JP2007066699A - Light guide plate and manufacturing method of the light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate capable of providing high-accuracy diffused light, without having to increase the size of a manufacturing facility. <P>SOLUTION: This light guide plate has an emitting surface and a reflecting surface, facing each other of a plate-like member and is so structured that light rays introduced from a light source are reflected from the reflecting surface to the emitting surface; a resinous projecting surface is arranged on a surface of the emitting surface; and a planar distributed light rays are emitted from the emitting surface. The resinous projecting part can be formed accurately by printing method or the like, without increasing the size of a facility, and required diffused light can be provided by the difference of a refraction index of an interface surface or the like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light guide plate for spreading light from a light source over the entire light emitting surface and emitting light, and a method for manufacturing such a light guide plate.

  Recently, as a light source for a backlight of a liquid crystal display device, a light emitting diode element (LED) or a cold cathode tube is used to generate light, and light from the light emitting diode element or the cold cathode tube is emitted in a planar shape. The device is used. In such a surface light-emitting device, light-emitting diode elements and the like are usually arranged on one side surface of the light guide plate, and the light incident from the side surface is reflected by one main surface of the light guide plate and faces the opposite side. Ejected from the main surface. A plurality of dots for reflection are formed on one main surface of the light guide plate that performs reflection, and light incident from the side surface is reflected by the plurality of dots to the exit surface.

  Also, the light guide plate has a structure in which a prism sheet for scattering light from the light guide plate is provided on the exit surface side of the light guide plate, and further, a prism-shaped portion for exhibiting a light scattering function on one side or both sides of the light guide plate A light guide plate having a prism sheetless structure is also known. By the way, as a general method for manufacturing the above-described prism-shaped light guide plate, there is a method of injection-molding a thermoplastic resin such as an acrylic resin or a polycarbonate resin. This is a method in which a mold having a shape opposite to a desired prism shape is manufactured by precision machining and molded by a high pressure injection molding machine. A method of forming a prism shape by a process of forming a sheet by pressing a molten resin is also known (see, for example, Patent Document 1). In addition, the surface of the cylinder-shaped material (roller) is engraved with a fine and high-precision shape by cutting, and a resin surface that contacts the surface of the cylindrical-shaped material while transferring heat by placing a heater inside the cylindrical-shaped material There is also known a technique for manufacturing a light guide plate having a fine and high-definition prism shape by processing (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 9-11328 JP-A-11-147255

  However, forming the prism-shaped portion for scattering light by the method described above has caused the following problems. First, in the method of forming a prism shape by the process of pressing and molding molten resin into a sheet, a large press forming apparatus is required as equipment, and since it is in the form of a sheet, the necessary thickness as a light guide plate is secured. The problem is that it is not easy. In addition, a technology that forms a desired fine and high-definition prism shape by bringing a heat roller into contact with the surface of a thermoplastic resin heats a thermoplastic resin plate such as an acrylic resin, a polycarbonate resin, or a transparent vinyl chloride resin. The process is indispensable, and when the thermoplastic resin is heated, the refractive index of the resin changes due to distortion caused by heating, etc. Even if the prism shape as designed is obtained, the progress of the light beam does not proceed as designed Will occur.

  In view of the above technical problems, an object of the present invention is to provide a light guide plate that does not involve an increase in the size of manufacturing equipment and realizes high-precision light scattering.

  In order to solve the above technical problem, the light guide plate of the present invention has a light emitting surface and a reflective surface facing each other of a plate-like member, and the light beam introduced from the light source is directed from the reflective surface to the light emitting surface. In addition to being reflected, a resin convex portion is provided on the surface of the emission surface, and surface distribution light rays are emitted from the emission surface.

  According to the light guide plate of the present invention, the resin convex portion is disposed on the light exit surface of the light guide plate. The resin surface itself is not processed to form irregularities, but there is an interface between the plate-like member and the resin protrusion, and incident light incident at a required angle from the reflective surface side is refracted at the interface. And then radiate the light. In addition, required refraction occurs on the surface of the resin convex portion, so that light can be scattered, and it is possible to achieve in-plane uniform surface emission as a whole.

  According to a preferred embodiment of the light guide plate of the present invention, the resin convex portion disposed on the surface of the emission surface can be configured by a linear or curved ridge, The protrusions can be formed by being applied by screen printing and then cured. Further, a plurality of reflective dots can be formed on the reflective surface of the light guide plate, and the plate-like member of the light guide plate can be made of a transparent resin material.

  Further, in the method of manufacturing a light guide plate having the emission surface and the reflection surface facing each other of the plate-like member of the present invention and emitting surface distribution light from the emission surface, a plurality of reflection patterns are formed on the back surface of the plate-like member. A step of applying a photocurable resin on the surface of the plate-like member to form a required pattern, and curing the photocurable resin of the required pattern formed on the surface of the plate-like member And a step of making it. By applying such a photocurable resin and curing it to a required pattern, the shape necessary for light scattering can be formed without heating or cutting the plate-like member.

  According to the light guide plate of the present invention, the light from the reflecting surface can be refracted by the resin convex portion at the interface with the plate-like member or at the resin convex portion and the external interface. By forming the pattern, it is possible to obtain a light guide plate that does not involve an increase in the size of manufacturing equipment and realizes highly accurate light scattering.

  A preferred embodiment of the light guide plate of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view of the light guide plate 10 of the present embodiment, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a schematic sectional view showing an image display device using the light guide plate of the present embodiment.

  As shown in FIG. 1, the light guide plate 10 of the present embodiment is a plate-like member made of a transparent synthetic resin with the emission surface 12 and the reflection surface 11 facing each other as main surfaces, for example, polyester resin, amorphous Acrylic resin such as polyester resin, polymethyl methacrylate (PMMA), polycarbonate resin, polystyrene resin (PS), styrene / acrylonitrile resin (SAN), urethane resin, cycloolefin resin, alicyclic polyolefin resin, cyclic polyolefin resin, alicyclic Various transparent polymer materials such as acrylic resin, amorphous fluororesin, epoxy resin, polyimide resin, polyamide resin, vinyl ester resin can be used. By combining these modified materials and multiple resin materials There may be. Moreover, you may have a structure which contains a fluorescent material in a part or whole surface of the light-guide plate 10. FIG.

  The bottom surface side of the light guide plate 10 is a reflective surface 11, and the concave portions 13 that function as a plurality of reflective dots are formed in a matrix from the surface of the reflective surface 11 in a substantially quadrangular pyramid shape. The shape of the recess 13 may be another pyramid shape such as a cone, a triangular pyramid, or a hexagonal pyramid. Further, the positions of the recesses 13 are not limited to the orderly arrangement in a matrix, and the recesses 13 are formed, for example, near the center of the reflection surface or in a region far from the side surface on which the light is incident so that the distribution of reflected light is uniform. The pattern may be densely arranged. Moreover, as what is formed in the reflective surface 11, you may form not only a reflective dot but the groove | channel for reflection, a protruding item | line part, etc.

  The surface side of the light guide plate 10 is an exit surface 12, and a protrusion 14 is formed on the exit surface 12 of the light guide plate 10 by applying a photocurable resin and curing it by light irradiation. This protrusion 14 is a region that functions like a lens as a resin protrusion, and an interface exists between the exit surface 12 and the protrusion 14 due to a difference in composition, and a required angle from the reflection surface 11 side. The incident light incident on is emitted so as to be refracted and scattered at the interface between the exit surface 12 and the protrusion 14. In addition, required refraction occurs between the air and the resin constituting the ridge portion 14 on the surface of the ridge portion 14 so that light can be scattered, and the surface emission of the entire surface can be uniformized. Is possible. The cross-sectional shape of the protrusion 14 is appropriately determined according to the emitted light beam, and has a flat portion, a corner, or a recess as long as it protrudes from the light exit surface 12 of the light guide plate 10. It may be.

  The pattern of the protrusions 14 formed on the emission surface 12 of the light guide plate 10 may be an oblique grid pattern as illustrated in FIG. 1 or may be a sine wave or sawtooth pattern. Further, the pitch of the pattern may have a constant interval on the entire surface, and it is also possible to arrange so that portions where light needs to be scattered are dense. Further, the protrusion 14 does not necessarily need to form a straight convex portion, and may be a pattern in which curves and points are combined. Moreover, the magnitude | size of the protrusion part 14 may differ partially, and you may have a pattern which overlapped the some protrusion part 14 partially. Moreover, it can also be configured by partially changing the resin material of the ridges 14, and the refractive index of light can be appropriately controlled by changing the resin material. As another example of the resin convex portion, a plurality of dot-like microlenses may be arranged side by side.

  As the photocurable resin used for forming the protruding portion 14 of the present embodiment, various UV curable resins that are liquid in an uncured state and can be cured and cured by irradiation light or Visible light curable resin can be used, for example, UV curable silicone resin, ester acrylate resin, urethane acrylate resin, epoxy acrylate resin, melamine acrylate resin, acrylic resin acrylate, unsaturated polyester Based resins and the like.

  Moreover, as a light source used for formation of the protrusion part 14 of this embodiment, what is necessary is just to be able to obtain the ultraviolet light or visible light of the wavelength range which hardens the photocurable resin to be used, and the photocurable resin to be used is used. For example, when an ultraviolet curable resin (UV curable resin) is used, an ultraviolet light source such as a low-pressure mercury lamp is preferably used.

  FIG. 3 shows an image display apparatus configured by incorporating the light guide plate 10 of the present embodiment. In this image display device, a light source 15 such as an LED array or a cold cathode tube arranged by arranging a plurality of LEDs is arranged on the side surface side, and the side of the light source 15 opposite to the side on which the light guide plate 10 is arranged. A reflective member or cover 16 is attached in such a shape as to cover the peripheral surface. The light guide plate 10 has a reflection surface 11 side as a bottom surface side and an emission surface 12 side as a surface side.

  On the reflective surface 11 side of the light guide plate 10, concave portions 13 each having a substantially square pyramid shape functioning as a plurality of reflective dots are formed as described above, and a reflective plate 17 is provided on the bottom side of the reflective surface 11. It is attached. The reflection plate 17 has a function of reflecting light emitted from the light guide plate 10 toward the bottom surface toward the light guide plate 10, and is configured by, for example, a resin plate bonded with a metal foil or the like.

  As described above, the protrusion 14 functioning as the resin protrusion is disposed on the light exit surface 12 side of the light guide plate 10, and a prism sheet 18 is provided above the protrusion 14. A liquid crystal panel 19 is provided on the sheet 18 for arranging image cells in a matrix and performing color or black and white display according to a required image signal. If sufficient light is diffused by the ridges 14 and the in-plane uniformity of the planar light rays incident on the liquid crystal panel 19 is sufficient, the prism sheet 18 can be omitted without being provided.

  In the image display device having such a structure, light from the light source 15 is incident from one side surface of the light guide plate 10, and a part of the light incident from the side surface is emitted by the recess 13 formed in the reflecting surface 11. Is reflected from the light guide plate 10 and emitted from the light guide plate 10 toward the liquid crystal panel 19. At this time, in the ridges 14 arranged on the emission surface 12, there is an interface between the emission surface 12 and the ridges 14 due to the difference in composition, and incidence is made at a required angle from the reflection surface 11 side. The light exits so as to be refracted and scattered at the interface between the exit surface 12 and the protrusion 14. In addition, required refraction occurs between the air and the resin constituting the ridge portion 14 on the surface of the ridge portion 14 so that light can be scattered, and the surface emission of the entire surface can be uniformized. Will be possible.

  Next, the manufacturing method of the light guide plate of this embodiment is demonstrated, referring FIG. 4 thru | or FIG. First, as shown in FIG. 4, a plate member 20 made of transparent resin having a front surface 22 and a back surface 21 facing each other is prepared. The plate-like member 20 is made of a thermoplastic synthetic resin such as an acrylic resin, and has a required plate thickness.

  Next, as shown in FIG. 5, a plurality of recesses 23 that function as reflective dots are formed on the back surface 21 side of the plate-like member 20. These concave portions 23 can be formed by, for example, uneven processing using a hot roll or ultrasonic processing, and are formed by melting by local heating. Further, the recess 23 may be formed by using a pressing member or the like that is heated to a high temperature using high frequency, and such heat processing, uneven processing by a hot roll, or ultrasonic processing is used. In addition, not only the recess but also other protrusions and grooves may be formed on the reflecting surface.

  After the concave portion 23 is formed on the back surface 21 side of the plate-like member 20, as shown in FIG. 6, the photocurable resin 24 is applied in a required pattern on the surface 22 side of the plate-like member 20 by screen printing. That is, at the time of this screen printing, an uncured photocurable resin 24 is arranged on a screen portion 25 having a required pattern in advance, and an uncured photocuring is performed by a squeegee 26 in which an elastic member at the tip is formed. The mesh of the screen part 25 is made to permeate | transmit the mold resin 24 selectively. An uncured photocurable resin 24 is formed on the surface 22 of the plate-like member 20 with a required film thickness at a portion where the mesh of the screen portion 25 is transmitted.

  Subsequently, as shown in FIG. 7, the light curing resin 24 is cured by irradiating the uncured photocurable resin 24 with a light beam for curing the resin such as ultraviolet rays. As shown in FIG. A ridge portion 24 that functions as a portion is obtained on the surface 22 of the plate-like member 20.

  According to the light guide plate manufacturing method of this embodiment, the plate member 20 is heated to a shape necessary for light scattering by applying the photocurable resin 24 and curing it to a required pattern. Alternatively, it is possible to form a light guide plate capable of emitting light without cutting. In addition, according to the light guide plate manufacturing method of the present embodiment, the photocurable resin 24 is formed into a required pattern by screen printing, so that high-precision light diffusion can be realized without increasing the size of the manufacturing equipment. A light guide plate can be obtained.

  In the present embodiment, the reflective dots on the back surface side of the plate-shaped member are formed prior to the formation of the protrusions on the front surface side. It is also possible to form it after forming the part. Further, the plate-like member does not necessarily have a flat plate shape, and may be a plate-like member having a curved surface partially or entirely. In addition, high-precision printing is possible without relatively increasing the size of equipment by screen printing, and a plurality of plate-like members can be printed side by side. Moreover, you may make it form a resin recessed part instead of a resin convex part. Furthermore, the surface side is formed with protrusions and grooves on the surface using heat processing using high frequency, uneven processing by a hot roll, and ultrasonic processing, and the surface side is a combination of a resin convex portion and a processed portion. It is good as structure to do

It is a perspective view of the light-guide plate of one Embodiment of this invention. It is the II-II sectional view taken on the line of FIG. It is a schematic sectional drawing which shows the image display apparatus using the light-guide plate of embodiment of this invention. It is process sectional drawing for demonstrating the manufacturing method of the light-guide plate of embodiment of this invention, Comprising: It is process sectional drawing which shows the process of preparing a plate-shaped member. It is process sectional drawing for demonstrating the manufacturing method of the light-guide plate of embodiment of this invention, Comprising: It is process sectional drawing which shows the process of forming a recessed part in the back surface of a plate-shaped member. It is process sectional drawing for demonstrating the manufacturing method of the light-guide plate of embodiment of this invention, Comprising: It is process sectional drawing which shows a screen printing process. It is process sectional drawing for demonstrating the manufacturing method of the light-guide plate of embodiment of this invention, Comprising: It is process sectional drawing which shows the resin hardening process by light irradiation. It is process sectional drawing for demonstrating the manufacturing method of the light-guide plate of embodiment of this invention, Comprising: It is process sectional drawing which shows the completed light-guide plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light-guide plate 11 Reflecting surface 12 Output surface 13 Recessed part 14 Projection part 15 Light source 17 Reflecting plate 18 Prism sheet 19 Liquid crystal panel 20 Plate-shaped member 21 Back surface 22 Front surface 23 Recessed part 24 Photocurable resin 25 Screen part 26 Squeegee

Claims (8)

The plate-like member has an emission surface and a reflection surface facing each other, reflects light rays introduced from the light source from the reflection surface to the emission surface, and a resin convex portion is disposed on the surface of the emission surface. The light guide plate is characterized in that a surface distribution light beam is emitted from the emission surface. The light guide plate according to claim 1, wherein the resin convex portion disposed on the surface of the emission surface is formed of a linear or curved protrusion. The light guide plate according to claim 2, wherein the protrusion is formed by being applied by screen printing and then cured. The light guide plate according to claim 1, wherein the plate-like member is made of a transparent resin material. The plate-like member has an emission surface and a reflection surface facing each other, and reflects light rays introduced from the light source from the reflection surface to the emission surface, and a resin recess is disposed on the surface of the emission surface. A light distribution plate in which a surface-distributed light beam is emitted from the emission surface. In a method of manufacturing a light guide plate having an emission surface and a reflection surface facing each other of a plate-like member, and emitting surface distribution light rays from the emission surface,
Forming a plurality of reflective patterns on the back surface of the plate-like member;
Applying a photocurable resin to the surface of the plate-like member so as to have a required pattern;
And a step of curing a photocurable resin having a required pattern formed on the surface of the plate-like member. The method of manufacturing a light guide plate according to claim 6, wherein the plurality of reflection patterns are formed by ultrasonic processing. The method of manufacturing a light guide plate according to claim 6, wherein the photocurable resin is applied to the surface of the plate-like member by screen printing.