JP2009230928A - Side edge type backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device which has a thinner incident end face of a light guide plate than a light emitting face of a light source in which a means to obtain a high light efficiency can be provided. <P>SOLUTION: The side edge type backlight device includes a light source, a light guide plate which makes light from the light source enter from an incident end face, and a reflection plate which is arranged at the back of the light guide plate, and has a relationship that the light emitting face of the light source is larger than the incident end face of the light guide plate. A nearby portion of the incident end face of the light guide plate is slanted and a slanted region is provided, and an air layer is provided between the rear face of the slanted region and the reflection plate, and part of the light emitting face of the light source and the incident end face of the light guide plate are made close-by, and the other part of the light emitting face of the light source is installed in the air layer. Thus, through the air layer, light is made to enter from the rear face of the slanted region of the light guide plate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight device used for a medium-sized, small-sized or portable liquid crystal screen.

  In recent years, there is an increasing need for thin liquid crystal screens used in mobile phones, portable electronic devices, and the like in order to improve convenience and design. As the structure of the backlight used for a thin liquid crystal screen such as a current cellular phone, a light source is disposed on the side surface of a transparent light guide plate, and the light emitted from the light source is guided while being repeatedly reflected in the light guide plate, that is, A so-called side-edge type backlight that is guided and emits light through an optical film disposed on the surface of the light guide plate is increasing. Moreover, in order to reuse the light beam leaking to the back surface of the light guide plate, there is one in which a reflector (reflecting plate) is installed on the back side of the light guide plate. An example of such a technique is described in Patent Document 1.

  On the other hand, LEDs (light emitting diodes) that can be miniaturized are currently used as the light source of the backlight in order to reduce the size of the liquid crystal screen and the thickness of the backlight. As the thickness of the LED is reduced, the light emission efficiency is reduced, so that the thickness is currently 0.3 to 0.4 mm. On the other hand, the thickness of the light guide plate is gradually reduced by film processing.

  However, when the light emission surface of the light source> the thickness of the light incident end surface of the light guide plate, the light emitted from the light source cannot enter the light guide plate effectively. For example, as shown in FIG. 10, when only the conventional light guide plate 300 is thinned and the LED as the light source 2 is thicker than the light guide plate 300, the light beam 202 of a part 201 of the light emitting surface 200 of the light source 2 is guided. A phenomenon occurs in which only the end face of the optical film 4 is irradiated without being transmitted to the optical plate 300. Only the light beam 203 that has entered the light guide plate 300 is guided and then emitted as a backlight, which becomes light energy. Therefore, the backlight device is not a high-brightness backlight device because the light efficiency is greatly reduced.

  Therefore, in Patent Document 2, as a means for making the light source enter the light guide plate as much as possible, the light guide plate is expanded only in the vicinity of the light emission surface of the light source, and a trumpet-shaped enlarged portion or a tapered portion. Techniques for providing are shown.

JP 2000-222924 A JP 2003-121840 A

  However, as in Patent Document 2, if a tapered portion is provided that has a light incident end face of the light guide plate that is thickened according to the thickness of the light source and then has one end inclined to reduce the diameter, all light rays emitted from the light emitting face of the light source are provided. Although light can be directly incident only on the light incident end face of the light guide plate, the light is repeatedly reflected and propagated at a large incident angle at the reduced diameter portion where the inclination is provided, but most of the light leaks at the tapered portion. Therefore, it is known that the emitted light becomes very weak.

  For example, in the tapered structure 210 shown in FIG. 11, let us consider the amount of light 204 and 205 that passes through the large end surface 211 having a large area and the small end surface 212 having a small area. In a tapered optical system in which light from a diffused light source such as an LED passes, the ratio of the light amount 204 of the large end surface to the light amount 205 of the small end surface is (NA of the small end surface (numerical aperture) / large end surface). It is known to be the square of (NA). The ratio of NA is determined by the area. For example, when the area of the large end surface: small end surface is 4: 1, (NA of the small end surface (numerical aperture) / NA of the large end surface) = 1/4. In this case, the amount of light 204 on the large end face is (1/4) ^ 2 = 0.0625 with respect to the amount of light 205 on the small end face. That is, the large end surface 211 can accept only 6.25% of the amount of light that can pass through the small end surface 212, so that only 6.25% of the light beam tapers even when both end surfaces have the same area. You will not be able to pass through the structure. Thus, if the tapered portion is provided on the light guide plate, high light efficiency cannot be obtained after all.

  Further, as shown in FIG. 2 of Patent Document 2, when a reflective film is provided on the liquid crystal screen side of the inclined surface, that is, on the surface side, and light rays leaking from the surface are reflected in the light guide plate, depending on the inclination angle of the inclined surface, Since many of the light rays reflected by the reflective film are nearly perpendicular to the light guide plate, it is difficult to be guided in the horizontal direction and used. In order to avoid this, it is necessary to make the inclination angle of the inclined surface as small as possible. However, in this case, the inclined surface becomes long in the horizontal direction, and thus the backlight device cannot be reduced in size.

  In view of these problems in the prior art, the present inventor has found that the light efficiency can be increased in a backlight device in which the light incident end face of the light guide plate is thinner than the light exit face of the light source such as an LED. I have been eagerly researching about.

  In particular, a means for effectively using the light emitted from the light source as a backlight without providing an extended portion on the light guide plate has been desired. Therefore, by providing an inclined portion on the light guide plate and an air layer on the back thereof, a new technical idea is found in which light from the light source enters the light guide plate through the air layer without increasing the thickness of the light guide plate. As a result, the present invention has been completed.

  In order to solve the above problem, the side edge type backlight device according to the present invention employs the following means.

  That is, the side edge type backlight device according to the present invention includes a light source, a light guide plate that guides a light beam from the light source from a light incident end surface on a side surface, and an optical film disposed on a surface side of the light guide plate. And a reflecting plate disposed on the back side of the light guide plate, and in a side-edge type backlight device having a light emitting surface of the light source> the thickness of the light incident end surface of the light guide plate, the light incident end surface of the light guide plate Is inclined to provide an inclined region, an air layer is provided between the back surface of the inclined region and the reflecting plate, and a part of the light emitting surface of the light source is installed on the light incident end surface of the inclined region of the light guide plate. In addition, another part of the light emission surface of the light source is installed in the air layer, and light enters from the back side of the inclined region of the light guide plate through the air layer.

  In this side edge type backlight device, an air layer is provided by the inclined surface of the light guide plate and the reflecting plate, and the light emission surface of the light source is in contact with the light guide plate and the air layer. A light beam incident from the light incident end surface of the light guide plate is guided in a direction away from the light source while repeating reflection between the front surface side of the light guide plate and the back surface side thereof. Then, the light beam that has entered the air layer from the light source passes through the air layer, enters the light guide plate from the back side of the inclined region, and is guided through the light guide plate. The light beam guided through the light guide plate is emitted from the surface side of the light guide plate and used as backlight light.

  The side edge type backlight device according to the present invention is characterized in that the inclination angle of the inclined region of the light guide plate is 1 to 20 degrees.

  And in this side edge type backlight device, in addition to the light beam incident from the light incident end surface of the light guide plate, the light beam incident from the back side of the light guide plate via the air layer is all to the light guide plate. It has a small incident angle and is guided away from the light source.

  The side edge type backlight device according to the present invention is characterized in that the inclined region of the light guide plate is formed by bending the vicinity of the light incident end surface from a polymer resin film material.

  In this side-edge type backlight device, a film that can be easily and accurately formed and has a uniform thickness is used, and an inclined region is provided by bending the film.

Furthermore, the side edge type backlight device according to the present invention is formed from a UV curable resin.

  In the side edge type backlight device, a light guide plate having high transparency of the light guide plate, easy to mold, and excellent in optical characteristics is provided.

  Furthermore, the side edge type backlight device according to the present invention is characterized in that a reflective structure is provided on the surface side of the inclined region of the light guide plate.

  In this side-edge type backlight device, leakage light that is about to be emitted from the surface side of the inclined region of the light guide plate is reflected to the light guide plate side by the reflection structure, and is guided through the light guide plate.

  According to the side edge type backlight device of the present invention, in the side edge backlight device having a structure in which the light incident end face of the light guide plate is thinner than the light exit surface of the light source, the light incident on the light guide plate. In addition to entering the end face, the inclined area on the back side of the light guide plate can be used as the light entering area through the air layer, and the light efficiency from the light source can be maximized. Since the light guide plate and the air layer are in contact with the light incident end face of the light source and use light rays, it is not necessary to provide a large enlarged portion such as a taper on the light guide plate, there is no reduction in light efficiency in the light guide plate, and the light guide plate The light efficiency can be improved while the thickness is reduced.

  Moreover, according to the side edge type backlight device according to the present invention, a large number of light beams incident from both the light guide plate and the air layer can be effectively guided by the inclined region of 1 to 20 degrees.

  Moreover, according to the side edge type backlight device according to the present invention, it is possible to provide an optical device that requires high accuracy only by bending a light guide plate formed by polymer resin film molding. Further, it is a simple processing technique called bending, which can be manufactured in a continuous process, and a highly accurate light guide plate can be produced in large quantities and at low cost.

  In addition, according to the side edge type backlight device according to the present invention, molding is easy, and the manufacturing method and conditions can be selected from various methods for molding the transparent material and the backlight device member. In addition, because of its excellent hardness, it is possible to design and mold the reflective element including a fine structure, and to suppress light incident loss and light guide loss.

  Further, according to the side edge type backlight device according to the present invention, the leakage light in the inclined region of the light guide plate is guided back to the light guide plate and used as the backlight light, thereby suppressing the reduction in light efficiency. Can do. In addition, the leaked light is not reflected in a direction close to the vertical direction with respect to the light guide plate, but is guided in the horizontal direction through the inclined region, so that it is used as backlight light on the light guide plate. Cheap.

  Embodiment (1) of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of the main part of a side edge type backlight device according to the present embodiment (1), FIG. 2 is a perspective view of the main part of the side edge type backlight device according to the present embodiment (1), and FIG. It is a principal part schematic diagram which shows an effect | action of the side edge type | mold backlight apparatus of Embodiment (1).

  The backlight device 1 includes a light source 2, a light guide plate 3, an optical film 4, a reflection plate 5, and an air layer 6.

  As the light source 2, an LED (light emitting diode) that emits light to the light guide plate 3 is used, and the thickness of the light emitting surface 20 is not limited. However, if the thickness is 0.2 to 0.4 mm, the degree of thinning is reduced. It can be adopted according to. As the light emitting surface 20, a thickness of about 0.27 to 0.35 mm is preferably used as the cellular phone or the like becomes thinner. As the light source 2, a light source such as an organic EL can be used.

  In the light source 2, a part 21 of the light emitting surface 20 is arranged so that the light incident end surface 30 of the light guide plate 3 is in close contact, and the light incident end surface 30 is bent in a so-called “U” or “U” shape near the light incident end surface 30. An inclined region 31 that is inclined is provided. The light source 2 is arranged in such a manner that the other part 22 of the light emitting surface 20 is in close contact with the air layer 6 between the back side 33 of the inclined region 31 of the light guide plate 3 and the reflection plate 5.

  The light guide plate 3 includes the inclined region 31 and the planar region 32 described above. The optical film 4 is disposed on the surface 33 of the planar region 32, and the reflecting plate 5 is disposed on the back surface 34.

  Although the thickness t of the light guide plate 3 is thinner than the thickness T of the light emitting surface 20 of the light source 2, 30 to 75% of the thickness T of the light emitting surface 20 is from the reason of securing the optical film thickness space laminated on the upper surface. 50% to 70% is preferable.

  The inclined region 31 of the light guide plate 3 is a region in which only a nearby portion is inclined with a constant width in parallel along the light incident end face 30 and is bent with an inclination angle α with respect to the planar region 32. The inclination angle α may be about 1 to 20 degrees in order to reduce the incident angle of the air layer 6 or the inclined region 31 to the back side 33. When the inclination angle α is 1.2 to 3.0 degrees, the light beam incident from the back surface 33 of the inclined region 31 can be guided while being substantially totally reflected in the light guide plate 3.

  The width w of the inclined region 31 is determined according to the size of the backlight device from the design of the ratio of the thickness of the light source 2, the light guide plate 3, and the air layer 6 based on the inclination angle α. More preferably, it is desirable that the inclined region is in the range of an equation having an inclination length of about 20 to 40 times the thickness of the light entrance portion air layer. Within this range, a light beam incident from the back surface 33 of the inclined region 31 can be guided while being totally reflected in the light guide plate 3. As an example, the light source emission part is 280 microns, the inclination angle α = 1.6 degrees, the light guide plate thickness is 170 microns, the air layer thickness is 110 microns or less, and in this case, w is in the range of 2200 microns to 4400 microns. A design that falls within the range of 20 to 40 times the thickness can be realized.

  The light guide plate 3 is desirably formed of a material having a high refractive index and high transparency so that light can be guided. In particular, acrylic (PMMA) materials that are UV curable are particularly suitable because they can be accurately molded using UV curing and have high transparency. In the example shown in the figure, the light guide plate 3 is made of acrylic UV curable resin and has a thickness of 150 μm and an area substantially the same as the size of the screen that provides the backlight.

The air layer 6 is surrounded by the light emitting part 20 of the light source 2, the back side 33 of the inclined region 31 of the light guide plate 3, and the reflector 5, and has a wedge-shaped cross section. In the normal assembly and use situation of the apparatus, the air layer 6 is composed of the atmosphere. The air layer 6 is a layer where light rays that have not entered the light incident end surface 30 of the light guide plate 3 out of the light rays emitted from the other portion 22 of the light exit surface 20 are incident, and the refractive index is very low. Therefore, the incoming light beam goes straight with almost no interference or diffusion. Therefore, the light beam that has entered the air layer 6 enters the light guide plate 3 as it is from the back side 33 of the inclined region 31.
Although not shown in the drawing, the back surface side 33 of the inclined region 31 can be formed with a diffusing element that promotes light incident.

  The optical film 4 is a film disposed on the surface of the light guide plate 3 where light exits, and is used to uniformly emit backlight light. In the illustrated example, a diffusing film 40 for uniformizing the emitted light beam and prism films 41 and 42 for condensing the uniformed light are arranged.

  The reflection plate 5 is a reflection structure disposed on the back surface of the light guide plate 3 and has a reflector function of reflecting light rays in the direction of the light guide plate 3. In the example shown in the figure, a PET film with a silver thin film deposited on the back surface is used, and is arranged so as to be the lower end of the light exit surface 20 of the light source 2.

  Next, the operation of the backlight device of this embodiment (1) will be described. As shown in FIG. 3, the light beam 23 is directly incident on the light incident end face 30 of the light guide plate 3, repeatedly reflected in the light guide plate 3, guided in a direction away from the light source 2, and eventually the horizontal region 32. Is emitted in the backlight irradiation direction.

  On the other hand, the light beam 24 from the other part 22 of the light emitting surface 20 of the light source 2 does not enter the light incident end surface 30 of the light guide plate 3 immediately after emission, enters the air layer 6, and is inclined from the back side 33. The light is incident on the region 31, is guided while being repeatedly reflected between the surface 35 and the back surface 33 of the inclined region 31, is eventually guided to the horizontal region 32, and is emitted from the surface 36 of the light guide plate 3 in the backlight irradiation direction. Is done.

  The light beam 25 from the other part 22 of the light emitting surface 20 of the light source 2 enters the air layer 6 without entering the light guide plate 3, but is reflected by the reflecting plate 5, and the reflected light is reflected on the back side 33. The light enters the inclined region 31 and is guided in the same manner as the light beam 24.

  The light beams 23, 24, and 25 emitted in the backlight irradiation direction are deflected by the diffusion film 40 and the prism films 41 and 42, and all of them become light that is emitted vertically from the backlight structure, and serve as backlight light. Is done. Thus, it is possible to guide substantially the entire amount of light emitted from the light source 2 and use it as backlight light.

  Next, an embodiment (2) of the present invention will be described. FIG. 4 is a schematic view of the main part showing the side edge type backlight device of the present embodiment (2), FIG. 5 is a process diagram of the main part of the light guide plate manufacturing method in the present embodiment (2), and FIG. The principal part perspective view which shows shaping | molding by the 1st roll metal mold | die of this Embodiment (2), FIG. 7 is the principal part perspective view which shows shaping | molding by the 2nd roll metal mold | die of this Embodiment (2). In the second embodiment (2), the same reference numerals as those in the first embodiment (1) indicate the same configuration, and the duplicate description is omitted.

  In this embodiment (2), the light guide plate 3 is provided with a diffusing element 37 on the surface of the planar region 32 and a reflecting element 38 on the back surface. A reflecting plate 50 is provided on the surface 36 of the inclined region 31.

  The reflector 50 in the inclined region 31 is for reflecting the light beam leaking from the surface 35 of the inclined region 31 and guiding it to the flat region 32. The reflection plate 50 is disposed over the entire width w of the surface 35 of the inclined region 31.

  The reflective element 38 is thermoformed into a three-dimensional pattern, deflects light rays incident on the back surface 34, and helps guide the light inside the planar region 32. The reflective element 38 can have a function of adjusting the angle at the time of emitting and entering light with the reflective plate 5. As the shape, a mirror surface V-groove, a rough dot surface, or the like can be selected. In the example shown in the figure, with respect to the reflective element 38, in the case of the V groove, when the light guide plate thickness is 170 microns, the inclination angle is constant at 0.15 degrees, or near the light incident part is 0.1 degree and the anti-light incident part is 0. .V-groove modified to 3 degrees is processed.

  The diffusing element 37 is thermoformed into a three-dimensional pattern, and is provided in order to diffuse the light emitted from the planar region 32 to make the backlight light uniform together with the optical film 4. In the example shown in the figure, the diffusing element 37 has a pattern of diffusing 60 degrees in a direction parallel to the light incident surface and 1 degree in a direction perpendicular to the diffusing element 37.

  In this embodiment (2), there is no leakage from the surface 35 of the inclined region 31, it is not necessary to reduce the incident angle of the light beam to the inclined region 31, and the inclined angle α can be set large. Therefore, the width of the inclined region 31 can be reduced, which contributes to downsizing the backlight device.

  Next, the manufacturing method of the light-guide plate which concerns on this side edge type | mold backlight apparatus of this Embodiment (2) is demonstrated.

In the figure, 7 is a transparent base film to be supplied, 70 is a resin supply device, 71 is a feed roll, 8 is a first roll mold, 9 is a second roll mold, and the supply line is the first line. Only the main part is displayed, and the second line is the same except for the second roll mold, and is omitted.
The first roll mold 8 has a substantially cylindrical shape, and has bases 81, 81 at both ends having inclined region forming surfaces 82, 82 that are reduced in diameter toward the middle, and in the center of the inclined region forming surfaces 82, 82. Is formed by arranging a thin diffusion pattern forming surface 83. Positioning guide pins 84 project from the base 81. Further, the second roll mold 9 has substantially the same shape, the base portions 91, 91 at both ends are provided with inclined region molding surfaces 92, 92, and a reflection pattern molding surface 93 is arranged at the center. A guide pin 94 projects from the base 91.

  The base film 7 is fed through a feed roll 71 while being controlled in speed, and a UV curable resin is supplied from the resin supply device 70 to the entire surface of the film. The first roll mold 8 feeds the base film 7 with the positioning guide pins 84 and sandwiches it with the gap rolls 73, 73 with respect to the one surface, while making the UV curable resin the inclined region molding surfaces 82, 82 and the diffusion pattern molding surface. 83 and thermoformed into a substantially trapezoidal shape. At that time, since the UV irradiation device 72 passes through the base film 7 and irradiates the UV resin, the trapezoidal UV resin is thermally cured to form the diffusion pattern forming surface 76 and the inclined region forming surfaces 75 and 75. It becomes the light-guide plate shaping | molding die surface 74 which has.

  Next, the base film 7 is fed into the second line while having the light guide plate molding die surface 74, and UV resin is supplied from the resin supply device 70 onto the light guide plate molding die surface 74. The second roll mold 9 is sandwiched by the gap rolls 73 and 73 with respect to the UV resin on the light guide plate forming die surface 74 while feeding the base film 7 having the light guide plate forming die surface 74 with the positioning guide pins 94. The UV curable resin is thermoformed into a substantially trapezoidal shape with the inclined region forming surfaces 92 and 92 and the reflective pattern forming surface 93, and at the same time, the light guide plate forming die surface 74 is formed into a similar trapezoidal shape on the opposite surface. At that time, the UV irradiation device 72 has the inclined regions 31 and 31 at both ends in the width direction between the second roll mold 9 and the second molding die surface 74, and at the same time, the reflection element 38 at the intermediate portion. Since the planar region 32 including the diffusion element 37 is molded over the length direction, the light guide plate 3 is molded by peeling from the second molding die surface 37 by cutting from an intermediate portion or the like.

  According to the manufacturing method according to this embodiment (2), since the pattern of the roll mold rolls 8 and 9 can be accurately applied to the UV curable resin, the molding accuracy is high and the optical path is also accurately calculated. Can do. Further, the thickness control by the gap rolls 73 and 73 can accurately control the thickness with an accuracy of approximately 1 to 2 μm or less, and this high accuracy is indispensable for the accurate adjustment of the optical path in the backlight device. Is.

  Next, an embodiment (3) of the present invention will be described. FIG. 8 is a schematic view of a main part of a side edge type backlight device using the light guide plate of the present embodiment (3). In addition, description is abbreviate | omitted about the duplication part with Embodiment (1).

  In this embodiment (3), the inclined region 310 reverses the inclination direction from the embodiment (1). The inclined region 310 is inclined to the back side, and the air layer 6 is provided between the second reflecting plate 51 and the optical film 4 side. Therefore, in the inclined region 310, light from the air layer 6 is incident on the front side 311 and the third reflector 52 is disposed on the back side 312 as necessary. In this case, a reflection element may be provided on the back side 312.

  In this embodiment (3), the light incident from the light incident end face 30 of the light guide plate 3 and the light incident from the front side 311 through the air layer 6 are equivalent to the light incident from the embodiment (1). Is obtained.

  In this embodiment (3), since the light guide plate 3 can be disposed on the upper end side of the light emission surface of the light source 2, it can be selected according to the design of the backlight device 1.

  Hereinafter, the present invention will be described in more detail with reference to examples.

First, as the transparent base film 7, an easy-adhesive acrylic film (Mitsubishi Rayon, HBX777) having a thickness of 150 μm was used, and a UV curable resin was applied while feeding at a desired speed according to rules. The composition of the UV curable resin was a mixture of the following components.
Urethane oligomer (MW: 7000) 50% by weight
Tetraethylene glycol diacrylate bifunctional monomer (manufactured by Kyoeisha) 50% by weight
Photoinitiator: 1-hydroxycyclohexyl phenyl ketone (product name “Irgacure 184”, manufactured by Ciba Specialty Chemicals)
2% by weight

Subsequently, the UV curable resin on the base film 7 was pressed against the first roll mold 8 through the gap rolls 73 and 73. The first roll mold 8 has inclined region molding surfaces 82 and 82 having a width of 4,000 μm and an inclination angle of 1.6 degrees, and a diffusion pattern molding surface 83 is formed at a width of 150 mm in the middle portion. It was. The diffusion pattern was a pattern made by LSD (60 degrees X1 degrees) Physical Optics, and was a pattern that diffused 60 degrees in the direction parallel to the light incident surface and 1 degree in the direction perpendicular to it.

  Next, UV was irradiated using the UV irradiation apparatus 72 from the side which opposes the 1st roll metal mold | die 8 on the base film 7. FIG. The UV irradiation device 72 is a 160 W / cm type manufactured by Eye Graphics, and the distance to the base film 7 is 140 mm. The thickness of the UV curable resin was adjusted to 150 μm by the gap rolls 73 and 73. In this way, a double film in which the light guide plate molding die surface 74 made of the UV curable resin 11 was superimposed on the base film 7 was obtained.

  Next, as a 2nd process, the mold release agent was apply | coated to the base film 7, and it carried out like the 1st process except having used the 2nd roll metal mold | die 9. FIG. The second roll mold 9 has inclined region forming surfaces 92 and 92 having a width of 4,000 μm and an inclination angle of 1.6 degrees, and a diffusion pattern forming surface 93 is formed at a width of 150 mm at an intermediate portion. Using. The obtained light guide plate 3 was cut into display dimensions to obtain Example 1.

[Optical characteristics evaluation]
In order to confirm the effects of the present invention, optical characteristics were evaluated. As Test Example 1, a light guide plate 3 having a thickness of 170 μm and a size of 2 inches for Example 1 was prepared, and four LEDs (Nichia Chemical Co., NSCW215) were provided as light sources. The reflective film 5 is a silver-evaporated reflector film (Reiko, 75 W) on the back surface of the light guide plate. , 42 (manufactured by 3M, Tin-BEF) is arranged as a two-sheet structure in which prisms are orthogonal to each other.
External dimensions: Vertical 38mm x Horizontal 44mm
Light emitting part: Length 36 mm × width 42 mm

  Further, as Comparative Example 1, the light guide plate was assembled in the same manner as in Test Example 1 except that the same light guide plate as in Example 1 was used except that there was no inclination near the incident light and the thickness was constant at 170 μm.

FIG. 9 shows a comparison in luminance change between Test Example 1 and Comparative Example 1. A graph showing the relative luminance of Test Example 1 is A, and a graph showing the relative luminance of Comparative Example 1 is B. In Example 1, the relative average luminance was 2250 cd / m ² , that is, about (2250 ÷ 1650) −1 = 36% higher than that of Comparative Example 1. This test result shows that the side-edge type backlight device of the present invention has an effect of increasing the light energy toward the liquid crystal side. In other words, it has been demonstrated that by making the air layer with a predetermined inclination angle the difference between the LED light source light emitting part thickness and the general thickness of the light guide plate, light can be taken into the light guide plate and the light energy to the liquid crystal side can be increased. did it.

It is a principal part schematic diagram of the side edge type | mold backlight apparatus of this Embodiment (1). It is a principal part perspective view of the side edge type | mold backlight apparatus of this Embodiment (1). It is a principal part schematic diagram which shows an effect | action of the side edge type | mold backlight apparatus of this Embodiment (1). It is a principal part schematic diagram which shows the side edge type | mold backlight apparatus of this Embodiment (2). It is principal part process drawing of the manufacturing method of the light-guide plate in this Embodiment (2). It is a principal part perspective view which shows shaping | molding by the 1st roll metal mold | die of this Embodiment (2). It is a principal part perspective view which shows shaping | molding by the 2nd roll metal mold | die of this Embodiment (2). It is a principal part schematic diagram of the side edge type backlight apparatus using the light-guide plate of this Embodiment (3). It is a graph which shows the optical characteristic comparison of the test example 1 and comparative example 1 of this invention. In prior art, it is the schematic which shows the utilization efficiency of the light ray when a light-guide plate is thinner than a light source. It is the schematic which shows the quantity of the light ray in a taper structure in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight apparatus 2 Light source 3 Light guide plate 4 Optical film 5, 50 Reflector plate 6 Air layer 7 Base film 8 1st roll metal mold | die 9 2nd roll metal mold | die 20,200 Light emission surface 21, 201 A part of light emission surface 22 Other parts of light emitting surface 23, 24, 25 Light beam 30 Light incident end surface 31, 310 Inclined region 32 Planar region 33 Back surface 35 Surface of inclined region 36 Surface of light guide plate 37 Diffusing element 38 Reflecting element 40 Diffusing film 41, 42 Prism film 51 Second reflector 52 Third reflector 70 Resin supply device 71 Feed rolls 72 UV irradiation device 73 Gap roll 74 Light guide plate molding surface 75 Inclined area molding surface 76 Diffusion pattern molding surface 81, 91 Roll mold base 82, 92 Inclined area forming surface 83, 93 Diffusion pattern forming surface 84, 94 Positioning guide pin 202, 03 Light beam 204 Light amount of large end surface 205 Light amount of small end surface 210 Tapered structure 211 Large end surface 212 Small end surface 300 Conventional light guide plate 311 Front side 312 Rear side A Relative luminance of Test Example 1 B Relative luminance of Comparative Example 1 t Thickness of the light plate T Thickness of the light exit surface of the light source w Width of the inclined region α Inclination angle

Claims (5)

A light source, a light guide plate that guides light from a light source through a light incident end surface on a side surface, an optical film disposed on a front surface side of the light guide plate, and a reflector plate disposed on a back side of the light guide plate In the side edge type backlight device in which the light exit surface of the light source is greater than the thickness of the light incident end surface of the light guide plate,
An inclined region is provided by inclining the vicinity of the light incident end surface of the light guide plate, an air layer is provided between the back surface of the inclined region and the reflecting plate, and a part of the light emission surface of the light source is provided in the inclined region of the light guide plate. The side edge type back is characterized in that the other side of the light emitting surface of the light source is installed in the air layer and the light enters from the back side of the inclined region of the light guide plate through the air layer. Light equipment.   The side-edge type backlight device according to claim 1, wherein an inclination angle of the inclined region of the light guide plate is 1 to 20 degrees.   3. The side edge type backlight device according to claim 1, wherein the inclined region of the light guide plate is formed by bending a vicinity of the light incident end surface from a polymer resin film material.   The side-edge type backlight device according to any one of claims 1 to 3, wherein the light guide plate is formed from a UV curable resin.   The side edge type backlight device according to any one of claims 1 to 4, wherein a reflective structure is provided on the surface side of the inclined region of the light guide plate.

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