composition is cured to form a light transmissive part.

  These photocurable prepolymer (P1), reactive diluent monomer (M1) and photopolymerization initiator (S1) can be used alone or in combination of two or more.

  The light transmitting unit constituting composition sandwiched between the roll mold 20 and the base material 11 ′ and filled therein is irradiated with light from the base material 11 ′ side by the light irradiation device 42. Thereby, the light transmissive portion constituting composition 13 ′ can be cured and its shape can be fixed. And the base material layer 11 and the shape | molded light transmission part 13 are released from the roll metal mold | die 20 with the release roll 43. FIG.

  Next, the light absorption part 14 is formed. In order to form the light absorbing portion 14, first, the light absorbing portion constituting composition is excessively applied to the concave portion 13a. Thereafter, the surplus light absorbing part constituting composition is scraped off with a doctor blade or the like. Then, by irradiating light from the light transmitting portion side to the light absorbing portion constituting composition remaining in the recess 13a, the binder 15 contained in the light absorbing portion constituting composition is cured to form the light absorbing portion 14. it can.

  Although what is used as a binder is not specifically limited, For example, the photocurable resin composition which mix | blended the reactive dilution monomer (M2) and the photoinitiator (S2) with the photocurable prepolymer (P2). Is preferably used.

  Examples of the photocurable prepolymer (P2) include urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate.

  Moreover, as a reactive dilution monomer (M2), a vinyl monomer, a (meth) acrylic acid ester monomer, and a (meth) acrylamide derivative are mentioned as a monofunctional monomer, for example. Moreover, (meth) acrylate type thing is mentioned as a polyfunctional monomer.

  Examples of the photopolymerization initiator (S2) include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1 -One, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, and the like. Among these, the irradiation device for curing the photocurable resin composition and the curability of the photocurable resin composition can be arbitrarily selected.

  The amount of the photopolymerization initiator (S2) contained in the photocurable resin composition is based on the total amount of the photocurable resin composition from the viewpoint of curability and cost of the photocurable resin composition (100% by mass). ) Is preferably 0.5% by mass or more and 10.0% by mass or less.

  These photocurable prepolymer (P2), reactive diluent monomer (M2), and photopolymerization initiator (S2) can be used alone or in combination of two or more.

  Specifically, a photopolymerizable component composed of urethane acrylate, epoxy acrylate, tripropylene glycol diacrylate and methoxytriethylene glycol acrylate (specifically, photocurable prepolymer (P2) and reactive dilution monomer (M2)). In consideration of the refractive index, the viscosity, the influence on the performance of the optical function layer 12, etc., they are arbitrarily mixed and used.

  Moreover, you may add a silicone, an antifoamer, a leveling agent, a solvent, etc. to an optical absorption part structure composition as an additive as needed.

  The light absorbing particles 16 are preferably light-absorbing colored particles such as carbon black, but are not limited thereto, and are colored particles that selectively absorb a specific wavelength in accordance with the characteristics of image light. May be used. Specific examples include organic fine particles colored with metal salts such as carbon black, graphite, and black iron oxide, dyes, pigments, colored glass beads, and the like. In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like. More specifically, acrylic cross-linked fine particles containing carbon black, urethane cross-linked fine particles containing carbon black, and the like are preferably used. Such colored particles are usually contained in the light absorbing part constituting composition in a range of 3% by mass to 30% by mass. The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less. As will be described later, when the light absorbing portion 14 is formed, the light absorbing portion constituting composition containing the colored particles is filled in the recesses 13a between the light transmitting portions 13, and then the excess light is used using a doctor blade. A step of scraping off the absorbent part composition is included. At this time, by using colored particles having an average particle diameter of 1.0 μm or more, it becomes difficult for the colored particles to pass through the gap between the doctor blade and the upper portion of the light transmitting portion 13, and the colored particles are formed on the upper portion of the light transmitting portion 13. Can be prevented from remaining.

  As described above, the optical sheet 10 can be obtained by forming the light transmitting portion 13 and the light absorbing portion 14 on the base material layer 11.

  The optical sheet 10 may be further laminated with layers having other functions as necessary. Specifically, for example, an electromagnetic wave shielding layer, a wavelength filter layer, an antiglare layer, an antireflection layer, a hard coat layer, and the like can be formed by bonding using an adhesive layer. The order of lamination of these layers and the number of laminations are appropriately determined according to the use of the optical sheet. Any layer may be a known layer. Each layer will be described below.

  The electromagnetic wave shielding layer is a layer having a function of shielding electromagnetic waves. As long as the layer has the function, a means for blocking electromagnetic waves is not particularly limited. Examples thereof include a metal mesh formed by a method such as an etching method, a printing method, a vapor deposition method, or a sputtering method.

  The wavelength filter layer is a layer having a function of attenuating and transmitting light of a predetermined wavelength. The light of the wavelength to be attenuated can be selected as needed, but the layer that attenuates / blocks the neon line emitted from the plasma display panel (PDP), attenuates / blocks infrared rays, near infrared rays, and ultraviolet rays. Examples thereof include a layer and a layer capable of adjusting the color tone of the emitted light.

  The antiglare layer is a layer having a function of suppressing so-called glare and is sometimes called an antiglare layer or an AG layer.

  The antireflection layer is a layer that is disposed closest to the viewer and has a function of preventing reflection of external light. According to this, it can suppress that external light reflects on the observer side surface of an optical sheet, returns to the observer side, and what is called reflection arises and it becomes difficult to see an image | video.

  The hard coat layer is sometimes called a protective layer or an HC layer. This is a layer in which a film having a function capable of imparting scratch resistance is provided in order to prevent the image display surface from being scratched.

  The adhesive layer is a layer in which an adhesive is disposed. An acrylic adhesive can be mentioned as this adhesive. However, the pressure-sensitive adhesive is not limited to this as long as necessary light transmittance, adhesiveness, and weather resistance can be obtained. Depending on the layer structure, it is desirable to include a UV absorber (benzotriazole type or the like) having an effect of absorbing ultraviolet rays in the pressure-sensitive adhesive in order to prevent deterioration of the pigment. Moreover, a UV absorber, a near-infrared absorber, a neon ray absorber, and a toning pigment may be included in the adhesive layer in the adhesive layer.

3. Video Display Device Next, the video display device of the present invention will be described. The video display device of the present invention includes the optical sheet of the present invention and a video light source. An example of the video light source is a PDP. By sticking the optical sheet of the present invention to the image light emitting side of the image light source via an adhesive layer or the like, the image display device of the present invention can be configured.

  FIG. 10 is an exploded perspective view schematically showing a plasma television 100 which is an image display device of the present invention according to one embodiment. In FIG. 10, the upper right side of the drawing shows the observer side, and the lower left side of the drawing shows the back side. As can be seen from FIG. 10, the plasma television 100 includes a PDP unit 110 that is a video source unit inside a casing formed by a front casing 130 and a rear casing 120. The PDP unit 110 includes a PDP and an optical sheet from the back side of the plasma television 100 toward the viewer side, and the optical sheet is bonded to the PDP with an adhesive layer. The optical sheet is the optical sheet of the present invention. The PDP is a plasma display panel, which is a flat image light source, and the one used for a normal plasma television can be applied as it is. Accordingly, like a normal PDP, pixels each having three primary color phosphors as one unit are arranged in parallel vertically and horizontally, and an electrode for causing gas discharge to emit light is provided.

  In addition to the PDP unit 110, the plasma television 100 is provided with various ordinary devices included in the plasma television in the casing. Examples thereof include various electric circuits and cooling means.

  Here, the plasma television is exemplified as the video display device of the present invention, but the present invention is not limited to such a form. For example, as an image light source, a generally known electroluminescent display panel (FED), surface conduction electron-emitting device display (SED), organic EL, or the like can be used.

  As described above, the video display device of the present invention includes the optical sheet of the present invention. That is, the video display apparatus of the present invention can easily make the viewing angle the same in the vertical direction of the screen, for example.

  Hereinafter, the present invention will be described in more detail with reference examples. However, the present invention is not limited to the examples.

(Example)
A mold cylinder having a diameter of 300 mm was prepared, and a hard copper plating (Vickers hardness 210 Hv) as a work layer was formed on the surface with a thickness (one side) of 0.5 mm. This was used as a roll base. Then, using a lathe, grooves and annular protrusions were formed on the roll base to produce a roll mold. The rotation speed of the roll mold was set to 420 rpm. A diamond tool was used as the cutting tool, and the diamond tool had a trapezoidal shape when the tip was viewed from the rake face side, the tip width was 35 μm, and the taper angles on both sides were 1.83 degrees. By inclining this diamond tool once, the angle of the lateral relief surface on the front side in the feed direction with respect to the rotation axis of the mold roll is 2.83 degrees, and the side of the die roll on the lateral relief surface on the rear side in the feed direction. Cutting was performed so that the angle with respect to the rotation axis was 0.83 degrees. The feeding angle of the cutting tool was 0.83 degrees, and the feeding speed was 2 μm / rotation. Further, the groove pitch was 45 μm and the cut depth was 94 μm. Forming grooves and annular protrusions over the width of the roll base (length in the axial direction) 250 mm as described above was repeated twice. In the first cutting, a new cutting tool was used, and in the second cutting, a used cutting tool after forming grooves and annular projections as described above over the width 1580 mm of the roll base was used. The first cutting assumes a part where the cutting is started, and the second cutting assumes a part where the cutting is finished. As a result, the first and second cuttings were completed without any problem, and the appearance was good.

(Comparative example)
A mold cylinder having a diameter of 400 mm was prepared, and a hard copper plating (Vickers hardness 210 Hv) as a work layer was formed on the surface with a thickness (one side) of 0.5 mm. This was used as a roll base. Then, using a lathe, grooves and annular protrusions were formed on the roll base to produce a roll mold. The rotation speed of the roll mold was set to 440 rpm. A diamond tool was used as the cutting tool, and the diamond tool had a trapezoidal shape when the tip was viewed from the rake face side, the tip width was 35 μm, and the taper angles on both sides were 2.83 degrees. The front flank was cut with the diamond tool so that the front flank was parallel to the rotation axis of the roll mold. The feeding angle of the cutting tool was 2.83 degrees, and the feeding speed was 2 μm / rotation. Further, the groove pitch was 45 μm and the cut depth was 94 μm. Grooves and annular projections were formed as described above over the width 1580 mm of the roll base.

(Production of optical sheet)
Using the roll mold described above, optical sheets of Examples and Comparative Examples were produced by the following procedure. First, a base material (PET film, trade name: A4300, manufactured by Toyobo Co., Ltd., thickness 100 μm) is inserted and conveyed between the roll mold and the nip roll. The composition was supplied onto the substrate from a supply device. The light transmitting portion constituting composition is filled between the substrate and the roll die by the pressing force between the roll die and the nip roll, and 800 mJ / cm ^{2 is} applied from the substrate side by an electrodeless UV lamp manufactured by Fusion UV Systems. The ultraviolet rays were irradiated. In this way, the light transmitting portion constituting composition was cured to form a light transmitting portion. Then, the light transmission part was released from the roll mold with a peeling roll, and an intermediate member in which the light transmission part was formed on the substrate was produced. Next, the light absorption part constituent composition was supplied from the supply device onto the intermediate member. In addition, using a doctor blade disposed substantially perpendicular to the traveling direction of the intermediate member, the light absorbing portion constituting composition supplied onto the intermediate member is filled in the recesses between the light transmitting portions, and an excess of the light absorbing portion The constituent composition was scraped off. Thereafter, the light absorbing part constituting composition was cured by irradiating with 800 mJ / cm ² of ultraviolet rays with the electrodeless UV lamp, and a light absorbing part was formed with the cured light absorbing part constituting composition. By the above procedure, an optical sheet in which an optical functional layer having a light transmission part and a light absorption part was formed on a substrate was produced.

(Evaluation)
About the optical sheet concerning the Example produced using a roll metallic mold as mentioned above, and the optical sheet concerning the comparative example concerning a comparative example, a viewing angle measuring device (GP-500 made by Murakami Color Research Laboratory Co., Ltd.) ) To measure the transmittance at ± 80 degrees. The Lorentz function was footed to the data, and the angle with the highest transmittance was calculated. The results are shown in FIG.

  In this evaluation, the parallel direction of the light transmitting parts is the vertical direction, and the part molded by the part where the cutting of the roll mold is started is formed by the lower part, the part where the cutting of the roll mold is finished. While arrange | positioning an optical sheet so that a part might become an upper side, it irradiated by light from the base-material side. In the graph shown in FIG. 11, the horizontal axis is “distance from the cutting start position [mm]”. That is, the left side of the graph shown in FIG. 11 is a portion formed by the portion where the cutting of the roll mold is started (the portion cut by the first cutting (the portion assuming the portion where cutting was started)). It is a result and the right side is a result in the part shape | molded by the site | part (The site | part cut | disconnected by the 2nd cutting (site | part which assumed the site | part which cut | disconnected cutting | disconnection)) which complete | finished cutting of a roll metal mold | die. On the other hand, the vertical axis represents the shift amount [°] of the peak position. Note that “the shift amount [°] of the peak position” means a direction having the highest transmittance when the normal direction of the sheet surface of the optical sheet is 0 °. Here, the upper side of the normal direction of the sheet surface of the optical sheet is +, and the lower side is −.

  In the optical sheet according to the example, the direction in which the light transmission part falls was different between the upper side and the lower side of the optical sheet. Therefore, as shown in FIG. 11, one side and the other side from the substantially central portion of the optical sheet. It is thought that + and-of the shift amount [°] of the peak position are opposite to each other. On the other hand, in the optical sheet according to the comparative example, the light transmission portion is greatly tilted from the lower side to the upper side of the optical sheet. Therefore, as shown in FIG. It is considered that the position shift amount [°] has increased. Further, it can be seen from the results shown in FIG. 11 that the optical sheet according to the example has a smaller shift amount [°] of the peak position as a whole than the optical sheet according to the comparative example. This is presumably because the tilt of the light transmission part was smaller on the whole in the optical sheet according to the example than in the optical sheet according to the comparative example.

DESCRIPTION OF SYMBOLS 10 Optical sheet 11 Base material layer 12 Optical functional layer 13 Light transmission part 14 Light absorption part 15 Binder part 16 Light absorption particle 20 Roll metal mold | die 21 Roll base | substrate 22 Annular protrusion 23 Groove

Claims (4)

An optical sheet having an optical functional layer having a light transmission part formed so as to be able to transmit light and a light absorption part formed so as to be able to absorb light, and disposed on the viewer side of the image light source,
The light transmitting portion is provided with a trapezoidal cross-section, while being parallel along the sheet surface at equal intervals in a short upper base side of trapezoid cross-section, the light absorbing portion is formed between the light transmitting portion,
The light transmitting portions are inclined toward the adjacent light absorbing portions at both ends in the parallel direction of the light transmitting portions, and the light transmitting portions are arranged at one end and the other end in the parallel direction of the light transmitting portions. An optical sheet characterized in that the direction in which is inclined is opposite.   The optical sheet according to claim 1, wherein the light transmission part is inclined toward the outside of the optical sheet at both ends in the parallel direction of the light transmission part. A layer capable of adjusting a color tone of light emitted from the image light source;
The optical sheet according to claim 1, wherein the optical functional layer is disposed on a side closest to the observer side. A video display device comprising an optical sheet disposed on the viewer side of Film image light source and said video source,
The optical sheet has an optical functional layer having a light transmission part formed so as to be able to transmit light and a light absorption part formed so as to be able to absorb light,
The light transmitting portion is provided with a trapezoidal cross-section, while being parallel along the sheet surface at equal intervals in a short upper base side of trapezoid cross-section, the light absorbing portion is formed between the light transmitting portion,
The video display device, wherein the light transmission part is inclined in the opposite direction between one end part and the other end part in the parallel direction of the light transmission part.

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