JP2014044368A - Method for manufacturing light guide plate - Google Patents

Abstract

A light guide plate manufacturing method capable of efficiently manufacturing a light guide plate having a desired degree of chromaticity uniformity.
A light guide plate manufacturing method is characterized in that the shape of a transfer mold 69 is compared with a resin sheet made of a styrene resin or a polycarbonate resin in which different bluing agent formulations are made by adjusting the amount of bluing agent added. Is transferred to the prototype molding step S1 for molding a plurality of light guide plate prototypes, an evaluation step S2 for evaluating the chromaticity uniformity of each of the plurality of light guide plate prototypes, and the evaluated chromaticity uniformity. Based on the determined step S3 for determining the addition amount of the bluing agent to make the light guide plate 30 that emits light of the desired degree of chromaticity uniformity, the light guide plate 30 is changed based on the determined addition amount of the bluing agent. A light guide plate forming step S4 to be formed.
[Selection] Figure 4

Description

  The present invention relates to a method for manufacturing a light guide plate and a light guide plate.

  A transmissive image display device such as a liquid crystal display device generally has a surface light source device as a backlight. As a method of the surface light source device, there are a direct type in which a light source is provided on the back side of the light guide plate and an edge light method in which a light source is provided along the side surface of the light guide plate. The edge light method is advantageous from the viewpoint of reducing the thickness of the image display device, and development of a high-luminance and large-sized surface light source device by the edge light method is strongly desired.

  In the case of an edge light type surface light source device, light incident from the side surface of the light guide plate is reflected by the action of a reflective portion such as a white dot provided on the back side of the light guide plate, and light having an angle component greater than the critical angle The light exits from the exit surface of the light guide plate.

  As the translucent material forming the base material of the light guide plate (light guide plate base material), in addition to the acrylic resin, a styrene resin or a polycarbonate resin which is a resin containing a styrene monomer unit is used. Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-204536) discloses that a styrene resin molded into a plate shape is used as a light guide plate.

JP 2007-204536 A

  When such a styrene resin or polycarbonate resin is used for the light guide plate base material, light emitted from a region far from the light source may be yellowish, and so-called uneven chromaticity is displayed on the image display of the light guide plate. May occur. In order to cope with this, as disclosed in Patent Document 1, it is conceivable to add a bluing agent to a styrene-based resin and form it into a plate shape to form a light guide plate base material. However, in order to obtain a light guide plate from which light having a desired chromaticity uniformity is emitted, it is necessary to add an appropriate amount of a bluing agent. For this reason, the production of the prototype and the evaluation of the chromaticity uniformity in the prototype are often repeated on a trial and error basis, and the actual situation is that much cost and time are required.

  Then, the main objective of this invention is to provide the manufacturing method of the light-guide plate which can manufacture efficiently the light-guide plate which has desired chromaticity uniformity.

  The light guide plate manufacturing method according to the present invention has a transfer mold shape with respect to a resin sheet made of a styrene resin or a polycarbonate resin in which different bluing agent prescriptions are made by adjusting the amount of bluing agent added. A prototype forming step for forming a plurality of light guide plate prototypes by transferring, an evaluation step for evaluating the chromaticity uniformity of each of the plurality of light guide plate prototypes, and a desired based on the evaluated chromaticity uniformity Determining step of determining the addition amount of the bluing agent to make a light guide plate that emits light of the same degree of chromaticity, and forming the light guide plate based on the determined addition amount of the bluing agent Steps.

  According to this manufacturing method, a plurality of light guide plate prototypes having different chromaticity uniformity can be easily formed by changing the bluing agent formulation of the light guide plate, and the chromaticity distribution obtained from these light guide plate prototypes can be obtained. By evaluating the chromaticity uniformity based on this, it is possible to easily determine the addition amount of the bluing agent that achieves the desired chromaticity uniformity. Thereby, the light-guide plate which has desired chromaticity uniformity can be manufactured efficiently.

  In the light guide plate manufacturing method according to the present invention, in the evaluation step, the brightness uniformity of each of the plurality of light guide plate prototypes is further evaluated, and in the determination step, a desired value is obtained based on the evaluated chromaticity uniformity and brightness uniformity. The addition amount of the bluing agent for producing a light guide plate that emits light having the same chromaticity uniformity and luminance uniformity may be determined.

  According to this manufacturing method, the desired chromaticity uniformity and luminance uniformity are obtained by evaluating the chromaticity uniformity and luminance uniformity based on the chromaticity distribution and luminance distribution of the plurality of light guide plate prototypes. The amount of bluing agent added can be determined. Thereby, the addition amount of the bluing agent for making the light guide plate that emits light having a desired chromaticity uniformity can be determined while reducing the luminance and the luminance uniformity.

  In the light guide plate manufacturing method according to the present invention, the resin sheet in the prototype molding step is further formulated with a different matting agent, and in the determination step, based on the evaluated brightness uniformity, a desired brightness uniformity is obtained. The matting agent prescription for making the light guide plate that emits light of the degree may be further determined, and in the light guide plate forming step, the light guide plate may be further formed based on the determined matting agent prescription.

  The matting agent here refers to a particle component for forming an uneven surface for diffusing light on the surface of the light guide plate (light guide plate substrate). The matting agent prescription means adjusting the surface roughness of the light guide plate.

  Furthermore, according to this manufacturing method, a plurality of light guide plate prototypes having different brightness uniformity are formed by changing the prescription of the matting agent of the light guide plate. In order to prepare such a light guide plate prototype, Therefore, it is not necessary to newly produce a prototype transfer mold having different uneven shapes. Therefore, a light guide plate that emits light having a desired luminance uniformity can be manufactured more efficiently and at low cost.

  In the light guide plate manufacturing method according to the present invention, the matting agent formulation may be performed by adjusting the amount of the matting agent added. Thereby, the surface roughness of a light-guide plate can be adjusted.

  In the light guide plate manufacturing method according to the present invention, the matting agent formulation may be performed by adjusting the temperature at which the layer to which the matting agent is added leaves the transfer mold. Thereby, the surface roughness of a light-guide plate can be adjusted.

  In the method for producing a light guide plate according to the present invention, the matting agent is a particle component having the same refractive index as that of the styrene resin or polycarbonate resin to which the matting agent is added, or the refractive index of the styrene resin or polycarbonate resin. May be a particle component having a difference of 0.01 or less.

  In the light guide plate manufacturing method according to the present invention, in the prototype forming step, the shape of the transfer mold may be transferred at a predetermined transfer rate to a resin sheet having a different bluing agent formulation and matting agent formulation. Good.

  In the light guide plate manufacturing method according to the present invention, in the light guide plate forming step, the determined amount of the bluing agent is added and the resin sheet subjected to the determined matting agent formulation is a prototype forming step. The light guide plate may be formed by transferring the shape of the transfer mold used in step 1 at the same transfer rate as when it was transferred in the prototype forming step.

  According to this manufacturing method, a light guide plate from which light having a desired chromaticity uniformity and luminance uniformity is emitted is manufactured using the transfer mold used when forming the light guide plate prototype as it is. There is no need to newly prepare a transfer mold for manufacturing the light guide plate. This makes it possible to manufacture a light guide plate that emits light having a desired luminance uniformity more efficiently and at low cost.

  In the light guide plate manufacturing method according to the present invention, in the prototype forming step, when the transfer mold shape is transferred, the transfer mold shape is transferred at a different transfer rate, thereby forming different uneven shapes, and the evaluation step. In order to further evaluate the peak angle of each of the plurality of light guide plate prototypes, and in the determining step, the unevenness for forming a light guide plate that emits light of a desired luminance uniformity and peak angle based on the evaluated peak angle The shape may be further determined, and in the light guide plate forming step, the light guide plate may be further formed based on the determined uneven shape.

  According to this manufacturing method, since the uneven shape can be adjusted by changing the transfer rate of the shape from the transfer mold, the peak angle of the emitted light can be adjusted in addition to the chromaticity uniformity and the luminance uniformity. Will be able to. As a result, a light guide plate that emits light at a desired chromaticity uniformity, luminance uniformity, and peak angle can be manufactured more efficiently and at a lower cost, and the light guide plate is disposed on the output side of the light guide plate. It is possible to manufacture an optimal light guide plate that matches the characteristics of the optical member.

  In the light guide plate manufacturing method according to the present invention, in the light guide plate forming step, the determined amount of bluing agent is added and the resin sheet having the determined matting agent prescription is used as a prototype forming step. The light guide plate may be formed by transferring the shape of the transfer mold used in step 1 at a transfer rate corresponding to the determined uneven shape.

  According to this manufacturing method, a light guide plate that emits light of desired chromaticity uniformity, luminance uniformity, and peak angle is manufactured using the transfer mold used when forming the light guide plate prototype as it is. Therefore, it is not necessary to newly prepare a transfer mold for manufacturing the light guide plate. As a result, a light guide plate from which light having a desired chromaticity uniformity, luminance uniformity, and peak angle is emitted can be manufactured more efficiently and at low cost.

  In the light guide plate manufacturing method according to the present invention, in the light guide plate forming step, the determined unevenness is determined with respect to the resin sheet to which the determined amount of bluing agent is added and the determined matting agent is formulated. The light guide plate may be formed by transferring a transfer mold for manufacturing a light guide plate having an inverted shape corresponding to the shape.

  According to this manufacturing method, since a transfer mold for manufacturing a light guide plate can be easily prepared, a light guide plate from which light having a desired chromaticity uniformity, luminance uniformity, and peak angle is emitted can be more efficiently obtained. And it becomes possible to manufacture at low cost.

  In the method of manufacturing the light guide plate according to the present invention, the transfer mold for manufacturing the light guide plate has a shape that becomes the determined uneven shape when transferring at a transfer rate of 25% to 90% with respect to the resin sheet. You may have.

  The light guide plate manufacturing method according to the present invention further includes a confirmation step of finding a stable transfer rate when the line speed is increased to a predetermined speed using the transfer mold used in the prototype molding step, In the molding step, the determined concavo-convex shape is obtained at the transfer rate found by the confirmation step for the resin sheet to which the determined amount of the bluing agent is added and the matting agent is determined. The light guide plate may be formed by transferring a light guide plate manufacturing transfer mold having such a shape.

  In order to increase the productivity of the light guide plate, it is necessary to increase the line speed of extrusion molding. In that case, a transfer mold that can mold the uneven shape determined by the determining step at an appropriate transfer rate must be used. The fact that a light guide plate having excellent luminance uniformity cannot be obtained has been found by the present inventors. Therefore, a stable transfer rate (stability transfer rate) that is easy to manage when the line speed is increased to a predetermined speed using the transfer mold used in the prototype molding step, in other words, resin peeling from the roll. To find a transfer rate that is less likely to cause defects in appearance and appearance and can improve productivity, and to obtain an uneven shape determined by evaluating the chromaticity uniformity, luminance uniformity, and peak angle at the transfer rate. A transfer mold for manufacturing an optical plate is produced, and a light guide plate is manufactured using the transfer mold for manufacturing a light guide plate. As a result, a light guide plate from which light having a desired chromaticity uniformity, luminance uniformity, and peak angle is emitted can be manufactured more efficiently and at low cost.

  In the method of manufacturing the light guide plate according to the present invention, the transfer rate having stability may be 25% or more and 90% or less.

  In the method of manufacturing the light guide plate according to the present invention, the resin sheet in the prototype molding step is further formulated with a diffusing agent. In the determination step, light having a desired luminance uniformity is obtained based on the evaluated luminance uniformity. The diffusing agent prescription for making the light guide plate that emits light may be further determined, and in the light guide plate forming step, the light guide plate may be further formed based on the determined diffusing agent prescription.

  The term “diffusing agent” as used herein refers to a particle component that is added to the base resin and has a refractive index different from that of the base resin, and has an effect of diffusing and reflecting light incident on the particle. The term “diffusing agent prescription” refers to adjusting the diffusion strength of the light guide plate, for example, adjusting the thickness of the layer to which the diffusing agent is added, or adjusting the amount of the diffusing agent added to the base resin. Is done. In addition, the spreading | diffusion agent prescription | regulation with respect to the resin sheet in a prototype shaping | molding step may mutually differ, and may be the same.

  According to this manufacturing method, the brightness uniformity can be adjusted with higher accuracy by prescribing the diffusing agent to such an extent that chromaticity unevenness does not occur, that is, the chromaticity uniformity does not deteriorate.

  In the light guide plate according to the present invention, the light guide plate base portion having a light exit surface that emits light and a back surface opposite to the light exit surface, and the back surface side of the light guide plate base material portion are provided. And a reflection portion that reflects the light. The light guide plate base material portion is formed from a styrene resin or a polycarbonate resin containing a bluing agent. The outermost layer on the light exit surface side in the light guide plate base material portion contains a matting agent for forming an uneven surface for diffusing light on the light exit surface.

  According to this light guide plate, the diffusion intensity can be easily adjusted as compared with the light guide plate in which the diffusion intensity is adjusted by adjusting the shape of the transfer mold or processing the surface. Further, the chromaticity uniformity can be adjusted simultaneously with the adjustment of the diffusion intensity. This makes it possible to provide a light guide plate with high production efficiency.

  In the light guide plate according to the present invention, the matting agent is a particle component having the same refractive index as that of the styrene resin or the polycarbonate resin, or a particle component having a refractive index difference of 0.01 or less from that of the styrene resin or the polycarbonate resin. There may be.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the light guide plate which can manufacture the light guide plate which has desired chromaticity uniformity degree more efficiently and at low cost can be provided.

It is a perspective view which shows one Embodiment of the light-guide plate manufactured with the manufacturing method of the light-guide plate which concerns on this invention. It is a schematic diagram which shows schematic structure of one Embodiment of the transmissive image display apparatus containing the light-guide plate shown in FIG. It is the schematic block diagram which shows an example of the manufacturing apparatus which manufactures the optical sheet used as a light-guide plate, and the figure which expanded and showed the one part side surface of the optical sheet manufactured by the manufacturing apparatus which manufactures an optical sheet. It is a flowchart which shows one Embodiment of the manufacturing method of a light-guide plate. It is a schematic diagram which shows one Embodiment of the manufacturing method of the optical sheet used as a light-guide plate. It is a perspective view which shows an example of the shape of the light-guide plate of each experiment example, and a measuring method. It is drawing which shows an example of the directivity of the point light source in each experiment example. It is drawing which shows an example of the recessed part shape formed in the transfer type | mold used when shape | molding the light-guide plate of each experiment example. The graph which showed distribution of the depth of the recessed part in the circumferential direction of the transfer type | mold used when shape | molding the light-guide plate of each experiment example. The graph which showed distribution of the coverage of the recessed part in the circumferential direction of the transfer type | mold used when shape | molding the light-guide plate of each experiment example. It is the graph which showed the measurement result of the chromaticity of the light-guide plate of each experiment example. It is the graph which showed the measurement result of the brightness | luminance of the light-guide plate of each experiment example. It is the graph which showed the result of the chromaticity difference of a light guide plate of each experiment example, and a brightness | luminance uniformity. It is a flowchart which shows other embodiment of the manufacturing method of a light-guide plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The dimensional ratios in the drawings do not necessarily match those described. Further, in the description, words indicating directions such as “up” and “down” are convenient words based on the state shown in the drawings.

  FIG. 1 is a perspective view showing an embodiment of a light guide plate manufactured by the method of manufacturing a light guide plate according to the present invention. The light guide plate 30 shown in FIG. 1 has a light guide plate base material portion 33 having a pair of main surfaces 30a and 30b having a rectangular shape in plan view and four side surfaces 30c to 30f orthogonal to the main surface, and one main surface 30a. And a ridge portion (reflecting portion) 34 that forms a concavo-convex shape on the surface.

  The ridge 34 is for irregularly reflecting light propagating in the light guide plate 30 and emitting it from the exit surface 30b side. The outer shape of the ridge 34 is the shape of a lenticular lens. The protruding portion 34 extends in a direction along one side of the main surface 30a. The cross-sectional shape perpendicular to the extending direction of the ridges 34 is almost uniform in any part in the extending direction. The concavo-convex shape formed by the ridges 34 is formed by transfer from a transfer die 69 (see FIG. 3A).

The coverage of the ridges 34 increases as the distance from the side surface 30c increases along the direction orthogonal to the side surface 30c (the X-axis direction in FIG. 1). The coverage of the ridge 34 is defined by, for example, the following equation by the distance g between the ends of the adjacent ridges 34 and the width w of the ridge 34.
Covering rate of ridges = w / (g + w)

  The light guide plate 30 is made of a translucent resin that transmits light and is formed in a plate shape. The translucent resin forming the light guide plate 30 is a styrene resin or a polycarbonate resin. Examples of the styrenic resin include polystyrene resin. As shown in FIGS. 1 and 2, the light guide plate 30 has a two-layer / two-layer configuration including a base layer 31 and a surface layer 32 constituting the outermost layer on the emission surface 30 b side. The translucent resin forming the surface layer 32 contains a bluing agent. The content of the bluing agent in the surface layer 32 is 0.1 ppm to 5 ppm, preferably 0.5 ppm to 2 ppm, based on the mass of the surface layer 32.

  The bluing agent is not particularly limited as long as it is usually used. For example, Macrolex Blue RR (trade name, manufactured by Bayer), Macrolex Blue 3R (trade name, manufactured by Bayer), and polysynthrene. Blue RLS (manufactured by Clariant, trade name) can be mentioned.

  Further, a matting agent is further added to the translucent resin forming the surface layer 32. The matting agent here is the same as the above-described translucent material (or transparent material) forming the surface layer 32, or the difference in refractive index between the translucent material is 0.01 or less. This is a particle component (powder) of which the output surface 30b is matted (roughened) by protruding the particle component from the surface of the surface layer 32.

  For example, the surface layer 32 of the light guide plate 30 can be made of PS resin with a thickness of 50 μm to 300 μm. For example, PS resin particles having a particle size of 30 μm may be added to the surface layer 32 as a matting agent in a concentration of 0.1 to 15% by weight. As such a matting agent, for example, organic particles such as PS resin particles are used depending on the constituent resin, and the particle diameter can be usually 1 μm to 50 μm.

  A diffusing agent may be added to the translucent resin forming the light guide plate 30 to the extent that the gist of the present invention and color unevenness do not occur. The diffusing agent here refers to a particle component (powder) having a refractive index different from that of the above-described translucent material (or transparent material) mainly constituting the light guide plate 30, and this is referred to as translucency. Used by being dispersed in the material. Examples of such a diffusing agent include organic particles such as styrene resin particles, methacrylic resin particles, and silicone resin particles, and inorganic particles such as potassium carbonate particles, silica particles, titanium oxide particles, and calcium carbonate particles. Is usually 0.8 μm or more and 50 μm or less.

  In addition, additives such as an ultraviolet absorber, an antistatic agent, an antioxidant, a processing stabilizer, a flame retardant, and a lubricant can be added to the light guide plate 30 without departing from the spirit of the present invention. These additives can be used alone or in combination of two or more.

  FIG. 2 is a schematic diagram illustrating a schematic configuration of an embodiment of a transmissive image display device including the light guide plate illustrated in FIG. 1, and illustrates an exploded cross-sectional configuration of the transmissive image display device. The transmissive image display device 1 can be suitably used as a display device for a mobile phone or various electronic devices or a television device.

  Examples of the transmissive image display unit 10 include a color liquid crystal display panel in which linearly polarizing plates 12 and 13 are disposed on both surfaces of a liquid crystal cell 11. In this case, the transmissive image display device 1 is a color liquid crystal display device (or color liquid crystal television). As the liquid crystal cell 11 and the polarizing plates 12 and 13, those used in a transmissive image display device such as a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 11 include known liquid crystal cells such as TFT (Thin Film Transistor) type liquid crystal cells and STN (Super Twisted Nematic) type liquid crystal cells.

  As shown in FIG. 2, the surface light source device 20 is opposed to the light guide plate 30, the light source unit 21 disposed facing the side surfaces 30 c and 30 d of the light guide plate 30, and the main surface 30 a of the light guide plate 30. This is an edge light type surface light source device including a reflection sheet 25 arranged.

  In the light guide plate 30, the other main surface 30 b is positioned on the transmissive image display unit 10 side, and the one main surface 30 a on which the ridges 34 are formed is positioned on the opposite side to the transmissive image display unit 10. To be arranged. In addition, the light guide plate 30 has a protrusion 34 formed on one main surface (hereinafter also referred to as “rear surface”) 30a, and a side surface (hereinafter referred to as “incident surface”) on which light from the light source unit 21 is incident. It is arranged so as to extend in a direction parallel to the longitudinal direction of 30c, 30d. As a result, light incident from the incident surfaces 30c and 30d of the light guide plate 30 is diffusely reflected by the ridges 34 and is emitted from the other main surface (hereinafter also referred to as “exit surface”) 30b.

  The light source unit 21 may be a plurality of LEDs (Light Emitting Diodes) arranged to face the side surfaces 30c and 30d of the light guide plate 30, respectively. The LEDs are discretely arranged along the longitudinal direction (Y-axis direction) of the side surfaces 30c and 30d. The light source unit 21 may be configured to be opposed to the four sides of the light guide plate 30, may be configured to be disposed on two sides opposed to the Y-axis direction, or only one side. The structure arrange | positioned may be sufficient. The light source unit 21 is not limited to the point light source as described above, and may be a configuration in which a linear light source such as a cold cathode fluorescent lamp (CCFL) is disposed.

  The transmissive image display device 1 may have a configuration in which various optical films 40 are disposed between the light guide plate 30 and the transmissive image display unit 10 on the light exit surface 30 b side of the light guide plate 30. Examples of the various optical films 40 include a diffusion film, a prism film, a brightness enhancement film, a lenticular lens film, a microlens film, and a reflective polarizing film.

(First embodiment)
Next, one Embodiment of the manufacturing method of the light-guide plate which concerns on this invention is described using FIGS. First, an apparatus for manufacturing the light guide plate 30 will be described. Fig.3 (a) is a schematic block diagram which shows an example of the manufacturing apparatus which manufactures the optical sheet used as a light-guide plate. FIG.3 (b) is sectional drawing to which the one part side surface of the optical sheet manufactured with the manufacturing apparatus shown to Fig.3 (a) was expanded. The light guide plate 30 is manufactured by cutting out an optical sheet 80 manufactured by an optical sheet manufacturing apparatus 60 as shown in FIG.

  As shown in FIG. 3A, the optical sheet manufacturing apparatus 60 includes a first extruder 61 for heating and melting a thermoplastic resin that becomes a base layer 81 (see FIG. 3B), and a surface layer 82 (FIG. 3). A second extruder 62 for heating and melting the thermoplastic resin to be (b)), a die 63 for extruding the molten resin supplied from the first and second extruders 61 and 62 into a sheet, A preloading roll 66, a first pressing roll 67, and a second pressing roll 68 for forming a two-type two-layer sheet-like resin sheet 70 extruded from a die 63 are provided. The preload roll 66, the first pressing roll 67, and the second pressing roll 68 are arranged such that the axes of the respective rolls are substantially parallel. The peripheral surfaces of the preload roll 66 and the first pressing roll 67 are mirror surfaces, and the peripheral surface of the second pressing roll 68 has a concave portion (groove) 69a corresponding to the concave-convex shape (protruded portion 34) of the light guide plate 30 (see FIG. 5) is provided.

  The resin sheet 70 discharged from the die 63 passes between the preload roll 66 and the first pressing roll 67. The thickness of the resin sheet 70 is mainly controlled by the distance between the preload roll 66 and the first pressing roll 67. The position where the resin sheet 70 that has passed between the preloading roll 66 and the first pressing roll 67 is pressed between the first pressing roll 67 and the second pressing roll 68 on the peripheral surface of the first pressing roll 67. It is conveyed to.

  The resin sheet 70 is pressed from both sides in the thickness direction when passing between the first pressing roll 67 and the second pressing roll 68, and the shape of the transfer mold 69 is transferred to the surface 70 a of the resin sheet 70. The resin sheet 70 to which the shape has been transferred is conveyed while being cooled, and taken up as an optical sheet 80. On one surface 80 a of the optical sheet 80, a concavo-convex shape is formed by the ridges 84 transferred from the transfer mold 69, as shown in FIG. The other surface 80b is formed flat. By cutting out the optical sheet 80 thus manufactured to a predetermined length, the light guide plate 30 having an uneven shape formed on one main surface 30a as shown in FIG. 1 is manufactured.

  Next, an embodiment of a method for manufacturing the light guide plate 30 will be described. FIG. 4 is a flowchart showing an embodiment of a method for manufacturing a light guide plate. As shown in FIG. 4, the manufacturing method of the light guide plate 30 in the present embodiment includes a prototype forming step S1, an evaluation step S2, a determining step S3, and a light guide plate forming step S4. Hereinafter, steps S1 to S4 will be described in order.

  In the prototype forming step S1, a plurality of light guide plate prototypes are formed by transferring the shape of a transfer mold at a predetermined transfer rate to resin sheets having different blueing agent formulations. As a result, a plurality of light guide plate prototypes having the same uneven shape and different bluing agent formulations are formed. The resin sheet has a matting agent having a predetermined concentration added to the translucent resin for forming the surface layer so that the luminance uniformity when transferred at a predetermined transfer rate is not less than a predetermined value. Also good. In the present embodiment, a resin sheet having a multilayer structure having a surface layer containing the matting agent will be described as an example.

  Specifically, a styrene resin and a styrene resin to which a bluing agent is added so as to have different concentrations are prepared, and the first extruder 61 and the second extruder of the optical sheet manufacturing apparatus 60 described above are prepared. 62, respectively. Note that a matting agent having a predetermined concentration is added to the styrene resin to which the bluing agent is added so that the luminance uniformity when transferred at a predetermined transfer rate is equal to or higher than a predetermined value. Next, the resins charged in the first extruder 61 and the second extruder 62 are respectively melted and kneaded and supplied to the die 63. Next, the molten resin supplied from the first extruder 61 becomes the base layer 81 (see FIG. 3B), and the molten resin supplied from the second extruder 62 becomes the surface layer 82 (see FIG. 3B). ) To be co-extruded by the die 63.

The coextrusion-molded two-type two-layer resin sheet 70 is pressed and cooled by the pre-press roll 66, the first press roll 67, and the second press roll 68 provided with the transfer die 69 on the peripheral surface. As a result, a two-type two-layer optical sheet 80 constituted by the base layer 81 and the surface layer 82 shown in FIG. In the present embodiment, changing the thickness t ₈₂ of the optical sheet 80 total thickness t ₈₀ and a surface layer 82 is fixed, the amount of the bluing agent added to the surface layer 82, i.e., the concentration of the bluing agent in the surface layer 82 However, by manufacturing the optical sheet 80, a plurality of light guide plate prototypes having different bluing agent formulations are manufactured. The transfer rate of the shape from the transfer die 69 at the time of molding is usually fixed to a constant value between 30% and 100%.

The transfer rate is the ratio of the height h ₁ of the concave portion 69a of the transfer mold to the height h ₃ of the convex portion 84 formed by the transfer when the shape of the transfer mold 69 is transferred, and (h ₃ / h ₁ ) × 100 (see FIGS. 5A to 5C).

  Note that the transfer die 69 used in the prototype forming step S1 is, for example, an existing uneven shape that emits light with a predetermined luminance uniformity degree when transferred under a predetermined condition (for example, transfer rate). It is also possible to use a transfer mold of this type, and it corresponds to a concavo-convex shape that emits light with a desired brightness uniformity if transferred under predetermined conditions, which is determined by each experimental example described later. Such a transfer mold may be used.

  In the evaluation step S2, the chromaticity uniformity of each of the plurality of light guide plate prototypes molded in the prototype molding step S1 is evaluated. Specifically, for a plurality of manufactured light guide plate prototypes, data (hereinafter also referred to as “chromaticity distribution”) that can grasp the change in chromaticity in the arrangement direction of the ridges 34 is acquired by simulation or actual measurement. Then, the chromaticity uniformity is evaluated. The chromaticity uniformity can be, for example, a value obtained by dividing the minimum value of chromaticity by the maximum value in the change in chromaticity in the obtained arrangement direction. It can also be evaluated using a chromaticity difference which is a difference between the minimum value and the maximum value of chromaticity.

  In the determination step S3, the addition amount of the bluing agent for manufacturing the light guide plate 30 that emits light of the desired chromaticity uniformity is determined based on the chromaticity uniformity evaluated in the evaluation step S2. Specifically, the blue color for obtaining the desired chromaticity uniformity by comparing the chromaticity uniformity of each prototype of the light guide plate evaluated in the evaluation step S2 with the target chromaticity uniformity. The concentration of the bluing agent at the surface layer 32 is determined.

  In the light guide plate forming step S4, the light guide plate is formed based on the addition amount of the bluing agent determined in the determination step S3. For example, using the shape of the transfer mold used when forming the light guide plate prototype for the resin sheet to which the addition amount of the bluing agent determined in the determination step S3 is added, By transferring at the same transfer rate as the molding, an optical sheet to be a light guide plate can be molded. This will be specifically described below.

  First, the same styrenic resin as that prepared in the prototype molding step S1 and a matting agent are added so as to have the same predetermined concentration as that prepared in the prototype molding step S1, and the determination step S3. And the styrenic resin to which the bluing agent is added so as to have the concentration determined in (1) above are prepared, and are respectively supplied to the first extruder 61 and the second extruder 62 of the optical sheet manufacturing apparatus 60 described above. Next, the resins charged in the first extruder 61 and the second extruder 62 are melt-kneaded and supplied to the die 63.

Next, the molten resin supplied from the first extruder 61 becomes the base layer 81 (see FIG. 3B), and the molten resin supplied from the second extruder 62 becomes the surface layer 82 (see FIG. 3B). ), The die 63 is used for coextrusion molding. The thickness t ₈₂ of the surface layer 82, co-extrusion molding is carried out so as to have the same thickness as when it is molded by the prototype molding step S1. The coextruded resin is sandwiched and cooled by the preload roll 66, the first pressing roll 67, and the second pressing roll 68, whereby the base layer 81 and the surface layer 82 shown in FIG. The optical sheet 80 used as the light-guide plate 30 of 2 types and 2 layers comprised by these can be obtained. Thereby, the light-guide plate 30 which radiate | emits the light of desired chromaticity uniformity can be obtained.

  The effect of the manufacturing method of the said light-guide plate 30 is demonstrated. According to the manufacturing method described above, a plurality of light guide plate prototypes having different chromaticity uniformity by adjusting the amount of the blueing agent added to the styrene-based thermoplastic resin forming the surface layer 32 (blueing agent prescription). Be prepared. By evaluating the chromaticity uniformity based on the chromaticity distribution obtained from these light guide plate prototypes, the concentration of the bluing agent that achieves the desired chromaticity uniformity can be easily determined. As described above, the light guide plate 30 having a desired chromaticity uniformity can be efficiently manufactured.

(Second Embodiment)
Next, another embodiment (hereinafter also referred to as “Embodiment 2”) of the method for manufacturing the light guide plate 30 will be described. Here, description of the manufacturing apparatus which manufactures the optical sheet 80 used as the light-guide plate 30 is abbreviate | omitted, and only the manufacturing method different from embodiment mentioned above is demonstrated in detail.

  First, the difference between the two in the prototype forming step S1 will be described. In the above embodiment (hereinafter also referred to as “Embodiment 1”), a plurality of light guide plate prototypes having different blueing agent formulations are formed, whereas in Embodiment 2, different blueing agent formulations are formed. A plurality of light guide plate prototypes having a matting agent formulation are formed.

  Specifically, a styrene resin and a styrene resin to which a blueing agent and a matting agent are added so as to have different predetermined concentrations are prepared, and the first extruder of the optical sheet manufacturing apparatus 60 described above is prepared. 61 and the second extruder 62, respectively. Next, the resins charged in the first extruder 61 and the second extruder 62 are respectively melted and kneaded and supplied to the die 63. Next, the molten resin supplied from the first extruder 61 becomes the base layer 81 (see FIG. 3B), and the molten resin supplied from the second extruder 62 becomes the surface layer 82 (see FIG. 3B). ), The die 63 is used for coextrusion molding.

  Next, the co-extruded resin is pressed and cooled by a pre-press roll 66, a first press roll 67, and a second press roll 68 provided with a transfer die 69 on the peripheral surface. The resin sheet 70 is pressed from both sides in the thickness direction when passing between the first pressing roll 67 and the second pressing roll 68, and the shape of the transfer mold 69 is transferred to the surface 70 a of the resin sheet 70. The resin sheet 70 onto which the shape of the transfer die 69 has been transferred at a predetermined transfer rate is conveyed while being cooled on the peripheral surface of the second pressing roll 68, and then taken up as the optical sheet 80. This is the same as in the first embodiment.

As described above, a two-type two-layer optical sheet 80 constituted by the base layer 81 and the surface layer 82 shown in FIG. Mat in this embodiment, is fixed thickness t ₈₂ of the optical sheet 80 total thickness t ₈₀ and a surface layer 82, which while changing the amount of bluing agent added to the surface layer 82, and is added to the surface layer 82 By manufacturing the optical sheet 80 while changing the additive amount of the agent, a plurality of light guide plate prototypes having different bluing agent formulations and matting agent formulations are formed.

  Next, the difference between the two in the evaluation step S2 will be described. In the first embodiment, only the chromaticity uniformity of each of the plurality of light guide plate prototypes formed in the prototype forming step S1 is evaluated, whereas in the second embodiment, the plurality of light guide plate prototypes formed in the prototype forming step S1 are evaluated. Evaluate chromaticity uniformity and luminance uniformity of each prototype of light guide plate. Specifically, for a plurality of manufactured light guide plate prototypes, chromaticity distribution and the like are obtained by simulation or actual measurement to evaluate chromaticity uniformity. In the present embodiment, in addition to this, a luminance distribution or the like is acquired by simulation or actual measurement to evaluate the luminance uniformity.

  Next, the difference between the two in the determination step S3 will be described. In the first embodiment, only the bluing agent prescription for the light guide plate 30 is determined based on the chromaticity uniformity, whereas in the second embodiment, the blue color of the light guide plate 30 is determined based on the chromaticity uniformity and the luminance uniformity. Ingredient formulations and matting agent formulations are determined. Specifically, the chromaticity uniformity and luminance uniformity of each light guide plate prototype evaluated in the evaluation step S2 are compared with the target chromaticity uniformity and luminance uniformity, and desired chromaticity uniformity. The bluing agent formulation and matting agent formulation for obtaining a good degree of brightness and brightness uniformity, that is, the addition amount (concentration) of the bluing agent and matting agent to the resin forming the base layer 81 are determined.

  Next, the difference between them in the light guide plate forming step S4 will be described. In Embodiment 1, the light guide plate is formed based on the determined bluing agent prescription, whereas in Embodiment 2, the light guide plate is formed based on the determined bluing agent prescription and matting agent prescription. Is done. This point will be specifically described below.

  First, the same styrenic resin as prepared in the prototype molding step S1 and a styrenic resin to which a bluing agent and a matting agent are added so as to have the concentration determined in the determination step S3 are prepared. It is put into the first extruder 61 and the second extruder 62 of the optical sheet manufacturing apparatus 60 described above. Next, the resins charged in the first extruder 61 and the second extruder 62 are melt-kneaded and supplied to the die 63.

Next, the molten resin supplied from the first extruder 61 becomes the base layer 81 (see FIG. 3B), and the molten resin supplied from the second extruder 62 becomes the surface layer 82 (see FIG. 3B). ), The die 63 is used for coextrusion molding. The thickness t ₈₂ of the surface layer 82, co-extrusion molding is carried out so as to have the same thickness as when it is molded by the prototype molding step S1. This is the same as in the first embodiment.

  Also in the second embodiment, when the co-extruded resin is pressed and cooled by the pre-loading roll 66, the first pressing roll 67, and the second pressing roll 68, it is molded in the prototype molding step S1. Are transferred at the same transfer rate. And the optical sheet 80 used as the light-guide plate 30 of 2 types and 2 layers comprised by the base layer 81 and the surface layer 82 which are shown in FIG.3 (b) is obtained. Thereby, the light guide plate 30 that emits light of desired chromaticity uniformity and luminance uniformity is obtained.

  The effect of the manufacturing method of the light-guide plate 30 which concerns on 2nd Embodiment is demonstrated. According to the manufacturing method described above, the amount of the bluing agent added to the styrene resin forming the surface layer 82 (blueing agent formulation) and the amount of the matting agent added to the styrene resin forming the surface layer 82 (matting agent) A plurality of light guide plate prototypes having different chromaticity uniformity and luminance uniformity of the emitted light are prepared. By evaluating the chromaticity uniformity and luminance uniformity based on the chromaticity distribution and luminance distribution obtained from these light guide plate prototypes, the concentration of the bluing agent that easily achieves the desired chromaticity uniformity, and the desired It is possible to determine the concentration of the matting agent that results in the luminance uniformity of. As described above, the light guide plate 30 having desired chromaticity uniformity and luminance uniformity can be efficiently manufactured.

  Furthermore, according to the manufacturing method described above, in order to prepare a plurality of light guide plate prototypes that emit light of different chromaticity uniformity and brightness uniformity, a prototype transfer die 69 having different uneven shapes is produced. There is no need to do. In addition, according to the second embodiment, the light guide plate 30 from which light having a desired luminance uniformity and peak angle is emitted using the transfer die 69 used when forming the light guide plate prototype is used as it is. Since it is manufactured, it is not necessary to prepare a new transfer die 69 for manufacturing the light guide plate. As described above, the light guide plate 30 from which light having a desired chromaticity / luminance uniformity and luminance uniformity is emitted can be manufactured more efficiently and at low cost.

  It was confirmed that the luminance uniformity of the light emitted from the light guide plate 30 changes when the matting agent formulation of the light guide plate 30 is changed. Specifically, in the light guide plate 30 in which the ridge portions 34 are arranged so that the luminance uniformity of the light emitted from the emission surface 30b is equal to or greater than a predetermined value, the light is incident from one side surface and the surface layer The emission intensity distribution when the addition amount (concentration) of the matting agent to the resin forming 32 was changed in various ways was calculated by simulation. According to this, it was confirmed that when the addition amount of the matting agent was increased, the emission intensity was higher in the region closer to the light source (incident surface 30c), and the emission intensity was lower in the region farther from the light source. Thus, it was confirmed that the brightness uniformity of the light emitted from the light guide plate 30 can be adjusted by changing the matting agent formulation of the light guide plate 30. Further, when light is incident from each of the two side surfaces facing each other, if the addition amount of the matting agent is increased, the emission intensity becomes higher in the region closer to the light source (incident surface 30c), and the region farther from the light source It was confirmed that the emission intensity was lower as the center of the light guide plate was lower.

Next, the following experimental example shows that the chromaticity uniformity can be adjusted by adding a bluing agent to the light guide plate 30 manufactured by the light guide plate manufacturing method of the present embodiment, that is, the surface layer 82. It demonstrates based on 1-3. However, the light guide plate manufactured by the manufacturing method of the present invention and the light guide plate of the present invention are not limited to these experimental examples. Hereinafter, for convenience of explanation, the components corresponding to the components shown in FIG. 1, described are denoted by the M as a light guide plate 30 _M.

(Experimental example 1)
In Experimental Example 1, as shown in FIG. 6, a light guide plate 30 _{M in} which the length W1 in the long side direction (X-axis direction) is 590 mm and the length W2 in the short side direction (Y-axis direction) is 240 mm. Got ready. Then, the light guide plate 30 _M was placed on a horizontal plane, the point-like light source 21 _M at a position opposed to one side of the short side of the light guide plate 30 _M arranged, rear 30 M _a side of the light guide plate 30 _M to the white reflector 25 _M arranged, on the exit surface 30 M _b side of the light guide plate 30 _M, in order from the outgoing surface 30 M _b side, the first prism film, in a stacked state of the second prism film and the diffusion film The chromaticity and luminance of the light emitted from the diffusion film were measured, and the chromaticity difference (chromaticity uniformity) and luminance uniformity in the X-axis direction were calculated. The measurement of chromaticity and luminance was performed from a point 2 m directly above the diffusion film using a luminance meter (Eye Scale Co., Ltd .: EyeScale 3).

The point light source 21 _M is mounted on a 46-inch size backlight unit, and the distance L between adjacent light sources is 8 mm (in FIG. 6, for convenience, the two point light sources 21 _M Only shows). Also, the point light sources 21 _M, the width of one light source 6 mm, is 2mm height. Figure 7 is a view showing an example of directional characteristics of the point light source 21 _M (light distribution characteristics). The horizontal axis in FIG. 7 indicates the outgoing angle θ ₂₁ (°), and the vertical axis indicates the normalized outgoing light intensity normalized by the maximum outgoing light intensity. In the present embodiment, θ ₂₁ = 0 corresponds to the X-axis direction in FIG. The point light sources 21 _M assumes the so-called Lambertian (Lambertian) type light source, examples of the point light source 21 _M, include light emitting diodes. The Lambertian type light source has a maximum output light intensity at which the output light intensity is maximum, and the output angle is around 0 ° (front direction), and decreases substantially monotonically as the inclination from the front direction (output angle) increases. It has the feature of going. PD in FIG. 7 shows the directivity characteristics when theoretical perfect diffusion, employing a point-like light source 21 _M where this characteristic is obtained in this experimental example.

First prism film, one surface with the prism portion extending to the incident surface 30 M _c in a direction parallel to the light guide plate 30 _M in (exit surface) are arranged in parallel, a direction orthogonal to the extending direction The prism part is arranged in parallel. The first prism film had an interval (pitch) between adjacent prism portions of 50 μm and an apex angle of 90 °. Moreover, the 1st prism film was comprised from PET (polyethylene terephthalate), and the refractive index was 1.58.

The second prismatic film serves to extend on one side direction perpendicular to the incident plane 30 M _c of the light guide plate 30 _M in (emission surface), the prism portion in the direction perpendicular to the extending direction are arranged parallel It is a film. The second prism film had an interval (pitch) between adjacent prism portions of 50 μm and an apex angle of 90 °. Moreover, the 2nd prism film was comprised from PET (polyethylene terephthalate), and the refractive index was 1.58.

  The diffusion film is a film having a diffusion performance capable of diffusing and emitting incident light. The total light transmittance Tt of the diffusion film was 93.6%, the diffusion transmittance Td was 90.2%, and the haze Haze was 96.4%.

Next, a description will be given chromaticity difference and luminance uniformity ratio light guide plate 30 for which to calculate the _M. The material of the light guide plate 30 _M is the base layer 31 _M, with a surface layer 32 _M, and the ridges 34 _M, both polystyrene (PS) (refractive index: 1.59) is. The surface layer 32 _M having a thickness of 100 μm is added with the bluing agent shown below so that the weight concentration becomes 1.0 ppm, and the matting agent shown below so that the weight concentration becomes 2.80%. Added.
(Bluing agent)
Macrolex Blue RR (Bayer, product name)
(Matting agent)
SBX-30 (Sekisui Plastics Co., Ltd., trade name)
Particle material: Polystyrene (PS) (refractive index 1.59), average particle size: 30 μm

Next, the convex portion 34 _M is formed on the exit surface 30 _M b side of the light guide plate 30 _M will be described. Arrangement of ridges 34 _M is a layout of the light-guiding plate used in the surface light source device of one side light incident type, as shown in FIG. 6, the convex portion 34 _M as the distance from the incident surface 30 M _c It arrange | positions so that a coverage may become large. Ridges 34 _M of the light guide plate 30 _M is contour of the cross-section perpendicular to the extending direction is represented by conic v (u) represented by the formula (1), the recess having a shape shown in FIG. 8 69 Molding is performed by transfer from transfer mold 69 _M on which _M a is formed.

In Formula (1), w _a is the length of the recess 69 _M a in the u-axis direction and corresponds to the width of the recess 69 _M a (hereinafter also referred to as width w _a ). In the formula (1), h _a is the length of the v-axis direction in case of the shape shown a recess 69 M _a in v (u), corresponding to the height of the recess 69 M _a (hereinafter, the height h _a ). In the formula (1), k _a is a parameter indicating the pointed how conic represents the pointed how the distal end portion of the recess 69 M _a which is formed on the transfer-type 69 _M (hereinafter, kurtosis k _a both Called). For example kurtosis when _{k a} is 0, the outer shape of the recess 69 _M a becomes parabolic, when kurtosis _{k a} is 1, the outer shape of the recess 69 _M a becomes prism shape, when kurtosis _{k a} is -1 , the outer shape of the recess 69 M _a is a shape cut in half an ellipse.

Transfer mold 69 _M gradually shape of the recess 69 M _a is increased up to a predetermined position at the same pitch along the circumferential direction, pitch gradual recess 69 M _a constant shape from the predetermined position It is formed to be shorter. When indicating the size of the shape of the recess 69 M _a in depth h _a, becomes as shown in FIG. In other words, gradually deeper depth h _a recess 69 M _a is to a predetermined position along the circumferential direction, are formed such that the depth h _a recess 69 M _a is constant from the predetermined position ing. At this time, the shapes of the minimum recess 69 _M a and the maximum recess 69 _M a are represented by the width w _a , the height h _a and the sharpness k _a as follows. Incidentally, AR and show the aspect ratio indicates the ratio of the maximum height h _a to the width w _a.
Maximum k _amax = 0.550, AR _max = 0.060, w _amax = 200 μm
Minimum k _amin = 0.834, AR _min = 0.022, w _amin = 35.8 μm

FIG. 10 shows the coverage distribution of the recess 69 _M a in the circumferential direction of the transfer mold 69 _M in which the recess 69 _M a is thus formed. Then, the transfer-type 69 light guide plate 30 whose shape has been transferred from _{M M} (e.g., transcription factor 77%), convex portions 34 _M of coverage, as shown in FIG. 6, from the incident surface 30 _M c It is formed so as to increase as it moves away. In this experimental example, the way the light guide panel 30 _M manufactured chromaticity and brightness were measured, chromaticity difference and luminance uniformity ratio was calculated. The chromaticity measurement result is shown by a solid line in FIG. 11, and the luminance measurement result is shown by a solid line in FIG. Further, the chromaticity difference (ΔCIEx: difference between the maximum CIEx and the minimum CIEx) and the luminance uniformity obtained from these measurement results are shown in the chart of FIG.

Further, the light guide plate 30 _M, as in the case of measuring the brightness, visually from the point immediately above 2m diffusion film was subjected to a sensory evaluation for chromaticity unevenness. In light plate 30 _M guide in the case of Experimental Example 1, the chromaticity non-uniformity was not confirmed. Further, using the luminance meter, the chromaticity difference was measured from a point 2 m directly above the diffusion film. The results are shown in the chart of FIG.

(Experimental example 2)
Similarly to Experimental Example 1, the light guide plate manufactured as Experimental Example 2 was calculated for chromaticity difference and luminance uniformity and evaluated for chromaticity unevenness. Here, description of points common to Experimental Example 1 is omitted, and only different points will be described.

That is, the surface layer 32 _M having a thickness of 100 μm is different from the experimental example 1 in that the above bluing agent is added so that the weight concentration is 1.5 ppm. In addition, about the point to which the matting agent was added so that a weight concentration might be 2.80%, it treats as equivalent to Experimental Example 1 to which the matting agent was added so that it may become 3.00%, and there is no problem.

The measurement result of chromaticity is indicated by a broken line in FIG. 11, and the measurement result of luminance is indicated by a broken line in FIG. Further, the chromaticity difference and the luminance uniformity obtained from these measurement results are shown in the chart of FIG. Further, the light guide plate 30 _M, as in the case of measuring the brightness, visually from the point immediately above 2m diffusion film was subjected to a sensory evaluation for chromaticity unevenness. Even the light guide plate 30 _M in the case of Example 2, the chromaticity non-uniformity was not confirmed. Further, using the luminance meter, the chromaticity difference was measured from a point 2 m directly above the diffusion film. The results are shown in the chart of FIG.

(Experimental example 3)
Similar to Experimental Example 1, the light guide plate manufactured as Experimental Example 3 was calculated for chromaticity difference and luminance uniformity and evaluated for chromaticity unevenness. Here, description of points common to Experimental Example 1 is omitted, and only different points will be described.

That is, the surface layer 32 _M having a thickness of 100 μm is different from the experimental example 1 in that the bluing agent is not added. In addition, about the point to which the matting agent was added so that a weight concentration might be 2.80%, it treats as equivalent to Experimental Example 1 to which the matting agent was added so that it may become 3.00%, and there is no problem.

The measurement result of this chromaticity is shown by a one-dot chain line in FIG. 11, and the measurement result of luminance is shown by a one-dot chain line in FIG. Further, the chromaticity difference and the luminance uniformity obtained from these measurement results are shown in the chart of FIG. Further, the light guide plate 30 _M, as in the case of measuring the brightness, visually from the point immediately above 2m diffusion film was subjected to a sensory evaluation for chromaticity unevenness. In light plate 30 _M guide in the case of Experimental Example 3, the light emitted from the region far from the point light sources 21 _M can observed that a strong yellowish compared to light emitted from a region close to the point light source 21 _M A difference in yellowness (unevenness in chromaticity) was observed between the light emitted from both. Further, using the luminance meter, the chromaticity difference was measured from a point 2 m directly above the diffusion film. The results are shown in the chart of FIG.

From the results of Experimental Example 1 to Experiment Example 3, when changing the bluing agent formulation of the light guide plate 30 _M, chromaticity uniformity ratio of light emitted from the light guide plate 30 _M was confirmed that change. According to this, as shown in FIG. 11, if increasing the amount of bluing agent, the effect of the yellow tint derived from the point light source 21 M _(incident surface 30 M _c) from farther regions styrene resin It was confirmed that it could be suppressed. Thus, by varying the bluing agent formulation of the light guide plate 30 _M, it can be adjusted chromaticity uniformity ratio of light emitted from the light guide plate 30 _M was confirmed.

Further, according to the results of Experiment Example 1 to Experiment Example 3, by adding a bluing agent to a resin for forming the light guide plate 30 _M, be able to adjust simultaneously the uniformity ratio of luminance and adjustment of chromaticity uniformity It could be confirmed. Thus, it was confirmed that the chromaticity uniformity can be adjusted within a range where the luminance uniformity does not decrease too much.

  As mentioned above, although one Embodiment and experiment example of this invention were demonstrated, this invention is not limited to the said embodiment and experiment example, A various change is possible in the range which does not deviate from the meaning of invention.

  In the above embodiment, in the prototype forming step S1, a matting agent having a predetermined concentration is added to the resin sheet so that the luminance uniformity when transferred at a predetermined transfer rate is a predetermined value or more. As explained. Examples of a method for adjusting the amount of the matting agent added include the following methods. That is, a step of forming a plurality of light guide plate prototypes by transferring the shape of the transfer mold 69 to resin sheets having different matting agent formulations, and brightness uniformity of each of the plurality of light guide plate prototypes A step of determining a matting agent prescription for providing a light guide plate that emits light of a desired luminance uniformity based on the evaluated luminance uniformity, and based on the determined matting agent prescription Forming the light guide plate. According to this method, by changing the matting agent formulation of the light guide plate, a plurality of light guide plate prototypes having different brightness uniformity are formed, and in order to prepare such a light guide plate prototype, There is no need to make a new transfer mold for different prototypes. Therefore, the addition amount of the matting agent can be adjusted more efficiently and at low cost.

  In the first embodiment, the chromaticity uniformity is evaluated in the evaluation step, and the example of determining the bluing agent prescription based on the chromaticity uniformity is described. However, the present invention is limited to this. It is not something. For example, the luminance uniformity may be further evaluated in the evaluation step, and the bluing agent prescription may be determined based on the chromaticity uniformity and the luminance uniformity. In this case, not only the chromaticity uniformity but also the luminance uniformity can be adjusted efficiently and at low cost, and a high-quality light guide plate can be provided.

  In the above embodiment, as the matting agent formulation, the method of adding the matting agent so as to have a predetermined concentration with respect to the resin forming the surface layer 82 has been described as an example, but the present invention is limited to this. It is not a thing. For example, the matting agent may be formulated by adjusting the temperature at which the surface layer 82 to which the matting agent is added leaves the second pressing roll 68 having the transfer die 69 provided on the peripheral surface. In this method, the matting agent floats on the surface as the temperature increases, and the surface roughness increases, so that the diffusion strength can be increased. In addition, as a matting agent formulation, not only the amount of matting agent added can be adjusted, but also the refractive index and particle size can be adjusted by changing the type of matting agent.

  Further, in the above embodiment, by transferring the shape of the transfer mold at a predetermined transfer rate to the resin sheets having at least different bluing agent prescriptions, at least the bluing agent prescription is different and the same uneven shape is obtained. Although the example which the some light-guide plate prototype which has is demonstrated was given and demonstrated, this invention is not limited to this. For example, a plurality of light guide plate prototypes in which at least the bluing agent prescription and the concavo-convex shape are different from each other by transferring the shape of the transfer mold at a different transfer rate to a resin sheet having at least a different bluing agent prescription. May be molded.

  In this case, in the evaluation step S2, the chromaticity uniformity, the luminance uniformity, and the peak angle of each of the plurality of light guide plate prototypes molded in the prototype molding step S1 are evaluated. In the determination step S3, the bluing agent prescription, matting agent prescription and uneven shape of the light guide plate 30 are determined based on the chromaticity uniformity and the luminance uniformity. In the light guide plate forming step S4, in the second embodiment, the light guide plate is formed based on the determined bluing agent prescription, matting agent prescription and uneven shape.

  Here, the transfer rate will be described. FIGS. 5A to 5C are schematic views showing an embodiment of the step of forming the optical sheet 80 as the light guide plate 30 (the same applies to the light guide plate prototype). As shown in FIG. 5A, a recess 69 a having a depth h <b> 1 corresponding to the shape of the ridge 84 forming the concavo-convex shape of the optical sheet 80 is formed on the peripheral surface of the transfer mold 69. As shown in FIG. 5B, the resin sheet 70 is pressed to fill the recess 69a with resin. The height h2 of the ridge 84 formed in the recess 69a in a state where the resin is in close contact with the transfer mold 69 is smaller than the maximum depth h1, and a gap is left between the resin and the transfer mold 69. . The resin may be completely filled in the recess 69a, and h1 = h2. After the resin temperature has dropped to some extent, the resin sheet 70 is removed from the transfer mold 69. Thereafter, since the resin shrinks due to thermoelastic deformation, the height h3 of the protruding portion 84 of the resin sheet 70 (optical sheet 80) in a state where the resin is solidified becomes smaller than the height h2. Even when the filling rate (h2 / h1) is small, the shape of the bottom part of the final protrusion 84 often accurately reflects the shape of the transfer die 69.

  The transfer rate (%) can be defined as a value calculated by the formula: (h3 / h1) × 100. By changing the transfer rate within a range of 25 to 100%, for example, a plurality of types of light guide plates (light guide plate prototypes) having various uneven shapes can be easily and quickly produced from one type of transfer mold. can do.

  As understood by those skilled in the art, the transfer rate of the shape from the transfer mold can be controlled by appropriately adjusting the molding conditions of the optical sheet. For example, there is a method of setting conditions by paying attention to the filling rate (h2 / h1) of the resin into the transfer type recess 69a. In this method, for example, when the temperature of the resin discharged from the die is increased, when the line speed is increased, when the melt bank is reduced, or when the temperature of the pressure roll having the transfer mold is increased, the filling is performed. Since the fluidity of the resin during printing increases, the transfer rate tends to increase. Or you may set conditions, such as roll temperature and a line speed, paying attention to the extent (h3 / h2) of the thermoelastic deformation of resin after mold release.

  Furthermore, according to this manufacturing method, the uneven shape can be changed by changing the transfer rate of the shape from the transfer die 69, so that the peak angle of the emitted light is adjusted in addition to the chromaticity uniformity and the brightness uniformity. Will be able to. Accordingly, the light guide plate 30 from which light is emitted at a desired chromaticity uniformity, luminance uniformity, and peak angle can be manufactured more efficiently and at a low cost, and the light guide plate 30 can be manufactured on the emission side of the light guide plate 30. The optimal light guide plate 30 matched with the characteristic of the optical member arrange | positioned can be manufactured.

  In the light guide plate forming step S4 of this manufacturing method, the resin sheet formulated with the bluing agent determined in the determining step S3 is transferred at a transfer rate corresponding to the uneven shape determined in the determining step S3. The light plate 30 can be formed.

  Further, for example, in the light guide plate forming step S4, a light guide plate manufacturing transfer mold having an inverted shape corresponding to the uneven shape determined in the determination step S3 is prepared, and the bluing agent prescription and the mat determined in the determination step S3 are prepared. The light guide plate 30 may be formed by transferring the light guide plate manufacturing transfer mold to the resin sheet on which the agent is formulated. At this time, the transfer mold for manufacturing the light guide plate may have a shape that becomes the uneven shape determined in the determination step S3 when the transfer mold is transferred at a transfer rate of 25% or more and 90% or less. Also, if the transfer mold for manufacturing the light guide plate is formed to have the uneven shape determined in the determination step S3 when transferred at a transfer rate of 25% or more and 65% or less, the line speed is relatively increased. Even if it is set to, a desired shape can be acquired stably.

  Further, for example, as shown in FIG. 14, a confirmation step S31 for finding a stable transfer rate when the line speed is increased to a predetermined speed using the transfer mold 69 used in the prototype forming step S1 is determined. It may be further included between step S3 and light guide plate forming step S4. In this case, in the light guide plate forming step S4, the light guide plate 30 is transferred by transferring the transfer mold for manufacturing the light guide plate so that the uneven shape determined in the determination step S3 is obtained at the transfer rate found in the confirmation step S31. You may make it shape | mold. At this time, as the transfer rate having the above-described stability, a transfer rate of 25% to 90%, preferably 25% to 65% may be set.

  It was confirmed that the brightness uniformity of the light emitted from the light guide plate 30 changes when the transfer rate of the shape from the transfer die 69 at the time of molding is changed. Specifically, a transfer die 69 having a concave portion 69a corresponding to the arrangement of the convex portion 34 such that the luminance uniformity of the light emitted from the emission surface 30b is equal to or greater than a predetermined value is prepared, and the transfer die at the time of molding is prepared. While changing the transfer rate of the shape from 69 variously, that is, changing the shape of the ridges 34 formed on the light guide plate 30, a plurality of light guide plates are manufactured, and the light emitted from these light guide plates The change of the brightness uniformity of was confirmed by simulation. According to this, it was confirmed that when the transfer rate was increased, the emission intensity was higher in the region closer to the light source (incident surface 30c), and the emission intensity was lower in the region farther from the light source. It was confirmed that the same result was obtained when light was incident from each of the two side surfaces facing each other. In addition, when light is incident from each of the two side surfaces facing each other, if the transfer rate is increased, the region closer to the light source (incident surface 30c) has higher emission intensity, and the region farther from the light source (light guide plate) It was confirmed that the emission intensity was lower in the middle part.

  Furthermore, in the above case, it was confirmed that the radiation intensity of the light emitted from the light guide plate 30 was changed and the peak angle was also changed. To adjust the brightness uniformity, there are a method using a matting agent formulation, a method using a bluing agent formulation, a method using a diffusing agent formulation, a method of adjusting the transfer rate, etc., but the brightness uniformity can be adjusted by adjusting the transfer rate. It was confirmed that the peak angle of the light emitted from the light guide plate 30 can be adjusted simultaneously.

  In the prototype forming step S1 of the above embodiment, a plurality of light guide plate prototypes having different blueing agent prescriptions or a plurality of light guide plates having different blueing agent prescriptions and matting agent prescriptions at a time. Although an example in which a prototype or a plurality of light guide plate prototypes having different concavo-convex shapes is formed with different bluing agent prescription and matting agent prescription has been described, the present invention is limited to this Is not to be done.

  For example, in the first embodiment, one prototype of a light guide plate with a predetermined bluing agent prescription is formed in the prototype molding step S1, and after evaluating the light guide plate prototype in the evaluation step S2, It also includes molding a light guide plate prototype with a different bluing agent formulation from the previous light guide plate prototype. In this case, the prototype forming step S1 and the evaluation step S2 are repeated until a desired chromaticity uniformity is obtained.

  Further, for example, when a plurality of light guide plate prototypes having different concavo-convex shapes are formed with different bluing agent prescriptions and matting agent prescriptions, a predetermined bluing is performed in the prototype forming step S1. After forming a light guide plate prototype that has been formulated with an agent and a matting agent and transferred at a predetermined transfer rate, and after evaluating the light guide plate prototype in the evaluation step S2, Molding a light guide plate prototype transferred at the same transfer rate to a resin with a different bluing agent formulation and matting agent formulation, or a predetermined bluing agent different from the previous light guide plate prototype It also includes molding light guide plate prototypes transferred at different transfer rates with respect to a resin having a prescription and a matting agent prescription. In this case, the prototype forming step S1 and the evaluation step S2 are repeated until the desired chromaticity uniformity, luminance uniformity, and peak angle are obtained.

  Even in the two other embodiments as described above, a plurality of light guide plate prototypes will be formed, and in the determination step S3, at least based on the evaluation results of the plurality of light guide plate prototypes. The bluing agent prescription will be determined.

  Moreover, in the said 1st Embodiment, 2nd Embodiment, and the said other embodiment mentioned above, the resin sheet 70 in prototype shaping | molding step S1 is made | formed further by the diffusing agent, In decision step S3, Based on the evaluated brightness uniformity, a diffusing agent prescription for making the light guide plate 30 that emits light having a desired brightness uniformity is further determined. In the light guide plate forming step S4, the diffusing agent prescription is further determined. The light guide plate 30 may be formed. According to this manufacturing method, by performing the diffusing agent formulation to such an extent that chromaticity nonuniformity does not occur, it is possible to deal with the brightness uniformity with high accuracy that cannot be dealt with by adjusting the bluing agent formulation, matting agent formulation and transfer rate. Can be adjusted.

  Note that the diffusing agent formulation may be performed by adjusting the amount of the diffusing agent added. Moreover, when the light guide plate is constituted by a plurality of layers including a diffusion layer to which a diffusion agent is added, the diffusion agent prescription may be performed by adjusting the thickness of the diffusion layer.

  In the said embodiment, although polystyrene was mentioned as an example and demonstrated as a styrene resin which is a main component of the base layer 31 and the surface layer 32, it should just be resin containing a styrene monomer unit. For example, the base layer 31 and the surface layer 32 may each be a resin in which a styrene monomer and a (meth) acrylic acid ester are copolymerized. In the present invention, methacrylic acid ester and acrylic acid ester are collectively referred to as (meth) acrylic acid ester.

  In the form in which the main component of the base layer 31 and the surface layer 32 is a resin in which a styrene monomer and a (meth) acrylate ester are copolymerized, the amount of the styrene monomer unit is the (meth) acrylate unit. More than the amount. That is, the resin constituting the base layer 31 and the surface layer 32 has a styrene monomer unit content of 50% by mass to 100% by mass and a (meth) acrylic acid ester unit content of 0% by mass to 50% by mass. % Resin is preferred. Since such a styrene-based resin is derived from a styrene-based monomer unit or is likely to have a yellowish color, the present invention is preferably applied. Examples of the resin in which such a styrene monomer and a (meth) acrylic acid ester monomer are copolymerized include MS resin in which styrene and methyl methacrylate are copolymerized.

  As the styrene monomer, substituted styrene or the like can be used in addition to styrene. Examples of the substituted styrene include halogenated styrene such as chlorostyrene and bromostyrene, and alkylstyrene such as vinyltoluene and α-methylstyrene. Examples of (meth) acrylic acid esters include, in addition to methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate. And methacrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate. .

  As the main component of the base layer 31 and the surface layer 32, polycarbonate (PC) resin can also be used. Polycarbonate resin is excellent in heat resistance. Therefore, heat resistance can be imparted to the base layer 31 and the surface layer 32. The molding temperature of the light guide plate base material portion 33 can be appropriately set according to the polycarbonate resin to be used, and is, for example, 260 to 320 ° C. Examples of the polycarbonate resin include Iupilon (model number: H-3000, H-4000, HL-4000, HL-7001, HL-8000) manufactured by Mitsubishi Engineering Plastics, and Macrolon (model number: 2205, 2405) manufactured by Bayer. CD2605), Teflon (model number: # 1700, # 1900, # 2200) manufactured by Idemitsu Kosan Co., Ltd., Panlite (model number: L-1225L, L-1225-Y, LV-2225Y) manufactured by Teijin Chemicals Ltd., ST-3000 manufactured by Teijin Bayer Polytech Co., Ltd., Lexan manufactured by GE Plastics (model number: 101R, 103R, 153R) and Caliber manufactured by Sumitomo Dow Co., Ltd. (model numbers: 301-15, 301-22, 301-30) Is mentioned.

  In the said embodiment, although the example in which a bluing agent was added to the surface layer 32 was given and demonstrated, this invention is not limited to this, For example, you may add to the base layer 31. Moreover, when the light-guide plate 30 is a multilayer structure, the bluing agent should just be added to at least any one layer.

  In the above-described embodiment, the transfer from the transfer mold in which the concave portion 69a having the same shape tip portion is formed has been described as an example. However, the present invention is not limited to this. It is only necessary to use a transfer mold having a concave portion in which a convex stripe portion capable of ensuring a predetermined luminance uniformity is formed, and the shape of the concave portion is not limited, and the arrangement method of the concave portion is not limited. .

  In the embodiment described above, a one-dimensional lenticular lens extending in one direction has been described as an example of the shape of the light guide plate prototype and the light guide plate, but the shape is not limited thereto. For example, the cross-sectional shape in the extending direction may be a triangular shape, or a two-dimensional uneven shape such as a microlens or a pyramid prism.

  In the embodiment shown in FIG. 5, the recess 69a of the transfer mold 69 has a mountain shape in cross section, but the shape of the transfer mold is not limited to this. For example, a transfer mold having a recess whose cross-sectional shape is a triangular prism shape can be suitably used. By using a plurality of types of transfer molds having different triangular prism base angles, various prototypes having different optical characteristics can be easily produced in a short period of time.

  As an embodiment of the light guide plate manufactured by the above method for manufacturing a light guide plate, a surface light source device having a configuration in which one side surface 30c among four side surfaces 30c to 30f as shown in FIG. Although described above, the present invention is not limited to this. For example, the surface light source device may be configured such that two side surfaces 30c and 30d facing each other serve as a light incident surface. In this case, the ridges 34 can be arranged denser as the position is farther from the light source unit 21 along the arrangement direction. That is, it is possible to obtain a coverage distribution in which the coverage of the ridges 34 is higher at positions farther from the light source unit 21 along the arrangement direction (central portion of the light guide plate 30). The coverage here refers to the ratio of the ridges 34 to the main surface 30a on which the ridges 34 are formed in a plan view. For example, when each protruding line part 34 has substantially the same shape, the coverage can be adjusted by changing the interval between the protruding line parts 34.

  In the said embodiment, although the extrusion molding method was mentioned as an example and demonstrated as a light-guide plate prototype and the shaping | molding method of a light-guide plate, this invention is not limited to this. For example, the light guide plate prototype and the light guide plate forming method may be compatible with other forming methods such as injection molding and hot press molding.

  DESCRIPTION OF SYMBOLS 1 ... Transmission type image display apparatus, 10 ... Transmission type image display part, 11 ... Liquid crystal cell, 12, 13 ... Polarizing plate, 20 ... Surface light source device, 21 ... Light source part, 25 ... Reflection sheet, 30 ... Light guide plate, 30a ... Main surface (back surface), 30b ... Main surface (outgoing surface), 30c ... Side surface (incident surface), 30d to 30f ... Side surface, 31 ... Base layer, 32 ... Surface layer, 33 ... Light guide plate base material portion, 34 ... Projections 40: Various optical films, 60: Optical sheet manufacturing apparatus, 61 ... First extruder, 62 ... Second extruder, 63 ... Die, 66 ... Preload roll, 67 ... First press roll, 68 ... Second press Roll, 69 ... transfer mold, 69a ... concave, 70 ... resin sheet, 80 ... optical sheet, 81 ... base layer, 82 ... surface layer, 84 ... projection strip, S1 ... prototype forming step, S2 ... evaluation step, S3 ... decision Step, S31: Confirmation step, S4: Light guide plate forming step -Up.

Claims (17)

Multiple light guide plate prototypes by transferring the shape of the transfer mold to a resin sheet made of styrene-based resin or polycarbonate resin with different bluing agent formulations by adjusting the amount of blueing agent added Prototype molding step to mold,
An evaluation step for evaluating the chromaticity uniformity of each of the plurality of light guide plate prototypes,
A determination step of determining an amount of a bluing agent added to form a light guide plate that emits light of a desired chromaticity uniformity based on the evaluated chromaticity uniformity;
A light guide plate forming step for forming the light guide plate based on the determined amount of bluing agent added;
A method for manufacturing a light guide plate, comprising: In the evaluation step, the brightness uniformity of each of the plurality of light guide plate prototypes is further evaluated,
In the determining step, an addition amount of a bluing agent for forming a light guide plate that emits light of desired chromaticity uniformity and luminance uniformity is determined based on the evaluated chromaticity uniformity and luminance uniformity. ,
The manufacturing method of the light-guide plate of Claim 1. The resin sheet in the prototype molding step is further made a different matting agent formulation,
In the determining step, based on the evaluated brightness uniformity, further determining a matting agent prescription for a light guide plate that emits light of a desired brightness uniformity,
In the light guide plate forming step, the light guide plate is further formed based on the determined matting agent prescription.
The manufacturing method of the light-guide plate of Claim 2. The matting agent formulation is performed by adjusting the amount of matting agent added,
The manufacturing method of the light-guide plate of Claim 3. The matting agent formulation is performed by adjusting the temperature at which the layer to which the matting agent is added leaves the transfer mold,
The manufacturing method of the light-guide plate of Claim 3 or 4. The matting agent has a particle component having the same refractive index as that of the styrene resin or the polycarbonate resin to which the matting agent is added, or a difference in refractive index from the styrene resin or the polycarbonate resin is 0.01. The following particle components:
The manufacturing method of the light-guide plate as described in any one of Claims 3-5. In the prototype molding step, the shape of the transfer mold is transferred at a predetermined transfer rate to the resin sheet having the different bluing agent formulation and the matting agent formulation.
The manufacturing method of the light-guide plate as described in any one of Claims 3-6. In the light guide plate molding step, the transfer sheet used in the prototype molding step is added to the resin sheet to which the determined amount of the bluing agent is added and the matting agent formulation is determined. Forming the light guide plate by transferring the shape at the same transfer rate as when transferred in the prototype forming step;
The manufacturing method of the light-guide plate of Claim 7. In the prototype molding step, different concavo-convex shapes are formed by transferring the shape of the transfer mold at different transfer rates when transferring the shape of the transfer mold,
In the evaluation step, further evaluate the peak angle of each of the plurality of light guide plate prototypes,
In the determining step, based on the evaluated peak angle, further determining a concavo-convex shape for a light guide plate that emits light having a desired luminance uniformity and peak angle,
In the light guide plate forming step, the light guide plate is further formed based on the determined uneven shape,
The manufacturing method of the light-guide plate as described in any one of Claims 3-6. In the light guide plate molding step, the transfer sheet used in the prototype molding step is added to the resin sheet to which the determined amount of the bluing agent is added and the matting agent formulation is determined. Forming the light guide plate by transferring the shape at a transfer rate corresponding to the determined uneven shape;
The manufacturing method of the light-guide plate of Claim 9. In the light guide plate forming step, an inverted shape corresponding to the determined uneven shape is applied to the resin sheet to which the determined amount of the bluing agent is added and the matting agent is determined. Forming the light guide plate by transferring a transfer mold for producing the light guide plate,
The manufacturing method of the light-guide plate of Claim 9. The light guide plate manufacturing transfer mold has a shape that becomes the determined uneven shape when transferred at a transfer rate of 25% or more and 90% or less with respect to the resin sheet.
The manufacturing method of the light-guide plate of Claim 11. The method further includes a confirmation step of finding a transfer rate having stability when the line speed is increased to a predetermined speed using the transfer mold used in the prototype molding step,
In the light guide plate forming step, the determined concavo-convex shape is found in the confirmation step with respect to the resin sheet to which the determined amount of the bluing agent is added and the determined matting agent is formulated. Molding the light guide plate by transferring a transfer mold for producing a light guide plate having a shape that can be obtained at the transferred transfer rate,
The manufacturing method of the light-guide plate as described in any one of Claims 9-12. The transfer rate having the stability is 25% or more and 90% or less,
The manufacturing method of the light-guide plate of Claim 13. The resin sheet in the prototype molding step is further subjected to a diffusing agent prescription,
In the determining step, based on the evaluated brightness uniformity, further determine a diffusing agent prescription for a light guide plate that emits light of a desired brightness uniformity,
In the light guide plate forming step, the light guide plate is further formed based on the determined diffusing agent prescription.
The manufacturing method of the light-guide plate as described in any one of Claims 1-14. A light guide plate substrate portion having an exit surface for emitting light and a back surface opposite to the exit surface;
Provided on the back side of the light guide plate base material part, and a reflection part for reflecting light on the emission surface side;
With
The light guide plate base material portion is formed of a styrene resin or a polycarbonate resin containing a bluing agent,
The outermost layer on the light emitting surface side in the light guide plate base material portion contains a matting agent for forming an uneven surface for diffusing light on the light emitting surface.
Light guide plate. The matting agent is a particle component having the same refractive index as the styrene resin or the polycarbonate resin, or a particle component having a refractive index difference of 0.01 or less from the styrene resin or the polycarbonate resin.
The light guide plate according to claim 16.

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