KR100737021B1 - Light guide for area light source, its production method, and area light source - Google Patents

Abstract

As a surface light source device in which the luminance unevenness in the region near the light guide light incident cross section due to thinning of the light guide is hardly confirmed, and there is little specific light output in the oblique direction in the vicinity of the light incidence cross section, the primary light source 1 and the light incidence cross section ( 31) and a planar light source device having a plate-shaped light guide 3 having a light exit surface 33 is provided. Here, the light guide light exit surface 33 consists of a rough surface, and in the specific area A in the vicinity of the light incident end surface 31, the average inclination angle θa of the surface is a general area B other than the specific area. The maximum value θa1 greater than the average value θa0 of the average inclination angle of the general area B is taken between the boundary with the light incidence end face 31 and the light incidence end face 31. In the vicinity, θa2 is smaller than the average value θa0 of the average inclination angle of the general area B. The maximum value (theta) a1 of an average inclination angle exists in the range of 2.2 degrees or more and 4.0 degrees or less. The average value (theta) a0 of the average inclination-angle in a general area exists in the range of 1.4 degrees or more and less than 2.4 degrees.

Description

Light guide for surface light source device, manufacturing method thereof, and surface light source device {LIGHT GUIDE FOR AREA LIGHT SOURCE, ITS PRODUCTION METHOD, AND AREA LIGHT SOURCE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type surface light source device, a light guide body used therein, and a manufacturing method thereof, and more particularly, to a surface light source device intended to reduce the confirmation of luminance unevenness and a light guide body used therein. The surface light source device of the present invention is a display panel of various types of devices such as a backlight of a liquid crystal display device used as a monitor such as a portable notebook, a display unit such as a liquid crystal television or a video integrated liquid crystal television, or a portable telephone. Backlight of a relatively small liquid crystal display device used as an indicator, or backlight of a liquid crystal display device used as a signboard or a signboard in a station or a public facility, or a traffic display on a highway or a general road. It is suitable for the backlight of the liquid crystal display device used as display devices, such as these.

The liquid crystal display device is widely used as a monitor of a portable notebook or the like, or as a display unit such as a liquid crystal television or a video integrated liquid crystal television, and other various fields. The liquid crystal display device basically consists of a backlight and a liquid crystal display element. As a backlight, the edge light system is used a lot from the viewpoint of the compactness of a liquid crystal display device. Conventionally, as an edge light backlight, at least one cross section of a rectangular plate-shaped light guide is used as a light incidence cross section, and a linear or rod-shaped primary light source such as a straight tube fluorescent lamp is disposed in accordance with the light incidence cross section. It is widely used to introduce the light generated from the primary light source into the light guide from the light incidence end face of the light guide, and to emit it from the light output plane which is one of the two main surfaces of the light guide.

By the way, in recent liquid crystal display devices, the ratio of the display screen dimension with respect to the external size is made to be as large as possible, and to increase the display efficiency. Therefore, even in the surface light source device, the ratio of the size of the light emitting surface with respect to its external size is made as large as possible, that is, the structural portion ("liquid smoke") existing in the frame shape around the light emitting surface is also called. It is required to make the size of the N) as small as possible.

On the other hand, in the surface light source device, the thickness reduction is also requested | required, and in order to respond to this request, the light guide body needs to be thinned. As the light guide becomes thin (for example, about 0.5 to 3 mm in thickness), the light generated from the primary light source functions as a secondary light source in the light guide ridge that forms a boundary between the light incident cross section and the light exit surface of the light guide. The effect of the above is shown on the luminance of the light emitting surface of the surface light source device. This effect is remarkable mainly in the region close to the light incident cross section. This phenomenon is not particularly a problem in the case where the liquid lead width is large, but the surface light source device having the small liquid lead width is a problem that the luminance unevenness due to this effect is particularly easy to be confirmed.

As one form which is easy to identify the luminance unevenness of such a light emitting surface, in the area | region near a light-incidence cross section, a high brightness part (bright line or a slit) and a low brightness part (dark line or a dark band) )) Occurs at specific intervals and is identified as a plurality of light and dark lines extending substantially parallel to the light incident cross section.

As a method for preventing the luminance unevenness in the vicinity of the light incidence cross section, for example, Japanese Patent Laid-Open No. 1998-153778 (Patent Document 1) discloses a light emitting surface as compared with a region adjacent to the light incidence cross section. It is disclosed to provide a band-shaped light diffusion region having high light scattering properties. Further, in order to achieve the same purpose, Japanese Patent Laid-Open Publication No. 200-216530 (Patent Document 2) discloses, for example, the average inclination angle of the surface of the area near the light incidence cross section of the light exit face in another area of the light exit face. The enlargement is disclosed.

Patent Document 1: Japanese Patent Application Laid-Open No. 1998-153778

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-216530

According to the method of the said patent document 1 and patent document 2, a dark band is not outstanding by making light scattering property or light diffusivity of the area | region near the light-incidence cross section of a light emission surface strong, and increasing the amount of emitted light in this area | region. It aims to reduce luminance unevenness.

However, the problem caused by thinning the light guide in the surface light source device having a small liquid lead width exists in addition to the above. That is, the light generated from the primary light source functions as a secondary light source in the light guide ridge forming the boundary between the light incident end face and the light exit face of the light guide. In the light emitting surface of the device, a particularly strong light output is performed in the inclined direction with respect to the normal direction, and when used as a backlight of a liquid crystal display device, the quality of a display image may fall.

In the method of the said patent document 1 and patent document 2, it is impossible to suppress such a thought fully.

SUMMARY OF THE INVENTION The present invention provides a surface light source device in which the luminance unevenness in the region near the light guide cross-section of light guide due to thinning of the light guide is hard to be confirmed, and the specific light output in the oblique direction in the vicinity of the light-incident cross section is small, and a light guide for use therein is provided. It is aimed at.

Summary of the Invention

According to the present invention, to solve the above problems,

A light guide for a surface light source device, which is also used to construct a surface light source device in combination with a primary light source, for guiding light generated from the primary light source.

A light incidence cross section through which light generated from the primary light source is incident, a light exit face through which light is emitted, and a rear surface opposite to the light exit face;

At least one of the light exit surface and the rear surface is a rough surface, and in the light exit surface and / or the rear surface formed of the rough surface, the average inclination angle of the surface is in the vicinity of the light incident surface. There is provided a light guide for a surface light source device, characterized in that there is an inclined angle diminished region that is decreasing at 0.5 ° or more toward the incident end face.

In one aspect of the present invention, the thickness at the edge of the light incidence end face side of the light guide is d, and at least a part of the inclined angle diminished region has a distance from the light incidence end face of 0.2d to 2d. It exists in the area. In one aspect of the present invention, at least a part of the inclined angle haptic region exists in a region from 0.2 mm to 4 mm in distance from the light incident end face.

Moreover, according to this invention, in order to solve the said subject,

A light guide for a surface light source device, which is also used to construct a surface light source device in combination with a primary light source, for guiding light generated from the primary light source.

A light incidence cross section through which light generated from the primary light source is incident, a light exit face through which light is emitted, and a rear surface opposite to the light exit face;

At least one of the light exit surface and the back surface is a rough surface, and in the light exit surface and / or the rear surface formed of the rough surface, in a specific region near the light incident cross section, the average inclination angle of the surface is different from the specific region. A maximum value that is greater than the average value of the average inclination angle of the general area is taken between the boundary between the general area and the light incidence cross section, and in the vicinity of the boundary with the light incidence cross section than the average value of the average inclination angle of the general area. There is provided a light guide for a surface light source device, which is becoming smaller.

In one aspect of the present invention, a position at the edge of the light incidence end face side of the light guide is d, and a position at which the maximum value of the average inclination angle is taken is a boundary to the light incidence end face of the specific region. The distance is in the range of d to 3d. In one aspect of the present invention, the maximum value of the average inclination angle in the specific region is within a range of 2.2 ° to 4.0 °. In one aspect of the present invention, the average value of the average inclination angle in the general region is in the range of 1.4 ° or more and less than 2.4 °. In one aspect of the present invention, the specific region has a distance from a boundary with the general region to a boundary with the light incidence end face of 10 to 30 times the thickness at the edge of the light incidence end face of the light guide. It is in range of ship. In one aspect of the present invention, the specific region has a distance from the boundary with the general region to the boundary with the light incident cross section within a range of 10 mm to 70 mm.

Moreover, according to this invention, in order to solve the said subject, the said surface light source device is provided so that the said primary light source may be arrange | positioned facing the light incidence cross section of the light guide for surface light source devices as mentioned above.

In one aspect of the present invention, the planar light source device is disposed on a light exit surface of the light guide, and has a light exit surface on which light exiting from the light exit surface of the light guide is incident and a light exit surface on the opposite side thereof. An optical deflecting element is further provided. In one aspect of the present invention, the optical deflecting element has a plurality of prism rows extending along the light incident cross section of the light guide body and arranged in parallel with each other on the light incident surface, wherein each of the prism rows is the light guide. It has a 1st prism surface into which light in the light exit surface of a sieve enters, and a 2nd prism surface in which incident light is reflected internally. In one aspect of the present invention, the primary light source is a linear light source.

Moreover, according to this invention, in order to solve the said subject,

A method for manufacturing a light guide for a surface light source device as described above, comprising: a first mold member having a first transfer surface for transferring the light exit surface and a second mold member having a second transfer surface for transferring the rear surface; Molding the light-transmissive synthetic resin, wherein the transfer surface region is formed on forming the first transfer surface and / or the second transfer surface for transfer formation of the light exit surface and the rough surface in the back surface. Wherein the first roughening is performed in a state in which a shielding effect is provided in the vicinity of the edge of the light guide end face corresponding to the boundary between the light incident end face and the light exit face of the light guide. This is provided.

In one aspect of the present invention, in view of forming the first transfer surface and / or the second transfer surface for the transfer formation of the light exit surface and the rough surface of the rear surface, the light emission surface corresponds to the general area. Second roughening is performed in a state in which a shielding effect on the transfer surface region is imparted. In one aspect of the present invention, a shielding effect on the vicinity of the edge is also provided in the transfer surface region corresponding to the specific region on the basis of the second roughening. In 1 aspect of this invention, the said 1st roughening and / or 2nd roughening is performed by an etching process. In one aspect of the present invention, the first roughening and / or second roughening are performed by blasting. In one aspect of the present invention, provision of the shielding effect is performed by arranging the shielding member, and the shielding member is disposed away from the first transfer surface or the second transfer surface.

Effects of the Invention

According to the present invention as described above, at least one of the light exit surface and the rear surface of the light guide for the surface light source device is composed of rough surfaces, and the rough surface has a light incidence cross section near the light incident cross section. Since the inclined angle diminished region that is decreasing in the vehicle by 0.5 ° or more is present, or the average inclined angle in a specific region near the light incident cross section is the boundary of the boundary with the general region other than the specific region and the light incident cross section. Since the maximum value is larger than the average value of the average inclination angle of the general area, and smaller than the average value of the average inclination angle of the general area in the vicinity of the boundary with the light incidence cross section, the light exit surface according to the light guide thinning is Luminance unevenness in the region near the light incidence cross section of the light incidence The less the light exit surface light source device is provided.

1 is a schematic perspective view showing one embodiment of a surface light source device according to the present invention.

FIG. 2 is a partial cross-sectional view of the surface light source device of FIG. 1.

3 is a schematic diagram showing the shape of light deflection by the light deflection element.

4 is a schematic diagram showing the relationship between the primary light source and the light guide surface and the average inclination angle distribution of the light exit surface.

5 is a view for explaining an example of the manufacturing method of the light guide.

FIG. 6 is a diagram illustrating an average inclination angle distribution of the light guide surface of the light guide manufactured in Example 1 and Comparative Example 1. FIG.

FIG. 7 is an enlarged view of a part of the average inclination angle distribution of FIG. 6.

FIG. 8 is a diagram showing the luminance distribution on the light emitting surface of the surface light source device manufactured in Example 1 and Comparative Example 1. FIG.

9 is an enlarged view of a part of the average inclination angle distribution of the light guide surface of the light guides manufactured in Example 2 and Comparative Example 2. FIG.

FIG. 10 is a diagram showing the luminance distribution on the light emitting surface of the surface light source devices manufactured in Example 2 and Comparative Example 2. FIG.

Explanation of the sign

1: primary light source 2: light source reflector

3: light guide 4: light deflecting element

5: light reflection element 8: liquid crystal display element

31: light incident cross section 32: side cross section

33: light exit surface 33 ': first transfer surface

34: Back side 34 ': Second transfer surface

41: light incident surface 42: light emitting surface

330: type 1 member 340: type 2 member

A: specific area B: general area

A ': transfer surface area B': transfer surface area

E: mold member edge M1, M2, M3: shield member

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings.

1 is a schematic perspective view showing an embodiment of a surface light source device according to the present invention, and FIG. 2 is a partial cross-sectional view thereof. As shown in the drawing, the surface light source device of the present embodiment includes a light guide 3 having at least one side cross section as a light incident end face 31 and having one surface substantially orthogonal to the light exit face 33. ) And a linear primary light source 1 disposed opposite to the light incident end face 31 of the light guide 3 and covered with the light source reflector 2, and disposed on the light exit surface of the light guide 3. The light reflection element 4 and the light reflection element 5 which are arrange | positioned facing the back surface 34 on the opposite side to the light emission surface 33 of the light guide 3 are comprised.

The light guide 3 is arrange | positioned in parallel with XY surface, and has comprised the rectangular plate shape as a whole. The light guide 3 has four cross sections, among which at least one side cross section of a pair of side cross sections parallel to the YZ plane is referred to as light incident cross section 31. The light incident end face 31 is disposed to face the primary light source 1, and the light generated from the primary light source 1 enters the light guide 3 from the light incident end face 31. In the present invention, for example, the light source may be disposed opposite to the other side end surface such as the side end surface 32 on the side opposite to the light incident end surface 31.

Two main surfaces substantially orthogonal to the light incident end face 31 of the light guide 3 are located substantially parallel to the XY plane, respectively, and one surface (the upper surface in the drawing) becomes the light exit surface 33. At least one of the light exit surface 33 or the rear surface 34 of the light exit surface 33 is provided with a directional light exit mechanism comprising a rough surface, thereby guiding the light incident from the light incident end surface 31 into the light guide 3. The light having directivity is emitted from the light exit face 33 in the light incident end face 31 and in the plane (XZ plane) orthogonal to the light exit face 33. The angle which the direction (peak light) of the peak of the emission light intensity distribution in this XZ surface distribution makes with the light emission surface 33 is made into (alpha). The angle α is, for example, 10 to 40 degrees, and the full width at half maximum of the emitted light intensity distribution is, for example, 10 to 40 degrees. The detail of the rough surface formed in the light output surface 33 or the back surface 34 of the light guide 3 is mentioned later.

In addition, in order to control the directivity in the surface (YZ plane) parallel to the primary light source 1 of the outgoing light from the light guide 3, in the other main surface which is not provided with the directional light output mechanism, the light incident cross section 31 It is preferable to form a lens surface in which a plurality of lens rows are arranged which extend in a substantially vertical direction (X direction) with respect to (). In the embodiment shown in FIG. 1, an array of a plurality of lens rows is formed on a light exit surface 33 and extends in a substantially vertical direction (X direction) with respect to the light incident end surface 31 on the back surface 34. A lens row forming surface is formed. In the present invention, the lens row forming surface may be formed on the light exit surface 33 and the rear surface 34 may be roughened, as opposed to the embodiment shown in FIG. 1.

As shown in FIG. 1, when the lens row forming surface is formed on the back surface 34 or the light output surface 33 of the light guide 3, as the lens row, a prism row and a lenticular lens extending substantially in the X-direction. Although a row, a V-shaped groove, etc. are mentioned, it is preferable to make the shape of a YZ cross section into a substantially triangular prism row.

In the present invention, when the prism row forming surface is formed on the back surface 34 of the light guide 3 as the lens row forming surface, the vertex angle is preferably in the range of 85 to 110 degrees. This is because by allowing the vertex angle to be in this range, it is possible to appropriately condense the emitted light from the light guide 3, and to improve the luminance as the surface light source device, more preferably in the range of 90 to 100 degrees. Range.

In the light guide of the present invention, the top portion of the prism row is aimed at accurately producing a desired prism row shape, obtaining stable optical performance, and suppressing abrasion and deformation of the prism top at the time of assembly work or use as a light source device. You may form a flat part or a curved part in the

Moreover, in this invention, it uses together with the light output mechanism formed in the above-mentioned light output surface 33 or its back surface 34, The directional light output mechanism by mixing and disperse | distributing light-diffusing microparticles inside a light guide body is provided. You may add.

The light incidence end face 31 is preferably roughened in order to adjust the area of light in the XY plane and / or in the XZ plane. As a method of forming a rough surface, a method of cutting with a ply tool or the like, a method of grinding with a grindstone, sandpaper, buffing, or the like, a method of blasting, electric discharge, electrolytic polishing, chemical polishing, or the like can be given. Examples of the blast particles used for blasting include spherical ones such as glass beads and polygonal ones such as alumina beads, but those using polygonal ones are preferable because they can form a rough surface having a great effect of widening light. . Anisotropic roughening surface can be formed by adjusting the cutting direction of cutting and polishing. In order to adjust the width of light in the XY plane, the machining direction in the Z direction can be adopted to form the near-surface irregularities in the Z direction, and in the Y direction to control the width of the light in the XZ plane. Can be used to form the near-surface irregularities in the Y direction. Although this roughening process can be performed directly to the light incident cross section of a light guide, it is also possible to process the part corresponded to the light incident cross section of a metal mold | die, and to transfer this at the time of shaping | molding.

The degree of roughening of the light incidence end face 31 has an average inclination angle θa of 1 to 5 degrees, a center line average roughness Ra of 0.05 to 0.5 µm, and a ten point average roughness Rz of 0.5 in the light guide thickness direction. It is preferable that it is-3 micrometers. By setting the degree of roughening of the light incidence end face 31 to this range, it is possible to suppress the occurrence of light and dark bands on the light exit surface and to make it difficult to see the bright and dark lines. The average inclination angle θa is more preferably in the range of 2 to 4.5 degrees, particularly preferably in the range of 2.5 to 3 degrees. Center line average roughness Ra becomes like this. More preferably, it is 0.07-0.3 micrometer, Especially preferably, it is the range of 0.1-0.25 micrometer. Ten-point average roughness Rz becomes like this. More preferably, it is the range of 0.7-2.5 micrometers, Especially preferably, it is the range of 1-2 micrometers. In the longitudinal direction, the degree of roughening of the light incident end surface 31 is, for the same reason as described above, the average inclination angle θa is 1 to 3 degrees, the centerline average roughness Ra is 0.02 to 0.1 µm, and the 10-point average It is preferable that roughness Rz is 0.3-2 micrometers. The average inclination angle θa is more preferably in the range of 1.3 to 2.7 degrees, and particularly preferably 1.5 to 2.5 degrees. The centerline average roughness Ra is more preferably in the range of 0.03 to 0.08 µm, particularly preferably 0.05 to 0.07 µm. Ten-point average roughness Rz becomes like this. More preferably, it is 0.4-1.7 micrometers, Especially preferably, it is the range of 0.5-1.5 micrometers.

As the light guide 3, it is not limited to the shape shown in FIG. 1, The thing of various shapes, such as a wedge shape with a thick light incident cross section, can be used.

The light deflecting element 4 is disposed on the light exit surface 33 of the light guide 3. The two main surfaces 41 and 42 of the optical deflecting element 4 are arranged in parallel with each other as a whole, and are respectively located in parallel with the XY plane as a whole. One of the main surfaces 41 and 42 (the main surface located on the light exit surface 33 side of the light guide 3) is the light incident surface 41, and the other is the light exit surface 42. The light exit surface 42 is a flat surface parallel to the light exit surface 33 of the light guide 3. The light incident surface 41 is a prism row forming surface in which a plurality of prism rows extending in the Y direction are arranged in parallel with each other. The prism row forming surface may be provided with a relatively narrow bottom flat portion (e.g., a flat portion having a width equal to or smaller than the X-direction dimension of the prism row) between adjacent prism rows, but increasing light utilization efficiency. From the above, it is preferable to arrange the prism rows continuously in the X direction without providing the bottom flat portion.

3, the shape of the optical deflection by the optical deflection element 4 is schematically shown. 3 shows an example of the traveling direction of peak light (light corresponding to the peak of the emitted light distribution) from the light guide 3 in the XZ plane. The peak light emitted obliquely from the light exit surface 33 of the light guide 3 at an angle α is incident on the first prism face of the prism row and totally internally reflected by the second prism face, so that it is almost normal to the light exit face 42. Eject in the direction of. In addition, within the YZ plane, due to the action of the prism heat of the light guide body 34 as described above, the luminance in the direction of the normal line of the light exit surface 42 can be sufficiently improved in a wide range.

The shape of the prism face of the prism array of the optical deflection element 4 is not limited to a single plane, but can be, for example, a cross-sectional convex polygonal shape or a convex curved shape, whereby high brightness and narrow field of view can be achieved. .

In the optical deflecting element 4, the top portion of the prism row is used for the purpose of accurately producing a desired prism shape, obtaining stable optical performance, and suppressing abrasion and deformation of the prism top portion at the time of assembly work or use as a light source device. The top flat portion or the top curved surface portion may be formed in the. In this case, the width of the top flat portion or the top curved surface portion is preferably 3 μm or less, from the viewpoint of suppressing the occurrence of a nonuniform pattern of luminance due to a decrease in luminance as a surface light source device or sticking phenomenon, more preferably. The width | variety of a top part flat part or a top part curved part is 2 micrometers or less, More preferably, it is 1 micrometer or less.

The primary light source 1 is a linear light source extending in the Y direction, and as the primary light source 1, for example, a fluorescent lamp or a cold cathode tube can be used. In this case, as shown in FIG. 1, the primary light source 1 may be further provided not only in the case of facing the side end face of the light guide 3 but also in the side end face of the opposite side as necessary.

The light source reflector 2 guides the light of the primary light source 1 to the light guide 3 with less loss LA. As the material, for example, a plastic film having a metal vapor deposition reflective layer on its surface can be used. As shown, the light source reflector 2 avoids the light deflecting element 4 from the outer edge of the light reflecting element 5 from the outer surface of the primary light source 1 to the light exit surface edge of the light guide 3. It is wound up in wealth. On the other hand, the light source reflector 2 may be wound around the light exit surface edge of the light deflecting element 4 from the outer edge of the light reflection element 5 via the outer surface of the primary light source 1. It is also possible to attach such a reflecting member as the light source reflector 2 to the side cross section other than the light incident end face 31 of the light guide 3.

As the light reflection element 5, for example, a plastic sheet having a metal vapor deposition reflection layer on its surface can be used. In the present invention, it is also possible to use a light reflection layer formed by metal deposition or the like on the back surface 34 of the light guide 3 instead of the reflective sheet as the light reflection element 5.

The light guide 3 and the light deflecting element 4 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacryl resin is excellent and suitable for the height of light transmittance, heat resistance, mechanical properties, and molding processability. As such methacryl resin, it is resin which has methyl methacrylic acid (methacrylic acid) as a main component, and it is preferable that methyl methacrylic acid (methacrylic acid) is 80 weight% or more. In the case of forming the surface structure such as the rough surface of the light guide 3 and the light deflecting element 4 or the surface structure such as the prism heat or the lenticular lens train, a transparent member is used to form a mold member having a desired surface structure. It may be formed by hot pressing by use, and may be formed simultaneously with molding by screen printing, extrusion molding or injection molding. Moreover, it is also possible to form a structural surface using heat or a photocurable resin. Moreover, the rough surface which consists of active energy precurable resin on the surface of transparent base materials, such as a transparent film or sheet which consists of polyester resin, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylimide resin, etc. A structure or a lens array arrangement may be formed, and such sheets may be bonded together on a separate transparent substrate by a method such as bonding or fusion. As active energy precurable resin, a polyfunctional (meth) acryl compound, a vinyl compound, (meth) acrylic acid ester, an aryl compound, the metal salt of (meth) acrylic acid, etc. can be used.

The light emitting surface of the surface light source device including the primary light source 1, the light source reflector 2, the light guide 3, the light deflection element 4, and the light reflection element 5 as described above (light deflection element 5). By arranging the transmissive liquid crystal display element 8 on the light-emitting surface 42) of Fig. 3), a liquid crystal display device having the surface light source device of the present invention as a backlight is constructed. The liquid crystal display device is observed by an observer from above in FIG. 3.

Next, the rough surface which comprises the light output mechanism of the light guide 3 is demonstrated. 4 is a schematic diagram showing the relationship between the primary light source 1 and the light guide light exit surface 33 and the distribution of the average inclination angle θa of the light exit surface 33. The rough surface formed on the light exit surface 33 is not formed uniformly as a whole, but is composed of two regions, i.e., a specific region A and a general region B, which are divided by the distribution form of the average inclination angle θa. do. The specific area A is an area of the width ((X-direction dimension) x1) in the vicinity of the light incident end face 31, and the general area B is another area. The general area B is most of the area including the central part of the light exit surface 33, and the specific area A has a width x1 of, for example, the edge of the light incident cross section side of the light guide 3. It is in the range of 10 d-30 d as thickness d (refer FIG. 2), specifically, it exists in the range of 10 mm-70 mm, for example, and is a comparatively narrow area | region with respect to the said general area | region B. As shown to FIG. In addition, the thickness d in the short edge of the light-incident cross section side of the light guide 3 exists in the range of 0.5 mm-3 mm, for example.

The average tilt angle [theta] a can be obtained using a surface roughness and contour measuring instrument (for example, surf rubber [trade name] manufactured by Tokyo Seimitsu Co., Ltd., Japan) in accordance with ISO 4287 / 1-1984. That is, it can obtain | require using the following (1) formula and (2) formula from the manufactured gradient function f (x) using the coordinate of a measuring direction as x. Here, L is a measurement length and Aa is the tangent of an average inclination-angle (theta) a.

In the actual measurement, the surface of the light guide 3 is measured in the Y direction, and the measurement is placed in the X direction at every constant pitch (for example, 1 mm pitch) to obtain? A, and the specific area A and the The distribution form of the average inclination angle (theta) a in the X direction in the general area B can be calculated | required.

As shown in FIG. 4, in the general area B, the distribution form of the average inclination angle θa is relatively gentle, and the average value of the entire range of the average inclination angle θa in the X direction is θa0. On the other hand, in the specific area A, the distribution form of the average inclination angle θa is relatively varied, and the average inclination angle θa at the position of the distance x2 from the boundary with the light incident end face 31. Takes the local maximum [theta] a1. This maximum value [theta] a1 is larger than [theta] a0. That is, in the specific area A, the average inclination angle θa is gradually increased from the boundary with the general area B with the light incidence end face 31 and first from θa0, and then at the maximum value θa1. And then become approximately low gradually. And the average inclination angle (theta) a of a specific area | region becomes smaller than (theta) a0 in the vicinity of the boundary with the light incident cross section 31, and is (theta) a2 (<(theta) a0) at the boundary with the light incident cross section 31. As shown in FIG. In this manner, in the specific area A, the area in which the average inclination angle θa is larger than the general area B is provided so that the surface light source device in the area near the light incident end face 31 due to the light guide thinning. The effect of making it difficult to confirm the luminance unevenness of the light emitting surface can be obtained. Further, in the vicinity of the boundary with the light incidence end face 31, the average inclination angle θa is made smaller than θa0, whereby the inclination direction in the surface light source device light emitting surface in the vicinity of the light incidence end face 31 due to the light guide body thinning. The effect of suppressing specific light emission of can be obtained.

(theta) a0 exists in the range of 1.4 degrees or more and less than 2.4 degrees, for example. Moreover, (theta) a1 exists in the range of 2.2 degrees or more and 4.0 degrees or less, for example. (theta) a2 exists in the range of 0.8 degrees or more and 2.0 degrees or less, for example. In the position where the average inclination angle [theta] a takes the maximum value [theta] a1, it is preferable that the distance x2 to the boundary with the light incidence end face 31 exists within the range of d to 3d. This is because the position which takes the maximum value (theta) a1 exists in this range, and a bright line can be applied.

In the specific area A, in the range from the light incidence end face 31 to the distance x2 in the vicinity of the light incidence end face 31, the average inclination angle θa is 0.5 ° toward the light incidence end face 31. There exists the inclination-angled immersion area | region decreasing in the abnormal difference. It is preferable that at least one portion of the inclined angle diminished region exists within a band-shaped area of 0.2d to 2d in distance from the light incident end face 31. For example, at least a portion of the inclined angle diminished region is present in a band-shaped region whose distance from the light incident end face 31 is 0.2 mm to 4 mm. Since the inclination angle sensation region of 0.5 ° or more such an average inclination angle diminishing amount is present in the vicinity of the light incidence end face 31, the inclination direction in the surface light source device light emitting surface in the vicinity of the light incidence end face 31 due to the light guide thinning is singular. The effect of suppressing red light emission can be obtained.

An example of the manufacturing method of the light guide 3 which has the above light exit surface 33 is demonstrated with reference to FIG.

Here, as shown in FIG. 5A, the light guide 3 has a first type member 330 and a back surface 34 having a first transfer surface 33 ′ for the transfer formation of the light exit surface 33. It is produced by molding the translucent synthetic resin using the second mold member 340 having the second transfer surface 34 'for transfer formation of the resin. As the molding method, hot press, injection molding or the like can be used. In FIG. 5A, only the first and second mold members 330 and 340 are shown as the mold apparatus for molding, but a cross section disposed around these mold members and corresponding to the light incident cross section or other side cross section of the light guide is shown. A cylindrical member having a transfer sidewall face for transferring is also used.

The second mold member 340 can be produced by mechanical cutting on a surface of a metal plate such as a stainless steel plate or a copper alloy plate. In addition, the 1st type | mold member 330 can be manufactured by the blast process or the etching process regarding the surface of metal flat plates, such as a stainless steel plate and a copper alloy plate.

The case where manufacture of the 1st type | mold member 330 is performed by a blast process is demonstrated below. First, as shown in the schematic cross-sectional view in Fig. 5B, the edge of the edge E corresponding to the boundary with the light incident cross section of the transfer surface region A 'corresponding to the specific region A of the light guide light exit surface. In the state which provided the shielding effect by the shielding member M1 in the vicinity, 1st roughening is performed by spraying a blast particle toward the surface of a metal flat plate under 1st conditions. Thereby, roughening of the 1st transfer surface 33 'other than the area | region of about half of the said distance x2 in the vicinity of the edge E is performed. The first condition is that the material, particle size, spraying speed, spraying distance and shielding member M1 of the blast particles can be manufactured such that the surface can be transferred to form the surface of the average inclination angle θa0 by this roughening. ) And so on. Next, as shown in a schematic cross-sectional view in FIG. 5C, a shielding effect is imparted by the shielding member M2 to the transfer surface region B 'corresponding to the general region B of the light guide surface. In the above, the second roughening is executed under the second condition. Thereby, roughening regarding the transfer surface area | region A 'is performed. The second condition is that the material, particle size, spraying speed, spraying distance and shielding of the blast particles, such that the roughening can produce a transfer surface capable of transferring and forming a specific area A of the average inclination angle distribution. Arrangement | positioning of the member etc. are set suitably. Moreover, in this 2nd roughening, the shielding member M3 with respect to the vicinity of the edge E in the transfer surface area | region A '(the area | region about half of the said distance x2 of the vicinity of the edge E). It is also possible to provide a shielding effect. According to this, formation of the transfer surface which can transfer-form the specific area | region A of the average inclination-angle distribution in which the average inclination-angle (theta) a in the vicinity of the boundary with the light incident cross section 31 becomes smaller than (theta) a0 becomes easy. In addition, the blasting process can be performed by scanning the injection nozzle in parallel with respect to the surface of the mold member while injecting blast particles from the injection nozzle.

As shown in Figs. 5B and 5C, when the blasting process as described above is arranged, the shield members M1 to M3 are separated from the mold member transfer surface 33 'to realize a gentle change in the average inclination angle distribution. Can be. On the other hand, by arranging the shielding members M1 to M3 close to the mold member transfer surface 33 'at the time of blast processing, a steep (steep and steep) change in the average inclination angle distribution can be realized. The distance between the shielding member and the mold member transfer surface may be appropriately set in accordance with the desired average inclination angle distribution.

5A using the first and second mold members 330 and 340 manufactured as described above, the first and second transfer surfaces 33 'and 34' are formed using a molding method such as injection molding. The light guide 3 having the light exit surface 33 and the back surface 34 of the required surface form can be manufactured by transferring the surface shape of the film to the surface of the translucent synthetic resin material.

The above transfer surface 33 'can be formed by etching instead of blasting. In this etching treatment, the light guide surface light-emitting surface 33 having a desired average inclination angle distribution can be transferred by setting the concentration of the etching solution, the processing time and the arrangement of the shielding member in contact with the mold member transfer surface. The transfer surface 33 'can be formed.

Example

Hereinafter, an Example and a comparative example demonstrate this invention.

Example  One

In the present Example, the light guide body demonstrated in embodiment of FIGS. 1-4, and the surface light source device using the same were manufactured.

In order to manufacture the 1st type member 330, the surface of the stainless steel plate of 309 mm x 234 mm and 3 mm of thickness which mirror-finished was performed, and glass beads (Potaz Barrodini temporary of Japan with a particle diameter of 75 micrometers or less) Using 1 to 220 (brand name) manufactured by Shikisha, the distance to the flush nozzle was 320 mm using a stainless steel plate, and the first roughening was carried out by blasting almost the entire surface at a flush pressure of 0.1 MPa. At this time, as shown in FIG. 5B, the shielding member M1 was floated and provided from a stainless plate, and only the area | region near the edge (one long side) E was not roughened. At the boundary between the area near the edge and the other area, the degree of blasting was continuously changed, and the change was steep and steep.

Next, the blowing nozzle was moved and blasted along the edge of the said shielding member in the state which raised and installed the shielding member M1 from the stainless steel plate so that the area | region in the vicinity of the edge E may not be roughened. Specifically, the flushing nozzle was moved and blasted six times on the same linear shape at the flushing pressure of 0.30 MPa with respect to the strip-shaped area adjacent to the area near the edge E.

In addition, as shown in Fig. 5C, the shielding members M2 and M3 are arranged with a gap in such a manner as to form a slit having a width of 3 mm, and the center of the slit is the maximum value of the average inclination angle of the specific region, That is, it was set to the position of 4.5 mm rather than the edge E, and in the state which floated and arrange | positioned from the stainless plate, the blasting process was carried out by moving the flushing nozzle three times at the flushing pressure 0.15 Mpa of the linear shape just above a slit.

On the other hand, in order to manufacture the 2nd type member 340, on the surface of the stainless steel plate of 309 mmx234 mm and thickness 3mm which mirror-finished, the vertex angle 100 degree, the top-end curvature radius 15 micrometers, pitch 50 micrometers The transfer surface for transferring and forming the prism pattern which made the prism line of this is formed by cutting.

The injection molding of the transparent acrylic resin is performed using the 1st and 2nd type | mold members 330 and 340 manufactured as mentioned above, and the thickness is made from the light incident end surface 31 side in the rectangle of 307 mm x 230 mm. The light exit surface 33 was roughened in the wedge shape continuously changing from 2.2 mm to 0.7 mm on the opposite end surface side, and the light guide 3 in which the prism pattern was formed in the back surface 34 was produced.

The average inclination-angle distribution of the specific area | region A (region from the light incident cross section to 40 mm) and the general area | region B of the light output surface 33 of the manufactured light guide 3 is shown in FIG. The average inclination-angle distribution in area | region A is enlarged and shown in FIG. The average inclination angle at the position where the distance from the light incidence cross section is 0.5 mm is 1.55 °, the average inclination angle at the position where the distance from the light incidence cross section is 1.5 mm is 2.00 °, and the distance from the light incidence cross section is 2.5. The average inclination angle at the position of mm was 2.46 degrees, and the average inclination angle at the position of 3.5 mm of the distance from the light incidence cross section was 2.67.

The primary light source 1 made of a cold cathode tube was disposed along the longitudinal direction of the light guide 3, and was covered with the light source reflector 2 so as to face the light incident end face 31 of the light guide 3. A light reflecting element 5 made of a light scattering reflecting sheet is disposed as opposed to a given back surface 34 of the prism pattern of the light guide 3, and a plurality of light reflecting surfaces 33 made of a rough surface are disposed. The optical deflecting element 4 which consists of a prism sheet in which the parallel arrangement of the prism rows was formed was arrange | positioned so that the prism row formation surface might be the light-guide body light emission surface side, and the surface light source device as shown in FIG. 2 was produced. As the prism sheet of the optical deflecting element 4, one prism face was used in a convex curved shape with a curvature radius of 1000 mu m and the other prism face was in a planar shape, while being stretched in parallel at a pitch of 50 mu m.

When the primary light source 1 of the manufactured surface light source device was turned on and the vicinity of the light-incident cross section 31 of the light emitting surface was observed, the light and dark lines which became uneven luminance could not be confirmed. In addition, when the vicinity of the light incidence end face 31 of the light emitting surface was observed from the inclination direction (that is, as if looking into the light incidence end face 31), specific light output in the inclination direction was not confirmed.

When the luminance distribution on the light emitting surface of the surface light source device was measured, it gradually decreased from the center to the light guide cross-section side of the light guide as shown in Fig. 8, which coincided with the observation result.

Comparative example  One

The light guide body was manufactured like Example 1 except having not used the shielding member M1 and not performing the blast process which uses the shielding members M2 and M3. 6 and 7 show the average inclination angle distribution of the light exit surface of the manufactured light guide. Moreover, the average inclination angle in the position where the distance from the light incidence cross section is 0.5 mm is 2.76 degrees, the average inclination angle in the position where the distance from the light incidence cross section is 1.5 mm is 2.81 degrees, and the distance from the light incidence cross section is 2.5 The average inclination angle at the position of mm was 2.68 degrees, and the average inclination angle at the position of the 3.5 mm distance from the light incidence cross section was 2.57 degrees.

Using the manufactured light guide body, the surface light source device was produced like Example 1. When the primary light source of the surface light source device was turned on and the vicinity of the light incidence cross section of the light emitting surface was observed, light and dark lines and brightness bands of luminance unevenness were found. Moreover, when the vicinity of the light incident cross section of the light emitting surface was observed from the inclination direction (that is, from the same direction as looking into the light incidence cross section side), specific light output of the inclination direction was confirmed.

The luminance distribution on the light emitting surface of the surface light source device was measured. As shown in Fig. 8, the luminance change was greater than that of Example 1, especially in the vicinity of the light guide cross-section of light guide, which was in agreement with the observation result. .

Example  2

In order to manufacture the 1st type member 330, the surface of the stainless steel plate of 336 mm x 214 mm which was mirror-finished, and thickness 3 mm was made into glass beads (Potaz and Barodyni Co., Ltd. of Japan with a particle diameter of 75 micrometers or less). Using 1 to 220 (brand name) manufactured by Shikisha, the distance to the flush nozzle was 320 mm using a stainless steel plate, and the first roughening was carried out by blasting almost the entire surface at a flush pressure of 0.1 MPa. At this time, as shown in FIG. 5B, the shielding member M1 was floated and provided from a stainless plate, and only the area | region near the edge (one long side) E was not roughened. The arrangement | positioning of the shielding member M1 regarding a stainless steel plate, ie, the overlap width of the shielding member M1 regarding the stainless steel plate in the surface parallel to a stainless steel plate was made smaller than Example 1. FIG. Thereby, the change of the grade of the blasting process in the boundary between the area | region near the edge E and other area | region was slower than Example 1.

Next, the blowing nozzle was moved and blasted along the edge of the said shielding member in the state which floated and installed the shielding member M1 so that the area | region in the vicinity of the edge E may not be roughened. Specifically, the blasting process was performed by moving the flushing nozzle six times on the same linear shape as the flushing pressure of 0.30 MPa with respect to the strip-shaped region adjacent to the area near the edge E.

On the other hand, in order to manufacture the 2nd type member 340, on the surface of the stainless steel plate of 336 mm x 214 mm and 3 mm thickness which mirror-finished, a vertex angle of 100 degrees, a top-end curvature radius of 15 micrometers, and a pitch of 50 micrometers The transfer surface for transferring and forming the prism pattern which made the prism line of this is formed by cutting.

The injection molding of the transparent acrylic resin is performed using the 1st and 2nd type | mold members 330 and 340 manufactured as mentioned above, and are 336 mm x 213 mm rectangle, and the thickness is from the light incident end surface 31 side. The light exit surface 33 was roughened in the wedge shape continuously changing from 2.6 mm to 0.7 mm in the cross section on the opposite side, and the light guide 3 in which the prism pattern was formed in the back surface 34 was produced.

The average inclination-angle distribution in the specific area | region A of the light emission surface 33 of the manufactured light guide 3 is shown in FIG. The average inclination angle at the position where the distance from the light incidence cross section is 0.2 mm is 1.92 °, the average inclination angle at the position where the distance from the light incidence cross section is 1 mm is 2.32 °, and the distance from the light incidence cross section is 2 The average inclination angle at the position of mm was 2.53 degrees.

The primary light source 1 made of a cold cathode tube was disposed along the longitudinal direction of the light guide 3, and was covered with the light source reflector 2 so as to face the light incident end face 31 of the light guide 3. A light reflecting element 5 made of a light scattering reflecting sheet is disposed as opposed to a given back surface 34 of the prism pattern of the light guide 3, and a plurality of light reflecting surfaces 33 made of a rough surface are disposed. The optical deflecting element 4 which consists of a prism sheet in which the parallel arrangement of the prism rows was formed was arrange | positioned so that the prism row formation surface might be the light-guide body light emission surface side, and the surface light source device as shown in FIG. 2 was produced. As the prism sheet of the optical deflecting element 4, one prism face was used in a convex curved shape with a curvature radius of 1000 mu m, and the other prism face was stretched in parallel at a pitch of 50 mu m in a planar shape.

When the primary light source 1 of the manufactured surface light source device was turned on, and the vicinity of the light-incident cross section 31 of the light emitting surface was observed, the degree of expression of the dark and dark bands which become luminance unevenness was small. In addition, when the vicinity of the light incidence end face 31 of the light emitting surface was observed from the inclination direction (that is, as viewed by the light incidence end face 31), the degree of specific light output in the inclination direction was also small.

When the luminance distribution on the light emitting surface of the surface light source device was measured, it gradually decreased from the center to the light guide cross-section side of the light guide as shown in Fig. 10, which coincided with the observation result.

Comparative example  2

A light guide was manufactured in the same manner as in Example 2 except that the shielding member M1 was not used. A part of the average inclination angle distribution of the light exit surface of the manufactured light guide is shown in FIG. In addition, the average inclination angle in the position where the distance from the light incidence cross section is 1 mm was 3.11 °, and the average inclination angle in the position where the distance from the light incidence cross section was 2 mm was 2.84 °.

Using the manufactured light guide body, the surface light source device was produced like Example 2. When the primary light source of the surface light source device was turned on and the vicinity of the light incidence cross section of the light emitting surface was observed, light and dark lines and brightness bands of luminance unevenness were found. Moreover, when the vicinity of the light incident cross section of the light emitting surface was observed from the inclination direction (that is, from the same direction as looking into the light incidence cross section side), specific light output of the inclination direction was confirmed.

The luminance distribution on the light emitting surface of the surface light source device was measured, and as shown in Fig. 10, the luminance change was greater than that in Example 2, especially in the vicinity of the light guide cross-section of light guide, which was in agreement with the observation result.

Claims (19)

A light guide for a surface light source device, which is used to construct a surface light source device in combination with a primary light source and guides light generated from the primary light source. A light incidence cross section through which light generated from the primary light source is incident, a light exit face through which light is emitted, and a rear surface opposite to the light exit face; At least one of the light exit surface and the rear surface is a rough surface, and in the light exit surface and / or the rear surface formed of the rough surface, an average inclination angle of the surface is 0.5 ° or more toward the light incident cross section in the vicinity of the light incident cross section. Characterized in that there is a decreasing inclination angle haptic region in the vehicle Light guide for surface light source device. The method of claim 1, With the thickness at the edge of the light incidence end face of the light guide as d, at least a part of the inclined angle diminished region exists in a region from 0.2d to 2d from the light incidence end face. Light guide for surface light source device. The method of claim 1, At least a portion of the inclined angle diminished region is characterized in that the distance from the light incident cross section exists within an area from 0.2 mm to 4 mm. Light guide for surface light source device. A light guide for a surface light source device, which is used to construct a surface light source device in combination with a primary light source and guides light generated from the primary light source. A light incidence cross section through which light generated from the primary light source is incident, a light exit face through which light is emitted, and a rear surface opposite to the light exit face; At least one of the light exit surface and the rear surface is a rough surface, and in the light exit surface and / or the rear surface formed of the rough surface, in a specific region near the light incident cross section, the average inclination angle of the surface is general other than the specific region. A maximum value larger than the average value of the average inclination angle of the general area is taken between the boundary between the area and the light incidence cross section, and smaller than the average value of the average inclination angle of the general area in the vicinity of the boundary with the light incidence cross section. Characterized in that Light guide for surface light source device. The method of claim 4, wherein In the position where the thickness at the edge of the light incidence cross section side of the light guide is taken as d, and the maximum value of the average inclination angle is taken, the distance to the boundary with the light incidence cross section of the specific region is in a range of d to 3d. Characterized in that Light guide for surface light source device. The method of claim 4, wherein The maximum value of the average inclination angle in the said specific area is in the range of 2.2 degrees or more and 4.0 degrees or less, It is characterized by the above-mentioned. Light guide for surface light source device. The method of claim 4, wherein The average value of the average inclination angle in the general region is in the range of 1.4 ° or more and less than 2.4 °. Light guide for surface light source device. The method of claim 4, wherein The said specific area | region has a distance from the boundary with the said general area | region to the boundary with the said light incident cross section in the range of 10 times-130 times the thickness in the edge of the said light incidence cross section side of the said light guide. doing Light guide for surface light source device. The method of claim 4, wherein The said specific area | region has a distance from the boundary with the said general area | region to the boundary with the said light incident cross section in the range of 10 mm-70 mm, It is characterized by the above-mentioned. Light guide for surface light source device. The said primary light source is arrange | positioned facing the light incident cross section of the light guide for surface light source devices of any one of Claims 1-9 characterized by the above-mentioned. Surface light source device. The method of claim 10, And a light deflecting element disposed on the light exit surface of the light guide and having a light entrance surface on which light exiting from the light exit surface of the light guide is incident and a light exit surface on the opposite side thereof. Surface light source device. The method of claim 11, The optical deflecting element has a plurality of prism rows extending along the light incidence cross section of the light guide on the light incident surface and arranged in parallel with each other, wherein each of the prism rows is formed at the light exit surface of the light guide. Characterized in that it has a first prism face on which light is incident and a second prism face on which inner light is reflected Surface light source device. The method of claim 10, The primary light source is characterized in that the linear light source Surface light source device. In the method of manufacturing the light guide for surface light source device of any one of Claims 1-9, Translucent synthetic resin is molded using a 1st type member which has a 1st transfer surface which transcribe | transforms the said light output surface, and a 2nd type member which has a 2nd transfer surface which transcribe | transforms the said back surface, Here, the said light emission On the basis of forming the first transfer surface and / or the second transfer surface for the transfer formation of the rough surface among the surface and the rear surface, the light incident end surface of the light guide and the light exit surface in the transfer surface region are formed. 1st roughening is performed in the state which provided the shielding effect about the vicinity of the edge of the edge corresponding to a boundary, It characterized by the above-mentioned. The manufacturing method of the light guide for surface light source devices. The method of claim 14, On the basis of forming the first transfer surface and / or the second transfer surface for the transfer formation of the light exit surface and the rough surface among the rear surfaces, a shielding effect on the transfer surface region corresponding to the general region is also obtained. Characterized in that the second roughening is carried out in a given state. The manufacturing method of the light guide for surface light source devices. The method of claim 15, A shielding effect on the vicinity of the edge is also imparted in the transfer surface region corresponding to the specific region on the basis of the second roughening. The manufacturing method of the light guide for surface light source devices. The method of claim 14, The first roughening and / or the second roughening are performed by etching. The manufacturing method of the light guide for surface light source devices. The method of claim 14, A first method of manufacturing a light guide for a surface light source device, characterized in that said first and / or second roughening are carried out by blasting. The method of claim 18, The provision of the shielding effect is performed by arranging the shielding member, and the shielding member is disposed away from the first transfer surface or the second transfer surface. The manufacturing method of the light guide for surface light source devices.

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