JP2013166269A - Method for manufacturing light guide plate - Google Patents

Abstract

A light guide plate manufacturing method capable of manufacturing a light guide plate having a desired luminance uniformity more efficiently and at a low cost.
A light guide plate manufacturing method includes: a prototype forming step S1 for forming a plurality of light guide plate prototypes by transferring the shape of a transfer mold 69 to resin sheets having different diffusing agent formulations; Evaluation step S2 for evaluating the brightness uniformity of each of the plurality of light guide plate prototypes, and a determination step for determining the diffusion intensity for obtaining the light guide plate 30 having a desired brightness uniformity based on the evaluated brightness uniformity S3 and light guide plate forming step S4 for forming the light guide plate 30 based on the determined diffusing agent prescription.
[Selection] Figure 4

Description

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

  2. Description of the Related Art A transmissive image display device such as a liquid crystal display device generally includes a surface light source device that is disposed on the back side of a transmissive image display unit such as a liquid crystal display panel and supplies a backlight to the transmissive image display unit. As such a surface light source device, an edge light type surface light source device is known.

  The edge light type surface light source device includes a light-transmitting light guide plate and a light source that is disposed on the side of the light guide plate and supplies light to the side surface of the light guide plate. Such a light guide plate may have a concavo-convex shape on its surface so that light with a desired luminance uniformity is emitted. As a method of manufacturing an optical sheet having an uneven shape, a method of transferring a transfer mold shape onto the surface of a continuous resin sheet is known (for example, Patent Document 1).

JP 2009-220555 A

  In such a light guide plate, in order to obtain a desired brightness uniformity, in general, a concavo-convex shape is designed by simulation, a prototype having the designed concavo-convex shape is produced, and the brightness uniformity in the prototype is As a result of the evaluation, the uneven shape is optimized. In order to obtain a light guide plate from which light having a desired luminance uniformity is emitted, it is necessary to precisely adjust the uneven shape. For this reason, in order to optimize the concavo-convex shape, production of a prototype and evaluation of luminance uniformity in the prototype are often repeated on a trial and error basis.

  However, in such a conventional method, it is necessary to create a new transfer mold every time a prototype is produced, so that a light guide plate that emits light with a desired luminance uniformity is produced by optimizing the uneven shape. Therefore, the actual situation is that it requires a great deal of cost and time.

  Accordingly, a main object of the present invention is to provide a method of manufacturing a light guide plate capable of manufacturing a light guide plate having a desired luminance uniformity more efficiently and at low cost.

  The light guide plate manufacturing method according to the present invention includes a prototype molding step of molding a plurality of light guide plate prototypes by transferring the shape of a transfer mold to resin sheets having different diffusing agent formulations. Evaluation step for evaluating the brightness uniformity of each of the light guide plate prototypes, and a determination step for determining a diffusing agent prescription for the light guide plate that emits light of the desired brightness uniformity based on the evaluated brightness uniformity And a light guide plate forming step for forming the light guide plate based on the determined diffusing agent prescription.

  According to this manufacturing method, by preparing a plurality of light guide plate prototypes having different brightness uniformity by changing the diffusing agent formulation of the light guide plate, in order to prepare a light guide plate prototype, There is no need to make a new transfer mold. 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 resin sheet is composed of a plurality of layers including a diffusion layer to which a diffusing agent is added, and the diffusing agent prescription may be performed by adjusting the thickness of the diffusing layer. Good.

  In the method for manufacturing a light guide plate according to the present invention, the diffusing agent formulation may be performed by adjusting the amount of the diffusing agent added.

  In the method of manufacturing the light guide plate according to the present invention, the shape of the transfer mold may be transferred at a predetermined transfer rate to the resin sheets having different diffusing agent formulations in the prototype forming step.

  In the light guide plate manufacturing method according to the present invention, the diffusing agent prescription and the concavo-convex shape are obtained by transferring the shape of the transfer mold at different transfer rates to the resin sheets having different diffusing agent prescriptions in the prototype forming step. Forming a plurality of light guide plate prototypes different from each other, evaluating the brightness uniformity and the peak angle of each of the plurality of light guide plate prototypes in the evaluation step, and determining based on the evaluated brightness uniformity and the peak angle in the determination step. Then, a diffusing agent prescription and a concavo-convex shape for making a light guide plate that emits light having a desired luminance uniformity and peak angle are determined. A light plate can also be formed.

  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 luminance uniformity. . As a result, a light guide plate that emits light at a desired luminance uniformity and peak angle can be manufactured more efficiently and at low cost, and the characteristics of the optical member disposed on the light exit side of the light guide plate It is possible to manufacture an optimal light guide plate that is suitable for the above.

  In the light guide plate manufacturing method according to the present invention, in the light guide plate molding step, the shape of the transfer mold used in the prototype molding step is determined in the prototype molding step for the resin sheet having the determined diffusing agent prescription. The light guide plate can also be formed by transferring at the same transfer rate as when it was transferred.

  According to this manufacturing method, a light guide plate that emits light with a desired luminance uniformity is manufactured using the transfer mold used when forming the light guide plate prototype as it is. There is no need to prepare a new transfer mold. 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, the shape of the transfer mold used in the prototype molding step is determined for the resin sheet subjected to the determined diffusing agent formulation in the light guide plate molding step. The light guide plate can also be formed by transferring at a transfer rate corresponding to.

  According to this manufacturing method, a light guide plate that emits light having a desired luminance uniformity and peak angle 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 an optical plate. This makes it possible to manufacture a light guide plate from which light having a desired luminance uniformity and peak angle is emitted 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, a light guide plate manufacturing transfer mold having an inverted shape corresponding to the determined concavo-convex shape is applied to the resin sheet subjected to the determined diffusing agent prescription. The light guide plate can be formed by transferring.

  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 luminance uniformity and peak angle is emitted can be manufactured more efficiently and at low cost. It becomes possible to do.

  In the light guide plate manufacturing method according to the present invention, the light guide plate manufacturing transfer mold may have an inverted shape in which the uneven shape of the light guide plate is formed when transferred at a transfer rate of 90% or more. .

  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 light guide plate manufacturing transfer mold is transferred to the resin sheet having the determined diffusing agent formulation so that the determined uneven shape is obtained at the transfer rate found in the confirmation step. A light plate can be formed.

  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 inventors' diligent study. Therefore, using the transfer mold used in the prototype molding step, the transfer rate having stability is found when the line speed is increased to a predetermined speed, and the uneven shape determined by evaluating the luminance uniformity and peak angle is A transfer mold for manufacturing a light guide plate that can be obtained at a transfer rate is prepared, and a light guide plate is manufactured using the transfer mold for manufacturing the light guide plate. This makes it possible to manufacture a light guide plate from which light having a desired luminance uniformity and peak angle is emitted more efficiently and at low cost.

  In the method for manufacturing a light guide plate according to the present invention, the transfer rate having stability can be 50% or more and less than 90%.

  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 a desired brightness | luminance uniformity 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 a schematic block diagram which shows an example of the manufacturing apparatus which manufactures the optical sheet used as a light-guide plate, and is sectional drawing along the IIIb-IIIb line 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 showing a simulation model, and is an explanatory diagram for explaining a setting state of a local coordinate system on an emission surface and a method of defining angles from the c-axis and the a-axis in this coordinate system. It is drawing which shows an example of the directivity of the point light source in simulation. It is drawing which shows an example of the shape of a protruding item | line part. It is a graph which shows the result of simulation A. It is a graph which shows the result of simulation B. It is a schematic diagram which shows a simulation model. It is a graph which shows the result of simulation C. It is a graph which shows the result of simulation D. It is a schematic diagram which shows one Embodiment of the manufacturing method of an optical sheet. It is a graph which shows the result of simulation E. It is a graph which shows the result of the simulation F and the simulation G, respectively. It is a graph which shows the result of simulation H. It is a graph which shows the result of the simulation I and the simulation J, respectively. 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 pair of main surfaces 30a and 30b having a rectangular shape in plan view. The one main surface 30 a has a concavo-convex shape formed by a plurality of ridges 33. The ridge 33 extends in a direction along one side of the main surface 30 a, and the shape of the cross section orthogonal to the extending direction of the ridge 33 is a mountain shape. The cross-sectional shape orthogonal to the extending direction of the ridge 33 is almost uniform in any part in the extending direction. The concavo-convex shape having the ridges 33 is formed by transfer from the transfer die 69 (see FIG. 3A).

  The plurality of ridges 33 are arranged in parallel in a direction perpendicular to the extending direction, and each ridge 33 has substantially the same shape. The plurality of ridge portions 33 are arranged so as to have a predetermined luminance uniformity when used as the surface light source device 20 (see FIG. 2) described in detail later. For example, when the light source unit 21 is provided on two opposite sides as in the surface light source device 20, the protrusions 33 are arranged more densely as the position is farther from the light source unit 21 along the arrangement direction. Can do. That is, it is possible to obtain a coverage distribution in which the coverage of the ridges 33 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 means the ratio of the ridges 33 to the main surface 30a on which the ridges 33 are formed in plan view. For example, when each protruding item | line part 33 is substantially the same shape, a coverage can be adjusted by changing the space | interval of the protruding item | line parts 33. FIG.

  The light guide plate 30 is made of a translucent resin that transmits light and is formed in a plate shape. The light guide plate 30 has a two-type two-layer configuration including a base layer 31 and a diffusion layer 32 as shown in FIGS. 1 and 2. Examples of the translucent resin forming the light guide plate 30 include acrylic resin, styrene resin, carbonate resin, cyclic olefin resin, polystyrene resin, methyl methacrylate-styrene copolymer resin (MS resin), and polymethyl methacrylate resin. (PMMA resin) can be used.

  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 (SuperTwistedNematic) 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 located on the transmissive image display unit 10 side, and one main surface 30 a on which the ridge 33 is formed is located on the opposite side to the transmissive image display unit 10. To be arranged. In addition, the light guide plate 30 has a protrusion 33 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 30c, 30d. As a result, the light incident from the incident surfaces 30 c and 30 d of the light guide plate 30 is diffusely reflected by the ridge 33 and emitted from the other main surface (hereinafter also referred to as “exit surface”) 30 b.

  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 along the IIIb-IIIb line | wire of the optical sheet manufactured with the manufacturing apparatus shown to Fig.3 (a). 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 diffusion layer 82 (see FIG. 3). 3 (b)), a second extruder 62 for heating and melting the thermoplastic resin, and a die 63 for extruding the molten resin supplied from the first and second extruders 61 and 62 into a sheet shape, , A preload roll 66, a first pressing roll 67, and a second pressing roll 68 for forming the two-type two-layer sheet-like resin sheet 70 extruded from the 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 transfer mold 69 corresponding to the uneven shape of the light guide plate 30 is provided on the peripheral surface of the second pressing roll 68.

  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. In many cases, a melt bank 71 where molten resin stays is formed at a position where the resin sheet 70 enters between these rolls. 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 a ridge 83 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 molding step S1, a plurality of light guide plate prototypes are molded by transferring the shape of a transfer mold at a predetermined transfer rate to resin sheets having different diffusing agent formulations. As a result, a plurality of light guide plate prototypes having the same uneven shape and different diffusion agent prescriptions are formed. Specifically, a thermoplastic resin and a thermoplastic resin to which a diffusing agent is added so as to have a predetermined concentration are prepared, and the first extruder 61 and the second extruder 62 of the optical sheet manufacturing apparatus 60 described above are prepared. 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 diffusion layer 82 (FIG. 3B). (See FIG. 4), the die 63 is coextruded.

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. Thus, a two-type two-layer optical sheet 80 constituted by the base layer 81 and the diffusion layer 82 shown in FIG. 3B, that is, the light guide plate 30 is obtained. In the present embodiment, the thickness t ₈₀ of the entire optical sheet 80 is fixed by a plurality of times of molding is carried out while changing the thickness t ₈₂ of the diffusion layer 82, a plurality of electrically different spreading agent formulation is made together A light plate prototype is 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 a ratio of the height h1 of the groove of the transfer mold to the height h3 of the protrusion 83 formed by the transfer when the shape of the transfer mold 69 is transferred, and (h3 / h1) × 100. (See FIGS. 13A to 13C).

  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 the above-mentioned shape, and to cope with a concavo-convex shape that emits light having a desired brightness uniformity degree when transferred under predetermined conditions, which is determined by simulation A described below. Various transfer molds may be used.

  In the evaluation step S2, the luminance 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 that can grasp the change in output intensity in the arrangement direction (hereinafter also referred to as “output intensity distribution”), etc. are obtained by simulation or measurement, and the luminance uniformity To evaluate. The luminance uniformity can be, for example, a value obtained by dividing the minimum value of the emission intensity by the maximum value in the change of the emission intensity in the acquired arrangement direction.

  In the determination step S3, a diffusing agent prescription for manufacturing the light guide plate 30 that emits light having a desired luminance uniformity is determined based on the luminance uniformity evaluated in the evaluation step S2. Specifically, by comparing the brightness uniformity of each light guide plate prototype evaluated in the evaluation step S2 with the target brightness uniformity, a diffusing agent formulation for obtaining a desired brightness uniformity well, That is, the thickness of the diffusion layer 82 is determined.

  In the light guide plate forming step S4, the light guide plate is formed based on the diffusing agent prescription determined in the determining step S3. For example, when the light guide plate prototype is molded using the shape of the transfer mold used when the light guide plate prototype is molded with respect to the resin sheet having the diffusing agent prescription determined in the determination step S3. By transferring at the same transfer rate, an optical sheet serving as a light guide plate can be formed. This will be specifically described below.

  First, the same thermoplastic resin as prepared in the prototype forming step S1 and a thermoplastic resin to which a diffusing agent is added so as to have a predetermined concentration are prepared, and the first of the optical sheet manufacturing apparatus 60 described above is prepared. It is put into the extruder 61 and the second extruder 62, respectively. 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 diffusion layer 82 (FIG. 3B). The co-extrusion molding is performed by the die 63 so that The thickness t ₈₂ of the diffusion layer 82, to a thickness determined by the decision step S3 is co-extrusion is carried out. Then, the coextruded resin is pressed and cooled by the preloading roll 66, the first pressing roll 67, and the second pressing roll 68, whereby the base layer 81 and the diffusion layer shown in FIG. The optical sheet 80 which becomes the light guide plate 30 of two types and two layers constituted by 82 can be obtained. Thereby, the light guide plate 30 that emits light having a desired luminance 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 brightness uniformity levels are prepared by adjusting the thickness t ₈₂ (diffusion agent prescription) of the diffusion layer 82. For this reason, in order to prepare a plurality of light guide plate prototypes having different brightness uniformity degrees, it is not necessary to newly produce a trial transfer mold 69 having different concavo-convex shapes. In addition, according to the above manufacturing method, the light guide plate 30 from which light having a desired luminance uniformity is emitted is manufactured using the transfer die 69 used when forming the light guide plate prototype as it is. There is no need to prepare a new transfer mold 69 for manufacturing the light guide plate. As described above, the light guide plate 30 from which light having a desired luminance uniformity is emitted can be manufactured more efficiently and at low cost.

  Next, in the method for manufacturing the light guide plate 30 of the present embodiment, the fact that the luminance uniformity can be adjusted by changing the diffusing agent prescription of the light guide plate 30 will be described using the simulation results shown below. However, the light guide plate manufactured by the manufacturing method of the present invention is not limited to these simulations.

First, simulation conditions will be described. FIG. 5A is a schematic diagram showing a simulation model. FIG. 5B is an explanatory diagram for explaining a setting state of a local coordinate system on the exit surface and a method for defining angles from the c-axis and the a-axis in this coordinate system. For convenience of explanation, the components corresponding to the components shown in FIG. 2, and marked M to the light guide plate 30 _M. Simulation, FIG. 5 as shown in (a), like the point of the respective light source unit to the subject to the light guide plate 30 _M side 30 of M _c, 30 M _d opposite the location of the evaluation to be described in detail later In the model in which the light sources 21 _M and 21 _M are arranged and the white reflecting plate 25 _M is arranged below the light guide plate 30 _M , the emission intensity (W / mm ² ) is calculated using the ray tracing method.

Conditions for the light guide plate 30 _M are as follows.
-Constituent material of light guide plate 30 _M : base layer 31 _M , diffusion layer 32 _M, and protruding strip 33 _M all assume PMMA (refractive index: 1.49)-planar view shape (plate thickness) of light guide plate 30 _M (Shape seen from direction): rectangle / light guide plate 30 _M long side length W1: 540 mm
-Light guide plate 30 _M short side length W2: 20 mm
· The light guide plate 30 _M of thickness _t 30: 3 mm
Diffusion layer 32 _M diffusing agent: particle size 7 μm (refractive index 1.59)
Diffusion layer 32 _M diffusing agent concentration: 0.25 wt%
The distance between-the light guide plate 30 _M ridge 33 _M of the distal end portion of the white reflector plate 25 _M: 0.1 mm
-White reflector 25 _M : Assumes reflection characteristics equivalent to those of the white reflector taken from the backlight unit used in Sony's "KDL40EX7"

The point light source _21M will be described. Two point light sources 21 _M and 21 _M are arranged in the short-side direction of the light guide plate 30 _M , the distance L1 from each end is 5 mm, and the light source interval L2 is 10 mm. The point light source 21 _M is a surface light source having a length of 5.5 mm in the horizontal direction (Y-axis direction) and a length of 2 mm in the vertical direction (X-axis direction).

Figure 6 is a diagram showing an example of directional characteristics of the point light source 21 _M (light distribution characteristics). The horizontal axis in FIG. 6 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 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). It has the feature of going. PD in FIG. 6 shows the directional characteristics when the theoretical perfect diffusion, in this simulation assumed a point-like light source 21 _M that this characteristic can be obtained. Other conditions associated with the point light sources 21 _M are as follows.

The wavelength of light emitted from the point light source 21 _M is assumed to be 550 nm. The number of incident light rays from the point light source 21 _M is 10000000 (= 2500,000 × 4), and the amount of incident light is 4 W (= 1 W × 4).
_-Distance between the point light source 21 _M and the light guide plate 30 _M : 0.05 mm

Note that periodic boundary conditions were assumed for the side surface 30 _M e and the side surface 30 _M f of the light guide plate 30 _M. That is, in the side surface 30 _M e and the side surface 30 _M f, and to return to all the light reflection guided plate 30 _M. Thus, by providing periodic boundary conditions in the short-side direction of the light guide plate 30 _M (Y axis direction), the length of the short side direction is the simulation that assumes a substantially infinite light guide plate It will be.

It will be described the shape of the ridge 33 _M. In this simulation, expressed in cross-sectional configuration of the convex portion 33 _M orthogonal to the extending direction, the contour of the ridges 33 _M in conic. Specifically, as shown in FIG. 7, it sets the uv coordinate system, the cross-sectional shape of the convex portion 33 _M defined by a conic v (u) represented by the formula (1). The v-axis of the uv coordinate system corresponds to the Z-axis direction shown in FIG. 5A, and the u-axis corresponds to the X-axis direction shown in FIG.

In the formula (1), k _a is a parameter indicating the kurtosis how conic represented by the formula (1) represents the kurtosis way of the tip of the convex portion 33 _M. For example, when _{k a} is 0, the outer shape of the convex portion 33 _M becomes parabolic, when _{k a} is 1, the outer shape of the convex portion 33 _M becomes prism shape, when _{k a} is -1, ridges The outer shape of 33 _M is a shape obtained by cutting an ellipse in half. In this simulation, the ridge 33 _{M, k a} in equation (1) is 0.55, the aspect ratio _{[h a} / _w a] has a shape defined by 0.06. Further, (see FIG. 7) the width _{w a} of the convex portion 33 _M is 500 [mu] m.

  Next, in the above-described simulation model (hereinafter also referred to as “two-side incident light model”), it is confirmed that the luminance uniformity of the light emitted from the light guide plate can be adjusted by changing the diffusing agent prescription of the light guide plate. Therefore, the following simulation A and simulation B were performed.

(1) Simulation A
First, a simulation was performed for to confirm the change in luminance uniformity ratio, setting the light guide plate 30 _M as a reference when changing the spreading agent formulation. Specifically, as shown in FIG. 5A, in the two-side incident light model, the luminance uniformity when the thickness t ₃₂ of the diffusion layer 32 _M to which the diffusing agent is added is 100 μm is 95% or more. consisting such ridges 33 _M arranging method, namely, a simulation was performed to determine the coverage distribution of ridge 33 _M. According to this, the coverage distribution satisfying the above condition ridges 33 _M became that shown in FIG. 8 (a). The horizontal axis corresponds to the arrangement direction of the convex portions 33 _M (X axis direction). Position far from the point light source 21 _M, that is, as the central portion of the light guide plate 30 _M ridge 33 _M coverage increases distributions were calculated.

Next, the light guide plate 30 _{M in} which the ridge 33 _M is arranged so as to have the coverage distribution shown in FIG. 8A and the thickness t ₃₂ of the diffusion layer 32 _M is 100 μm is shown in FIG. When applied to the two-side incident light model shown, it was confirmed by simulation that the luminance uniformity was 95% or more. As a result, change in the emission intensity in the arrangement direction of the convex portion 33 _M is as shown in FIG. 8 (b), the luminance uniformity ratio was 97.3%. Ridges 33 _M is, as such a coverage based on the arranged light guide plate 30 _M such that the distribution was simulated B shown in later.

  A transfer mold for manufacturing a light guide plate prototype can be prepared by setting a target transfer rate of the shape from the transfer mold based on the result of the simulation A. By designing a transfer mold for manufacturing a light guide plate prototype by simulation or the like, it becomes possible to manufacture a light guide plate prototype that emits light close to the desired brightness uniformity at the prototype stage. . As a result, the evaluation step S2 and the determination step S3 in the manufacturing method can be performed more efficiently and at low cost.

  In addition, in the simulation A, an example in which a transfer mold is prepared to be a light guide plate that can emit light having an emission intensity distribution as shown in FIG. 8B has been described. However, the present invention is not limited to this. . For example, you may make it prepare the transcription | transfer type | mold for setting it as the light-guide plate from which the emitted light intensity of a light-guide plate edge part becomes weak compared with a light-guide plate center part.

(2) Simulation B
Next, when changing the diffusing agent formulation of the light guide plate 30 _M, a simulation was performed to confirm the change in the luminance uniformity of the light emitted from the light guide plate 30 _M. Specifically, in the two-side incident light model, the thickness t ₃₂ of the diffusion layer 32 _M is changed variously after setting the ridges 33 _{M to} have the coverage distribution shown in FIG. A simulation for calculating the emission intensity distribution was performed. The result of this simulation is as shown in FIG. Legend shown in FIG. 9 shows the thickness _{t 32} of the diffusion layer 32 _M.

According to FIG. 9, when no diffusing agent is added to the light guide plate 30 _M (the thickness t ₃₂ of the diffusion layer 32 _M is 0 μm), a position far from the point light source 21 _M , that is, near the center of the light guide plate 30 _M. Is getting brighter. Becomes thicker diffusion layer 32 _M thick _{t 32} of the light guide plate 30 _M, portion becomes brighter near the point light source 21 _M in the light guide plate 30 _M, confirmed that the portion far from the point light sources 21 _M darkens did it. According to the results of this simulation B, by changing the diffusing agent formulation of the light guide plate 30 _M, to be able to adjust the luminance uniformity of the light emitted from the light guide plate 30 _M was confirmed.

Next, in the method of manufacturing the light guide plate 30 of the present embodiment, the point that the luminance uniformity is adjusted by changing the diffusing agent prescription will be described using the results of the following simulation C and simulation D different from the above. . Simulation C and simulation D is greatly different from the simulation A and simulation B, as shown in FIG. 10, a point which incident light from one side of the light guide plate 30 _M, the light from the point light source 21 _M There side 30 _M c and facing the point where the white reflective tape 34 _M to the side surface 30 _M d are stuck to, the number of incident light from the point light sources 21 _M is present 10000000 is incident (= 5,000,000 this × 2 ), The amount of incident light is 2 W (= 1 W × 2), and a point where a simulation model different from the two-side incident light model (hereinafter also referred to as “one-side incident light model”) is used. Since other conditions are the same as those of the two-side incident light model, description thereof is omitted here.

(3) Simulation C
First, similarly to the above-described simulation A, it was simulated for in order to confirm the change in luminance uniformity ratio, setting the light guide plate 30 _M as a reference when changing the spreading agent formulation.

In the one side incident light model, the coverage distribution of ridges 33 _M satisfying the condition (brightness uniformity is 95% or more when the diffusion layer 32 _M thickness _{t 32} of 100 [mu] m) is, FIG. 11 (a) It became what was shown. The horizontal axis corresponds to the arrangement direction of the convex portions 33 _M (X axis direction). Incidentally, the left end of the graph in FIG. 11 (a) corresponds to the side surface 30 _M c of the point light source 21 _M side, the right end corresponds to the side surface 30 _M d side white reflective tape 34 _M was stuck. In other words, the coverage of the point light source 21 from _M farther position ridge 33 _M increases distributions were calculated.

Next, the light guide plate 30 _{M in} which the ridge 33 _M is arranged so as to have the coverage distribution shown in FIG. 11A and the thickness t ₃₂ of the diffusion layer 32 _M is 100 μm is shown in FIG. It was confirmed by simulation that the luminance uniformity was 95% or more when applied to the one side incident light model shown. As a result, change in the emission intensity in the arrangement direction of the convex portion 33 _M is as shown in FIG. 11 (b), the luminance uniformity ratio became 96.2%. Ridges 33 _M is, as such a coverage based on the arranged light guide plate 30 _M such that the distribution was simulated D shown in the subsequent stage.

  As described above, the transfer mold for manufacturing the light guide plate prototype can be prepared by setting the target transfer rate of the shape from the transfer mold based on the result of the simulation C. . Moreover, in the simulation C, although the example which prepares the transfer mold | type which becomes a light-guide plate which can radiate | emit the light of the emitted intensity distribution as shown in FIG.11 (b) was given and demonstrated, it is not limited to this. This is also as described above.

(4) Simulation D
Next, when changing the diffusing agent formulation in the light guide plate 30 _M, a simulation was performed to confirm the change in the luminance uniformity of the light emitted from the light guide plate 30 _M. Specifically, in one side incident light model, on the ridges 33 _M was set to be the coverage distribution shown in FIG. 11 (a), variously changing the thickness t ₃₂ of the diffusion layer 32 _M A simulation for calculating the emission intensity distribution was performed. The result of this simulation is as shown in FIG. Legend of FIG. 12 shows the thickness _{t 32} of the diffusion layer 32 _M.

According to FIG. 12, without the addition of diffusion agent in the light guide plate 30 _M (diffusion layer 32 _M of thickness _{t 32} is 0 .mu.m), a position far become part of the point light source 21 _M in the light guide plate 30 _M becomes brighter ing. It was confirmed that as the thickness t ₃₂ of the diffusion layer 32 _M was increased, the portion near the point light source 21 _M in the light guide plate 30 _M became brighter and the portion far from the point light source 21 _M became darker. According to the results of this simulation D, by varying the diffusing agent formulation of the light guide plate 30 _M, to be able to adjust the luminance uniformity of the light emitted from the light guide plate 30 _M was confirmed.

(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-described embodiment (hereinafter also referred to as “Embodiment 1”), the diffusing agent prescription is different by transferring the shape of the transfer mold at a predetermined transfer rate to the resin sheets having different diffusing agent prescriptions. While a plurality of light guide plate prototypes having the same uneven shape are molded, in the second embodiment, the shape of the transfer mold is transferred at different transfer rates to resin sheets having different diffusing agent formulations. Thus, a plurality of light guide plate prototypes having different diffusing agent formulations and uneven shapes are formed.

  Specifically, a thermoplastic resin and a thermoplastic resin to which a diffusing agent is added so as to have a predetermined concentration are prepared, and the first extruder 61 and the second extruder 62 of the optical sheet manufacturing apparatus 60 described above are prepared. Respectively. 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 diffusion layer 82 (FIG. 3B). The co-extrusion molding is performed by the die 63 so that The points so far are the same as in the first embodiment.

  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 mold 69 has been transferred is conveyed while being cooled on the peripheral surface of the second pressing roll 68, and then taken up as an optical sheet 80. At this time, the unevenness formed on the optical sheet 80 is adjusted by adjusting the transfer rate of the shape from the transfer die 69. This point is different from the first embodiment.

As described above, a two-type two-layer optical sheet 80 constituted by the base layer 81 and the diffusion layer 82 shown in FIG. 3B, that is, the light guide plate 30 can be obtained. In the present embodiment, a city the same thickness t ₈₀ of the entire optical sheet 80, while variously changing the thickness t ₈₂ of the diffusion layer 82, further, a plurality of times while variously changing also the transfer rate of the shape of the transfer mold 69 Is formed. Thus, a plurality of light guide plate prototypes having a predetermined concavo-convex shape with a predetermined diffusing agent prescription are formed. For example, only the thickness t ₈₂ and the several different types of light guide plate prototype of the diffusion layer 82 was changed irregularities (the transfer rate at the time of transfer is changed) for each of the several light guide plate prototype several A light guide plate prototype can be prepared.

  Next, the difference between the two in the evaluation step S2 will be described. In the first embodiment, only the luminance uniformity of each of the plurality of light guide plate prototypes molded in the prototype molding step S1 is evaluated, whereas in the second embodiment, the plurality of guides molded in the prototype molding step S1 are evaluated. Evaluate the brightness uniformity and peak angle of each light plate prototype. Specifically, for a plurality of manufactured light guide plate prototypes, the emission intensity distribution and the like are obtained by simulation and actual measurement to evaluate the luminance uniformity. In addition to this, for a plurality of manufactured light guide plate prototypes, for example, the emission intensity at each angle emitted from the central portion of the light guide plate is acquired by simulation or actual measurement to evaluate the peak angle.

Next, the difference between the two in the determination step S3 will be described. In the first embodiment, only the diffusing agent prescription for the light guide plate 30 is determined based on the luminance uniformity, whereas in the second embodiment, the diffusing agent prescription and the uneven shape of the light guide plate 30 are determined based on the luminance uniformity. Is done. Specifically, the desired brightness uniformity and peak angle are determined by comparing the brightness uniformity and peak angle of each light guide plate prototype evaluated in the evaluation step S2 with the target brightness uniformity and peak angle. The diffusing agent formulation for obtaining a good result, that is, the thickness t ₈₂ of the diffusion layer ₈₂ and the transfer rate of the shape from the transfer die 69 are determined.

  Next, the difference between them in the light guide plate forming step S4 will be described. In the first embodiment, the light guide plate is formed based on the determined diffusing agent prescription, whereas in the second embodiment, the light guide plate is formed based on the determined diffusing agent prescription and the uneven shape. For example, the transfer mold used when the light guide plate prototype is molded at a transfer rate corresponding to the concavo-convex shape determined in the determination step S3 with respect to the resin sheet having the diffusing agent prescription determined in the determination step S3. By transferring the shape, an optical sheet serving as a light guide plate can be formed. This will be specifically described below.

  First, the same thermoplastic resin as prepared in the prototype forming step S1 and a thermoplastic resin to which a diffusing agent is added so as to have a predetermined concentration are prepared, and the first of the optical sheet manufacturing apparatus 60 described above is prepared. It is put into the extruder 61 and the second extruder 62, respectively. 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 diffusion layer 82 (FIG. 3B). The co-extrusion molding is performed by the die 63 so that The thickness t ₈₂ of the diffusion layer 82, to a thickness determined by the decision step S3 is co-extrusion is carried out. This is the same as in the first embodiment.

  In the second embodiment, when the coextruded resin is subjected to pinching and cooling by the pre-press roll 66, the first press roll 67, and the second press roll 68, the transfer corresponding to the determined uneven shape is performed. Transcribed at a 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 diffusion layer 82 shown in FIG.3 (b) is obtained. Thereby, the light-guide plate 30 which has a desired brightness | luminance uniformity can be obtained.

  Here, the transfer rate will be described. FIGS. 13A to 13C are schematic views showing an embodiment of the step of forming the optical sheet 80 as the light guide plate 30 (also the light guide plate prototype). As shown in FIG. 13A, the shape of the transfer die 69 is an inverted shape in which a concave portion 69a that is a groove having a depth h1 corresponding to the shape of the convex portion 83 of the concave and convex shape of the optical sheet 80 is formed. have. As shown in FIG. 13B, the resin sheet 70 is pressed and filled in the recess 69a. The height h2 of the ridge 83 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 remains 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 contracts due to thermoelastic deformation, the height h3 of the ridge 83 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 of the final protrusion 83 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 30 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. be able to.

  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.

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, by changing the thickness t ₈₂ (diffusion agent formulation) of the diffusion layer 82 and the transfer rate of the shape from the transfer mold 69, the luminance uniformity and peak angle of the emitted light are changed. A plurality of different light guide plate prototypes are prepared. For this reason, in order to prepare a plurality of light guide plate prototypes that emit light having different luminance uniformity and peak angles, it is not necessary to newly create a prototype transfer die 69 having different concavo-convex shapes. 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 luminance uniformity and peak angle is emitted can be manufactured more efficiently and at low cost.

  Furthermore, according to the manufacturing method according to the second embodiment, since the uneven shape can be changed by changing the transfer rate of the shape from the transfer die 69, the peak angle of the emitted light is also added to the luminance uniformity. Will be able to adjust. Accordingly, the light guide plate 30 from which light is emitted at a desired luminance uniformity and peak angle can be manufactured more efficiently and at a low cost, and the optical member disposed on the output side of the light guide plate 30 The optimal light guide plate 30 matched with the characteristics can be manufactured.

  Next, in the method of manufacturing the light guide plate 30 according to the second embodiment, the brightness uniformity is adjusted by changing the transfer rate of the shape from the transfer die 69 at the time of molding. This will be described using the results of simulation E, simulation F, and simulation G.

(5) Simulation E
Here, in the two sides light incident model shown in FIG. 5 (a), convex portions 33 _M is in terms of the set to be the coverage distribution shown in FIG. 8 (a), from the transfer mold 69 during the molding when changing the transfer ratio of the shape, i.e., a simulation was performed to confirm the change in the luminance uniformity ratio when changing the shape of the ridge 33 _M for forming the light guide plate 30 _M. The result of this simulation is as shown in FIG. The legend shown in FIG. 14 shows the transfer rate of the shape from the transfer mold 69.

Incidentally, just as in this simulation, kurtosis of lenses (k _a in the formula represents the conic ₍₁₎₎ is fixed, by changing the aspect ratio h _{a /} w _a, changes the transfer ratio Result can be obtained.

According to FIG. 14, as the transfer rate of the shape of the transfer mold 69 is high at the time of molding (larger aspect ratio of the convex portion 33 _M is), the position farther from the point light source 21 _M, i.e. the light guide plate 30 _M of The area near the center becomes dark. According to the results of this simulation E, by varying the transfer rate of the shape of the transfer mold 69 during molding, the uniformity ratio of luminance of light emitted from the light guide plate 30 _M was confirmed to be able to adjust.

Then, by changing the transfer ratio of the shape of the transfer mold 69 during the molding (the aspect ratio of the ridges 33 _M), peak angle theta ₃₀ of light emitted from the light guide plate to confirm that the adjusted Therefore, the following simulation F and simulation G were performed.

(6) Simulation F
First, the two sides light incident model shown in FIG. 5 (a), on the ridges 33 _M was set to be the coverage distribution shown in FIG. 8 (a), the thickness of the diffusion layer 32 _M t ₃₂ A simulation was performed to confirm the change in the peak angle θ ₃₀ when changing. The result of this simulation is as shown in FIG. Legend shown in FIG. 15 (a) shows the thickness _{t 32} of the diffusion layer 32 _M.

The distribution of the peak angle θ ₃₀ of light emitted from the vicinity of the center p of the light guide plate 30 _M is symmetric in the bc plane shown in FIG. 5B, and symmetric at θ ₃₀ = 0 °. For this reason, the peak angle θ ₃₀ shown in FIG. 15A is a value shown in the range of 0 ° ≦ θ ₃₀ ≦ 90 °.

(7) Simulation G
Then, the two sides light incident model as shown in FIG. 5 (a), on the ridges 33 _M was set to be the coverage distribution shown in FIG. 8 (a), the transfer mold during molding 69 when changing the transfer ratio of the shape from, i.e., a simulation was performed to calculate the distribution of the peak angle theta ₃₀ when changing the shape of the ridge 33 _M. The result of this simulation is as shown in FIG. The legend shown in FIG. 15B shows the transfer rate of the shape from the transfer mold 69.

According to FIG. 15A and FIG. 15B, the following could be confirmed. That is, when changing the diffusion layer 32 _M thickness (diffusion agent formulation), as shown in FIG. 15 (a), although the radiation intensity is changed, did not change in the peak angle theta ₃₀ occurs. In contrast, when changing the transfer ratio (the shape of the convex portion 33 _M), as shown in FIG. 15 (b), together with the radiation intensity is changed, confirmed that the change occurs in the peak angle theta ₃₀ did it. To adjust the luminance uniformity ratio, and a method of changing the spreading agent formulation, there are a method of changing the transfer rate, in the case of adjusting the luminance uniformity ratio by changing the transfer rate, emitted from the light guide plate 30 _M It was confirmed that the peak angle θ _{30 of the} emitted light can be adjusted simultaneously.

  Next, in the method of manufacturing the light guide plate 30 according to the second embodiment, the brightness uniformity is adjusted by changing the transfer rate of the shape from the transfer die 69 at the time of molding. This will be described using the results of simulation H, simulation I, and simulation J. These simulations H to I are greatly different from the simulations E to G in that a one-side incident light model is used.

(8) Simulation H
Here, in the side light entrance model shown in FIG. 10, on the ridges 33 _M was set to be the coverage distribution shown in FIG. 11 (a), the transfer rate of the shape of the transfer mold 69 during the molding when changing, i.e., a simulation was performed to confirm the change in the luminance uniformity ratio when changing the shape of the ridge 33 _M for forming the light guide plate 30 _M. The result of this simulation is as shown in FIG. The legend shown in FIG. 16 shows the transfer rate of the shape from the transfer mold 69.

Also in this simulation, kurtosis of lenses (k _a in the formula represents the conic ₍₁₎₎ is fixed, by changing the aspect ratio h _{a /} w _a, similar to changing the transfer rate Result can be obtained.

According to FIG. 16, as the transfer rate of the shape of the transfer mold 69 is high at the time of molding (larger aspect ratio of the convex portion 33 _M is), the position farther from the point light source 21 _M, i.e. white reflective tape 34 _M near the side 30 _M d which was attached a becomes dark. On the contrary, the position farther from the point light source 21 _M, that is bright in the vicinity of the side surface 30 M _d which was attached a white reflective tape 34 _M. According to this simulation H results by changing the transfer ratio of the shape of the transfer mold 69 during molding, to be able to adjust the luminance uniformity of the light emitted from the light guide plate 30 _M was confirmed.

Then, the transfer ratio of the shape of the transfer mold 69 during molding when varying (aspect ratio of ridge 33 _M), in order to confirm the change of the peak angle theta ₃₀ of light emitted from the light guide plate The following simulation I and simulation J were performed.

(9) Simulation I
First, in the one side incident light model shown in FIG. 10, the peak angle when the thickness of the diffusion layer 32 _M is changed after the ridge 33 _M is set to have the coverage distribution shown in FIG. a simulation was performed to confirm the change of θ _30. The result of this simulation is as shown in FIG. Legend shown in FIG. 17 (a) shows the thickness _{t 32} of the diffusion layer 32 _M.

In the one side incident light model, unlike the two sides light incident model, the distribution of the peak angle theta ₃₀ of light emitted from the light guide plate 30 _M near the center p becomes symmetrical in bc plane shown in FIG. 10 (b) There is nothing. Therefore, the peak angle θ ₃₀ here is a value shown in the range of 0 ° ≦ θ ₃₀ ≦ 90 °.

(10) Simulation J
Next, in the side light entrance model shown in FIG. 10, on the ridges 33 _M was set to be the coverage distribution shown in FIG. 11 (a), the transfer rate of the shape of the transfer mold 69 during the molding when changing, i.e., a simulation was performed to calculate the distribution of the peak angle theta ₃₀ when changing the shape of the ridge 33 _M. The result of this simulation is as shown in FIG. The legend shown in FIG. 17B shows the transfer rate of the shape from the transfer mold 69.

According to FIG. 17A and FIG. 17B, the following could be confirmed. That is, when the diffusing agent formulation is changed as a means for adjusting the luminance uniformity, it is confirmed that the peak angle θ ₃₀ does not change although the radiation intensity changes as shown in FIG. did it. On the other hand, when the transfer rate was changed, it was confirmed that the radiation intensity changed and the peak angle θ ₃₀ changed as shown in FIG. To adjust the luminance uniformity ratio, and a method of changing the spreading agent formulation, there are a method of changing the transfer rate, in the case of adjusting the luminance uniformity ratio I by varying the transfer rate is emitted from the light guide plate 30 _M It was confirmed that the peak angle θ _{30 of the} emitted light can be adjusted simultaneously.

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

  In the light guide plate forming step S4 of the second embodiment, the resin sheet prescribed with the diffusing agent determined in the determining step S3 is transferred at a transfer rate corresponding to the uneven shape determined in the determining step S3. Although an example of forming the light guide plate 30 has been described, the present invention is not limited to this.

  For example, in the light guide plate forming step S4, a transfer sheet for producing a light guide plate having an inverted shape corresponding to the uneven shape determined in the determination step S3 is prepared, and the resin sheet on which the diffusing agent prescription determined in the determination step S3 is made. On the other hand, the light guide plate 30 may be formed by transferring the light guide plate manufacturing transfer mold. At this time, the transfer mold for manufacturing the light guide plate may have an inverted shape in which the uneven shape of the light guide plate is formed when transferred at a transfer rate of 90% or more.

  Also, for example, as shown in FIG. 18, 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, a transfer rate of 50% or more and less than 90% can be set as the transfer rate having the above-described stability.

In the above embodiment, the diffusing agent formulation has been described by taking a method of changing the thickness t ₈₂ of the diffusion layer 82 diffusing agent is added to a predetermined concentration as an example, the present invention is not limited thereto It is not a thing. For example, as a diffusing agent prescription, the light guide plate may have a single-layer structure instead of a two-layer structure, and the addition amount of the diffusing agent may be adjusted. In addition, as a diffusing agent prescription, not only the concentration and addition amount of the diffusing agent can be adjusted, but also the refractive index and particle size can be adjusted by changing the kind of the light diffusing agent.

  In the prototype forming step S1 of the above embodiment, a plurality of light guide plate prototypes having different diffusing agent prescriptions or a plurality of light guide plate prototypes having different diffusing agent prescriptions and uneven shapes are formed at a time. Although described with an example, the present invention is not limited to this.

  For example, in the first embodiment, one prototype of a light guide plate having a predetermined diffusing agent formulation is formed in the prototype forming 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 diffusing agent prescription from the light guide plate prototype. In this case, the prototype forming step S1 and the evaluation step S2 are repeated until a desired luminance uniformity is obtained.

  Further, for example, in the second embodiment, in the prototype forming step S1, one light guide plate prototype transferred at a predetermined diffusing agent prescription and a predetermined transfer rate is formed, and in the evaluation step S2, the guide is formed. After evaluating the optical plate prototype, molding a light guide plate prototype transferred at the same transfer rate on a resin with a different diffusing agent formulation from the previous light guide plate prototype, This includes forming a prototype of a light guide plate transferred at a different transfer rate for a resin with a different diffusing agent formulation from the work. In this case, the prototype forming step S1 and the evaluation step S2 are repeated until the desired 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 diffusing agent prescription will be determined.

  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, a two-dimensional uneven shape such as a microlens or a pyramidal prism may be used.

  In the embodiment shown in FIG. 13, the cross-sectional shape of the recess 69a of the transfer mold 69 is a mountain shape, 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 method of manufacturing the light guide plate, a surface light source device having a configuration in which two opposite side surfaces 30c and 30d as shown in FIG. However, for example, a surface light source device having a configuration in which one side surface is an incident surface and a white reflective tape is attached to the side surface at a position facing the incident surface may be used.

  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 molding method may be other molding 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, 30d ... Side surface (incident surface), 31 ... Base layer, 32 ... Diffusion layer, 33 ... Convex strip, 34 ... White reflective tape, 40 ... Various types Optical film, 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 ... recess, 70 ... resin sheet, 70a ... surface, 71 ... melt bank, 80 ... optical sheet, 81 ... base layer, 82 ... diffusion layer, 83 ... ridge.

Claims (11)

Prototype molding step of molding a plurality of light guide plate prototypes by transferring the shape of the transfer mold to resin sheets having different diffusing agent prescriptions,
An evaluation step for evaluating the brightness uniformity of each of the plurality of light guide plate prototypes;
A determining step for determining a diffusing agent prescription for a light guide plate that emits light of a desired luminance uniformity based on the evaluated luminance uniformity;
A light guide plate forming step for forming the light guide plate based on the determined diffusing agent prescription,
A method for manufacturing a light guide plate, comprising: The resin sheet is composed of a plurality of layers including a diffusion layer to which a diffusing agent is added,
The diffusing agent formulation is performed by adjusting the thickness of the diffusion layer,
The manufacturing method of the light-guide plate of Claim 1. The diffusing agent formulation is performed by adjusting the amount of diffusing agent added,
The manufacturing method of the light-guide plate of Claim 1 or 2. In the prototype molding step, the shape of the transfer mold is transferred at a predetermined transfer rate to the resin sheets having different diffusing agent formulations.
The manufacturing method of the light-guide plate in any one of Claims 1-3. In the prototype molding step, a plurality of light guide plate prototypes having different diffusing agent prescriptions and uneven shapes are transferred to resin sheets having different diffusing agent prescriptions by transferring the shape of the transfer mold at different transfer rates. Molded,
In the evaluation step, the brightness uniformity and the peak angle of each of the plurality of light guide plate prototypes are evaluated,
In the determining step, based on the evaluated brightness uniformity and the peak angle, determine a diffusing agent prescription and a concavo-convex shape for a light guide plate that emits light of a desired brightness uniformity and peak angle,
In the light guide plate forming step, the light guide plate is formed based on the determined diffusing agent prescription and uneven shape,
The manufacturing method of the light-guide plate in any one of Claims 1-3. In the light guide plate forming step, the same transfer rate as when the shape of the transfer mold used in the prototype forming step was transferred in the prototype forming step to the resin sheet subjected to the determined diffusing agent prescription. The light guide plate is formed by transferring with
The manufacturing method of the light-guide plate in any one of Claims 1-4. In the light guide plate forming step, the shape of the transfer mold used in the prototype forming step is transferred to the resin sheet having the determined diffusing agent prescription at a transfer rate corresponding to the determined uneven shape. To form the light guide plate,
The manufacturing method of the light-guide plate of Claim 5. In the light guide plate forming step, the light guide plate is transferred to the resin sheet having the determined diffusing agent prescription by transferring a transfer mold for manufacturing a light guide plate having an inverted shape corresponding to the determined uneven shape. Molding,
The manufacturing method of the light-guide plate of Claim 5. The transfer mold for manufacturing the light guide plate has an inverted shape in which the uneven shape of the light guide plate is formed when transferred at a transfer rate of 90% or more,
The manufacturing method of the light-guide plate of Claim 8. 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, a transfer mold for manufacturing a light guide plate in which the determined uneven shape is obtained at the transfer rate found in the confirmation step with respect to the resin sheet having the determined diffusing agent prescription. Forming the light guide plate by transferring
The manufacturing method of the light-guide plate of Claim 5. The transfer rate having the stability is 50% or more and less than 90%.
The manufacturing method of the light-guide plate of Claim 10.

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