JP2011014412A - Lighting device and display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it hard to be visible on unevenness of incident light of a light guide body by using an optical film with a large haze value in the vicinity only of a point light source in an edge-light type lighting device using a point light source; and prevent a moire phenomenon generated in loading a liquid crystal panel.SOLUTION: A diffusion film 1 wherein the surface of a diffusion layer 12 is partially covered with a transparent resin 8 is arranged on the light guide body of the lighting device. The transparent resin 8 forms a plurality of dots, and these dots are arranged to enlarge their sizes as they are separated from the point light source.

Description

  The present invention relates to a lighting device and a display device used for an electronic device. In particular, the present invention relates to a lighting device such as a front light or a backlight that illuminates a non-self-luminous display element, and a liquid crystal display device used for a portable information device, a notebook PC, a mobile phone, a liquid crystal television, and the like.

  2. Description of the Related Art Conventionally, an edge light type illumination device is known in which light from a light source enters from a side surface of a light guide and is emitted from an upper surface of the light guide (hereinafter referred to as an emission surface). A point light source such as a light emitting diode (LED) is used as the light source, and a large number of grooves and dot patterns are formed on the back surface opposite to the exit surface (that is, the bottom surface of the light guide). In addition, a diffusion pattern having an effect of diffusing light is often formed on the exit surface. Further, a reflection sheet is disposed below the light guide. In addition, a configuration in which a diffusion sheet or a prism sheet is disposed on the light exit side of the light guide is the mainstream. A transparent resin such as polycarbonate (PC) or acrylic (PMMA) having a higher refractive index than air is used as the material of the light guide.

  In addition, in an edge light type illumination device using a line light source such as a cold cathode tube, a diffusion film on which gradation printing is applied is used in order to prevent bright lines generated in the vicinity of the line light source (for example, patent document) 1) and the use of a protective sheet in which the light diffusibility is partially changed (see, for example, Patent Document 2).

JP 2002-22909 A JP 2002-323607 A

  In the conventional lighting device, when an LED (light emitting diode) is used as a light source, unevenness (eyeball) of the light incident portion is likely to occur. In order to suppress unevenness, the shape of the light incident part and the prism of the light guide are devised, and a diffusion film with a large haze value is used.However, if unevenness is difficult to see, brightness tends to decrease. It was.

  If the haze value of the diffusion film is increased only in the vicinity of the LED, the luminance reduction can be reduced while making the unevenness difficult to see. As a method for producing such a diffusion film, a method of gradation printing a diffusion material is known. As a general gradation printing method, square dots and chain dots are known.

  FIG. 3 is an external view schematically showing a diffusion film used in a conventional lighting device. As shown in the enlarged portion in the figure, the diffusion film 1 is formed with a gradation pattern created by a printing method called a chain dot. Chain dots are a printing method in which so-called tone jumps are less likely to occur compared to square dots. The size of the dot 2 varies in the range of about 1 mm to 0.01 mm in diameter, and the dot pitch is about 0.4 mm to 0.8 mm. The dots 2 have a configuration in which a diffusing material is dispersed in a transparent resin. FIG. 4 is a photograph partially showing the diffusion pattern shown in FIG. A gradation-like diffusion pattern is formed by the dots 2.

  FIG. 5 is a diagram showing a cross-sectional configuration of the diffusion film 1 shown in FIG. 4 taken along the line AB. On the upper surface of the transparent base film 10, dots 2 in which a diffusing material 9 is dispersed in a resin layer 11 are arranged. The dots 2 are arranged so that the size decreases as they move away from the light source of the illumination device, and the haze value of the diffusion film 1 is controlled. That is, the conventional diffusion film 1 controls the haze value by changing the density of the diffusion material 9. However, when chain dot printing is used, as shown in FIG. 4, as the size of the dot 2 decreases, the area where the dot 2 does not exist extremely increases in the diffusion film 1, and the presence or absence of the diffusion pattern is clearly separated. . When the liquid crystal panel is arranged on the diffusion film in such an area, a large brightness and darkness occurs in each pixel in the liquid crystal panel, and moire occurs. Moreover, in the structure of the conventional diffusion film, it is difficult to optimize the diffusion material 9, and it is very difficult to print a small dot pattern of 50 μm or less.

  Accordingly, an object of the present invention is to realize an illuminating device and a display device that reduce unevenness of a light incident portion and that hardly cause moire even when a liquid crystal panel is mounted without reducing the light use efficiency. And

  In order to solve the above problems, a diffusion film is disposed on the light exit surface of the light guide, and the transparent resin is partially provided on the surface of the diffusion layer of the diffusion film. Thereby, the diffusion of light can be controlled in the region where the transparent resin is provided. Further, the transparent resin forms a plurality of dots, and the plurality of dots are arranged so that the size increases as the distance from the light source increases.

  Alternatively, the transparent resin is intensively arranged near the light source.

  Further, the display device of the present invention has a configuration in which a non-self-luminous display element is disposed on the lighting device having any one of the above-described configurations.

  According to the present invention, high luminance can be maintained while reducing luminance unevenness in the vicinity of the light incident portion of the light guide. In addition, a lighting device and a display device with high luminance and little luminance unevenness can be realized at low cost.

It is a schematic diagram which shows the cross-sectional structure of the diffusion film used for the illuminating device of this invention. It is an external view which shows typically the diffusion film used for the illuminating device of this invention. It is an external view which shows typically the diffusion film used for the conventional illuminating device. It is a photograph of the diffusion pattern of the conventional diffusion film. It is sectional drawing which shows the structure of the conventional diffusion film typically. It is sectional drawing which shows the structure of the illuminating device of this invention. It is an external view which shows typically the diffusion film used for the illuminating device of this invention. It is an external view which shows typically the diffusion film used for the illuminating device of this invention. It is sectional drawing which shows the structure of the display apparatus of this invention.

  In the illumination device of the present invention, a diffusion layer is provided on the exit surface of a light guide that guides and emits light from a light source, and a transparent resin is partially disposed on the surface of the diffusion layer. With such a configuration, the diffusion layer can reduce the diffusion of light and reduce the haze value in the region where the transparent resin is provided. The diffusion layer is provided by disposing a film having a diffusion function on the exit surface of the light guide. Or it is good also as a structure which forms a diffusion surface in the upper surface of a light guide, and a transparent resin is partially arrange | positioned on this diffusion surface.

  Further, the transparent resin forms a plurality of dots, and the plurality of dots are arranged so that the size increases stepwise or continuously as the distance from the light source increases. Specifically, a plurality of dots are arranged in a gradation by an inkjet method or gravure printing, and the smallest dot has a diameter of 20 μm or less.

  Alternatively, the transparent resin is intensively arranged near the light source. At this time, the shape of the transparent resin may not be dots.

  Furthermore, the film disposed on the light exit surface of the light guide is composed of a transparent base film and a diffusion layer in which a diffusion material is dispersed in a resin formed on the base film. At this time, the composition of the resin forming the diffusion layer and the transparent resin may be the same.

With the above-described configuration, it is possible to make it difficult to see the light incident unevenness of the light guide in the lighting device, and it is possible to prevent moire that has occurred when the liquid crystal panel is mounted.

  The diffusion film 1 according to this embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the configuration of the diffusion film 1. On the upper surface of the transparent base film 10, a diffusion layer 12 composed of a resin layer 11 in which a diffusion material 9 is dispersed is formed. In this embodiment, the diffusing material 9 is uniformly dispersed in the resin layer 11. A material such as silica or acrylic beads having a diameter of about 1 to 200 μm is used for the diffusing material 9. The transparent base film 10 is formed of PET, acrylic, or the like, and has a thickness of approximately 12 μm to 300 μm. A small amount of beads may be printed on the surface opposite to the surface on which the diffusion layer 12 is provided to prevent sticking. The diffusion layer 12 can be printed by a roll-to-roll using a coater. Further, a transparent resin 8 made of a material such as acrylic or epoxy resin is partially disposed on the upper surface of the diffusion layer 12 to constitute the diffusion film 1.

  Generally, in a diffusion film having a structure in which a diffusion material is dispersed in a resin layer, the diffusion material protrudes in a dome shape on the surface of the film. The diffusing material protruding in a dome shape exhibits a lens effect due to a difference in refractive index from air and diffuses light. In this embodiment, the transparent resin 8 is partially provided on the surface of the diffusion layer 12 composed of the resin layer 11 in which the diffusion material 9 is dispersed. With such a configuration, the protruding diffusion material 9 is covered with the transparent resin 8, and the diffusion of light can be reduced in the area of the diffusion film 1 where the transparent resin 8 is provided.

  FIG. 2 is an external view schematically showing the diffusion film 1 of this example. The dot-shaped transparent resin 8 is arranged in a gradation and printed on the diffusion layer. The smallest dot size of the transparent resin 8 is 20 μm or less. The transparent resin 8 is arranged so that the size of the dots increases as the distance from the light source side increases when the diffusion film 1 is disposed in the lighting device. With such an arrangement, the diffusion film 1 is controlled such that the haze value is high in an area close to the light source of the lighting device, and the haze value decreases as the distance from the light source increases.

  The transparent resin 8 can be formed in a gradation on the diffusion layer by using silk screen printing using a mask, gravure printing, offset printing, an inkjet method, or the like. When an ink jet method or gravure printing is used, the thickness of the transparent resin 8 can be partially controlled, and a finer gradation can be expressed.

  Although not shown, the end surface of the transparent resin 8 formed on the diffusion layer 12 is actually rounded due to surface tension, so that the boundary between the diffusion layer 12 and the transparent resin 8 becomes inconspicuous.

  By partially forming the transparent resin using such a printing method, it becomes possible to reduce the dot size of the transparent resin or change the thickness of the transparent resin, and control the diffusion of light. The haze value of the film can be changed.

  Further, the transparent resin 8 is better as the visible light transmittance is higher. The materials used for the resin layer 11 and the transparent resin 8 are better in optical and physical (reliability) when the composition is closer. Further, the curing system of these resin materials may be heat, ultraviolet light, or a mixed type, but in general, a volatile resin material by heat is used.

  When the haze value of the diffusion film 1 is controlled by providing the transparent resin 8 on the diffusion layer 12 as in this example, the haze value of the diffusion layer 12 should be higher. In general, a diffusion film having a high haze value is more demanding than a diffusion film having a low haze value, so that the price is low. Moreover, according to the structure of a present Example, since it is not necessary to add a diffusing material further to the conventional diffusion film, cost can be reduced.

  An illumination device according to this embodiment will be described with reference to the drawings. FIG. 6 is a cross-sectional view schematically showing the configuration of the illumination device according to this embodiment. In the illuminating device shown in FIG. 6, the light guide 4 is disposed facing the light source 3, and a reflective structure such as a prism or a dot is formed on the lower surface of the light guide 4. The light that has entered the light guide 4 exits from the exit surface of the light guide 4 by striking the reflection structure while guiding the light. A reflective film 6 is disposed on the surface (lower surface side) opposite to the light exit surface of the light guide 4 to improve the light output efficiency. In many cases, the reflective film 6 is a type in which silver or aluminum is deposited on a transparent film such as PET, a white PET type, ESR manufactured by Sumitomo 3M, or the like. In addition, a frame 5 is provided to mechanically support the light source 3, the light guide 4, and the reflective film 6, prevent leakage light, and improve light utilization efficiency. The reflective film 6 is disposed on the frame 5, and the light guide 4 is disposed on the surface facing the reflective surface of the reflective film 6. The frame 5 is often a resin molded product such as white polycarbonate. In many cases, the frame 6 is further covered with a metal frame such as aluminum. The diffusion film 1 described in Example 1 is disposed on the light exit surface of the light guide 4. On the diffusion film 1, dots formed of the transparent resin 8 are gradation printed. There are almost no dots in the area close to the light source 3, and the number of dots gradually increases or the dot size increases as the distance from the light source 3 increases. With such an arrangement, it is possible to maintain the luminance efficiency of the entire lighting device while reducing unevenness near the light incident portion. Further, on the diffusion film 1, one or more prism sheets called BEF made by Sumitomo 3M or diamond art made by Mitsubishi Rayon are often arranged. Or you may arrange | position the diffusion film 1 on a prism sheet.

  Moreover, a diffusion surface may be formed by roughening the surface of the light guide 4 or by directly printing resin beads. In such a case, it is possible to control the diffusion of light by partially providing a transparent resin on the diffusion surface. If a diffusion surface is provided, the diffusion film may be omitted.

  The illumination device of the present embodiment is the same as the second embodiment in other configurations, although the pattern printed by the transparent resin is different from the second embodiment. FIG. 7 is an external view schematically showing the diffusion film 1 used in this example. In the diffusion film 1 of this embodiment, the transparent resin 8 is provided only in the vicinity of the light source 3. In general, in a lighting device, when bright unevenness called an eyeball or a hot spot occurs in the vicinity of the light source 3, the eyeball may be more easily seen by increasing the haze near the light source. In such a case, it is necessary to lower the luminance near the light source 3. By providing the transparent resin 8 only in the vicinity of the light source 3, the diffusion of light is controlled and it becomes difficult for the light to be emitted, and the eyeballs generated in the vicinity of the light source 3 can be reduced.

  FIG. 8 is an external view schematically showing the diffusion film 1 used in the illumination device of this example. The illumination device of the fourth embodiment is the same as the second embodiment except for the pattern printed by the transparent resin. In this example, the transparent resin layer 8 was printed with a heart pattern. When the diffusion film 1 is arranged on the light guide, light is not easily diffused in the printed portion of the transparent resin, so that contrast with other areas is generated, and the heart mark can be recognized when the light source is turned on. A method of arranging a film formed with an ink pattern on a light guide so as to make the pattern visible is conventionally known. According to the configuration of the present embodiment, the pattern can be visually recognized by controlling the diffusion of light, and a visual expression different from the conventional one can be realized. For example, when a highly transparent light guide is used in a lighting device, a heart pattern can be recognized only from a certain angle, and the other side can be seen through at other angles. In the present embodiment, the pattern is a heart mark, but other patterns, characters, and symbols can be expressed.

  FIG. 9 schematically shows a cross-sectional configuration of the display device of this example. A liquid crystal panel 7 was disposed on the illumination device of FIG. Light from the light source 3 enters the light guide 4 and is emitted from the exit surface by the lower prism provided on the light guide 4 to illuminate the liquid crystal panel 7 through the diffusion film 1. By covering the light guide 4 with the frame 5, a high-brightness liquid crystal display can be realized. Here, the diffusion film 1 described in Example 1 is used. A transparent resin is printed on the diffusion film 1 in a gradation with a size and pitch smaller than the dots of the liquid crystal panel 7. Thereby, it is possible to control the diffusion of light with finer gradation, and it is possible to prevent moiré that occurs in the display device by preventing diffusion unevenness.

  In each of the above-described embodiments, a point light source is used as a light source, and a side view type white LED is assumed. However, a top view, a bullet type, or a color other than white may be used. As the light guide, a molded product of transparent resin such as ZEONOR, PMMA, or PC can be used.

  The lighting device and the display device according to the present invention can be applied to display devices such as mobile phones, PDAs, car navigation systems, and televisions, amusements, and design lighting devices.

DESCRIPTION OF SYMBOLS 1 Diffusion film 2 Dot 3 Light source 4 Light guide 5 Frame 6 Reflective film 7 Liquid crystal panel 8 Transparent resin 9 Diffusing material 10 Transparent base film 11 Resin layer 12 Diffusion layer

Claims (9)

A light source;
A light guide that enters the light from the light source from the side surface and emits the light from the upper surface;
A film disposed on the light exit surface of the light guide,
The film has a diffusion layer, and a transparent resin is partially provided on the upper surface of the diffusion layer.   The lighting device according to claim 1, wherein the transparent resin forms a plurality of dots, and the plurality of dots are arranged so as to increase with distance from the light source side edge.   The illumination device according to claim 2, wherein a minimum diameter of the dots is 20 μm or less.   The lighting device according to claim 1, wherein the transparent resin is formed in the vicinity of the light source. The film is composed of a transparent base film and the diffusion layer in which a diffusion material is dispersed in a resin layer formed on the base film,
The lighting device according to any one of claims 1 to 4, wherein the resin layer and the transparent resin have the same composition.   The lighting device according to claim 5, wherein the composition of the transparent resin is an acrylic resin. A light source;
A light guide that enters the light from the light source from the side surface and emits the light from the upper surface;
A non-self-luminous display element disposed on the exit surface of the light guide;
A diffusion film disposed between the light guide and the display element,
The diffusion film is composed of a transparent base film and a diffusion layer in which a diffusion material is dispersed in a resin layer formed on the base film,
A display device, wherein a transparent resin is partially provided on an upper surface of the diffusion layer.   The display device according to claim 7, wherein the transparent resin forms a plurality of dots, and the plurality of dots are arranged so as to increase with distance from the light source side edge.   The display device according to claim 7, wherein the transparent resin is formed in the vicinity of the light source.