KR102021909B1 - Light guide panel, surface light source apparatus comprising light guide panel and flat panel display comprising surface light source apparatus - Google Patents

Abstract

A light guide plate and a surface light source device including the same are disclosed. The light guide plate according to the exemplary embodiment of the present invention includes a light guide layer having a light incident surface, a polarization separation layer that emits polarized light from light emitted from the light guide layer, and a plurality of fibers and a support thereof, which are incident on the light guide layer. And a light homogenization layer for diffusing and scattering light into the light guide layer. The polarization separation layer may include a plurality of first fibers having birefringence and an isotropic first support for supporting the first fibers. The refractive index of the first support may match at least one of two refractive indices of the first fiber. The optical homogenization layer may include a plurality of second fibers having birefringence and an isotropic second support for supporting the second fibers.

Description

A light guide plate, a surface light source device having the same, and a flat panel display having the same: a light guide panel, surface light source apparatus comprising light guide panel and flat panel display comprising surface light source apparatus

One embodiment of the present invention relates to a display device, and more particularly, to a light guide plate, a surface light source device having the same, and a flat panel display including the surface light source device.

Liquid crystal display devices used in PCs, computer monitors, video cameras, liquid crystal televisions (LCD-TVs), mobile communication terminals, etc., are light-receiving display devices that do not have their own luminescence capability. Is displayed. Therefore, a backlight is provided on the back of the liquid crystal display as a surface light source device.

In the liquid crystal display device, the light emitted from the surface light source device passes through the liquid crystal cell in which the liquid crystal layer is disposed between a pair of polarizing plates having a transmission axis orthogonal to each other. An image is displayed by the light which transmitted the liquid crystal cell electrically ON / OFF.

As a polarizing plate, a polyvinyl alcohol film colored with iodine and uniaxially stretched is usually used as a polarizer, and a protective film such as a triacetylcellulose film, a coating layer made of acrylic resin, or the like on one or both surfaces of the polarizer, norbornene or polycarbonate, etc. The absorption type polarizing plate which arrange | positioned the phase difference film of is used.

However, such an absorption type polarizing plate has the property of transmitting only light in the transmission axis direction of the polarizing plate and absorbing the light of the remaining components. In principle, the light utilization efficiency (light transmittance) does not exceed 50%. In addition, considering that the reflectance of the inner surface was 4%, the maximum was 46%. Therefore, the effective utilization of the backlight and the improvement of the brightness are the propositions of the liquid crystal display device in achieving low power consumption.

As one of the methods of solving this, the reflection type polarizing plate using the optical reflection interference characteristic is known. Reflective polarizers transmit polarized light that reflects specific polarized light and exhibits opposite properties.

Specifically, by aligning the light transmitted through the reflective polarizing plate to transmit the polarizing plate as linearly polarized light, it transmits only the polarization in the transmission axis direction and at the same time reflects and reuses the polarized light absorbed by the absorption polarizing plate. Thereby, the utilization efficiency of the light emitted from a backlight can be improved.

One example of the reflective polarizing plate is a dual luminance rising film (DBEF) composed of alternating laminated films of a refractive index isotropic layer and a refractive index anisotropic layer. However, DBEF has a problem in that manufacturing cost is high because it is necessary to laminate hundreds of polymer films as a whole in order to secure polarization characteristics over the visible light region and precise control is required.

As a method of improving the light utilization efficiency and the polarization separation ability at a lower cost, a technique using a polarization sensitive scattering element (PSSE) has attracted attention. For example, Prior Art 1 (Japanese Patent Laid-Open No. 11-502036) scatters polarized light in the orthogonal direction and the transmission axis behind by PSSE to separate the polarized light, and polarizes the back scattered light by the λ / 4 plate. A technique of inverting and reusing a state is disclosed.

In addition, Prior Art 2 (Japanese Patent Laid-Open No. 2009-047802) discloses a reflective polarizing plate using a birefringent body made of a birefringent fiber as a PSSE. In this method, the layer (polarization layer A) in which the refractive index in the cross-sectional direction of the birefringent body is matched with the refractive index of the supporting medium (polarizing layer A), the refractive index in the longitudinal direction of the birefringent body (normal ray refractive index) and the refractive index of the supporting medium are matched. The laminated layer (polarizing layer B) is laminated so as to cross the birefringent array direction. In this way, the polarization separation ability with respect to obliquely incident light or diffused light is improved.

In addition, Prior Art 3 (Japanese Patent Laid-Open No. 2006-517720) discloses a method in which an isotropic resin layer containing birefringent fibers as PSSE is integrated with a light guide plate to scatter only one polarized light to be emitted to the outside and to improve polarization separation efficiency.

On the other hand, in achieving low power consumption of a surface light source device, a backlight using an LED having excellent long life and power saving effect as a light source is mainstream.

One embodiment of the present invention provides a light guide plate that suppresses luminance unevenness even when discontinuous light sources are disposed on a cross section of the light guide plate while improving polarization separation efficiency.

One embodiment of the present invention provides a surface light source device including such a light guide plate.

One embodiment of the present invention provides a flat panel display having such a surface light source device as a light source device.

The light guide plate according to the exemplary embodiment of the present invention includes a light guide layer having a light incident surface, a polarization separation layer that emits polarized light from light emitted from the light guide layer, and a plurality of fibers and a support thereof, which are incident on the light guide layer. And a light homogenization layer for diffusing and scattering light into the light guide layer.

In the light guide plate, the polarization separation layer may include a plurality of first fibers having birefringence and an isotropic first support for supporting the first fibers.

The refractive index of the first support may match at least one of two refractive indices of the first fiber.

The optical homogenization layer may include a plurality of second fibers having birefringence and an isotropic second support for supporting the second fibers.

The refractive index of the second support may be different from at least one of the two refractive indices of the second fiber.

Any one selected from the light guide layer, the polarization separation layer, and the light homogenization layer may be provided between the other two.

The light guide plate is provided on a phase difference plate for converting the polarization direction of the light in the light guide layer, and a surface other than the light incident surface and the light emitting surface of the light guide layer, and reflects the light emitted from the light guide layer into the light guide layer. A reflector may be further provided.

The polarization separation layer and the light homogenization layer may be stacked on the light emitting surface of the light guide layer. In this case, the polarization separation layer and the optical homogenization layer may be integrated to form a single layer. In the single layer, the first fiber and the second fiber may be arranged crosswise, and the first and second supports may form a single third support that supports the cross arranged first and second fibers. The first fiber and the second fiber may be different in material.

The material of the light guide layer may be the same as the material of at least one of the first and second supports.

The first fibers may be densely arranged away from the light incident surface.

The second fiber may have a different density of the arrangement depending on the arrangement position.

Some of the plurality of first and second fibers may comprise discrete portions.

Some of the plurality of first and second fibers may overlap.

The surface light source device according to an embodiment of the present invention includes a light source unit including a plurality of light sources spaced apart from each other, and a light guide plate emitting a polarization component of light incident from the light source unit, wherein the light guide plate is in the embodiment of the present invention. It may be a light guide plate.

In such a surface light source device, the array density of the second fibers may be high between the plurality of light sources.

The plurality of light sources may be divided into two opposing side surfaces of the light guide plate.

A flat panel display according to an embodiment of the present invention includes a light source device and a liquid crystal panel for displaying an image using light supplied from the light source device, and the light source device includes a surface light source according to an embodiment of the present invention described above. It may be a device.

According to one embodiment of the present invention, light is scattered and diffused at various angles in the in-plane direction by the optical homogenization layer in which the second fibers extending perpendicular to the incident surface are arranged. Therefore, even when a discontinuous light source is used, uniform luminance can be obtained.

Further, only the desired polarization component can be selectively taken out with high polarization separation efficiency by the polarization separation layer in which the first fibers extending parallel to the incident surface are arranged.

1 is a perspective view of a surface light source device according to a first embodiment of the present invention.
2A and 2B are diagrams for explaining the relationship between one fiber and the refractive index.
3 is a cross-sectional view showing a modification of the cross-sectional shape of the fiber.
4A is a right side view of the surface light source device of FIG. 1.
4B is an enlarged view of FIG. 4A illustrating a propagation state of an S polarized light component incident on a polarization splitting layer.
4C is an enlarged view of FIG. 4A illustrating a propagation state of a P polarization component incident on a polarization splitting layer.
5 is a bottom view of the surface light source device of FIG. 1.
6 is a side view of the surface light source device according to the second embodiment of the present invention.
7 is a side view of the surface light source device according to the third embodiment of the present invention.
8 is a side view of the surface light source device according to the fourth embodiment of the present invention.
9 is a side view of the surface light source device according to the fifth embodiment of the present invention.
10 is a side view of the surface light source device according to the sixth embodiment of the present invention.
11 is a side view of the surface light source device according to the seventh embodiment of the present invention.
12 is a cross-sectional view of the polarization splitting layer formed in the surface light source device according to the eighth embodiment of the present invention.
FIG. 13 is a diagram showing a two-dimensional luminance distribution of light emitted from an upper surface (light emitting surface) of a light guide plate of the surface light source device according to the ninth embodiment of the present invention.
FIG. 14 is a diagram illustrating a two-dimensional luminance distribution of light emitted from an upper surface (light emitting surface) of a light guide plate of a surface light source device manufactured by a comparative example. FIG.

Hereinafter, a light guide plate according to an embodiment of the present invention, a surface light source device including the same, and a flat panel display including the same will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of layers or regions illustrated in the drawings are exaggerated for clarity. In addition, the dimension ratio of drawing is exaggerated for convenience of description, and may differ from an actual ratio.

In the following description, the case of "lamination" may include not only the case of lamination directly, but also the case of lamination indirectly by interposing different configurations therebetween. In addition, the presence of a member such as a layer, an area, a plate, or the like on another member "on" or "upper" includes not only the case of "just above" the other member but also the case where there is another member in the middle. Similarly, the presence of a member such as a layer, an area, or a plate "below" or "below" of another member includes not only the case where it is "just below" of the other member, but also when there is another member in the middle thereof.

First, a surface light source device according to embodiments of the present invention will be described.

1 shows a schematic configuration of a surface light source device according to a first embodiment of the present invention. 2A and 2B are diagrams for explaining the relationship between one fiber and the refractive index, and FIG. 3 shows a modification of the cross-sectional shape of the fiber.

As shown in FIG. 1, the surface light source device 1 is an edge light type surface light source device, and among the light source unit 10 and the light irradiated from the light source 11 of the light source unit 10, the desired surface light source device 1 is used. The light guide plate 20 which emits a polarization component is provided. In the present embodiment, the surface light source device 1 emits light toward the top of the ground. Although not shown, when the surface light source device 1 is applied to a liquid crystal display, a liquid crystal unit may be disposed on the surface light emitting side.

The light source unit 10 generates light for supplying to the surface light source device 1, and includes a plurality of light sources 11 arranged on the side of the light guide plate 20 and arranged at given intervals. The arrangement interval of the plurality of light sources 11 may or may not be constant.

In FIG. 1, the light sources 11 are arranged in one dimension but may be arranged in two dimensions. For example, the plurality of light sources 11 may be composed of dot-shaped LEDs (light emitting diodes).

The light guide plate 20 may have a rectangular parallelepiped shape. The light guide plate 20 includes a light guide layer 30, a polarization separation layer 40 stacked on the light guide layer 30, an optical homogenization layer 50 stacked on the light guide layer 30, and a phase difference plate provided on the light guide layer 30. 60 and the reflecting plate 70 are included. The polarization separation layer 40 and the light homogenization layer 50 are provided to face each other with the light guide layer 30 therebetween. The light guide layer 30 introduces the light irradiated from the light source 11 into the side from the incident surface 30a which is a side surface. The introduced light propagates in the light guide layer 30 and selectively extracts only a predetermined polarization component from the polarization separation layer 40. The light guide layer 30 may be formed of a transparent material that may transmit incident light. In this case, the transparent material may be, for example, an optically isotropic material such as polymethyl methacrylate (PMMA) or polycarbonate (PC). The polarization splitting layer 40 is stacked on the light guide layer 30, and the desired polarization of the light in the light guide layer 30 is derived from the light emitting surface 30b, which is one main surface of the light guide layer 30, and is orthogonal to the polarization. Reflects polarized light. Although the position of the polarization separation layer 40 is not particularly limited, for example, it may be located on the outer surface of the light guide layer 30.

The polarization splitting layer 40 may include a first fiber 41 and a first support medium 42 supporting the first fiber 41. The first fiber 41 is formed in a shape extending in parallel to the incident surface 30a of the light guide layer 30. Here, "extending parallel to the incidence plane" refers to the direction parallel to the incidence plane 30a as well as the case where the extending direction (length direction) of the first fiber 41 coincides with the direction completely parallel to the incidence plane 30a. It also includes the case where the extension direction (length direction) of the 1st fiber 41 is inclined with respect to +/- 45 degrees with respect to the. The polarization separation layer 40 includes a plurality of first fibers 41. The plurality of first fibers 41 are arranged in a direction perpendicular to the incident surface 30a of the light guide layer 30. The light homogenization layer 50 is laminated on the light guide layer 30, and diffuses the light in the light guide layer 30 in the in-plane direction, that is, the direction orthogonal to the direction of propagation of the light to homogenize the direction of the light. The optical homogenization layer 50 includes a second fiber 51 and a second support medium 52 that supports the second fiber 51. The second fiber 51 is formed in a shape extending perpendicularly to the incident surface 30a of the light guide layer 30. Here, "extending perpendicularly to the incidence plane" refers to the direction perpendicular to the incidence plane 30a as well as the case where the extension direction (length direction) of the second fiber 51 coincides with the direction completely perpendicular to the incidence plane 30a. It also includes the case where the extension direction (length direction) of the 2nd fiber 51 is inclined with respect to +/- 45 degrees with respect to.

The optical homogenization layer 50 is provided with a plurality of second fibers 51. The plurality of second fibers 51 are arranged in a direction parallel to the incident surface 30a of the light guide layer 30. In other words, the second fibers 51 are arranged in a direction orthogonal to the arrangement direction of the first fibers 41 in the polarization separation layer 40. The fibers 41 and 51 included in the polarization separation layer 40 and the optical homogenization layer 50 have a large abnormal light refractive index ne that is a refractive index in the longitudinal direction and a small normal light refractive index no that is a refractive index in the cross-sectional direction. It has birefringence.

The relationship between one fiber 41 and 51 and refractive index is demonstrated with reference to FIG. 2A and FIG. 2B.

As shown in Figs. 2A and 2B, the fibers 41 and 51 have a refractive index (normal light refractive index) no in the cross-sectional direction smaller than the refractive index (abnormal light refractive index) ne in the longitudinal direction. Various materials having birefringence may be used as the fibers 41 and 51, and may be polymer fibers produced by extending the polymer in terms of excellent stability and durability of the cross-sectional shape and easy control of orientation.

The material of the polymer fiber is a polyolefin fiber such as polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), polyvinyl chloride (PVC), polyvinyl fiber such as polyvinyl alcohol (PVA), or acrylic fiber such as polyacrylonitrile (PAN), or nylon 6 (N6), nylon 6,6 (N66), nylon 4,6 ( N46), aliphatic polyamide fibers such as nylon 6,10 (N610), or aromatics such as poly (m-phenyleneisophthalamide) (PMPIA) and poly (p-phenylene telephthalamide) (PMPTA) Polyamide fibers (aramid fibers), polyester fibers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and poly-ε-caprolactone, or animal fibers such as silk, wool, and spider webs, or It may be a cellulose-based plant fiber, such as plastic, rayon-based fibers. The kind of the 1st fiber 41 and the 2nd fiber 51 is selected so that the relationship of the refractive index mentioned later may be satisfy | filled, the same kind may be used, and a different kind may be used. In some cases, various types of fibers may be used for the polarization separation layer 40 or the optical homogenization layer 50. The first and second fibers 41 and 51 may use polymer fibers having a large difference Δn between the abnormal light refractive index ne and the normal light refractive index no. As the refractive index difference Δn increases, polarization separation efficiency of the polarization separation layer 40 and light diffusion efficiency of the light homogenization layer 50 may be improved. The regulation rate difference Δn may be 0.03 or more, for example, 0.05 or more or 0.1 or more.

The ordinary light refractive index (no) and abnormal light refractive index (ne) of such a polymer fiber adjust the tensile speed or tensile rate when extending a polymer, the material of a polymer, the thickness (diameter), or the density of a fiber. Can be controlled.

Table 1 below shows typical light refractive index (no) and abnormal light refractive index (ne) of typical stretched polymer fibers. In addition, the refractive indices (no, ne) of Table 1 are used to immerse the fibers in liquids of various refractive indices and adjust the liquids in which the fiber wires are invisible by assimilating with the liquid using a polarization microscope. The refractive index of the fiber was determined by measuring with DR-A1 (wavelength 589 nm). No and ne can be measured by measuring about each transmission axis of polarization.

The thickness of the first and second fibers 41 and 51 is not particularly limited and may be controlled to suit the size of the display to be applied or to have a desired refractive index. For example, the thicknesses of the first and second fibers 41 and 51 may be about 1 μm to 200 μm.

The spacing between the first and second fibers 41 and 51 is not particularly limited and may be appropriately selected according to the size of the display so as to be smaller than the pixel pitch of the liquid crystal display device to which the first and second fibers 41 and 51 are applied. The spacing of the arrangement of the first and second fibers 41, 51 may be regular or irregular. In addition, the first and second fibers 41 and 51 may have a single layer structure or a multilayer structure.

The first fibers 41 may be arranged uniformly or differently in density. For example, the first fiber 41 may be disposed to be higher in density while away from the light source 11. That is, the density of the first fibers 41 in the polarization separation layer 40 may increase continuously or stepwise while moving away from the light source 11. The amount of light decreases as it moves away from the light source 11. Therefore, the first fiber 41 is densely arranged in a region away from the light source 11 having a small amount of light, and the first fiber 41 is sparsely disposed in the vicinity of the light source 11 having a large amount of light. Surface), it is possible to take out a homogeneous light from the whole.

The length of the first and second fibers 41 and 51 can be determined in accordance with the size of the polarization separation layer 40 or the light homogenization layer 50 on which the first and second fibers 41 and 51 are disposed. The length of the first and second fibers 41 and 51 is not limited to being continuous over the length direction of the polarization separating layer 40 or the light homogenizing layer 50. That is, a portion of the first and second fibers 41 and 51 may be divided so that discontinuous portions may exist. In addition, some of the first and second fibers 41 and 51 may overlap. Further, the first and second fibers 41 and 51 may have a circular cross section, as shown in FIG. 1, but are not limited to a circular shape and may have other cross-sectional shapes. The other cross-sectional shape may be, for example, a cross-sectional shape in which a regular or irregular polygon such as a triangle, a rectangle, a hexagon, or the like is combined, or a combination of curved and straight sides. Here, the term "polygon" includes not only a figure in which each side is a straight line, but also a figure in which each side includes a slight curve. In other words, the polygonal cross sections of the polymer fibers 41 and 51 may have a slight curve at each side or a vertex portion, and such cross-sectional shapes are also included in the "polygon" cross-sectional shape.

In the polarization separation layer 40, as described later, only the polarization component of specific light is selectively scattered by the first fiber 41 and taken out from the light emitting surface 30b. Scattered light in a direction perpendicular to the direction is reduced.

When the surface light source device including the light guide plate according to the embodiment of the present invention is used as the backlight of the liquid crystal display, when the cross-sectional shape of the first fiber 41 is polygonal, the scattering angle is varied and scattered light is perpendicular to the waveguide direction. More, and as a result, light having a more uniform angular distribution can be obtained.

The shape of the outer circumferential surface of the first and second fibers 41 and 51 is not particularly limited. The surface roughness Rz of the outer circumferential surface of the first fiber 41 may be about 0.1 μm to about 10 μm. In this case, the scattering angle of the light by the first fiber 41 is varied, so that light having a more uniform angle distribution can be obtained. Here, "surface roughness Rz" means the maximum height of the smooth surface prescribed by JIS B 0601-2001.

The first and second support media 42, 52 serve to support the first and second fibers 41, 51, respectively, and may be formed of a material having optical isotropy. Therefore, the material of the first and second support media 42, 52 is not particularly limited as long as it exhibits good adhesion to the first and second fibers 41, 51 and has optical transparency. For example, the materials of the first and second support media 42, 52 may be curable resins polymerized / crosslinked by heat or radiation. Specifically, the curable resin is a UV curable resin made of a compound having acryloyl group, methacryloyl group, vinyl group, aryl group, styryl group, thiol group, epoxy group, vinyl ether group, oxetanyl group; Thermosetting resins composed of silicone resins, aryl esters, acrylic resins, epoxy resins, polyimides, urethane resins, and the like; And mixtures thereof. Furthermore, acrylic resins, such as poly (methyl methacrylate) (PMMA), polyolefin resins, such as polyethylene (PE) and a polypropylene (PP) cycloolefin polymer (COP), polyester resins, such as polyethylene terephthalate (PET), Polyethers such as polyphenylene oxide (PPO), vinyl resins such as polyvinyl alcohol (PVA), polystyrene, polycarbonate, polyurethane, polyamide, polyimide, epoxy resin, and two kinds of monomers constituting these The copolymer used above, these polymer blends, etc. can be used as a material of the 1st and 2nd support media 42 and 52. By mixing a plurality of resins, the refractive indices (nm) of the first and second support media 42, 52 can be controlled to a desired value.

The polarization splitting layer 40 may be configured such that the refractive index nm1 of the first support medium 42 and the normal ray refractive index no1 or the abnormal ray refractive index ne1 of the first fiber 41 coincide with each other.

The refractive index nm1 of the first support medium 42 and the image ray refractive index no1 of the first fiber 41 will be described below.

In the present specification, "a refractive index nA coincides with a refractive index nB" means a case where nA and nB coincide with precision of 2 or more decimal places, and may mean a case of matching with 3 or more digits of precision. Therefore, it may be expressed as nA = nB ± 0.003.

The optical homogenization layer 50 may be configured such that the refractive index nm2 of the second support medium 52 differs from at least one of the normal light refractive index no2 and the abnormal light refractive index ne2 of the second fiber.

Hereinafter, the refractive index nm2 of the second support medium 52 will be described as being different from both the normal light refractive index no2 and the abnormal light refractive index ne2 of the second fiber 51.

The retardation plate 60 is mounted on the side opposite to the incident surface 30a of the light guide layer 30 and converts the polarization direction of the light propagating through the light guide layer 30. The retardation plate 60 may be, for example, a λ / 4 plate that staggers the phase by λ / 4. The provision of the retardation plate 60 may be optional. Therefore, the retardation plate 60 may be omitted.

The reflector 70 is formed on a side surface other than the incident surface 30a of the light guide layer 30 or a main surface opposite to the light emitting surface 30b to prevent light in the light guide layer 30 from leaking outside the light emitting surface 30b. Are stacked. The reflector 70 is laminated on the retardation plate 60 and the light homogenization layer 50. Although not shown, the reflecting plate 70 may be provided on two side surfaces other than the incident surface 30a and the opposite surface of the incident surface 30a of the light guide layer 30. In addition, although not shown, the reflective plate 70 may be provided between the plurality of light sources 11 or above and below.

Next, the principle which takes out the light of a light source as surface light emission in the surface light source device 1 is demonstrated.

4A is a right side view of the surface light source device 1 of FIG. 1, FIG. 4B is an enlarged view of FIG. 4A showing the propagation state of the S polarization component incident on the polarization separation layer 40, and FIG. 4C is the polarization separation. It is an enlarged view of FIG. 4A which shows the propagation state of the P polarization component incident on the layer 40.

As shown in FIG. 4A, light is incident from the light source 11 to the incident surface 30a of the light guide layer 30. The incident light propagates the light guide layer 30 while repeating total internal reflection at the interface between the polarization separation layer 40, the light homogenization layer 50, and the retardation plate 60, as indicated by the dashed and dashed lines. The light is also reflected by the reflecting plate 70 attached to the outer side of the retardation plate 60 and the lower portion of the light homogenizing layer 50 and the side surface of the light guiding layer 30. It continues to propagate in layer 30.

Light generated by the light source 11 is natural light, and light of various polarization components is mixed. Hereinafter, in FIG. 4A-4C, the dashed lines and the black circles are polarization components vibrating in the same plane as the ground, and are referred to as P polarization components. In addition, what is represented by the dashed-dotted line and an arrow is a polarization component which vibrates in the plane perpendicular | vertical to the ground, and is called S polarization component. The S-polarized component is selectively taken out from the light emitting surface 30b by the polarization separating layer 40.

The polarization splitting layer 40 has the first fiber 41 as described above. As shown in FIG. 2A, the first fiber 41 has the abnormal light refractive index ne1 in the longitudinal direction and the normal light refractive index no1 in the cross-sectional direction. The S-polarized component vibrates in a plane parallel to the cross section in which the first fiber 41 is cut in the longitudinal direction. Therefore, the S-polarized component may be affected by the abnormal light refractive index ne1 in the longitudinal direction of the first fiber 41, but is not affected by the normal light refractive index no1 in the cross-sectional direction.

On the contrary, since the P-polarized component vibrates in a plane parallel to the cross section of the first fiber 41, the P-polarized component may be affected by the normal light refractive index no1 in the cross-sectional direction of the first fiber 41, but is an abnormal light beam in the longitudinal direction. It is not affected by the refractive index ne1.

Here, the first support medium 42 supporting the first fibers 41 is formed such that the refractive index nm1 coincides with the normal ray refractive index no1 of the first fiber 41. Therefore, when light is incident from the first support medium 42 to the first fiber 41 or from the first fiber 41 to the first support medium 42, the material having the same refractive index propagates as the P polarization component. . Therefore, the P-polarized component of the light goes straight without affecting the normal ray refractive index no1. In other words, the first fiber 41 is not present in the first support medium 42 with respect to the P polarization component of light. Therefore, the P-polarized component represented by the dashed-dotted line in FIG. 4 is not refracted by the first fiber 41 and as a result is reflected according to the total internal reflection condition of the first support medium 42.

On the other hand, the refractive index nm1 of the first support medium 42 is formed differently from the abnormal ray refractive index ne1 of the first fiber 41. Thus, when light is incident from the first support medium 42 to the first fiber 41 or from the first fiber 41 to the first support medium 42, it propagates through a material of different refractive index as the S polarization component. Done. Therefore, the S-polarized component of the light is refracted or reflected under the influence of the extraneous ray refractive index ne1. Accordingly, the S-polarized component represented by the dashed-dotted line in FIG. 4 is refracted or reflected by the first fiber 41, a part of which enters the interface at an acute angle away from the total internal reflection condition of the first support medium 42, and thus the first support medium. It is taken out at 42.

By laminating the polarization separation layer 40 on the light guide layer 30 in this manner, only the S polarization component can be selectively scattered and taken out from the light emitting surface 30b. As a result, only the polarization component required for the liquid crystal unit can be selectively taken out.

In the above, the case where the refractive index nm1 of the first support medium 42 coincides with the normal light refractive index no1 of the first fiber 41 is different from the abnormal light refractive index ne1.

However, the refractive index nm1 of the first support medium 42 may be configured to match the extraordinary ray refractive index ne1 of the first fiber 41 and to match the ordinary ray refractive index no1. In this case, only the P polarization component can be selectively scattered and taken out from the light emitting surface 30b side. However, the use of the S polarization component that does not oscillate in the same plane as the waveguide direction of light is superior to the P polarization component that oscillates in the plane such as the waveguide direction of light, so that the scattering efficiency is excellent. It may be preferable to configure the first fiber 41 to match the normal ray refractive index no1.

Next, the principle of diffusing the light in the light guide layer 30 in the in-plane direction by the light homogenization layer 50 will be described. 5 is a bottom view of the surface light source device of FIG. 1.

As shown in Fig. 5, the light source 11 in which the LED is used is point emission. As a result, the amount of light between the adjacent light sources 11 decreases, and a dark portion may be generated in the inter-light source region 12 near the light source 11. Since the light propagated in the light guide layer 30 is scattered in the in-plane direction by the light homogenization layer 50, the direction distribution of the light in the light guide layer 30 may be homogenized. Accordingly, the dark part may disappear.

The optical homogenization layer 50 includes the second fiber 51 as described above, and the second fiber 51 has the abnormal light refractive index ne2 in the longitudinal direction and the normal light refractive index no2 in the cross-sectional direction. . The 2nd fiber 51 is arrange | positioned so that the longitudinal direction may correspond with the waveguide direction of light. Therefore, the light incident on the second fiber is affected by the normal ray refractive index no1 and the effective abnormal ray refractive index ne2_eff.

As shown in FIG. 2B, when the light guided in the longitudinal direction of the second fiber 51 in the optical homogenization layer 50 is incident on the second fiber 51 at the incident angle θ, the second fiber 51 The effective abnormal light refractive index ne2_eff of) is expressed by the following formula (A).

In formula (A), no2 is the ordinary ray refractive index of the second fiber 51, ne2 is the extraordinary ray refractive index of the second fiber 51, and θ is the angle of incidence of light with respect to the second fiber (length direction) 51. .

Since the P-polarized component vibrates in a plane parallel to the cross section of the second fiber 51 cut in the longitudinal direction, the effective polarized light refractive index ne2_eff in the longitudinal direction of the second fiber 51 may be affected. It is not affected by the image ray refractive index no2 in the cross-sectional direction.

On the contrary, since the S-polarized component vibrates in a plane parallel to the cross section of the second fiber 51, the S-polarized component may be affected by the normal ray refractive index no2 in the cross-sectional direction of the second fiber 51, but is effective in the longitudinal direction. It is not affected by the abnormal ray refractive index ne2_eff.

That is, when light is incident from the second support medium 52 to the second fiber 51, or from the second fiber 51 to the second support medium 52, the P-polarized component has an effective abnormal light refractive index ne2_eff. Is refracted or reflected under the influence of), and the S polarization component is refracted or reflected under the influence of the ordinary ray refractive index no2. At this time, in the optical homogenization layer 50, the 2nd fiber 51 is arrange | positioned so that the longitudinal direction of the 2nd fiber 51 may be parallel to a waveguide direction. Therefore, the interface between the second fiber 51 and the second support medium 52 on which light is incident is not orthogonal to the waveguide direction, and when the P-polarized component or the S-polarized component is refracted or reflected at the interface, The angular distribution is changed. That is, the light may be angled to the left and right of the waveguide direction. As a result, the light propagated in the light guide layer 30 can be scattered and diffused at various angles to homogenize the direction distribution of the light.

In addition, since the light in the optical homogenization layer 50 is refracted and enlarged only in the left and right directions, and the angle in the vertical direction is not changed, both polarizations of P and S do not satisfy the total reflection condition by the optical homogenization layer 50. It is not. That is, in the optical homogenization layer 50, only the function of enlarging the light to the left and right to remove the spots of the LED, and in the polarization separation layer 40, the angle of refraction of the vertical direction only S polarized light is changed, so that only the desired piece of polarized light is taken out of the light guide plate. It is compatible with the light spot improvement of the LED.

In order to exert the optical homogenization function, the refractive index nm2 of the second support medium 52 may be different from the normal light refractive index no2 and the abnormal light refractive index ne2 of the second fiber 51.

However, the optical homogenization layer 50 may act more strongly as a homogenization layer of S polarized light.

In this regard, the difference between the ordinary light refractive index no 2 and the refractive index nm 2 of the second support medium may be 0.03 or more, for example, 0.05 or more or 0.1 or more.

Further, in order to scatter and diffuse both the S-polarized component and the P-polarized component in a good balance, the normal light refractive index no2 and the extraordinary light refractive index ne2 of the second fiber 51 and the refractive index of the second support medium 52 (nm2). ) May satisfy the following equation (1).

In particular, the refractive index nm2 of the second support medium 52 and the effective abnormal light refractive index ne2_eff of the second fiber 51 may satisfy the following equation (2).

The refractive index (nm2) of the second support medium 52 may satisfy the following formula (3), in which case the refractive index (nm2) of the second support medium 52 is the effective abnormal light beam of the second fiber 51. Since it is smaller than the refractive index ne2_eff, P polarization component can be scattered and diffused. Therefore, it can act as an optical homogenization layer which diffuses and scatters both polarization of P polarization and S polarization effectively.

In the above formula, no2 is the normal light refractive index of the second fiber 51, ne2 is the extraordinary light refractive index of the second fiber 51, and nl is the refractive index of the light guide layer 30.

Here, the formula (3) is derived from the formula (2), the formula (A) and the following formulas (B) to (F).

In the above formula, no2 is an ordinary light refractive index of the second fiber 51, ne2 is an abnormal light refractive index of the second fiber 51, ni is a refractive index of the external medium of the light guide plate 20, and nl is a light guide layer 30. Θ i is the angle of incidence of the light incident on the light guide layer 30, θ l is the angle of refraction of the light incident on the light guide layer 30, θ in is the angle of incidence of the light incident on the light homogenization layer 50, and θ out is It is a refractive angle of light incident on the light homogenization layer 50. Usually, the light guide plate 20 is disposed in air, and the refractive index ni of the external medium of the light guide plate 20 is equal to the refractive index of air (= 1) and is represented by the above formula (B).

In Equation (A), the equation (F) is derived by setting nm2 = ne2_eff and modifying the equation using the above equations (B) to (E). And the equation (3) is derived from the equation (2) and the equation (F). When nm2 = ne2_eff, the incident light component (θi ≒ π / 2) at which the angle becomes the maximum during P polarization does not go straight without being refracted or reflected by the second fiber 51 of the optical homogenization layer 50. Therefore, the optical homogenization layer 50 cannot exert an optical homogenization effect on such light. In this case, the effective refractive index for light having a small angle θ is close to no2.

When the above formulas (B) to (F) are satisfied, the light homogenizing effect can be exerted on the incident light component incident on the second fiber 51 at all angles θ.

When the refractive index difference between nm2 and ne2_eff represented by the above formula (F) differs by 0.03 or more, the effect of the P polarization component as a homogenizing layer can be further improved.

As shown in FIG. 5, in the optical homogenization layer 50, the density of the second fibers 51 located on the centerline between adjacent light sources is determined by the density of the second fibers 51 located on the axis of the light irradiation direction of the light sources. May be greater than the density. Since the amount of light is small between the light source and the light source, a dark portion easily occurs in the inter-light source region 12 near the light source. Therefore, by densely arranging the second fibers 51 in these areas, the light homogenization effect can be further improved.

In addition, in the polarization separation layer 40 described above, the first fibers 41 are disposed such that the longitudinal direction of the first fibers 41 is perpendicular to the waveguide direction. Therefore, the cross-sectional shape of the 1st fiber 41 in the radial direction is the same or almost the same, even if cut | disconnected anywhere in the longitudinal direction of the 1st fiber 41. Since the first fiber 41 has no change in shape in the longitudinal direction, when the P-polarized component or the S-polarized component is refracted and reflected by the first fiber 41, the light is viewed in both directions in the waveguide direction. It is not substantially scattered. It is scattered in the plane along the waveguide direction. That is, the angle distribution in the in-plane direction is not substantially changed.

In the light homogenization layer 50, light scattering in the in-plane direction is possible by the second fibers 51 extending perpendicular to the incident surface 30a. As a result, scattering in the in-plane direction of light that cannot be sufficiently obtained only by using the PSSE of the first fiber 41 extending in parallel with the incident surface can be obtained.

When only the S-polarized component is taken out, light of a phase close to the P-polarized component remains in the light guide layer 30. In order to effectively utilize the remaining light, the retardation plate 60 is disposed.

In FIG. 1, the retardation plate 60 is a λ / 4 plate, and is formed to have a thickness of 90 degrees to offset the phase of light incident at right angles to the retardation plate 60. Light that totally internally reflects inside the light guide layer 30 is not incident to the retardation plate 40 at a right angle as shown in FIG. 4. The P polarization component is out of phase so as to be close to the S polarization component.

On the contrary, although the S-polarized component may be converted to the P-polarized component, the ratio of the S-polarized component to the S-polarized component is high because the S-polarized component is selectively emitted to the outside. Since the light remaining in the light guide layer 30 is converted into the S polarization component as described above, the extraction efficiency of the S polarization component can be increased, and as a result, the light utilization efficiency can be increased.

As the retardation plate 40, a suitable one can be used depending on the wavelength band. For example, a birefringent sheet formed by stretching a film formed of polycarbonate (PC), polysulfone (PS), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyamide, polyester, or the like; The support sheet of a liquid crystal polymer (polymer) alignment layer or these multilayer laminated bodies can be used as the retardation plate 40. In addition, a sheet formed by arranging the first and second fibers 41 and 51 used in the polarization separation layer 40 or the optical homogenization layer 50 in the support medium may be used as the retardation plate 40.

Second Embodiment

6 shows a schematic configuration of a surface light source device according to a second embodiment of the present invention.

In FIG. 4, the light homogenization layer 50 is provided on the lower surface of the light guide layer 30. However, the position where the light guide layer 30 is provided is not limited. The optical homogenization layer 50 only needs to be laminated on the light guide layer 30. Therefore, the light homogenization layer 50 may be provided between the light guide layer 30 and the polarization separating layer 40, as in the surface light source device 1 shown in FIG.

Third Embodiment

7 shows a schematic configuration of a surface light source device according to a third embodiment of the present invention.

As in the surface light source device 1 shown in FIG. 7, the light homogenization layer 50 may be provided on the upper surface of the polarization separation layer 40.

Fourth Example

8 shows a schematic configuration of a surface light source device according to a fourth embodiment of the present invention.

In FIG. 4, the retardation plate 60 is mounted on a side opposite to the incident surface 30a of the light guide layer 30. However, the retardation plate 60 may be mounted on at least one side of the light guide layer 30 opposite to the laminated surface of the polarization separation layer 40 and the side surface of the light guide layer 30 other than the incident surface 30a.

For example, like the surface light source device 1 shown in FIG. 8, the retardation plate 60 has a main surface of the light guide layer 30 opposite to the surface on which the polarization separation layer 40 is laminated, that is, the light guide layer. It may be installed on the lower surface of the (30). However, when the phase difference plate 60 is provided on the main surface or side surface of the light guide layer 30 perpendicular to the waveguide direction as shown in FIG. 8, the phase difference plate 60 is a λ / 2 plate, and the phase difference plate ( 60 may be formed to have a thickness staggered 180 degrees of light incident at right angles.

As a result, even when the light is refracted and reflected toward the light guide layer 30 in the polarization separation layer 40 and is incident on the retardation plate 60 at an acute angle, the phase of the light is changed by about 180 degrees. S polarization component is kept as it is. Therefore, the light of the S polarized light component is reflected by the reflector 70, and returns to the light guide layer 30 again and exits from the polarization separation layer 40. In this way, the light of the S-polarized component is emitted and the light of the P-polarized component is prevented from being emitted.

In addition, as described above, since light guiding in the light guide layer 30 is not normally incident at right angles to the retardation plate 60, the λ / 2 retardation plate 60 is appropriately converted from the P polarization component to the S polarization component. do.

Fifth Embodiment

9 is a plan view showing a schematic configuration of a surface light source device according to a fifth embodiment of the present invention. The same reference numerals are used for the members mentioned in the previous embodiment.

The surface light source device shown in FIG. 9 includes a polarization split light homogenizing layer 80.

In the above-described first to fourth embodiments, the polarization separation layer 40 and the light homogenization layer 50 are separately provided.

However, as shown in FIG. 9, the surface light source device may be provided with a polarization splitting light homogenizing layer 80 in which the polarization splitting layer 40 and the light homogenizing layer 50 are integrated.

Referring to FIG. 9, a polarization splitting light homogenization layer 80 includes a first fiber 81 and a second fiber 82, and a third support medium for supporting the first and second fibers 81, 82. (83). The first fibers 81 extend in parallel to the incident surface 30a of the light guide layer 30, and a plurality of first fibers 81 are arranged in a direction perpendicular to the incident surface 30a. The second fibers 82 extend perpendicular to the incident surface 30a of the light guide layer 30 and are arranged in plural in a direction parallel to the incident surface 30a. That is, the first fiber 81 and the second fiber 82 are extended and arranged in the direction orthogonal to each other, and in the state where the first fiber 81 and the second fiber 82 are woven together, the third support medium ( 83).

In the polarization split light homogenization layer 80, the normal light refractive index no1 and the abnormal light refractive index ne1 of the first fiber 81, the normal light refractive index no2 and the abnormal light refractive index ne2 of the second fiber 82 And the refractive index n _matrix3 of the third support medium 83 satisfy the following equations (4) and (5).

As a result, the first fiber 81 (warp) selectively scatters only the S-polarized component to lead to the light emitting surface which is the upper surface of the polarization splitting light homogenizing layer 80, and the second fiber 82 (weft) The light propagating in the light guide layer 30 diffuses in the in-plane direction and serves to homogenize the direction distribution of the light. The refractive index n _matrix3 of the third support medium 83 may match the ordinary light refractive index no1 of the first fiber 81, and may be different from the abnormal light refractive index ne1. Therefore, the P-polarized component of the light goes straight without being refracted by the first fiber 81, and only the S-polarized component of the light is refracted and reflected under the influence of the extraordinary ray refractive index ne1 of the first fiber 81, and part of the light is emitted. Emitted through the cotton.

On the other hand, the refractive index n _matrix3 of the third support medium 83 may be different from the normal ray refractive index no2 and the abnormal ray refractive index ne2 of the second fiber 82. Therefore, the S-polarized component of the light goes straight without being refracted by the second fiber 82, and only the P-polarized component of the light is refracted and reflected under the influence of the extraordinary refractive index ne1 of the second fiber 82 and diffused in the in-plane direction. do.

As the first and second fibers 81 and 82, the first and second fibers 41 and 51 described in the foregoing embodiments may be used, and as the third support medium 83, the first support medium 42 or The second support medium 52 can be used. However, in the fifth embodiment, the first fibers 81 and the second fibers 82 may be formed of different materials to satisfy the above formulas (4) and (5) of the refractive index.

Sixth Example

10 shows a schematic configuration of a surface light source device according to a sixth embodiment of the present invention.

In the first to fifth embodiments (Figs. 1 to 9) described above, the light guide layer 30 is formed of a material different from the first and second support media 42 and 52.

However, the light guide layer 30 may be formed of the same material as at least one of the first and second support media 42, 52.

In the surface light source device shown in FIG. 10, the light guide layer 34 corresponds to a case where the light guide layer 30 of the surface light source device according to the first embodiment is formed of the same material as that of the first support medium 42. In other words, the light guide layer 34 of FIG. 10 may be regarded as an integral part of the light guide layer 30 and the polarization separation layer 40 of the first embodiment.

Although not shown in the drawings, the light guide layer 30 of the surface light source device according to the first embodiment is formed of the same material as the second support medium 52 so that the light guide layer 30 and the light homogenizing layer 50 are integrally formed. It can also be formed as. Although not shown in the drawing, in the surface light source device according to the first embodiment, the light guide layer 30, the first support medium 42, and the second support medium 52 are all formed of the same material to form the light guide layer 30. ), The polarization separation layer 40 and the light homogenization layer 50 may be formed as an integral layer.

In the surface light source device of FIG. 9 provided with the polarization splitting light homogenizing layer 80 in which the polarization splitting layer 40 and the light homogenizing layer 50 are integrated, the light guide layer 30 may be replaced by the third support medium 83. The polarization splitting light homogenizing layer 80 and the light guiding layer 30 may be formed as a single layer by forming the same material.

As such, by integrating the light guide layer 30 with the polarization separation layer 40 and / or the light homogenization layer 50, manufacturing is easy, cost can be reduced, and the light guide plate and the surface light source device can be reduced.

In the light guide layer 34 of FIG. 10, the first fibers 41 are arranged in the upper region, and the first fibers 41 may be disposed in the entirety of the light guide layer 34, or in other regions other than the upper region. May be

Seventh Example

11 shows a schematic configuration of a surface light source device according to a seventh embodiment of the present invention.

In the surface light source device 1 according to the first to sixth embodiments described above, the light source unit 10 is disposed on one side of the short side of the light guide layer 30 constituting the light guide plate 20.

However, the surface light source device 1 may include a plurality of light source units 10. For example, as illustrated in FIG. 11, the light source unit 10 may be disposed on both side surfaces of the light guide layer 30 on the short axis side.

The surface light source device shown in FIG. 11 corresponds to the case where the light source unit 10 is further provided in place of the reflecting plate 70 on the side in the surface light source device shown in FIG.

Although not shown in the drawings, the surface light source device except for the surface light source device according to the third embodiment of the above-described embodiments, for example, the surface light source device according to the first, second and fourth embodiments, may also be used. The light source part 10 can be arrange | positioned at the both sides of the short axis side of the light guide layer 30. FIG. That is, the light source unit 10 may be provided to face each other with respect to the light guide layer 30.

In some cases, the light source unit 10 may be further disposed on the side surface of the light guide layer 30 other than the light emitting surface on the long axis side.

Experimental Example

An experimental example performed to verify the effect of the surface light source device according to the embodiments of the present invention and a comparative example for comparing the same. The technical scope of the present invention is not limited to the following experimental examples.

Experimental Example 1

(1) Preparation of the light guide layer

As the light guide layer, PMMA (size: 6 cm x 9 cm) is prepared.

(2) Formation of polarized light separation layer

PET fiber (material: polyethylene terephthalate, no = 1.5449, ne = 1.7200, surface roughness (Rz) = 2 μm, cross-sectional shape: circle (diameter: 20 μm)) of the outer circumferential surface is the same as the first fiber on the prepared light guide layer. In the thickness direction of 15 layers. UV curable resin was infiltrated between the PET fibers as a first support medium designed to have a refractive index of 1.545 after curing. The UV curable resin EA-F5503 manufactured by Osaka Gas Chemical Co., Ltd .; 40 parts by weight, MK ester A-400 manufactured by Shin-Nakamura Chemical Industries; 58 parts by weight and photopolymerization initiator Irgacure 184, manufactured by Ciba Specialty Chemicals; 2 parts by weight of the mixture. Subsequently, vacuum degassing removes air between the PET fiber and the UV curable resin, and then covers the top with a glass plate subjected to a release treatment, and cures the UV curable resin using a UV lamp. Thereafter, the polarizing separation layer is formed on the light guide layer by peeling the glass plate.

The cross section of the polarization separation layer was observed using a laser microscope device (VK-9600, manufactured by Keyence). As shown in FIG. 11, the polarization separation layer was formed by supporting first UV fibers aligned in the same direction on a UV curable resin. It is confirmed to have a structure.

(3) Formation of Light Homogenization Layer

N610 fibers (material: nylon 6,10, no = 1.5217, ne = 1.5711, cross-sectional shape: circle (diameter: 50 mu m)) are arranged on the lower surface of the prepared light guide layer in the direction of arrangement of the first fibers in the polarization separation layer. It is arranged in the thickness of three layers in the direction orthogonal to. Subsequently, the UV curable resin is penetrated between the N610 fibers as a second support medium designed so that the refractive index after curing is 1.571. At this time, the UV curable resin MK ester A-BPE-4 manufactured by Shin-Nakamura Chemical Industries; 74 parts by weight, MK ester A-LEN-10 manufactured by Shin-Nakamura Chemical Industries; 24 parts by weight and photopolymerization initiator Irgacure 184, manufactured by Ciba Specialty Chemicals; It may be a mixture of 2 parts by weight. The light homogenization layer is formed on the light guide layer by curing the UV curable resin in the same manner as the polarization separation layer.

(4) Arrangement of the light source unit, retardation plate and reflector plate

Subsequently, a light source unit in which nine LEDs, which are light sources, are arranged on a side surface of the light guide layer in a one-dimensional arrangement (arranged arrangement) is provided on a short side of the light guide layer. At this time, the side surface of the light guide layer on which the light source is provided is a plane parallel to the longitudinal direction of the first fiber in the polarization separation layer and perpendicular to the cross-sectional direction of the second fiber in the light homogenization layer, and the arrangement direction of the LED is polarization separation. It is set as the direction parallel to the longitudinal direction of the 1st fiber in a layer. Then, the λ / 4 retardation plate is disposed on the side surface of the light guide layer opposite to the surface on which the light source unit is provided. Moreover, the reflecting plate is attached to all surfaces other than the upper surface (light emitting surface) and the surface in which the light source part was provided in the polarization separation layer. This produced the surface light source device. The surface light source device according to the present experimental example corresponds to the surface light source device according to the first embodiment shown in FIG. 1.

Experimental Example 2

An optical homogenization layer is formed on the upper surface of the light guide layer. Subsequently, a polarization separation layer was formed on the upper surface of the optical homogenization layer, and PET fibers (material: polyethylene terephthalate, no = 1.5449, ne = 1.7200, surface roughness (Rz) of the outer circumferential surface as second fibers constituting the optical homogenization layer). = 2 mu m, cross-sectional shape: circle (diameter 20 mu m)), and the same method as that of Experimental Example 1, except that UV curable resin designed to have a refractive index of 1.605 after curing was used as the second support medium. The surface light source device is manufactured. Wherein the UV curable resin is EA-F5503 manufactured by Osaka Gas Chemical Co., Ltd .; 68 parts by weight, benzyl acrylate; 30 parts by weight, and photopolymerization initiator Irgacure 184, manufactured by Ciba Specialty Chemicals; It may be a mixture of 2 parts by weight.

The surface light source device produced in Experimental Example 2 corresponds to the surface light source device shown in FIG. 6.

Experimental Example 3

The polarization separation layer is formed on the upper surface of the light guide layer. Subsequently, except that the light homogenization layer was formed on the upper surface of the formed polarization separation layer, the remainder is manufactured using the same method as the method of Experimental Example 2, and manufacturing a surface light source device.

The surface light source device produced in Experimental Example 3 corresponds to the surface light source device shown in FIG. 7.

Experimental Example 4

PET fibers (material: polyethylene terephthalate, no = 1.5449, ne = 1.7200, surface roughness (Rz) = 2 μm, cross-sectional shape: equilateral triangle (length of one side) of 10 μm) were used as the first fibers constituting the polarization separation layer. A surface light source device is manufactured by the same method as the method of Experimental Example 2, except that it is used.

Comparative Example 1

A surface light source device was manufactured in the same manner as in Experiment 1, except that the light homogenization layer was not formed on the lower surface of the light guide layer.

[evaluation]

In the surface light source device obtained in the above Experimental Example and Comparative Example 1, the luminance, luminance unevenness and polarization degree of the light emitted from the light emitting surface are measured. In this case, the measurement of the luminance and the luminance unevenness, and the measurement of the polarization degree are performed by using a two-dimensional color luminance meter Konica Minolta CA-2000 or Conoscope 80 manufactured by AUTRONIC-MELCHERS GmbH in combination with a polarizing plate to Find the ratio. In addition, the luminance measurement is performed by driving nine LEDs arranged in series at a constant current of 30mA. At this time, as the luminance of the light emitted, the front luminance at the center of the light emitting surface of the light guide plate is measured. Table 2 shows the results of these measurements.

13 and 14 show two-dimensional luminance distributions of light emitted from the upper surface (light emitting surface) of the light guide plate of the surface light source devices manufactured in Experimental Example 2 and Comparative Example 1, measured by CA-2000. In addition, the two-dimensional luminance distribution similar to that of FIG. 13 can also be obtained for the surface light source devices manufactured in Experimental Examples 1, 3, and 4. FIG.

In the case of the surface light source devices of Experiments 1 to 4 provided with the optical homogenization layer, as shown in Fig. 13, no streaks are observed on the light emitted from the upper surface of the laminate. From these results, in the case of the surface light source device according to the embodiments of the present invention, it can be seen that luminance unevenness is removed even when an LED which is a discontinuous light source is used. In addition, it is confirmed that the surface light source device manufactured in the above experimental examples can achieve high polarization separation ability.

On the other hand, in the case of the surface light source device produced in Comparative Example 1, the polarization separation ratio is similar to that of the experimental example. However, as shown in Fig. 14, streaks and stains are clearly observed in the light emitted from the upper surface of the laminate.

In addition, in the case of the surface light source device of Experimental Example 4 in which the cross-sectional shape of the first fiber constituting the polarization separation layer is an equilateral triangle, the surface light source device of Experimental Example 2 in which the cross-sectional shape of the first fiber is circular is in a direction perpendicular to the light guide layer. The intensity (luminance) of the emitted light (light emitted from the upper surface of the laminate) is about twice as large.

From the above, it can be seen that the surface light source device according to the embodiments of the present invention can achieve high polarization separation ability, and also prevent streaks of light even when using a discontinuous light source such as an LED.

Next, a flat panel display according to an embodiment of the present invention will be described.

The flat panel display includes a liquid crystal panel on which an image is displayed, and includes a light source device for supplying light used to display the image to the liquid crystal panel. The light source device may be a surface light source device according to an embodiment of the present invention described above. The liquid crystal panel may be positioned on a surface where the light of the surface light source device is emitted. The liquid crystal panel may be a conventional liquid crystal panel.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

1: Surface light source device 10: Light source part
11: light source 12: area between light sources
20: Light guide plate 30, 34: Light guide layer
30a: Incident surface 30b: Light emitting surface
40: polarization separation layer 41, 81: first fiber
42, 52, 83: first to third support media
50: optical homogenization layer 51, 82: second fiber
60: phase difference plate 70: reflection plate
80: polarization separation light homogenization layer

Claims (36)

A light guide layer having a light incident surface;
A polarization splitting layer that obscures and emits polarized light from the light emitted from the light guide layer, and reflects light of polarized light orthogonal to the emitted polarized light to the light guide layer; And
And a light homogenization layer including a plurality of fibers and a support thereof to diffuse and scatter light incident on the light guide layer into the light guide layer. The method of claim 1,
The polarization separation layer,
A plurality of first fibers having birefringence; And
The light guide plate comprising a; isotropic first support for supporting the first fiber. The method of claim 2,
The refractive index of the first support is a light guide plate that matches at least one of the two refractive indices of the first fiber. The method according to claim 1 or 2,
The optical homogenization layer,
A plurality of second fibers having birefringence; And
The light guide plate comprising a; isotropic second support for supporting the second fiber. The method of claim 4, wherein
A light guide plate of which the refractive index of the second support is different from at least one of the two refractive indices of the second fiber. The method of claim 4, wherein
The light guide plate of the second optical fiber (no2) and the abnormal light refractive index (ne2) and the refractive index (nm2) of the second support satisfies the following formula (1).

The method of claim 2,
The surface roughness (Rz) of the outer peripheral surface of the said 1st fiber is 0.1 micrometer-10 micrometers. The method of claim 2,
A light guide plate in which the radial cross-sectional shape of said first fiber is polygonal. The method of claim 4, wherein
The light guide plate of any one selected from the light guide layer, the polarization separation layer and the light homogenization layer is provided between the remaining two. The method of claim 9,
A phase difference plate for converting a polarization direction of light in the light guide layer; And
And a reflector provided on a surface of the light guide layer except for a light incident surface and a light emitting surface, and reflecting light emitted from the light guide layer into the light guide layer. The method of claim 9,
The polarizing separation layer and the light homogenization layer is a light guide plate laminated on the light emitting surface of the light guide layer. The method of claim 11,
The light guide plate of which the polarization separation layer and the light homogenization layer are integrated to form a single layer. The method of claim 12,
Wherein the first fiber and the second fiber are cross-aligned in the single layer, and the first and second supports form a single third support for supporting the cross-aligned first and second fibers. The method of claim 12,
A phase difference plate for converting a polarization direction of light in the light guide layer; And
And a reflector provided on a surface of the light guide layer except for a light incident surface and a light emitting surface, and reflecting light emitted from the light guide layer into the light guide layer. The method of claim 9,
The light guide plate is the same as the material of at least one of the said 1st and 2nd support body. The method of claim 13,
Ordinary ray refractive index of the first fiber (no1) and the extraordinary ray refractive index (ne1), refractive index (n _matrix3) of the ordinary ray of the second fiber refractive index (no2) and the extraordinary ray refractive index (ne2), and said third support is The light guide plate which satisfy | fills following formula (4) and (5).

The method of claim 4, wherein
The light guide plate of the first fiber is arranged more densely away from the light incident surface. The method of claim 4, wherein
The second fiber has a light guide plate having a different density of arrangement depending on the arrangement position. The method of claim 4, wherein
The light guide plate, wherein some of the plurality of first and second fibers comprise discontinuous portions. The method of claim 4, wherein
The light guide plate, wherein some of the plurality of first and second fibers overlap. The method of claim 13,
The first and second fibers are light guide plates of different materials. A light source unit including a plurality of light sources spaced apart from each other; And
And a light guide plate emitting a polarization component of light incident from the light source unit.
The light guide plate is a surface light source device according to any one of claims 1 to 3. The method of claim 22,
The optical homogenization layer,
A plurality of second fibers having birefringence; And
And an isotropic second support for supporting the second fiber. The method of claim 23,
An array density of the second fibers is higher between the plurality of light sources than on the axis of the light irradiation direction of the light source. The method of claim 22,
And the plurality of light sources are divided on two opposing side surfaces of the light guide plate. The method of claim 23,
Any one selected from the light guide layer, the polarization separation layer and the light homogenization layer is provided between the remaining two. The method of claim 23,
A phase difference plate for converting a polarization direction of light in the light guide layer; And
And a reflector provided on a surface excluding the light incident surface and the light emitting surface of the light guide layer, and reflecting the light emitted from the light guide layer into the light guide layer. The method of claim 26,
And the polarization separation layer and the light homogenization layer are stacked on the light emitting surface of the light guide layer. The method of claim 28,
And the polarization separation layer and the light homogenization layer are integrated to form a single layer. The method of claim 29,
Wherein said first fiber and said second fiber in said monolayer are intersected and said first and second supports form a single third support for supporting said first and second intersected fibers. The method of claim 29,
A phase difference plate for converting a polarization direction of light in the light guide layer; And
And a reflector provided on a surface excluding the light incident surface and the light emitting surface of the light guide layer, and reflecting the light emitted from the light guide layer into the light guide layer. The method of claim 26,
The material of the said light guide layer is the same surface light source device as the material of at least one of the said 1st and 2nd support body. The method of claim 22,
And the first fiber is densely arranged away from the light incident surface. Light source device; And
A flat panel display comprising: a liquid crystal panel displaying an image by using light supplied from the light source device.
The light source device is a flat panel display as claimed in claim 22. The method of claim 34, wherein
The optical homogenization layer,
A plurality of second fibers having birefringence; And
And an isotropic second support for supporting the second fiber. The method of claim 1,
And the plurality of fibers are arranged to be parallel to the waveguide direction of light.

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