JP2005285390A - Lighting device and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the thickness of a sidelight type lighting device. <P>SOLUTION: The lighting device is composed of a light guide body having a light irradiation part irradiating light from a light source as illumination light, a light-incident body having a light-incident face on which the light from a light source is incident, and a light conducting part conducting the light to a light guide body. The light-incident body is formed so as to gradually reduce its thickness as it is headed from a light-incident side to a light conducting part side, and the light guide body composed of a pair of films is formed so as to interpose the light conducting part. Further, a light reflection layer is formed on the surface of the light-incident body, excluding the light-incident face, a light-emitting face, and a stepped part adjacent to the light-emitting face at its light source side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device used in a watch, a mobile phone, an audio, an electronic device, and the like, and a lighting device used in the display device.

  In recent years, liquid crystal display elements having a thin and light feature have been widely used in portable devices and the like. In particular, since a display device used in a mobile phone is required to be small and light, a liquid crystal display device is used in most mobile phones. However, since the liquid crystal display device is a light receiving type, there is a problem in visibility in a dark place required for a mobile phone. Therefore, an illuminating device is often installed on the front or back of the liquid crystal display device.

In order to realize this thin and light weight, a sidelight type lighting device in which an LED is arranged on the side surface of the light guide plate as a light source is often used (for example, see Patent Document 1).
Japanese Patent No. 3301752 (page 1 to page 3, FIG. 1)

  However, in the conventional sidelight type illumination device, if the thickness of the light guide plate is made thinner than the size of the LED light source, the light from the LED light source cannot be efficiently guided to the inside of the light guide plate. Had the problem of not being able to.

  The present invention employs a transparent light receiving body that is sequentially thinned from the light source side, and the light guide is configured to sandwich the light exit portion of the light incident body with a pair of transparent film substrates. The thickness of the light-emitting device is made to gradually decrease from the light incident surface side toward the light exiting portion side.

Furthermore, the light incident body was formed to be thin step by step from the light source side. Further, the height of the step portion adjacent to the light exiting portion on the light incident surface side was made substantially equal to the thickness per transparent film.
Furthermore, the tip of the light incident body opposite to the light incident surface is formed in a convex shape or a circular shape when viewed from the side surface.

  ADVANTAGE OF THE INVENTION According to this invention, the thin and lightweight illuminating device which has favorable brightness | luminance and brightness distribution can be provided. Furthermore, by setting the thickness of the light guide plate to about 200 μm or less, a flexible light guide plate can be obtained. Therefore, not only the display quality of the liquid crystal display device using the same is improved, but also the liquid crystal display device can be reduced in thickness and weight. Moreover, since it becomes a flexible light-guide plate by making film light-guide plate thickness into about 200 micrometers or less, even if the place which arrange | positions an illuminating device is a curved surface, it has an effect which can be applied. Moreover, it has the effect that it can utilize also as illumination apparatuses, such as a flexible film display apparatus using electrophoresis.

  The illumination device of the present invention includes a light source, a light guide having a light irradiation unit that emits light from the light source as illumination light, a light incident surface into which light from the light source enters, and a light transmission unit that transmits light to the light guide And a reflective structure provided on the back side of the light illuminating unit, and the thickness of the light incident member is sequentially reduced from the light incident surface side toward the light transmitting unit side, The light body is composed of a pair of transparent film substrates and is configured to sandwich the light transmitting portion.

  Furthermore, a light reflecting layer is formed on the surface of the light incident body excluding the light source side end surface (light incident surface), the light emitting surface (light transmitting portion), and the step adjacent to the light emitting surface on the light source side. Has been. And a pair of transparent films are mutually joined so that the light-projection surface of this light incident body may be clamped. This pair of transparent films is used as a light guide plate. A light reflecting layer is formed on three side surfaces excluding the light source side end surface and the upper and lower surfaces of these transparent films, and a reflecting structure is formed on the surface of the pair of transparent films opposite to the light illumination portion.

  With this configuration, light from the light source can be efficiently introduced into the film light guide plate, and the thickness of the light guide plate can be 1 mm or less.

  Hereinafter, an illumination device of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a cross-sectional view of the configuration of the film type illumination device of the present invention. The film-type illumination device of the present invention includes an LED light source 1 as a light source, a wedge-shaped light incident portion 2 and a pair of transparent films 3 and 4. The transparent films 3 and 4 form a film light guide plate that is a light illumination part of the light guide plate.

  The light emitted from the LED light source 1 is narrowed down by the wedge-shaped light incident part 2, guided in the transparent films 3 and 4, and is not shown from the upper surface side of the transparent film 3 that is the light irradiation surface of the illumination device. The object to be illuminated is irradiated uniformly in a planar shape. By using a liquid crystal display element as the object to be illuminated, a thin liquid crystal display device with uniform brightness and brightness can be obtained.

  Although only one is drawn in FIG. 1, a plurality of LED light sources 1 such as 3 to 5 are usually used. Although not shown, the light incident surface that is the light source side end surface of the wedge-shaped light incident portion 2 facing the LED light source 1 has an in-plane direction inside the wedge-shaped light incident portion 2 of the light emitted from the LED light source 1. A small prism is formed to control the spread angle. The microprism has a vertical ridgeline in the plane of FIG. 1, and the spread angle can be controlled by the apex angle and height of the microprism.

  The wedge-shaped light incident part 2 is stepped and has a plurality of steps, and is gradually thinner toward the light emitting end face. These step portions are formed with a substantially vertical angle. In order to make the figure easy to see, the case where the number of stages is two is shown here, but in reality, about 20 to 100 stages are formed.

  Further, a light reflecting layer is formed except for the end face on the light source side of the wedge-shaped light incident portion 2, the light exit end face, and the step adjacent to the light exit end face. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined.

  The transparent films 3 and 4 are made of a transparent polymer such as an acrylic resin, a polycarbonate resin, a polyethylene resin, or a cycloolefin resin. These transparent films are bonded to each other with an optical adhesive except for the end on the wedge-shaped light incident portion 2 side. These transparent films may be joined to each other by thermocompression bonding without using an optical adhesive. Further, the light source side end surfaces of the transparent films 3 and 4 are joined to the wedge-shaped light incident portion 2 while sandwiching the wedge-shaped light incident portion 2.

  A light reflecting layer 5 is formed on the side surfaces of the transparent films 3 and 4 except the light source side and the upper and lower surfaces. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined.

  A micro-reflection structure is formed on the surface of the transparent film 4 on which the transparent film 4 is not bonded. As the fine reflection structure, a fine prism group having a ridge line in a direction perpendicular to the paper surface of FIG. 1, a minute triangular prism group that is convex or concave toward the inside of the transparent film 4, or a texture structure is used. be able to. As a method for forming these fine reflective structures, a method can be used in which pressure is applied with a molding die on which a fine reflective structure pattern is formed in a state where the transparent film is heated to a softening point or higher.

  The number of times that the light guided inside the transparent films 3 and 4 is reflected on the surface of these films is about 10 times more than a normal light guide plate having a thickness of about 5 to 10 mm. The formation density of the fine reflective structures may be about 1/10 or less of the normal light guide plate.

  FIG. 2 is a cross-sectional view schematically showing an illumination device having another configuration. Here, the light reflection layer 6 is formed on the surface of the transparent film 4 on which the fine reflection structure is formed. In this way, by forming the light reflecting layer 6 on the surface of the transparent film 6, light that is about to escape to the back surface of the transparent film 4 is efficiently applied to the light irradiation surface, that is, the light irradiation surface that is the surface side of the transparent film 3. Can be returned. With such a structure, illumination efficiency can be improved while maintaining thinness and flexibility.

  Of course, in addition to the structure shown in FIG. 2, a reflecting plate may be arranged facing the transparent film 4 in the configuration shown in FIG. 1.

  FIG. 3 is a perspective view schematically showing a wedge-shaped light incident portion used in the illumination device of the present invention. The wedge-shaped light incident portion shown here has steps formed on both upper and lower surfaces, and has a wedge shape that becomes thinner from the incident end 10 toward the emission end 13. The height of the step 12 adjacent to the emission end 13 is formed to be approximately the same as the thickness of the transparent film. There is no restriction on the height of the other steps, for example, the step 11, but it is desirable to make the height of the steps as low as possible. Specifically, the height of each step can be arbitrarily set in the range of 50 to 1000 μm except for the step 12 adjacent to the emission end 13.

  FIG. 4 shows another configuration of the wedge-shaped light incident portion used in the illumination device. In this configuration, the step formed in the wedge-shaped light incident portion is only one side. With such a configuration, the length from the incident end 10 to the emission end 13 is longer than that shown in FIG. 3, but the wedge-shaped light incident portion and the bottom surface of the transparent film 4 can be made to coincide. In order to be able to do it, it has the advantage that it becomes easy to arrange lighting.

  FIG. 5 shows the behavior of light inside the wedge-shaped light incident portion 2 shown in FIG. Here, the light reflecting layer formed on the surface of the wedge-shaped light incident portion 2 is indicated by 13. In FIG. 5, the light emitted from the light source enters the wedge-shaped light incident portion 2 from the incident end face of the wedge-shaped light incident portion. First, the light indicated by the optical path 20 is reflected by the light reflecting layer 13 formed on the upper surface of the light incident portion and reaches the light emitting surface 12, and is on the side of the film light guide plate formed by the transparent films 3 and 4. To reach. On the other hand, the light indicated by the optical path 21 is reflected by the light reflecting layer 13 formed in the step portion and once returns to the light incident end face side, but is reflected again by the light incident end face and reaches the light emitting end face 12. As shown here, the wedge-shaped light incident part 2 used in the present invention is formed of a vertical stepped part, so that the side surface of the wedge-shaped light incident part 2 can be The angle of incidence on the top and bottom surfaces does not change. That is, it is possible to reach the light emitting end face without substantially changing the emission angle from the light source 1.

  If a wedge-shaped light incident portion having a normal smooth taper or a wedge-shaped light incident portion having a tapered step is used, the light reflected by the taper will eventually be more than the emission angle from the light source. Is equivalent to light having a large emission angle, and after entering the film light guide plate, it immediately leaks to the outside. Therefore, the formation density of the fine reflective structure changes with a higher order function as the distance from the light source increases. Thus, it is important that the illumination luminance distribution is not biased toward the light source.

  The light emitting end face 12 is formed in a circular and convex shape when viewed from the side. Therefore, the light emitted from the light emitting end face 12 is condensed and emitted in the vertical direction in FIG. By doing in this way, since the light incident angle to the film light-guide plate internal surface can be enlarged, the luminance distribution by a film light-guide plate can be improved more.

  Of course, even if the light emitting end face 12 is formed as a flat surface, as described above, since the emission angle from the light source is preserved and light is emitted, the guided light can be transmitted by total reflection inside the film light guide plate. it can.

  Further, the step portions 11a and 11b adjacent to the light emitting end face 12 have a height substantially equal to the thickness of the transparent films 3 and 4, respectively. Therefore, the light emitted to the outside from the step portions 11a and 11b is directly incident on the transparent films 3 and 4 from the end surfaces.

  Next, the behavior of light inside the film light guide plate will be described with reference to FIG. The optical path 23 is an example of an optical path of light incident from the end face of the transparent film 3. In FIG. 6, the light emitted from the step portion 11 a adjacent to the emission end surface 12 of the wedge-shaped light incident portion 2 enters the film from the end surface of the transparent film 3. Then, after guiding the inside of the transparent film 3, the portion after the joint between the transparent films 3 and 4 is repeatedly reflected between the surfaces of the transparent films 3 and 4 and guided. A fine reflection structure is formed on the surface of the transparent film 4, and the guided light incident on the fine reflection structure is deflected in the optical path and enters the surface of the transparent film 3 at an incident angle smaller than the critical angle. As shown in the result 23, the light is emitted from the surface of the transparent film 3 to irradiate the object to be illuminated. On the other hand, the light emitted from the emission end 12 enters the transparent film from the opposing surfaces of the transparent films 3 and 4 as indicated by the optical path 22. In the example shown in FIG. 6, the light enters the transparent film 4. This light is repeatedly reflected between the surfaces of the transparent films 3 and 4 in the same manner as the optical path shown at 23, and then enters the fine reflecting structure formed on the surface of the transparent film 4, so that the optical path is deflected and transparent. The light is emitted from the surface of the film 3.

  The fine reflecting structure formed on the surface of the transparent film 4 is formed densely with increasing distance from the light source side so that the brightness of the state from the surface of the transparent film 3 becomes uniform. In the above description, the example in which the fine reflective structure is formed on the back surface of the transparent film 4 has been described, but it goes without saying that the fine reflective structure may be formed on the top surface of the transparent film 3.

  In the following, more specific examples of the present invention will be described.

  A film type lighting apparatus having the structure shown in FIG. 1 was produced. A wedge-shaped light incident portion 2 having a thickness of 7 mm on the light source side and a width of 35 mm was molded from an acrylic resin. The thickness of the light exit end of the wedge-shaped light incident portion was 70 μm. Aluminum was vapor-deposited with a thickness of about 1 μm on the surface of the wedge-shaped light incident part excluding the light incident end face and the light exit end face. The height of each step portion of the wedge-shaped light incident portion was 80 μm, and the number of steps was 76 steps in total.

  As the transparent films 3 and 4, acrylic films having a width of 35 mm, a length of 40 mm, and a thickness of 90 μm were used. An aluminum light reflecting layer of about 1 μm was formed on the three side surfaces of these transparent films excluding the light source side by vapor deposition. On the back surface of the transparent film 4, convex fine triangular prisms were scattered and formed in a film having a height of 5 μm, a base angle on the light source side of 30 degrees, and a base angle on the opposite side of the light source of 80 degrees. The formation density was such that the bottom area of the fine triangular prism was proportional to the square of the distance from the light source. Then, the transparent films 3 and 4 were bonded by thermocompression bonding, and the end surface on one side was bonded to the wedge-shaped light incident portion with an acrylic adhesive.

  Three white LED light sources were used as the light source.

When the luminance of the lighting device thus manufactured was measured, a value of 1800 to 2200 cd / m ² was obtained, and performance equivalent to that of a normal sidelight type lighting device was obtained.

  Moreover, the thickness of the illumination part of the illumination device can be reduced to 180 μm, and if the curvature is small, it has been confirmed that the performance is not deteriorated even if it is bent.

  The film type lighting device shown in FIG. 2 was produced. However, the wedge-shaped light incident part 2 has the shape shown in FIG. As the transparent films 3 and 4, the same films as in Example 1 were used. However, a fine prism having a ridge line in the same direction as the light incident end was formed on the back surface of the transparent film 4. The prism had a height of 5 to 50 μm and an apex angle of 90 degrees. Also, the prism pitch and height were increased so that the prism surface area was proportional to the square of the distance from the light source.

  Instead of the light reflecting layer 6, an aluminum plate having a reflecting surface as a mirror surface was used. Further, three white LED light sources were used as the light source.

When the luminance of this film type illumination device was measured, a luminance of 1500 to 1800 Cd / m ² was obtained.

  Further, even when the produced film type lighting device was bent, the same luminance as that obtained when the film type lighting device was not bent as long as the curvature was small was obtained.

It is sectional drawing which shows the film type illuminating device by this invention typically. It is sectional drawing which shows the film type illuminating device by this invention typically. It is a perspective view which shows typically the wedge-shaped light-incidence part used for the film type illuminating device by this invention. It is a perspective view which shows typically the wedge-shaped light-incidence part used for the film type illuminating device by this invention. It is sectional drawing which shows typically an example of the optical path in a wedge-shaped light incident part. It is sectional drawing which shows typically an example of the optical path in a transparent film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source 2 Wedge-shaped light incident part 3, 4 Transparent film 5, 6 Light reflection layer 10 Light incident end surface 11 Light output end surface

Claims (6)

  Light input comprising a light source, a light guide having a light irradiating unit that irradiates light from the light source as illumination light, a light incident surface into which light from the light source enters, and a light transmitting unit that transmits light to the light guide And a reflective structure provided on the back side of the light illuminating unit, and the thickness of the light incident body is sequentially reduced from the light incident surface side toward the light transmitting unit side, and The light guide is composed of a pair of transparent film substrates, and is provided so as to sandwich the light transmission part.   The film-type lighting device according to claim 1, wherein the light incident body is configured to be thin stepwise from the light source side.   The film-type lighting device according to claim 2, wherein a height of a step portion adjacent to the light transmitting portion on the light incident surface side is substantially equal to a thickness per pair of the transparent films.   The lighting device according to any one of claims 1 to 3, wherein a tip of the light incident body opposite to the light incident surface is formed in a convex shape when viewed from a side surface.   The lighting device according to claim 4, wherein the convex shape is a circular shape.   A display device comprising: the illumination device according to claim 1; and a non-self-luminous display element provided on a light irradiation surface side of the illumination device.

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