JP3500098B2 - Lighting device and display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device (so-called front light) provided on the display surface side to illuminate the display surface.
In particular, the present invention relates to a linear light source including a point light source and a linear light guide.

[0002]

2. Description of the Related Art A non-emissive display device typified by a liquid crystal display device is indispensable as a display means for electronic equipment because it consumes less power and can be made smaller and thinner. The liquid crystal display device is roughly classified into a transmissive liquid crystal display device and a reflective liquid crystal display device. A transmissive liquid crystal display device is equipped with a backlight which is provided on the back side and illuminates a display screen from the back surface. Is equipped with a so-called front light which is provided on the display surface side and illuminates the display screen from the front. This front light is superior to the backlight in that it consumes less power because it can be illuminated by external light, and various configurations have been developed for practical use ( For example, JP-A-10-3119
15 and JP-A-10-153777).

A linear light source is used in these illuminating devices, and a cold cathode fluorescent tube is usually used. The linear light source is composed of a point light source and a linear (rod-shaped) light guide. Has been developed (for example, Japanese Patent Laid-Open No. 11-
191307).

[0004]

FIG. 5 shows a schematic configuration diagram of a display device having a front light. Reference numeral 51 is a reflective liquid crystal display panel for displaying an image, 52 is a front light provided on the display surface side of the liquid crystal display panel 51, and the front light 52 is a linear light source 53 such as a cold cathode fluorescent tube or a linear light source. A light guide plate 54 that illuminates the display screen of the liquid crystal display panel 51 by allowing light from the light source 53 to enter from the side and passing external light, and a display screen of the liquid crystal display panel 51 of the light guide plate 54 for improving visibility. It is composed of an antireflection film 55 attached to the opposite surface.

The surface of the light guide plate 54 opposite to the surface on which the antireflection film 55 is adhered has a first inclined surface 56 which is inclined toward the incident surface a on which the light from the linear light source 53 is incident, Since the second inclined surfaces 57 that incline toward the surface opposite to the incident surface a are alternately formed, and the plurality of first inclined surfaces 56 and the plurality of second inclined surfaces 57 are parallel to each other in the length direction, The top line and the valley line formed by the sides where the inclined surface 56 and the second inclined surface 57 contact each other are also in parallel.

When a plane including a plurality of valley lines is a virtual plane (broken line in FIG. 5), the inclination angle β of the first inclined surface 56 with respect to the virtual plane is the second inclined surface 57 with respect to the virtual plane. It is formed to be much larger than the inclination angle α, for example, the angle β is 43 ° and the angle α is 2 °. Therefore, the first inclined surface 5 with respect to the virtual plane
The projected area of 6 is much smaller than the projected area of the second inclined surface 57 with respect to the virtual plane (about 1:27 in this case).
Has become. Further, the light guide plate 54 is formed so as to have a so-called wedge-shaped cross-sectional shape in which the thickness (the distance between the virtual plane and the surface on which the antireflection film 55 is attached) becomes smaller as the distance from the incident surface a increases. ing.

In FIG. 5, in order to simplify the description, the first inclined surface 56 and the second inclined surface 57 are formed so that the top line and the valley line are parallel to the incident surface of the light guide plate 54. However, in many cases, as shown in FIG.
No. 4 is formed so that the top line and the valley line form a predetermined angle θ (θ is about 5 to 25 °, which is 22 ° in this example) with respect to the incident surface a, and is installed on the liquid crystal display panel 51. It This is because the pixels are arranged in a matrix in the liquid crystal display panel 51, and thus moire fringes are prevented from occurring in relation to the top line and the valley line of the light guide plate 54.

By the way, FIG. 6 shows an LED as a linear light source.
The top view of a front light in the case of using a light source composed of a point light source 61 and a linear light guide 62 is shown.
In such a configuration, when the light from the linear light source is supplied to the light guide plate 54, the light from the point light source 61 is incident on the light guide body 62, and the light is incident surface a of the light guide plate 54 of the light guide body 62. The light is emitted from the surface opposite to and enters the incident surface a of the light guide plate 54. At this time, all the light from the point light source 61 needs to be incident on the light guide 62, but in most cases, the light is emitted from the point light source 61 and the light entering portion of the light guide 62 is connected. Due to the imperfections or the relationship between the size of the point light source and the size required for the light guide 62, part of the light from the point light source 61 does not enter the light guide 62 but leaks and is directly incident on the light guide plate 54. Sometimes. The light directly incident on the light guide plate 54 from the point light source 61 is such that the top line and the valley line are inclined at a predetermined angle θ with respect to the incident surface a, and the inclination angles of the surfaces of the first inclined surface 56 and the second inclined surface 57. It is thought that this is caused by the bright line L (see FIG. 6) in a direction substantially orthogonal to the top line and the valley line.
Raise on.

The front light in which such a bright line L is generated deteriorates the display quality of the display screen, and is not practically used as an illuminating device. Since such a bright line L is also generated by a slight leak of light from the point light source 61, the production yield as a front light is significantly reduced.

The present invention has been made in view of such a point, and in a front light using a linear light source composed of a point light source and a linear light guide, even if light leaks from the point light source, the front light is on the light guide plate. It is an object of the present invention to provide a front light capable of suppressing the generation of bright lines and improving the manufacturing yield. Another object of the present invention is to provide a display device having a front light that suppresses the generation of bright lines and has good display performance.

[0011]

According to a first aspect of the present invention, there is provided a lighting device including a linear light source, an incident surface on which light from the linear light source is incident, and an emission surface and an emission surface on which the incident light is emitted. A linear light source comprises a point light source means and a light from the point light source means, the light guide plate having a light guide plate facing each other and reflecting light incident from an incident surface and transmitting light from the outside. And a linear light guide that emits light to the incident surface of the light guide plate, and the first light source is inclined in a predetermined direction on the opposite surface of the light guide plate.
The second slanted surfaces that slant in different directions from the slanted surfaces and the first slanted surfaces are alternately formed to form the first slanted surface and the second slanted surface.
The inclined surfaces form parallel top lines and valley lines, respectively, and the top lines and the valley lines are provided so as to be inclined at an angle with respect to the incident surface, and the point light source means includes the top line or the valley lines and the incident surface. It is characterized in that it is arranged near the end in the length direction of the incident surface of the light guide plate on the side where the angle formed is obtuse.

In the illumination device of the present invention according to claim 2, in the invention according to claim 1, the linear light guide member faces an emission surface for emitting the light from the point light source means and the emission surface. It is characterized in that it has an opposing surface, and the opposing surface is provided with emission direction control means for emitting the light emitted from the emission surface with an inclination toward the point light source means.

According to a third aspect of the present invention, there is provided a display device comprising: the illuminating device according to the first or second aspect; and a non-light emitting type display means provided on the exit surface side of the light guide plate.

[0014]

1 is a schematic configuration diagram showing an embodiment of a lighting device and a display device according to the present invention. It should be noted that all the figures are drawn schematically for easy understanding, and are different from actual dimensions and scale ratios.

Reference numeral 1 is a reflective liquid crystal display panel as a non-emissive display means for displaying an image, and 2 is a front light as an illuminating device provided on the display screen side of the liquid crystal display panel 2.

The front light 2 is composed of a linear light source 3, which is composed of an LED 31 as a point light source means and a linear light guide 32 which linearly emits light from the LED 31.
A light guide plate 4 for illuminating the display screen of the liquid crystal display panel 1 by allowing light from the linear light source 3 to enter from an incident surface described later and passing light from the outside, and a liquid crystal display of the light guide plate 4 for improving visibility. An antireflection film 5 attached to a surface (a rear surface described later) of the panel 1 facing the display screen, a linear light source 3 (especially a linear light guide body) whose inner surface is a reflective surface and excluding an emission surface described later. 32) It is composed of a reflector 6 wound around the periphery.

The light guide plate 4 is made of a translucent material such as acrylic resin and is a flat surface, which is an incident surface 41 facing the linear light source 3 and on which light from the linear light source 3 is incident.
And a back surface 42 as an emission surface to which the antireflection film 5 is attached, and an opposite surface that faces the back surface 42, reflects the light from the linear light source 3 that is incident from the incident surface 41, and transmits the light from the outside. Has 43.

The facing surface 43 is a first inclined surface 44 and a first inclined surface 4 which are inclined in a predetermined direction so as to face the incident surface 41.
4, a plurality of parallel first inclined surfaces 44 and a plurality of parallel second inclined surfaces 45 are alternately formed, and the first inclined surfaces 44 and the second inclined surfaces 45 are formed. A top line and a valley line are formed on the side where the inclined surface 45 contacts. At this time, the top lines and the valley lines are alternately present and are in parallel with each other. Then, as shown in FIG. 2, the top line and the valley line are at a predetermined angle θ (θ is 5 to 25) with respect to the incident surface 41.
The first inclined surface 44 and the second inclined surface 45 are provided so as to incline by about 20 ° (22 ° in this embodiment).

When a plane including a plurality of valley lines is a virtual plane (broken line in FIG. 1), the first inclined surface 44 with respect to the virtual plane is a plane orthogonal to the top line and the valley line.
Is formed to be much larger than the inclination angle α of the second inclined surface 45 with respect to the virtual plane.
The angle β is formed to be 43 ° and the angle α is formed to be 2 ° (however, FIG. 1 is not a cross section taken along a plane orthogonal to the top line and the valley line, and therefore is schematically shown). Therefore, the projected area of the first inclined surface 44 on the virtual plane is much smaller than the projected area of the second inclined surface 45 on the virtual plane (about 1:27 in this embodiment).

Further, the light guide plate 4 has a so-called wedge-shaped cross-sectional shape in which the distance between the back surface 42 and the imaginary plane of the facing surface 43 becomes smaller as the distance from the incident surface 41 increases, that is, the thickness becomes thinner. Has been formed. For example, the thickness of the light guide plate 4 on the incident surface 41 side is about 1.2 mm.
The thickness of the surface side opposite to 1 is about 1 mm, and the distance between the valley line and the top line in the projected state on the virtual plane is about 13 μm.

The linear light guide 32 of the linear light source 3 has a light guide plate 4
LED made of translucent material such as acrylic resin
An incident surface 33 on which the light from 31 is incident, an emission surface 34 that opposes the incident surface 41 of the light guide plate 4 and emits the light incident from the incident surface 33, and a flat surface as an opposed surface that opposes the emission surface 34. It has a reflective surface 35. The exit surface 34 is formed to have a size substantially equal to or larger than the entrance surface 41 of the light guide plate 4, and the linear light guide 32 faces the entrance surface 33 from the entrance surface 33 side. As you go to the face side,
It is formed in a wedge-shaped cross-sectional shape in which the distance (thickness) between the emission surface 34 and the reflection surface 35 is reduced (thinned). For example, the distance (thickness) between the emitting surface 34 and the reflecting surface 35 on the incident surface 33 side.
Is 2.8 mm, and the exit surface 34 on the side facing the entrance surface 33
The distance (thickness) between the reflective surface 35 and the reflecting surface 35 is 0.5 mm, and these distances are appropriately changed and determined according to the specifications such as the illumination capability and the size required for the front light 2.

The shape of the light guide plate 4 or the linear light guide 32 is formed by injection molding using a thermoplastic resin such as polycarbonate including acrylic resin, and the first inclined surface and the second inclined surface are formed. Even if it has it, it can be integrally and easily formed by a general molding process using a mold.

When assembling the front light,
The exit surface 34 of the linear light guide 32 and the entrance surface 41 of the light guide plate 4 are opposed to each other (this embodiment shows a gap between the exit surface 34 and the entrance surface 41. 34 and the incident surface 41 may be in contact with each other), and the linear light source 3 and the light guide plate 4 are provided. Further, at that time, as shown in FIG. 2, the LED 31 of the linear light source 3 is on the side opposite to the angle θ formed by the top line and the valley line with the incident surface 41, that is, one of the top line and the valley line and the incident surface 41. The incident surface 4 of the light guide plate 4 on the side where the angle formed with is obtuse.
It is provided by being arranged near the end in the length direction of 1.

Now, in such a device, first, the case where the display screen of the liquid crystal display panel 1 is illuminated by light from the outside (external light) will be described. External light such as sunlight or room light comes from above the facing surface 43 and enters the second inclined surface 4
5 and the first inclined surface 44 (almost second from the area ratio)
The light enters the light guide plate 4 through the inclined surface 45). External light that has entered the light guide plate 4 passes through the light guide plate 4 and exits from the back surface 42, and illuminates the display screen of the liquid crystal display panel 1 through the antireflection film 5. Light reflected from the display screen of the liquid crystal display panel 1 due to illumination enters the light guide plate 4 from the back surface 42 through the antireflection film 5, and exits from the second inclined surface 45 to the outside to be recognized by an observer. It

When the display screen of the liquid crystal display panel 1 is illuminated by the front light 2, the LED 31 is turned on. When the LED 31 is turned on, the light from the LED 31 enters from the incident surface 33 of the linear light guide 32, and the linear light guide 3 is illuminated.
While traveling in the inside of 2, the light is emitted from the emission surface 34 directly or after being reflected by the reflection surface 35 or another side surface. Exit surface 3
Light is emitted from 4 along the surface, that is, linearly. still,
The light that has passed through the linear light guide 32 without being reflected by the reflecting surface 34 or the other side surface is reflected by the reflector 6 and is incident on the linear light guide 32 again, and is used as the light emitted from the emission surface 34. To be done.

Linear light source 3 (emission surface 3 of linear light guide 32)
The light emitted from 4) enters from the incident surface 41 of the light guide plate 4, is reflected by the first inclined surface 44, and is emitted from the back surface 42. Light is reflected or passes through the surface of the light guide plate 4 because the light guide plate 4 has a critical angle of the material of the light guide plate (for example, acrylic resin) with respect to air. Light traveling at a small angle passes with refraction, and light traveling at an angle larger than the critical angle is reflected. The light emitted from the back surface 42 illuminates the display screen of the liquid crystal display panel 1 through the antireflection film 5. Light reflected from the display screen of the liquid crystal display panel 1 due to illumination enters the light guide plate 4 from the rear surface 42 through the antireflection film 5, and
The light is emitted from the inclined surface 45 to the outside and is recognized by an observer.

When the LED 31 is turned on, LE
Even if a part of the light from D31 does not enter the incident surface 33 of the linear light guide 32 and is directly incident on the light guide plate 4 from the incident surface 41, such light does not enter the installation position of the LED 31 and the top. Due to the relationship between the line and the valley line, the light does not enter the light guide plate 4 at an angle orthogonal to the top line and the valley line of the light guide plate 4. Therefore, L
Even if part of the light from the ED 31 is directly incident on the light guide plate 4, the bright line L as shown in FIG. 6 does not occur, and the display quality of the display screen of the liquid crystal display panel 1 is deteriorated. Is prevented. Therefore, since the generation of the bright line L is suppressed, it is possible to improve the manufacturing yield of the front light.

By the way, as shown in FIG. 2, when the display screen of the liquid crystal display panel 1 is illuminated by the front light 2, the linear light source 3 is separated from the LED 31 with respect to the incident surface 41 of the light guide plate 4. Light having an inclination of direction is incident. This is because the reflecting surface 35 is formed in a shape that approaches the emitting surface 34 with respect to the emitting surface 34 as the distance from the incident surface 33 increases. When light enters the light guide plate 4 in such an orientation, the amount of light reflected by the first inclined surface 44 decreases, and the light that contributes to the illumination of the display screen of the liquid crystal display panel 1 is the first light as described above. Since the light is reflected by the inclined surface 44, there is a possibility that the amount of illumination light will be small and sufficient luminance cannot be obtained.

Therefore, in such a case, the light emitted from the emission surface 34 is guided to the reflection surface 35 of the linear light guide 32 by L.
It is possible to increase the brightness of the front light by forming the emission direction control means that emits light with an inclination closer to the ED 31.

FIG. 4 is an external view showing an example of a linear light guide 32 'having a plurality of grooves 36 as an emission direction control means. This linear light guide 32 'has substantially the same structure as the linear light guide 32 shown in FIG. 1 or 2, but is different in that a plurality of grooves 36 are formed in the reflecting surface 35'.

This groove 36, as shown in FIG.
3 ', and the inclined surface 37 is inclined with respect to the emission surface 34' at an angle γ of 45 °. By providing the groove 36, the light from the LED 31 enters through the incident surface 33 ′, then travels in the linear light guide 32 ′ while being reflected by the emitting surface 34 ′ or the reflecting surface 35 ′, and is inclined. When reflected by the surface 37, the light having an inclination toward the LED 31 is emitted from the emission surface 34 ′.
Therefore, the light is incident on the light guide plate 4 in such a direction that the amount of light reflected by the first inclined surface 44 increases. Therefore,
Since a large amount of light contributes to the illumination of the display screen of the liquid crystal display panel 1, the amount of illumination light increases and the brightness can be improved.

In the present embodiment, the angle γ of the inclined surface 37 of the groove 36 as the emitting direction control means with respect to the emitting surface 34 'was 45 °, but this angle γ is 45 ° or more and less than 90 °, preferably. The same effect can be obtained even in the range of 45 ° or more and about 70 °. Further, the depth and interval at which the grooves 36 are formed may be constant regardless of the distance from the incident surface 33 ′, or may be increased as the distance from the incident surface 33 ′ increases (for example, 5 ~ 100μ
m), the interval may be narrowed (for example, 10 to 200 μm) (either one or both of the depth and the interval may be changed), and may be appropriately selected depending on the size and the light amount required for the linear light source. It is determined.

[0033]

As is apparent from the above description, the present invention provides a linear light source including a point light source and a linear light guide in the front light, and an inclined surface in a predetermined direction on the facing surface facing the emitting surface. The first inclined surface and the second inclined surface inclined in a direction different from the direction in which the first inclined surface is inclined are alternately formed, and the first inclined surface and the second inclined surface form parallel top lines and valley lines, respectively. In the case where a light guide plate that is configured and is provided with the top line and the valley line inclined at an angle with respect to the incident surface is used, the point light source on the side where the angle between the top line or the valley line and the incident surface is an obtuse angle. By arranging near the end in the length direction of the incident surface of the light guide plate,
Even if light leaks from the point light source, it is possible to prevent a bright line from being generated on the light guide plate. Thus, it becomes possible to improve the manufacturing yield as a front light.

Further, by providing the reflecting surface of the linear light guide with a groove (emission direction control means) for emitting the light emitted from the emission surface with an inclination toward the point light source, the brightness can be improved. Becomes

Further, there is provided a display device having a front light which suppresses the generation of bright lines and which can realize a bright display screen with high brightness and good display performance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a lighting device and a display device according to the present invention.

FIG. 2 is an explanatory diagram of a front light shown in FIG.

FIG. 3 is an explanatory view showing another embodiment of the lighting device according to the present invention.

FIG. 4 is an external view of a linear light guide according to the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a display device having a front light for explaining a problem.

FIG. 6 is an explanatory view of the front light shown in FIG.

[Explanation of symbols]

1 Liquid crystal display panel (non-emissive display means) 2 Front light (illuminator) 3 linear light source 31 LED (point light source means) 32 linear light guide 33 Incident surface 34 exit surface 35 Reflective surface (opposing surface) 36 grooves (outgoing direction control means) 4 Light guide plate 41 incident surface 42 Rear surface (emission surface) 43 Opposing surface 44 First inclined surface 45 Second inclined surface

Claims (3)

(57) [Claims] 1. A linear light source, an incident surface on which the light from the linear light source is incident, an emission surface for emitting the incident light, and a light from the outside that faces the emission surface and reflects the light incident on the incident surface. In a lighting device having a light guide plate having a facing surface that transmits light, the linear light source has a point light source means, and a linear light guide body that receives light from the point light source means and emits the light to the incident surface of the light guide plate. And a first surface inclining in a predetermined direction on the opposite surface of the light guide plate.
The second slanted surfaces that slant in different directions from the slanted surfaces and the first slanted surfaces are alternately formed to form the first slanted surface and the second slanted surface.
The inclined surfaces form parallel top lines and valley lines, respectively, and the top lines and the valley lines are provided so as to be inclined at an angle with respect to the incident surface, and the point light source means includes the top line or the valley lines and the incident surface. An illuminating device, characterized in that the illuminating device is arranged in the vicinity of an end in the length direction of the incident surface of the light guide plate on the side where the angle formed is an obtuse angle. 2. The linear light guide has an emission surface for emitting the light from the point light source means and an opposing surface facing the emission surface, and the opposing surface is provided with the light emitted from the emission surface. The illumination device according to claim 1, further comprising an emission direction control unit that emits light with an inclination closer to the point light source unit. 3. A lighting device according to claim 1 or 2,
A display device comprising a non-emissive display means provided on the exit surface side of a light guide plate.