JP2007305544A - Light guide plate for plane light source device and plane light source device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plane light source device in which one of expensive light deflection members can be saved or none of them is used and high luminance and uniformity of luminance of the plane light source device can be obtained. <P>SOLUTION: The light guide plate for a plane light source device is used for composing a plane light source device by being assembled with a primary light source and guides light emitted from the primary light source, and is composed of a light incident face to which light emitted from the primary light source enters, a light-emitting face to emit a guided light and a rear face on an opposite side of the light-emitting face. A plurality of lens eye units are provided on the light-emitting face, and on a focusing position of the lens eye unit of the rear face or on a focusing point of the lens eye unit and on an optical axis, there is provided a light diffusing structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface light source device used for a liquid crystal display device and the like and a light guide used therefor.

  There are two types of surface light source devices used for liquid crystal display devices: an edge light method that attaches the light source to the edge of the light guide plate, and a direct light type method that diffuses light using the diffusion plate by placing the light source directly under the diffusion plate. In a liquid crystal display device having a relatively small screen size, such as a notebook PC and a PC monitor, an edge light system is mainly used.

  Currently, in the edge light system, optical sheets such as a diffusion film and a light deflection sheet (prism lens sheet) are disposed on the light exit surface side of the light guide plate, and high brightness and cost reduction are required.

  Optical members used for these, particularly light deflecting sheets (prism sheets) for deflecting light are expensive, and there is a strong demand for cost reduction including the installation cost.

In addition, when these optical members are combined, if a foreign substance is mixed in, the surface light source quality may be lowered.

FIG. 11 is a cross-sectional view showing a configuration example of a conventional surface light source device. A conventional surface light source device includes a light guide plate 31 and a linear light source (CCFL) 32 disposed on a side surface of the light guide plate.
In addition, a reflection sheet 35 disposed on the back surface of the light guide plate, a light diffusion film 33 disposed on the light emitting surface side of the light guide plate, a light deflection sheet (prism sheet) 34, and the like are sequentially disposed.

  However, the surface light source device having the above-described configuration has a problem that the cost of the optical member disposed for obtaining high luminance and the mounting cost (assembly cost) are high. Further, when a light guide plate and various optical sheet members are combined, there is a problem that optical quality deteriorates when foreign matter is mixed between the members.

In order to solve these problems, there is a surface light source device in which the function of a light deflecting member is imparted to a light guide plate to increase the brightness and reduce the number of optical members. It is disclosed in Patent Literature 1, Patent Literature 2 and Patent Literature 3.
Japanese Patent Laid-Open No. 9-21451 JP-A-10-39118 Japanese Patent Laying-Open No. 2005-71928

  FIG. 12 is a cross-sectional view showing the configuration of the surface light source device disclosed in Patent Document 1. As shown in FIG. A surface light source device 40 shown in FIG. 12 includes a light source 41, a light guide plate 42, and a reflection sheet 45. A light guide region is provided inside the light guide plate 42 so as to emit light from the light exit surface side of the light guide plate. 43, the light reflection layer 46, and the lens array 44 installed in the opening of the light guide region 43 are formed. Light emitted from the light source 41 enters the light guide plate 42 and is guided to the lens array 44 in the light guide region 43 to be collimated.

  FIG. 13 is a cross-sectional view showing the configuration of the surface light source device disclosed in Patent Document 2. As shown in FIG. A surface light source device 50 shown in FIG. 13 includes a light source 51, a light guide plate 52, a reflection sheet 55, and a lens sheet 54. The light guide plate 52 and the lens sheet 54 are formed by minute protrusions 53 formed on the lower surface of the lens sheet 54. Optically in close contact.

The light emitted from the light source 51 enters the light guide plate 52 and is guided to the lens sheet 54 by the minute protrusions 53 to be converted into parallel rays.

  FIG. 14 is a cross-sectional view showing the configuration of the surface light source device disclosed in Patent Document 3. As shown in FIG. A surface light source device 60 shown in FIG. 14 includes a light source 61, a light guide plate 62, and a reflective film 65. A prism array 64 is formed on the upper surface of the light guide plate 62, and a protrusion 63 is formed on the lower surface. The light emitted from the light source 61 enters the light guide plate 62, is reflected by the protrusion 63, is guided to the lens array 64, and is collimated.

  However, although the surface light source device shown in FIG. 12 controls the luminance uniformity of the surface light source by the distribution and depth of the light guide region 43, it is difficult to align the optical axis between the light guide region and the lens array. In order to form the light guide region, there is a problem that productivity and yield are inferior.

  Further, the surface light source device shown in FIG. 13 controls the luminance uniformity of the surface light source by the distribution of the minute protrusions 53, but the lens size and lens pitch corresponding to the distribution of the minute protrusions must be changed. In addition, it is difficult to align the optical axis of the lens, and it is difficult to obtain luminance uniformity.

  Further, the surface light source device shown in FIG. 14 controls the luminance uniformity of the surface light source by the distribution of the protrusions 53, but the size and arrangement of the protrusions need to be adjusted according to each lens. For products with a large screen size (15 inches or more) and protrusion pattern, there is a problem that the cost is high and the productivity is inferior. In order to obtain brightness uniformity, it is necessary to adjust the lens pitch or lens size according to the arrangement, or to adjust the exposure time to form protrusions, so a complicated optical design is required, and productivity is also increased. There is a problem of being inferior.

  The present invention has been made to solve such a problem, and can achieve high luminance and uniform luminance of the surface light source device without reducing or using one expensive light deflecting member. Therefore, the surface light source device has been found.

  According to the present invention, a light guide for a surface light source device that is used to construct a surface light source device in combination with a primary light source and guides light emitted from the primary light source, the light source being emitted from the primary light source. A light incident end surface on which light is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface, the light emitting surface having a plurality of lens array units, A light guide plate for a surface light source device having a light scattering mechanism at the focal position of the lens array unit on the back surface is provided.

  Further, according to the present invention, there is provided a light source for a surface light source device that is used to configure a surface light source device in combination with a primary light source, and that guides light emitted from the primary light source. It has a light incident end face on which emitted light is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface, and has a plurality of lens array units on the light emitting surface. A light guide plate for a surface light source device having a light scattering mechanism on the focal point and optical axis of the lens array unit on the back surface is provided.

  Furthermore, according to this invention, the surface light source device by which the said primary light source is arrange | positioned facing the light-incidence end surface of the above light guides for surface light source devices can be provided.

  In the surface light source device of the present invention configured as described above, the lens array is formed on the light guide plate exit surface, thereby providing the light guide plate with a light deflection function, thereby reducing expensive light deflection members, Cost can be reduced. In addition, it is possible to reduce yield reduction due to foreign matter contamination and defect factors such as scratches when the light deflection member is assembled.

Furthermore, since the light scattering mechanism is arranged at the focal position of each lens array, the light scattered by the light scattering mechanism is deflected in the normal direction by the lens array and is emitted from the light exit surface of the light guide plate. High brightness can be achieved.

  Furthermore, by forming a light scattering mechanism inside the light guide plate, the thickness of the light guide plate is not limited.

  According to another preferred aspect of the present invention, the lens array unit is a lens unit composed of a cylindrical lens or a polygonal column, and a ridge line of the lens array unit extends in a direction substantially perpendicular to the light incident end surface of the light guide plate. It is characterized by that.

  In the surface light source device of the present invention configured as described above, light incident on the light guide plate can be efficiently deflected in the normal direction, and emission of light in an oblique direction called a side lobe can be suppressed. The brightness in the normal direction can be improved.

  According to the present invention, a high-quality surface light source device can be provided efficiently and inexpensively.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view schematically showing the structure of a surface light source device 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an AA1 cross-sectional structure of the surface light source device 1. 3 is a cross-sectional view schematically showing a cross-sectional structure of the surface light source device 1 taken along the line B-B1.

  As shown in FIG. 1, in the surface light source device 1, a light guide plate 2 is formed by a rectangular plate-like transparent substrate 2a and a lens array 2b arranged on the light emission surface 2c of the transparent substrate 2a. A linear light source 3 is provided at one end of 2 in parallel with the light incident end face 2 d of the light guide plate 2.

  The linear light source 3 is covered with a reflector 4 and enters the light incident surface 2 d of the light guide plate 2 from the linear light source 3. A light scattering mechanism 6 is formed on the back surface 2 e of the light guide plate 2, and a silver reflection film or a white diffuse reflection film 5 is disposed below the light scattering mechanism 6.

  Examples of the material constituting the light guide plate 2 include methacrylic resin, polycarbonate resin, styrene resin, cyclic olefin resin, and amorphous polyester resin. A methacrylic resin, a polycarbonate resin, and a cyclic olefin resin are preferable, and a methacrylic resin is more preferable.

  The lens array is formed on both the light exit surface 2c and the back surface 2e of the light guide plate or on the light exit surface 2c of the light guide plate.

  FIG. 3 is a cross-sectional view of a light guide plate in which a lens array is formed only on the light exit surface. The lens array 2b formed on the light emitting surface 2c of the light guide plate 2 has a function of a convex lens.

  The light scattered and reflected by the light scattering mechanism 6 arranged for each lens array unit is deflected by the lens array 2b, so that the luminance in the normal direction of the surface light source device can be improved efficiently. it can.

The above operation will be described in detail with reference to FIG. 15 showing the positional relationship between the lens array 2b and the light scattering mechanism 6. The light scattered at a certain point O on the light scattering mechanism 6 is converted into light parallel to the x plane (a plane perpendicular to the x axis) by the refracting surface 2b1 expressed by Equation 1. Here, n is the refractive index of the transparent substrate 2a and the lens array 2b, and t is the shortest distance between the point O and the apex of the lens 2b1.

  FIG. 7 is a cross-sectional view of the light guide plate in which the lens array 2b is formed on both the light emitting surface 2c and the back surface 2e, and is an example in which the optical axes of the lens array units match each other.

  When forming on both the light emission surface 2c and the back surface 2e of a light-guide plate, it is preferable that the ridgeline of the lens array 2b formed in each surface is mutually parallel. When the ridge lines of the lens array 2b are parallel, light scattered and reflected by the light scattering mechanism 6 arranged for each lens array unit can be prevented from entering the adjacent lens array unit, which is efficient. The brightness in the normal direction of the surface light source device can be improved by deflecting the light. Further, the shape of the lens array 2b and the number of pitches of the lens array unit may be changed between the light emitting surface 2c and the back surface 2e of the light guide plate.

  FIG. 8 is a cross-sectional view of a light guide plate in which lens arrays 2b are formed on both the light emitting surface 2c and the back surface 2e, and is an example in which the optical axes of the lens array units on the light emitting surface and the back surface are shifted by a half pitch.

  As the shape of the lens array 2b, a cylindrical lens array having a semicircular shape or an elliptical shape in which the cross-sectional shape of each lens constituting the lens array 2b approximates the shape represented by Formula 1, or a polygonal prism such as a triangular prism. Examples thereof include a prism array or a cone, and a polygonal pyramid such as a quadrangular pyramid and a triangular pyramid, a hemispherical surface, an elliptical spherical surface, a triangular frustum, a quadrangular frustum, and a truncated cone.

For example, when the refractive index n of the transparent substrate 2a and the lens array 2b is 1.49, the cross-sectional shape of each lens is a semicircular shape represented by Formula 2, an elliptical cylindrical lens represented by Formula 3, Some of them can be used.

  In addition, by changing the shape of the lens array from each lens shape represented by Formula 1, it can be adjusted to a desired viewing angle. For example, in each lens shape represented by Expression 1, if the shortest distance t ′ between the lens apex and the light diffusion mechanism is larger or smaller than t in Expression 1, the viewing angle can be widened.

  For example, in each lens shape represented by Formula 1, when the lens is flattened, the viewing angle can be similarly increased. When it is desired to adjust the viewing angle in any one direction with respect to the vertical and horizontal directions of the surface light source device, it can be adjusted by a cylindrical lens array having a circular shape or an elliptical shape or a polygonal prism array such as a triangular prism. Also, if you want to adjust the viewing angle in both directions with respect to the vertical and horizontal directions of the surface light source device, you can adjust the cone, polygonal pyramid, hemispherical, elliptical spherical, triangular pyramid, square pyramid, Can be adjusted by a truncated cone.

  The lens array 2b is a cylindrical lens or a prism lens formed of a polygonal column, and it is more preferable that the lens array ridge line is formed in a direction extending in a direction perpendicular to the light incident end face of the light guide plate.

  As a result, the angular distribution of the light emitted from the lens array increases the ratio of light emitted in the normal direction of the light guide plate, and the emission of light in an oblique direction called a side lobe is suppressed, improving the brightness. I can plan.

  The light scattering mechanism 6 is formed on the back surface 2e of the light guide plate, which is the focal position of the lens array 2b, with the center of the light scattering mechanism corresponding to the optical axis of each lens array unit of the lens array 2b. Here, the plate thickness dimension of the light guide plate is the approximate focal length of the lens array 2b.

The minimum distance t between the apex (ridge line) of the lens array 2b and the back surface 2e of the light guide plate is given by Equation 1. However, it is also possible to shift the value by about 50% from t calculated by Equation 1 for viewing angle adjustment. For example, when the refractive index n of the transparent substrate 2a and the lens array 2b is 1.49, and each lens has a semicircular cylindrical lens as the cross-sectional shape of each lens, using Equation 2, the vertex (ridge line) of the lens array 2b The relationship between the minimum distance t of the back surface 2e of the light guide plate and the lens radius r is expressed by the following formula 4.

  Therefore, the thickness of the light guide plate is rt = 0.6t. In order to control the viewing angle, the thickness of the light guide plate can be changed in the range of about 0.3 to 0.9 t. Here, although t is an arbitrary design value, a light guide plate with smaller luminance spots is obtained when t is smaller.

  The method for forming the lens array 2b is not particularly limited, and a known technique can be used. For example, a lens array 2b is formed by using a mold in which the lens array 2b is formed, a method of manufacturing by cast molding, extrusion molding, injection molding, press molding or the like, or by previously molding a light guide plate without a lens array. 2P molding method using an ultraviolet curable resin on a light guide plate using a mold, or a lamination method in which a sheet on which a lens array is formed is bonded with an adhesive. In that case, known additives such as a release agent for improving the peelability between the resin and the mold and an ultraviolet absorber for delaying the deterioration due to ultraviolet rays can be added.

  Examples of the light scattering mechanism 6 formed on the back surface 2e of the light guide plate 2 include dot printing or stripe printing by printing with a white paint containing silica, titanium oxide or the like, or roughening of the light guide plate. The methods for dot printing, stripe printing, and surface roughening of the light guide plate are not particularly limited, and known techniques can be used. Examples of the printing technique include screen printing, gravure printing (intaglio printing), letterpress printing, and inkjet printing. Examples of the roughening of the surface of the light guide plate include thermal transfer using sandblasting, mat rolls, and the like.

  In dot-like printing and stripe-like printing, there is a gradation printing pattern in which the print dot area and the print stripe line width are small near the light source and increase toward the center of the light guide plate. In addition, in the roughening of the light guide plate, there is a gradation pattern in which the rough surface near the light source is similarly sparse and the rough surface becomes denser toward the center of the light guide plate. In this way, since the occupation density of the light scattering mechanism (occupation area of the light scattering mechanism pattern per unit area on the back surface of the light guide plate) can be appropriately changed depending on the location within the lower surface of the light guide plate, the upper surface 2d of the light guide plate 2 The amount of light emitted from can be controlled as desired.

  In the first embodiment of the present invention, the linear light source 3 has been described. Here, examples of the linear light source 3 include fluorescent tubes such as a hot cathode tube and a cold cathode tube. Further, instead of the linear light source, a light source in which point light sources such as light emitting diodes (LEDs) are arranged in parallel can be used. In the present embodiment, the incident from one side of the light guide plate has been described. When light is incident from both ends of the light guide plate, a uniform luminance distribution can be obtained by adjusting the gradation of the light scattering mechanism.

  The reflector 4 that covers the linear light source 3 is made of a reflective member on which silver or aluminum is deposited, or a white reflective member.

  Further, a further increase in luminance can be obtained by arranging a diffusion film for adjusting the angle characteristics of the emitted light on the light emitting surface side of the light guide plate, and further arranging a light deflecting member on the emitting side of the diffusion film. The diffusion film may be a type in which acrylic resin beads or silica beads are applied together with a binder, and has both a diffusion function and a light deflection function. The light deflection member is a transparent sheet in which a large number of columnar triangular prisms are continuously formed in a parallel state on the surface. One of the light deflecting members is preferably arranged in a direction in which the ridge of the prism is orthogonal to the lens array ridge line formed on the light emitting surface of the light guide plate.

  The operation of the planar light source device 1 of the first embodiment will be described with reference to FIG. The light emitted from the linear light source 3 is guided into the light guide plate from the light incident end face 2d of the light guide plate 2 and propagates through the light guide plate by total reflection. On the other hand, the light incident on the light scattering mechanism 6 formed on the back surface 2e of the light guide plate is reflected and diffused by the light scattering mechanism 6 and guided to the lens array 2b formed on the light exit surface 2c of the light guide plate. The light incident on the lens array 2b is collimated by the convex lens effect of the lens array and is emitted in the normal direction of the light guide plate.

  The light scattering mechanism 6 has a low density (area for dot printing, line width for stripe printing, rough surface density for sandblasting) near the light source, and the density increases toward the center of the light guide plate. By using the gradation pattern, the luminance distribution in the planar light source device is adjusted to a desired distribution.

Next, another embodiment of the present invention will be described.
FIG. 4 is a perspective view schematically showing the structure of the surface light source device 20 according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing an AA1 cross-sectional structure of the surface light source device 20. FIG. 6 is a cross-sectional view schematically showing a cross-sectional structure taken along the line B-B1 of the surface light source device 20. As shown in FIG. 5, the second embodiment is the same as the first embodiment except that the light scattering mechanism 6 is formed inside the light guide plate 2.

  Similarly to the first embodiment, the lens array 2b is formed only on both the light exit surface 2c and the back surface 2e of the light guide plate or only on the light exit surface 2c of the light guide plate. FIG. 6 is a cross-sectional view of a light guide plate in which a lens array is formed only on the light exit surface. FIG. 9 is a cross-sectional view of the light guide plate in which the lens array 2b is formed on both the light emitting surface 2c and the back surface 2e, and is an example in which the optical axes of the lens array units match each other. FIG. 10 is a cross-sectional view of the light guide plate in which the lens array 2b is formed on both the light emitting surface 2c and the back surface 2e, and is an example in which the optical axes of the lens array units on the light emitting surface and the back surface are shifted by a half pitch.

  As a method of forming bubbles inside the light guide plate, a lens array is formed on the light guide plate in advance, and laser light such as YAG laser or YVO4 laser is irradiated from the lens array side or the back surface side of the light guide plate, and then focused by the lens array. There is a method of generating bubbles by condensing a laser beam and heating it at a position where the lens is connected or at a focal position of a lens array.

  In addition, by forming an infrared absorption layer on the substrate surface of the light guide plate in advance by a known coating technique, forming a lens array directly on the infrared absorption layer, or laminating a lens array sheet created in a separate process After obtaining the light guide plate on which the lens array is formed, the laser is irradiated to the position in the infrared absorption layer focused by the lens array or the position in the infrared absorption layer that becomes the focal point of the lens array by laser irradiation as described above. There is a method of forming a light scattering layer by bubbles or phase separation by collecting and heating light.

  According to these methods, the density and size of the bubbles can be adjusted by changing the output intensity of the laser light according to the distance from the light source, and a desired pattern is formed inside the light guide plate. Can do.

As a method for forming a light diffusing resin layer inside the light guide plate, it can be obtained by the following molding method.
1. Co-extrusion molding method The material of the light guide plate is the light that is phase-separated by kneading inorganic fine particles with different refractive index, light diffusing resin containing organic fine particles, or transparent resins that are not compatible with each other. The diffusible resin is extruded from different dies to form a light diffusing resin layer inside the light guide plate.

2. Laminate molding method, hot press molding method A plurality of lens array units having the same transparent substrate thickness as the focal length of the lens array are formed on one side of the transparent substrate, and the lens array forming surface of the transparent substrate is further formed. A light diffusing resin layer is formed inside the light guide plate by attaching a light guide plate and a transparent base material provided with a light scattering mechanism at a position matching the focal position of each lens array unit on the opposite surface. Examples of the bonding method include laminating with an adhesive and hot pressing.

  Examples of the method for forming the light scattering mechanism include potting or printing of light diffusing resin by inkjet, screen printing, gravure printing (intaglio printing), letterpress printing, and the like. The method of forming the light diffusing resin layer inside the light guide plate has an advantage that it can cope with not only batch production but also continuous production.

  The operation of the planar light source device 20 of the second embodiment will be described with reference to FIG. The light emitted from the linear light source 3 is guided into the light guide plate from the light incident end face 2d of the light guide plate 2 and propagates through the light guide plate by total reflection. On the other hand, the light incident on the light scattering mechanism 6 formed inside the light guide plate is reflected, refracted or diffused by the light scattering mechanism 6 and guided to the lens array 2b formed on the light exit surface 2c of the light guide plate.

  The light incident on the lens array 2b is collimated by the convex lens effect of the lens array and is emitted in the normal direction of the light guide plate. Further, the light reflected by the light scattering mechanism 6 and not incident on the lens array 2b propagates inside the light guide plate and enters the lens array 2b again while being incident on the light scattering mechanism 6 or propagating inside the light guide plate. The light is emitted in the normal direction of the optical plate.

(Brightness measurement method of surface light source device)
The cold cathode tube of the obtained surface light source device was energized with a voltage of 12 V and a tube current of 7 mA and left to stabilize for about 20 minutes, and the luminance was measured from the light emitting surface side of the surface light source device. For luminance measurement, the luminance in the normal direction at the center of the surface light source device was measured with a luminance meter (BM7 manufactured by Topcon, viewing angle 2 °, measurement distance about 50 cm).

Example 1
A semicircular columnar lens array (cylindrical lens) having a lens radius and a lens pitch described in Table 1 was prepared on the upper surface of an acrylic resin plate having a thickness of 3.6 mm, a length of 115 mm, and a width of 150 mm by the 2P method using an acrylic UV curable resin. . At that time, the ridge line direction of the lens array was formed in parallel with the vertical 115 mm direction of the acrylic resin plate. Further, the end surface of the acrylic resin plate was finished to a mirror surface by polishing to prepare a light guide plate.

  Screen printing is performed on the lower surface of the light guide plate using white ink (solvent type) so that the center position (optical axis) of each lens array unit matches the center of the stripe width. A light scattering mechanism (white stripe pattern) was formed. At this time, a screen plate having a stripe pattern formed so that the center position (optical axis) of each lens array unit coincides with the center of the white stripe, and one side of the light guide plate on the side of 150 mm wide is used as the light incident surface. A silver reflective film (with SU115 pressure sensitive adhesive SU115 adhesive) was bonded to the end face of the light guide plate other than the light incident surface.

  Furthermore, a cold cathode tube having a diameter of 3 mm and a length of 150 mm is disposed on the light incident surface of the light guide plate, and is formed into a “U” shape so as to cover the cold cathode tube with a silver reflective reflector (Reiko Ruil mirror 150W05). Arranged. Furthermore, a diffusion film (Duji Tsujiden) was disposed on the upper surface of the lens array of the light guide plate to create a surface light source device. The luminance in the normal direction of the obtained surface light source device was measured, and the result is shown in Table 1.

Examples 2-3
A surface light source device was prepared in the same manner as in Example 1 except that the lens radius and lens pitch shown in Table 1 and the width and pitch of stripe printing were changed as the light scattering mechanism. The luminance in the normal direction of the obtained surface light source device was measured, and the result is shown in Table 1.

Example 4
A semicircular columnar lens array having a lens radius and a lens pitch shown in Table 1 was formed on the upper surface of an acrylic resin plate 1 having a thickness of 0.9 mm and a length of 125 mm and a width of 170 mm by the 2P method using an acrylic ultraviolet curable resin. At that time, the ridge line direction of the lens array was formed in parallel with the vertical 125 mm direction of the acrylic resin plate.

  Furthermore, white ink (UV curable type) is used on the lower surface of the acrylic resin plate 1 so that the center position (optical axis) of each lens array unit and the center of the stripe width match the uniform stripe pattern shown in Table 1. Screen printing was performed to form a light scattering mechanism (white stripe pattern).

  An acrylic resin plate 2 having a thickness of 4.5 mm and the same dimensions is bonded to the light scattering mechanism forming surface of the acrylic resin plate 1 with an acrylic ultraviolet curable resin by UV irradiation, thereby providing a light scattering mechanism layer inside. A light plate was obtained. The end face of the obtained light guide plate was cut and polished to obtain a light guide plate having a length of 115 mm and a width of 150 mm.

  Except for the above, a surface light source device was prepared in the same manner as in Example 1. The luminance in the normal direction of the obtained surface light source device was measured, and the result is shown in Table 1.

Comparative Example 1
An acrylic resin plate having a thickness of 6 mm was used as the light guide plate, and no lens array was formed on the upper surface of the light guide plate. Further, the apex angle was 90 ° on the upper surface of the diffusion film disposed on the light emitting surface side of the light guide plate. The triangular prism prism was arranged in the same manner as in Example 1 except that the surface light source device was formed by arranging the prism ridge line in a direction orthogonal to the light incident surface of the light guide plate. The luminance in the normal direction of the obtained surface light source device was measured, and the result is shown in Table 1.

As shown in Table 1, in Examples 1 to 4 of the present invention, improvement in luminance was recognized as compared with Comparative Example 1.

1 is a perspective view schematically showing a structure of a surface light source device according to a first embodiment of the present invention. It is sectional drawing which shows schematically the AA1 cross-section in the surface light source device of FIG. It is sectional drawing which shows schematically the BB1 cross-section in the surface light source device of FIG. It is a perspective view which shows roughly the structure of the surface light source device by 2nd embodiment of this invention. It is sectional drawing which shows roughly the AA1 cross-section in the surface light source device of FIG. FIG. 5 is a cross-sectional view schematically showing a B-B1 cross-sectional structure in the surface light source device of FIG. 4. It is sectional drawing which shows schematically the other structure of the surface light source device by 1st form of this invention. It is sectional drawing which shows roughly still another structure of the surface light source device by 1st form of this invention. It is sectional drawing which shows roughly the other structure of the surface light source device by the 2nd form of this invention. It is sectional drawing which shows roughly still another structure of the surface light source device by the 2nd form of this invention. It is sectional drawing which shows one structural example of the conventional surface light source device. It is sectional drawing which shows the other structural example of the conventional surface light source device. It is sectional drawing which shows the further another structural example of the conventional surface light source device. It is sectional drawing which shows the further another structural example of the conventional surface light source device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 20 Surface light source device 2 Light guide plate 2a Transparent base material 2b Lens array 3 Linear light source 4 Reflector 5 Diffuse reflection film 6 Light scattering mechanism

Claims (4)

A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
A light guide plate for a surface light source device having a plurality of lens array units on the light emitting surface and having a light scattering mechanism at a focal position of the lens array unit on the back surface. A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
A light guide plate for a surface light source device having a plurality of lens array units on the light emitting surface and having a light scattering mechanism on the focal point and optical axis of the lens array unit on the back surface. The lens array unit is a lens unit including a cylindrical lens or a polygonal column, and a ridge line of the lens array unit extends in a direction substantially perpendicular to a light incident end surface of the light guide plate. The light guide plate for surface light source devices of description. 4. The surface light source device, wherein the primary light source is disposed so as to face a light incident end surface of the light guide for the surface light source device according to any one of claims 1 to 3.

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