JP2012243422A - Lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sidelight-type lighting system restraining a hot spot in the vicinity of a light-incident surface of a light-emitting surface part, and capable of carrying out local dimming.SOLUTION: The lighting system is provided with a light source group consisting of a plurality of point light sources, a light guide plate, a light diffusion member and a reflecting member. The light guide plate is equipped with a light emission surface part emitting incident light, a rear face part opposite to the light emission part, and a side surface part placed between the light emission surface part and the rear surface part, and having a light-incident surface part where the light emitted from the light source group is partly incident. The light emission part includes a first concavo-convex structure making a diffusion angle toward a normal line direction of the light-incident surface part against transmitted light smaller than a direction crossing the normal line direction. The light incident surface part includes a second concavo-convex structure making a diffusion angle toward a normal line direction of the light emission surface part against the transmitted light smaller than a direction crossing the normal line direction. The light diffusion member is arranged facing the rear surface part of the light guide plate, and the reflecting member is arranged facing a surface of the light diffusion member opposite to the light guide plate.

Description

  The present invention relates to a sidelight type illumination device.

  In a liquid crystal display device, since the liquid crystal display panel itself does not emit light, it is necessary to supply the liquid crystal display panel with light emitted from an illumination device having a planar light exit surface (hereinafter simply referred to as “illumination device”). There is. Such illumination devices are roughly classified into two types, a direct type and a side light type. The direct illumination device is an illumination device in which a light source is located on the back surface of the liquid crystal display panel, and is an illumination device that is excellent in light use efficiency. On the other hand, the sidelight type illumination device is an illumination device in which the light guide plate is located on the back surface of the liquid crystal display panel and the light source is located on the side surface of the light guide plate, and is an illumination device suitable for thinning.

  The light guide plate in the sidelight type illumination device has a light emitting surface portion from which incident light is emitted, a back surface portion facing the light emitting surface portion, and a side surface portion located between the light emitting surface portion and the back surface portion, A part of the side surface portion becomes a light incident surface portion. With this configuration, the light guide plate guides light incident from the light incident surface portion toward the opposite surface of the light incident surface portion by total reflection between the light emitting surface portion and the back surface portion, and light scattering provided on the back surface portion. It has the function of scattering from the pattern and emitting from the light exit surface. In addition, in the light guide plate, it is desired to emit light with substantially uniform intensity regardless of the position of the light emitting surface portion, and the arrangement of the above-described light scattering pattern size and density has been studied conventionally. Yes.

  According to this sidelight type illumination device, since the light source can be arranged on the side of the image display surface of the liquid crystal display panel, the liquid crystal display device can be thinned.

  However, in a sidelight type illumination device, when a point light source with high linearity of emitted light such as a light emitting diode is used as a light source, the projection part of the point light source has a bright spot in the area near the light incident surface part on the light emitting surface part. Luminance unevenness (hereinafter referred to as “hot spot”) in which the projection portion between the light sources becomes dark occurs (see FIG. 7). For this reason, the image display surface of the liquid crystal display device using the sidelight type illumination device needs to exclude the area near the light incident surface portion where the hot spot is generated from the light emitting surface portion, and the area where the hot spot is generated is reduced. A means to reduce it has been desired.

  As an example of such means, a groove is formed in the light incident surface portion of the light guide plate from the light exit surface portion toward the back surface portion to diffuse the incident light and guide light having a larger incident angle to the inside of the light guide plate. Thus, an illumination device with reduced hot spots has been proposed (see, for example, Patent Document 1).

  By the way, in a CRT display device that scans a phosphor surface with an electron gun and displays an image, each pixel on the image display surface emits light only for an instant for one frame, whereas in a liquid crystal display device, each pixel is lit by an illumination device. The light is emitted all the while. Therefore, in the liquid crystal display device, a decrease in contrast and blurring of moving images occur due to the afterglow characteristics of human eyes. As a countermeasure, the light exit surface portion of the light guide plate is divided into a plurality of parts, and only a part of the light exit surface portion of the light guide plate is caused to emit light by lighting only a part of the plurality of light sources. A technique for performing area control so as not to emit light, or a technique for adjusting the amount of light in each section (hereinafter referred to as “local dimming”) is known. In addition to improving the contrast of the display image described above, local dimming reduces power consumption and reduces the phenomenon (crosstalk) in which the right eye image and the left eye image can be seen simultaneously when displaying a 3D image. Is also a useful technique that can be used.

  In the liquid crystal display device using the sidelight type illumination device, in order to perform the above-mentioned local dimming, a plurality of light sources arranged in the vicinity of the light incident surface portion of the light guide plate are divided into two or more sections (for example, “upper half”, “ This is divided into two categories, “lower half”, and only necessary segments are lit. At this time, if the light emitted from the light source has diffusibility, the light exit surface portion and the back surface portion may be separated according to the critical angle of the material of the light guide plate in the sections other than the section where the light exit surface portion is desired to emit light. Light spreads in the range where total reflection continues between them. As a result, there is a problem that the section adjacent to the section where the light source is turned on also emits light.

  Therefore, as one form for realizing local dimming, there has been proposed an illumination device in which a light emitting area of a light emitting surface portion is divided into a plurality of strip-shaped areas (see, for example, Patent Document 2). Further, it has been proposed that a convex portion is provided on the incident surface portion of the light guide plate and a light source is disposed on the top thereof, and that a lenticular lens is disposed on the incident surface portion of the light guide plate and a light source is disposed at the focal position thereof. (Patent Document 3).

JP-A-10-293202 JP 2001-210122 A JP 2009-199927 A

  The present inventor has sought to obtain a sidelight type illumination device that achieves both hot spot suppression and local dimming. However, when the technique described in Patent Document 2 described above is used to perform local dimming, there is a concern that the number of assembling steps or the strength may be reduced because the light guide plate is divided. In addition, dark lines are generated in the divided portions. On the other hand, the technique described in Patent Document 3 provides an optical structure for condensing light on the incident surface portion, and is difficult to combine with an optical structure for diffusing light provided on the incident surface side to suppress hot spots. It is.

  Therefore, an object of the present invention is to provide a sidelight type illumination device capable of suppressing a hot spot in the vicinity of a light incident surface portion of a light emitting surface portion and capable of local dimming.

  In view of the above problems, as a result of studies by the present inventors, in the above-described illumination device, in order to prevent luminance unevenness in the vicinity of the light incident surface portion of the light exit surface portion of the light guide plate, the back surface portion of the light guide plate and the reflecting member In the meantime, it was found that providing a light diffusing member was effective, and the present invention was completed.

  The illuminating device of the present invention is an illuminating device including a light source group in which a plurality of point light sources are arranged, a light guide plate, a light diffusing member, and a reflecting member, and the light guide plate is light incident on the light guide plate. A light emitting surface portion that emits light, a back surface portion facing the light emitting surface portion, and a side surface portion located between the light emitting surface portion and the back surface portion, and the light source group in a part of the side surface portion A light incident surface portion on which light emitted from the light is incident, and a diffusion angle in a normal direction of the light incident surface portion with respect to transmitted light is made smaller than a direction orthogonal to the normal direction on the light output surface portion. A first concavo-convex structure imparting anisotropic diffusivity is formed, and the light incident surface portion has a diffusion angle in the normal direction of the light emitting surface portion with respect to the transmitted light, and a direction orthogonal to the normal direction. A second concavo-convex structure that imparts anisotropic diffusivity to be smaller is formed, and the front The light diffusing member is a flat plate member that diffuses and transmits incident light, and is disposed to face the back surface of the light guide plate. The reflecting member is a flat plate member having light reflectivity. The light diffusing member is disposed to face the surface opposite to the light guide plate.

  In the illumination device of the present invention, it is preferable that the light diffusion member is bonded to the back surface portion of the light guide plate.

  In the illuminating device of the present invention, it is preferable that the light diffusing member is integrally formed on the back surface portion of the light guide plate.

  In the illumination device of the present invention, the first concavo-convex structure includes at least one of a pitch in a normal direction of the light incident surface portion, a pitch in a direction orthogonal to the normal direction, a height, an arrangement, and a cross-sectional shape. It is preferred that the item is aperiodic.

  In the illuminating device of the present invention, it is preferable that a light scattering process is applied to the back surface portion of the light guide plate.

  In the illumination device of the present invention, the second concavo-convex structure includes at least one of a pitch in a normal direction of the light emitting surface portion, a pitch in a direction orthogonal to the normal direction, a height, an arrangement, and a cross-sectional shape. It is preferred that the item is aperiodic.

  In the illumination device of the present invention, it is preferable that the light diffusing member includes an additive that imparts light diffusibility to transmitted light inside.

  In the illuminating device of the present invention, it is preferable that the light diffusing member has a third uneven structure that imparts light diffusibility to transmitted light on at least one surface.

  In the illuminating device of the present invention, the third concavo-convex structure has an anisotropic diffusibility so that a diffusion angle in a normal direction of the light incident surface portion with respect to transmitted light is smaller than a direction orthogonal to the normal direction. Is preferably applied to the light diffusing member.

  In the illumination device of the present invention, the third uneven structure has a pitch in a normal direction of the light incident surface portion of the light guide plate, a pitch in a direction orthogonal to the normal direction, a height, an arrangement, and a cross-sectional shape. Of these, at least one item is preferably aperiodic.

  In the illumination device of the present invention, it is preferable that the first concavo-convex structure, the second concavo-convex structure, and the third concavo-convex structure are concavo-convex structures formed by interference exposure using a speckle pattern.

  According to the present invention, it is possible to provide a sidelight type illumination device that is less likely to have uneven brightness in the vicinity of the light incident surface portion of the light emitting surface portion and can be locally dimmed.

It is a schematic perspective view of the light-guide plate used with the illuminating device which concerns on embodiment of this invention. It is a schematic perspective view of the illuminating device which concerns on embodiment of this invention. It is an example of the schematic cross section of the 1st, 2nd, and 3rd uneven structure which the light-guide plate used with the illuminating device which concerns on embodiment of this invention has. It is an example of the cross-sectional shape of the 1st, 2nd, and 3rd uneven structure which the light-guide plate used with the illuminating device which concerns on embodiment of this invention has. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on Comparative Examples 1-3 and Example 1. FIG. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on Comparative Examples 1-3 and Example 2. FIG. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on Comparative Examples 1-3 and Example 3. FIG. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on Comparative Examples 1-3 and Example 4. FIG. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on Comparative Examples 1-3 and Example 5. FIG. It is an evaluation result of the brightness nonuniformity which arises in the illuminating device which concerns on the comparative example 4 and Examples 6-8. It is explanatory drawing of the bright line which appears in the light-projection surface part of the light-guide plate of a comparative example. It is explanatory drawing of the hot spot which appears in the light-projection surface part of the light-guide plate of a prior art. It is explanatory drawing which shows the definition of a diffusion angle. It is explanatory drawing which shows the measurement direction of the diffusion angle of the optical sheet which has an uneven | corrugated structure on one side. It is explanatory drawing which shows the line which measures a brightness | luminance profile in an Example and a comparative example.

  The present inventor has provided a lenticular lens-like uneven structure extending in the normal direction of the light incident surface portion on the light exit surface portion for performing local dimming, and at the back surface from the light exit surface portion to eliminate the hot spot. A light guide plate having a groove shape extending in the part direction was produced. Then, when a prototype of a sidelight type illumination device composed of a light source group composed of the light guide plate, a plurality of point light sources, and a reflective member, the light exit surface portion of the light guide plate is different from a hot spot in the vicinity of the light incident surface portion. It has been found that a bright region (bright line) is generated in an oblique direction from the light source (see FIG. 6).

  Further, the bright line generated in the vicinity of the light incident surface portion is provided with a lenticular lens-shaped concavo-convex structure extending in the normal direction of the light incident surface portion on the light emitting surface portion, or extends from the light emitting surface portion toward the back surface portion on the light incident surface portion. It has been found that when a groove shape is provided, it does not occur only in either case, but occurs only when both are combined. Therefore, the present inventor conceived a sidelight type lighting device capable of suppressing hot spots and providing local dimming by providing a predetermined uneven structure on the light emitting surface portion and the light incident surface portion of the light guide plate. It came to.

  Hereinafter, modes for carrying out the present invention (hereinafter abbreviated as “embodiments”) will be described in detail with reference to the drawings as appropriate. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

(Light guide plate)
FIG. 1 is a schematic perspective view of a light guide plate 1 used in the illumination device according to the embodiment. The light guide plate 1 has a substantially rectangular flat plate shape, one main surface is a light emitting surface portion, and the other main surface is a back surface portion. The light guide plate 1 has a side surface portion (here, four side surface portions) located between the light emitting surface portion and the back surface portion, and one of them is a light incident surface portion. The light incident surface portion may be two opposing surfaces of the side surface portions. Further, the shape of the light guide plate 1 is not limited to a rectangle.

  The light guide plate 1 has a first concavo-convex structure 4 on the light exit surface portion and a second concavo-convex structure 5 on the light incident surface portion. The first concavo-convex structure 4 has a shape that imparts anisotropic diffusibility so that the diffusion angle in the normal direction of the light incident surface portion is smaller than the direction orthogonal to the normal direction with respect to the transmitted light of the light exit surface portion. Have Further, the second concavo-convex structure 5 imparts anisotropic diffusibility so that the diffusion angle in the normal direction of the light exit surface portion is smaller than the direction orthogonal to the normal direction with respect to the transmitted light of the light incident surface portion. Has a shape. Here, the anisotropic means a state in which the property (here, the diffusibility of transmitted light) varies depending on the direction.

  By setting the diffusion angle of the first concavo-convex structure 4 as described above, the light that attempts to spread in the light guide plate in the direction perpendicular to the normal direction of the light incident surface portion is reflected by the concavo-convex structure. Can be present only in the front section of the point light source, i.e. local dimming is possible which only illuminates the front section of the point light source. Moreover, by setting the diffusion angle in the second concavo-convex structure 5 as described above, the angle of light that can enter the light guide plate can be increased, and hot spots can be reduced.

  In the present invention, the “diffusion angle” means an angle (FWHM: Full Width Half Maximum) that is twice the angle (half-value angle) at which the transmitted light intensity attenuates to half of the peak intensity (see FIG. 8). This diffusion angle is, for example, from Gotonometric Radiometers Real-Time Far-Field Angular Profiles Model LD8900 (hereinafter referred to as “LD8900”) manufactured by Photon, and from the normal direction of the surface on which the uneven structure of the object to be measured is formed. The angle distribution of transmitted light intensity with respect to light incident on the concavo-convex structure (distribution of transmitted light intensity with respect to the emission angle) can be obtained. Here, the normal direction of the surface on which the concavo-convex structure is formed refers to the vertical direction when the surface on which the concavo-convex structure is formed is regarded as a horizontal plane (here, the back surface of the concavo-convex structure), as shown in FIG. .

  Note that the diffusion angle is theoretically (Snell's law), if the substrate does not have internal diffusion performance, it is not affected by the refractive index of the substrate, and the material that forms the surface on which the concavo-convex structure is formed. Depends on refractive index. For this reason, as a method of forming a concavo-convex structure on the incident surface portion or the output surface portion of the light guide plate, if a manufacturing method in which a film having a concavo-convex structure is bonded is employed, measurement of the diffusion angle measured by the film having the concavo-convex structure alone The result can be regarded as a measurement result of a diffusion angle measured in a final state in which a film having an uneven structure is bonded to a light guide plate. Alternatively, a thin piece obtained by cutting the light guide plate along a plane parallel to the incident surface portion or the output surface portion may be produced, and the diffusion angle thereof may be measured.

  In addition, when the surface facing the surface to be measured is not smooth, the surface is made smooth by cutting or the like, or the surface shape of the surface to be measured is the same refraction as the material forming the surface It can be transferred to a material having a rate and the transferred material can be measured. This is because the angle distribution of the transmitted light intensity does not change even when the unevenness is reversed, and the diffusion angle does not change.

  The first concavo-convex structure 4 may be a periodic shape or an aperiodic shape, but an aperiodic shape in which moire due to interference hardly occurs is preferable. As a diffusion angle that the first concavo-convex structure 4 gives to the transmitted light of the light exit surface portion, the diffusion angle in the normal direction of the light incident surface portion is preferably 10 ° or less, more preferably 5 ° or less, and most preferably 1 ° or less. preferable. The diffusion angle in the direction perpendicular to the normal direction of the light incident surface portion is preferably 20 ° or more, more preferably 40 ° or more, and most preferably 60 ° or more.

  The first concavo-convex structure 4 in the light exit surface portion is preferably formed so that the pitch in the direction orthogonal to the normal direction of the light incident surface portion is smaller than the pitch in the normal direction of the light incident surface portion. Thereby, the light that attempts to spread in the direction perpendicular to the normal direction of the light incident surface portion in the light guide plate can be reflected by the concavo-convex structure, and the light can be present only in the front section of the point light source, that is, Local dimming in which only the front section of the point light source is illuminated becomes possible.

  The first concavo-convex structure 4 may be, for example, a lenticular lens-like concavo-convex structure having the cross-sectional shape shown in FIG. 3A, or a prism-like concavo-convex structure having the cross-sectional shape shown in FIG. It may be. In this case, the pitch is preferably 1 to 300 μm, and the height is preferably 1 to 100 μm.

  Further, the first concavo-convex structure 4 has a pitch in the normal direction of the light incident surface portion, a pitch in a direction orthogonal to the normal direction, a height, an arrangement, and a cross-sectional shape shown in FIG. Of the cross-sectional shapes, at least one item may be a non-periodic shape. Such a non-periodic concavo-convex structure can be formed using, for example, interference exposure using a speckle pattern. In this case, the average pitch in the direction orthogonal to the normal direction of the light incident surface portion is preferably 1 to 50 μm, and the average height is preferably 1 to 20 μm.

  When speckle pattern exposure is used, specifically, an aperiodic uneven structure can be formed as follows. For example, a random speckle pattern such as a speckled pattern or a striped pattern is generated by interference exposure using laser light, and this is irradiated to a layer made of a photosensitive resin material such as a photoresist. Next, when the exposed photosensitive resin material layer is developed by a known method, an aperiodic uneven structure corresponding to the speckle pattern is formed on the surface of the cured photosensitive resin material layer.

  Note that the random speckle pattern or striped speckle pattern can be generated by, for example, diffusing laser light with a diffusion layer having strong anisotropy. Normally, when the laser beam is diffused by the diffusion layer and irradiated to the exposed surface, speckles are generated as circular unevenness. However, if the diffusion layer has a strong anisotropy, the speckles have a speckled or striped pattern. be able to. Furthermore, a desired random spot / striped pattern can be obtained by appropriately changing the wavelength of the laser light, the conditions for diffusing the laser light, and the like. Specifically, it can be generated by the method disclosed in paragraphs 0047 to 0057 of JP-T-2004-508585.

  In addition, a transfer mold can be produced by a known method as a sub-master mold having a concavo-convex structure produced as described above, and the concavo-convex structure can be transferred onto the surface of the transparent resin layer using this.

  In addition, a method for producing a fine concavo-convex structure using a speckle pattern by interference exposure is well known, and is disclosed in, for example, Japanese Patent No. 3341519, Japanese Patent Publication No. 2003-525472, Japanese Patent Publication No. 2004-508585, and the like. Yes.

  The second concavo-convex structure 5 may be a periodic shape or a non-periodic shape, but is preferably a non-periodic shape that does not cause a peak in the intensity distribution of diffused light. As the diffusion angle that the second uneven structure 5 gives to the transmitted light of the light incident surface portion, the diffusion angle in the normal direction of the light emitting surface portion is preferably 10 ° or less, more preferably 5 ° or less, and most preferably 1 ° or less. preferable. In addition, the diffusion angle in the direction perpendicular to the normal direction of the light emitting surface portion is preferably 15 ° to 100 °, more preferably 20 ° to 80 °, and most preferably 20 ° to 50 °.

  In addition, it is preferable that the second concavo-convex structure 5 is formed so that the pitch in the direction perpendicular to the normal direction of the light emitting surface portion is smaller than the pitch in the normal direction of the light emitting surface portion. Thereby, the angle of the direction orthogonal to the normal line direction of the light emission surface part of the light which can approach in a light-guide plate can be enlarged, and a hot spot can be reduced.

  The second concavo-convex structure 5 may be, for example, a lenticular lens-like concavo-convex structure having the cross-sectional shape shown in FIG. 3A, or a prism-like concavo-convex structure having the cross-sectional shape shown in FIG. It may be. In this case, the pitch is preferably 1 to 300 μm, and the height is preferably 1 to 100 μm.

  Further, the second concavo-convex structure 5 may have a shape in which at least one of the pitch, height, arrangement, and cross-sectional shape is aperiodic, as in the cross-sectional shape shown in FIG. . Such a non-periodic concavo-convex structure can be formed using, for example, interference exposure using a speckle pattern. In this case, the average pitch in the direction orthogonal to the normal direction of the light emitting surface portion is preferably 1 to 50 μm, and the average height is preferably 1 to 20 μm.

  The first concavo-convex structure 4 and the second concavo-convex structure 5 are cross sections formed of combinations of straight lines and curves as shown in FIG. 4 in addition to the cross-sectional shape shown in FIG. A shape may be sufficient and it is not limited to these, Various uneven structures can be used. 4A, 4D, and 4G, the slope is straight, FIG. 4D is the top of the concavo-convex structure is flat, and FIG. 4G is the concavo-convex. The upper part of the structure is curved. 4 (b) and 4 (e) have a curved surface whose slope is convex upward, and FIG. 4 (e) has a flat top of the concavo-convex structure. 4 (c), (f), and (h) are curved with convex slopes downward, (f) is flat on the top of the concavo-convex structure, and (h) is curved on the top of the concavo-convex structure. It has become.

  Further, the first concavo-convex structure 4 and / or the second concavo-convex structure 5 may be formed integrally with the light guide plate 1, or a plate-like member (or “film-like member”) having the concavo-convex structure is used as the light guide plate. It may be formed by pasting. The plate-like member having the concavo-convex structure may have the concavo-convex structure formed integrally with the base material layer, or may have a multilayer structure including the base material layer and the surface layer having the concavo-convex structure.

  The light guide plate 1 is preferably subjected to light scattering processing on the back surface portion so as to emit light from the light emitting surface portion. In this light scattering process, one surface may have a uniform scattering property, or the scattering property may be changed depending on the position in order to make the light emission distribution on the light emitting surface portion uniform.

Specifically, as the light scattering process, a process of applying light-reflecting or light-absorbing ink in the form of dots on the back surface can be mentioned. When changing the degree of light scattering on the back surface with dot-like ink, the density of dots of a certain area may be changed depending on the location, the density of the dots may be changed to change the area of the dots, The ink film thickness may be changed depending on the location. Area of each dot is preferably 25 [mu] m ² or more ～250000Myuemu ² or less.

  As the light reflective ink, white ink is most preferable from the viewpoint of high reflectance and low absorption. Moreover, as a coating method, since the pattern of a white ink cured material can be formed freely, a printing method is preferable. Here, the white ink cured product means a cured white ink composition, and the white ink composition includes a solvent, a white pigment, a dispersant, and a resin as a fixing agent on the surface of the object. Included as a basic ingredient.

Specific examples of the white pigment in the white ink composition include titanium oxide (TiO ₂ , titanium white), calcium carbonate, talc, clay, aluminum silicate, basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , silver White), zinc oxide (ZnO, zinc white), strontium titanate (SrTiO ₃ , titanium strontium white), barium sulfate and the like can be used alone or in a mixed system.

  The mixing ratio of the white pigment is preferably 30% by mass to 60% by mass of the entire white ink composition. It is generally preferable to use a white pigment other than titanium oxide in an amount of up to about 30% of the whole white pigment for the purpose of dispersion aid if necessary.

  Examples of the resin in the white ink composition include ketone resin, sulfoamide resin, maleic acid resin, ester gum, xylene resin, alkyd resin, rosin, polyvinyl pyrrolidone, polyvinyl butyral, acrylic resin, melamine resin, cellulose resin, and vinyl. Resins, phenol resins, ester resins and the like can be used, and among them, acrylic resins can be preferably used.

  The organic solvent in the white ink composition is used for the purpose of dissolving the resin and adjusting the viscosity, and is an aromatic hydrocarbon solvent such as toluene, xylene, ethylbenzene, n-hexane, n-heptane, isoheptane, Aliphatic hydrocarbon solvents such as n-octane and isooctane and cycloparaffin solvents such as methylcyclohexane and ethylcyclohexane can be used alone or as a mixture. The amount of the organic solvent used is about 30% by mass to 60% by mass of the entire white ink composition.

  The thickness of the light guide plate (the distance between the light emitting surface portion and the back surface portion) is not limited, but can be, for example, about 2.0 to 5.0 mm.

  The material of the light guide plate is not particularly limited as long as it is translucent. For example, the light guide plate is generally used as a material for optical components such as polymethyl methacrylate, polycarbonate, polystyrene, and methyl methacrylate-styrene copolymer. High-polymer materials and inorganic materials such as glass can be used.

  The light guide plate is made of organic or inorganic dyes and pigments, matting agents, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, color stabilizers, antioxidants, UV absorbers, impurities as necessary. Additives such as scavengers, thickeners, surface conditioners and mold release agents may be contained within a range not impairing the object of the present invention.

  In addition to the light guide plate 2 described above, the illumination device shown in the present embodiment is a light source composed of a plurality of point light sources 6 so as to face the back surface of the light guide plate 2 as shown in FIG. The light diffusion member 2 further diffuses and transmits the light incident from the group. Moreover, it further has the reflection member 3 which has light reflectivity so that the surface on the opposite side to the light guide plate 1 of the light-diffusion member 2 may be opposed. In this case, the light guide plate 1, the light diffusing member 2 facing the back surface portion of the light guide plate 1, and the reflecting member 3 facing the surface opposite to the light guide plate 1 side of the light diffusing member 2 are laminated and guided. A plurality of point light sources 6 are arranged on the light incident surface portion of the optical plate 1.

  The light guide plate 1 and the light diffusing member 2 may be simply overlapped, may be bonded, or may be integrally formed. Below, the light-diffusion member 2, the reflection member 3, and the point light source 6 are demonstrated.

(Light diffusion member)
The light diffusing member 2 is a plate-like member having light diffusibility. This light diffusibility is a member having a light diffusible additive inside the member, a member having a third concavo-convex structure 7 for imparting light diffusibility to transmitted light on the surface, or a member having features of both It is preferable that it is either.

  As the light diffusing additive, any of organic materials, inorganic materials, and composite materials of organic materials and inorganic materials can be used.

  As the third concavo-convex structure 7, the isotropic shape or the diffusion angle of the light incident surface portion of the light guide plate 1 in the normal direction with respect to the transmitted light is made smaller than the direction orthogonal to the normal direction. Any shape that imparts anisotropic diffusivity can be used.

  The third uneven structure 7 may have a periodic shape or a non-periodic shape. When the third concavo-convex structure 7 is isotropic, the diffusion angle given to the transmitted light is preferably 20 ° or more, more preferably 50 ° or more, and most preferably 70 ° or more.

  When the third uneven structure 7 is anisotropic, the diffusion angle given to the transmitted light by the third uneven structure 7 is 10 ° as the diffusion angle in the normal direction of the light incident surface portion of the light guide plate 1. Or less, more preferably 5 ° or less, and most preferably 1 ° or less. Further, the diffusion angle in the direction orthogonal to the normal direction of the light incident surface portion of the light guide plate 1 is preferably 10 ° or more, more preferably 50 ° or more, and most preferably 70 ° or more.

  The third concavo-convex structure 7 is formed such that the pitch in the direction perpendicular to the normal direction of the light incident surface portion of the light guide plate 1 is smaller than the pitch in the normal direction of the light incident surface portion of the light guide plate 1. Is preferred. This is because bright lines can be reduced.

  The third concavo-convex structure 7 may be, for example, a lenticular lens-like concavo-convex structure having the cross-sectional shape shown in FIG. 3A, or a prism-like concavo-convex structure having the cross-sectional shape shown in FIG. It may be. In this case, the pitch is preferably 1 to 300 μm, and the height is preferably 10 to 100 μm.

  Further, the third concavo-convex structure 7 may have a shape in which at least one of the pitch, height, arrangement, and cross-sectional shape is aperiodic as in the cross-sectional shape shown in FIG. . Such a non-periodic concavo-convex structure can be formed using, for example, interference exposure using a speckle pattern. In this case, the average pitch in the direction orthogonal to the normal direction of the light emitting surface portion is preferably 1 to 50 μm, and the average height is preferably 1 to 20 μm.

  In addition to the cross-sectional shape shown in FIG. 3, the third concavo-convex structure 7 may be, for example, a shape composed of a combination of a straight line and a curve as shown in FIG. Structure can be used. Moreover, the 3rd uneven structure 7 may be formed in the light-guide plate side of the light-diffusion member, and may be formed in the reflection member side.

  The light diffusing member 2 may be formed integrally with a base material layer and a layer having a concavo-convex structure, or may be a multilayer structure including a base material layer and a layer having a concavo-convex structure.

(Reflective member)
As the reflecting member 3, various members can be used as long as they can reflect light. For example, a resin such as polyester or polycarbonate is foamed and fine air particles are made into a sheet, and a sheet is formed by mixing two or more resins, and resin layers with different refractive indexes are laminated. A sheet having a mirror surface prepared by vapor-depositing a metal on the surface of the substrate can be used. Moreover, as the reflecting member 3, the uneven structure may be formed in the surface. As these, those having inorganic fine particles added to the surface can be used as necessary.

  As the material of the substrate used for the light diffusing member 2 and the reflecting member 3, any of organic materials, inorganic materials, and composite materials of organic materials and inorganic materials can be used. In particular, an organic material such as an organic polymer material is a preferable base material because it is excellent in workability such as cutting, welding, bending, and cutting. Examples of the organic polymer include polycarbonate, polyurethane, polyacrylonitrile, polyvinyl alcohol, polyvinyl acetal, polyester, polyamide, polystyrene, polysulfone, cellulose, triacetyl cellulose, cellulose acetate, polyethylene, polypropylene, polyvinyl fluoride, polyvinylidene fluoride, Polytrifluorochlorovinyl, vinylidene fluoride-tetrafluoroethylene copolymer, polyethersulfone, polymethyl (meth) acrylate, butadiene-acrylonitrile copolymer, polyether-polyamide block copolymer, ethylene-vinyl alcohol copolymer, cycloolefin polymer, etc. However, it is not limited to these. As a material of the base material used for the light diffusing member 2, a material that is transparent or translucent among these materials is used.

(Light source group)
Although there is no limitation in the point light source 6, it is preferable to use LED (light emitting diode). There is no limitation on the type of LED, for example, a one-chip type pseudo white LED that excites green and red phosphors by a blue LED, a multi-chip type that combines white / red / green / blue LEDs to produce white light, and the near ultraviolet One-chip type pseudo white LED that combines an LED and a red / green / blue phosphor may be used.

  There is no limitation on the outer shape of the LED and the size of the light emitting surface, but the outer shape is about 5.6 mm (width) x 3.0 mm (height) x 1.0 mm (thickness) and the width of the light emitting surface is 5 mm or less. Commonly used.

  The arrangement method of the point light source 6 is not limited, but it is assumed that an equal interval (an equal interval) includes an error of ± 10% along a light incident surface portion of the light guide plate 1 (parallel to the light emitting surface portion) on a straight line. ) Is preferably used. In this case, the arrangement pitch P of the plurality of point light sources 6 can be set to, for example, about 0.2 mm to 50 mm.

  Moreover, since the illuminating device of this invention uses the light guide plate suitable for local dimming as the light guide plate 1, the light source group arrange | positioned in the light-incidence surface part vicinity is made into two or more groups so that local dimming can be implemented. The brightness (flashing) of each point light source constituting each group can be controlled independently for each group. Furthermore, by dividing the plurality of point light sources 6 into a plurality of groups (preferably equally in order from the end) and controlling so that the point light sources belonging to each group are sequentially lit up and down (in some cases left and right), Scanning used for displaying a three-dimensional image is possible.

  Next, although an Example and a comparative example are given and this Embodiment is demonstrated more concretely, unless this summary is exceeded, this invention is not limited to a following example.

[Light source group]

  The sidelight type illuminating devices according to Examples and Comparative Examples to be described later are light emitting diodes having a horizontal (light guide plate thickness direction) of 5.6 mm and a vertical (light guide plate width direction) of 3 mm as a point light source. A light source group arranged to be 8 mm was used.

[Evaluation of uneven brightness]
A luminance profile in a direction parallel to the light incident surface portion from the luminance data of the light emission surface portion measured by a two-dimensional color luminance meter (CA-2000 manufactured by Konica Minolta), and a distance A from a point light source in a range of 5 mm to 40 mm. And extracted in steps of 2.5 mm. In order to cancel the luminance gradient unrelated to the luminance unevenness from each of the luminance profiles L (X) (X axis: distance in the direction parallel to the light incident surface portion, Y axis: luminance L), the pitch P of the light emitting diode (this In this case, a smoothed value (moving average value) was obtained by taking an average value in a range corresponding to 18.8 mm (see formula (1)).

  The range of X is a range excluding point light sources at both ends, that is, from the position of the second light emitting diode from the end of the light source group to the position of the second light emitting diode from the other end. Yes.

[Comparative Example 1]
The sidelight type illumination device according to Comparative Example 1 uses the light source group described above, and a light guide plate is formed with a first concavo-convex structure in the form of a lenticular lens having a pitch of 290 μm and a height of 60 μm as a light guide plate. A transparent acrylic plate with a thickness of 3 mm on which white dot printing was applied as a light scattering process was used. The first concavo-convex structure having a lenticular lens shape is provided so that the convex portion (or concave portion) extends in the normal direction of the light incident surface portion, and in the normal direction of the light incident surface portion with respect to the transmitted light of the light emitting surface portion. The diffusion angle is made smaller than the direction orthogonal to the normal direction. Further, a reflective member (mounted on BRAVIA KDL-32EX700 manufactured by Sony Corporation) is provided on the back surface side of the light guide plate, and a diffusion sheet (mounted on BRAVIA KDL-32EX700 manufactured by Sony Corporation) is provided on the light exit surface side of the light guide plate. ) Was prepared.

[Comparative Example 2]
In the sidelight illumination device according to Comparative Example 2, a concavo-convex structure was formed on the light incident surface portion of the light guide plate of the sidelight illumination device according to Comparative Example 1 using interference exposure using a speckle pattern. Specifically, the diffusion angle is 80 ° in the minor axis direction of the concavo-convex structure, 3 ° in the major axis direction of the concavo-convex structure, the average pitch in the minor axis direction is about 5.4 μm, and the average pitch in the major axis direction is about 5.4 μm. A polyethylene terephthalate film having an average thickness of 100 μm, in which a non-periodic second uneven structure having an average height of about 300 μm and an average height of about 3.6 μm is formed in a direction in which the major axis direction extends from the light emitting surface portion to the back surface portion. And what was bonded using the 25-micrometer-thick transparent double-sided adhesive sheet (PD-S1 by Panac Corporation) was produced.

[Comparative Example 3]
The sidelight type illumination device according to Comparative Example 3 is a light diffusion member between the light guide plate and the reflection member of the sidelight type illumination device according to Comparative Example 1, and the diffusion angle is 66 ° in the minor axis direction of the prism shape. The prism shape, which is 1 ° in the major axis direction of the prism shape, has a vertex angle of 90 degrees, a pitch of 50 μm, and a height of 25 μm, and the prism shape, which is the third uneven structure, extends in the normal direction of the light incident surface portion. In addition, the prism shape was disposed on the reflecting member side.

[Example 1]
In the sidelight type illumination device according to Example 1, a light diffusion member is provided between the light guide plate and the reflection member of the sidelight type planar illumination device according to Comparative Example 2. As the light diffusion member, a prism sheet having a diffusion angle of 66 ° in the minor axis direction of the prism shape and 1 ° in the major axis direction of the prism shape, an apex angle of 90 degrees, a pitch of 50 μm, and a height of 25 μm is used. The prism shape, which is the uneven structure, is arranged so as to extend in the normal direction of the light incident surface portion, and is arranged so that the prism shape is on the reflecting member side. In this case, the diffusion angle in the normal direction (major axis direction of the prism) of the light incident surface portion of the light guide plate with respect to the transmitted light is smaller than the diffusion angle in the direction perpendicular to the normal direction (minor axis direction). .

  FIG. 5A shows an evaluation result of luminance unevenness of the sidelight type illumination device according to the first embodiment. In FIG. 5, the horizontal axis is (distance A from point light source) / (pitch P between point light sources), and the vertical axis is S.P. D. Value.

  From FIG. 5A, in Example 1, in the vicinity of the light incident surface (A / P = 5 mm / 18.8 mm≈0.27 position: see FIG. 10), the S. D. The value was reduced by about 90% compared to the sidelight type planar illumination device according to Comparative Example 1 and about 86% compared with Comparative Example 3. In addition, compared with Comparative Example 2, the S.P. D. The tendency of the value to go up and down has been eliminated. Further, even in the visual evaluation, it was confirmed that the occurrence of the hot spot visually recognized in Comparative Examples 1 and 3 and the bright line visually recognized in Comparative Example 2 were not visually recognized, and the luminance unevenness was improved.

[Example 2]
The sidelight type illumination device according to the second embodiment has the prism sheet of the sidelight type planar illumination device according to the first embodiment so that the prism shape extends in the normal direction of the light incident surface portion and the prism shape is guided. It was arranged so as to be on the optical plate side.

  FIG. 5B shows an evaluation result of luminance unevenness of the sidelight type illumination device according to the second embodiment. In the vicinity of the light incident surface (A / P = 5 mm / 18.8 mm≈0.27 position) D. The value was reduced by about 80% compared to the sidelight type illumination device according to Comparative Example 1 and about 73% compared with Comparative Example 3. In addition, compared with Comparative Example 2, the S.P. D. The tendency of the value to go up and down has been eliminated. Further, even in the visual evaluation, it was confirmed that the occurrence of the hot spot visually recognized in Comparative Examples 1 and 3 and the bright line visually recognized in Comparative Example 2 were not visually recognized, and the luminance unevenness was improved.

[Example 3]
The sidelight type illumination device according to Example 3 includes a diffusing agent inside the base material instead of the prism sheet of the sidelight type illumination device according to Example 1, and the diffusion angle is 60 ° in the minor axis direction of the prism shape. The prism shape is 5 ° in the major axis direction, the apex angle is 90 °, the pitch is 50 μm, and the height is 24 μm. The prism shape extends in the normal direction of the light incident surface portion, and the prism shape is a reflecting member. It was arranged so as to be on the side.

  FIG. 5C shows the evaluation result of luminance unevenness of the sidelight type illumination device according to Example 3. In the vicinity of the light incident surface (A / P = 5 mm / 18.8 mm≈0.27 position) D. The value was reduced by about 80% compared with the sidelight type illumination device according to Comparative Example 1 and about 75% compared with Comparative Example 3. In addition, compared with Comparative Example 2, the S.P. D. The tendency of the value to go up and down has been eliminated. Further, even in the visual evaluation, it was confirmed that the occurrence of the hot spot visually recognized in Comparative Examples 1 and 3 and the bright line visually recognized in Comparative Example 2 were not visually recognized, and the luminance unevenness was improved.

[Example 4]
The sidelight type illuminating device according to Example 4 includes a diffusing agent-containing prism sheet of the sidelight type illuminating device according to Example 3, so that the prism shape extends in the normal direction of the light incident surface portion, and the prism shape is An arrangement was made so that it was on the light guide plate side.

  FIG. 5 (d) shows the evaluation results of luminance unevenness of the sidelight type planar illumination device according to Example 4. In the vicinity of the light incident surface (A / P = 5 mm / 18.8 mm≈0.27 position) D. The value was reduced by about 78% compared to the sidelight type planar illumination device according to Comparative Example 1 and about 71% compared with Comparative Example 3. In addition, compared with Comparative Example 2, the S.P. D. The tendency of the value to go up and down has been eliminated. Further, even in the visual evaluation, it was confirmed that the occurrence of the hot spot visually recognized in Comparative Examples 1 and 3 and the bright line visually recognized in Comparative Example 2 were not visually recognized, and the luminance unevenness was improved.

[Example 5]
In the sidelight type illumination device according to the fifth embodiment, the prism sheet of the sidelight type illumination device according to the first embodiment is arranged so that the prism shape extends in a direction perpendicular to the normal direction of the light incident surface portion, and the prism shape Was arranged so as to be on the reflecting member side.

  FIG. 5 (e) shows the evaluation results of luminance unevenness of the sidelight type planar illumination device according to Example 5. In the vicinity of the light incident surface (A / P = 5 mm / 18.8 mm≈0.27 position) D. The value was reduced by about 81% compared to the sidelight type planar illumination device according to Comparative Example 1 and about 75% compared with Comparative Example 3. In addition, compared with Comparative Example 2, the S.P. D. The tendency of the value to go up and down greatly improved. Moreover, even in the visual evaluation, it was confirmed that the luminance unevenness due to the hot spot visually recognized in Comparative Examples 1 and 3 and the bright line visually recognized in Comparative Example 2 was improved.

[Comparative Example 4]
In the sidelight type illumination device according to Comparative Example 4, the first concavo-convex structure of a lenticular lens shape having a pitch of 290 μm and a height of 80 μm is formed on the light emitting surface portion as a light guide plate, and the speckle is formed on the light incident surface portion. The diffusion angle formed by interference exposure using a pattern is 80 ° in the minor axis direction of the concavo-convex structure and 3 ° in the major axis direction of the concavo-convex structure, and the average pitch in the minor axis direction and the major axis direction is about 5.4 μm, respectively. A polyethylene terephthalate film having an average thickness of 100 μm, in which a non-periodic second uneven structure having an average height of about 3.6 μm is formed in a direction in which the major axis direction is directed from the light emitting surface portion to the back surface portion. In addition, a 25 μm thick transparent double-sided adhesive sheet (PD-S1 manufactured by Panac Co., Ltd.) was used for bonding, and a recess was formed on the back surface by laser processing as light scattering processing. It was used an acrylic plate having a thickness of 3 mm. The first concavo-convex structure having a lenticular lens shape is provided so that the convex portion (or concave portion) extends in the normal direction of the light incident surface portion, and in the normal direction of the light incident surface portion with respect to the transmitted light of the light emitting surface portion. The diffusion angle is made smaller than the direction orthogonal to the normal direction. Further, a reflective member (mounted on BRAVIA KDL-32EX700 manufactured by Sony Corporation) is provided on the back surface side of the light guide plate, and a diffusion sheet (mounted on BRAVIA KDL-32EX700 manufactured by Sony Corporation) is provided on the light exit surface side of the light guide plate. ) Was prepared.

[Example 6]
The sidelight type illumination device according to Example 6 is a light diffusion member between the light guide plate and the reflection member of the sidelight type illumination device according to Comparative Example 4, and the diffusion angle is 66 ° in the minor axis direction of the prism shape. Using a prism sheet with an angle of 1 ° in the major axis direction of the prism shape, an apex angle of 90 degrees, a pitch of 50 μm, and a height of 25 μm, the prism shape extends in the normal direction of the light incident surface portion, and the prism shape is reflected It was arranged so as to be on the member side.

[Example 7]
The sidelight type illumination device according to Example 7 includes a diffusion agent as a light diffusion member between the light guide plate and the reflection member of the sidelight type illumination device according to Comparative Example 4, and has a diffusion angle of 17 °. The diffusion sheet was arranged and produced.

[Example 8]
The sidelight type illuminating device according to Example 8 is formed by using interference exposure with a speckle pattern as a light diffusing member between the light guide plate and the reflecting member of the illuminating device according to Comparative Example 4, and the diffusion angle is uneven. The pitch is 75 ° in the minor axis direction of the structure and 1 ° in the major axis direction of the concavo-convex structure, and the average pitch in the minor axis direction and the major axis direction is about 4.7 μm and 1 mm, respectively, and the average height is about 2.1 μm. A polyethylene terephthalate film having an average thickness of 100 μm on which an aperiodic uneven structure having a height, arrangement, and cross-sectional shape is formed, and the long axis of the uneven structure extends in the normal direction of the light incident surface portion of the light guide plate In addition, the concavo-convex structure was disposed on the reflecting member side.

  FIG. 5F shows the evaluation results of luminance unevenness of the sidelight type illumination devices according to Comparative Example 4, Example 6, Example 7, and Example 8. In Examples 7 and 8, a light diffusing member is installed between the light guide plate and the reflecting member. D. The value is decreased by 10% or more, that is, the luminance unevenness is reduced. D. The tendency for the value to go up and down was also eliminated.

  The present invention can be suitably used for a liquid crystal display device and a 3D liquid crystal display device with high contrast and low power consumption by local dimming.

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Light diffusing member 3 Reflective member 4 1st uneven structure 5 2nd uneven structure 6 Point light source 7 3rd uneven structure

Claims (11)

A lighting device comprising a light source group in which a plurality of point light sources are arranged, a light guide plate, a light diffusion member, and a reflection member,
The light guide plate has a light emission surface portion from which light incident on the light guide plate is emitted, a back surface portion facing the light emission surface portion, and a side surface portion positioned between the light emission surface portion and the back surface portion. A light incident surface portion on which light emitted from the light source group is incident on a part of the side surface portion, and a diffusion angle in a normal direction of the light incident surface portion with respect to transmitted light on the light output surface portion A first concavo-convex structure that imparts anisotropic diffusivity is made smaller than the direction perpendicular to the normal direction, and the light incident surface portion is directed to the normal direction of the light emitting surface portion with respect to the transmitted light. A second concavo-convex structure imparting anisotropic diffusivity that makes the diffusion angle smaller than the direction perpendicular to the normal direction is formed,
The light diffusing member is a flat member that diffuses and transmits incident light, and is installed facing the back surface of the light guide plate.
The said reflecting member is a flat member which has light reflectivity, Comprising: It is installed facing the surface on the opposite side to the said light-guide plate of the said light-diffusion member, The illuminating device characterized by the above-mentioned.   The lighting device according to claim 1, wherein the light diffusion member is bonded to the back surface portion of the light guide plate.   The lighting device according to claim 1, wherein the light diffusing member is integrally formed on the back surface of the light guide plate.   In the first uneven structure, at least one of the pitch in the normal direction of the light incident surface portion, the pitch in the direction orthogonal to the normal direction, the height, the arrangement, and the cross-sectional shape is aperiodic. The lighting device according to any one of claims 1 to 3, wherein   The lighting device according to any one of claims 1 to 4, wherein the back surface portion of the light guide plate is subjected to light scattering processing.   In the second concavo-convex structure, at least one of the pitch in the normal direction of the light emitting surface portion, the pitch in the direction orthogonal to the normal direction, the height, the arrangement, and the cross-sectional shape is aperiodic. The lighting device according to any one of claims 1 to 5, wherein   The lighting device according to claim 1, wherein the light diffusing member includes an additive that imparts light diffusibility to transmitted light inside.   The said light-diffusion member is formed in the at least one surface by the 3rd uneven structure which provides light diffusibility with respect to transmitted light, The one in any one of Claim 1 to 6 characterized by the above-mentioned. Lighting device.   The third concavo-convex structure imparts anisotropic diffusion to the light diffusing member so that a diffusion angle in the normal direction of the light incident surface portion with respect to transmitted light is smaller than a direction orthogonal to the normal direction. The lighting device according to claim 8, wherein:   The third concavo-convex structure has at least one item out of a pitch in a normal direction of the light incident surface portion of the light guide plate, a pitch in a direction orthogonal to the normal direction, a height, an arrangement, and a cross-sectional shape. The lighting device according to claim 8, wherein the lighting device is periodic.   11. The first uneven structure, the second uneven structure, and the third uneven structure are uneven structures formed by using interference exposure with a speckle pattern. The illuminating device in any one of.

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