JP2012234083A - Method for manufacturing light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a light guide plate capable of processing the end surface of an original light guide plate with high accuracy, where the conventional manufacturing method of processing the end surface of each original light guide plate using a rotating cutter blade has bad positioning accuracy and difficulty of high accuracy processing resulting from warpage, waviness or the like of the original light guide plates.SOLUTION: The manufacturing method comprises a series of works of: bundling a plurality of basic light guide plates or original light guide plates; cutting each bundled basic light guide plate or each bundled original light guide plate; polishing and processing the end surfaces thereof.

Description

  The present invention relates to a method of manufacturing a light guide plate used for a backlight for a liquid crystal display device and a lighting device used in a liquid crystal television, a liquid crystal monitor, a personal computer, and the like.

  As a backlight of a liquid crystal display device or a lighting device, for example, a light source such as an LED light source is disposed on the side of a light guide plate (referred to as an “end face” or an “edge”), and light from the LED light source is all transmitted. It is known that the inside of the light guide plate is guided by reflection, and the light is uniformly emitted from the front surface of the light guide plate by being reflected by a dot pattern or a prism portion formed on the back surface of the light guide plate (for example, , See Patent Document 1).

  As a method for manufacturing such a light guide plate for backlight, the end face (edge) of the light guide plate original plate is processed into a desired shape such as a prism shape for the purpose of improving the brightness of the backlight and improving the brightness uniformity. It has been proposed to produce a light guide plate.

  And as a method of processing and manufacturing, a method of manufacturing a light guide plate having a desired shape on its end face by using injection molding (for example, refer to Patent Document 2), or rotating one light guide plate original plate at a time. A method (for example, refer to Patent Document 3) in which an end face is processed and manufactured using a cutter blade is proposed.

Japanese Patent Application Laid-Open No. 2001-075522 JP 2008-010291 A JP 2002-169032 A

  However, injection molding is not economical because the mold is expensive. In addition, in the case of a manufacturing method in which each end plate of the light guide plate is processed using a cutter blade whose end face is rotated, the positioning accuracy is poor due to warpage or waviness of the light guide plate, and high accuracy processing is difficult. It was.

  Accordingly, an object of the present invention is to provide a method of manufacturing a light guide plate that can perform highly accurate processing on an end surface of a light guide plate original plate.

  The present invention has been made in view of such a technical background, and the inventor has intensively studied a method for manufacturing a light guide plate, and as a result, has completed the present invention.

  That is, the present invention provides the following [1] to [9].

[1] A method of manufacturing a light guide plate in which a plurality of light guide plate original plates are bundled and then processed into end surfaces of the bundled light guide plate original plates.
[2] After bundling a plurality of light guide plate base plates or light guide plate original plates, a series of operations including bundling each light guide plate base plate or master plate cutting of each light guide plate original plate, end face polishing, and processing to end faces [1] The production method according to [1].
[3] The manufacturing method according to [1] or [2], in which end surfaces of the bundled light guide plate originals are collectively processed.
[4] The manufacturing method according to any one of [1] to [3], wherein the processing on the end face is formation of a groove on the end face, and the groove is a groove in a direction parallel to the surface of the light guide plate original plate. .
[5] The manufacturing method according to any one of [1] to [3], wherein the processing on the end face is formation of a groove on the end face, and the groove is a groove in a direction parallel to the thickness direction of the light guide plate original plate. .
[6] In any one of [1] to [3], the processing to the end face is a process of forming a plurality of uneven portions on the end face of each light guide plate original plate using a mold having a plurality of protrusions. The manufacturing method as described.
[7] As described in any one of [1] to [6], the end surface of the light guide plate original plate is processed by curing the ultraviolet curable resin by ultraviolet irradiation using a mold and the ultraviolet curable resin. Production method.
[8] The production method according to [7], wherein the method is performed from an end surface opposite to the end surface on which ultraviolet irradiation is shaped.
[9] The manufacturing method according to any one of [1] to [3], in which the processing on the end surface forms a pattern by printing on the end surface.

The manufacturing method of the present invention can reduce warpage during processing even when the light guide plate is thin and easily warps, or even a light guide plate originally having a slight warpage, and is stable. Since the light guide plate can be held, the shaping process can be performed with high accuracy. In addition, the light guide plate original plate is cut out, end-face polished, and shaped into the end face in a series of operations, that is, by not separating the bundle of light guide plates between each operation, Since it is not necessary to align (align the edge position), the machining accuracy can be increased and the work efficiency is also improved.
Irrespective of the type of mold, the ultraviolet curable resin can be irradiated with ultraviolet rays. A highly accurate groove shape can be produced.

The figure which shows one Embodiment of the light-guide plate manufactured with the manufacturing method of this invention. The figure which shows one Embodiment of the manufacturing method of this invention. The figure which shows one Embodiment of the light-guide plate manufactured with the manufacturing method of this invention. The figure which shows one Embodiment of the light-guide plate manufactured with the manufacturing method of this invention. The figure which shows the grinding | polishing method of the end surface of the light-guide plate original plate which concerns on one Embodiment of the manufacturing method of this invention. The figure which shows one Embodiment of the manufacturing method of this invention. The figure which shows one Embodiment of the manufacturing method of this invention.

  The light guide plate manufacturing method of the present invention is characterized in that a light guide plate original plate is bundled and shaped on an end surface.

Hereinafter, the present invention will be described in detail. This manufacturing method includes at least a step of bundling a plurality of light guide plate original plates, and a step of processing the end surfaces of the bundled light guide plate original plates. Hereinafter, it demonstrates in order for every process.
In the present invention, the plate obtained by subjecting the end face processing to the “light guide plate”, the plate before the end face processing to the “light guide plate original plate”, and the plate before cutting out the light guide plate original plate of a predetermined size It will be referred to as a “light guide plate base plate”.

  As the light guide plate original plate before processing of the light guide plate produced by the production method of the present invention, a plate made of a transparent resin usually formed into a plate shape is used. Examples of the transparent resin include methacrylic resin (PMMA, etc.), polycarbonate resin, ABS resin (acrylonitrile-styrene-butadiene copolymer resin), MS resin (methyl methacrylate-styrene copolymer resin), polystyrene resin, AS resin ( Acrylonitrile-styrene copolymer resin), polyolefin resin (polyethylene, polypropylene, etc.), and cyclic polyolefin.

  As a method for producing the light guide plate base plate by molding the resin into a plate shape, the following method can be usually used industrially. Melt extrusion method: Transparent resin material is melt-extruded using an extruder, and at least one side of a sheet-like material that can be discharged from a die is brought into contact with a roll or belt to form a sheet-like base plate. It is a method to do. Cast polymerization method: Mixing a monomer composition containing a monomer component and a polymerization initiator, and then injecting the two glasses into a cell facing each other through a spacer, further heating or ultraviolet irradiation In this method, the initiator is activated by a technique such as polymerization to obtain a sheet-like molded body, and a light guide plate base plate is manufactured. Press molding; a method for producing a light guide plate base plate by molding a transparent resin material into a plate shape using a heating press device. Of course, the original plate obtained by injection molding may be used for further end face processing.

  The shape given to the end face of the light guide plate is selected mainly for the purpose of reducing the light leaking from the end face or controlling the direction of the light reflected by the end face.

  For example, the shape on the end surface is the formation of a groove on the end surface, and the groove is a shape in a direction parallel to the surface (outgoing surface) of the original light guide plate (FIG. 1). Examples of the cross-sectional shape of the convex portion formed by the groove include a triangular prism having an apex angle of 90 degrees and a prism whose direction is parallel to the exit surface. With this shape, leakage of light from the edge can be suppressed. The apex angle of the triangular prism is usually in the range of 45 degrees to 120 degrees, and preferably 60 degrees to 100 degrees. The side length of the triangular prism is usually in the range of 10 μm to 1 mm, and preferably in the range of 30 μm to 500 μm.

  Further, for example, the shape on the end face is the formation of a groove on the end face, and the groove is a groove in a direction parallel to the thickness direction of the light guide plate original plate (perpendicular to the exit face) (FIG. 3). As a cross-sectional shape of the convex portion formed by the groove, a shape that is a triangular prism having an apex angle of 90 degrees can be given. The in-plane spread can be adjusted by this shape. The apex angle of the prism and the bottom of the groove may be rounded. The apex angle of the triangular prism is usually in the range of 45 degrees to 120 degrees, and preferably 60 degrees to 100 degrees. The side length of the triangular prism is usually in the range of 10 μm to 1 mm, and preferably in the range of 30 μm to 500 μm.

  The shaping on the end face may be a three-dimensional structure such as a cone, a quadrangular pyramid, or a part of a sphere, instead of the two-dimensional linear groove as described above (FIG. 4).

Hereafter, each process is demonstrated (FIG. 5).
First, the original light guide plate is bundled. The following method can be mentioned as a method of bundling. They may be simply stacked (especially in the case of flat placement), and in the case of flat placement, they may be pressed by placing a heavy object from above. Moreover, the method of using a vise, the method of using a string or a belt, and the method of screwing in a container are mentioned. Flatness may be ensured by placing a highly rigid metal plate or glass plate on both sides of the outside and placing a bundle of light guide plates.

  The thickness after being bundled is usually 10 mm or more, preferably 20 mm or more, more preferably 50 mm or more. The thicker one can obtain higher fixability and stability, so that highly accurate processing can be performed. However, if it exceeds 500 mm, handling becomes difficult.

  The process of cutting out the light guide plate original plate from the original plate can be performed using an electric saw, a laser cutter, or a cutting method using a frame-shaped mold if the thickness is thin.

  You may grind | polish the end surface of a light-guide plate original plate before shaping. As a polishing method, for example, a general sandpaper can be used. The sandpaper to be used is usually 400 or more. Depending on the roughness of the end face of the light guide plate original plate, rough polishing may be first performed at 320 to 600 and finish polishing may be performed at 800 to 1200.

  In order to perform processing with higher accuracy, a method that can obtain high smoothness is desirable, and polishing or buffing using an abrasive may be performed. Preferably, when an end face finishing machine for a light guide plate using a diamond blade is used, a simple and good end face can be obtained efficiently.

  Shaping can be performed in various ways. Examples of the shaping method include a photopolymer method (ultraviolet curable resin), a hot embossing method, grinding, cutting, and the like.

As a shaping method, a method of shaping with an ultraviolet curable resin and a mold can be used.
As the ultraviolet curable resin, a commercially available ultraviolet curable resin such as urethane acrylate can be used.

  As the type of the mold, a general mold shaped by various methods can be used. A steel plate with copper plating, cut with a diamond bite, a master mold having a desired shape, a master mold transferred by a so-called electroforming method, a commercially available A shaped film such as a prism sheet can also be used.

  In the case of using an opaque mold such as metal, the curing method (light application method) is to apply an ultraviolet curable resin to the shaping end surface of the light guide plate base plate and bring the mold into contact with the ultraviolet curable resin. When light is irradiated from the end surface opposite to the end surface of the light guide plate original plate, the light propagates inside the light guide plate and is irradiated to the ultraviolet curable resin, and the ultraviolet curable resin is cured, and is applied to the end surface of the light guide plate original plate. It can be shaped (Figure 2). A light guide plate having sufficient transparency with respect to the absorption wavelength of the photoinitiator is required. When using a transparent mold (transparent to the absorption wavelength of the photoinitiator), light may be irradiated from the mold side. Examples of the transparent mold include those in which a shape opposite to the desired uneven shape is imparted to the transparent resin substrate film.

  Examples of other methods include a method of directly forming a groove with a blade (FIG. 6) and hot embossing.

  Printing can be performed instead of shaping processing such as grooving (FIG. 7). For the purpose of reducing light leaking from the edge, it may be painted white, for example. You may give a dotted | punctate, linear, or strip | belt-shaped pattern with a white paint.

  When screen printing is used, a method of screen printing white ink (a transparent acrylic resin with a filler such as silica or titanium oxide added) using a screen plate having an appropriate mesh size may be used.

  As the printing pattern, an appropriately adjusted pattern may be used in consideration of optical characteristics, such as a dot pattern with a controlled size and density, a line pattern with a controlled line width and line density, and a white fill on the entire surface. it can.

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

Example 1
PMMA (polymethyl methacrylate) (“SUMIPEX EXN” manufactured by Sumitomo Chemical Co., Ltd.) was melt-kneaded with a single screw extruder having a screw diameter of 40 mm and extruded from a T die at a resin temperature of 255 ° C. A 250 mm original plate is manufactured.

  The obtained original plate is cut into a size of 200 mm wide × 400 mm long to produce a light guide plate original plate, and 15 obtained light guide plate original plates are stacked. In a state fixed with a vise, the four side surfaces (end surfaces) are polished with a polishing machine (“Pura Beauty 1000” manufactured by Asahi Megaro Co., Ltd.) to produce a polished light guide plate original plate.

  A bundle of the obtained light guide plate original plates is installed as shown in FIG. 5, and an end surface to be shaped is directed upward, and an ultraviolet curable resin is applied to the upper end surface to a thickness of about 30 μm using a bar coater.

  From above, a metal mold (a metal metal mold having a prism groove (pitch 50 μm, apex angle 90 degrees, extending in parallel to the emission surface)) is applied. The ultraviolet curable resin is cured by irradiating ultraviolet rays from the end surface on the opposite side (lower side) of the shaping end surface. When the mold is removed, an end surface having a prism structure is obtained.

Claims (9)

A method for manufacturing a light guide plate, in which a plurality of light guide plate original plates are bundled and then processed into end surfaces of the bundled light guide plate original plates.   After bundling a plurality of light guide plate base plates or light guide plate base plates, a request is made for a series of operations to cut each bundled light guide plate base plate or each light guide plate base plate, end face polishing, and end face processing. Item 2. The production method according to Item 1.   The manufacturing method of Claim 1 or 2 which processes collectively on the end surface of each said light-guide plate original plate bundled.   The manufacturing method according to claim 1, wherein the processing on the end surface is formation of a groove on the end surface, and the groove is a groove in a direction parallel to the surface of the light guide plate original plate.   The manufacturing method according to any one of claims 1 to 3, wherein the processing on the end face is formation of a groove on the end face, and the groove is a groove in a direction parallel to the thickness direction of the light guide plate original plate.   The manufacturing method according to any one of claims 1 to 3, wherein the processing to the end face is a process of forming a plurality of uneven portions on the end face of each light guide plate original plate using a mold having a plurality of protrusions.   The manufacturing method as described in any one of Claims 1-6 which harden and process this ultraviolet curable resin by ultraviolet irradiation using the metal mold | die and ultraviolet curable resin to the end surface which processes a light-guide plate original plate.   The manufacturing method of Claim 7 performed from the end surface on the opposite side to the end surface which shapes ultraviolet irradiation.   The manufacturing method according to any one of claims 1 to 3, wherein the patterning is performed on the end face by printing on the end face.