JP2011138698A - Surface light source device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light utilization efficiency while achieving thinness, light weight, and low cost of a device. <P>SOLUTION: The surface light source device 11 includes a light source 12 and a light guide plate 13 which guides light from the light source 12 and is made of a plate body. The light guide plate 13 includes: a light guide plate body 15 having a rear face 16 to reflect light propagating inside, and an emitting face 17 to emit light propagating inside; and an incident end part 14 which is arranged integrally at the side part of the light guide plate body 15 and on which light from the light source 12 is incident. The incident end part 14 has: an incident face 18 which receives light from the light source 12; and an inclined face 19 which is inclined against the incident face 18 so as to reflect the light emitted from the light source 12 entered through the incident face 18 toward the light guide plate body 15 side. The light source 12 is established at light distribution characteristics of a full width at half maximum of 45° or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface light source device that illuminates an object to be illuminated, and a liquid crystal display device including the surface light source device.

  As a backlight used in a liquid crystal display device, a side-ride type backlight in which light from a light source is introduced from a side end surface of a light guide plate and is emitted from an output surface of the light guide plate is known. Sidelight-type backlights have the advantage that they can be made thinner than direct-type backlights, but they have the disadvantage of increasing the so-called frame area because the light source is placed around the light guide plate. is there.

  As a technique for improving such a drawback, light from a light source is incident from a direction perpendicular to the plate surface of the light guide plate in the vicinity of the side end surface of the light guide plate, guided into the light guide plate, and from the emission surface. What is made to radiate | emit is known (for example, refer patent document 1). In the technique described in Patent Document 1, a refractive surface composed of an incident surface on which light from the light source of the light guide plate is incident and a plurality of inclined surfaces that are inclined with respect to an emission surface that emits light from the light guide plate, It is arranged so as to face the incident surface, and the light incident from the incident surface is reflected and guided into the light guide plate.

  Here, since the light emitted from the light source is generally divergent light, even if the refracting surface is appropriately arranged with respect to the light beam, a part of the light beam having a critical angle or less with respect to the refracting surface is the refracting surface. Is lost. Therefore, in Patent Document 1, a reflection plate is separately arranged outside the refracting surface, and light transmitted through the refracting surface is returned to the light guide plate again.

JP 2002-365629 A

  However, providing a reflector as described in Patent Document 1 may be an obstacle to a request for further thinning of the apparatus, and may increase costs as the configuration becomes complicated. Moreover, although the loss of light is improved to some extent by the reflector, it is still not sufficient, and there is room for improving the light utilization efficiency.

  The present invention has been made in view of the above points, and a surface light source device capable of improving light utilization efficiency while reducing the thickness, weight, and cost of the device, and a liquid crystal display including the surface light source device An object is to provide an apparatus.

  According to a first aspect of the present invention, there is provided a surface light source device including a light source and a light guide plate made of a plate-like body that guides light from the light source, wherein the light guide plate reflects light propagating therein. A light guide plate body having a back surface and an exit surface for emitting light propagating therethrough, and an incident end portion that is integrally disposed on a side portion of the light guide plate body and into which light from the light source is incident The incident end portion receives the light from the light source, and reflects the light from the light source incident through the incident surface toward the light guide plate body. There is provided a surface light source device having an inclined surface and the light source set to a light distribution characteristic having a full width at half maximum of 45 ° or less.

  In the surface light source device according to the first aspect of the present invention, the water absorption rate of the light guide plate is preferably set to 0.25% or less.

  In the surface light source device according to the first aspect of the present invention, a part or all of the divided inclined surface is arranged so that a distance from the incident surface increases as it goes from the outside to the inside of the light guide plate. Can do. Further, a part or all of the divided inclined surfaces can be arranged so that the inclination angle with respect to the incident surface becomes smaller as going from the outside to the inside of the light guide plate.

  In the surface light source device according to the first aspect of the present invention, the incident end is set so that its thickness is larger than the thickness of the light guide plate body, and the light guide plate body side of the inclined surface is set. The light guide slope which connects the edge of this and the edge of the said output surface can be provided.

  According to a second aspect of the present invention, there is provided a liquid crystal display device comprising a liquid crystal panel and the surface light source device according to the first aspect of the present invention.

  In the surface light source device according to the first aspect of the present invention, a light source having a light distribution characteristic set to a full width at half maximum of 45 ° or less is used, so that the incident light is guided into the light guide plate body. If the inclined surface is optimized with respect to the incident light, most of the light beam can be reflected to the light guide plate body side. Accordingly, it is not always necessary to separately provide a reflector as in the prior art. Light loss can be suppressed and light utilization efficiency can be improved while reducing the thickness, weight and cost of the device. Can do.

  Since the liquid crystal display device according to the second aspect of the present invention includes the surface light source device according to the first aspect of the present invention, a liquid crystal display device that is thin, lightweight, low-cost, and power-saving is provided. Can do.

It is a side view which shows the principal part of the surface light source device of 1st Embodiment of this invention. It is a side view which shows the principal part of the surface light source device of 2nd Embodiment of this invention. It is a side view which shows the principal part of the surface light source device of 3rd Embodiment of this invention. It is a side view which shows the principal part of the surface light source device of 4th Embodiment of this invention. It is a side view which shows the principal part of the surface light source device of 5th Embodiment of this invention. It is a side view which shows the principal part of the surface light source device of 6th Embodiment of this invention. It is a figure which shows the relationship between the half value angle and light utilization efficiency as a simulation result in embodiment of this invention.

  Hereinafter, a surface light source device according to an embodiment of the present invention will be described with reference to the drawings. In the following, the thickness direction of a rectangular light guide plate in plan view, which will be described later, is the Z direction, and in the plane perpendicular to the Z direction, the direction along one side of the rectangular light guide plate is the X direction, and the X direction. A description will be given using an XYZ orthonormal coordinate system in which the direction orthogonal to the Y direction is the Y direction.

  This surface light source device is particularly suitable for use in a backlight that illuminates a liquid crystal panel of a liquid crystal display device as an object to be illuminated. However, the object to be illuminated is not limited to such a liquid crystal panel, and can also be used as illumination for a signboard arranged at a storefront or the like, illumination for a show window, or any other illumination. Below, the case where it uses as a backlight of a liquid crystal display device is demonstrated to an example.

(First embodiment)
First, a first embodiment of the present invention will be described with reference to FIG. The surface light source device 11 of the first embodiment includes a light source 12 and a light guide plate (film light guide plate) 13 made of a rectangular plate-like film that guides light from the light source 12. In this embodiment, the light source 12 is formed by arranging a plurality of LEDs (Light Emitting Diodes) along the X direction at a predetermined pitch. As the LED, a blue-yellow pseudo white light emitting diode, a three-color (RGB) white light emitting diode, or the like is used. However, the light source 12 is not limited to such an LED, and for example, a semiconductor laser or the like may be used.

  The light source 12 is preferably small, light and thin (low height). In this embodiment, each LED constituting the light source 12 is a cannonball type, and the axis of each LED (the direction of the chief ray of the emitted light) is arranged so as to be oriented substantially in the + Z direction. The dimension of the light source 12 in the Y direction can be set to d1 = 1 mm, for example.

  A general high dome type LED has a light distribution of Lambertian and emits a relatively large divergent light having a half-value angle (half-value full-angle) of about 120 °. The LED used in this embodiment has a half-value angle. However, at least in the Y direction, it is preferably set to 45 ° or less, more preferably 30 ° or less, still more preferably 20 ° or less, and parallel light or light close thereto (hereinafter simply referred to as parallel light) is emitted. Is most preferred. The half-value angle in the X direction may be the same as the half-value angle in the Y direction, but the wider the half-value angle in the X direction, the light can be propagated to a wider range of the XY plane, and the in-plane luminance uniformity is improved. In order to reduce the number of light sources, 45 ° or more is preferable, 90 ° or more is more preferable, and 120 ° or more is more preferable. The number or arrangement pitch of each LED is appropriately selected in relation to the dimension of the light guide plate 13 in the X direction, the maximum light emission amount of the LED, the half-value angle in the X direction, and the like.

  In addition, the LED whose half-value angle is set to a value larger than the preferable range as described above or the LED set within the preferable range as described above is used, adjacent to the LED in the Z direction (that is, By providing a lens or the like (between the LED and an incident surface 18 of the incident end portion 14 described later), the light may be converted into divergent light or parallel light in a preferable range as described above. A plurality of lenticular lenses having a longitudinal direction in the X direction may be integrally formed on an incident surface 18 of the incident end portion 14 to be described later, and converted into similar divergent light or parallel light.

  The light guide plate 13 is made of a transparent resin. The transparent resin is not particularly limited, but propylene-ethylene copolymer, polystyrene, (meth) acrylic acid ester-aromatic vinyl compound copolymer, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer. , Polycarbonate, methacrylic resin, and resin having an alicyclic structure. The light guide plate 13 may be made of glass.

  Among these, a resin having an alicyclic structure, a methacrylic resin, and a (meth) acrylic acid ester-aromatic vinyl compound copolymer resin can be preferably used, and a resin having an alicyclic structure is particularly preferably used. Can be used. Resin with alicyclic structure has good flowability of molten resin, so in injection molding, mold cavity can be filled with low injection pressure, and weld line is less likely to occur. The thickness unevenness at the time of molding is small, and shape formation after molding is easy. Further, since the hygroscopic property is extremely low, the dimensional stability is excellent, the light guide plate is not warped, and the specific gravity is small, so that the light guide plate can be reduced in weight. Moreover, as resin which has an alicyclic structure, polymer resin which has an alicyclic structure in a principal chain or a side chain can be mentioned. A polymer resin having an alicyclic structure in the main chain can be particularly preferably used because it has good mechanical strength and heat resistance. The alicyclic structure is preferably a saturated cyclic hydrocarbon structure, and the carbon number thereof is preferably 4 to 30, more preferably 5 to 20, and further preferably 5 to 15. . The ratio of the repeating unit having an alicyclic structure in the polymer resin having an alicyclic structure is preferably 50% by weight or more, more preferably 70% by weight or more, and 90% by weight or more. More preferably.

  Examples of the resin having an alicyclic structure include a ring-opening polymer or a ring-opening copolymer of a norbornene monomer or a hydrogenated product thereof, an addition polymer or an addition copolymer of a norbornene monomer, or Those hydrogenated products, polymers of monocyclic olefin monomers or hydrogenated products thereof, polymers of cyclic conjugated diene monomers or hydrogenated products thereof, vinyl alicyclic hydrocarbon monomers Or a hydrogenated product thereof, a polymer of a vinyl aromatic hydrocarbon monomer, or a hydrogenated product of an unsaturated bond part containing an aromatic ring of the copolymer. Among these, hydrogenated products of norbornene-based monomer polymers and hydrogenated products of unsaturated bonds containing aromatic rings of vinyl aromatic hydrocarbon-based monomer polymers have mechanical strength and heat resistance. Since it is excellent in property, it can be used especially suitably. The methacrylic resin is excellent in transparency, tough and hardly cracked, so that it can be suitably used. Examples of the methacrylic resin include a methacrylic resin molding material containing 80% or more of a methyl methacrylate polymer defined in JIS K6717. Among the methacrylic resins specified in this standard, methacrylic resins having a specified classification code 100-120 having a Vicat softening point temperature of 96 to 100 ° C. and a melt flow rate of 8 to 16 have suitable fluidity and strength, and thus are suitable. Can be used.

  An antioxidant can be added to the molding material used in the present embodiment in order to prevent oxidative degradation and thermal degradation during molding. Moreover, in order to improve the light resistance etc. of a molded article, a light resistance stabilizer can be added. Examples of the antioxidant include a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant. These antioxidants can be used individually by 1 type, or can be used in combination of 2 or more type. Among these, phenolic antioxidants, particularly alkyl-substituted antioxidants can be suitably used. The addition amount of the antioxidant is preferably 0.01 to 2 parts by weight and more preferably 0.02 to 1 part by weight with respect to 100 parts by weight of the resin component.

  Examples of the light resistance stabilizer include hindered amine light resistance stabilizer (HALS) and benzoate light resistance stabilizer. These light-resistant stabilizers can be used alone or in combination of two or more. Among these, hindered amine light resistance stabilizers can be particularly preferably used. The addition amount of the light resistance stabilizer is preferably 0.01 to 2 parts by weight, more preferably 0.02 to 1 part by weight, with respect to 100 parts by weight of the resin component. More preferably, it is 5 parts by weight.

  If necessary, other additives can be added to the molding material. Other additives include, for example, stabilizers such as heat stabilizers, ultraviolet absorbers and near infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments; antistatic agents, light Examples include a diffusing agent.

  The light guide plate 13 is formed of a rectangular plate body, and the dimensions in the X direction and the Y direction are set according to the size of the effective surface of the liquid crystal panel of the liquid crystal display device in which the light guide plate 13 is used. The dimension (thickness) in the Z direction of the light guide plate 13 can be set to h1 = 1.0 mm, for example. Here, the thickness of the light guide plate 13 is usually 0.02 mm or more, preferably 0.1 mm or more, and usually 10 mm or less, preferably 5 mm or less. As the refractive index of the light guide plate 13, for example, a refractive index of 1.533 (critical angle 40.7 °) can be used.

  The light guide plate 13 includes an incident end portion 14 into which light from the light source 12 is incident, and a light guide plate main body 15 that guides the light incident from the incident end portion 14 and emits the light. In this embodiment, it is assumed that the incident end portion 14 and the light guide plate main body 15 are manufactured by simultaneous integral molding using the same material. However, the incident end 14 and the light guide plate main body 15 may be formed as separate bodies using the same or different materials, and may be integrated by bonding or the like. When the incident end portion 14 and the light guide plate main body 15 are respectively formed as separate bodies using the same or different materials and integrated by adhesion or the like, it is preferable to use the same water absorption rate. If the water absorption rate is different, warping and bending occur with moisture absorption, and this is to suppress this. The light guide plate body 15 preferably has a refractive index higher than that of the incident end 14. This is because refraction occurs at these interfaces and the light utilization efficiency may be reduced.

  The light guide plate main body 15 has a back surface 16 that reflects light propagating in the light guide plate main body 15 and a light that is opposed to the back surface 16 and is reflected or not reflected by the back surface 16 and propagates in the light guide plate main body 15. Is provided. In this embodiment, the back surface 16 and the emission surface 17 (the respective average surfaces when the back surface 16 and the emission surface 17 are uneven) are surfaces substantially parallel to the XY plane.

  In this embodiment, the back surface 16 of the light guide plate 13 is a reflective surface composed of a uniform plane. The back surface 16 may be configured such that a reflective metal is deposited on the back surface of the resin plate constituting the light guide plate 13 or a white scattering plate (white reflection plate) is disposed. Note that the back surface 16 may be an inclined surface that is inclined with respect to the XY plane so that the dimension with respect to the emission surface 17 gradually decreases from the side closer to the incident end portion 14 toward the side farther from the side.

  In addition, the back surface 16 may be provided with unevenness such as a row in order to emit light propagating through the light guide plate body 15 with high efficiency and make the emitted light uniform. As the row in this case, for example, the longitudinal direction is set along the Y direction of the back surface 16, and the row (prism row) is formed by arranging a plurality of triangular stripes in the X direction. ) Can be used. Similarly, the longitudinal direction of the back surface 16 may be set along the X direction, and a strip (prism strip) formed by arranging a plurality of triangular strips in the Y direction may be used. Moreover, you may use the thing which mutually differs in the inclination | tilt angle with respect to XY plane of a row | line | column of a row | line | column, the pitch of the arrangement | sequence of a row | line | column, height, etc. Furthermore, adjacent strips may not have the same shape, and the shape of the strip is not limited to a triangular cross section, and may be another polygonal shape or a curved shape such as a semicircular arc or an elliptical arc. These may be mixed. Further, the row is not limited to being formed uniformly over the back surface 16, but may be formed in the middle or divided in the middle of the row. Further, it may be slightly oblique with respect to the Y direction.

  The back surface 16 may be an irregular rough surface (a surface on which minute irregularities are randomly formed). Further, it may be formed in a dot shape, or may be formed by arranging a plurality of projections or depressions having the same or different shapes in an array or discretely. In this case, a spherical shape, a conical shape, a polygonal pyramid shape, or the like can be adopted as the shape of the protrusion or the depression. Alternatively, the shape may be formed by printing with white ink or metal vapor deposition.

  Further, from the viewpoint of preventing the surface from being scratched, a convex structure is preferable regardless of whether it is linear or dotted. In this case, the height of the protrusion is preferably 1 μm or more from the same viewpoint, and more preferably 5 μm or more.

  The light emission surface 17 of the light guide plate main body 15 is a surface that emits light propagated in the light guide plate main body 15, and is a uniform flat surface in this embodiment. In order to emit light propagating into the light guide plate main body 15 with high efficiency and make the emitted light uniform, unevenness such as a row may be arranged. As a row in this case, for example, the longitudinal direction is set along the Y direction of the emission surface 17, and a row (prism strip) formed by arranging a plurality of triangular cross-sections in the X direction. Column). Similarly, the longitudinal direction may be set along the X direction of the emission surface 17, and a strip (prism strip) formed by arranging a plurality of triangular strips in the Y direction may be used. . The apex angle of the line and the inclination angle of the pair of inclined surfaces constituting the line with respect to the XY plane, the pitch of the array of the lines, the height, and the like may be different from each other. Furthermore, adjacent strips may not have the same shape, and the shape of the strip is not limited to a triangular cross section, and may be another polygonal shape or a curved shape such as a semicircular arc or an elliptical arc. These may be mixed. Further, the row is not limited to being formed uniformly over the emission surface 17, but may be formed by being divided in the middle and arranged in an array or discretely. Further, it may be slightly oblique with respect to the Y direction.

  The emission surface 17 may be an irregular rough surface (a surface on which minute irregularities are randomly formed). Further, it may be formed in a dot shape, or may be formed by arranging a plurality of projections or depressions having the same or different shapes in an array or discretely. In this case, a spherical shape, a conical shape, a polygonal pyramid shape, or the like can be adopted as the shape of the protrusion or the depression. Alternatively, the shape may be formed by printing with white ink or metal vapor deposition.

  Further, from the viewpoint of preventing the surface from being scratched, a convex structure is preferable regardless of whether it is linear or dotted. In this case, the height of the protrusion is preferably 1 μm or more from the same viewpoint, and more preferably 5 μm or more.

  In the manufacture of the light guide plate 13 of the present embodiment, there is no particular limitation on the method of forming the specific shape of the protrusion on the surface. For example, when forming a prism row, it can be formed on the surface of a flat light guide plate, or the prism row can be formed simultaneously with the formation of the light guide plate. The method for forming the prism array on the surface of the flat light guide plate is not particularly limited. For example, the method can be performed by cutting using a tool capable of forming a linear prism having a desired shape, or a photo-curing resin. Can be applied and cured in a state where a mold having a desired shape is transferred. When the light guide plate is produced by extrusion molding and the prism rows are formed at the same time, the shape of the prism rows can be extrude using a deformed die having a desired prism row shape, or the prism rows can be formed by embossing after extrusion. It can also be formed. When the light guide plate is produced by casting and the prism rows are formed at the same time, a casting mold capable of forming a desired prism row shape can be used. When the light guide plate is manufactured by injection molding and the prism rows are formed at the same time, a mold capable of forming a desired prism row shape can be used. Die shape transfer to photo-curing resin, extrusion process using odd-shaped die, embossing, casting, or injection molding, the mold used to form the prism row was a tool that can form the desired linear prism It can be obtained by cutting a metal member of a mold or electroforming on a member having a desired shape.

  On the exit surface 17 side of the light guide plate 13, a light diffusion sheet is sandwiched between air layers so that the illumination light from the surface light source device 11 is uniform and uniform, and a prism sheet or the like so as to increase the luminance. It is preferable that the optical sheet is disposed. As an optical sheet, a transparent resin, a plate-like body in which a light diffusing agent or other additives are added to a transparent resin, or a plate-like body formed with a pattern such as a plurality of protrusions or rows on one or both surfaces, etc. Can be used.

  The incident end 14 of the light guide plate body 13 includes an incident surface 18 on which light emitted from the light source 12 is incident, an inclined surface 19, and an interface 20 that is a boundary between the light guide plate body 15. The incident surface 18 is a flat surface substantially parallel to the XY plane, and is flush with the back surface 16 of the light guide plate body 15. The inclined surface 19 is a uniform plane inclined at an angle that is greater than the angle at which the angle with respect to the XY plane is totally reflected with respect to the parallel rays in the Z direction, and is emitted from the light source 12 in the approximately + Z direction. This is a reflecting surface that reflects the light incident through the light guide plate body 15 side. In this embodiment, the angle of the inclined surface with respect to the XY plane is 45 °. The inclined surface 19 can be a reflective surface formed by depositing a reflective material such as silver. However, in this embodiment, the resin plate constituting the light guide plate 13 is exposed because it can function substantially as a reflective surface due to the relationship between the incident angle of light incident on the inclined surface 19 and the refractive index of the light guide plate. The exposed surface.

  As a result, as indicated by the one-dot chain line arrow in the drawing, the light emitted from the light source 12 in the + Z direction is introduced into the incident end portion 14 via the incident surface 18 and reflected by the inclined surface 19. It is guided to the light guide plate main body 15 side through the interface 20. The light guided into the light guide plate body 15 is emitted through the emission surface 17 while being appropriately reflected or scattered within the light guide plate body 15.

  By the way, the light guide plate 13 made of resin undergoes a dimensional change (elongation or warpage) due to moisture absorption, and particularly when the size of the light guide plate 13 is large (for example, 40 inches), the light source 12 and the incident end 14 are caused by the dimensional change. The relative positional relationship with the light changes, and the light use efficiency decreases. Therefore, the water absorption rate of the light guide plate 13 is preferably set to 0.25% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. In this embodiment, the water absorption is set to 0.01%. In addition, the water absorption rate in the specification of the present application is a desiccator after drying a test piece having a disk shape of 50 mm in diameter or a square of 50 mm on a side at 50 ° C. for 24 hours in accordance with JIS K7209 A method. It can be calculated from the weight increase when it is allowed to cool and then immersed in water at 23 ° C. for 24 hours.

  With the surface light source device 11 configured as described above, a surface light source device that illuminates the entire area of the liquid crystal panel as the object to be illuminated can be configured. In addition, the surface light source device 11 configured as described above is configured as a single unit, and a plurality of units are appropriately arranged to configure a surface light source device that illuminates the entire area of the liquid crystal panel as the object to be illuminated. You can also.

  In the liquid crystal display device, the above-described surface light source device 11 is provided on the back side of a liquid crystal panel in which an alignment film, a transparent electrode, a glass plate, a color filter, a polarizing plate, and the like are appropriately stacked with a liquid crystal layer interposed therebetween. Each is configured to be fixed to a housing or the like so as to be arranged in a positional relationship.

  As described above, the half-value angle in the Y direction of the light source 12 (LED) is set to be 45 ° or less based on the simulation result shown in FIG. In FIG. 7, the horizontal axis represents the half-value angle (°) in the Y direction, and the vertical axis represents the light utilization efficiency (%). The light utilization efficiency is the ratio of the total luminous flux emitted from the light source 12 and the total luminous flux emitted from the emission surface 17. This simulation result is calculated while appropriately selecting a plurality of light sources (half-value angles 0 to 120 °) having mutually different half-value angles in the configuration of FIG.

  Referring to the figure, as the half-value angle decreases from 120 °, the light utilization efficiency increases with a relatively small slope, and as the inflection point is around 45 °, the light utilization efficiency increases relatively as it decreases from 45 °. It can be seen that the slope is rising. Therefore, by setting the half-value angle to a value smaller than 45 °, high light utilization efficiency can be realized.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, about the component substantially the same as FIG. 1 which concerns on 1st Embodiment mentioned above, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the surface light source device 11 of the first embodiment described above, the incident end portion 14 includes the inclined surface 19 formed of a uniform plane. In the surface light source device 21 of the second embodiment, the incident end portion 22 is The difference is that the section is provided with a divided inclined portion 23 having a saw-tooth shape. The division | segmentation inclination part 23 arranges the some division | segmentation inclination surface 24a in a Y direction, and these are each connected by the connection surface 24b, and is comprised. The angle of inclination of each divided inclined surface 24a with respect to the XY plane can be 45 °, for example, and the angle of inclination of the connecting surface 24b with respect to the XY plane can be 90 ° (ie, substantially in the ZX plane). Parallel). The divided inclined surface 24a and the connection surface 24b are exposed surfaces from which the resin plate constituting the light guide plate 13 is exposed.

  The dimension in the Y direction and the Z direction of the portion constituted by the divided inclined surface 24a and the connecting surface 24b can be set to 0.1 mm, for example. For example, the dimension of the light source 12 in the Y direction can be set to d2 = 1.0 mm, and the dimension (thickness) of the light guide plate 13 in the Z direction can be set to h2 = 0.5 mm.

  As a result, as indicated by the one-dot chain line arrow in the drawing, the light emitted from the light source 12 in the + Z direction is introduced into the incident end 22 through the incident surface 18, and the divided inclined surface of the divided inclined portion 23. A part of the light is reflected and guided directly to the light guide plate body 15 side by 24a, and the other part is once emitted from the corresponding connection surface 24b and refracted and incident on the adjacent divided inclined surface 24a. It is guided to the optical plate body 15 side. The light guided to the light guide plate body 15 is emitted through the emission surface 17 while being appropriately reflected or scattered in the light guide plate body 15. Others are the same as in the first embodiment described above.

  In the second embodiment, the angles and dimensions (dimension in the Y direction and dimension in the Z direction) of each of the divided inclined surface 24a and the connection surface 24b with respect to the XY plane are the thickness of the light guide plate 13 (in the Z direction). Dimensions), the dimension of the light guide plate 13 in the Y direction, the refractive index of the light guide plate 13, and the like.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the component substantially the same as FIGS. 1-2 concerning the 1st-2nd embodiment mentioned above, and the description is abbreviate | omitted.

  In the surface light source device 21 of the second embodiment described above, the incident end portion 22 includes the divided inclined portion 23 in which a plurality of divided inclined surfaces 24a are arranged in the Y direction. On the other hand, the incident end portion 32 of the surface light source device 31 of the third embodiment includes a divided inclined portion 33 in which the arrangement of the divided inclined surfaces 34a is different from the divided inclined surface 24a of the second embodiment described above. The point is different. In other words, the positions of the plurality of divided inclined surfaces 34a of the divided inclined portion 33 are set so that part or all of them are different not only in the Y direction but also in the Z direction. Each of the divided inclined surfaces 34a is arranged so as to be displaced in the + Z direction as a part or all of it goes in the + Y direction, that is, away from the incident surface 18.

  The inclination angle of each divided inclined surface 34a with respect to the XY plane can be set to 45 °, for example, as in the second embodiment described above. Similarly, the inclination angle of the connection surface 34b with respect to the XY plane can be set to 90 ° (ie, substantially parallel to the ZX plane), for example. Similarly to the second embodiment described above, the divided inclined surface 34a and the connecting surface 34b are exposed surfaces from which the resin plate constituting the light guide plate 13 is exposed.

  The dimensions in the Y direction and the Z direction of the portion constituted by the divided inclined surface 34a and the connecting surface 34b are, for example, such that the dimension m3 is 1/5 of the thickness h3 of the light guide plate 13 as shown in FIG. Can be set. For example, the dimension in the Y direction of the light source 12 can be d2 = 1.0 mm, and the dimension (thickness) in the Z direction of the light guide plate 13 can be h3 = 0.5 mm (accordingly, m3 = 0.1 mm). .

  As a result, as indicated by a one-dot chain line arrow in the drawing, light emitted from the light source 12 in the + Z direction is introduced into the incident end portion 32 via the incident surface 18, and the divided inclined surface of the divided inclined portion 33. A part of the light is reflected and guided directly to the light guide plate main body 15 side by 34a, and the other part is once emitted from the corresponding connecting surface 34b and refracted and incident on the adjacent divided inclined surface 34a. It is guided to the optical plate body 15 side. The light guided to the light guide plate body 15 is emitted through the emission surface 17 while being appropriately reflected or scattered in the light guide plate body 15. Others are the same as those of the first and second embodiments described above.

  According to the third embodiment, since the position of a part of the divided inclined surface 34a is different in the Z direction, the light once emitted from the connecting surface 34b and refracted and incident from the adjacent divided inclined surface 34a is As compared with the second embodiment, the amount of light reflected by the divided inclined surface 34a and directly guided to the light guide plate body 15 is increased. Therefore, the light loss is smaller than in the second embodiment described above, and the light utilization efficiency can be increased.

  In the third embodiment, the angles and dimensions (Y-direction dimensions and Z-direction dimensions) of the divided inclined surface 34a and the connection surface 34b with respect to the XY plane are the thicknesses of the light guide plate 13 (Z direction). )), The dimension of the light guide plate 13 in the Y direction, the refractive index of the light guide plate 13, and the like.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the component substantially the same as FIGS. 1-3 concerning 1st-3rd embodiment mentioned above, and the description is abbreviate | omitted.

  In the surface light source device 11 of the first embodiment described above, the incident end portion 14 is provided with the inclined surface 19 having a uniform plane. In the surface light source device 41 of the fourth embodiment, the incident end portion 42 is The difference is that a divided inclined portion 43 is provided. The divided inclined portion 43 is configured by sequentially connecting a plurality of divided inclined surfaces 44a, 44b, and 44c having different inclination angles with respect to the XY plane.

  As the inclination angles φ1, φ2, and φ3 of the divided inclined surfaces 44a, 44b, and 44c with respect to the XY plane, the inclined angle φ1 of the divided inclined surface 44a is larger than the inclined angle φ2 of the intermediate divided inclined surface 44b, The inclination angle φ3 of the divided inclined surface 44c is preferably set to a value smaller than the inclination angle φ2 of the intermediate divided inclined surface 44b. It is preferable that the inclination angles φ1, φ2, and φ3 of each of the divided inclined surfaces 44a, 44b, and 44c are equal to or greater than an angle that causes total reflection with respect to parallel rays in the Z direction. For example, the inclined angle of the divided inclined surface 44a with respect to the XY plane is φ1 = 50 °, the inclined angle of the divided inclined surface 44b with respect to the XY plane is φ2 = 45 °, and the inclined angle of the divided inclined surface 44c with respect to the XY plane. Can be φ3 = 41 °. The divided inclined surfaces 44a, 44b, 44c may be total reflection surfaces by metal vapor deposition or the like, or may be exposed surfaces from which the resin plate constituting the light guide plate 13 is exposed, as in the first embodiment described above. is there.

  For example, the dimension in the Y direction of the light source 12 can be set to d4 = 1.0 mm, and the dimension (thickness) in the Z direction of the light guide plate 13 can be set to h4 = 1.0 mm.

  As a result, as indicated by the one-dot chain line arrow in the drawing, the light emitted from the light source 12 in the + Z direction is introduced into the incident end portion 42 via the incident surface 18, and the divided inclined surface of the divided inclined portion 43. It is reflected by 44a, 44b, 44c and guided to the light guide plate body 15 side. The light guided to the light guide plate body 15 is emitted through the emission surface 17 while being appropriately reflected or scattered in the light guide plate body 15. Others are the same as in the first embodiment described above.

  In addition, the angle and dimension (dimension in the Y direction, dimension in the Z direction) of each of the divided inclined surfaces 44a, 44b, and 44c with respect to the XY plane are the thickness of the light guide plate 13 (dimension in the Z direction), and the light guide plate 13. The Y direction dimension, the refractive index of the light guide plate 13 and the like can be changed as appropriate.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG. In addition, about the component substantially the same as FIGS. 1-4 based on 1st-4th embodiment mentioned above, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the surface light source device 51 of the fifth embodiment, the configuration of the third embodiment described above is changed so as to be compatible with a thinner light guide plate. That is, the incident end portion 52 of the fifth embodiment includes an introduction portion 52a and a transmission portion 52b. The introduction portion 52a has the same configuration as the configuration of the incident end portion 32 of the third embodiment described above, and includes a divided inclined portion 33 having a plurality of divided inclined surfaces 34a and a plurality of connecting surfaces 34b.

  The transmission part 52b is a part that connects the introduction part 52a and the light guide plate body 13, and is located on the most + Y side of the introduction part 52a and the bottom surface 55 that is integral with the incident surface 18 and the back surface 16 of the light guide plate body 15. A light guide inclined surface 56 that connects the divided inclined surface 34 a and the emission surface 17 of the light guide plate body 13 is provided. The bottom surface 55 and the light guide slope 56 are total reflection surfaces, and can be formed, for example, by vapor-depositing a metal material such as silver on the surface. The inclination angle of the light guide slope 56 with respect to the XY plane is preferably 45 ° or less.

  There is no restriction | limiting in particular as a method of forming the division | segmentation inclined surface 34a in the incident end part 52, For example, it can be by the cutting process using the tool which can form the division | segmentation inclined surface 34a of a desired shape, or photocurable resin is used. It can also be applied and cured in a state where a mold having a desired shape is transferred. A portion corresponding to the upper portion 58 of the incident end portion 52 may be separately formed and then bonded to a similar resin plate. When the upper part 58 of the incident end part 52 and the light guide plate main body 15 (lower part 57 of the incident end part) are separately formed and integrated later, it is preferable to use the same water absorption rate. If the water absorption rate is different, warping and bending occur with moisture absorption, and this is to suppress this. In addition, it is preferable to use a refractive index of the upper portion 58 that is higher than that of the lower portion 57. This is because refraction occurs at these interfaces and the light utilization efficiency may be reduced.

  The height (dimension in the Z direction) of the upper portion 58 of the incident end 52 can be the same as the height m3 × 5 (= h3) of the incident end 32 of the third embodiment described above. m5 = 0.5 mm can be set. The thickness of the light guide plate main body 13 can be made considerably thinner than the thickness of the light guide plate main body 15 of the third embodiment described above. For example, h5 = 0.2 mm. In this case, the height of the incident end 52 is h5 + m5 = 0.7 mm.

  The inclination angle of the light guide inclined surface 56 with respect to the XY plane is preferably set to 45 ° or less in order to guide light transmitted from the introduction portion 52a to the transmission portion 52b to the light guide plate body 15 with high efficiency. It is more preferable to set the following value, and 22.5 ° or less is more preferable. By setting such an inclination angle, it is possible to suppress the light that is emitted from the transmission unit 52b out of the light transmitted from the introduction unit 52a to the transmission unit 52b, and to prevent a decrease in light utilization efficiency. The inclination angle of the light guide slope 56 with respect to the XY plane can be set to 14.04 °, for example, when the dimension in the Y direction of the transmission portion 52b is 2.0 mm.

  As a result, as indicated by the one-dot chain line arrow in the drawing, the light emitted from the light source 12 in the + Z direction is introduced into the introducing portion 52a of the incident end portion 52 via the incident surface 18, and the divided inclined portion 33. Part of the divided inclined surface 34a is reflected and guided directly to the transmitting portion 52b side, and the other part is once emitted from the corresponding connecting surface 34b and refracted by the adjacent divided inclined surface 34a. Then, it is guided to the transmission part 52b. The light guided to the transmission part 52 b is appropriately reflected between the light guide slope 56 and the bottom surface 55 and guided to the light guide plate body 15 through the interface 20. The light guided to the light guide plate body 15 is emitted through the emission surface 17 while being appropriately reflected or scattered in the light guide plate body 15. Others are the same as the first to fourth embodiments described above.

  According to the fifth embodiment, since the thickness of the light guide plate body 15 can be reduced, the surface light source device can be thinned, and the liquid crystal display device can be thinned.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG. In addition, about the component substantially the same as FIGS. 1-5 based on 1st-5th embodiment mentioned above, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The surface light source device 61 of the sixth embodiment is obtained by changing the configuration of the fifth embodiment described above. That is, in the fifth embodiment described above, the inclination angles of the divided inclined surfaces 34a of the divided inclined portions 33 with respect to the XY plane are all the same angle (for example, 45 °). On the other hand, in the sixth embodiment, some or all of the inclined angles of each divided inclined surface 34a are set to different values.

  Although not particularly limited, the inclination angle of each divided inclined surface 34a with respect to the XY plane is P1 in the most divided inclined surface 34a on the -Y side, P5 in the divided inclined surface 34a on the most + Y side in FIG. The divided inclined surfaces 34a are P2, P3, P4, respectively. For example, the inclined angles of the intermediate divided inclined surfaces P2 to P4 are the same, and the inclined angle of the divided inclined surface P1 is the same as that of the intermediate divided inclined surfaces P2 to P4. The inclination angle of the divided inclined surface P5 can be set to a value smaller than the inclination angles of the intermediate divided inclined surfaces P2 to P4. It is preferable that the inclination angles of the divided inclined surfaces P1 to P5 are equal to or greater than the angle at which total reflection is performed with respect to parallel rays in the Z direction. As an example, the divided inclined surfaces P2 to P4 can be set to 45 °, the divided inclined surface P1 can be set to 50 °, and the divided inclined surface P5 can be set to 41 °.

  It is thin by appropriately optimizing the inclination angles of the divided inclined surfaces 34a (P1 to P5) and the light guide slope 56 in relation to the thickness of the light guide plate body 15 (for example, h6 = 0.2 mm). Light can be guided to the light guide plate body 15 with high efficiency. Others are the same as the first to fifth embodiments described above.

  Next, examples of the present invention will be described with reference to Table 1. An optical model is created for each of the surface light source devices 11, 21, 31, 41, 51, 61 shown in FIGS. 1 to 6, and the light use efficiency (%) is calculated by software simulation. As the light guide plate material, ZNR (thermoplastic alicyclic structure-containing resin ZEONOR1420 (trade name, manufactured by Nippon Zeon Co., Ltd.), refractive index 1.533, critical angle 40.7 degrees, water absorption 0.01%) is used. To do.

(Example 1)
The light guide plate has the configuration shown in FIG. The light source size (dimension in the Y direction of the light source 12) was set to d1 = 1.0 mm, and the light source half-value angle (half-value full angle in the Y direction of the LEDs constituting the light source 12) was set to 0 ° (parallel light). The thickness of the light guide plate (dimension in the Z direction of the light guide plate main body 15) was h1 = 1.0 mm. The inclined surface angle (inclined angle of the inclined surface 19 with respect to the XY plane) was 45 °. The dimension of the inclined surface 19 in the Y direction was 1.0 mm, which is the same as the light source size. As a result of the simulation, the light utilization efficiency was 98.5%.

(Example 2)
Except that the light source half-value angle was set to 15 °, it was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 71.9%.

(Example 3)
The same as Example 1 described above except that the light source half-value angle was set to 35 °. As a result of the simulation, the light utilization efficiency was 60.3%.

Example 4
The light guide plate has the configuration shown in FIG. The thickness of the light guide plate was h2 = 0.5 mm. The inclined surface angle (the angle of each divided inclined surface 24a with respect to the XY plane) was 45 °. The angle of the connecting surface 24b with respect to the XY plane was 90 °, and the dimension of each divided inclined surface 24a in the Y direction was 0.1 mm. The rest was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 70.6%.

(Example 5)
The shape of the light guide plate is the same as that shown in FIG. The thickness of the light guide plate was h3 = 0.5 mm. The inclined surface angle (angle of each divided inclined surface 34a with respect to the XY plane) was 45 °. The angle of the connection surface 34b with respect to the XY plane was 90 °, and the dimension of each divided inclined surface 34a in the Y direction was 0.2 mm. As for the arrangement of the divided inclined surfaces 34a in the Z direction, the fourth to the fourth divided inclined surface 34a to the fourth divided inclined surface 34a are sequentially arranged at positions shifted by m3 = 0.1 mm, and only the divided inclined surface 34a closest to the + Y side is arranged. Was arranged at the same position as the divided inclined surface 34a adjacent thereto. The rest was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 93.9%.

(Example 6)
The light guide plate has the configuration shown in FIG. The thickness of the light guide plate was h4 = 1.0 mm. The inclined surface angles (inclined angles of the divided inclined surfaces 44a, 44b, and 44c) were φ1 = 50 °, φ2 = 45 °, and φ3 = 41 °. The dimension of each divided inclined surface 44a, 44b, 44c was 0.333 mm. The rest was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 76.5%.

(Example 7)
The light guide plate has the configuration shown in FIG. The thickness of the light guide plate was h5 = 0.2 mm. The inclined surface angle (inclination angle of each divided inclined surface 34a with respect to the XY plane) was 45 °. The angle of the connection surface 34b with respect to the XY plane was 90 °, and the dimension of each divided inclined surface 34a in the Y direction was 0.2 mm. As for the arrangement of the divided inclined surfaces 34a in the Z direction, the fourth to the fourth divided inclined surface 34a to the fourth divided inclined surface 34a are sequentially arranged at positions shifted by 0.1 mm, and only the most + Y side divided inclined surface 34a is arranged. It arrange | positions in the same position as the division | segmentation inclined surface 34a adjacent to. The dimension in the Z direction of the upper part 58 of the incident end 52 was set to m5 = 0.5 mm, and the dimension in the Z direction of the lower part 57 was set to 0.2 mm, which is the same as the light guide plate thickness h5. The angle of the light guide slope 56 was 14.04 ° with respect to the XY plane, and the dimension of the bottom surface 55 in the Y direction was 2.0 mm. The rest was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 72.1%.

(Example 8)
The light guide plate has the configuration shown in FIG. The thickness of the light guide plate was h6 = 0.2 mm. The inclined surface angles (angles of the divided inclined surfaces 34a (P1 to P5) with respect to the XY plane) were set to P1 = 50 °, P2 to P3 = 45 °, and P5 = 41 °. The dimension indicated by reference numeral m6 in the figure was 0.5 mm. Since the inclination angle of the divided inclined surface P1 is 50 °, the position in the Z direction on the + Y side of the divided inclined surface P1 is set to be 0.04 mm above the corresponding position in Example 7 (+ Z direction side). ing. Further, since the inclination angle of the divided inclined surface P5 is 41 °, the position in the Z direction on the −Y side of the divided inclined surface P5 is 0.02 mm above the corresponding position in Example 7 (+ Z direction side). Is set to The rest was the same as Example 7 described above. As a result of the simulation, the light utilization efficiency was 80.1%.

(Comparative Example 1)
Except that the light source half-value angle (half-value full angle in the Y direction of the LED constituting the light source 12) was set to 55 °, it was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 56.5%.

(Comparative Example 2)
Except that the light source half-value angle (half-value full angle in the Y direction of the LED constituting the light source 12) was set to 90 °, it was the same as Example 1 described above. As a result of the simulation, the light utilization efficiency was 54.4%.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the embodiment described above is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

11, 21, 31, 41, 51, 61 ... surface light source device 12 ... light source 13 ... light guide plate 14, 22, 32, 42, 52, 62 ... incident end 15 ... light guide plate body 16 ... back surface 17 ... exit surface 18 ... Incident surface 19 ... Inclined surfaces 24a, 34a, 44a, 44b, 44c ... Divided inclined surfaces 24b, 34b ... Connection surface 52a ... Introducing portion 52b ... Transmitting portion 56 ... Light guiding slope

Claims (7)

A surface light source device comprising a light source and a light guide plate made of a plate-like body that guides light from the light source,
The light guide plate is integrally disposed on a light guide plate body having a back surface that reflects light propagating in the interior and an exit surface that emits light propagating in the interior, and on a side portion of the light guide plate body, and the light source And an incident end where light from is incident,
The incident end is inclined with respect to the incident surface so as to reflect an incident surface that receives light from the light source and the light from the light source that is incident through the incident surface toward the light guide plate body side. An inclined surface,
The surface light source device, wherein the light source is set to have a light distribution characteristic of a full width at half maximum of 45 ° or less.   The surface light source device according to claim 1, wherein a water absorption rate of the light guide plate is set to 0.25% or less.   The surface light source device according to claim 1, wherein the inclined surface includes a plurality of divided inclined surfaces having substantially the same or different inclination angles.   4. The surface light source device according to claim 3, wherein a part or all of the divided inclined surfaces are arranged such that a separation dimension with respect to the incident surface increases from the outside to the inside of the light guide plate.   5. The surface light source device according to claim 3, wherein a part or all of the divided inclined surfaces are arranged so that an inclination angle with respect to the incident surface becomes smaller from an outer side to an inner side of the light guide plate.   The incident end is set to a value whose thickness is larger than the thickness of the light guide plate body, and the light guide slope connecting the edge of the inclined surface on the light guide plate body side and the edge of the exit surface The surface light source device according to any one of claims 1 to 5.   A liquid crystal display device provided with a liquid crystal panel and the surface light source device as described in any one of Claims 1-6.

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