JP4044308B2 - Surface light emitting device, liquid crystal display device including the same, and portable electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting device enabled to reduce the light reflected by an emitting surface of a light guide plate mounted to the surface light emitting device, getting into the visual field of an observer when the surface light emitting device is lit. SOLUTION: A surface light emitting derive 10 comprises a light source, and a light guide plate 12 with a structure of making the light from the light source get into the end side surface and get out from an emitting surface 12b. A surface at the opposite side of the emitting surface 12b of the light guide plate 12 is designated as a reflection surface 12c changing the direction of the light traveling inside the light guide plate 12, to which, indentations for changing the direction of the light traveling inside the light guide plate 12, are repeatedly formed, and indentations for restricting the reflecting direction of the light when a part of the light traveling inside the light guide plate 12 is reflected at the emitting surface 12b, are repeatedly formed to the emitting surface 12b. The pitch P2 of a convex part 32f formed to the reflection surface 12b, and the horizontal distance x between a vertex of the convex part 12f formed to the reflection surface 12c, and a vertex of the convex part 32f formed to the emitting surface 12b fulfills the relation: x<=P2 /8.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface light emitting device, a liquid crystal display device including the surface light emitting device, and a portable electronic device, and particularly close to a normal direction to a display surface of the liquid crystal display device including the surface light emitting device and the portable electronic device. When the display is observed from the direction, it is possible to reduce the incidence of reflected light reflected on the exit surface of the light guide plate provided in the surface light-emitting device when the surface light-emitting device is turned on. The present invention relates to a technique for improving the contrast ratio by making it easy to see and preventing blurring and blurring of black display.
[0002]
[Prior art]
In general, in a reflective liquid crystal display device that displays using ambient light as a light source, the brightness depends on the amount of ambient light, so in an environment where sufficient ambient light cannot be obtained, such as when used in a dark place, There has been a problem that the visibility of the display is extremely lowered.
In order to solve the above problem, a liquid crystal display device of a type in which a surface light emitting device (front light) is arranged on the front side of a reflective liquid crystal display unit and used as an auxiliary light source has been proposed. The liquid crystal display device equipped with this front light operates as a normal reflection type liquid crystal display device in an environment where sufficient ambient light can be obtained such as outdoors in the daytime, and the front light is turned on as a light source if necessary. It is.
[0003]
An example of a cross-sectional view of a reflective liquid crystal display device provided with a front light as described above is shown in FIG. In this figure, the liquid crystal display device 200 includes a liquid crystal display unit 220 and a front light 210 disposed on the front surface (upper surface in FIG. 7) of the liquid crystal display unit 220. The front light 210 includes a light guide plate 212 and a light source 213 disposed on a side end surface 212a of the light guide plate 212. The light guide plate 212 is disposed on the front surface (upper surface in FIG. 7) of the liquid crystal display unit 220. Has been placed.
The light guide plate 212 is made of an injection-molded transparent acrylic resin or the like. The light guide plate 212 introduces light from the light source 213 disposed on the side end surface 212a therein, and transmits the light propagating through the light guide plate 212 to the light guide plate. The light is emitted from an emission surface 212b which is the lower surface of 212 (the surface on the liquid crystal display unit 220 side). On the other hand, the upper surface (outer surface) of the light guide plate 212 is a reflective surface 212c. The first inclined surface portion 216 formed on the reflecting surface 212c is inclined with respect to the emission surface 212b, and the first inclined surface portion. Concavities and convexities 212 d are formed in which second slope portions 217 following 216 are periodically formed. The unevenness 212d has a shape in which convex portions 212f and wedge-shaped grooves 212g are alternately provided in a stripe shape.
The light exit surface 212b of the light guide plate 212 is a flat surface. An antireflection film 215 is attached to the emission surface 212d.
[0004]
The liquid crystal display unit 220 has a configuration in which a first substrate 221 and a second substrate 222 which are opposed to each other with a liquid crystal layer 223 interposed therebetween are joined and integrated with a sealant 224, and the liquid crystal layer 223 side of the first substrate 221 is disposed on the liquid crystal layer 223 side. Includes a reflective layer 225 including a reflective film for reflecting light incident on the liquid crystal display unit 220, and a display circuit 226 for driving and controlling the liquid crystal layer 223, which are sequentially stacked. A display circuit 227 is provided on the 223 side.
[0005]
In the liquid crystal display device 200 having the above configuration, the light R1 emitted from the light source 213 when the front light 210 is turned on is introduced into the light guide plate 212 from the side end surface 212a of the light guide plate 212 and propagates through the light guide plate 212. At the same time, the light is reflected by the first inclined surface portion 216 formed on the reflection surface 212c and the propagation direction is changed to the direction toward the emission surface 212b, and the light is emitted from the emission surface 212b.
The light emitted from the emission surface 212b enters the liquid crystal display unit 220 as illumination light R2, passes through the second substrate 222, the display circuit 227, the liquid crystal layer 223, and the display circuit 226, and reaches the reflection layer 225. The light is reflected by the reflective layer 225, returns to the outside of the liquid crystal display unit 220, passes through the exit surface 212b of the light guide plate 212 and the second inclined surface portion 217 of the reflective surface 212c, and reaches the observer (user) ob. In this way, the display of the liquid crystal display unit 220 is visually recognized by the observer ob.
[0006]
By the way, as the display performance of the liquid crystal display device, the visual recognition such as (1) resolution, (2) contrast, (3) screen brightness, (4) vividness of color, (5) wide viewing angle range, etc. The property is required to be good.
In addition, when a liquid crystal display device is incorporated into a device that is used with an inclined display surface when a display is viewed, such as a portable information terminal such as a mobile phone or a notebook personal computer (PC), the display is generally performed. It is often seen from a direction close to the normal direction with respect to the surface, specifically, a direction within a range of ± 10 degrees from the normal direction.
FIG. 8 is an explanatory diagram showing a state in which the display unit 1000 including the liquid crystal display device 200 having the above-described configuration uses a mobile phone provided in the main body 1050. In FIG. 8, H is a normal to the display surface of the display unit 1000, ob is an observer (user), α is an observation direction of the observer ob, β is a range of ± 10 ° from the normal direction H, and R2 is a guide. The light R1 emitted from the emission surface 212b of the light plate 221 is reflected by the reflection layer 225 of the liquid crystal display unit 220, and R3 is a part of the light R1 emitted from the light source 213 reflected by the emission surface 212b of the light guide plate 212. Reflected light.
[0007]
[Problems to be solved by the invention]
However, in the conventional liquid crystal display device 200 having the structure shown in FIG. 7, the light R <b> 1 emitted from the light source 213 when the front light 210 is turned on propagates through the light guide plate 212 and is reflected by the first inclined surface portion 216. When the light reaches the emission surface 212b, part of the light R1 is reflected from the emission surface 212b without being emitted toward the liquid crystal display unit 220, and the reflected light R3 passes through the reflection surface 212c of the light guide plate 212 to be liquid crystal. The light is emitted to the outside of the display device 200. Also, when the light R1 propagating through the light guide plate 212 reaches the light exit surface 212b, a part of the light R1 is reflected without being emitted from the light exit surface 212b toward the liquid crystal display unit 220, and this reflection is further performed. The light R3 passes through the reflection surface 212c of the light guide plate 212 and is emitted to the outside of the liquid crystal display device 200.
These reflected lights R3 are also normally concentrated in a direction close to the normal direction H with respect to the display surface of the liquid crystal display device 200, more specifically in a direction β within the range of ± 10 degrees from the normal direction H. When the observer ob observes the display from a normal viewpoint (a direction close to the normal direction H, more specifically, a direction within ± 10 degrees from the normal direction H), the reflected light R3 is reflected by the observer. Since the light is incident in the field of view, it is difficult to see the display, and even if black is displayed, blurring and blurring occur, resulting in a display with a low contrast ratio.
[0008]
Such a problem also occurs when the liquid crystal display device 200 is used in the display unit 1000 of the mobile phone shown in FIG. R3 in FIG. 8 is reflected light that is reflected from the light exit surface 212b of the light guide plate 212 when the light R1 emitted from the light source 213 is operated by turning on the front light 210 of the liquid crystal display device 200 used in the display unit 1000. R3 passes through the reflection surface 212c of the light guide plate 212 and is emitted to the outside of the display unit 1000.
[0009]
The present invention has been made in order to solve the above-described problem, and the reflected light reflected by the exit surface of the light guide plate provided in the surface light-emitting device when the surface light-emitting device is turned on is within the visual field of the observer. An object is to provide a surface light-emitting device that can reduce incidence. In addition, the present invention provides a liquid crystal display device that can improve display performance by providing such a surface light emitting device so that the display can be easily seen and the contrast ratio can be improved by preventing blurring and blurring of black display. One of the purposes. In addition, the present invention uses a liquid crystal display device having such a surface light emitting device as a display unit, thereby making it easy to see the display and preventing blurring and blurring of black display to improve the contrast ratio and improve display performance. An object is to provide portable electronic devices that can be used.
[0010]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention employs the following configuration.
  The surface light-emitting device of the present invention includes a light source and a light guide plate having a structure in which light from the light source is incident from a side end surface and is emitted from the output surface, and is a surface opposite to the output surface of the light guide plate. Is a reflection surface for changing the direction of the light propagating through the light guide plate, and the light propagating through the light guide plate is reflected on the reflection surface to change the light propagation direction. Concavities and convexities are periodically provided, and concavities and convexities for periodically controlling the light reflection direction when a part of the light propagating inside the light guide plate is reflected by the light exit surface are provided on the light exit surface. TheAnd the convex pitch provided on the reflecting surface is P ₁ , P is the pitch of the protrusions provided on the exit surface ₂ P ₁ = P ₂ And the horizontal displacement between the top of the convex portion provided on the reflecting surface and the top of the convex portion provided on the exit surface is a distance x, and the reflective surface of the light guide plate The provided unevenness is formed by periodically and continuously forming a first slope part formed in an inclined manner and a second slope part following the first slope part, and on the exit surface of the light guide plate. The unevenness provided is formed by periodically and continuously forming a third inclined surface portion formed in an inclined manner and a fourth inclined surface portion following the third inclined surface portion. Tilt angle θ ₁ , And the inclination angle of the second slope portion is θ ₂ , The angle of inclination of the third slope portion is θ ₃ , And the inclination angle of the fourth slope portion is θ ₄ When these inclination angles are ₃ = Θ ₄ > Θ ₂ <Θ ₁ By using the relationship expressed by, the reflected light on the exit surface is controlled to be reduced.It is characterized by that.
  In the present invention, the light whose reflection direction is controlled by the projections and depressions provided on the exit surface means that the light propagating through the light guide plate when the surface light emitting device is turned on is reflected by the reflection surface. The light that has been reflected from the light exit surface without being emitted from the light exit surface to the outside (the liquid crystal display unit side when the surface light emitting device is provided in the liquid crystal display device). Of the light that has directly propagated through the light guide plate when the surface light-emitting device is turned on and reaches the light-emitting surface directly, the light is emitted from the light-emitting surface to the outside. The light that is not emitted (to the side) and is reflected by this exit surface.
[0011]
According to the surface light emitting device having such a configuration, the condition of the unevenness provided on the reflection surface of the light guide plate and the condition of the unevenness provided on the exit surface of the light guide plate are adjusted, more specifically, provided on the reflection surface. The convex pitch, the convex pitch provided on the output surface, the horizontal distance between the top of the convex provided on the reflective surface and the top of the convex provided on the output surface, the output of the light guide plate The light emitted from the light source propagates through the inside of the light guide plate when the surface light-emitting device is turned on by adjusting the inclination angles of the plurality of slope portions constituting the unevenness provided on the surface, and is reflected on the reflection surface. When a part of this light is reflected by the exit surface after being reflected, the exit direction of the reflected light is set to the normal direction of the surface light emitting device (this surface light emitting device is connected to the liquid crystal display device). When equipped, the normal to the display surface of the liquid crystal display device It can be removed from the direction close to direction), and more specifically can be the direction out of the range from the normal direction to 10 degrees ±.
In addition, when the light propagating inside the light guide plate reaches the light exit surface directly without being reflected by the reflection surface when the surface light emitting device is turned on, when a part of the light is reflected by the light exit surface, The outgoing direction of the reflected light is removed from a direction close to the normal direction of the surface light emitting device (when the surface light emitting device is provided in the liquid crystal display device, the normal direction of the display surface of the liquid crystal display device). More specifically, the direction can be outside the range of ± 10 degrees from the normal direction.
[0012]
Therefore, according to the surface light-emitting device of the present invention, when the surface light-emitting device is turned on, the observer (user) can perform a normal viewpoint (a direction close to the normal direction, more specifically, ± 10 degrees from the normal direction). When the surface light-emitting device is viewed in a direction within a range of (2), it is possible to reduce the incidence of the reflected light reflected by the light exit surface of the light guide plate into the observer's visual field.
[0013]
  Also,According to the surface light emitting device having such a configuration, even when the light propagating through the light guide plate when the surface light emitting device is turned on is reflected by the reflection surface and reaches the emission surface, Even when light propagating inside reaches the exit surface directly, when a part of this light is reflected by the exit surface, the exit direction of the reflected light is changed to the normal direction of the surface emitting device (this When the surface light emitting device is provided in the liquid crystal display device, it can be removed from a direction close to the normal direction of the display surface of the liquid crystal display device, and more specifically, a range of ± 10 degrees from the normal direction. In other words, the reflected light is less likely to be emitted in a direction near the normal direction of the surface light emitting device, and more specifically, the reflected light is up to ± 10 degrees from the normal direction. It becomes difficult to be emitted within the range.
  Therefore, according to this surface light-emitting device, when this surface light-emitting device is turned on, the observer (user) is in a normal viewpoint (direction close to the normal direction, more specifically, a range of ± 10 degrees from the normal direction). When the surface light emitting device is viewed in the inner direction), it is possible to prevent the reflected light reflected by the exit surface of the light guide plate from entering the observer's field of view.
[0016]
  In the surface light emitting device of the present invention having the above configuration,Inclination angle θ of the third slope portion ₃ And the inclination angle θ of the fourth slope portion ₄ But1 ° ≦ θ₃≦ 7 °, 1 ° ≦ θ₄It is more preferable to satisfy the relationship of ≦ 7 °. According to the surface light emitting device having such a configuration, even when the light propagating through the light guide plate when the surface light emitting device is turned on is reflected by the reflection surface and reaches the emission surface, Even when light propagating inside reaches the exit surface directly, when a part of this light is reflected by the exit surface, the exit direction of the reflected light is close to the normal direction of the surface light emitting device. Can be removed from the direction, more specifically, can be outside the range of ± 10 degrees from the normal direction, in other words, the reflected light is emitted in a direction closer to the normal direction of the surface emitting device. More specifically, the reflected light is less likely to be emitted within a range of ± 10 degrees from the normal direction. Therefore, according to the surface light-emitting device, when the observer views the surface light-emitting device from a normal viewpoint when the surface light-emitting device is turned on, the reflected light reflected by the exit surface of the light guide plate is within the viewer's visual field. Can be prevented.
[0017]
A liquid crystal display device according to the present invention includes the surface light-emitting device according to the present invention having any one of the above-described configurations.
According to the liquid crystal display device having such a configuration, since the surface light-emitting device of the present invention having any one of the above-described configurations is provided, an observer can have a normal viewpoint (display surface of the liquid crystal display device) when the surface light-emitting device is turned on. When the display is observed in a direction close to the normal line direction, more specifically, a direction within ± 10 degrees from the normal line direction), the reflected light reflected by the light exit surface of the light guide plate Since it can be prevented from entering the field of view, the display can be easily seen, the blur and blur of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved.
[0018]
The portable electronic device of the present invention is characterized in that a liquid crystal display device including the surface light emitting device of the present invention having any one of the above-described configurations is provided in a display unit.
According to the portable electronic device having such a configuration, when the surface light emitting device of the liquid crystal display device provided in the display unit is turned on, the observer can observe the normal viewpoint (the direction close to the normal direction of the display surface of the display unit, more specifically, When the display is observed in a direction within a range of ± 10 degrees from the normal direction), it is possible to prevent the reflected light reflected by the exit surface of the light guide plate from entering the observer's visual field. As a result, the display becomes easy to see and the blur and blur of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. Each drawing referred to in this embodiment is for explaining the configuration and operation of a light guide plate, a surface light emitting device, a liquid crystal display device, and a portable electronic device. The size, thickness, dimensions, etc. of each part are as follows. They are different from actual light guide plates, surface light emitting devices, liquid crystal display devices, and portable electronic devices.
(Embodiments of surface light emitting device and liquid crystal display device)
FIG. 1 is a perspective view illustrating a schematic configuration of a liquid crystal display device including a front light (surface light emitting device) according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating the liquid crystal display device of FIG. is there.
[0020]
The liquid crystal display device 1 of the present embodiment is generally configured by a liquid crystal display unit 20 and a front light 10 that is disposed on the front side (the upper surface side in the drawing) of the liquid crystal display unit 20 and illuminates the liquid crystal display unit 20. The front light 10 includes a transparent light guide plate 12 and a bar light source (long light source) 13. The bar light source 13 is disposed on a side end surface 12 a that introduces light into the light guide plate 12.
The light guide plate 12 is disposed on the front surface side (the upper surface side in the drawing) of the display area of the liquid crystal display unit 20 and irradiates the liquid crystal display unit 20 with light introduced from the light source 13, such as a transparent acrylic resin. It is composed of As shown in FIG. 1, the lower surface (surface facing the liquid crystal display unit 20) of the light guide plate 12 is an emission surface 12b from which light for illuminating the liquid crystal display unit 20 is emitted, and this emission surface 12b. The upper surface on the opposite side (the outer surface of the light guide plate 12) is a reflective surface 12c for changing the direction of light propagating through the light guide plate 12.
[0021]
As a material constituting the light guide plate 12, transparent resin materials such as polycarbonate resin and epoxy resin, glass, and the like can be used in addition to acrylic resin. Moreover, if a specific example is given, it is not particularly limited, but Arton (trade name: manufactured by JSR) and the like can be mentioned as suitable ones.
As shown in FIG. 2, in the front light 10 of the present embodiment, the antireflection film 11 is provided on the side end face 12 a that introduces the light from the bar light source 13 into the light guide plate 12. The emission surface 12 b is a surface on which the light for illuminating the liquid crystal display unit 20 is emitted by being disposed to face the liquid crystal display unit 20. An antireflection film 15 for preventing light reflection is provided on the emission surface 12b.
[0022]
The reflecting surface 12c is provided with irregularities 12d in which convex portions 12f and wedge-shaped grooves (concave portions) 12g are alternately formed in a stripe shape in order to reflect light propagating through the light guide plate 12 and change the propagation direction. It has been. Here, the direction protruding to the opposite side of the liquid crystal display unit 220 is referred to as a convex portion 12f, and the direction recessed toward the side opposite to the liquid crystal display unit 220 (the direction protruding to the liquid crystal display unit 220 side) is a groove ( (Concave part) called 12 g. The unevenness 12d is formed by alternately forming inclined first slopes 16 and second slopes 17 following the first slopes 16. Of the first slope portion 16 and the second slope portion 17, the first slope portion 16 is formed with a steeper inclination angle. Further, an antireflection film 18 for preventing light reflection is provided on the reflection surface 12c.
[0023]
Pitch (convex pitch) P between adjacent convex portions 12f and 12f provided on the reflective surface 12c₁Is 140 μm ≦ P₁≦ 240 μm is preferably satisfied, more preferably 160 μm ≦ P₁It is desirable to satisfy the relationship of ≦ 180 μm. Convex pitch P₁Is smaller than 140 μm, the luminance of the surface light emitting device is lowered, so that the display performance such as the luminance and contrast ratio of the screen of the liquid crystal display device provided with the surface light emitting device is lowered.₁If it exceeds 240 μm, bright lines will be visible when viewing the display of a liquid crystal display device equipped with this surface light emitting device, making it difficult to see the display.
[0024]
Inclination angle θ of first slope 16₁Is 43 ° ≦ θ₁It is preferable to satisfy the relationship of ≦ 47 °, more preferably 43 ° ≦ θ.₁It is desirable to satisfy the relationship of ≦ 45 °. Inclination angle θ of first slope 16₁Is outside the above range (θ₁<43 ° or 47 ° <θ₁) Does not match the characteristics of the reflective liquid crystal display device, and the brightness of the screen of the reflective liquid crystal display device provided with the surface light emitting device is lowered.
Inclination angle θ of second slope portion 17₂Is 1.8 ° ≦ θ₂≦ 2.5 ° is preferably satisfied, more preferably 2.0 ° ≦ θ₂It is desirable to satisfy the relationship of ≦ 2.4 °. Inclination angle θ of second slope portion 17₂Is less than 1.8 °, the luminance of the surface light emitting device is lowered, the display performance such as the contrast ratio of the liquid crystal display device provided with the surface light emitting device is lowered, and θ₂If the angle exceeds 2.5 °, the luminance distribution in the surface of the light guide plate 12 of the surface light emitting device is lowered, and the display performance of the liquid crystal display device provided with the surface light emitting device is lowered.
[0025]
The exit surface 12b is provided with a convex portion 32f and a wedge-shaped groove (concave portion) 32g in order to control the light reflection direction when a part of the light propagating inside the light guide plate 12 is reflected by the exit surface. Irregularities 32d formed alternately in stripes are provided periodically. Here, the direction protruding to the side opposite to the liquid crystal display unit 220 is referred to as a convex portion 32f, and the direction recessed toward the side opposite to the liquid crystal display unit 220 (the direction protruding to the liquid crystal display unit 220 side) is a groove ( (Recess) 32g. The light whose reflection direction is controlled by the irregularities 32 means that the light that propagates in the light guide plate 12 when the surface light emitting device 10 is turned on is reflected by the reflection surface 12c and reaches the emission surface 12b. Light that is not emitted from 12b to the outside (to the liquid crystal display unit 20 side) but reflected by the emission surface 12b, and is directly emitted by light propagating through the light guide plate 12 when the surface light emitting device 10 is turned on. Of the light reaching 12b, the light is not emitted from the emission surface 12b to the outside (to the liquid crystal display unit 20 side) but is reflected by the emission surface 12b.
[0026]
The unevenness 32d is formed by alternately forming the third inclined surface portion 36 formed in an inclined manner and the fourth inclined surface portion 37 following the third inclined surface portion 36.
Pitch (convex portion pitch) P between adjacent convex portions 32f and 32f provided on the emission surface 12b₂Is P₁−30 μm ≦ P₂≦ P₁+30 μm is preferably satisfied, more preferably P₁−10 μm ≦ P₂≦ P₁It is desirable to satisfy the relationship of +10 μm. Convex pitch P₂Is P₁If it is smaller than −30 μm, the amount of light propagating inside the light guide plate 12 is reduced and light is directly emitted to the viewer side.₂Is P₁If it exceeds +30 μm, the amount of light propagating inside the light guide plate 12 is reduced and light is directly emitted to the viewer.
[0027]
FIG. 3 shows the horizontal distance (horizontal misalignment, in other words, the top of the projection 12f provided on the reflection surface 12c of the front light 10 of the present embodiment and the top of the projection 32f provided on the exit surface 12b. For example, it is an explanatory diagram of a direction x along the substrate surface of the substrate 22 of the liquid crystal display unit 20 described later.
In the front light 10 of the present embodiment, P₁= P₂Or P₁≠ P₂In either case, the horizontal distance (horizontal displacement) x between the top of the convex portion 12f and the top of the convex portion 32f is x ≦ P.₂/ 8 is preferably satisfied, and more preferably x ≦ P.₂It is desirable to satisfy the relationship / 24, and more preferably P₁= P₂And x = 0 (when there is no horizontal displacement), it is desirable to satisfy the relationship.
[0028]
Even when the light R1 propagating through the light guide plate 12 when the front light 10 is turned on is reflected by the reflecting surface 12c and reaches the output surface 12b, the light R1 propagating through the light guide plate 12 is directly emitted. Even when the light reaches the surface 12b, the reflected light R3 in which a part of the light R1 is reflected by the light emission surface 12b is emitted to the outside of the front light 10 (outside of the liquid crystal display device 1). x is P₂Is greater than / 8, the reflected light R3 is close to the normal direction H of the front light 10 (normal direction H to the display surface of the liquid crystal display device 1), more specifically ± 10 from the normal direction H. Concentrate in the direction β within the range up to degrees.
[0029]
Inclination angle θ of the third slope portion 36_ThreeIs 1 ° ≦ θ_ThreeMore preferably, the relationship of ≦ 7 ° is satisfied, and more preferably 5 ° ≦ θ._ThreeIt is desirable to satisfy the relationship of ≦ 6 °.
Inclination angle θ of the fourth slope portion 37_FourIs 1 ° ≦ θ_FourMore preferably, the relationship of ≦ 7 ° is satisfied, and more preferably 5 ° ≦ θ._FourIt is desirable to satisfy the relationship of ≦ 6 °.
Inclination angle θ of the third slope portion 36_ThreeAnd the inclination angle θ of the fourth inclined surface portion 37_FourMay be the same size or different angles.
[0030]
Even when the light R1 propagating through the light guide plate 12 when the front light 10 is turned on is reflected by the reflecting surface 12c and reaches the output surface 12b, the light R1 propagating through the light guide plate 12 is directly emitted. Even when the light reaches the surface 12b, the reflected light R3 in which a part of the light R1 is reflected by the light emission surface 12b is emitted to the outside of the front light 10 (outside of the liquid crystal display device 1). The inclination angle θ of the slope portion 36 of_ThreeAnd / or the inclination angle θ of the fourth inclined surface portion 37._Four Is outside the above range (an angle smaller than 1 ° or an angle larger than 7 °), the reflected light R3 has a normal direction H of the front light 10 (a normal direction with respect to the display surface of the liquid crystal display device 1). H), more specifically, in the direction β within the range of ± 10 degrees from the normal direction H.
[0031]
The bar light source 13 is a cold cathode tube, an organic EL element (organic electroluminescence element), an LED (light emitting diode), or a combination of an LED and a rod-shaped light guide. Any material that can be irradiated can be suitably used. 1 to 2 show a case where the bar light source 13 is configured by combining the bar-shaped light guide 13a and the LEDs 13b and 13b disposed at both ends thereof.
[0032]
The liquid crystal display unit 20 is configured by joining and integrating a first substrate 21 made of glass or the like and a second substrate 22 facing each other with a liquid crystal layer 23 interposed therebetween. A reflective layer 25 including a metal reflective film and a display circuit 26 are sequentially laminated on the surface of the first substrate 21 on the liquid crystal layer 23 side, and on the surface of the second substrate 22 on the liquid crystal layer 23 side, Each of the display circuits 27 is formed. Thus, the liquid crystal display unit 20 is a reflective liquid crystal display unit including the reflective layer 25 for reflecting light incident from the outside.
Although not shown, the display circuits 26 and 27 include an electrode layer made of a transparent conductive film for driving the liquid crystal layer 23, an alignment film for controlling the alignment of the liquid crystal layer 23, and the like. In some cases, a configuration including a color filter for performing color display may be used.
[0033]
The reflective layer 25 is formed by, for example, forming a metal reflective film made of aluminum, silver, or the like on an organic film made of acrylic resin or the like having a concavo-convex shape formed on the surface, and covering the reflective film and the organic film. In this way, a flattening film made of an acrylic resin or the like is formed. The reflective layer 25 may include a color filter. In that case, it is preferable to form a color filter immediately above the reflective film. With such a configuration, a color filter can be disposed on the light reflecting surface, so that high-quality color display is possible with reduced color shift and parallax.
[0034]
Here, the surface of the organic film constituting the reflective layer 25 of the liquid crystal display unit 20 and the shape of the reflective film formed on the organic film will be described below with reference to FIG.
FIG. 4 is an enlarged perspective view showing the organic film and the reflective film formed on the reflective layer 25 of the liquid crystal display unit 20. In this figure, the surface of the organic film 28 is continuously formed so that a large number of recesses 28 a whose inner surface forms a part of a spherical surface overlap each other, and a reflective film 29 is formed on the organic film 28. . On the surface of the reflective film 29 formed on the organic film 28 having a large number of concave portions 28a as described above, a large number of concave portions 29a whose inner surface forms part of a spherical surface are continuously formed. Yes.
[0035]
The organic film 28 is formed by forming a resin layer made of a photosensitive resin or the like on a substrate in a planar shape, and then transferring a transfer mold made of a silicone resin or the like having a surface shape opposite to the surface of the organic film 28 shown in FIG. Is pressed onto the surface of the resin layer, and then the resin layer is cured. The reflective film 29 is formed on the surface of the organic film 28 and reflects light incident on the liquid crystal display unit 20, and a metal material having a high reflectance such as aluminum or silver is formed by sputtering or vacuum deposition. It is formed by a film method.
[0036]
The recesses 29a shown in FIG. 4 are randomly formed with a depth in the range of 0.1 μm to 3 μm, and the pitches of the adjacent recesses 29a are randomly arranged in the range of 5 μm to 100 μm. Is preferably set in the range of −30 degrees to +30 degrees.
In particular, it is particularly important that the inclination angle distribution of the inner surface of the recess 29a is set in the range of −30 degrees to +30 degrees, and the pitch of the adjacent recesses 29a is randomly arranged in all directions in the plane. This is because if there is regularity in the pitch of the adjacent recesses 29a, there is a problem that the interference color of light comes out and the reflected light is colored. On the other hand, if the inclination angle distribution on the inner surface of the recess 29a exceeds the range of −30 ° to + 30 °, the diffusion angle of the reflected light is excessively widened, the reflection intensity is lowered, and a bright display cannot be obtained (the diffusion angle of the reflected light is This is because it becomes 36 degrees or more in the air, the reflection intensity peak inside the liquid crystal display device decreases, and the total reflection loss increases.
[0037]
On the other hand, if the depth of the concave portion 29a exceeds 3 μm, when the concave portion 29a is flattened in a later step, the top of the convex portion cannot be filled with the flattening film, and desired flatness cannot be obtained. When the pitch of the adjacent recesses 29a is less than 5 μm, there is a restriction on the production of the transfer mold used to form the organic film 28, and the processing time is extremely long, and a shape capable of obtaining desired reflection characteristics is formed. Inability to generate interference light occurs. In addition, the transfer mold for forming the surface shape of the organic film 28 transfers the surface shape of a transfer mold mother die produced by pressing a large number of diamond indenters against a base material such as stainless steel to a silicone resin or the like. However, since it is desirable that the tip diameter of the diamond indenter is practically 30 μm to 200 μm, the pitch of the adjacent concave portions 29 a is desirably 5 μm to 100 μm.
[0038]
In the liquid crystal display unit 20, the reflective film 29 constituting the reflective layer 25 has the shape as described above. Therefore, light incident from the outside can be efficiently reflected and scattered, and a bright reflective display and a wide range can be obtained. A viewing angle can be realized. This is because the depth and pitch of the recesses 29a shown in FIG. 4 are controlled within the above ranges, and the inner surface of the recesses 29a is spherical.
That is, since the depth and pitch of the recess 29a are controlled, the inclination angle of the inner surface of the recess 29a that governs the light reflection angle is controlled within a certain range. It becomes possible to control within a certain range. In addition, since the inner surface of the recess 29a is a spherical surface that is symmetrical with respect to all directions, the above reflection efficiency can be obtained with respect to all directions of the reflective film 29. That is, a brighter display can be performed from any direction.
[0039]
The light guide plate 12 of the present embodiment can be introduced into the light guide plate 12 without reflecting the light of the light source 13 by the side end surface 12 by the antireflection film 11 provided on the side end surface 12a. That is, according to the present invention, the amount of light propagating through the light guide plate 12 can be greatly increased, so that the amount of light emitted from the exit surface 12b of the light guide plate 12 and illuminating the liquid crystal display unit 20 can be increased. it can.
The antireflection film 11 can be formed by attaching an antireflection film to the side end face 12 a of the light guide plate 12. With such a configuration, since a commercially available antireflection film can be used, the amount of light emitted from the front light 10 can be increased without greatly changing the structure of the light guide plate 12 or the manufacturing process. The brightness of the device 1 can be improved.
[0040]
Alternatively, the antireflection film 11 can be formed by a dip coating method. Further, according to the dip coating method, the emission surface 12b and the antireflection films 15 and 18 on the reflection surface 12c shown in FIG. 2 can be formed simultaneously with the antireflection film 11, so that the production process can be simplified. Cost can be reduced.
[0041]
The liquid crystal display device 1 having the above configuration cannot provide sufficient ambient light such as when used in a dark place in addition to reflective display using ambient light in an environment where sufficient ambient light such as sunlight or illumination is obtained. In the environment, the front light 10 can be turned on to perform reflection display using the light.
First, the case where reflective display using ambient light is performed by the liquid crystal display device 1 shown in FIGS. 1 and 2 will be described. Since the antireflection film 18 is provided on the reflection surface 12c of the light guide plate 12 which is the outermost surface of the liquid crystal display device 1, the reflectance of light incident on the reflection surface 12c can be kept low. That is, it is possible to prevent the visibility of the liquid crystal display device 1 from being significantly reduced due to strong reflection of light in a specific direction on the reflecting surface 12c.
In addition, light incident on the light guide plate 12 from the outside through the reflection surface 12c passes through the emission surface 12b and enters the liquid crystal display unit 20, and since the reflection surface 15 is also provided on the emission surface 12b. The antireflection film 15 can reduce the reflectance to 1% or less. Therefore, it is possible to reduce the light that is reflected by the emission surface 12b and returns to the outside to reduce the visibility of the liquid crystal display device 1.
[0042]
The light incident on the liquid crystal display unit 20 passes through the second substrate 22, the display circuit 27, the liquid crystal layer 23, and the display circuit 26 and reaches the reflection layer 25, and this light is reflected by the reflection layer 25. Then, after passing through the display circuit 26, the liquid crystal layer 23, the display circuit 27, the second substrate 22 and being emitted to the outside of the liquid crystal display unit 20, and further entering the light guide plate 12 again through the emission surface 12b, It passes through the reflecting surface 12c and reaches the observer ob. Here, even when the light reflected by the reflection layer 25 passes through the emission surface 12b, the antireflection film 15 is provided, so that the reflectance at the emission surface 12b can be 1% or less, and the emission surface 12b. As a result, it is possible to reduce the occurrence of reflected light that is reflected by the liquid crystal display unit 20. Even when the light incident on the light guide plate 12 again passes through the reflection surface 12c, the antireflection film 18 is formed on the reflection surface 12c. Generation of light returning to the inside can be reduced, and light that does not contribute to display can be prevented from remaining inside the front light 10 or the liquid crystal display unit 20 and causing a decrease in visibility.
As described above, the liquid crystal display device 1 according to this embodiment includes the light guide plate 12 that can reduce the light reflected on each surface by providing the antireflection films 15 and 18 on the surface through which the light passes. Therefore, it is possible to perform reflective display with good visibility by efficiently using ambient light.
[0043]
Next, a case where display is performed by turning on the front light 10 will be described. In this case, the light R <b> 1 emitted from the bar light source 13 shown in FIGS. 1 to 2 is introduced into the light guide plate 12 through the side end face 12 a of the light guide plate 12. Since the antireflection film 11 is provided on the side end face 12a as described above, the reflectance of the side end face 12a is reduced, and the light of the bar light source 13 that is reflected and lost by the side end face 12a. Thus, the light from the bar light source 13 is introduced into the light guide plate 12 with almost no attenuation.
[0044]
Next, the light R1 propagating through the light guide plate 12 is reflected by the first inclined surface portion 16 to change its propagation direction, and reaches the emission surface 12b. Most (most) of the light R1 reaching the emission surface 12b passes through the emission surface 12b and enters the liquid crystal display unit 20, but a part of the light R1 is reflected by the emission surface 12b, and this reflected light R3 is further reflected. Passes through the reflection surface 12 c of the light guide plate 12 and is emitted to the outside of the liquid crystal display device 1. Further, the light R1 propagating through the light guide plate 12 may reach the light exit surface 12b directly without being reflected by the first inclined surface portion 16, but in this case also, most of the light R1 reaching the light exit surface 12b is reached. (Most) passes through the exit surface 12b and enters the liquid crystal display unit 20, but part of the light R1 is reflected by the exit surface 12b, and this reflected light R3 passes through the reflective surface 12c of the light guide plate 12. Is emitted to the outside of the liquid crystal display device 1. Here, since the antireflection film 15 is provided on the emission surface 12b, the reflectance at the emission surface 12b can be reduced to 1% or less, so that the light reflected by the emission surface 12b passes through the reflection surface 12c. In addition, the amount of light emitted to the outside of the liquid crystal display device 1 and reaching the observer Ob can be significantly reduced. Further, in the present embodiment, the unevenness 32d as described above for controlling the light reflection direction when a part of the light R1 propagating inside the light guide plate is reflected by the output surface 12b is periodically formed on the output surface 12b. Therefore, the emission direction of the reflected light R3 reflected by the emission surface 12b can be removed from a direction close to the normal direction H of the front light 10 (normal direction H to the display surface of the liquid crystal display device 1). More specifically, the direction can be outside the range of ± 10 degrees from the normal direction H.
[0045]
Further, by adjusting the condition of the unevenness 12d provided on the reflecting surface 12c of the light guide plate 12 and the condition of the unevenness 32d provided on the emitting surface 12b, in particular, the top of the convex portion 12f provided on the reflecting surface 12c and the emitting surface 12b. The distance x in the horizontal direction of the top of the convex portion 32f provided at x is P ≦ P₂The inclination angle θ of the third inclined surface portion 36 that satisfies the relationship of / 8 and / or constitutes the unevenness 32d provided on the emission surface 12b._Three  And the inclination angle θ of the fourth inclined surface portion 37_FourIs 1 ° ≦ θ_Three≦ 7 °, 1 ° ≦ θ_FourWhen the front light 10 is turned on, the light R1 propagating through the light guide plate 12 is reflected by the reflecting surface 12c and reaches the emitting surface 12b. However, even when the light R1 propagating through the light guide plate 12 reaches the output surface 12b directly, when a part of the light R1 is reflected by the output surface 12b, the reflected light R3 The emission direction can be removed from a direction close to the normal direction H of the front light 10 (the normal direction H of the display surface of the liquid crystal display device 1), more specifically, from the normal direction H to ± 10 degrees. In other words, the reflected light R3 is less likely to be emitted in a direction near the normal direction H of the front light 10, and more specifically, the reflected light R3 is ± 10 from the normal direction H. To be emitted within the range of degrees Kunar. In particular, P₁= P₂In the case where the relationship x = 0 is satisfied, the above effect can be increased.
[0046]
Next, the light R1 emitted from the emission surface 10b of the front light 10 enters the liquid crystal display unit 20 as illumination light R2, passes through the second substrate 22, the display circuit 27, the liquid crystal layer 23, and the display circuit 26. The light R2 reaches the reflection layer 25, and is reflected by the reflection layer 25. The light R2 passes through the display circuit 26, the liquid crystal layer 23, the display circuit 27, and the second substrate 22, and is emitted to the outside of the liquid crystal display unit 20. Further, the light enters the light guide plate 12 again through the emission surface 12b. Even in the illumination light R2 that passes through the emission surface 12b, the reflectance is reduced to 1% or less by the antireflection film 15, so that the light reflected by the emission surface 12b and returning to the liquid crystal display unit 20 can be reduced. Therefore, it is possible to prevent light that does not contribute to display from entering the liquid crystal display unit 20 and causing display blurring.
[0047]
Then, the illumination light R2 incident on the light guide plate 12 from the liquid crystal display unit 20 side through the emission surface 12b passes through the reflection surface 12c and reaches the observer ob. Even when the illumination light R2 passes through the reflection surface 12c, the antireflection film 18 is formed on the reflection surface 12c, so that the illumination light R2 is reflected by the reflection surface 12c and returns to the inside of the light guide plate 12. Therefore, it is possible to prevent light that does not contribute to the display from remaining in the front light 10 or the liquid crystal display unit 20 and causing a decrease in visibility.
According to the front light 10 of the present embodiment, in particular, the front light 10 in which the unevenness 12d as described above is periodically provided on the reflection surface 12c and the unevenness 32d as described above is periodically provided on the emission surface 12b. When the front light 10 is turned on (when the light R2 is emitted from the bar light source 13 and is incident on the light guide plate 12 through the side end face 12a and propagated), the observer ( When the user sees the front light 10 from a normal viewpoint (a direction close to the normal direction H, more specifically, a direction within ± 10 degrees from the normal direction H), the light guide plate 12 It is possible to prevent the reflected light R3 reflected by the exit surface 12b from entering the observer ob's field of view.
[0048]
The liquid crystal display device 1 according to the present embodiment performs reflection display using ambient light by providing the light guide plate 12 with the front light 10 provided with the antireflection films 11, 15, and 18 as described above. In both the case and the case where the reflective display is performed by turning on the front light 10, high-quality display with excellent visibility can be performed.
In particular, in the liquid crystal display device 1 of the present embodiment, when the front light 10 is turned on, the observer ob has a normal viewpoint (a direction close to the normal direction H of the display surface of the liquid crystal display device 1, more specifically, the legal Preventing the reflected light R3 reflected by the exit surface 12b of the light guide plate 12 from entering the field of view of the observer ob when the display is observed in a direction within a range of ± 10 degrees from the line direction H). Therefore, the display is easy to see and the blur and blur of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved.
For this reason, when the liquid crystal display device 1 of the present embodiment is used in a display unit of a portable electronic device such as a mobile phone or a notebook PC, an observer can turn on the front light 10 of the liquid crystal display device 1 provided in the display unit. When the display is observed from a normal viewpoint (a direction close to the normal direction of the display surface of the display unit, more specifically, a direction within ± 10 degrees from the normal direction), the output surface of the light guide plate 12 Since the reflected light R3 reflected by 12b can be prevented from entering the field of view of the observer ob, the display can be easily seen, and the blurring and blurring of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved. It can be improved.
[0049]
In the light guide plate 12 provided in the front light 10 of the present embodiment shown in FIGS. 1 and 2, the shape of the reflection surface 12 c is changed to the first inclined surface portion 16 and the second inclined surface following the first inclined surface portion 16. Although the case where the portions 17 are alternately formed has been described, a trapezoidal shape in which a flat portion is provided between the adjacent convex portions 12f and 12f can also be formed. Further, in the light guide plate 12 of the present embodiment, the case where the third inclined surface portion 36 and the fourth inclined surface portion 37 following the third inclined surface portion 36 are alternately formed in the shape of the emission surface 12b is described. However, in addition to this, a trapezoidal shape in which a flat portion is provided between adjacent convex portions 32f and 32f may be a continuous shape.
[0050]
【Example】
(Experimental example 1)
First, by performing injection molding using acrylic resin Delpet 80NH (trade name: manufactured by Asahi Kasei Co., Ltd.) as a material, convex portions and wedge-shaped grooves (concave portions) are alternately formed in a stripe shape on one surface (upper surface). Various light guide plates were prepared in which unevenness was provided, and the other surface (lower surface) was provided with unevenness in which protrusions and wedge-shaped grooves (recesses) were alternately formed in a stripe shape. In each light guide plate, one surface (upper surface) is a reflection surface, and the surface opposite to the reflection surface is an emission surface. Convex pitch P formed on the reflective surface of this light guide plate₁Is 240 μm, and the convex pitch P provided on the exit surface₂The horizontal distance x between the top of the convex portion provided on the reflecting surface and the top of the convex portion provided on the exit surface was changed within a range of 5 to 180 μm. The unevenness provided on the reflection surface is formed by alternately forming the first slope portion and the second slope portion following the first slope portion, and the inclination angle θ of the first slope portion is₁43 °, the inclination angle θ of the second slope₂Was set to 2.2 °. The unevenness provided on the emission surface is formed by alternately forming a third slope portion and a fourth slope portion following the third slope portion, and an inclination angle θ of the third slope portion._Three5 °, the inclination angle θ of the fourth slope part_FourWas 5 °.
[0051]
Next, an antireflection film ARP4T (trade name: manufactured by Dai Nippon Printing Co., Ltd.) was attached to the exit surface and the reflection surface of each light guide plate. Subsequently, an antireflection film ARP4T was attached to the side end face of each light guide plate.
Next, a bar light source provided with white LEDs at both ends of the rod-shaped light guide was disposed on the side end surface of each light guide plate to which the antireflection film was attached to form various front lights.
[0052]
Next, the relationship between the viewing angle and the luminance was examined with BM5 (trade name: manufactured by Topcon) for the characteristics of the various front lights produced. The result is shown in FIG. In FIG. 5, the viewing angle of 0 deg is the normal direction of the front light (the normal direction of the display surface when the liquid crystal display device is provided).
[0053]
From the results shown in FIG. 5, the front light with x = 40 μm, 60 μm, and 180 μm has a luminance (cd ···) within a viewing angle range of −10 ° to + 10 ° (within ± 10 degrees from the normal direction). m^-2) Is large, it can be seen that there is a large amount of reflected light reflected from the exit surface of the light guide plate.
In contrast, the front light with x = 0, 5, and 30 μm has a luminance (cd · m) within a viewing angle range of −10 ° to + 10 ° (within ± 10 degrees from the normal direction).^-2), Especially when x = 0 and 5 μm, the luminance (cd · m) within the range of viewing angle of −5 ° to + 5 ° (within ± 5 degrees from the normal direction).^-2) Is small, it can be seen that there is a large amount of reflected light reflected from the exit surface of the light guide plate. From this, x ≦ P₂If the front light satisfying the relationship of / 8 is provided in the display unit of the liquid crystal display device, the observer can observe the normal viewpoint (a direction closer to the normal direction of the display surface of the liquid crystal display device, more specifically, when the front light is turned on. To prevent the reflected light reflected by the exit surface of the light guide plate from entering the observer's field of view when the display is observed in a direction within a range of ± 10 degrees from the normal direction). Therefore, it is considered that the display is easy to see, the black display blur and blur can be prevented, the contrast ratio can be improved, and the display performance can be improved.
[0054]
(Experimental example 2)
First, by performing injection molding using acrylic resin Delpet 80NH (trade name: manufactured by Asahi Kasei Co., Ltd.) as a material, convex portions and wedge-shaped grooves (concave portions) are alternately formed in a stripe shape on one surface (upper surface). Various light guide plates were prepared in which unevenness was provided, and the other surface (lower surface) was provided with unevenness in which protrusions and wedge-shaped grooves (recesses) were alternately formed in a stripe shape. In each light guide plate, one surface (upper surface) is a reflection surface, and the surface opposite to the reflection surface is an emission surface. Convex pitch P formed on the reflective surface of this light guide plate₁Is 240 μm, and the convex pitch P provided on the exit surface₂Was 240 μm, and the horizontal distance x between the top of the convex portion provided on the reflecting surface and the top of the convex portion provided on the exit surface was 10 μm. The unevenness provided on the reflection surface is formed by alternately forming the first slope portion and the second slope portion following the first slope portion, and the inclination angle θ of the first slope portion is₁43 °, the inclination angle θ of the second slope₂Was set to 2.2 °. The projections and depressions provided on the emission surface are formed by alternately forming a third slope portion and a fourth slope portion following the third slope portion, and the inclination angle θ of the third slope portion._Three, Inclination angle θ of the fourth slope portion_FourWas changed in the range of 0 ° to 7 °. Θ_ThreeAnd θ_FourWere the same size. And θ_Three, Θ_FourIn the case of = 0 °, it is a case of a flat surface on which the unevenness is not formed on the exit surface of the light guide plate.
[0055]
Next, an antireflection film ARP4T (trade name: manufactured by Dai Nippon Printing Co., Ltd.) was attached to the exit surface and the reflection surface of each light guide plate. Subsequently, an antireflection film ARP4T was attached to the side end face of each light guide plate.
Next, a bar light source provided with white LEDs at both ends of the rod-shaped light guide was disposed on the side end surface of each light guide plate to which the antireflection film was attached to form various front lights.
[0056]
Next, the relationship between the viewing angle and the luminance was examined with BM5 (trade name: manufactured by Topcon) for the characteristics of the various front lights produced. The result is shown in FIG. In FIG. 6, the viewing angle of 0 deg is the normal direction of the front light (the normal direction of the display surface when the liquid crystal display device is provided).
[0057]
From the results shown in FIG._Three, Θ_Four= 0 °, 0.5 ° front light has a luminance (cd · m) within a viewing angle range of −10 ° to + 10 ° (within ± 10 degrees from the normal direction).^-2) Is large, it can be seen that there is a large amount of reflected light reflected from the exit surface of the light guide plate.
Compared to this_Three, Θ_Four= 1 °, 5 °, and 7 ° front light with a viewing angle in the range of −10 ° to + 10 ° (within ± 10 ° from the normal direction) (cd · m)^-2) Is small, it can be seen that there is a large amount of reflected light reflected from the exit surface of the light guide plate. θ_Three, Θ_Four  Is greater than 7 °, the amount of reflected light is small, but the amount of light from the exit surface of the front light is also small, which is not preferable because the display becomes dark. From this, 1 ° ≦ θ_Three≦ 7 °, 1 ° ≦ θ_FourWhen a front light satisfying the relationship of ≦ 7 ° is provided in the display unit of the liquid crystal display device, the observer can observe a normal viewpoint (a direction closer to the normal direction of the display surface of the liquid crystal display device, when the front light is turned on). Specifically, when the display is observed in a direction within a range of ± 10 degrees from the normal direction), the reflected light reflected by the exit surface of the light guide plate is prevented from entering the observer's field of view. Therefore, it is considered that the display is easy to see, the blur and blur of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved.
[0058]
【The invention's effect】
As described above in detail, according to the surface light-emitting device of the present invention, the condition of the unevenness provided on the reflection surface of the light guide plate and the condition of the unevenness provided on the exit surface of the light guide plate are adjusted more specifically. Is the convex pitch provided on the reflective surface, the convex pitch provided on the output surface, the top of the convex portion provided on the reflective surface and the top of the convex portion provided on the output surface. By adjusting the distance, the inclination angle of a plurality of inclined surfaces constituting the unevenness provided on the exit surface of the light guide plate, the light propagating through the light guide plate when the surface light emitting device is turned on is reflected on the reflective surface. Even when the light is reflected by the light and reaches the light exit surface, or even when the light propagating through the light guide plate reaches the light output surface directly, a part of the light is reflected by the light exit surface. In this case, the emission direction of the reflected light is set to the normal direction of the surface light emitting device ( When the surface light emitting device is provided in a liquid crystal display device, it can be removed from a direction close to the normal direction to the display surface of the liquid crystal display device, and more specifically, ± 10 degrees from the normal direction. It is possible to make the direction out of the range. Therefore, according to the surface light-emitting device of the present invention, when the surface light-emitting device is turned on, the observer (user) can perform a normal viewpoint (a direction close to the normal direction, more specifically, ± 10 degrees from the normal direction). When the surface light-emitting device is viewed in a direction within a range of (2), it is possible to reduce the incidence of the reflected light reflected by the light exit surface of the light guide plate into the observer's visual field.
[0059]
Further, according to the liquid crystal display device of the present invention, since the surface light emitting device of the present invention is provided, an observer can view the normal viewpoint (in the normal direction of the display surface of the liquid crystal display device) when the surface light emitting device is turned on. When the display is observed in a near direction, more specifically, a direction within a range of ± 10 degrees from the normal direction), the reflected light reflected by the exit surface of the light guide plate enters the observer's field of view. Therefore, it is easy to see the display, blurring and blurring of black display can be prevented, contrast ratio can be improved, and display performance can be improved.
Further, according to the portable electronic device of the present invention, when the surface light-emitting device of the liquid crystal display device provided in the display unit is turned on, the observer can observe a normal viewpoint (a direction closer to the normal direction of the display surface of the display unit, more specifically, To prevent the reflected light reflected by the exit surface of the light guide plate from entering the observer's field of view when the display is observed in a direction within a range of ± 10 degrees from the normal direction). Therefore, the display is easy to see and the blur and blur of black display can be prevented, the contrast ratio can be improved, and the display performance can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a schematic configuration of a liquid crystal display device including a front light (surface light emitting device) according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the liquid crystal display device of FIG.
FIG. 3 is a diagram for explaining a horizontal distance x between a top of a convex portion provided on the reflecting surface of the front light (surface light emitting device) of FIGS. 1 to 2 and a top of the convex portion provided on an exit surface; Illustration.
FIG. 4 is an enlarged perspective view showing a part of a reflective layer of a liquid crystal display unit provided in the liquid crystal display device of the present invention.
FIG. 5 is a diagram showing the relationship between the viewing angle and the luminance when the horizontal distance x between the top of the convex portion provided on the reflecting surface of the light guide plate and the top of the convex portion provided on the exit surface is changed.
FIG. 6 is a diagram showing the relationship between the viewing angle and the luminance when the inclination angles of the third slope part and the fourth slope part constituting the unevenness provided on the reflection surface of the light guide plate are changed.
FIG. 7 is a cross-sectional view illustrating an example of a liquid crystal display device including a conventional surface light emitting device.
8 is a diagram illustrating an example of a portable electronic device including the liquid crystal display device of FIG. 7 in a display unit.
[Explanation of symbols]
1 Liquid crystal display device
10 Front light (surface emitting device)
11, 15, 18 Antireflection film
12 Light guide plate
12a End face
12b Outgoing surface
12c Reflective surface
13 Bar light source (long light source)
13a Bar light guide
13b LED
12d, 32d uneven
12f, 32f Convex part
12g, 32g groove (concave)
16 1st slope part
17 Second slope
20 Liquid crystal display unit
36 Third slope
37 4th slope
P₁ Convex pitch
P₂Convex pitch
R1 light
R2 illumination light
R3 reflected light
x Horizontal distance
θ₁   Inclination angle
θ₂   Inclination angle
θ_Three   Inclination angle
θ_Four   Inclination angle

Claims (5)

A light source and a light guide plate having a structure in which light from the light source is incident from a side end surface and is emitted from the output surface, and a surface opposite to the output surface of the light guide plate is disposed inside the light guide plate. It is a reflection surface for changing the direction of propagating light, and the reflection surface is provided with irregularities for periodically reflecting the light propagating through the light guide plate and changing the propagation direction of the light, Irregularities for controlling the reflection direction of light when a part of the light propagating inside the light guide plate is reflected by the emission surface are periodically provided on the emission surface ,
P ₁ a projecting portion pitch provided in the reflecting surface, when the protrusion pitch provided on the exit surface was set to P _2, fulfills the relation P 1 ₌ P _2, the convex provided in the reflecting surface The displacement in the horizontal direction between the top of the projection and the top of the projection provided on the exit surface is the distance x,
The unevenness provided on the reflection surface of the light guide plate is formed such that a first slope portion formed in an inclined manner and a second slope portion following the first slope portion are periodically and continuously formed, The unevenness provided on the exit surface of the light guide plate is formed by periodically and continuously forming a third slope portion formed to be inclined and a fourth slope portion following the third slope portion,
The inclination angle of the first slope portion is θ ₁ , the inclination angle of the second slope portion is θ ₂ , the inclination angle of the third slope portion is θ ₃ , and the inclination angle of the fourth slope portion is θ ₄ and the time, each of these inclination angles of, by a relationship represented by _{θ 3 = θ 4> θ 2} <θ 1, characterized in that the light reflection at the exit surface is controlled so as to reduce A surface light emitting device. The distance x of the positional deviation in the horizontal direction between the top of the convex portion provided on the reflecting surface and the top of the convex portion provided on the exit surface is in the range of 5 to 180 μm. Surface light emitting device. Said third inclined surface portion inclined angle theta ₃ and the fourth inclined surface portion inclined angle theta ₄ of, and satisfy the _{1 ° ≦ θ 3 ≦ 7 °} , 1 ° ≦ θ 4 ≦ 7 ° the relationship The surface emitting device according to claim 1 or 2 . A liquid crystal display device comprising the surface light-emitting device according to any one of claims 1 to 3. A portable electronic device comprising the liquid crystal display device according to claim 4 in a display portion.

Images