JP4282453B2 - Surface light source device - Google Patents

Description

  The present invention relates to a surface light source device used for a liquid crystal display device or the like.

  A liquid crystal display device widely used in personal computers, mobile phones, and the like usually includes a light source device because the liquid crystal material does not emit light. In particular, in the case of a liquid crystal display device mounted on a mobile device, in order to reduce the thickness and weight, a light source such as a light emitting diode (LED) or a fluorescent tube, a thin light guide plate, and the light source repeatedly emits total reflection. In general, a surface light source device including light extraction means for emitting light guided through the light guide plate to the liquid crystal display panel side is generally used. As the light extraction means, a diffusing pattern obtained by dot printing of diffuse reflection ink, or an uneven shape such as a prism is often used.

  A perspective view of a conventional typical surface light source device is shown in FIG. The conventional surface light source device shown in FIG. 11 has a plurality of LEDs 30 used as a light source, a light guide plate 31 made of a transparent material such as acrylic, and dots of diffuse reflection ink on the surface of the light guide plate 31 facing the light exit surface 31a. It is comprised by the diffusion pattern 32 formed by printing, and the reflecting plate 33 arrange | positioned at the surface 31b side in which the diffusion pattern 32 of the light-guide plate 31 was formed.

  Light emitted from the LED 30 and guided to the inside of the light guide plate 31 from the light incident surface 31c travels inside the light guide plate 31 while repeating total reflection. When the light inside the light guide plate 31 strikes the diffusion pattern 32, the light is scattered by the diffusion pattern 32. When the scattered light enters the light emitting surface 31a at an angle smaller than the critical angle of total reflection, the light exits from the light emitting surface 31a to the outside. To do. The light transmitted through the portion where the diffusion pattern 32 on the lower surface 31b of the light guide plate 31 does not exist is reflected by the reflection plate 33 and returns to the inside of the light guide plate 31 again.

  In order to obtain in-plane uniformity of light intensity, the diffusion pattern 32 is printed so that the dot density increases as the distance from the LED 30 increases as illustrated in FIG. Since the conventional surface light source device shown in FIG. 11 is a thin surface light source device that emits light uniformly in a plane, it is used as a light source device for many liquid crystal display devices.

  In general, a liquid crystal display device mounted on a mobile device is often viewed from the front by a user. Therefore, in a liquid crystal display device mounted on a mobile device, the front luminance is emphasized among the display characteristics. However, since the conventional surface light source device shown in FIG. 11 uses the diffusion pattern 32 that is a scatterer as the light extraction means, light is emitted in a wide range on the liquid crystal display panel side, and in principle a high front surface. It was difficult to obtain brightness.

  In addition, there is a method of increasing the front luminance by increasing the number of LEDs, but adopting such a method means an increase in power consumption, and a liquid crystal display mounted on a mobile device that operates with a battery with a limited capacity It was not suitable for the light source device of the device.

  Patent document 1 and non-patent document 1 describe surface light source devices that can solve such problems. This surface light source device increases the front luminance by collecting the emitted light in a very narrow range centering on the front direction of the surface light source device. Hereinafter, the surface light source devices described in Patent Literature 1 and Non-Patent Literature 1 are referred to as “conventional surface light source devices having high front luminance”.

  FIG. 12 is a perspective view of a conventional surface light source device having a high front luminance, FIG. 13 is a top view of the conventional surface light source device having a high front luminance, and FIG. 14 is a sectional view taken along the line DD in FIG.

  A conventional surface light source device having a high front luminance has an LED 34 as a light source, a light guide plate 35 made of a transparent material such as acrylic, and a triangular groove-like shape formed on a surface 35b of the light guide plate 35 facing the light exit surface 35a. And a prism 36.

  The light emitted from the LED 34 and guided into the light guide plate 35 from the light incident surface 35c travels inside the light guide plate 35 while repeating total reflection. When the light inside the light guide plate 35 hits the reflection surface of the prism 36, the light is reflected by the prism 36, and the reflected light is emitted to the outside from the light emission surface 35a.

  The reflecting surface of the prism 36 is formed so as to extend in the X direction orthogonal to the Y direction, which is the radial direction of the circle centered on the LED 34, as shown in FIG. In other words, the prism 36 is configured by a groove extending in the X direction. The angle of inclination of the reflecting surface of the prism 36 is defined so that the light guided inside the light guide plate 35 is efficiently emitted in the normal direction of the light emitting surface 35a. The spacing between the adjacent prisms 36 is designed so that the spacing between the prisms 36 decreases as the distance from the LED 34 increases as shown in FIGS. 12 to 14 in order to obtain in-plane uniformity of light intensity. Has been.

  Here, the measurement result of the optical characteristic in the output surface 35a of the conventional surface light source device with high front luminance is shown in FIG. FIG. 15 shows the luminance-viewing angle distribution measured at the center of the exit surface 35a of the light guide plate 35 provided in the conventional surface light source device having a high front luminance. The characteristic curve 37 is the result of measurement in the Y direction, which is the radial direction of the circle centered on the LED 34, and the characteristic curve 38 is the result of measurement in the X direction orthogonal to the Y direction.

As can be seen from the characteristic curve 38, the half-value width of the luminance in the X direction is about ± 3 °. As can be seen from the characteristic curve 37, the half-value width of the luminance in the Y direction is about ± 15 °. When the same measurement is performed with respect to the conventional surface light source device shown in FIG. 11, the half value width of the luminance is ± 30 ° or more. It can be seen that they are efficiently collected in the line direction. In the conventional surface light source device having a high front luminance, since the emitted light is efficiently collected in the normal direction of the light emitting surface 35a, the front luminance is dramatically improved.
Japanese Patent No. 3151830 “IDW'02”, 2002, p. 509-512

  However, in a conventional surface light source device having high front luminance, the light source must be a point light source because the light source must be arranged at the center of a circle drawn by the prism. When the light source deviates from the center of the circle, the light is emitted out of the normal direction of the light emitting surface 35a, and thus the emitted light cannot be efficiently collected in the normal direction of the light emitting surface 35a. In addition, since the amount and angle at which the emitted light deviates from the normal direction of the light emitting surface 35a differs depending on the location within the light emitting surface of the light guide plate, the front luminance becomes uneven and the appearance is poor.

  A case where the light source is shifted from the center position of the circle drawn by the prism will be described with reference to FIG. FIG. 16 shows a top view of a conventional surface light source device having a high front luminance when two LEDs are arranged in parallel. In FIG. 16, the same parts as those in FIGS.

  Except for the shape of the light guide plate 35, the arrangement method of the prism 36, that is, the arrangement of the LEDs, the configuration is the same as that of the surface light source device shown in FIGS. In FIG. 16, the center of the circle drawn by the prism 36 is set at an intermediate position between the two LEDs 34 ′ and 34 ″. In FIG. 16, a large number of displays are omitted for the prism 36, and only one prism located at the center of the light guide plate 35 is shown as a representative example.

  If the light emitted from the two LEDs 34 ′ and 34 ″ is guided through the light guide plate 35 and enters the prism 36 at the center, the light is shifted by Δθ from the direction perpendicular to the longitudinal direction of the prism 36. As a result of being reflected by the prism 36, the light is emitted with a deviation of Δθ from the normal direction of the light emitting surface. On the other hand, when the light source is a point light source, that is, a single LED, light always enters the prism 36 from a direction orthogonal to the longitudinal direction of the prism 36, so that such a problem does not occur. The light exits in the normal direction of the light exit surface.

  FIG. 17 shows the relationship between the distance d between the centers of the LEDs 34 ′ and 34 ″ and Δθ. FIG. 17 shows the calculation result for the prism located at the center of the light guide plate. In a general surface-mount type LED, the lateral width is about 3.5 mm. Therefore, when the mounting margin is included, the distance d between the LED centers needs to be about 5 mm. Then, Δθ is about 4.8 ° from the graph of FIG. This means that light is emitted with a deviation of about 4.8 ° from the normal direction of the light emitting surface. As a result, the front luminance is lowered, and the light emitted from the LEDs 34 ′ and 34 ″ is divided into ± 4.8 °, resulting in an unnatural luminance characteristic emitted from the light guide plate.

  Moreover, the deviation | shift amount of this output angle changes also with the distance of LED and a prism, and the deviation | shift amount is so large that the light radiate | emitted from the prism near LED.

  Therefore, in the conventional surface light source device with high front luminance, only one LED can be used, and there is a limit even if light is collected to increase front luminance.

  In addition, in a surface light source device that is used by backlighting a liquid crystal display device that is viewed by a user in a direction inclined by a predetermined angle from the front, the luminance in a direction inclined by a predetermined angle from the front is improved instead of improving the front luminance. Is required.

  In view of the above problems, the present invention provides a surface light source device that can efficiently collect light in the front direction and improve front luminance even when a plurality of light sources are used, and a liquid crystal display device and a mobile device including the surface light source device. The purpose is to provide equipment. Further, in view of the above problems, the present invention efficiently collects light in a direction inclined at a predetermined angle from the front even when a plurality of light sources are used, and improves the luminance in the direction inclined at the predetermined angle from the front. An object of the present invention is to provide a surface light source device capable of realizing the above, a liquid crystal display device including the same, and a mobile device.

In order to achieve the above object, in the surface light source device according to the present invention, at least two point light sources, a reflection unit that is provided for each point light source and reflects light emitted from the point light source, and the reflection A light guide plate that internally propagates the light reflected by the means, and light that emits the light traveling inside the light guide plate to the outside in a predetermined direction from the light exit surface of the light guide plate at a plurality of locations by non-scattering reflection A position of a virtual image by the reflecting means of each of the point light sources substantially coincides when viewed from the normal direction of the light guide plate, and each reflecting surface of the light extracting means has the reflection of each of the point light sources. It is formed so as to extend in a direction orthogonal to the radial direction of the circle with the position of the virtual image by the means as the approximate center. The predetermined direction may be a normal direction of the light output surface of the light guide plate, or may be a direction inclined by a predetermined angle from the normal direction of the light output surface of the light guide plate.

  According to such a configuration, each reflection surface of the light extraction means includes a plurality of point light sources and extends in a direction orthogonal to the radial direction of a circle having substantially all the virtual images formed by the reflection means of each point light source. Therefore, the light emitted from the plurality of point light sources does not enter the reflecting surfaces of the light extraction means in different directions, but enters all the reflection surfaces of the light extraction means in the radial direction. The light is emitted from the light guide plate in a predetermined direction from the emission surface. As a result, the front luminance or the luminance in a direction inclined by a predetermined angle from the front can be improved, and a natural luminance characteristic can be obtained.

In order to achieve the above object, in the surface light source device according to the present invention, at least two ultraviolet light sources, a point light source that emits visible light by being excited by ultraviolet light emitted from the ultraviolet light source, and emits visible light; A wavelength converter, a light guide plate that introduces light emitted from the wavelength converter and travels inside, and light that travels inside the light guide plate is emitted from the light guide plate by non-scattering reflection at a plurality of locations. And a light extraction means for emitting the light from the surface to the outside in a predetermined direction. The light guide plate is in contact with one surface of the wavelength converter, and a reflective surface is formed on the surface of the wavelength converter that is not in contact with the light guide plate. The reflecting surfaces of the light extraction means are formed so as to extend in a direction orthogonal to the radial direction of a circle whose center is the wavelength converter. The predetermined direction may be a normal direction of the light output surface of the light guide plate, or may be a direction inclined by a predetermined angle from the normal direction of the light output surface of the light guide plate.

  According to such a configuration, each reflection surface of the light extraction means is formed so as to extend in a direction orthogonal to the radial direction of the circle centering on the wavelength converter, so that the wavelength converter has a plurality of ultraviolet light sources. Visible light emitted from the wavelength converter is incident on each reflecting surface of the light extraction means in the radial direction and emitted from the light guide plate in a predetermined direction from the light emitting surface. As a result, the front luminance or the luminance in a direction inclined by a predetermined angle from the front can be improved, and a natural luminance characteristic can be obtained.

  In order to achieve the above object, a surface light source device according to the present invention includes the surface light source device having any one of the above configurations as a backlight.

  In order to achieve the above object, a mobile device according to the present invention includes the liquid crystal display device having the above configuration.

  According to the present invention, it is possible to realize a surface light source device that can efficiently collect light in the front direction and improve front luminance even when a plurality of light sources are used, and a liquid crystal display device and a mobile device including the surface light source device. it can. In addition, according to the present invention, even if a plurality of light sources are used, a surface light source device capable of efficiently collecting light in a direction inclined at a predetermined angle from the front and improving luminance in a direction inclined at a predetermined angle from the front. In addition, a liquid crystal display device and a mobile device including the same can be realized.

  An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 to 6 and FIGS. 8 to 10 referred to below, the number of prisms is reduced for the sake of simplicity, but a larger number of prisms are formed on an actual light guide plate.

  First, a first embodiment of the present invention will be described. A perspective view of the surface light source device according to the first embodiment of the present invention is shown in FIG. 1, a top view of the surface light source device according to the first embodiment of the present invention is shown in FIG. 2, and AA sectional view of FIG. Is shown in FIG.

  The surface light source device according to the first embodiment of the present invention includes light sources 1 and 2 that are arranged in parallel in the thickness direction of the light guide plate 3 with light emitting surfaces aligned, and light emitted from the light sources 1 and 2 inside. And a prism 4 formed on a surface 3b of the light guide plate 3 facing the light exit surface 3a.

  In the present embodiment, LEDs having a sufficiently narrow width as compared with the width dimension of the light guide plate 3 are used for the light sources 1 and 2. Thereby, the light sources 1 and 2 become point light sources for the light guide plate 3. The bottom surface of the LED that is the light source 1 and the top surface of the LED that is the light source 2 are bonded together using an adhesive so that the positions of the two LEDs in the light guide plate thickness direction do not shift. The LED connection body thus obtained is arranged so that the light emitting surface is in close contact with the light incident surface 3 c of the light guide plate 3.

  The light guide plate 3 is made of a transparent material such as acrylic. In this embodiment, the light guide plate 3 is created by injection molding. The light guide plate 3 is a substantially rectangular flat plate, and a light incident surface 3c is formed at one corner. In addition, the thickness of the peripheral portion of the light emitting surface 3a is increased so that the light emitted from the two LEDs can be efficiently taken into the interior, and the thickness of other portions is decreased in order to reduce the thickness and weight. Furthermore, the region connecting the portions with different thicknesses of the light guide plate 3 has a shape that draws a gentle curve so as not to disturb the light guide. If there is no need to reduce the thickness and weight, the entire light guide plate 3 may be formed with a uniform thickness.

  In the present embodiment, the shape of the prism is created in advance in an injection mold, and the prism 4 is created simultaneously with the injection molding of the light guide plate 3. The prism may be formed on a transparent sheet, and the transparent sheet may be bonded to a light guide plate on which the prism is not formed via an adhesive.

  As shown in FIGS. 1 and 2, the reflecting surface of the prism 4 extends in the X direction orthogonal to the Y direction, which is the radial direction of the circle centered on the two LEDs that are the light sources 1 and 2. Is formed. In other words, the prism 4 is configured by a groove extending in the X direction. The angle of inclination of the reflecting surface of the prism 4 is defined so that the light guided while totally reflecting the light guide plate 3 is efficiently emitted in the normal direction of the light emitting surface 3a. In order to obtain in-plane uniformity of the light intensity, the distance between the adjacent prisms 4 decreases as the distance from the two LEDs, which are the light sources 1 and 2, as shown in FIGS. Designed to be

  In the surface light source device having such a configuration, the light emitted from the two LEDs, which are the light sources 1 and 2, and guided to the inside of the light guide plate 3 from the light incident surface 3c, repeats total internal reflection and repeats the inside of the light guide plate 3 To proceed. When the light inside the light guide plate 3 hits the reflecting surface of the prism 4, the light is reflected by the prism 4, and the reflected light is emitted from the light emitting surface 3a to the outside.

  The surface light source device according to the first embodiment of the present invention includes two light sources and extends in a direction orthogonal to the radial direction of a circle centered on the two LEDs that are the light sources 1 and 2. Since the reflecting surfaces of the prisms are formed, the light emitted from the two light sources does not enter the reflecting surfaces of the prisms in different directions but enter the reflecting surfaces of the prisms in the radial direction. The light is emitted from the light guide plate in the normal direction of the light emitting surface. Accordingly, it is possible to obtain approximately twice the front luminance as compared with the conventional surface light source device having a high front luminance shown in FIGS. 12 to 14 and obtain natural luminance characteristics.

  In this embodiment, two light sources are used. However, in principle, more light sources can be used, and the front luminance is improved by the number of the arranged light sources.

  In addition, as in the present embodiment, it is desirable that the plurality of light sources coincide completely when viewed from the normal direction of the light guide plate, but the plurality of light sources may be arranged slightly deviated. The amount of deviation seen from the normal direction of the light guide plate is preferably within ± 1.5 mm in consideration of the half-value width of the emitted light.

  In the present embodiment, the angle of the reflecting surface of the prism 4 is defined so that light guided inside the light guide plate 3 is emitted in the normal direction of the light emitting surface 3a. However, the present invention is not limited to this. In other words, it may be designed such that light is emitted at a predetermined angle from the normal direction of the light exit surface 3a.

  Next, a second embodiment of the present invention will be described. FIG. 4 shows a perspective view of a surface light source device according to the second embodiment of the present invention, FIG. 5 shows a top view of the surface light source device according to the second embodiment of the present invention, and FIG. Is shown in FIG. Moreover, the virtual image position of the light source which the surface light source device which concerns on 2nd embodiment of this invention comprises is shown in FIG.

  The surface light source device according to the second embodiment of the present invention includes light sources 11 and 12 arranged side by side above the light guide plate 13, and a light guide plate that guides light emitted from the light sources 11 and 12 inside. 13 and a prism 14 formed on a surface 13b of the light guide plate 13 facing the light exit surface 13a.

  The light guide plate 13 is made of a transparent material such as acrylic. In the present embodiment, the light guide plate 13 is created by injection molding. The light guide plate 13 is a substantially rectangular flat plate and has a side surface 13d having an angle of 112.5 ° with the short side surface 13f and a side surface 13e having an angle of 112.5 ° with the long side surface 13g. Is formed. Then, the side surfaces 13d and 13e are made reflective surfaces. As a method of making the side surfaces 13d and 13e reflective surfaces, for example, a method of depositing a metal thin film on the side surfaces 13d and 13e can be mentioned.

  In this embodiment, the shape of the prism is created in advance in an injection mold, and the prism 14 is created simultaneously with the injection molding of the light guide plate 13. The prism may be formed on a transparent sheet, and the transparent sheet may be bonded to a light guide plate on which the prism is not formed via an adhesive.

  In the present embodiment, LEDs having a sufficiently narrow width as compared with the width dimension of the light guide plate 13 are used for the light sources 11 and 12. Thereby, the light sources 11 and 12 become point light sources for the light guide plate 13. The position of the virtual image 11 ′ (see FIG. 7) of the light source 11 by the side surface 13d which is the reflecting surface and the position of the virtual image 12 ′ (see FIG. 7) of the light source 12 by the side surface 13e which is the reflecting surface are the method of the light guide plate 13. The LED that is the light source 11 and the LED that is the light source 12 are fixed on the light emitting surface 13a of the light guide plate 13 via an adhesive so as to substantially match when viewed from the line direction.

  As shown in FIGS. 5 and 7, the reflecting surface of the prism 14 is in the X direction orthogonal to the Y direction, which is the radial direction of a circle centered on the virtual image 11 ′ of the light source 11 and the virtual image 12 ′ of the light source 12. It is formed to extend. In other words, the prism 14 is configured by a groove extending in the X direction. The angle of inclination of the reflecting surface of the prism 14 is defined so that the light guided while totally reflecting inside the light guide plate 13 is efficiently emitted in the normal direction of the light emitting surface 13a. In order to obtain in-plane uniformity of the light intensity, the distance between the adjacent prisms 14 decreases as the distance from the two LEDs, which are the light sources 11 and 12, as shown in FIGS. Designed to be

  The surface light source device according to the second embodiment of the present invention includes two light sources and extends in a direction orthogonal to the radial direction of a circle centered on the virtual image of the light source 11 and the virtual image of the light source 12. Since the reflecting surface of each prism is formed, the light emitted from the two light sources does not enter the reflecting surface of each prism in different directions, and enters the reflecting surface of each prism in the radial direction, The light is emitted from the light guide plate in the normal direction of the light emitting surface. Accordingly, it is possible to obtain approximately twice the front luminance as compared with the conventional surface light source device having a high front luminance shown in FIGS. 11 to 13, and to obtain a natural luminance characteristic.

  In this embodiment, two light sources are used. However, in principle, more light sources can be used, and the front luminance is improved by the number of the arranged light sources.

  In addition, it is desirable that the virtual images of the plurality of light sources completely coincide with each other when viewed from the normal direction of the light guide plate, but the plurality of light sources may be arranged slightly deviated. The amount of deviation seen from the normal direction of the light guide plate is preferably within ± 1.5 mm in consideration of the half-value width of the emitted light.

  In the present embodiment, the light source is disposed on the upper surface of the light guide plate. However, the light source may be enclosed in the light guide plate or may be disposed on the lower surface of the light guide plate.

  In the present embodiment, the angle of the reflecting surface of the prism 14 is defined so that light guided inside the light guide plate 13 is emitted in the normal direction of the light emitting surface 13a. However, the present invention is not limited to this. In other words, it may be designed such that light is emitted at a predetermined angle from the normal direction of the light emitting surface 13a.

  Next, a third embodiment of the present invention will be described. FIG. 8 shows a perspective view of the surface light source device according to the third embodiment of the present invention, FIG. 9 shows a top view of the surface light source device according to the third embodiment of the present invention, and FIG. Is shown in FIG.

  The surface light source device according to the third embodiment of the present invention has ultraviolet light sources 21 and 22 disposed adjacent to the phosphor 25, and a wavelength that emits visible light when excited by ultraviolet light emitted from the ultraviolet light sources 21 and 22. A phosphor 25 serving as a converter, a light guide plate 23 in which the phosphor 25 is disposed on the light incident surface 23c and confining visible light emitted from the phosphor 25, and a light emitting surface of the light guide plate 23 And a prism 24 formed on a surface 23b facing the surface 23a. Here, the ultraviolet light source refers to a light source that mainly emits light having a wavelength of 400 nm or less.

  In this embodiment, a red-emitting phosphor (P22-RE3 manufactured by Kasei Optonics), a green-emitting phosphor (LP-G3 manufactured by Kasei Optonics), and a blue-emitting phosphor (produced by Kasei Optonics) LP-B4) is mixed in appropriate amounts to produce a phosphor having a white luminescent color, and the produced phosphor is applied to the light incident surface 23c of the light guide plate 23 so as to have a width of about 3 mm. A body 25 is formed. By making the width of the phosphor 25 sufficiently narrow compared with the width dimension of the light guide plate 3, the phosphor 25 that emits visible light when excited by ultraviolet light becomes a point light source for the light guide plate 3. In addition, in order to make visible light emitted from the phosphor 25 efficiently enter the inside of the light guide plate 23, a reflective surface (for example, a metal thin film) may be formed on the surface of the phosphor 25 that is not in contact with the light guide plate 23. good.

  In the present embodiment, ultraviolet light emitting LEDs (NSHU550A manufactured by Nichia Corporation) are used for the ultraviolet light sources 21 and 22.

  The light guide plate 23 is made of a transparent material such as acrylic. In this embodiment, the light guide plate 23 is created by injection molding. The light guide plate 23 is a substantially rectangular flat plate, and a light incident surface 23c is formed at one corner.

  In the present embodiment, the shape of the prism is created in advance in an injection mold, and the prism 24 is created simultaneously with the injection molding of the light guide plate 23. The prism may be formed on a transparent sheet, and the transparent sheet may be bonded to a light guide plate on which the prism is not formed via an adhesive.

  As shown in FIGS. 8 and 9, the reflecting surface of the prism 24 is formed so as to extend in the X direction orthogonal to the Y direction, which is the radial direction of the circle centering on the phosphor 25. In other words, the prism 24 is configured by a groove extending in the X direction. Then, the angle of inclination of the reflecting surface of the prism 24 is defined so that the light guided while being totally reflected inside the light guide plate 23 is efficiently emitted in the normal direction of the light emitting surface 23a. In order to obtain the in-plane uniformity of the light intensity, the distance between the adjacent prisms 24 is designed to become shorter as the distance from the phosphor 25 increases as shown in FIGS.

  In the surface light source device having such a configuration, the light emitted from the phosphor 25 and guided to the inside of the light guide plate 23 from the light incident surface 23c travels inside the light guide plate 23 while repeating total reflection. Then, when the light inside the light guide plate 23 hits the reflecting surface of the prism 24, the light is reflected by the prism 24, and the reflected light is emitted from the light emitting surface 23a to the outside.

  According to the surface light source device according to the third embodiment of the present invention, the reflection of each prism so as to extend in a direction orthogonal to the radial direction of the circle centering on the phosphor 25 that emits visible light when excited by ultraviolet light. Since the surface is formed, even if ultraviolet light is emitted from the two ultraviolet light sources 21 and 22 to the phosphor 25, the visible light emitted from the phosphor 25 is incident on the reflecting surface of each prism in the radial direction, The light is emitted from the light guide plate in the normal direction of the light emitting surface. Accordingly, it is possible to obtain approximately twice the front luminance as compared with the conventional surface light source device having a high front luminance shown in FIGS. 12 to 14 and obtain natural luminance characteristics.

  In the present embodiment, two ultraviolet light sources are used. However, in principle, more ultraviolet light sources can be used, and the front luminance is improved by a factor of the number of arranged ultraviolet light sources.

  In addition, the emission color of the wavelength converter that emits visible light when excited by ultraviolet light is desirably white as in the present embodiment.

  In the present embodiment, the angle of the reflecting surface of the prism 24 is defined so that the light guided inside the light guide plate 23 is emitted in the normal direction of the light emitting surface 23a. However, the present invention is not limited to this. In other words, it may be designed such that light is emitted at a predetermined angle from the normal direction of the light emitting surface 23a.

  The above-described surface light source device according to the present invention is preferably used as a backlight of a liquid crystal display device, for example. The liquid crystal display device includes a liquid crystal display panel, a drive circuit that drives the liquid crystal display panel, and a backlight. Here, a configuration example of the liquid crystal display panel will be described. A liquid crystal display panel is obtained by applying an alignment film to an active matrix substrate, and laminating the liquid crystal between both substrates by laminating a transparent insulating counter substrate on which a transparent electrode, an alignment film, a color filter, and the like are disposed. In the active matrix substrate, a plurality of gate wirings and a plurality of source wirings are arranged on a transparent insulating substrate so as to be orthogonal to each other, and a switching element controlled by the drive circuit is formed at the intersection. A transparent electrode that covers a pixel region surrounded by the gate wiring and the source wiring is formed.

  In the liquid crystal display device using the surface light source device according to the present invention as a backlight, the direction of the emitted light from the surface light source device according to the present invention is changed between the surface light source device according to the present invention and the liquid crystal display panel. A prism sheet may be provided.

  The above-described liquid crystal display device according to the present invention may be mounted on a mobile device such as a mobile phone device or a PDA.

These are the perspective views of the surface light source device which concerns on 1st embodiment of this invention. These are top views of the surface light source device according to the first embodiment of the present invention. These are sectional drawings of the surface light source device concerning a first embodiment of the present invention. These are the perspective views of the surface light source device which concerns on 2nd embodiment of this invention. These are top views of the surface light source device according to the second embodiment of the present invention. These are sectional drawings of the surface light source device which concerns on 2nd embodiment of this invention. These are figures which show the virtual image position of the light source with which the surface light source device which concerns on 2nd embodiment of this invention comprises. These are the perspective views of the surface light source device which concerns on 3rd embodiment of this invention. These are top views of the surface light source device according to the third embodiment of the present invention. These are sectional drawings of the surface light source device which concerns on 3rd embodiment of this invention. These are the perspective views of the conventional surface light source device. These are perspective views of the conventional surface light source device with high front luminance. These are the top views of the conventional surface light source device with high front luminance. These are sectional drawings of the conventional surface light source device with high front luminance. These are figures which show the optical characteristic in the output surface of the conventional surface light source device with high front luminance. These are top views at the time of arrange | positioning two LED in parallel about the conventional surface light source device with high front luminance. These are figures which show the relationship between the distance between two LED centers, and the incident direction deviation | shift amount of prism incident light.

Explanation of symbols

1, 2, 11, 12 Light source 3, 13, 23 Light guide plate 4, 14, 24 Prism 21, 22 Ultraviolet light source 25 Phosphor

Claims (4)

  At least two point light sources;
  Reflecting means that is provided for each point light source and reflects light emitted from the point light source;
  A light guide plate that internally propagates the light reflected by the reflecting means;
  Light extraction means for emitting light traveling inside the light guide plate to the outside in a predetermined direction from the light exit surface of the light guide plate by non-scattering reflection at a plurality of locations;
The position of the virtual image by the reflecting means of each of the point light sources substantially coincides when viewed from the normal direction of the light guide plate,
  Each of the reflection surfaces of the light extraction means is formed so as to extend in a direction orthogonal to a radial direction of a circle having a substantially centered position of a virtual image by the reflection means of each of the point light sources. Light source device.   At least two ultraviolet light sources;
  A wavelength converter that is excited by ultraviolet light emitted from the ultraviolet light source, emits visible light, and becomes a point light source that emits visible light;
  A light guide plate that introduces light emitted from the wavelength converter and advances the light internally;
  Light extraction means for emitting light traveling inside the light guide plate to the outside in a predetermined direction from the light exit surface of the light guide plate by non-scattering reflection at a plurality of locations;
A reflective surface is formed on the surface of the wavelength converter that is not in contact with the light guide plate, and the light guide plate is in contact with one surface of the wavelength converter.
A surface light source device, wherein each reflection surface of the light extraction means is formed to extend in a direction orthogonal to a radial direction of a circle having the wavelength converter as a center.   A liquid crystal display device comprising the surface light source device according to claim 1 as a backlight. A mobile device comprising the liquid crystal display device according to claim 3.

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