JP5948128B2 - Light guide plate - Google Patents

Description

  The present invention relates to a light guide plate, a surface light source device, and a transmissive image display device.

  A transmissive image display device such as a liquid crystal display device generally has a surface light source device as a backlight. The edge light type surface light source device includes a light guide plate (translucent resin sheet) and a light source that supplies light to an end surface of the light guide plate.

  2. Description of the Related Art As a light guide plate of an edge light type surface light source device, one having an uneven shape on an end surface which is a light incident surface is known (see Patent Document 1). Thus, it is expected that the light from the point light source (LED light source) is dispersed in the thickness direction of the light guide plate by providing the uneven shape on the end face.

JP 2008-10291 A

  However, in the light guide plate applied to the conventional surface light source device, the light incident from the end face cannot be made sufficiently uniform, and the brightness between adjacent light sources is insufficient near the end of the light guide plate. There is a problem that an area to be generated occurs. For this reason, it has been difficult to reduce the number of installed light sources.

  In addition, when there is a region where the brightness is insufficient at the peripheral portion of the light guide plate, the region where the brightness is insufficient is hidden by a frame of the transmissive image display device so as not to be seen from the front side. There is a need. When the frame becomes large, there is a problem that the image display device looks bad.

  Therefore, an object of the present invention is to provide a light guide plate, a surface light source device, and a transmissive image display device that can sufficiently disperse light incident from an end face and reduce a region where brightness is insufficient. .

The present invention relates to a light guide plate having an end surface that is an incident surface on which light is incident, a light emitting surface that is formed in a direction intersecting the end surface, emits light incident from the end surface, and a back surface that faces the light emitting surface. The thickness direction is the first direction, the longitudinal direction of the end face is the second direction, the first direction and the direction orthogonal to the second direction are the third direction, and the end face has the first direction A plurality of convex portions extending in the second direction and arranged in the second direction are formed, a groove portion extending in the first direction is formed between the adjacent convex portions, and the groove portion in the third direction is formed. The distance in the third direction between the deepest point C and the outer bending point B in the third direction of the convex portion is H, and the distance in the second direction between the bending points B of the adjacent convex portions is Is P, and the distance in the second direction between the bending points B of one convex portion is F, and the distance F is set to be equal to or less than the interval P. When the axis parallel to the second direction passing through B is the x axis and the axis parallel to the third direction passing through the deepest point C is the y axis, the contour shape of the groove satisfies the following formula (1) y with a conical curve represented by (x), k _a is the kurtosis of conic, the following formula (3) and the following equation (4) filled in the case where the following formula (2) is satisfied, following When the expression (5) is satisfied, the following expression (6) and the following expression (7) are satisfied. When the following expression (8) is satisfied, the following expression (9) and the following expression (10) are satisfied. When Formula (11) is satisfied, a light guide plate that satisfies Formula (12), Formula (13), and Formula (14) below is provided.

  In this light guide plate, a plurality of convex portions are provided on the end surface, and a groove portion extending in the first direction is formed between adjacent convex portions. The contour shape of the groove portion is represented by y (x) satisfying the above-described formula (1), the above-described formulas (2) to (4), the above-described formulas (5) to (7), and the above-described formula. (8) to (10) or the above formulas (11) to (14) are satisfied. By these convex portions and grooves, the light incident from the end face is sufficiently dispersed in the second direction, which is the longitudinal direction of the end face, so that the light emitted from the light sources adjacent in the second direction intersect each other. The position to be moved can be brought closer to the end face. As a result, it is possible to reduce the area where the brightness is insufficient at the end of the light exit surface, and to reduce the number of light sources installed. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

  Moreover, since the front-end | tip part (end part of the outer ends of a 3rd direction) of a convex part has a flat surface (surface parallel to a 1st direction and a 2nd direction) equivalent to the distance F. The tip of the convex portion is less likely to be chipped.

Moreover, as a structure which exhibits the said effect | action more effectively, when said Formula (2) is satisfy | filled when the outline shape of a groove part satisfy | fills following Formula (15) and following Formula (16), said Formula (5) ) Is satisfied, the following expression (17) and the following expression (18) are satisfied. When the above expression (8) is satisfied, the following expression (19) and the following expression (20) are satisfied, and the above expression When (11) is satisfied, a configuration that satisfies the following formula (21) and the following formula (22) is included.

Further, as a configuration that achieves the above action more effectively, the distance F is set to be equal to or less than half of the interval P, and when the contour shape of the groove portion satisfies the above expression (2), the following expression (23) and When the following expression (24) is satisfied and the above expression (5) is satisfied, a configuration that satisfies the following expression (25) and the following expression (26) may be mentioned.

  Moreover, this invention provides a surface light source device provided with said light guide plate and the light source which supplies light to the end surface of the said light guide plate. Since this surface light source device includes the light guide plate according to the present invention, the position where the light emitted from the light sources adjacent to each other in the second direction crosses each other can be brought close to the end surface. As a result, it is possible to reduce the area where the brightness is insufficient at the end of the light exit surface, and to reduce the number of light sources installed. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

  In addition, the present invention includes a light transmission plate including the above light guide plate, a light source that supplies light to an end surface of the light guide plate, and a transmissive image display unit that is illuminated by light emitted from the light emission surface of the light guide plate. A type image display apparatus is provided. Since the transmissive image display device includes the light guide plate according to the present invention, the position where the light emitted from the light sources adjacent in the second direction intersects each other can be brought close to the end surface. As a result, the area where the brightness is insufficient at the end of the light exit surface can be reduced, and the number of installed light sources can be reduced. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

  According to the present invention, a light guide plate capable of sufficiently dispersing light incident from an end face and reducing a region where brightness is insufficient, a surface light source device including the light guide plate, and a transmissive image display device are provided. can do. According to the present invention, since the light incident from the end face can be dispersed in the longitudinal direction of the end face, the frame portion for concealing the region where the brightness of the peripheral portion of the light exit surface is insufficient can be narrowed.

It is sectional drawing which shows one Embodiment of a transmissive image display apparatus provided with a surface light source device. It is a top view of the side in which the reflective dot of the light-guide plate is formed. It is a front view which expands and shows the positional relationship of the LED light source arrange | positioned facing the edge part and this edge part of a light-guide plate. It is a graph which shows an example of the light emission distribution of a LED light source. It is a front view which shows one Embodiment of a transmissive image display apparatus provided with a light-guide plate. It is a front view which expands and shows the convex-shaped part and groove part which were provided in the edge part of the light-guide plate. In the case of 0% <F / P ≦ 25 %, depending on the aspect ratio H / P and kurtosis k _a of the groove is a table showing the differences in uniformity. It is a graph which shows the area | region where the calculation result of the uniformity was favorable in the case of 0% <F / P ≦ 25%. In the case of 25% <F / P ≦ 50 %, depending on the aspect ratio H / P and kurtosis k _a of the groove is a table showing the differences in uniformity. It is a graph which shows the area | region where the calculation result of the uniformity was favorable when 25% <F / P ≦ 50%. In the case of 50% <F / P ≦ 75 %, depending on the aspect ratio H / P and kurtosis k _a of the groove is a table showing the differences in uniformity. It is a graph which shows the area | region where the calculation result of the uniformity was favorable when 50% <F / P ≦ 75%. In the case of 75% <F / P ≦ 100 %, depending on the aspect ratio H / P and kurtosis _{k a} of the groove is a table showing the differences in uniformity. It is a graph which shows the area | region where the calculation result of the uniformity was favorable in the case of 75% <F / P ≦ 100%. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning comparative example 1. It is a figure showing the light ray image after the entrance of the light which injected from the edge part about the light-guide plate which concerns on Example 1. FIG. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning comparative example 2. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning Example 2. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning comparative example 3. It is a figure showing the light ray image after the entrance of the light which injected from the edge part about the light-guide plate which concerns on Example 3. FIG. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning comparative example 4. It is a figure showing the light ray image after the entrance of the light which injected from the edge part about the light-guide plate which concerns on Example 4. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent element, and the overlapping description is abbreviate | omitted. The dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a cross-sectional view showing a transmissive image display device including an embodiment of a light guide plate according to the present invention. The transmissive image display device 100 shown in FIG. 1 is mainly composed of a surface light source device 20 and a transmissive image display unit 30. The surface light source device 20 is an edge light type surface light source device that includes a light guide plate 1 and a light source 3 that is provided on a side of the light guide plate 1 and supplies light to the light guide plate 1.

  As shown in FIG. 1, the transmissive image display unit 30 is disposed to face the light guide plate 1 on the light exit surface S1 side of the light guide plate 1. The transmissive image display unit 30 is, for example, a liquid crystal display unit having a liquid crystal cell.

  Further, the transmissive image display device 100 may have a configuration in which various films 51 are disposed between the transmissive image display unit 30 and the light guide plate 1. Examples of the various films 51 include a diffusion film, a prism film, and a brightness enhancement film.

The light guide plate 1 has a substantially rectangular parallelepiped shape, and an exit surface S1, the opposite side of the back S2 of the exit surface S1, and four end surfaces (side _surfaces) S3 1 to S3 ₄ intersecting the emitting surface S1 and the back surface S2 Have. In the present embodiment, the four end surfaces S3 _{1 to} S3 ₄ are substantially orthogonal to the emission surface S1 and the back surface S2.

  The light guide plate 1 is made of a translucent resin. The translucent resin is a resin that transmits light. The refractive index of the translucent resin is usually 1.49 to 1.59. As the translucent resin used for the light guide plate 1, methacrylic resin is mainly used. As the translucent resin used for the light guide plate 1, other resins may be used, or styrene resins may be used. As the translucent resin, acrylic resin, styrene resin, carbonate resin, cyclic olefin resin, MS resin (acrylic and styrene copolymer), and the like can be used. When the light guide plate 1 is applied to a liquid crystal display device (transmission type image display device 1), a light diffusing agent, an ultraviolet absorber, a heat stabilizer, a photopolymerization stabilizer, or the like may be added to the light guide plate.

  The light guide plate 1 is preferably a poly (meth) acrylic acid alkyl resin sheet, a polystyrene sheet, or a polycarbonate resin sheet, and among these, a polymethyl methacrylate resin sheet (PMMA resin sheet) is preferable. The translucent resin sheet may contain diffusing particles. The surface (exit surface S1) opposite to the surface (back surface S2) on which the reflective dots 12 of the translucent resin sheet are formed may be a flat surface as in the present embodiment, but has an uneven shape. You may do it. In addition, it is preferable that the thickness of a translucent resin sheet is 1.0 mm or more and 4.5 mm or less.

  The back surface S2 of the light guide plate 1 is subjected to reflection processing (for example, silk printing) for irregularly reflecting light. As a printing method performed as reflection processing, ink jet printing may be performed in addition to silk printing. Alternatively, as a method of reflection processing, dot-shaped irregularities may be imparted by laser irradiation instead of printing, or dot-shaped irregularities are imparted by injection molding using a shape-shaped mold to which the shape is imparted. Or you may give a dot-shaped unevenness | corrugation by extrusion molding using the shape roll by which the shape was engraved. In printing dot patterns, ink having diffusing particles that diffuse light is used. Further, the gradation change is given so that the diameter of each dot (printing dot) constituting the dot pattern increases as the distance from the light source side increases. The maximum thickness of each reflective dot 12 is preferably 20 μm or less, more preferably 15 μm or less.

  As shown in FIG. 2, the plurality of reflective dots 12 are arranged on the back surface S2 so as to be separated from each other. FIG. 2 is a plan view when the light guide plate is viewed from the back side. In FIG. 2, the light source 3 is also shown for convenience of explanation. In FIG. 2, the reflective dots 12 are spaced apart from each other. The number and arrangement pattern of the reflective dots 12 are adjusted so that uniform planar light is efficiently emitted from the emission surface S1.

As shown in FIGS. 1 and 2, the light source 3 is disposed on the side of a pair of end faces S3 ₁ and S3 ₂ facing each other. The light source 3 is a point light source such as an LED. As shown in FIG. 2, a plurality of point light sources are arranged along two sides of the light guide plate 1 that are opposed to each other among four sides that form, for example, a rectangle.

In the following description, the thickness direction of the light guide plate 1 is referred to as the Z direction (first direction), and the longitudinal direction of the end faces S3 ₁ and S3 _{2 on} which the light from the light source 3 is incident is referred to as the X direction (second direction). The direction orthogonal to the Z direction and the X direction is referred to as the Y direction (third direction).

The plurality of light sources 3 are discretely arranged along the longitudinal direction (second direction) X of the end surfaces S3 ₁ and S3 ₂ that are incident surfaces. FIG. 3 is an enlarged front view showing the positional relationship between the end portion of the light guide plate and the LED light source disposed facing the end portion. As shown in FIG. 3, the arrangement | positioning space | interval L of the light source 3 is about 5 mm-150 mm, and the space | interval L is about 8 mm in this embodiment. The distance D between the light source 3 and the end faces S3 ₁ and S3 ₂ is about 0.5 mm to 5 mm.

The distance y shown in FIG. 3, the end surface S3 _1, S3 in the case _{where 2} in shape does not have, of the point distribution of emitted light of the light source 3 adjacent to each other overlap on the calculated P _C Y direction (third direction) The distance is shown. A distance half of the distance y is expressed as y / 2.

  The light source 3 may be a white LED, and a plurality of LEDs may be arranged in one place to constitute one light source unit. For example, as one light source unit, LEDs of three colors different in red, green, and blue may be arranged close to each other. And the light source unit which has several LED is discretely arrange | positioned according to the arrangement | positioning direction mentioned above. In such a case, it is preferable that different LEDs are arranged as close as possible.

  As the LED light source, those having various light output distributions can be used. Specific examples of the LED light source type include a Lambertian type, a shell type, and a side emission type.

  FIG. 4 is a graph showing an example of the light output distribution of the LED light source. The relationship between the emission angle φ and the emission light intensity is shown with the emission light intensity in the normal direction of the LED light source 3 (emission angle φ = 0 °) being 1.0 (reference). In the LED light source 3 having the light emission distribution shown in FIG. 4, the full width at half maximum is about 60 °. In addition, you may use the LED light source which has another light emission distribution.

  As the light source 3 of the present embodiment, for example, a Lambertian LED light source with a 120-degree light distribution having a width W (length in the X direction) of 3.5 mm is applicable.

FIG. 5 is a front view showing the image display apparatus according to the embodiment of the present invention. In the transmissive image display device 100, a frame 101 that covers the peripheral edge of the transmissive image display unit 30 is formed. Accordingly, the peripheral edge (end face) of the light guide plate 1 indicated by a broken line in FIG. 5 is not visible from the front side. In addition, the size of the frame is set in the vicinity of the end faces S3 ₁ and S3 ₂ where the light source 3 of the light guide plate 1 is disposed so that a region with insufficient brightness cannot be visually recognized from the front side.

  As shown in FIG. 5, the light guide plate 1 has a rectangular shape. The size of the light guide plate 1 in a plan view is selected so as to match the target screen size of the transmissive image display device 100, but is usually 250 mm × 440 mm or more, preferably 1020 mm × 1800 mm or less. The planar view shape of the light guide plate 30 is not limited to a rectangle but may be a square, but in the following, it will be described as a rectangle unless otherwise specified.

  In addition, the rectangle of 250 mm × 440 mm or more means a rectangle having one side of 250 mm or more and the other side of 440 mm or more. Further, the rectangle of 1020 mm × 1800 mm or less means a rectangle having one side of 1020 mm or less and the other side of 1800 mm or less.

Here, on the end surfaces S3 ₁ and S3 ₂ of the light guide plate 1, as shown in FIGS. 6A and 6C, a plurality of convex portions 41 protruding outward in the Y direction are formed. The convex portion 41 extends in the thickness direction (Z direction) of the light guide plate 1, and the plurality of convex portions 41 are arranged side by side in the longitudinal direction (X direction) of the end faces S3 ₁ and S3 ₂ . The plurality of convex portions 41 are arranged in parallel.

A plurality of groove portions 44 having a curved contour shape are formed between the convex portions 41 adjacent in the Y direction. The plurality of groove portions 44 are concave groove portions extending in the Z direction. In other words, the groove portion 44 is formed by a pair of side surfaces 43 and 43 of the convex portion 41 adjacent in the Y direction. In the cross section perpendicular to the Z direction, the contour of the groove 44 forms a conical curve. The end portions on the inner side in the Y direction of the pair of side surfaces 43, 43 are the deepest point C in the Y direction of the groove portion 44. The tip (outer end in the Y direction) of the convex portion 41 forms a surface 42 (hereinafter referred to as a flat surface 42) parallel to the X direction and the Z direction. In other words, a plurality of groove portions 44 are formed on the end surfaces S3 ₁ and S3 ₂ of the light guide plate 1, and a flat surface 42 is formed between the groove portions 44 and 44 adjacent in the Y direction.

  Here, the distance in the Y direction between the deepest point C of the groove 44 and the outer bending point B in the Y direction of the convex portion 41 is defined as H. The bending point B is an intersection of the flat surface 42 and the side surface 43. The distance H is the depth of the groove 44, or in other words, the protruding length of the convex portion 41. Further, let P be the interval in the X direction between the bending points B of the adjacent convex portions 41. The interval P is the width of the groove 44 in the X direction. Let F be the distance in the X direction between the bending points B of one convex portion 41. The distance F is the length between the end portions (bending points B) in the X direction of the flat surface 42 of the convex portion 41, that is, the width in the X direction.

  As shown in FIG. 4C, the distance F is equal to or less than the interval P. That is, a relationship of 0 <F / P ≦ 100% is established in the ratio between the distance F and the distance P (that is, the ratio of the flat surface 42).

Hereinafter, the contour shape of the groove 44 will be described in more detail. As shown in FIG. 6B, when the axis parallel to the X direction passing through the bending point B is the x axis and the axis parallel to the Y direction passing through the deepest point C is the y axis, the contour shape of the groove 44 is And y (x) satisfying the following formula (1).

Y (x) satisfying the above equation (1) corresponds to a conical curve which is a curve obtained when the conical surface is cut by a plane. k _a is the sharpness of the conic curve, and is a number selected from the range of −1 to +1.

In the light guide plate 1, the aspect ratio H / P and the kurtosis ka of the groove 44 are set to values within _a suitable range according to the ratio F / P between the distance F and the interval P. Specifically, it is as follows.

That is, when the ratio F / P between the distance F and the distance P is in the range of the following formula (2),

The aspect ratio H / P and the kurtosis k _a satisfy the following expressions (3) and (4).

When the ratio F / P between the distance F and the distance P is in the range of the following formula (5),

The aspect ratio H / P and the kurtosis k _a satisfy the following expressions (6) and (7).

When the ratio F / P between the distance F and the distance P is in the range of the following formula (8),

The aspect ratio H / P and the sharpness k _a satisfy the following formulas (9) and (10).

When the ratio F / P between the distance F and the distance P is in the range of the following formula (11),

The aspect ratio H / P and kurtosis _{k a} satisfies the following formula (12) to (14).

More preferable range of the aspect ratio H / P and kurtosis k _a is as follows. If the distance F and the ratio F / P between the distance P is in the range of formula (2), the aspect ratio H / P and kurtosis k _a satisfies the following formula (15) and (16).

Further, when the distance F and the ratio F / P between the distance P is in the range of the above formula (5), the aspect ratio H / P and kurtosis k _a is satisfied the following equation (17) and (18) Yes.

Further, when the distance F and the ratio F / P between the distance P is in the range of the above formula (8), the aspect ratio H / P and kurtosis k _a is satisfied the following equation (19) and (20) Yes.

Further, when the distance F and the ratio F / P between the distance P is in the range of the equation (11), the aspect ratio H / P and kurtosis _{k a} is satisfied the following equation (21) and (22) Yes.

Further, when the distance F is less than half the spacing P (F / P ≦ 50% ), even more preferred value of the aspect ratio H / P and kurtosis k _a is as follows. If the distance F and the ratio F / P between the distance P is in the range of formula (2), the aspect ratio H / P and kurtosis k _a satisfies the following formula (23) and (24).

Further, when the distance F and the ratio F / P between the distance P is in the range of the above formula (5), the aspect ratio H / P and kurtosis k _a is satisfied the following equation (25) and (26) Yes.

  Next, a method for forming the light guide plate 1 will be described. The light guide plate 1 can be formed by methods such as extrusion molding, cast molding, and injection molding. The thickness t of the light guide plate 1 is not particularly limited, but is preferably, for example, 1.0 mm to 10.0 mm, more preferably 1.5 mm to 8.0 mm, and 2.0 mm to 4.0 mm is particularly preferable.

The uneven shapes (convex portions 41) of the end faces S3 ₁ and S3 ₂ of the light guide plate 1 can be formed by cutting, laser processing, injection molding, or the like. In the cutting process, the light guide plate 1 is cut using a cutting tool, so that the groove portions 44 are formed in the end faces S3 ₁ and S3 ₂ of the light guide plate 1 and the convex portions 41 are formed. In laser processing, the groove part 44 is formed in the end surfaces S3 ₁ and S3 ₂ of the light guide plate 1 using laser light, and the convex part 41 is formed. In the case of the injection molding method, it is preferable that an opposite mold having a shape corresponding to the convex portion 41 is provided on the inner wall of the injection mold.

  If the interval (pitch) in the X direction of the plurality of convex portions 41 is too small, there is a concern about a decrease in processing accuracy, and if it is too large, the region where the brightness is insufficient in the peripheral portion of the light guide plate 1 with the uneven shape. Therefore, when the light guide plate 1 is incorporated in the liquid crystal display device 100, a frame portion for concealing the peripheral portion of the light guide plate 1 so as not to be seen from the liquid crystal display screen becomes large. The pitch of the plurality of convex portions 41 is preferably 0.03 mm to 10 mm.

According to such a light guide plate 1 according to the present embodiment, light from a plurality of light sources 3 that are arranged to face the side surfaces S3 ₁ and S3 ₂ of the light guide plate 1 are incident from the side surfaces S3 ₁ and S3 _2. Planar light can be emitted from the emission surface S1 orthogonal to (intersect) the side surfaces S3 ₁ and S3 ₂ . Then, light incident from the side surfaces S3 ₁ and S3 _{2 of the} light guide plate 1 is refracted by the side surface 43 of the convex portion 41 and spread in the X direction. Thus the brightness at the edge of the light guide plate 1 (side S3 _1, S3 ₂ vicinity) can reduce the area to be insufficient. According to the light guide plate 1, it is possible to reduce a region where the brightness is insufficient between adjacent light sources, and thus it is possible to reduce the number of installed light sources 3.

  Moreover, since the front end portion of the convex portion 41 has a flat surface 42 corresponding to the distance F, the front end portion of the convex portion 41 is not easily chipped.

Further, according to the transmission type image display part 30 and the transmission type image display apparatus 100 including the same according to the present embodiment, faces the side surface S3 _1, S3 ₂ as the incident surface of the light guide plate 1, the side surface S3 _1, comprising a plurality of light sources 3 which are discretely arranged in S3 ₂ in the longitudinal direction (X direction), the light from these light sources 3 is incident from the side _S3 1, S3 _2, perpendicular to the side surface _S3 1, S3 ₂ The planar light can be emitted from the outgoing surface S1. Then, light incident from the side surfaces S3 ₁ and S3 _{2 of the} light guide plate 1 is refracted by the side surface 43 of the convex portion 41 and spread in the X direction. Thereby, the area | region where brightness is insufficient in the edge part (incident surface vicinity) of the light-guide plate 1 can be reduced. Therefore, the frame part for concealing the region where the brightness is insufficient at the end of the light guide plate 1 so as not to be seen from the display screen can be reduced. The degree of freedom in designing the frame portion that is the peripheral portion of the display screen of the transmissive image display device 1 can be increased.

(Example)
Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.

First, a light guide plate having no convex portion formed on the end face was prepared, and the point light source 3 was disposed so as to face the end face. As shown in FIG. 3, as the point light sources 3, Lambertian LEDs with a width of 3.5 mm and 120-degree light distribution are arranged at intervals of 8 mm. And the position y where the light which injected into the light-guide plate cross | intersect was calculated from adjacent LED3,3. The specification and measurement conditions of the light guide plate according to the comparative example are shown below.
Light guide plate: Resin material PMMA (manufactured by Sumitomo Chemical Co., Ltd.)
Refractive index of air n ₁ 1.00
Refractive index n _{2 of} light guide plate 1.49
Light source width W 3.5mm
Distance L between light sources 8.0 mm
Length of light source in Y axis direction 2.0mm
Incident angle α ₁ 60.0 [deg]
Incident angle α ₂ 35.5 [deg]
Distance between light source and end face D 2 μm
Distance X direction of the light source and to the entrance point _{P i x 1} ≒ 0mm
Distance in the X direction from the incident point P _i to the light intersection P _c x ₂ = 2.25 mm
The distance y in the Y direction from the incident point P _i to the light intersection P _c = 3.15 mm
Distance y / 2 = 1.6 mm to point PC _{/ 2} where the distance in the Y direction is half of the intersection point _Pc

Next, a light receiver is set on a plane perpendicular to the Y direction through the light intersection P _C {y} and the point P _{c / 2} {y / 2} calculated in the above comparative example. The illuminance distribution was calculated with ray tracing software. For convenience of calculation, the calculation is performed for the case where only one LED light source 3 is present, and the illuminance distribution is assumed on the assumption that there are a plurality of LED light sources by superimposing the illuminance distribution according to the arrangement interval of the LED light sources 3 later. It was created. And the uniformity was calculated about the obtained illumination distribution.

(Search range)
As shown in FIG. 6 (A), for the combination of the aspect ratio H / P and kurtosis k _a of the groove 44, and perform the calculations of the plurality of patterns. Specifically, with respect to the aspect ratio H / P, 0.05 intervals (that is, 0.3, 0.35, 0.4, 0.45, 0.5, 0) in the range of 0.3 to 1.0. .55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1). The kurtosis _{k a,} 0.2 intervals in the range of -1 to +1 (i.e. -1, -0.8, -0.6, -0.4, -0.2,0,0.2,0 .4, 0.6, 0.8, 1). Calculations were performed for 165 patterns of each of these combinations. In addition, about the ratio F / P [%] of the flat surface 42, it was set as 11 kinds of 10% intervals in the range of 0 to 100%.

(Search results)
Hereinafter, the ratio F / P of the flat surface 42 is classified into four ranges, and search results are shown. 7, in the case of 0% <F / P ≦ 25 %, depending on the aspect ratio H / P and kurtosis _{k a} of the groove 44 is a chart showing the difference in uniformity. FIG. 7 illustrates a case where a light receiver is set at the point P _{c / 2} {y / 2}.

(When 0% <F / P ≦ 25%)
FIG. 8 is a chart showing a region where the calculation result of the uniformity of the illuminance distribution is good when 0% <F / P ≦ 25%. Based on FIG. 7, a region where the calculation result of the uniformity was good was searched, and the range of FIG. 8 was selected. Specifically, a range in which the uniformity of illuminance is approximately 17.5% or more is set as a range where the result is good. The ranges shown in FIG. 8 are as follows. In Figure 8, the range shown by the solid line L ₁ is a uniformity of approximately the range of 17.5% or more illumination, the following formula (3), corresponds to a range indicated by (4).

In Figure 8, the range indicated by the one-dot chain line L ₂ is a uniformity of approximately 20% or more ranges of intensity, following equation (15) corresponds to the range indicated by (16).

In Figure 8, a range indicated by a dashed line L ₃ is a uniformity of approximately 22.5% over the range of illumination, the following equation (23) corresponds to the range indicated by (24).

(25% <F / P ≦ 50%)
9, in the case of 25% <F / P ≦ 50 %, depending on the aspect ratio H / P and kurtosis _{k a} of the groove 44 is a chart showing the difference in uniformity. FIG. 10 is a chart showing a region where the calculation result of the uniformity of the illuminance distribution is good when 25% <F / P ≦ 50%. Based on FIG. 9, a region where the calculation result of the uniformity was good was searched, and the range of FIG. 10 was selected. Specifically, a range in which the uniformity of illuminance is approximately 17.5% or more is set as a range where the result is good. The ranges shown in FIG. 10 are as follows. In Figure 10, the range indicated by the solid line L ₄ are a uniformity of approximately the range of 17.5% or more illumination, formula (6), corresponds to a range indicated by (7).

In Figure 10, the range indicated by the dot-dash line L ₅ represents a uniformity of approximately 20% or more ranges of intensity, following equation (17) corresponds to the range indicated by (18).

In Figure 10, the range indicated by the dashed line _{L 6} is a uniformity of approximately 22.5% over the range of illumination, the following equation (25) corresponds to the range indicated by (26).

(50% <F / P ≦ 75%)
11, in the case of 50% <F / P ≦ 75 %, depending on the aspect ratio H / P and kurtosis _{k a} of the groove 44 is a chart showing the difference in uniformity. FIG. 12 is a chart showing a region where the calculation result of the uniformity of the illuminance distribution is good when 50% <F / P ≦ 75%. Based on FIG. 11, an area where the calculation result of uniformity was good was searched, and the range of FIG. 12 was selected. Specifically, a range in which the uniformity of illuminance is approximately 17.5% or more is set as a range where the result is good. The ranges shown in FIG. 12 are as follows. In Figure 12, the range indicated by the solid line L ₇ is a uniformity of approximately the range of 17.5% or more illumination, formula (9), corresponds to a range indicated by (10).

In Figure 12, the range indicated by the one-dot chain line L ₈ is a uniformity of approximately 20% or more of a range of illumination, the following formula (19), corresponds to a range indicated by (20).

(75% <F / P ≦ 100%)
13, in the case of 75% <F / P ≦ 100 %, depending on the aspect ratio H / P and kurtosis _{k a} of the groove 44 is a chart showing the difference in uniformity. FIG. 14 is a chart showing a region where the calculation result of the uniformity of the illuminance distribution is good when 75% <F / P ≦ 100%. Based on FIG. 13, an area where the calculation result of the uniformity was good was searched, and the range of FIG. 14 was selected. Specifically, a range in which the uniformity of illuminance is approximately 17.5% or more is set as a range where the result is good. The ranges shown in FIG. 14 are as follows. In FIG. 14, the range indicated by the solid line L <b> ₉ is a range in which the illuminance uniformity is approximately 17.5% or more, and corresponds to the ranges indicated by the following formulas (12) to (14).

In Figure 14, the range indicated by the one-dot chain line L ₁₀ is a uniformity of approximately 20% or more ranges of intensity, following equation (21) corresponds to the range indicated by (22).

(Ray image after incident (0% <F / P ≦ 25%))
FIG. 15A shows a light guide plate according to Comparative Example 1, in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 15B shows an illuminance distribution. In Figure _15, illustrates the case of _{H / P = 1, k a} = 0.8, the convex portion 41 is a F / P = 10%.

FIG. 16A shows the light guide plate according to the first embodiment, in which light receivers are set at the intersections P _C {y} and P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 16B represents the illuminance distribution. In Figure 16, the point _{P c} / 2 uniformity is (are excellent uniformity) which was the largest in {y / 2} convex portion _{41 (H / P = 0.45,} k a = 0.8, The case of F / P = 10%) is illustrated. Here, the uniformity is a ratio (minimum value / maximum value) of the minimum value and the maximum value of illuminance in the X direction.

The uniformity of Comparative Example 1 shown in FIG. 15A was 56.0% at the intersection P _C {y} and 10.5% at the point P _{c / 2} {y / 2}. On the other hand, the uniformity of Example 1 shown in FIG. 16A was 91.8% at the intersection P _C {y} and 23.2% at the point P _{c / 2} {y / 2}. Thus, it can be seen that the case of Example 1 shown in FIG. 16A is superior in uniformity at the intersections P _c {y} and P _{C / 2} {y}.

(Ray image after incident (25% <F / P ≦ 50%))
FIG. 17A shows a light guide plate according to Comparative Example 2, in which light receivers are set at the intersections P _C {y} and P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 17B represents the illuminance distribution. In Figure 17 _illustrates the case of H / P = 1, k a = -0.8, the convex portion 41 is a F / P = 40%.

FIG. 18A illustrates a light guide plate according to the second embodiment in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 18B shows the illuminance distribution. In Figure 18, the convex portion 41 uniformity at the point _{P c / 2 {y / 2} } was maximum _{(H / P = 0.6, k} a = 0.8, F / P = 40%) of The case is illustrated.

The uniformity of Comparative Example 2 shown in FIG. 17A was 51.0% at the intersection P _C {y} and 13.6% at the point P _{c / 2} {y / 2}. On the other hand, the uniformity of Example 2 shown in FIG. 18A was 85.0% at the intersection P _C {y} and 22.8% at the point P _{c / 2} {y / 2}. Thus, it can be seen that the case of Example 2 shown in FIG. 18A is superior in uniformity at the intersection points P _c {y} and P _{C / 2} {y}.

(Ray image after incidence (when 50% <F / P ≦ 75%))
FIG. 19A shows a light guide plate according to Comparative Example 3, in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 19B shows the illuminance distribution. In Figure 19, it is shown for the case of _{H / P = 0.3, k a} = 0.8, the convex portion 41 is a F / P = 60%.

FIG. 20A illustrates a light guide plate according to the third embodiment in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2} and the illuminance distribution in these light receivers is traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 20B shows the illuminance distribution. In Figure 20, the convex portion 41 uniformity at the point _{P c / 2 {y / 2} } was maximum _{(H / P = 0.65, k} a = 0.8, F / P = 60%) of The case is illustrated.

The uniformity of Comparative Example 3 shown in FIG. 19A was 56.3% at the intersection P _C {y} and 13.2% at the point P _{c / 2} {y / 2}. On the other hand, the uniformity of Example 3 shown in FIG. 20 (A) was 80.0% at the intersection P _C {y} and 21.0% at the point P _{c / 2} {y / 2}. Thus, it can be seen that the case of Example 3 shown in FIG. 20A is superior in uniformity at the intersections P _c {y} and P _{C / 2} {y}.

(Ray image after incidence (when 75% <F / P ≦ 100%))
FIG. 21A shows a light guide plate according to Comparative Example 4, in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 21B shows an illuminance distribution. In Figure 21, it is shown for the case of _{H / P = 0.3, k a} = 0.8, the convex portion 41 is a F / P = 90%.

FIG. 22A illustrates a light guide plate according to the fourth embodiment, in which a light receiver is set at the intersection P _C {y} and the point P _{c / 2} {y / 2}, and the illuminance distribution in these light receivers is ray-traced. The calculation result calculated by software is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm ² ]. FIG. 22B shows an illuminance distribution. In Figure 22, the convex portion 41 uniformity at the point _{P c / 2 {y / 2} } was maximum _{(H / P = 0.7, k} a = 0.6, F / P = 90%) of The case is illustrated.

The uniformity of Comparative Example 4 shown in FIG. 21A was 47.2% at the intersection P _C {y} and 12.3% at the point P _{c / 2} {y / 2}. On the other hand, the uniformity of Example 4 shown in FIG. 22A was 80.7% at the intersection P _C {y} and 21.0% at the point P _{c / 2} {y / 2}. Thus, it can be seen that Example 4 shown in FIG. 22A is superior in uniformity at the intersections P _c {y} and P _{C / 2} {y}.

  As mentioned above, although this invention was concretely demonstrated based on the embodiment, this invention is not limited to the said embodiment. For example, the point light sources may be arranged along one side surface extending in the long side direction of the optical sheet, or may be arranged along one side surface extending in the short side direction. Good. Moreover, the structure by which a point light source is arranged in two side surfaces extended in a long side direction may be sufficient, and the structure arranged in one side surface extended in a short side direction may be sufficient. In addition, it is preferable that the point light source is arrange | positioned in the position corresponding to the groove part 44 formed of the inclined surface 43 of the adjacent convex-shaped part 41. FIG.

The longitudinal direction of the side surface serving as the incident surface is the Y direction in the side surfaces S3 ₁ and S3 ₂ facing the X direction, and the X direction in the side surfaces S3 ₃ and S3 ₄ facing the Y direction (FIG. 2).

DESCRIPTION OF SYMBOLS 1 ... Light guide plate, 3 ... Light source, 12 ... Reflection dot, 20 ... Surface light source device, 30 ... Transmission type image display part, 41 ... Convex part, 42 ... Flat surface (tip surface), 43 ... Inclined surface, 44 ... groove, 51 ... film, 100 ... transmission type image display device (liquid crystal display device), 101 ... frame, B ... inflection point, C ... deepest point, S1 ... exit surface, S2 ... back, _S3 1 to S3 4 _... end surface.

Claims (5)

In a light guide plate having an end surface that is an incident surface on which light is incident, a light exit surface that is formed in a direction intersecting with the end surface, and that emits light incident from the end surface, and a back surface that faces the light exit surface.
The thickness direction is the first direction, the longitudinal direction of the end face is the second direction, the first direction and the direction orthogonal to the second direction are the third direction,
The end surface is formed with a plurality of convex portions extending in the first direction and arranged in the second direction,
A groove portion extending in the first direction is formed between the adjacent convex portions,
The distance in the third direction between the deepest point C in the third direction of the groove and the outer bending point B in the third direction of the convex portion is H,
The interval in the second direction between the bending points B of the adjacent convex portions is P,
The distance in the second direction between the bending points B of one convex portion is F,
The distance F is set to be less than the interval P,
When the axis parallel to the second direction passing through the bending point B is the x axis and the axis parallel to the third direction passing through the deepest point C is the y axis,
The contour shape of the groove is
With a conical curve expressed by y (x) satisfying the following formula (1), k _a is the kurtosis of the conic,
When the following formula (2) is satisfied, the following formula (3) and the following formula (4) are satisfied,
When the following formula (5) is satisfied, the following formula (6) and the following formula (7) are satisfied,
When the following formula (8) is satisfied, the following formula (9) and the following formula (10) are satisfied,
When the following formula (11) is satisfied, the following formula (12), the following formula (13), and the following formula (14) are satisfied.
Light guide plate.













The contour shape of the groove is
When the formula (2) is satisfied, the following formula (15) and the following formula (16) are satisfied,
When the formula (5) is satisfied, the following formula (17) and the following formula (18) are satisfied,
When the formula (8) is satisfied, the following formula (19) and the following formula (20) are satisfied,
The light guide plate according to claim 1, wherein, when the formula (11) is satisfied, the following formula (21) and the following formula (22) are satisfied.







The distance F is not more than half of the interval P,
The contour shape of the groove is
When the formula (2) is satisfied, the following formula (23) and the following formula (24) are satisfied,
The light-guide plate of Claim 1 or 2 which satisfy | fills following formula (25) and following formula (26) when the said Formula (5) is satisfy | filled.



The light guide plate according to any one of claims 1 to 3,
A surface light source device comprising: a light source that supplies light to the end face of the light guide plate. The light guide plate according to any one of claims 1 to 3,
A light source for supplying light to the end face of the light guide plate;
A transmissive image display device comprising: a transmissive image display unit that is faced by light emitted from the light emitting surface of the light guide plate.