JP3316441B2 - Light guide plate, surface light source using the light guide plate, liquid crystal display device, and method of manufacturing light guide plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light guide plate, a surface light source using the light guide plate, a liquid crystal display device, and a method for manufacturing the light guide plate. A light guide plate having an external light intake portion formed therein, a surface light source for a backlight of a liquid crystal display device using the light guide plate, a backlight type liquid crystal display device such as a liquid crystal monitor for projecting a subject with a digital still camera or a video camera, and The present invention relates to a method for manufacturing the light guide plate.

[0002]

2. Description of the Related Art As a surface light source for a backlight of a liquid crystal display device, a side light type using a light-transmitting flat plate as a light guide plate is known. In such a surface light source, light from a light source such as a fluorescent lamp is incident from one of the side end surfaces of a light guide plate made of a transparent parallel flat plate or a wedge-shaped flat cross section, and the total internal reflection inside the translucent flat plate is used. Light is propagated throughout the light guide plate, and a part of the propagated light is made into a diffuse reflection light of less than a critical angle by a light scattering reflector on the back surface of the light guide plate, and diffuse light is emitted from the surface of the light guide plate (actually open). 55-162201).

Further, a lens sheet having a triangular prism type lenticular lens protrusion on one surface and a smooth surface on the other surface is superposed on the light guide plate surface of the above-mentioned surface light source with the protrusion surface facing upward. , Utilizing the light focusing action of the lens
A device capable of uniformly and isotropically diffusing the diffused radiation within a desired angle range is also known (Japanese Utility Model Application Laid-Open No. 4-1).
07201).

When this lens sheet is used in combination with a matte transparent diffuser (matte transparent sheet), the lens sheet uses only a matte transparent diffuser (US Pat. No. 4,729,067).
), The light energy of the light source can be more preferentially distributed within a desired limited angle range, and diffused light having high uniform isotropy can be obtained within that angle range. More recently, as a measure against the high luminance of the backlight used in the liquid crystal display device, there is a tendency to adopt a configuration in which two lenticular lens sheets are stacked at right angles as shown in FIG. 1 (Monthly Display, May 1996, p. 35). ~ P39).

[0005] Further, a surface light source for a backlight in which an external light intake portion is provided on a side end surface of a light guide plate in order to use external light such as sunlight or indoor light as an auxiliary light source is also known. The shape of the entrance portion is arc-shaped in cross section to constitute one cylindrical lens (JP-A-5-11249).

[0006]

However, the conventional surface light source of the liquid crystal display device not only has a problem that the visual characteristics are relatively narrow, but also uses two lenticular lens sheets. In addition to the cost, it is necessary to attach two lenticular lens sheets at right angles to each other and attach them, so that there is a problem in that a large manufacturing cost is generated and the backlight itself becomes very expensive. In addition, since the power consumption of the liquid crystal display device itself, which projects a subject with a digital still camera or video camera, is extremely large, even if the power consumption of other circuit systems is suppressed, the overall power consumption of the camera device can be effectively reduced. As a result, there is a problem that the use time of the camera device cannot be extended.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the parts cost and the manufacturing cost can be reduced by reducing the number of lenticular lens sheets used to one or unnecessary. Provided are a liquid crystal display device and a backlight surface light source capable of reducing the power consumption of the main light source and eliminating the need for the main light source, a light guide plate provided with the surface light source, and a method of manufacturing the light guide plate. The purpose is to:

[0008]

According to a first aspect of the present invention, there is provided a light guide plate which is formed integrally with a resin to achieve the above object, and is provided with an external light take-in for taking in external light. An entrance and a light exit surface that emits external light taken from the external light intake unit, the external light intake unit protrudes from the light exit surface, and the light exit surface has a plurality of light exit surfaces. A first lens unit made of a concave or convex lenticular unit lens is formed, and the plurality of lenticular unit lenses of the first lens unit are arranged such that their ridge directions are substantially parallel to each other, and the external light collecting unit has a ridge line direction. It is characterized by being substantially orthogonal to the longitudinal direction of the entrance.

According to a second aspect of the present invention, in the light guide plate according to the first aspect, an angle of a top of the plurality of lenticular unit lenses of the first lens portion is 125 degrees to 165 degrees. Features. According to a third aspect of the present invention, in the light guide plate according to the first aspect, an angle of a top of the plurality of lenticular unit lenses of the first lens unit is about 150 degrees.

The light guide plate of the present invention according to claim 4 is the light guide plate according to any one of claims 1 to 3,
The light reflecting surface facing the light emitting surface includes a second lens unit including a plurality of concave or convex lenticular unit lenses molded of the same resin as the light guide plate, and a plurality of the second lens units. The lenticular unit lenses are characterized in that their ridge directions are arranged substantially parallel to each other, and are substantially perpendicular to the ridge directions of the plurality of lenticular unit lenses of the first lens unit.

According to a fifth aspect of the present invention, in the light guide plate according to the fourth aspect, an angle of a top of the plurality of lenticular unit lenses of the second lens portion is 125 degrees to 165 degrees. Features. According to a sixth aspect of the present invention, in the light guide plate according to the fourth aspect, an angle of a top of the plurality of lenticular unit lenses of the second lens unit is about 150 degrees.

According to a seventh aspect of the present invention, there is provided a surface light source according to any one of the first to sixth aspects, an external light intake portion of the light guide plate, the light exit surface and the light reflection surface. And a light source attached to at least one surface other than the light source. According to an eighth aspect of the present invention, there is provided a liquid crystal display device, comprising: the light guide plate according to any one of the first to sixth aspects or the surface light source according to the seventh aspect; and a light emitting surface of the light guide plate. And a liquid crystal panel mounted close to the liquid crystal panel.

According to a ninth aspect of the present invention, there is provided a method of manufacturing a light guide plate according to any one of the first to sixth aspects, wherein the light guide plate is molded with a mold. It is characterized by including.

[0014]

Embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 7A and 7B are perspective views showing a light guide plate, and the following terms are defined using this drawing.
In FIG. 7A, a lenticular unit lens is a prism having a triangular prism whose base is a triangle formed by a vertex ABC, and in FIG. 7B, a vertex ABDE
A pentagonal prism having a pentagon formed by C as a bottom surface. However, the lenticular unit lens 1 shown here
f is merely an example and is not limited to these, and may be a cylinder, an ellipse, or a polygon. Also, in this figure, the lenticular unit lens 1f shows only a convex shape, but may have a concave shape (not shown).

The prism portion of the triangular prism of the lenticular unit lens corresponds to the vertex AB in both FIGS. 7A and 7B.
A triangular prism having a triangular bottom formed by C as a bottom surface. The top of the triangular prism is the vertex A in both FIGS. 7A and 7B.

The angle at the top of the prism portion of the triangular prism refers to the angle formed by the point BAC in both FIGS. 7A and 7B. FIG. 8 is a schematic diagram showing a cross-sectional shape of a prism portion of a triangular prism. The prism portion of the triangular prism is desirably an isosceles triangle shape as shown in FIG. 8A. For example, as shown in FIG. Even if the top A is smoothly curved as shown in FIG. 8 (C), the performance of the light guide plate is hardly affected. Therefore, all prisms having these shapes are included in the prism portion of the triangular prism of the present invention.

FIG. 2 is a perspective view showing a light guide plate according to the present invention. Reference numeral 1 denotes a light guide plate. At the same time when the light guide plate 1 is manufactured by resin molding using a mold, an external light intake portion 1a is formed at one upper end of the light guide plate 1, and a plurality of lenticular unit lenses 1f are formed. Is formed. Lenticular unit lens 1 of first lens unit 1e
f denotes prisms of triangular prisms, their ridge lines are substantially parallel to each other, and are arranged so as to be substantially perpendicular to the longitudinal direction of the external light intake 1a. In particular, the apex angle of the triangular prism is manufactured so as to be in a range of 125 degrees to 165 degrees based on a calculation result described later. In addition, if the apex angle of the triangular prism is in the range of 125 to 165 degrees, even if the size, pitch, height, and deviation of the apex angle of the triangular prism are varied, the performance of the light guide plate is affected. Do not give. In particular, as shown in FIG. 9, even when the pitch of the prism is changed in the range of 10 μm to 1000 μm,
It can be seen that the luminance distribution characteristics do not change significantly.

The external light receiving section 1a receives external light such as sunlight or room light as main light. This external light intake section 1a
Project from the first lens portion 1e in the upward direction in the figure, and as a result, the surface area of the external light intake surface is larger than that of the conventional light guide plate. The shape of the external light intake 1a is
This is a cylindrical lens having a substantially fan-shaped cross section and an arc-shaped tip, and the lens effect efficiently takes in external light not only directly above but also immediately beside or obliquely from above and below. However,
The external light intake portion 1a is not limited to a cylindrical lens having a fan shape, and may be, for example, a flat shape having no lens.

Reference numeral 1c denotes a light incident surface. As will be described below, light emitted from a light source (not shown) disposed substantially parallel to the light incident surface 1c enters. However, it is also possible to arrange a light source on one or both of the two side surfaces 1b to be a light incident surface. 1d is a light reflecting surface, in order to prevent light from leaking and to increase reflection efficiency, a plurality of cones having a substantially conical concave shape are formed simultaneously with resin molding, or after dot printing is performed after resin molding. A reflector such as aluminum is attached (not shown).

With the above-described light guide plate, the light incident from the external light take-in portion 1a and the light incident surface 1c from the first lens portion 1e is transmitted to the light reflection surface 1d and the two side surfaces 1 of the light guide plate 1.
b, most of the incident light is finally
e, the light is emitted as synthesized light having uniform directivity.
In addition, a leakage prevention member such as a white tape is attached to the side surface 1b in order to prevent light leakage.

The material of the light guide plate 1 is selected from light-transmissive materials, and usually acrylic or polycarbonate resin is used. The shape of the light guide plate is a parallel flat plate or a flat wedge-shaped flat plate, and the thickness thereof is generally about 1 to 10 mm. Other translucent materials include acrylate or methacrylate homo- or copolymers such as polymethyl methacrylate and polymethyl acrylate, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, and the like. Thermoplastic resins such as polystyrene and polymethylpentene, or acrylates such as polyfunctional urethane acrylates and polyester acrylates cross-linked by ultraviolet rays or electron beams, transparent resins such as unsaturated polyesters, transparent glass, transparent ceramics, etc. are used. Can be

Next, the operation of the light guide plate according to the present invention will be described with reference to FIG. From the outside light taking-in portion 1a of the light guide plate 1, sunlight outside the room and outside light from a fluorescent lamp or the like efficiently enter inside the room. When the light source is turned on, the light from the light source incident from the light incident surface 1c and the external light introduced from the external light intake unit 1a are reflected by the light reflecting surface 1d and the two side surfaces 1b of the light guide plate 1. Then, the diffuse radiation light guided toward the first lens portion 1e having an action of converging light is emitted from the first lens portion 1e as a combined light having a uniform directivity within a desired angle range. . Therefore, when the liquid crystal display device including the light guide plate according to the present invention is used for a liquid crystal monitor or the like for projecting a subject with a digital still camera or a video camera, it is necessary to provide sufficient illumination so that the light source does not need to be turned on. As a result, it is possible to reduce the power consumption of various camera devices themselves.

FIG. 3 is a graph showing the luminance distribution characteristics of the light guide plate according to the present invention. The horizontal axis represents the length of the light guide plate by 100.
The position of the light guide plate from the lamp is expressed as a percentage, and the position of the value 0 is the end surface position of the light guide plate closest to the lamp, while the position of the value 100 is the end surface of the light guide plate farthest from the lamp. Position. The vertical axis does not show a unit, but is a luminance, and a larger value means a brighter.

FIG. 3 is a graph showing the luminance distribution characteristics obtained by analyzing the luminance distribution characteristics of the light guide plate using CODEV, which is an optical design evaluation software developed by ORA in the United States. The wavelength of the light to be emitted is 600 nm, the refractive index of PMMA is 1.49 as a material of the light guide plate, and the apex angles of the triangular prism are 90 °, 120 °, 135 °, 150 °, 16
The simulation results of the luminance distribution characteristics when the angle is changed to 5 ° and flat (that is, without a triangular prism) are shown.

As can be clearly seen from the figure, the apex angle of the lens sheet used with the conventional light guide plate is 9
The luminance distribution characteristics from 0 ° to 120 ° are not only inferior to those which are flat, but also 135 °.
The luminance distribution characteristics from to 165 ° are greatly improved as compared with the conventional luminance distribution characteristics from 90 ° to 120 °. Further, the characteristic improvement from 135 ° to 165 ° is remarkable, and it can be easily understood that a peak effect appears in the luminance distribution characteristic especially around 150 °. However, even if the wavelength of light or the refractive index of the material of the light guide plate is slightly changed, there is no significant effect on the luminance distribution characteristics found here.

FIG. 4 is a graph showing viewing angle characteristics.
The horizontal axis indicates the viewing angle with respect to the light guide plate, and the value 0
(Not shown) is the direction perpendicular to the light guide plate, and the value -9.
0 means a direction horizontal to the light guide plate. The vertical axis does not show a unit, but is a luminance, and a larger value means a brighter.

The graph showing the viewing angle characteristics in FIG. 4 is obtained by analyzing the viewing angle characteristics of the light guide plate using CODEV in the same manner as described above. As the material of the light guide plate, a typical PMMA refractive index of 1.49 was used, and the apex angles of the triangular prism were 90 °, 120 °, 125 °, 135 °, and 1 °.
10 shows simulation results of luminance distribution characteristics when the angle is changed to 50 °, 165 ° and flat (that is, without a triangular prism).

As can be clearly seen from the figure, the apex angle of the lens sheet used with the conventional light guide plate is 9
Comparing the viewing angle characteristics of 0 ° and the viewing angle characteristics of 120 °, the result of 120 ° is much worse than that of 90 °, while the viewing angle characteristics from 125 ° to 165 ° are It can be easily understood that the viewing angle characteristic is much improved as compared with the conventional 90 ° viewing angle characteristic, and a peak effect appears.

The applicant of the present application has departed from the conventional concept of 90 ° to 120 °, which is the range of the apex angle of the conventional lens sheet, and has independently performed a basic optical design simulation of the light guide plate. The present inventors have found that the temperature is greatly improved in the range of 125 ° to 165 °, and propose a completely new light guide plate based on the results. FIG.
1 is a perspective view showing a light guide plate according to the present invention. However, the same reference numerals are given to the components already described, and the description is omitted.

The light guide plate 1 is manufactured by resin molding using a metal mold, and at the same time, a first lens portion 1e comprising a plurality of lenticular unit lenses 1f formed of the same resin as the light guide plate 1 is used. And a second lens portion 1g. Lenticular unit lens 1f of second lens portion 1g
Is a triangular prism similar to the first lens unit 1e, and their ridge lines are substantially parallel to each other, and are substantially parallel to the longitudinal direction of the external light intake unit 1a (that is, the first lens unit 1e).
Of the lenticular unit lens 1f).
The triangular prisms are manufactured so that the apex angle is in the range of 125 degrees to 165 degrees. Also, the vertex angle of the triangular prism is from 125 degrees to 16 degrees.
If the angle is within 5 degrees, the performance of the light guide plate will not be affected even if the size, pitch, height, apex angle of the triangular prism fluctuates or varies.

The lower surface of the second lens portion 1g is subjected to a reflection surface treatment by aluminum vapor deposition or the like (not shown) so as to prevent light from transmitting therethrough. Next, the operation of the light guide plate according to the present invention will be described with reference to FIG. External light intake 1 of light guide plate 1
From a, sunlight efficiently enters outside the room, and outside light from a fluorescent lamp or the like efficiently enters the room. When the light source is turned on, the light from the light source incident from the light incident surface 1c and the external light introduced from the external light intake unit 1a receive the lower surface of the second lens unit 1g and the two side surfaces of the light guide plate 1. 1b
Reflected by At this time, the second lens portion 1g has a function of making the light uniform within the light guide plate 1, and guides the diffused light toward the first lens portion 1e.

The diffuse radiation light guided toward the first lens portion 1e, which has the function of converging light by the second lens portion 1g, has uniform directivity within a desired angle range from the first lens portion 1e. Are emitted as combined light. Therefore, when the liquid crystal display device including the light guide plate according to the present invention is used for a liquid crystal monitor or the like for projecting a subject with a digital still camera or a video camera, it is necessary to provide sufficient illumination so that the light source does not need to be turned on. As a result, it is possible to reduce the power consumption of various camera devices themselves.

FIG. 6 is a schematic diagram showing a surface light source according to the present invention. 2 is a surface light source, and the light guide plate 1 according to the present invention,
It comprises a light source 3 such as a fluorescent tube and various control circuits (not shown). The control circuit also includes, for example, a circuit that detects the total amount of light emitted from the light emission surface of the light guide plate 1 and adjusts and supplies power to the light source 3 so that the amount of emitted light is optimized.

Light emitted from the light source 3 is reflected by the reflector 4 and enters the inside of the light guide plate 1 from the light incident surface 1c of the light guide plate 1 and external light such as natural light enters from the external light intake portion 1a. Reflector 5 attached to the lower part of 1d or the second
The light is repeatedly reflected and reflected by the lens portion 1g and the side end surface 1b,
The light is emitted from the first lens portion 1 e of the light guide plate 1 to the diffusion plate 6. Further, the light incident on the diffusion plate 6 is uniformly and isotropically diffused within a desired angle range by the diffusion plate 6 and the lens sheet 7 and is emitted from the lens sheet 7. However, depending on the application, a fluorescent tube, a control circuit (not shown), or the like may be removed from the main surface light source 2 to provide a surface light source of a type that takes in only external light, or the diffusion plate 6 and the lens sheet 7 may be removed. It is also possible.

FIG. 10 is a schematic diagram showing a liquid crystal display device provided with the surface light source according to the present invention. In the liquid crystal display device of FIG. 10A, the external light intake portion protrudes from the display surface of the liquid crystal panel 9 in the light emission direction, while in the liquid crystal display device of FIG. This indicates that it does not protrude from the display surface of the liquid crystal panel 9 in the light emission direction. These two types of liquid crystal display devices are both excellent in the effect of taking in external light, but the liquid crystal display device of FIG. 10B does not protrude from the display surface of the liquid crystal panel 9 because the external light taking-in portion does not protrude. Not only can the external light intake unit itself be prevented from being damaged or the user being injured, but also the degree of freedom in design is not impaired.

Reference numeral 8 denotes a liquid crystal display, and a liquid crystal panel 9
And the surface light source 2 according to the present invention. Light that is uniformly and isotropically diffused and emitted from the surface light source 2 described above is guided to the liquid crystal panel 9. However, a liquid crystal display device that removes the light source 3 from the surface light source 2 and uses only external light from the light guide plate 1 may be used. Further, in the method for manufacturing a light guide plate according to the present invention, a mold in which the fine pattern of the first lens portion 1e is processed or a mold in which the fine patterns of the first lens portion 1e and the second lens portion 1g are processed are used. And forming a plurality of lenticular unit lenses formed of the same resin as the light guide plate at the same time as the light guide plate is formed.

[0037]

As described above, according to the method of manufacturing a light guide plate according to the present invention, the light guide plate is molded with a mold, and at the same time, the external light intake portion and the conventional lenticular lens sheet are not required. Since the first lens portion including a plurality of lenticular unit lenses is formed on the light guide plate, it is possible to greatly reduce the manufacturing cost.

According to the light guide plate of the present invention, since the first lens portion composed of a plurality of lenticular unit lenses and the external light taking-in portion are already formed, the number of lenticular lens sheets required conventionally is reduced. Or, it is unnecessary, and as a result, the manufacturing cost can be greatly reduced. Further, it becomes possible to efficiently take in external light such as sunlight or indoor light from the external light intake section as main light.

According to the surface light source and the liquid crystal display device of the present invention, since the light guide plate is used, the cost of parts is greatly reduced. When obtaining the amount of emitted light, not only can the power supplied to the light source be reduced, but also the light source can be made unnecessary depending on the application. Also,
According to the liquid crystal display device of the present invention, since the external light intake portion of the light guide plate does not protrude from the display surface of the liquid crystal panel, the user of the device can be insured with less factors causing injuries, and furthermore, In addition, it is possible to prevent the external light intake section itself from being damaged and to maintain the degree of freedom in design.

[Brief description of the drawings]

FIG. 1 is a schematic view of a conventional liquid crystal display device.

FIG. 2 is a perspective view showing a light guide plate according to the present invention.

FIG. 3 is a graph showing luminance distribution characteristics.

FIG. 4 is a graph showing viewing angle characteristics.

FIG. 5 is a perspective view showing a light guide plate according to the present invention.

FIG. 6 is a schematic view showing a surface light source according to the present invention.

FIG. 7 is a perspective view showing a light guide plate.

FIG. 8 is a schematic diagram illustrating a cross-sectional shape of a prism portion of a triangular prism.

FIG. 9 is a graph showing a change in a luminance distribution characteristic with respect to a prism pitch.

FIG. 10 is a schematic diagram showing a liquid crystal display device including the surface light source according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 1 a external light intake portion 1 b side surface 1 c light incident surface 1 d light reflection surface 1 e first lens portion 1 f lenticular unit lens 1 g second lens portion 2 surface light source 3 light source 5 reflection plate 6 diffusion plate 7 lens sheet 8 liquid crystal display device 9 LCD panel

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Higuchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. No. 5 Inside Sanyo Electric Co., Ltd. (56) References JP-A-8-179322 (JP, A) JP-A-9-5529 (JP, A) JP-A-9-15426 (JP, A) JP-A-9-95 113730 (JP, A) JP-A-8-122534 (JP, A) JP-A 63-47297 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13357 F21V 8 / 00 601 G02B 6/00 331

Claims (9)

(57) [Claims] 1. A light guide plate which is integrally molded with resin, comprising a preparative external light join the club incorporating external light, and a light emitting surface for emitting the external light taken in from the outside light intake portion, wherein The external light intake section protrudes from the light exit surface.
A first lens portion formed of a plurality of concave or convex lenticular unit lenses is formed on the light emitting surface, and the lenticular directions of the plurality of lenticular unit lenses of the first lens portion are substantially parallel to each other. And a light guide plate substantially orthogonal to the longitudinal direction of the external light intake section. 2. The light guide plate according to claim 1, wherein an angle of a top of the plurality of lenticular unit lenses of the first lens unit is 125 to 165 degrees. 3. The light guide plate according to claim 1, wherein the angle of the top of the plurality of lenticular unit lenses of the first lens unit is about 150 degrees. 4. The light guide plate according to claim 1, wherein a plurality of concave or convex shapes formed of the same resin as the light guide plate are provided on a light reflecting surface facing the light emitting surface. A second lens unit comprising a lenticular unit lens, wherein the plurality of lenticular unit lenses of the second lens unit are arranged such that their ridge directions are substantially parallel to each other, and the plurality of lenticular unit lenses of the first lens unit. A light guide plate, which is substantially perpendicular to the ridge direction of the lenticular unit lens. 5. The light guide plate according to claim 4, wherein the angle of the top of the plurality of lenticular unit lenses of the second lens portion is 125 to 165 degrees. 6. The light guide plate according to claim 4, wherein an angle of a top of the plurality of lenticular unit lenses of the second lens portion is about 150 degrees. 7. A light guide plate according to claim 1, further comprising: a light source attached to at least one surface of the light guide plate other than the external light intake portion, the light exit surface, and the light reflection surface. A surface light source, comprising: 8. A light guide plate according to any one of claims 1 to 6 or a surface light source according to claim 7, and a liquid crystal mounted in close proximity to a light exit surface of said light guide plate. A liquid crystal display device comprising: a panel. 9. The method for manufacturing a light guide plate according to claim 1, further comprising a step of molding the light guide plate with a mold. .