JP2012030590A - Method of manufacturing surface shape-transferred resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a surface shape-transferred resin sheet, capable of accurately transferring a transfer mold onto a surface of a resin sheet while maintaining the surface smoothness and thickness uniformity of the sheet.SOLUTION: A resin sheet 53 is produced by extruding a resin from a die 58 in a heated and melted state; the resin sheet 53 is inserted between an upper roll 63 and an intermediate roll 64, and the resin sheet 53 is carried as it is closely pressed against the intermediate roll 64. In this step, an engraved plate transfer mold 69 is attached to the intermediate roll 64, and a melt bank 73 having a height h which is equal to or less than 1.1 times a gap A between the upper roll 63 and the intermediate roll 64 is formed at the inlet of the gap A.

Description

  The present invention relates to a method for producing a surface shape transfer resin sheet that can be used as a light diffusing plate or a light guide plate used in a liquid crystal display device.

The surface shape transfer resin sheet is, for example, a sheet produced by forming a resin sheet that is heated and in a softened state, and transferring the uneven shape of the transfer mold to the surface of the resin sheet.
Specifically, the melt-kneaded resin is continuously extruded from a die, and the extruded resin is passed through an air gap from the nip position between the first roll and the second roll, and the first roll and the second roll. A manufacturing method is known that includes a step of feeding to a roll gap provided between and a step of pressing a resin sent to the roll gap with a second roll (see, for example, Patent Document 1). In this method, a mold corresponding to a mold corresponding to the target lenticular lens shape is provided, and when the resin is pressed by the second roll, an uneven shape is formed on the surface of the resin.

JP 2005-66953 A

  As a use of the surface shape transfer resin sheet, a use as a light diffusion plate or a light guide plate incorporated in a backlight device of a liquid crystal display device is becoming widespread. In this case, if the uneven shape is not accurately transferred when the resin sheet is manufactured, there is a possibility that desired optical characteristics cannot be imparted to the light diffusion plate or the light guide plate. Therefore, in recent years, establishment of a technique for accurately transferring a transfer mold onto a resin sheet is desired.

On the other hand, in the field of manufacturing a sheet by resin molding, the surface smoothness and thickness uniformity of the sheet are also important characteristics of the resin sheet. Conventionally, in order to maintain such characteristics, a melt bank (resin pool) is formed at the entrance between the opposing pressure rolls, and a sheet is formed by feeding the resin from the melt bank to the gap between the pressure rolls. It was broken.
The size (height) of the melt bank is preferably larger if only the surface smoothness and thickness uniformity of the sheet are taken into consideration. As the height of the melt bank increases, the contact area between the melt bank and the pressure roll increases, so that the resin can be fed from the pressure roll to the melt bank with a large surface pressure. It is thought that the property and thickness uniformity can be improved.

  However, when the height of the melt bank is large, the time during which the resin stays as the melt bank becomes long. Therefore, the resin before being sent out between the press rolls is gradually cooled and hardened from the contact surface with the press roll, and when it is sent between the press rolls, the fluidity may be lowered. Therefore, as in Patent Document 1, when the transfer die is provided in the first press roll that is discharged from the die, the fed resin cannot sufficiently enter the recessed portion of the transfer mold, Transferability may be insufficient.

  An object of the present invention is to provide a method for producing a surface shape transfer resin sheet capable of accurately transferring the shape of a transfer mold onto the surface of a resin sheet while maintaining the surface smoothness and thickness uniformity of the sheet. It is.

  The method for producing a surface shape transfer resin sheet of the present invention for achieving the above object includes an extrusion step of continuously extruding a resin from a die in a heated and melted state to produce a continuous resin sheet, A pressing step sandwiched between the pressing roll and the second pressing roll; and a transporting step of transporting the continuous resin sheet in close contact with the second pressing roll after the pressing step. A transfer mold is provided on the surface, and in the pressing step, a melt bank having a height of 1.1 times or less of a gap A between the first pressing roll and the second pressing roll is provided with the first pressing roll and the first pressing roll. It is characterized by including the process of forming between 2 press rolls.

Moreover, in the manufacturing method of the surface shape transfer resin sheet of this invention, it is suitable that the conveyance speed of the said continuous resin sheet is 2.5 m / min or more.
In the method for producing a surface shape transfer resin sheet of the present invention, it is preferable that the resin is an amorphous resin.
In the method for producing a surface shape transfer resin sheet of the present invention, the amorphous resin is mainly composed of a styrene resin, an acrylic resin, an acrylic / styrene copolymer resin, a cyclic olefin resin, or a polycarbonate system. It is preferable to include.

Moreover, in the manufacturing method of the surface shape transfer resin sheet of the present invention, the transfer mold has grooves formed in a plurality of streaks along the circumferential direction of the second pressing roll, and the adjacent groove portions The interval (pitch P) is preferably 200 μm to 500 μm, and the depth H of the groove is preferably 100 μm to 500 μm.
In the method for producing a surface shape transfer resin sheet of the present invention, it is preferable that an aspect ratio represented by the depth H of the groove / the pitch P of the groove is 0.4 or more.

  Furthermore, in the method for producing a surface shape transfer resin sheet of the present invention, it is preferable that the cross-sectional shape in a direction orthogonal to the longitudinal direction of the groove portion is a substantially semicircular shape, a substantially semielliptical shape, or a substantially prism shape.

  According to the method for producing a surface shape transfer resin sheet of the present invention, since the height of the melt bank is 1.1 times or less of the gap A between the first pressing roll and the second pressing roll, the melt bank is the pressing roll. The resin can be sequentially sent out to the gap A before being cooled and solidified. Therefore, the molten resin fed into the gap A can be satisfactorily entered into the recessed portion of the transfer mold provided in the second pressing roll. Therefore, the transfer mold can be accurately transferred onto the surface of the resin sheet. As a result, if the resin sheet obtained by this manufacturing method is used as a light diffusion plate or a light guide plate of a liquid crystal display device, excellent optical characteristics can be expressed.

  Moreover, since it forms by a press roll after forming a melt bank, the surface smoothness and thickness uniformity of a resin sheet can also be hold | maintained.

FIG. 1 is a schematic side view of a liquid crystal display device (first form) on which a light diffusion plate (resin sheet) according to an embodiment of the present invention is mounted. FIG. 2 is a schematic perspective view of the liquid crystal display device of FIG. FIG. 3 is a schematic perspective view of the light diffusion plate of FIG. FIG. 4 is an enlarged cross-sectional view of a main part of the lamp box showing a mounted state of the light diffusing plate. FIG. 5 is a schematic side view of a liquid crystal display device (second embodiment) on which a light guide plate (resin sheet) according to an embodiment of the present invention is mounted. FIG. 6 is a schematic plan view of the backlight system of FIG. FIG. 7 is a schematic rear view of the backlight system of FIG. FIG. 8 is a diagram illustrating a modification of the dot pattern of the light guide plate. FIG. 9 is a schematic configuration diagram of a manufacturing apparatus used in the method for manufacturing a resin sheet according to an embodiment of the present invention. FIG. 10 is an enlarged perspective view of the upper roll and the intermediate roll. FIG. 11 is an enlarged cross-sectional view of a main part of the intaglio transfer mold attached to the intermediate roll. FIG. 12 is a diagram showing a first modified example (substantially semicircular shape) of the intaglio transfer mold. FIG. 13 is a view showing a second modified example (substantially prism shape) of the intaglio transfer type.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<Liquid crystal display device (first form)>
(1) Backlight System FIG. 1 is a schematic side view of a liquid crystal display device (first embodiment) on which a light diffusion plate (resin sheet) according to an embodiment of the present invention is mounted. FIG. 2 is a schematic perspective view of the liquid crystal display device of FIG.

  The liquid crystal display device 1 (liquid crystal television) is a so-called direct-type liquid crystal display device, and includes a backlight system 2, a liquid crystal panel 3 disposed in front of the backlight system 2, a backlight system 2, and a liquid crystal panel 3. And an optical film 4 disposed between the two. In FIG. 1 and FIG. 2, the liquid crystal display device 1 is shown in a posture with its front side facing the upper side of the drawing for the sake of convenience. Further, the scales of the constituent members such as the liquid crystal display device 1, the backlight system 2, and the liquid crystal panel 3 shown in the following drawings are set for convenience of explanation, and the scales of all the constituent members are the same. Not that.

The backlight system 2 has a rectangular plate-shaped rear wall 5 and a rectangular frame-shaped side wall 6 integrally standing upright from the periphery of the rear wall 5, and is made of a thin box-shaped resin whose front side is open. A lamp box 7, a plurality of linear light sources 8 provided in the lamp box 7, and a light diffusion plate 10 that closes an open surface 9 (front surface) of the lamp box 7 are provided.
That is, the box-shaped lamp box 7 has an open surface 9 whose outline is defined by a square-shaped side wall 6, and a linear light source 8 is provided in a space surrounded by the side wall 6 and the rear wall 5. On the inner surface of the rear wall 5 of the lamp box 7, for example, a reflection plate (not shown) for reflecting light incident on the rear wall 5 side from the linear light source 8 toward the open surface 9 side of the box is attached to the whole. It has been.

The linear light source 8 is, for example, a cylindrical lamp having a diameter of 2 mm to 4 mm. The plurality of linear light sources 8 are arranged in parallel with each other at an equal interval in a state where they are spaced apart from the back surface 18 of the light diffusion plate 10.
The distance L between the centers of the adjacent linear light sources 8 is preferably 30 mm to 60 mm from the viewpoint of power saving. Moreover, it is preferable that the distance D of the back surface 18 (for example, center part in the back surface 18) of the light diffusing plate 10 and the center of the linear light source 8 is 10 mm-20 mm from a viewpoint of thickness reduction. Moreover, it is preferable that the ratio (L / D) of the space | interval L with respect to the distance D is 2.5-4.0. In particular, the distance L is preferably 40 mm to 55 mm, and the distance D is preferably 13 mm to 17 mm. The number of the linear light sources 8 is inevitably determined by the size of the lamp box 7 (screen size of the liquid crystal display device 1) and the interval L. For example, in the 32 type liquid crystal display device 1, the number is 6-10. Preferably there is. In FIG. 1 and FIG. 2, only five linear light sources 8 are shown for easy illustration.
Moreover, as the linear light source 8, well-known cylindrical lamps, such as a fluorescent tube (cold cathode tube), a halogen lamp, a tungsten lamp, can be used, for example. Further, as the light source of the backlight system 2, a point light source such as a light emitting diode (LED) can be used instead of the linear light source 8.
(2) Liquid Crystal Panel The liquid crystal panel 3 includes a liquid crystal cell 11 and a pair of polarizing plates 12 and 13 that sandwich the liquid crystal cell 11 from both sides in the thickness direction. Such a liquid crystal panel 3 is disposed on the front surface of the backlight system 2 so that the polarizing plate 12 on the back side and the light diffusion plate 10 face each other.

As the liquid crystal cell 11, for example, a known liquid crystal cell such as a TFT liquid crystal cell or an STN liquid crystal cell can be used.
(3) Optical film The optical film 4 is not particularly limited, and examples thereof include a microlens film, a substantially semicircular lenticular lens film, a diffusion film, a prism film, and a reflective polarization separation film.
(4) Light Diffusing Plate FIG. 3 is a schematic perspective view of the light diffusing plate of FIG. FIG. 4 is an enlarged cross-sectional view of a main part of the lamp box showing a mounted state of the light diffusion plate.

As shown in FIG. 3, the light diffusing plate 10 is formed in a square plate shape that is substantially the same as the frame shape of the side wall 6 of the lamp box 7.
On one main surface (outgoing surface 16) of the light diffusing plate 10, a plurality of ridges 17 extending between a pair of opposed peripheral edges of the light diffusing plate 10 are formed in a streak shape. That is, on the emission surface 16 of the light diffusing plate 10, the ridges 17 and the grooves 19 between the adjacent ridges 17 are alternately formed.

As for the protruding item | line part 17, the cut surface orthogonal to the longitudinal direction has the outline of a substantially semi-elliptical shape. The shape of the ridge portion 17 may be a semi-elliptical shape, a prism shape, or a semi-circular shape. Moreover, the shape which changes continuously in one protruding item | line part 17 (shape unit) is preferable, for example, a semicircle shape or a semi-elliptical shape is more preferable than a prism shape.
A large number of the ridges 17 are arranged at an equal interval E (for example, 1 μm to 15 μm) in parallel with each other. The distance (pitch P ′) between the centers of the adjacent ridges 17 is, for example, 200 μm to 500 μm. Moreover, the height (depth of the ditch | groove 19) H 'of the protruding item | line part 17 is 100 micrometers-500 micrometers, for example. Moreover, the aspect ratio represented by the ratio (H '/ P') of the height H 'to the pitch P' of the ridges 17 is, for example, 0.4 or more, preferably 0.5 to 0.7. is there.

On the other hand, the other main surface (back surface 18) of the light diffusing plate 10 is a flat surface having no irregularities.
Moreover, as shown in FIG. 4, the thickness T of the light diffusing plate 10 from the back surface 18 to the top part of the convex part 17 in the output surface 16 is 1 mm-4 mm, for example.
The raw material of the light diffusing plate 10 is not particularly limited, and for example, an amorphous translucent resin can be used.

  As an amorphous translucent resin to be used, for example, acrylic resin, styrene resin, polycarbonate, cyclic polyolefin, cyclic olefin copolymer, MS resin (methyl methacrylate-styrene copolymer resin), ABS resin ( And acrylonitrile-butadiene-styrene copolymer resin) and AS resin (acrylonitrile-styrene copolymer resin).

The said amorphous translucent resin can be used individually or in combination with 2 or more types. Among these, Preferably, a styrene resin or an acrylic resin is mentioned, More preferably, a single use of a styrene resin or a single use of an acrylic resin is mentioned.
Moreover, the light diffusing plate 10 can contain a light diffusing agent (light diffusing particles) if necessary.

  The light diffusing agent is not particularly limited as long as it has a refractive index different from that of the translucent resin constituting the light diffusing plate 10 and can diffuse transmitted light. For example, as an inorganic light diffusing agent, calcium carbonate, Examples thereof include barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, and zinc oxide. These may be subjected to a surface treatment with a fatty acid or the like.

Examples of the organic light diffusing agent include styrene polymer particles, acrylic polymer particles, and siloxane polymer particles. Preferably, the weight average molecular weight is 500,000 to 5,000,000. Examples include coalescent particles and crosslinked polymer particles having a gel fraction of 10% by mass or more when dissolved in acetone.
The light diffusing agents can be used alone or in combination of two or more.

  When the light diffusing plate 10 contains a light diffusing agent, the mixing ratio of the light diffusing agent is 0.001 to 1 part by weight, preferably 0.001 to 0.01 with respect to 100 parts by weight of the light-transmitting resin. Parts by weight. Moreover, a light-diffusion agent can be used as a masterbatch with the said translucent resin. Further, the absolute value of the difference between the refractive index of the translucent resin and the refractive index of the light diffusing agent is usually 0.01 to 0.20, preferably 0.02 to 0.02 from the viewpoint of light diffusibility. 0.15.

The light diffusing plate 10 may have various additives such as an antistatic agent, an ultraviolet absorber, a heat stabilizer, an antioxidant, a weathering agent, a light stabilizer, a fluorescent whitening agent, and a processing stabilizer, as necessary. Can also be added.
The ultraviolet absorber is not particularly limited, and examples thereof include salicylic acid phenyl ester ultraviolet absorbers, benzophenone ultraviolet absorbers, triazine ultraviolet absorbers, and benzotriazole ultraviolet absorbers. When adding an ultraviolet absorber, it is preferable to add 0.1-3 weight part of ultraviolet absorbers with respect to 100 weight part of translucent resin. If it is the above-mentioned range, the bleeding to the surface of an ultraviolet absorber can be suppressed and the external appearance of a light diffusing plate can be maintained favorable.

  The heat stabilizer is not particularly limited, and examples thereof include manganese compounds and copper compounds. When adding the heat stabilizer, it is preferably added together with the ultraviolet absorber, and the heat stabilizer is preferably added at a ratio of 2 parts by weight or less with respect to 1 part by weight of the ultraviolet absorber in the translucent resin. More preferably, 0.01 to 1 part by weight of a heat stabilizer is added to 1 part by weight of the ultraviolet absorber in the translucent resin.

Moreover, it does not restrict | limit especially as antioxidant, For example, a hindered phenol compound, a hindered amine compound, etc. are mentioned. When adding antioxidant, it is preferable to add 0.1-3 weight part of antioxidant with respect to 100 weight part of translucent resin.
As shown in FIG. 4, the light diffusing plate 10 has a light diffusing plate with respect to the side wall 6 of the lamp box 7 at a position where the ridges 17 are parallel to the linear light source 8 in the lamp box 7. 10 is fixed to the lamp box 7 by bringing the back surface 18 into contact therewith. As a result, the open surface 9 of the lamp box 7 is blocked by the light diffusion plate 10.
<Liquid crystal display device (second embodiment)>
(1) Backlight System FIG. 5 is a schematic side view of a liquid crystal display device (second embodiment) on which a light guide plate (resin sheet) according to an embodiment of the present invention is mounted. FIG. 6 is a schematic plan view of the backlight system of FIG. FIG. 7 is a schematic rear view of the backlight system of FIG. FIG. 8 is a diagram illustrating a modification of the dot pattern of the light guide plate.

The liquid crystal display device 21 (liquid crystal television) is a so-called edge-type liquid crystal display device, and includes a backlight system 22, a liquid crystal panel 23 disposed in front of the backlight system 22, the backlight system 22, and the liquid crystal panel 23. And an optical film 24 disposed therebetween.
In FIG. 5, the liquid crystal display device 21 is shown in a posture with the front side facing the upper side of the drawing for the sake of convenience. Further, the scales of the constituent members such as the liquid crystal display device 21, the backlight system 22, and the liquid crystal panel 23 shown in the following drawings are set for convenience of explanation, and the scales of all the constituent members are the same. Not that. Further, in the following description, as shown in FIGS. 5 to 8, the arrangement direction of the backlight system 22 and the liquid crystal panel 23 is referred to as a z direction (plate thickness direction), which are two directions orthogonal to the z direction. Two directions orthogonal to each other are referred to as an x direction and a y direction.

The backlight system 22 includes a light guide plate (optical sheet) 25 and a point light source (LED light source) 27 arranged to face the side surface 26 of the light guide plate 25.
The point light source 27 functions as a point light source of the backlight system 22 and faces the side surfaces 26 and 26 extending in the y-axis direction of the light guide plate 25 as shown in FIGS. 6 and 7. Several are arranged. The plurality of point light sources 27 are discretely arranged along the longitudinal direction (y-axis direction) of the side surface 26. The arrangement interval of the point light sources 27 is usually 5 mm to 20 mm. The point light source 27 may be disposed so as to face the four sides of the light guide plate 25, on two sides facing the x-axis direction (see FIGS. 6 and 7) and on two sides facing the y-axis direction. It may be arranged and may be arranged only on one side (see FIG. 8).

Further, the point light source 27 is not limited to the LED light source, and may be other point light sources. Furthermore, instead of the point light source 27, a linear light source (a cold cathode tube or the like) may be disposed.
Further, the point light source 27 may be a white LED, and a plurality of LEDs may be arranged at one place to constitute one light source unit. For example, as one light source unit, LEDs of three colors different in red, green, and blue may be arranged close to each other. And the light source unit which has several LED is discretely arrange | positioned according to the arrangement | positioning direction mentioned above. In such a case, it is preferable that different LEDs are arranged as close as possible.

As the LED light source used as the point light source 27, those having various light emission distributions can be used, but the luminous intensity in the normal direction (z-axis direction) of the LED light source is maximum, and the half-value width of the luminous intensity distribution is What has the light emission distribution which is 40 degree | times or more and 80 or less is suitable. Specific examples of the LED light source type include a Lambertian type, a shell type, and a side emission type.
(2) Liquid Crystal Panel The liquid crystal panel 23 includes a liquid crystal cell 28 and a pair of polarizing plates 29 and 30 that sandwich the liquid crystal cell 28 from both sides in the thickness direction. Such a liquid crystal panel 23 is arranged on the front surface of the backlight system 22 so that the polarizing plate 29 on the back side and the light guide plate 25 face each other.

As the liquid crystal cell 28, for example, a known liquid crystal cell such as a TFT liquid crystal cell or an STN liquid crystal cell can be used.
(3) Optical film The optical film 24 is not particularly limited, and examples thereof include a microlens film, a substantially semicircular lenticular lens film, a diffusion film, a prism film, and a reflective polarization separation film.
(4) Light Guide Plate As shown in FIGS. 6 and 7, the light guide plate 25 has a rectangular shape, and the size of the plan view shape is selected so as to match the target screen size of the liquid crystal panel 23. As for the screen size of the light guide plate 25, for example, the length of two orthogonal sides (L1 × L2) is preferably a large size of usually 250 mm × 440 mm or more, preferably 500 mm × 800 mm or more. The planar view shape of the light guide plate 25 is not limited to a rectangle, but may be a square.

The light guide plate 25 is formed of a translucent resin that transmits light and has a plate shape. The light guide plate 25 may be a sheet or a film. The thickness T of the light guide plate 25 is preferably 1.0 mm or greater and 4.5 mm or less.
The light guide plate 25 includes a pair of main surfaces (31, 32) facing in the z-axis direction (thickness direction), a pair of side surfaces 26, 26 facing in the X-axis direction, and a pair of side surfaces 33 facing in the Y-axis direction. 33 is provided. The main surfaces (31, 32) are formed in a direction intersecting with the side surfaces (26, 33).

One main surface (31) of the pair of main surfaces facing each other in the z-axis direction functions as an emission surface 31 capable of emitting planar light. The emission surface 31 is disposed on the liquid crystal panel 23 side, and the other main surface (back surface 32) is disposed on the side opposite to the liquid crystal panel 23. In addition, a reflection sheet 34 that reflects light in the light guide plate 25 toward the emission surface 31 is provided at a position facing the back surface 32.
Referring to FIG. 6, a plurality of ridges 35 that are convex outward in the z-axis direction are formed on the emission surface 31 of the light guide plate 25. The ridges 35 extend in the x-axis direction (one direction) and are arranged in parallel in the y-axis direction.

  In addition, examples of the shape of the ridge portion 35 include a prism shape, a semicircular shape, and a semi-elliptical shape, and a shape that continuously changes in one ridge portion 35 (shape unit) is preferable. A semicircular shape or a semi-elliptical shape is preferable to a prism shape. In addition, it is preferable that the direction where the protruding line part 35 extends is parallel to the light emission direction from the light source. Further, in the direction in which the ridges 35 are adjacent (y-axis direction), a plane portion may be formed between the adjacent ridges 35, 35.

  The distance (pitch P ′) between the centers of the adjacent ridge portions 35 is, for example, 200 μm to 500 μm, similar to the light diffusion plate 10 described above. Further, the height H ′ of the ridge 35 is, for example, 100 μm to 500 μm. Moreover, the aspect ratio represented by the ratio (H '/ P') of the height H 'to the pitch P' of the ridge 35 is, for example, 0.4 or more, preferably 0.5 to 0.7. is there.

  On the other hand, referring to FIG. 7, the back surface 32 of the light guide plate 25 is subjected to reflection processing (for example, silk printing) for irregularly reflecting light. As a printing method performed as reflection processing, ink jet printing may be performed in addition to silk printing. Or as a method of reflection processing, you may give a dot-shaped unevenness | corrugation by laser irradiation instead of printing. In the light guide plate 25 of the present embodiment, a dot pattern formed by collecting a plurality of dots 36 is printed as reflection processing. In printing dot patterns, ink having diffusing particles that diffuse light is used.

  Further, the gradation of each dot 36 (printing dot) constituting the dot pattern is changed so as to increase as the distance from the point light source 27 side increases. For example, the diameter of the dot 36a in the region near the side that is a region near the point light source 27 is about 516 μm, and the diameter of the dot 36b in the region near the center of the panel that is the farthest region from the point light source 27 is The diameter of the dot 36c in the intermediate region between them is about 729 μm.

  The diameter of each dot 36 is, for example, in a region close to the point light source 27 when the point light source 27 is disposed on only one side of the side surface 26 of the light guide plate 25 as shown in FIG. The diameter of the dot 36a in the area near one side of a panel is about 516 μm, and the diameter of the dot 36b in the area near the opposite side of the panel, which is the area farthest from the point light source 27, is about 904 μm. The diameter of the dot 36c in the intermediate area between them is about 729 μm.

  The light guide plate 25 is made of a translucent resin. The refractive index of the translucent resin is usually 1.49 to 1.59. As the translucent resin used for the light guide plate 25, methacrylic resin is mainly used. As the translucent resin used for the light guide plate 25, other resins may be used, or a styrene resin may be used. As the translucent resin, acrylic resin, styrene resin, carbonate resin, cyclic olefin resin, MS resin (acrylic and styrene copolymer), and the like can be used.

In applying the light guide plate 25 to the liquid crystal display device 21, additives such as a light diffusing agent, an ultraviolet absorber, a heat stabilizer, and a photopolymerization stabilizer may be added to the light guide plate 25.
<Production method of light diffusion plate or light guide plate (resin sheet)>
The light diffusion plate 10 or the light guide plate 25 described above can be produced by cutting a resin sheet produced by the following method.

FIG. 9 is a schematic configuration diagram of a manufacturing apparatus used in the method for manufacturing a resin sheet according to an embodiment of the present invention. FIG. 10 is an enlarged perspective view of the upper roll and the intermediate roll. FIG. 11 is an enlarged cross-sectional view of a main part of the intaglio transfer mold attached to the intermediate roll.
The sheet manufacturing apparatus 51 takes out the resin sheet 53, a sheet molding machine 52 that extrudes the raw material resin into a sheet shape, a set of pressing rolls 54 for molding the extruded resin sheet 53 by pressing. And a pair of take-up roll groups 55.

The sheet forming machine 52 is configured by a known extruder such as a single screw extruder or a twin screw extruder. The sheet molding machine 52 includes a cylinder 56 for heating and melting (softening) the resin material, a hopper 57 for feeding the resin material into the cylinder 56, and a die 58 for extruding the softened resin material in the cylinder 56. Including.
As the die 58, a metal T die used for a normal extrusion molding method or the like is used. As shown in FIG. 10, the width W of the lip (die lip 59) of the die 58 is selected according to the width of the target resin sheet 53, and is, for example, 300 mm to 3000 mm. The gap t of the die lip 59 is, for example, 4 mm to 8 mm. The resin sheet 53 is pushed out of the die 58 with substantially the same thickness as the gap t and sent to the pressing roll group 54.

The sheet forming machine 52 is disposed so that the gap t of the die lip 59 faces a gap A between an upper roll 63 and an intermediate roll 64 described later.
The press roll group 54 includes three press rolls 63 to 65 as a mechanism for forming irregularities on the front and back surfaces 75 and 76 of the resin sheet 53 by a transfer mold while molding the resin sheet 53 by pressing.

  The surface 76 of the resin sheet 53 is a surface that forms the back surfaces 18 and 32 of the light diffusing plate 10 or the light guide plate 25, and is a surface that is not finally subjected to shape processing (for example, in this embodiment, the flatness is low). Maintained flat surface). On the other hand, the back surface 75 of the resin sheet 53 is a surface that forms the emission surfaces 16 and 31 of the light diffusion plate 10 or the light guide plate 25, and is a shape transfer surface that is finally subjected to shape processing.

  Each of the three pressing rolls 63 to 65 is a cooling roll having a function of adjusting the temperature (surface temperature) of its peripheral surface, which is made of a cylindrical metal (for example, stainless steel, steel, etc.) roll. The three pressing rolls 63 to 65 are arranged so that the axes thereof are parallel to each other as the upper roll 63 as the first pressing roll, the intermediate roll 64 as the second pressing roll, and the lower roll 65 in order from top to bottom. Are arranged vertically. Between each of the pressing rolls 63 to 65, a gap A and a gap B are provided for sandwiching and winding the resin sheet 53 between the pair of pressing rolls.

  The gap A is a space defined by the lower end of the peripheral surface 66 of the upper roll 63 and the upper end of the peripheral surface 67 of the intermediate roll 64 (projection strips 71 of an intaglio transfer mold 69 described later), while the gap B is A space defined by the lower end of the peripheral surface 67 of the intermediate roll 64 and the upper end of the peripheral surface 68 of the lower roll 65. Since the axes of the three pressing rolls 63 to 65 are all parallel, the widths of the gaps A and B (the distance between the pressing rolls) are both constant along the axial direction of the pressing rolls 63 to 65.

The gap A is, for example, in a range of 0.95 × thickness T to 1.05 × thickness T, where T is the total thickness of the final form of the resin sheet 53 (the form of the light diffusion plate 10 or the light guide plate 25). Is set.
On the other hand, the gap t of the die lip 59 with respect to the gap A is set in a range of 1.5 × gap A to 5.0 × gap A.
By setting the gap A and the gap t of the die lip 59 within the above range and further adjusting the take-up speed of the resin sheet 53, the amount of resin discharged from the die lip 59, the temperature of the die 58, etc. The thickness can be made uniform over the entire width of the resin sheet 53.

  On the other hand, when the melt bank 73 near the entrance of the gap A disappears, the resin cannot be pressed by the upper roll 63 and the intermediate roll 64, and there is a possibility that appearance defects such as bank omission and transfer defects may occur. Therefore, in this case, the height h of the melt bank 73 is set to 1.0 × gap A by appropriately adjusting the take-up speed of the resin sheet 53, the discharge amount of the resin from the die lip 59, the temperature of the die 58, and the like. <Control is performed so as to satisfy the expression of height h ≦ 1.1 × gap A.

In this embodiment, the peripheral surface 66 of the upper roll 63 and the peripheral surface 68 of the lower roll 65 are formed into smooth surfaces (mirror surfaces) by, for example, mirror finishing.
On the peripheral surface 67 of the intermediate roll 64, an intaglio transfer die 69 for forming the ridges 17 and 35 and the concave groove 19 in the resin sheet 53 is provided. The intaglio transfer mold 69 is copper plated on a cylindrical metal roll, the plated metal roll is placed on a lathe, and a diamond bite is used to engrave the copper plated layer into a target lens shape. After forming a groove by chemical etching or the like, a copper plating process is performed on copper.

In order to form a more precise shape with good reproducibility, a lathe-diamond bit combination is preferred, and the chromium plating thickness applied on copper is preferably 5 μm or less, more preferably 2 μm or less.
As shown in FIG. 11, the intaglio transfer die 69 is formed with a plurality of concave grooves 70 as grooves opposite to the ridges 17 and 35 in a streak shape along the circumferential direction of the intermediate roll 64. Yes. In other words, the intaglio transfer mold 69 has a protrusion 71 between the indentation groove 70 and the adjacent indentation groove 70 (this protrusion 71 is opposite to the indentation groove 19 and is referred to as the surface of the intaglio transfer mold 69). Is the surface of the ridge 71.) are alternately arranged along the axial direction of the intermediate roll 64.

The concave groove 70 has a substantially semi-elliptical outline in a cut surface perpendicular to the longitudinal direction (circumferential direction). The depth H of the concave groove 70 is slightly larger than the height H ′ of the ridges 17 and 35, and is, for example, 100 μm to 500 μm, preferably 100 μm to 300 μm or less. If the depth H is excessively large, it is difficult to allow the resin to enter the tip of the groove 70.
Moreover, although the distance (pitch P) between the centers of the adjacent ditch | grooves 70 is suitably determined according to the shape of the protruding item | line parts 17 and 35, for example, 200 micrometers-500 micrometers, Preferably, they are 250 micrometers-450 micrometers, More preferably , 300 μm to 400 μm. If the pitch P is less than 200 μm, the resin may solidify immediately upon contact with the intermediate roll 64, and as a result, the resin does not enter the tip of the concave groove 70 and a target transfer shape cannot be obtained. There is a fear. On the other hand, when the pitch P exceeds 500 μm, pitch streaks are observed with the naked eye on the back surfaces 18 and 32 of the light diffusion plate 10 or the light guide plate 25, and the liquid crystal panels 3 and 23, the optical films 4 and 24, etc. The moire pattern may appear.

Moreover, the aspect ratio represented by the ratio (H / P) of the height H with respect to the pitch P of the ditch | groove 70 is 0.4 or more, for example, Preferably, it is 0.5-0.7.
The difference between the height H ′ of the ridges 17 and 35 and the depth H of the groove 70 is that when the intaglio transfer mold 69 is transferred to the resin sheet 53 and the ridges 17 and 35 are formed. This is due to the transfer rate (H ′ / H) (%).

  Note that motors (not shown) are connected to the rotation shafts of the pressing rolls 63 to 65, respectively, so that the upper roll 63 and the lower roll 65 can rotate counterclockwise, and the intermediate roll 64 rotates clockwise. Is possible. That is, the pressing rolls 63 to 65 are “rotatable counterclockwise”, “rotatable clockwise”, and “rotatable counterclockwise” in order from the top. Thereby, all the rolls 63 to 65 can be rotated synchronously with the resin sheet 53 sandwiched therebetween. Moreover, the conveyance speed of the resin sheet 53 can be adjusted by adjusting the rotational speed of the press rolls 63-65 suitably.

The diameter of each pressing roll 63-65 is 100 mm-500 mm, for example. Moreover, when a metal roll is used as the pressing rolls 63 to 65, the surface thereof may be subjected to plating treatment such as chromium plating, copper plating, nickel plating, Ni-P plating, or the like.
The pair of take-up roll groups 55 includes a pair of take-up rolls 85 and 86 that sandwich the resin sheet 53 from both sides in the thickness direction.

  The take-up rolls 85 and 86 are each made of a cylindrical metal roll (for example, made of stainless steel or steel), so that the upper end of the lower take-up roll 85 is at the same height as the lower end of the lower roll 65. It is installed opposite. Thereby, since the resin sheet 53 delivered from the lower roll 65 can be horizontally conveyed while being supported at the height immediately after the delivery, the conveyance resistance can be reduced.

Next, a method for manufacturing the resin sheet 53 using the above-described manufacturing apparatus will be described.
(1) Extrusion Step First, the raw material resin is charged into the hopper 57 of the sheet forming machine 52, melted and kneaded by the cylinder 56, and then supplied to a feed block (not shown). The cylinder 56 temperature is set to 190 ° C. to 250 ° C., for example.

  Next, the resin in the feed block (not shown) is continuously extruded from the die 58 as the resin sheet 53 with the same thickness as the gap t of the die lip 59. The amount of resin discharged from the die 58 (discharge amount) can be appropriately changed in the range of 30 kg / hr to 1500 kg / hr depending on the width and thickness of the final product (resin sheet 53). Further, in order to change the discharge amount, if the change amount is twice or more, the apparatus must be significantly modified such as changing the screw diameter and screw design of the sheet forming machine 52. On the other hand, when the change amount is less than twice, it can be adjusted by changing the screw rotation speed of the sheet forming machine 52.

Moreover, the height h of the melt bank 73 can be sufficiently adjusted by finely adjusting the screw rotation speed. Moreover, about the temperature of the die | dye 58, you may confirm the height h of the melt bank 73 in the range of 200 degreeC-280 degreeC, and may have distribution in the width direction suitably. Generally, when the die temperature is lowered, the flowability of the resin is lowered, so that the melt bank becomes smaller. When the die temperature is raised, the flowability of the resin is raised, so that the meltbank becomes larger.
(2) First Pressing Step and Conveying Step The resin sheet 53 pushed out from the die 58 is fed into the gap A. Since the gap A is narrower than the gap t of the die lip 59, a part of the resin forming the resin sheet 53 does not enter the gap A and starts to blow upward along the peripheral surface 66 of the upper roll 63. On the other hand, it remains as a melt bank 73 (resin pool) that rises to the opposite side of the transfer roll (intermediate roll 64). The melt bank 73 is formed with a substantially uniform height h along the axial direction of the upper roll 63. The height h (the amount of rise from the back surface 75 of the resin sheet 53) is 1.1 times or less of the gap A. That is, 1.0A <h ≦ 1.1A.

  In order to measure the height h of the melt bank 73, for example, the upper roll 63 is pulled upward in a state where the melt bank 73 is formed, and the retained melt bank 73 is not brought into contact with the upper roll 63. So that it passes behind the gap A. Then, the height h of the melt bank 73 after passing (the distance from the back surface 75 of the resin sheet 53 to the top of the melt bank 73) is measured using a micrometer or the like.

  Thereafter, the resin staying as the melt bank 73 is sequentially fed into the gap A, and is sandwiched and pressed between the upper roll 63 and the intermediate roll 64. The surface temperature of the upper roll 63 and the intermediate roll 64 is preferably lower than the extrusion temperature of the resin sheet 53. For example, the surface temperature of the upper roll 63 is 40 ° C to 160 ° C, and the surface temperature of the intermediate roll 64 is 40 ° C to 170 ° C.

When the upper roll 63 and the intermediate roll 64 are pressed, the surface shape of the intaglio transfer mold 69 is transferred to the back surface 75 (the exit surfaces 16 and 31) of the resin sheet 53, so that the sheet flow direction (send-out) A plurality of strip-like ridges 17 and 35 parallel to (direction) are formed. Thereafter, the back surface 75 is brought into close contact with the peripheral surface 67 of the intermediate roll 64 and is then cooled from the back surface 75 side by the intermediate roll 64.
(3) Second pressing step Thereafter, the conveyed resin sheet 53 enters the gap B, and is sandwiched and pressed between the intermediate roll 64 and the lower roll 65. The surface temperature of the lower roll 65 is appropriately adjusted so that the temperature of the surface 76 of the resin sheet 53 immediately after peeling from the lower roll 65 (lower roll 65 outlet temperature) is, for example, near the glass transition temperature Tg of the raw material resin. . For example, when a polystyrene resin having a glass transition temperature Tg of 105 ° C. is used, the lower roll 65 is adjusted so that the lower roll 65 outlet temperature of the surface 76 is 110 ° C. (for example, 50 ° C. to 100 ° C.). .

Thereafter, the resin sheet 53 is fed out from the gap B and peeled off from the intermediate roll 64, and the surface 76 is conveyed in close contact with the peripheral surface 68 of the lower roll 65. At this time, in addition to cooling by the lower roll 65, the resin sheet 53 is also cooled from the back surface 75 side by blowing air from the blower 72 facing the back surface 75 (shape transfer surface) of the resin sheet 53.
Then, the resin sheet 53 is manufactured by being sent horizontally from the lower end of the lower roll 65 to the take-up roll group 55 and taken up by the pair of take-up rolls 85 and 86. Thereafter, after the resin sheet 53 is further cooled, the light diffusion plate 10 or the light guide plate 25 can be obtained by cutting the resin sheet 53 with an appropriate size.

In addition, the conveyance speed (take-off speed) of the resin sheet 53 is adjusted to 2.5 m / min or more, preferably 2.5 m / min to 10 m / min, for example.
(4) Operational Effects As described above, in this embodiment, the gap A is set in the range of 0.95 × thickness T to 1.05 × thickness T, and the gap t of the die lip 59 is 1.5 ×. By setting the gap A to 5.0 × gap A and adjusting the take-up speed of the resin sheet 53, the amount of resin discharged from the die lip 59, the temperature of the die 58, and the like, The thickness can be reduced to 1.1 times or less, and the entire width of the resin sheet 53 can be made uniform. Thereby, the resin staying in the vicinity of the entrance of the gap A can be sequentially sent out to the gap A before the passage of a long time after the stay (that is, before being cooled and solidified by the upper roll 63 and the intermediate roll 64). . Therefore, the molten resin fed into the gap A can be satisfactorily entered into the concave groove 70 of the intaglio transfer mold 69. Therefore, the intaglio transfer mold 69 can be accurately transferred to the back surface 75 of the resin sheet 53. Therefore, the light diffusion plate 10 or the light guide plate 25 made of the resin sheet 53 can exhibit optical characteristics as designed.

That is, by using the manufacturing method disclosed in this embodiment, a prism shape having a high degree of difficulty, which has been difficult to transfer by a conventional manufacturing method, a high H / P ratio (0.5 or more), a narrow pitch shape ( The transfer rate can be improved with high accuracy even for 300 μm or less.
Further, since the upper bank 63 and the intermediate roll 64 are formed after the melt bank 73 is formed, the surface smoothness and thickness uniformity of the resin sheet 53 can be maintained.

Furthermore, by setting the conveyance speed of the resin sheet 53 to 2.5 m / min to 10 m / min, the residence time of the resin as the melt bank 73 can be made more appropriate, and the filling property of the resin into the concave groove 70 is improved. be able to.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented in other embodiment.

For example, instead of the intaglio transfer mold 69 having the substantially semi-elliptical groove 70, an intaglio transfer mold 77 having a semi-circular groove 78 having a substantially semicircular shape (cylindrical lens shape) shown in FIG. An intaglio transfer mold 79 having a prism groove 80 having a substantially prism shape (for example, a vertex angle θ of 60 ° to 120 °) shown in FIG.
In the above-described embodiment, the back surfaces 18 and 32 of the light diffusing plate 10 or the light guide plate 25 are flat surfaces without unevenness. For example, the mat surface has fine unevenness after being embossed or the like. It may be. In that case, the surface 76 of the resin sheet 53 may be embossed. In order to emboss the surface 76 of the resin sheet 53, for example, in the manufacturing apparatus 51 for the resin sheet 53, an embossed transfer mold may be wound around the peripheral surface 68 of the lower roll 65, and the transfer mold may be transferred. .

Further, in the above-described embodiment, the press roll group 54 is configured such that the upper roll 63, the intermediate roll 64, and the lower roll 65 are arranged side by side in the vertical direction. The form arrange | positioned along with a direction may be sufficient.
Further, for example, a roll (touch roll) in contact with the resin sheet 53 and the intaglio transfer mold 69 is provided as long as the roll is irrelevant in terms of transfer technology for assisting conveyance or adhesion between the resin sheet 53 and the pressing rolls 63 to 65. May be.

Further, for example, the light diffusing plate or the light guide plate (resin sheet) is not limited to a single layer resin plate such as the light diffusing plate 10 or the light guide plate 25. For example, a two-layer resin plate or a three-layer resin plate It may be a multi-layer resin plate composed of four or more layers.
Moreover, although the light diffusing plate 10 or the light guide plate 25 is suitably used as a light diffusing plate or a light guide plate for backlight, it is not particularly limited to such an application.

The backlight systems 2 and 22 are preferably used as a surface light source device for a liquid crystal display device, but are not particularly limited to such applications.
In addition, various design changes can be made within the scope of matters described in the claims.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.
<Raw material of resin sheet>
The following materials (1) and (2) were prepared as raw materials for the resin sheet.
(1) Amorphous resin A: heat-resistant styrene resin (“T080” manufactured by Toyo Styrene Co., Ltd., MFR: 1.3 g / 10 min)
(2) Amorphous resin B: Acrylic resin (“SUMIPEX EXN” manufactured by Sumitomo Chemical Co., Ltd. MFR: 0.24 g / 10 min)
In addition, MFR of each material (1) and (2) was measured on 200 degreeC and 49 N load conditions.
<Configuration of resin sheet manufacturing apparatus>
The apparatus which has the structure similar to the resin sheet manufacturing apparatus shown in FIG. 9 was used.

In addition, the mirror surface cooling roll by which chromium plating was given to the surface was prepared as a press roll.
Further, a transfer mold A shown in Table 1 was prepared as a transfer mold to be attached to the pressing roll. In the transfer mold A, semi-elliptical groove portions are formed in parallel at equal intervals along the circumferential direction of the pressing roll. In Table 1, “Pitch P” and “Depth H” are values defined in the above-described embodiment.

<Examples and Comparative Examples>
(1) Examples 1-2 and Comparative Example 1
First, the amorphous resin A was supplied to an extruder having a screw diameter of 120 mm, melt-kneaded at a cylinder temperature of 210 ° C. to 250 ° C., and then supplied to a feed block.
Next, the resin in the feed block was extruded in a sheet form at a T die temperature of 260 ° C. to 280 ° C. through a T die having a width of 1500 mm. The discharge rate from the T die was 1000 kg / hr in Example 1 and Comparative Example 1, and 850 kg / hr in Example 2.

  After that, the extruded resin sheet is temporarily retained as a melt bank at the entrance of the gap between the upper roll (mirror cooling roll) and the intermediate roll (transfer mold mounting roll), and then sandwiched between the upper roll and the intermediate roll. It was conveyed in the state wound around the surface of the intermediate roll. And it pinched with the intermediate roll and the lower roll (mirror surface cooling roll), it conveyed in the state wound around the surface of the lower roll, and the resin sheet which peeled from the lower roll was taken up with the take-up roll. As a result, a surface shape transfer resin sheet having a concave shape transferred to the back surface (lower surface) was obtained. And the shape transfer rate T of the obtained resin sheet was calculated | required by the following formula | equation. The results are shown in Table 2. In the following formula, a replica refers to a resin sheet on which each transfer mold is transferred at a transfer rate of 100%.

  Shape transfer rate T (%) = depth of the groove portion of the resin sheet H ′ / depth of the groove portion of the replica H ″ × 100

(2) Example 3
First, the amorphous resin B is supplied to an extruder having a screw diameter of 120 mm, melt-kneaded at a cylinder temperature of 210 ° C. to 250 ° C., and then supplied to a feed block.
Next, the resin in the feed block is extruded into a sheet shape at a T die temperature of 260 ° C. to 280 ° C. via a T die having a width of 1500 mm. The discharge rate from the T die is 1000 kg / hr.

  After that, the extruded resin sheet is temporarily retained as a melt bank at the entrance of the gap between the upper roll (mirror cooling roll) and the intermediate roll (transfer mold mounting roll), and then sandwiched between the upper roll and the intermediate roll. Then, it is conveyed while being wound around the surface of the intermediate roll. And it sandwiches with an intermediate roll and a lower roll (mirror surface cooling roll), conveys in the state wound around the surface of the lower roll, and takes up the resin sheet which peeled from the lower roll with the take-up roll.

  In Example 3, the height of the melt bank with respect to the gap A of the gap between the upper roll and the intermediate roll is set to 1.05 times (the height of the melt bank = 1.05 × A). As a result, a surface shape transfer resin sheet having a concave shape transferred to the back surface at a high shape transfer rate is obtained.

53 Resin sheet 58 Die 63 Upper roll 64 Intermediate roll 67 (Intermediate roll) peripheral surface 69 Intaglio transfer mold 70 Concave groove 73 Melt bank 77 Intaglio transfer mold 78 Semicircular concave groove 79 Intaglio transfer mold 80 Prism concave groove A (Upper roll) And the intermediate roll) h Melt bank height

Claims (7)

An extrusion process in which a resin is continuously extruded from a die in a heated and melted state to produce a continuous resin sheet;
A pressing step of sandwiching the continuous resin sheet between the first pressing roll and the second pressing roll;
A transporting step of transporting the continuous resin sheet in close contact with the second pressing roll after the pressing step;
The second pressing roll has a transfer mold on its surface,
In the pressing step, a melt bank having a height not more than 1.1 times the gap A between the first pressing roll and the second pressing roll is interposed between the first pressing roll and the second pressing roll. The manufacturing method of the surface shape transfer resin sheet including the process to form.   The manufacturing method of the surface shape transfer resin sheet of Claim 1 whose conveyance speed of the said continuous resin sheet is 2.5 m / min or more.   The method for producing a surface shape transfer resin sheet according to claim 1 or 2, wherein the resin is an amorphous resin.   4. The surface shape transfer resin sheet according to claim 3, wherein the amorphous resin contains a styrene resin, an acrylic resin, an acrylic / styrene copolymer resin, a cyclic olefin resin, or a polycarbonate resin as a main component. Method. The transfer mold has grooves formed in a plurality of streaks along the circumferential direction of the second pressing roll,
5. The method for producing a surface shape transfer resin sheet according to claim 1, wherein an interval (pitch P) between the adjacent groove portions is 200 μm to 500 μm, and a depth H of the groove portion is 100 μm to 500 μm.   6. The method for producing a surface shape transfer resin sheet according to claim 5, wherein an aspect ratio represented by a depth H of the groove portion / a pitch P of the groove portion is 0.4 or more.   The method for producing a surface shape transfer resin sheet according to claim 5 or 6, wherein a cross-sectional shape in a direction orthogonal to the longitudinal direction of the groove portion is a substantially semicircular shape, a substantially semielliptical shape, or a substantially prism shape.

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