WO2008066154A1

WO2008066154A1 - Surface illuminant element, and image display device having the element

Info

Publication number: WO2008066154A1
Application number: PCT/JP2007/073167
Authority: WO
Inventors: Seiji Kinoshita
Original assignee: Kuraray Co., Ltd.
Priority date: 2006-12-01
Filing date: 2007-11-30
Publication date: 2008-06-05
Also published as: TW200834187A; JPWO2008066154A1

Abstract

Provided is a surface illuminant element of an edge light type, in which at least one linear light source is arranged on the side face of an optical guide plate. The surface illuminant element is characterized in that a pattern formed of a plurality of troughs parallel to the light source is formed on the bottom face of the optical guide plate, in that the degree of inclination of the troughs with respect to the bottom face is substantially 30 degrees or more and 45 degrees or less, and in that a pitch (P) or the distance between the centers of any adjacent two of the troughs satisfies the following formulas: Hv/tan(Φin) ≤ P ≤L × Hv × 0.3 (1); and Φin = (C3R3 + C2R2 + C1R + C0) + 2R - 90.0º (2), C0 = -1.25 × 102, C1 = 1.31 × 101, C2 = -3.30 × 10-1, and C3 = 2.43 × 10-3. Also provided is an image display device, which is made excellent in an image quality by equipping the surface illuminant element with the optical guide plate capable of reducing the formation of dark lines, as might otherwise degrade the image quality, while avoiding or reducing the use of a diffusion sheet.

Description

Specification

Surface light source element and image display device including the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to an edge light type surface light source element having a plurality of linear light sources and an image display device using the same, and in particular, a liquid crystal display device and an illumination that require high screen quality. The present invention relates to an edge light type surface light source element used for a signboard device and the like, and an image display device using the same.

Background art

[0002] For example, there are two types of surface light source elements used in an image display device, an edge light method and a direct light method, but since an edge light type surface light source element has a linear light source on the side surface of a light guide plate, Compared to direct-type surface light source elements, it has the feature of being effective in reducing the thickness, and is widely used as a display unit for portable notebook computers and monitors.

In such an edge light type surface light source element, a light guide plate having a main surface of a generally rectangular shape made of a transparent resin or the like is used. This light guide plate has an incident end surface on which a primary light source such as a linear light source or a point light source is disposed between an output surface that is one of the main surfaces and a bottom surface that is another main surface facing the output surface. Have. The light emitted from the primary light source enters the light guide plate from the incident end surface of the light guide plate, guides the inside of the light guide plate, scatters by white printing dots applied to the bottom surface of the light guide plate, or temporarily guides the light. After being emitted from the bottom surface of the light plate, scattered by a reflection sheet having a reflection surface facing the bottom surface and incident again on the light guide plate, the light is emitted from the emission surface toward the liquid crystal display element portion.

[0004] In a printed dot type light guide plate in which white printed dots are printed on the bottom surface of the light guide plate, the luminance distribution in the viewing direction is adjusted to be uniform by adjusting the size, density, etc. of the dots. ing. Thereby, the light emitted from the primary light source enters the light guide plate from the incident end surface, and this incident light is emitted from the emission surface toward the liquid crystal display element while being guided through the light guide plate.

[0005] Since the surface light source element using such a printed dot type light guide plate uses light scattering by white printed dots, the light emitted from the light guide plate has a light distribution distribution spread over a wide angle. As shown, the orientation and brightness in the front direction which are important as a surface light source element cannot be obtained sufficiently. Therefore, in order to increase the brightness by condensing the emitted light in the front direction with the light guide plate force, a plurality of diffusion sheets are used, or in addition to the diffusion sheet, a prism sheet is further used.

[0006] The prism sheet has a force S that can increase the front brightness more efficiently, and since the scratches that cause deterioration in the appearance quality are likely to enter the sharp apex of the prism, It is essential to dispose the diffusion sheet on the exit surface side of the prism sheet, resulting in lower brightness, lower production efficiency, and higher costs. Further, there is a problem that it is difficult to reduce the thickness of the element as the number of parts of these optical sheets increases. Therefore, these sheets are 100 to 300 Hm! /, And thin ones are used! /, The force S, wrinkles are likely to occur, not only causing defective products in the assembly process, The generation of wrinkles on the prism sheet significantly reduces the illumination quality of the surface light source element.

[0007] In order to avoid the use of a prism sheet, a proposal has been made to direct the light emitted from the exit surface in the viewing direction by forming a prism on the exit surface of the light guide plate, the bottom surface facing the exit surface, and the like! (For example, see Patent Documents 1 and 2).

[0008] For example, Patent Documents 1 and 2 disclose a prism optical element integrated light guide plate. Such a prism optical element integrated light guide plate has a V-shaped groove array in a direction intersecting with each of the emission surface and the bottom surface. As a result, the light incident from the incident end face is taken into the bottom surface and the reflected light is efficiently reflected in the direction of the exit surface. Further, when the light is emitted from the emission surface via the prism formed on the emission surface, the incident light incident in the direction perpendicular to the incident end surface can be emitted at an angle close to the front direction.

Patent Document 1: Japanese Patent Laid-Open No. 10-282342

Patent Document 2: Japanese Patent Laid-Open No. 2003-114432

Disclosure of the invention

Problems to be solved by the invention

[0010] In the prism optical element integrated light guide plate described in Patent Document 1 or 2, the ridges or ridges formed on the exit surface and the bottom surface are V-shaped groove arrays having apex angles of acute angles. Edge-lighted surface using a prism optical element integrated light guide plate having such V-shaped groove rows In the light source element, it is difficult to emit light in the front direction. In addition, although it is controlled in the direction that requires the emitted light, it is very difficult to change the brightness continuously. Brightness and darkness of brightness become prominent depending on the angle, and only the glare is conspicuous on the surface. When the exit surface of the rectangular light guide plate is viewed from an oblique direction, a dark line is seen and the screen quality is deteriorated. Therefore, in such a prism optical element integrated light guide plate, it is necessary to eliminate glare and dark lines by using a plurality of diffusion sheets, lowering the brightness, worsening the viewing angle characteristics, and increasing the thickness of the device. In addition, the production process has become complicated and has become a problem.

Accordingly, an object of the present invention is to provide a surface light source element having excellent screen quality by a light guide plate that can reduce the occurrence of dark lines that reduce image quality while avoiding or reducing the use of a diffusion sheet, and Means for solving the problem is to provide an image display device including the surface light source element.

The present invention is an edge light type surface light source element in which at least one linear light source is disposed on a side surface of a light guide plate, and the light guide plate has an emission surface, a bottom surface facing the emission surface, and a small amount. It has an incident end face for entering light emitted from a linear light source provided on at least one side surface, and includes a reflecting means for reflecting light on the bottom surface side of the light guide plate,

The normal of the X—Y plane consisting of the X axis and the Y axis perpendicular to the X axis is the z axis,

The linear light source is arranged parallel to the X axis,

The reflecting means and the light guide plate are arranged in parallel to the XY plane,

It is configured in the order of the reflection means and the light guide plate in the Z-axis direction,

An incident end face of the light guide plate is parallel to the X-Z plane, and a pattern comprising a plurality of concave stripes parallel to the X axis is formed on the bottom surface, and an X on the incident end face side of the plurality of concave stripes. A slope parallel to the axis, and the slope of the slope with respect to the bottom is substantially not less than 30 degrees and not more than 45 degrees;

The minimum value P and the maximum value P of the pitch P, which is the distance between the centers of two adjacent grooves

MIN M

And the ratio P / P is 1.5 or more, The surface light source element is characterized in that a pitch P, which is a distance between the centers of any two adjacent grooves, satisfies the following formula.

[0013] ΗνΛ η (Φίη) ≤ Ρ ≤ LXHvX0.3 (1)

here

Φίη = (CR ³ + CR ² + C R + C) + 2R— 90.0. (2)

3 2 1 0

C = — 1.25X 10 ² , C = 1.31X10 ¹ , C = —3.30X10— C = 2.43X10— ³

0 1 2 3

P: Distance between the centers of any two adjacent grooves (pitch) (unit: mm)

R: Average slope (unit degree) with respect to the bottom of the slope parallel to the X axis on the incident end face side of the groove

Hv: Height of the groove (unit: mm)

L: Distance from the incident end face of the light guide plate to the minimum pitch P (unit: mm)

MIN

c ~

0 c: Coefficient

Three

[0014] The present invention also provides:

Said surface light source element,

The linear light sources are respectively disposed on two incident end faces facing the light guide plate, and the plurality of concave stripes have the inclined surfaces parallel to the X axis with respect to the two incident end faces, respectively. It may be characterized by

[0015] The present invention also provides:

Said surface light source element,

A cross section of the groove formed on the bottom surface of the light guide plate may be V-shaped.

[0016] The present invention also provides:

Said surface light source element,

The cross section of the groove formed on the bottom surface of the light guide plate may be trapezoidal.

[0017] The present invention also provides:

Said surface light source element,

A pattern composed of a plurality of ridges parallel to the Y-axis is formed on the exit surface of the light guide plate It may be characterized by that.

[0018] The present invention also provides:

Said surface light source element,

The cross section of the ridge formed on the exit surface of the light guide plate may be trapezoidal.

[0019] Further, the present invention provides:

An image display device comprising a transmissive display element on an emission surface side of the surface light source element according to any one of the above.

The invention's effect

[0020] The surface light source element of the present invention is an edge light type surface light source element, and the pitch P of the concave stripes on the bottom surface facing the light exit surface of the light guide plate provided in the surface light source element of the present invention is the minimum value P. Maximum

MIN

The ratio P / P with the value P is 1.5 or more and is adjusted to satisfy the following conditions

MAX MAX MIN

By doing so, it has a function to prevent deterioration of the screen quality due to dark lines while ensuring the uniformity of luminance.

[0021] ΗνΛ η (Φ ίη) ≤ Ρ ≤ L X HvX 0.3 (1)

here

Φ ίη = (CR ³ + CR ² + C R + C) + 2R— 90.0. (2)

3 2 1 0

C = — 1.25 X 10 ² , C = 1.31 X 10 ¹ , C = —3.30 X 10— C = 2.43 X 10— ³

0 1 2 3

P: Distance between the centers of any two adjacent grooves (pitch) (unit: mm)

Hv: Height of the groove (unit: mm)

MIN

c ~

0 c: Coefficient

Three

[0022] In addition, when the linear light sources are arranged on the two incident end faces facing each other of the light guide plate, they are guided from the linear light sources as compared with the case where there are two linear light sources on one incident end face. The incident efficiency to the light plate is improved, and since it can be incident from the two incident end faces, the thickness of the light guide plate can be reduced when the luminance performance is the same, leading to a thinner surface light source element. Ma In addition, since there are incident end faces at both ends, it is only necessary to adjust the surface luminance distribution for the exit area from the incident end face on one side to the center line with the incident end face opposite to the incident end face. Therefore, the light guide plate having one incident end face In comparison, it is easy to make the surface luminance distribution uniform.

[0023] Further, when the cross section of the concave stripe installed on the bottom surface of the light guide plate is V-shaped, the incident end face side of the V-shaped concave stripe among the light guided through the light guide plate Those directly incident on the slope are totally reflected and can be emitted at an angle very close to the front direction, improving the brightness in the front direction.

[0024] Further, when the cross section of the concave stripe installed on the bottom surface of the light guide plate is trapezoidal, the luminance in the front direction can be improved as in the V shape, and the light guide plate can be manufactured by a manufacturing method by injection molding. The production efficiency can be increased because it is excellent in releasability from the mold during fabrication.

[0025] Further, in the case where a ridge is disposed on the exit surface of the light guide plate, at least one incident end surface of the light guide plate is installed in parallel to the X axis, and the projecting ridge axis is disposed on the exit surface of the light guide plate. If the X-axis direction is the horizontal direction and the Y-axis direction is the vertical direction, the reflected light from the bottom surface of the light guide plate can be deflected in the horizontal direction by the ridges arranged on the exit surface. As a result, viewing angle characteristics can be improved.

[0026] In particular, when the protrusions on the emission surface have a trapezoidal cross-sectional shape parallel to the plane consisting of the X axis and the Z axis, the protrusions are arranged on the bottom surface of the light guide plate. Out of the light reflected by the recessed stripes, the light near the normal direction of the emission surface is emitted from the top and bottom surfaces of the trapezoidal shape so that it can be emitted in the front direction as it is, and high brightness can be obtained. When the light is incident on the slope, the emitted light can be spread in the horizontal direction, so it has a function that can maintain a wide viewing angle characteristic.

As described above, the light guide plate provided in the surface light source element of the present invention is configured to dispose incident light from a linear light source at a predetermined pitch on the bottom surface facing the output surface, thereby forming the output surface. Dark lines when viewed from an angle can be eliminated. Further, when the projection is provided on the exit surface, the exit direction of the exit light from the light guide plate can be controlled, so that it is possible to provide an image display device with high brightness and excellent viewing angle characteristics.

Brief Description of Drawings

FIG. 1 is a schematic view showing an example of a surface light source element of the present invention. FIG. 2 is an angular luminance distribution of outgoing light in the vertical direction from the light guide plate provided in the surface light source element of the present invention.

FIG. 3 is a typical locus of light emitted in the front direction in the angular luminance distribution of light emitted in the vertical direction from the light guide plate provided in the surface light source element of the present invention.

FIG. 4 is a typical light trajectory forming the second peak in the angular luminance distribution of light emitted in the vertical direction from the light guide plate provided in the surface light source element of the present invention.

FIG. 5 is a diagram for explaining that the second peak disappears in the angular luminance distribution of outgoing light in the vertical direction in a light guide plate where dark lines are generated.

[Fig. 6] A surface light source element with a light guide plate that generates dark lines! (A) Front view when observed from the exit surface, (b) と -Ζ plane at points e and f This is the angular luminance distribution from the front plane direction to the non-incident end face side of the emitted light in the parallel plane.

FIG. 7 is a schematic diagram for explaining a trapezoidal shape formed as a ridge on the exit surface of the light guide plate provided in the surface light source element of the present invention.

FIG. 8 is a schematic view showing an example of the surface light source element of the present invention, where (a) a side view when observed in the Y-axis direction from a side parallel to the X-Z plane, and (b) It is a side view when observed in the X-axis direction from the side parallel to the Y-Z plane.

FIG. 9 is a diagram for explaining the surface characteristics of trapezoidal ridges protruding from the light exit surface of the light guide plate provided in the surface light source element of the present invention.

FIG. 10 is an example of a configuration diagram of a backlight unit used for evaluating luminance and dark lines of a light guide plate.

FIG. 11 is an example of a configuration diagram of a backlight unit used for evaluating luminance and dark lines of a light guide plate.

Explanation of symbols

1: Light guide plate

2: ridge

3: concave

4: Primary light source

4a: Linear light source 4b: Reflector

5: Reflective sheet

5a: diffusion sheet

6: Output surface

7: Bottom

8: Incident end face (side face)

8a: Reflective end face (side face)

8b: Reflective end face (side face)

9: V-shaped groove

9a: Slope on the incident end face side of the V-shaped groove

9b: Slope on the anti-incident end face side of the V-shaped groove

10: Surface light source element

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] The best mode for carrying out the present invention will be described below. In the following drawings, for the convenience of explanation, the vertical and horizontal scales of each part are illustrated by schematic diagrams that are randomly changed.

[0031] First, a surface light source element of the present invention includes a light guide plate that is a flat transparent structure formed of a transparent resin, a linear light source disposed on one side of the light guide plate, and a lower surface of the light guide plate. It is generally composed of the reflective sheet placed!

[0032] The light guide plate can be made of a transparent resin having a high light transmittance. As the transparent resin that can be used, for example, methacrylic resin, acrylic resin, polycarbonate resin, polyester resin, and cyclic polyolefin resin can be widely used.

[0033] One surface of the light guide plate is an emission surface, and a bottom surface is disposed to face the emission surface. In addition, a linear light source is disposed on at least one side surface of the light guide plate, and this side surface is an incident end surface.

In the present invention, the incident end face may be at least one place, but may be a plurality of places. When the incident end face is one place, the reflection end face is provided on the side face other than the incident end face. Is formed. [0035] A typical example in the case where the incident end face has two power stations is an example in which there are linear light sources on mutually opposing faces, and the reflecting end faces are formed on both side faces. The incident end face of the two power stations must satisfy the condition that it is parallel to the concave line formed on the bottom surface, and if any convex line is formed on the output surface, both must be orthogonal to the convex line. is required.

[0036] A linear light source is disposed toward the incident end face. Any linear light source may be used, but it is a linear light source in which a large number of point light sources such as cold cathode tubes, fluorescent tubes, and LED light sources are arranged. Also good.

[0037] In the present invention, a reflecting means for reflecting light is provided on the side contacting the bottom surface of the light guide plate, and the reflecting means has a function of causing light emitted from the bottom surface of the light guide plate to enter the light guide plate again. Have. A reflectance of 95% or more is desirable because of high light utilization efficiency. Examples of the reflector material include aluminum, silver, and stainless steel foils, white paint, and foamed PET resin. In order to increase the light utilization efficiency, it is desirable that the material has a high reflectance. This includes silver and foamed PET. Also, in order to improve the brightness uniformity, the material should be diffusely reflected. This includes foamed PET.

[0038] In the light guide plate provided in the surface light source element of the present invention, recesses formed at a predetermined pitch are formed on the bottom surface of the light guide plate. These recesses are formed by extending a recess in a cross section in one direction. The cross-sectional shape of these grooves may be a desired shape such as a triangle, a wedge, another polygon, a wave, or a semi-elliptical shape, but with respect to the bottom surface of the slope located on the linear light source side of the grooves. The slope is substantially 30 ° force 45 °, and the average slope with respect to the bottom of the slope is approximately equal. If the angle is 45 ° or more, the brightness changes at an angle close to the front direction of the exit surface of the light guide plate, and the dark line cannot be eliminated unless a large number of diffusion sheets are placed. On the other hand, if the angle is 30 ° or less, it becomes difficult to increase the outgoing light in the front direction.

[0039] Here, the height of the concave stripe formed on the bottom surface may gradually increase as the distance from the linear light source increases. In this case, the average value of the height of each groove is used as the value Hv representing the height of the groove in equation (1). Further, the shape may be gradually changed as the distance from the linear light source is increased. For example, when the cross section includes a trapezoidal groove, the length of the upper and lower bases of the trapezoid is the angle formed by the inclined surface of the trapezoidal groove with respect to the bottom surface. Including the case where it is gradually different while being kept substantially constant. These configurations Thus, the uniformity of the in-plane luminance can be further improved.

[0040] Further, the pitch of the grooves formed on the bottom surface is calculated by a functional equation given by equation (2), where R is the average slope of the concave surface of the linear light source side inclined surface with respect to the bottom surface. By using Φin and the height Hv of the groove, the minimum value Pbotom that can be obtained from Eq. (3) is used. I play. The pitch of the grooves is usually narrower as you move away from the linear light source! Similarly, when the linear light source is arranged on the two incident end faces facing each other of the light guide plate, the pitch becomes narrower as it approaches the center of the light guide plate. At this time, the ratio P / P between the minimum value P and the maximum value P of the pitch P, which is the distance between the centers of the two adjacent ridges, is 1.5 or more, preferably 2 or more.

MIN MAX MAX MIN

Shigu 2.5 or more is more preferable. With these configurations, it is possible to further increase the balance between the luminance performance in the front direction and the uniformity of luminance in the plane.

[0041] Φ ίη = (CR ³ + CR ² + C R + C) + 2R— 90.0. (2)

3 2 1 0

C =-1.25 X 10 ² , C = 1.31 X 10 ¹ , C = —3.30 X 10— C = 2.43 X 10— ³

0 1 2 3

R: Average slope of the slope parallel to the X-axis on the linear light source side of the concave strip relative to the bottom (unit degree)

c to c: Coefficient

0 3

[0042] Pbotom = ΗνΛ η (Φ ίη) (3)

Hv: Height of the groove (unit: mm)

P: Distance between the centers of any two adjacent ridges (pitch) (unit: mm) Pbotom: Minimum value that P can take (unit: mm)

[0043] In any case, the light is refracted by using the bottom surface and the reflection sheet to control the structure of the bottom surface so that the light is emitted with a desired intensity from the output surface. Are performed in combination with each other or in combination with other adjustment means.

[0044] Particularly, in the light guide plate provided in the surface light source element of the present invention, when the cross section of the concave stripe provided on the bottom surface is V-shaped, the V-shaped concave stripe is arranged in parallel to the incident end face, and the pitch When a V-shaped concave stripe is arranged in the range, the occurrence of dark lines can be suppressed when the exit surface of the light guide plate is viewed from an oblique direction. Furthermore, when a diffusion sheet and a prism sheet are mounted on the light guide plate, the luminance in the front direction can be increased. [0045] In addition, the average slope of the slope of the cross-section of each concave groove provided on the bottom surface is in the range of 30 ° to 45 °, and preferably in the range of 35 ° to 45 ° in terms of excellent viewing angle characteristics. More preferably, it is set within the range of 37.5 ° to 42.5 ° in terms of high brightness and excellent viewing angle characteristics. The height is set in the range of 0.001 mm to 0.1 mm, preferably in the range of 0.005 mm to 0.05 mm in terms of moire reduction, and in order to make the surface brightness near the linear light source uniform. More preferably, it is set within the range of 0.005 mm to 0.02 mm.

[0046] In addition, when the shape of the cross section of the groove provided on the bottom surface is constant, it is desirable to make the optical design easy. Therefore, it is desirable that the cross section of the groove is constant. In this case, the average inclination of the slopes of the individual grooves is equal to the average slope R of the slopes parallel to the X axis on the incident end face side of the grooves.

[0047] When the hypotenuse of the cross section of the groove provided on the bottom surface is linear, the average slope R with respect to the bottom surface of the slope parallel to the X axis on the incident end surface side of the groove is the inner angle of the cross section formed by the bottom surface and the slope. Therefore, it is the average value of the base angle, which is usually an acute angle.

[0048] The principle of wire suppression will be described below by taking as an example the case where a concave shape having a cross-sectional force shape is formed on the bottom surface of the light guide plate.

An example representing the surface light source element of the present invention is shown in FIG. In FIG. 1, in the light guide plate provided in the surface light source element of the present invention, one incident end face is installed so as to be parallel to the plane consisting of the X axis and the Z axis perpendicular thereto, and the incident end face is linear. A light source is installed, and the bottom of the light guide plate has a Y-axis perpendicular to the X-axis and a Z-axis parallel to the Y-Z plane. The cross section parallel to the XZ plane is formed parallel to the trapezoidal convex axis on the exit surface. In the outgoing light from the outgoing surface of the light guide, the outgoing component in the direction parallel to the X axis is the horizontal component, and the outgoing component in the direction parallel to the Y axis is the vertical component.

[0049] Fig. 2 shows the angular luminance distribution of the outgoing light of the vertical component from the light guide plate provided in the surface light source element of the present invention. The light emitted from the light guide plate provided in the surface light source element of the present invention has a distribution in which there are many outgoing components in the front direction and in the vicinity of ± 45 °. The peak in the front direction is called the first peak, and the peak formed by the outgoing component near ± 45 ° is called the second peak.

[0050] Fig. 3 shows a locus of light propagating in a typical light guide plate of the emitted light forming the first peak. The Outgoing light that forms the first peak is incident on the Y axis among the light emitted from the linear light source, enters the light guide plate from the incident end face of the light guide plate, and is guided through the light guide plate. The light c traveling at a shallow angle in the Z direction with respect to the parallel straight line a is totally reflected by the inclined surface 9a on the bottom surface of the concave strip 9 on the bottom surface and emitted from the exit surface. This light is important because it has a large effect on the brightness in the front direction.

[0051] FIG. 4 shows a locus of light propagating through a typical light guide plate of the emitted light forming the second peak. Outgoing light that forms the second peak is incident on the Y axis among the light emitted from the linear light source, enters the light guide plate from the incident end face of the light guide plate, and is guided through the light guide plate. The light c traveling in the Z direction with respect to the parallel straight line a is totally reflected at the bottom surface between the concave strips 9 on the bottom surface, and then the slope 9a on the linear light source side of the concave strip 9 on the bottom surface. It is totally reflected again and emitted from the exit surface.

[0052] Generally, the luminance distribution on the exit surface of the surface light source element is desired to be a distribution in which the luminance decreases as it goes toward each end surface where the central luminance increases. For this reason, the space | interval of the concaves arrange | positioned at the bottom face of the light-guide plate with which a surface light source element is provided becomes narrow as it goes to the center.

[0053] When the interval between the bottom grooves is reduced, the light c traveling in the light guide plate that has formed the second peak is completely reflected on the bottom surface between the grooves as shown in FIG. The light can no longer be reflected, and is directly incident on the inclined surface 9a on the incident end face side of the concave stripe. The light incident on the inclined surface once passes through the inclined surface 9a on the incident end face side and re-enters the light guide plate on the inclined surface 9b on the counter incident end face side. Instead of exiting from the exit surface. That is, a part of the emission angle forming the second peak is lost.

[0054] Furthermore, Fig. 6 shows the angular distribution of luminance in the vertical direction at two locations e and f close to the location where the dark line is generated on the exit surface of the surface light source element where the dark line is generated. ing . The grooves arranged on the bottom surface facing the point e are close to each other, and cannot be totally reflected on the bottom surface between the grooves. On the other hand, the concave line disposed on the bottom surface facing the point f is a point that can be totally reflected on the bottom surface between the concave line and the concave line, and can be totally reflected on the slope of the concave line. In this example, the difference in luminance between point f and point e is greatly dissociated at an output angle of 35 °, which is observed as a dark line when visually observed at 35 ° force.

[0055] In the present invention, of the light in the light guide plate forming the second peak, the factor causing the dark line This is a dark line that reduces the disappearance of total reflection between the bottom surfaces of the grooves, and reduces the screen quality by arranging the grooves more than the pitch that reduces the light transmitted through the slope on the incident end face side of the grooves. Can be prevented.

[0056] Equation (2) is a process in which total reflection is performed on the bottom surface between the grooves forming the second peak, total reflection on the slope of the linear light source side of the groove, and emission from the output surface. This is a functional equation that determines the relationship between the maximum angle Φin of the light passing through the straight line a parallel to the Y-axis Φin and the average slope R of the concave stripes formed on the bottom surface of the light guide. . Once this maximum angle Φίη is determined, the smallest possible pitch Pbotom can be found from equation (3).

[0057] On the bottom surface of the light guide plate included in the surface light source element of the present invention, the pitch P, which is the distance between the centers of any two adjacent recesses, satisfies the following expressions (1) 'and (2)' Therefore, it is preferable because the dark line observed on the exit surface of the light guide plate can be eliminated with two diffusion sheets.

[0058] ΗνΛ η (Φίη) ≤ Ρ ≤ LXHvX0.3 (1) '

here

Φίη = (CR "+ CR ² + C R + C) + 2R— 90.0 ° (2),

3 2 1 0

C = 1.48X 10 ² , C = -8.07, C = 2.01X10— C = — 1.96X10— ³

0 1 2 3

[0059] Further, it is more preferable that the pitch P satisfies the following expressions (1) "and (2)" because dark lines observed on the exit surface of the light guide plate can be eliminated with one diffusion sheet.

ΗνΛ η (Φίη) ≤ Ρ ≤ LXHvX0.3 (1) "

here

Φίη = (CR ³ + CR ² + C R + C) + 2R-90.0 ° (2) "

3 2 1 0

C = 2.08 X 10 ² , C = — 1.30X10 ¹ , C = 3.32X10— C = —3.12X10— ³

0 1 2 3 Further, even when the cross-section of the groove formed on the bottom surface of the light guide plate is trapezoidal, dark lines can be eliminated by the same principle as the V-shape.

[0060] In the present invention, protrusions formed at a predetermined pitch are formed on the exit surface of the light guide plate. The ridges include trapezoidal ridges described below, and may be substantially the same or equivalent to the ridges used in the conventional surface light source element.

[0061] These ridges are formed such that the convex portions of the cross section extend in the negative direction. The cross-sectional shape of these ridges is a desired shape such as a triangle, wedge, other polygon, wave, or semi-elliptical. There may be.

[0062] In the light guide plate provided in the surface light source element of the present invention, if the protrusion provided on the exit surface is a protrusion having a trapezoidal cross section, the front luminance in the viewing direction is higher and the viewing angle characteristic is higher. It is more preferred and form in terms of widening.

For example, on the surface of the light guide plate 1 shown in FIG. 7, the one surface la has symbols A, B, C and

A section with a trapezoidal cross section with each vertex at D and a trapezoidal protrusion with a sign A ', B', C ', and D' with each vertex at two vertices are arranged apart from each other. Yes.

Note that the trapezoidal shape of the light guide plate provided in the surface light source element of the present invention is not limited to a trapezoidal shape in a strict sense as shown in the drawings. As will be apparent from the description below, if the upper and lower bases, which are planes having different heights parallel to the XY plane, are continuous across the slope connecting the chevron, for example, the upper base or the lower base The connecting portion of the slope may be curved. Such a trapezoidal shape having a curved connecting portion is preferable because it is relatively easy to mold and is not only advantageous for production but also hardly damages the connecting portion. In addition, at least part of the upper and lower bases may be inclined with respect to the XY plane. For example, the upper and / or lower bases are gently wavy with the X-axis direction as the longitudinal direction. In addition, the uniformity of light emission can be improved by having fine irregularities. The average of the slopes preferably has no angle with respect to the XY plane. In addition, it is desirable that the part where the inclination is 10 degrees or less accounts for 50% or more of the whole.

Yes

[0064] Further, since the plurality of upper and lower bases are in the same X-Y plane, the center of gravity of the light guide plate can be stabilized only by being able to guide light efficiently. Advantageous continuous production becomes easy.

Next, the trapezoidal function will be described with reference to FIG. The terms “upper base” and “lower base” are used, but this is for the purpose of explanation rather than the vertical direction. In the trapezoidal parallel opposite side, the short side is described as “upper base”, and the long side is described as “lower base”. First, in Fig. 7, the length of the straight line AD (width of the lower base of the ridge 2) is Wl, the length of the straight line BC (width of the upper base 2a of the ridge 2) is W2, and the length of the straight spring AD ' The height (width of the top 3a of the groove 3) is W3, the height of the protrusion 2 (or the depth of the groove 3) is H, and the angle between the straight line AD and the straight line AB (slope 2b) is a 1 The angle between the straight line AD and the straight line DC (inclined surface 2c) is a2, and the length of the straight line DD 'is the pitch. To do. The pitch P is equal to the sum of the width of the lower base of the ridge 2 (the length of the straight line AD) Wl and the width W3 of the upper base 3a of the concave 3 and the width of the upper base 2a of the ridge 2 (straight line). BC length) Equal to the sum of W2 and the width of the bottom of the groove 3 (length of straight line BC ').

[0066] On the exit surface of the light guide plate provided in the surface light source element of the present invention, the light guide incident from the incident end face is provided by making the cross section of the ridge 2 trapezoidal and providing the ridge 2 with an appropriate width W2. It plays the role of guiding light to the center of the light guide plate, while increasing the luminance in the front direction perpendicular to the emission surface in the luminance distribution emitted from the emission surface.

[0067] Further, on the exit surface of the light guide plate provided in the surface light source element of the present invention, the cross-sectional shape of the recess 3 is trapezoidal and a desired width W3 is provided in the recess 3, so that the same as W2 described above. While playing the role of guiding the light incident from the incident end surface along the Y-axis direction inside the light guide plate, the brightness in the front direction orthogonal to the exit surface is increased in the exit surface force and the emitted brightness distribution. Yes. If the width W2 is too narrow and the contribution of the inclined surfaces 2b and 2c becomes too large, it will be difficult to fully exhibit the effect of increasing the luminance in the vertical direction. Further, even if the width W3 is too narrow and the contribution of the inclined surfaces 2b and 2c becomes too large, it is difficult to sufficiently exert the effect of increasing the luminance in the vertical direction. On the other hand, if the width W2 and / or the width W3 is set too wide relative to the inclined surfaces 2b and 2c, the contribution of the inclined surfaces 2b and 2c becomes relatively small, and the luminance in the vertical direction is reduced. However, the viewing angle is narrowed, a periodic pattern of ridges is provided on the exit surface, the directional sheet is omitted as much as possible, and the viewing angle can be secured without reducing the brightness in the vertical direction. The problem cannot be met sufficiently.

[0068] On the exit surface of the light guide plate provided in the surface light source element of the present invention, the shape and size of the ridges 2 or 3 and the pitch P are the size of the light guide plate 1, the display performance and specifications of the surface light source elements, etc. It is determined in consideration of the relationship. As a result, the brightness of the light emitted from the exit surface of the light guide plate can be kept moderate and an appropriate viewing angle can be obtained.

[0069] The general height H of such ridges 2 (or ridges 3) is selected from the range of 0.001 mm to 0.1 mm, and a more preferable height H is 0.005 mm to 0.005 mm. 05mm, the most preferable height H is selected in the range of 0.01mm to 0.03mm. Further, the general inclination angle al and the inclination angle a2 are each selected from the range of 15 to 70 °, and the more preferable inclination angle al and the inclination angle a2 are respectively selected from the range of 15 ° to 60 °. . Emphasis on viewing angle characteristics 15 ° to 35 ° is selected as the best range, and 35 ° to 60 ° is selected as the most preferable range when the luminance characteristics are important. Also, the general bottom width W1 is within the range of 0.01 mm to 0.5 mm, more preferably within the range of 0.015 mm to 0.27 mm, and most preferably within the range of 0.051 mm to 0.18 mm. Selected. In addition, the width W2 of the upper base is selected from the range of 0.001 mm to 0.5 mm, and the more preferable width W2 is in the range of 0.001 mm to 0.1 mm, most preferably 0.005 mm to 0.05 mm. Is selected from the range. The general width W3 is selected from the range of 0.0001 mm to 0.5 mm, and the more preferable width W3 is in the range of 0.0001 mm to 0.3 mm, and most preferably the range of 0.001 mm to 0.15 mm. Selected from

[0070] Further, in a preferred embodiment of the exit surface of the light guide plate provided in the surface light source element of the present invention, the exit surface of the light guide plate 1 has a specific ratio in relation to the widths Wl, W2, and W3 and the pitch P. It is characterized by having a trapezoidal pattern that is formed to hold. That is, on the exit surface of the light guide plate 1 provided in the surface light source element of the present invention, the ratio of the width W3 of the upper base formed on the concave strip 3 to the width W2 of the upper base formed on the convex strip 2 W3 / W2 Is more preferably in the range of 0.01 to 20 0, more preferably in the range of 0 · 02 to; 100, and most preferably in the range of 0.;! To 10. The ratio of (P−W2−W3) to (W2 + W3) is preferably in the range of 0 · 04−400 0, more preferably (more preferably in the range of 0.2 to 200, most preferably (or 0. 3 to;

[0071] On the exit surface of the light guide plate provided in the surface light source element of the present invention, the ratio of W3 to W2 is kept within these ranges, thereby appropriately adjusting the luminance of light emitted from the exit surface of the light guide plate 1. And setting conditions for obtaining an appropriate viewing angle becomes easy. Here, if the ratio of W3 to W2 is in the range of 0.;! ~ 10, the luminance in the vertical direction can be improved and the directional sheet can be omitted.

[0072] Further, when (P−W2−W3) has a specific power of (P2−W2−W3) in the range of 0 · 3 to 150, it is possible to ensure viewing angle characteristics while suppressing a decrease in luminance in the vertical direction. Therefore, the directional sheet can be omitted. Such a trapezoidal pattern may have a mirror surface, or may be appropriately roughened to form a diffusion surface. By roughening the surface, glare on the surface of the liquid crystal display device can be suppressed. In some cases, rectangular It is possible to prevent the generation of dark line-like lines that occur when the corner portion of the light guide plate is viewed obliquely. The liquid crystal display device thus obtained has excellent surface quality. For such roughening, for example, the arithmetic average roughness Ra based on JIS B0601 is preferably in the range of 0.001 mm to 0.01 mm, more preferably 0.00015 mm to 0.005 mm. It is within the range, and particularly preferably within the range of 0.0002 mm to 0.002 mm. In addition, as shown in FIG. 9 (b), such roughening may be performed only on the upper base (zenith surface) 2a of the ridge 2 but as shown in FIG. 9 (d), the inclined surface 2b And the zenith surface 2a (full diffused surface). Further, as shown in FIG. 9 (c), it may be provided only on the side surface (inclined surface 2b). Further, this roughening may be present on the upper base (zenith surface) 3a of the groove 3. By roughening the surface, a diffusing surface is formed, and the light emitted thereby is expected to improve the surface quality in any case.

Next, an example of a surface light source element using such a light guide plate 1 will be described with reference to FIG. 1 and FIG.

These surface light source elements 10 include a light guide plate 1 which is a flat transparent structure formed of a transparent resin such as acrylic resin, a linear light source 4a arranged on one side of the light guide plate 1, and a light guide plate 1 And a reflection sheet 5 disposed on the lower surface of the substrate. On the upper surface of the light guide plate 1, an emission surface 6 for emitting light is formed, and a bottom surface 7 is formed to face the emission surface 6.

FIG. 1 is a perspective view showing an example of a surface light source element of the present invention. Here, in the surface light source element 10 of FIG. 1, a linear light source 4 a is disposed on one side surface of the light guide plate 1, and this side surface is an incident end surface 8. Further, both side faces intersecting with the incident end face 8 are reflection end faces 8b, and a face facing the incident end face 8 is a reflection end face 8a.

Further, the surface light source element of FIG. 8 is an example of the surface light source element of the present invention in which two linear light sources are provided on two opposite side surfaces of the light guide plate, and displays a large liquid crystal image display device. It is for making it happen. Figures 8 (a) and (b) are side views parallel to the X-Z plane, respectively, and a side view when viewed in the Y-axis direction, and from the side parallel to the Y-Z plane, toward the X-axis direction. It is a side view when observed.

[0076] A pair of linear light sources 4a are arranged in the reflector 4b on both sides of the emission surface 6 and the bottom surface 7, respectively. It is set up! The thick light guide plate 1 is used in order to secure a sufficient amount of light that enters the light guide plate 1 from the linear light source 4a. Thus, both side surfaces on which these linear light sources 4a are disposed are made incident end surfaces 8, and both side surfaces intersecting with the incident end surfaces 8 are made reflected end surfaces 8b. In the surface light source element of FIG. 8, a diffusion sheet 5a is disposed above the emission surface 6. By disposing a diffusion sheet on the light guide plate, the light emitted from the surface light source elements can be appropriately leveled and the screen quality can be improved. In addition, the front brightness can be further increased by selecting an appropriate diffusion sheet.

In any of the surface light source elements shown in FIGS. 1 and 8, the output surface 6 has a trapezoidal ridge 2 having a trapezoidal cross section and a trapezoidal concave in which the trapezoidal shape of the ridge 2 is upside down. Articles 3 and I are arranged alternately. Since these ridges 2 and 3 are substantially the same as the surface la described with reference to FIG. 7 described above, detailed description thereof is omitted. Thereby, a plurality of ridges and ridges having a trapezoidal cross section perpendicular to the incident end face 8 are arranged on the exit face 6. On the other hand, on the bottom surface 7, concave strips 9 having a cross-sectional force shape are arranged in parallel to the incident end surface 8. By gradually adjusting the pitch of the V-shaped concave strip 9, the light intensity distribution of the light emitted from the exit surface can be adjusted.

Next, the surface light source element 10 configured as described above will be described.

The light from the linear light source 4a enters the light guide plate 1 from the incident end face 8 of the light guide plate 1, and propagates in the vertical direction between the output surface 6 and the bottom surface 7 while repeating total reflection. A part of this light is guided toward the exit surface 6 by the V-shaped recess 9 formed on the bottom surface 7 and the reflection sheet 5, and the cross section formed on the exit surface 6 has a trapezoidal prism (convex shape). The light is condensed by the strip 2 and the concave strip 3) and is emitted within a desired viewing angle.

[0079] Thus, by forming a prism having a trapezoidal cross section on the exit surface 6, a reduction in luminance in the vertical direction can be suppressed and a viewing angle can be reduced as compared with the case of forming a V-groove prism on the exit surface 6. Expanding.

The trapezoidal prism described above is an example in which the zenith surface (upper base) 2a and the inclined surface 2b are mirror surfaces as shown in FIG. 9 (a). These surfaces are roughened. It may be. For example, as shown in FIG. 9 (c), when the inclined surface 2b of the trapezoidal prism (projection 2) is roughened, the viewing angle is larger than when the entire surface shown in FIG. 9 (a) is a mirror surface. As surface light source elements expand If the surface 10 has a glare as a child 10, the wrinkled line that occurs when the corner portion of the light guide plate is viewed obliquely is relaxed, and the screen quality can be improved.

Further, as shown in FIG. 9 (d), when the entire surface of the zenith surface 2a and the inclined surface 2b of the trapezoidal prism (projection 2) is roughened, the inclined surface 2b shown in FIG. 9 (c) is obtained. The surface brightness is slightly reduced compared with the case where only the surface is roughened, but if the surface shines as a surface light source element, the dark line is relaxed and the screen quality is further improved, and the viewing angle and the surface are improved. Suitable for surface light source elements where quality is important.

In addition, the image display device of the present invention is configured by disposing a transmissive display device in the front direction of the surface light source element, and has high brightness and high brightness uniformity. High-quality images can be displayed without degrading the quality. Here, the image display device of the present invention is a display module in which a surface light source element and a display element are combined, and a device having at least an image display function using the display module, such as a personal computer monitor or a television. including.

Example

Hereinafter, the effects of the present invention will be specifically described with reference to examples.

The stamper on the exit surface side (hereinafter referred to as stamper I) was a mirror stamper made of SUS. On the other hand, the bottom side stamper (hereinafter referred to as stamper Π), in which prism patterns with a height of 0.01 mm and apex angle of 100 ° are arranged at a predetermined interval, has a apex angle of 100 ° and a height of A 0.01 mm V-shaped groove was produced by cutting, and was directly electroplated from this cutting insert to form a nickel electroplating layer, and this master was peeled off.

These stamper I and stamper Π were used as transfer molds and incorporated in the mold fixing side cavity and mold movable side cavity of the injection molding machine, and a light guide plate having a fine structure for 17-inch display was obtained by injection molding. . The outer dimensions of the obtained light guide plate were horizontal X vertical X thickness 348 X 281 X 6 mm, and the distance L from the incident end face to P was 140 mm. The light guide plate emits light

MIN

The surface is a mirror surface, and a V-shaped groove is provided on the bottom surface. The groove has a height Hv of 0.01 mm and the bottom surface of the slope parallel to the X axis on the incident end surface side of the groove corresponding to the average base angle. The average slope R with respect to is 40 ° and the pitch is in the range satisfying the formula (1) (0.0337mm≤P≤0.422mm) It was changed so that it gradually decreased gradually from 0.18mm on the polar tube side to 0.06mm in the center.

[0084] The lateral end face of the light guide plate is defined as an incident end face, the incident end face is arranged in parallel to the X axis, and the tube surface brightness is 39,000 cd / m ² along the two incident end faces facing each other. Two pairs of cold cathode tubes with a diameter of 2.4 mm were placed facing each other, and a reflector coated with foamed PET on the inner surface was placed behind the light source. Then, a reflection sheet 5 (E6 SU manufactured by Toray Industries, Inc. was disposed on the bottom surface 7 and the reflection end surface 8b to form the backlight device shown in FIG. 10. The backlight device shown in FIG. When the exit surface of the surface light source element was observed, it was found that dark lines were not generated when viewed obliquely with respect to the front direction.

[0085] Further, two diffusion sheets (product name: DX2) 5a manufactured by Judgen Co., Ltd. are disposed on the light exit surface of the light guide plate in the backlight device shown in FIG. 10, and the backlight device shown in FIG. Formed.

[0086] The luminance performance of the backlight device thus formed was measured. This surface luminance measurement was performed on the entire emission surface using a luminance meter (TOPCON BM-7) manufactured by Topcon Co., Ltd. at a distance of 50 cm from the sample surface. In addition, at the center point of the light exit surface of the light guide plate, the luminance angle distribution (hereinafter referred to as the horizontal direction) by tilting the luminance meter sequentially from the vertical direction of the exit surface to both sides with respect to the plane parallel to the X axis and perpendicular to the light guide plate. Angular luminance distribution) was measured. Similarly, at the central point of the light exit surface of the light guide plate, the luminance angle distribution (hereinafter referred to as the vertical direction) is tilted sequentially from the vertical direction of the light exit surface to both sides with respect to the surface perpendicular to the X axis and perpendicular to the light guide plate. Angular luminance distribution) was measured. From the horizontal angular luminance distribution and the vertical angular luminance distribution, the horizontal half-value angle and the vertical half-value angle, which are indicators of viewing angle characteristics, were obtained. As a result, the maximum luminance was 1457 cd / m ² , the horizontal half-value angle was 39.8 °, and the vertical half-value angle was 42.4 °.

A stamper I was used as the stamper on the exit surface side in the same manner as in Example 1. On the other hand, a stamper having a trapezoidal cross section on the bottom side (hereinafter referred to as stamper III) was produced by the following method. First, a negative photoresist (CA3000) manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied to clean glass, heated on a hot plate at 110 ° C for 2 minutes, and then cooled to room temperature. Between the glass substrate and the predetermined A photomask with slits was put in close contact with each other and rotated at a constant speed from 35 ° to + 35 °, during which UV light was irradiated at 1400 mJ. After removing the photomask, the substrate was imaged. In accordance with a conventional method, a nickel conductive film was formed on the surface of the obtained master, and nickel was used as a metal for the nickel to form a nickel conductive layer. In addition, the master was peeled from the nickel conductive film, and a stamper with a trapezoidal pattern with a tilt angle of 40 ° and a flat part with a height of 0.01 mm and a width of about 0.0 lmm at the top part. Make III

; ^^

[0088] A light guide plate having a fine structure for a 17-inch display was obtained in the same manner as in Example 1 using these stano I and stamper III as transfer molds. The outer dimensions of the light guide plate were horizontal X vertical X thickness 348 X 281 X 6 mm, and the distance L from the incident end face to P was 140 mm.

MIN

The resulting light guide plate has a mirror-like exit surface, and a trapezoidal groove with a trapezoidal cross section on the bottom. The height Hv of the groove is 0.01 mm, the upper base is 0.01 mm, average The average slope R with respect to the bottom of the slope parallel to the X-axis on the incident end face side of the groove corresponding to the base angle is 40 °. The pitch was varied so that it gradually decreased gradually from the cold cathode tube side of 0.18 mm to the center of 0.06 mm within the range satisfying equation (1) (0.0337 mm ≤ P ≤ 0.422 mm).

A backlight device shown in FIG. 10 was formed in the same manner as in Example 1 by incorporating the light guide plate. When the exit surface of the surface light source element was observed with the backlight device shown in Fig. 10, it was found that the dark line was not generated when viewed obliquely with respect to the normal direction.

[0090] Further, two diffusion sheets (product name: DX2) 5a made by Gidden Co., Ltd. are arranged on the light exit surface of the light guide plate to form the backlight device shown in FIG. 11, and the luminance performance is measured. As a result, the maximum luminance was 1105 cd / m ² , the horizontal half-value angle was 40.1 °, and the vertical half-value angle was 38.3 °.

A negative type photoresist (CA3000) manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied to clean glass, heated on a hot plate at 110 ° C for 2 minutes, and then cooled to room temperature. The glass substrate and a photomask with slits at predetermined intervals were brought into close contact with each other and rotated at a constant speed from 35 ° to + 35 °, during which UV light was irradiated at 1400 mJ. After removing the photomask, the substrate was developed. In accordance with a conventional method, a nickel conductive film is formed on the surface of the obtained master disk, and nickel is used as a metal for the electrode to form a nickel conductive layer. did. Further, the master is peeled off from the nickel conductive film, and the height is 0.01 mm and the top part has a flat part with a width of about 0.01 mm, and a trapezoidal pattern with an inclination angle of 55 ° is molded. A stamper (hereinafter referred to as stamper IV) was produced.

[0092] These stano IV and the same stamper II as in Example 1 were used as transfer molds and incorporated into the mold fixing side cavity and mold movable side cavity of the injection molding machine, and the microstructure for 17-inch display was achieved by injection molding. A light guide plate with was obtained. The outer dimensions of the light guide plate were horizontal X vertical X thickness 3 48 X 281 X 6 mm, and the distance L from the incident end face to P was 140 mm.

MIN

[0093] The obtained light guide plate has an exit surface in which convex stripes having a trapezoidal cross section are arranged apart from each other and a bottom surface in which concave stripes having a cross sectional shape are arranged at a predetermined pitch And. The trapezoidal convex shape of this exit surface has a height H of 0.01 mm, a zenith width W2 of 0.01 mm, and a bottom surface width W1 of 0.024 mm. The depth Hv is 0.01 mm, and the average slope R with respect to the bottom surface of the slope parallel to the X axis on the incident end face side of the groove corresponding to the average base angle is 40 °. The pitch of the bottom ridges produced this time was changed so that it gradually decreased gradually from 0.18 mm on the cold cathode tube side to 0.06 mm in the center within the range satisfying the formula (1) as in Example 1.

The backlight device shown in FIG. 10 was formed in the same manner as in Example 1 by incorporating the light guide plate. When the exit surface of the surface light source element was observed, no dark line was generated when the oblique force was seen in the front direction.

[0095] Further, two diffusion sheets (product name: DX2) 5a made by Gidden Co., Ltd. are arranged on the light exit surface of the light guide plate to form the backlight device shown in FIG. As a result, the maximum brightness was 51 77 cd / m ² , the horizontal half-value angle was 42.3 °, and the vertical half-value angle was 42.0 °.

A light guide plate was produced in the same manner as in Example 1, using the stamper IV as the stamper on the exit surface side and the stamper III as the stamper on the bottom surface side. The outer dimensions of the light guide plate were horizontal X vertical X thickness force 48 X 281 X 6 mm, and the distance L from the incident end face to P was 140 mm.

MIN

[0097] The obtained light guide plate has a light emitting plate in which convex ridges having a trapezoidal cross section are spaced apart and a bottom surface in which concaves having a trapezoidal cross sectional shape are arranged at a predetermined pitch. And. The trapezoidal convex shape of this exit surface has a height H of 0.01 mm, a zenith width W2 of 0.01 mm, and a bottom. The surface width Wl is 0.024 mm, and the height Hv of the concave trapezoidal groove is 0.01 mm. The average slope with respect to the bottom of the slope parallel to the X axis on the incident end face side of the concave corresponding to the average bottom angle The degree R is 40 °. The pitch of the bottom groove produced this time was changed so that it gradually decreased gradually from the cold cathode tube side 0.18 mm to the center 0.06 mm within the range satisfying formula (1) (0.0337 mm ≤ P ≤ 422 mm). It was.

[0098] The backlight device shown in FIG. 10 was formed in the same manner as in Example 1 by incorporating the light guide plate, and when the exit surface of the surface light source element was observed, it was observed when viewed obliquely with respect to the front direction. No line was generated.

[0099] Further, two diffusion sheets (product name: DX2) 5a manufactured by Gidden Co., Ltd. were disposed on the light exit surface of the light guide plate to form the backlight device shown in FIG. 11, and the luminance performance was measured. The maximum brightness was 4658cd / m ² , the horizontal half-value angle was 43.5 °, and the vertical half-value angle was 41.3 °.

[0100] <Comparative Example 1>

In this comparative example, the pitch of the V-shaped ridges on the bottom surface of the light guide plate used in Example 3 is changed from 0.027 mm to 0.18 mm. In the same manner as in Example 1, a V-shaped concave strip having a vertex angle of 100 ° and a height of 0.01 mm was manufactured by cutting with a diamond tool in a direct mold insert, and the nickel was directly fed from this cutting insert. An electroplating layer was formed. The master disc was peeled off, and a stamper V on the bottom side was formed by arranging prism patterns with a height of 0.01 mm and an apex angle of 100 ° at predetermined intervals.

[0101] The stamper IV and stamper V, which have a trapezoidal cross-section on the exit surface side used in Example 3, are incorporated into the mold fixed side cavity and mold movable side cavity of the injection molding machine as transfer molds. The light guide plate 5 having a fine structure for a 17-inch display was obtained by an injection molding method. The outer dimensions of the light guide plate are horizontal X vertical X thickness 348 X 28 I X 6mm, from the incident end face to P

MIN

The distance L was 40mm.

[0102] The obtained light guide plate has a light emitting plate having a trapezoidal section in cross section and a bottom surface in which convex sections having a cross section shape are arranged at a predetermined pitch. And. The trapezoidal convex shape of this exit surface has a height H of 0.01 mm, a zenith width W2 of 0.01 mm, and a bottom surface width W1 of 0.024 mm. The height Hv is 0.01 mm, and the average slope R with respect to the bottom of the slope parallel to the X axis on the incident end side of the groove corresponding to the average base angle is 40 °. The pitch of the bottom groove produced this time was gradually reduced from 0.18 mm on the cold cathode tube side to 0.027 mm in the center.

[0103] When the backlight device shown in FIG. 10 was formed in the same manner as in Example 1 and the emission surface of the surface light source element was observed, dark lines were generated when an oblique force was also observed in the front direction. For this reason, two diffusion sheets (product name: DX2) 5a made by Judgen Co., Ltd. are arranged on the light guide plate, and reflection sheets 5 (E6SL made by Toray Industries, Inc.) are arranged on the bottom and reflection end surfaces. The backlight device shown in Fig. 11 was formed. When the luminance performance of the backlight device thus formed was measured, it had a maximum luminance of 5232 cd / m ² , a horizontal half-value angle of 42.1 °, and a vertical half-value angle of 41.8 °. The dark line of the book was generated in parallel with the cold cathode tube. In order to eliminate the dark line, two diffusion sheets (product name: DX2) were installed to eliminate the dark line, but the luminance performance was lowered and the viewing angle characteristics were narrowed.

[Comparative Example 2]

In this comparative example, the pitch of the V-shaped concave stripes located on the bottom surface of the light guide plate used in Example 1 is set to 0.027 mm force and 0.18 mm.

Stamper I is used as the stamper on the exit surface side, and stamper V is used as the transfer die on the bottom side stamper. A light guide plate with structure was obtained. The outer dimensions of the light guide plate are horizontal and vertical thickness 48 281 6111111, and the distance L from the incident end face to P is 140 mm.

MIN

It was.

[0105] In the obtained light guide plate, the exit surface is a mirror surface, and the bottom surface is provided with concave stripes having a V-shaped cross section, and the height Hv of the concave stripes is 0.01 mm, the average base angle The average slope R with respect to the bottom of the slope parallel to the X axis on the incident end face side of the concave stripe is 40 °. The pitch of the bottom grooves produced this time was gradually reduced from 0.18 mm on the cold cathode tube side to 0.027 mm in the center.

[0106] When the backlight device shown in FIG. 10 was formed in the same manner as in Example 1 and the emission surface of the surface light source element was observed, dark lines were generated when an oblique force was also observed in the front direction. For this reason, two diffusion sheets (product name: DX2) 5a made by Judgen Co., Ltd. are arranged on the light guide plate, and reflection sheets 5 (E6SL made by Toray Industries, Inc.) are arranged on the bottom and reflection end surfaces. Shown in Figure 11 A backlight device was formed. The luminance performance of the backlight device thus formed was measured. The maximum luminance was 1596 cd / m ² , the horizontal half-value angle was 37.5 °, and the vertical half-value angle was 38.5 °. The dark line of the book was generated in parallel with the cold cathode tube. In order to eliminate the dark line, two diffusion sheets (product name: DX2) were installed to eliminate the dark line. The luminance performance was lowered and the viewing angle characteristics were narrowed.

[0107] The above results are summarized in Table 1.

[table 1]

Industrial applicability

[0108] If the light guide plate provided in the surface light source element of the present invention is used, dark lines that lower the screen quality can be eliminated and the brightness can be increased. Therefore, the light source plate can be suitably used for a surface light source element. In addition, since the surface light source element of the present invention is of an edge light type, it is not limited to a monitor device equipped with a liquid crystal backlight device, but can be applied to various types of thin image display devices such as notebook computers, lighting announcements, traffic signs, etc. Is expected to be applied.

Claims

The scope of the claims

An edge light type surface light source element in which at least one linear light source is arranged on the side surface of the light guide plate,

The light guide plate has an exit surface, a bottom surface facing the exit surface, and an incident end surface on which light emitted from a linear light source provided on at least one side surface is incident,

Reflecting means for reflecting light is provided on the bottom side of the light guide plate,

The linear light source is arranged parallel to the X axis,

MIN M

And the ratio P / P is 1.5 or more,

AX MAX MIN

A surface light source element characterized in that a pitch P, which is a distance between the centers of any two adjacent concave stripes, satisfies the following formula (1).

ΗνΛ η (Φ ίη) ≤ Ρ ≤ L X HvX 0.3 (1)

here

Φ ίη = (CR ³ + CR ² + C R + C) + 2R— 90.0 ° (2)

3 2 1 0

C = — 1.25 X 10 ² , C = 1.31 X 10 ¹ , C = —3.30 X 10— 丄, C = 2.43 X 10— ³

0 1 2 3

P: Distance between the centers of any two adjacent grooves (pitch) (unit: mm)

Hv: Height of the groove (unit: mm)

MIN

c to c: Coefficient [2] The linear light source is disposed on each of the two incident end faces facing each other of the light guide plate, and the plurality of concave stripes are parallel to the X axis with respect to the two incident end faces. The surface light source element according to claim 1, comprising:

[3] The surface light source element according to [1] or [2], wherein a cross-section of the groove formed on the bottom surface of the light guide plate is V-shaped.

[4] The surface light source element according to claim 1 or 2, wherein a cross-section of the groove formed on the bottom surface of the light guide plate is trapezoidal.

[5] The surface light source element according to [1] or [2], wherein a pattern composed of a plurality of ridges parallel to the Y-axis is formed on the exit surface of the light guide plate.

6. The surface light source element according to claim 5, wherein a cross-section of the ridge formed on the light exit surface of the light guide plate is trapezoidal.

[7] An image display device comprising a transmissive display element on an emission surface side of the surface light source element according to [1].