JP2009047762A - Optical element, layered optical member, surface light source element, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element having compatibly both a light guide function and a polarization separation function, capable of enhancing brightness, manufactured relatively easily, and hardly generating trouble such as delamination. <P>SOLUTION: The optical element 30 includes a support medium 4 having a pair of opposed faces 7, 8 opposed each other, and having an isotropic refractive index, and a plurality of double-refractors 5 arranged in the support medium 4, each double-refractor 5 is a column having 2 or more of aspect ratio that is a ratio of a major axis-directional length to a minor axis-directional length, and having 0.05 or more of refractive index difference between refractive indexes in a major axial direction and a minor axial direction, the plurality of double-refractors 5 is arrayed juxtaposedly along a face in substantial parallel to one opposed face to direct major axes of the respective double-refractors 5 each other to substantially the same direction, a difference between a refractive index of the support medium 4 and the refractive index either in the major axial direction or in the minor axial direction is 0.03 or less, and an irregular part 6 is formed on one face 8 out of the paired opposed faces. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses an optical element suitable for use in a mobile phone, a personal digital assistant (PDA), a video camera, a car navigation system, a personal computer, a computer monitor, a television receiver, an advertising signboard, and the like. The present invention relates to a laminated optical member, a surface light source element, and a liquid crystal display device.

  Liquid crystal display devices that have come to be widely used as medium- and large-sized display devices such as small display devices such as mobile phones, PDAs, video cameras, car navigation systems, personal computers, computer monitors, television receivers, advertising billboards, etc. A surface light source element (backlight) that emits light in a planar shape and a liquid crystal display panel that provides image information, and the light transmittance is controlled by the image information provided by the liquid crystal display panel, thereby allowing characters and images to be displayed. Is displayed.

  FIG. 1 shows a configuration of a general surface light source element 10. Light emitted from a light source 11 such as a cold cathode tube or a light emitting diode (LED) is incident on the left side surface of a light guide plate 12 made of a transparent material such as polymethyl methacrylate or cycloolefin polymer, and passes through the light guide plate 12. Propagate. A fine pattern portion 13 such as printed dots is disposed on the back surface of the light guide plate 12, and propagating light incident on the fine pattern portion 13 is diffused and emitted from the upper surface of the light guide plate 12. Since the emitted light is omnidirectional, by using a plurality of optical function sheets such as the diffusion plate 14, the prism sheet 15, and the brightness enhancement film 17, the light is condensed in the front direction to improve the brightness. . In the example shown in FIG. 1, one diffusing plate, two prism sheets in which each lens is orthogonal, and one brightness enhancement film are used. Further, a reflective plate 16 made of a metal-deposited film, foamed polyethylene terephthalate, or the like is disposed on the back side of the light guide plate 12, and fulfills the function of returning light emitted to the back side of the light guide plate 12 to the light guide plate 12 again. .

  Next, a general liquid crystal display panel will be described with reference to FIG. The liquid crystal display panel 20 is provided with a polarization functional layer 22 on the outer side of the liquid crystal cell 21. The polarizing functional layer 22 includes a polarizing plate 23 and an optical functional layer 24 such as a retardation film or a viewing angle widening film provided as necessary. The liquid crystal cell 21 includes two substrates 25 and 26, electrodes 27 and 28 provided inside each substrate, a liquid crystal layer 29 sealed between the two substrates, an alignment film, a spacer, and a color not shown. It consists of a filter. However, the configuration of the liquid crystal display panel is not limited to this, and various configurations can be made according to applications and requirements. By disposing the surface light source element 10 as shown in FIG. 1 below the liquid crystal display panel 20 of FIG. 2, that is, by adjoining the surface light source element 10 and the polarization functional layer 22, a liquid crystal display device is provided. Is configured.

  In the surface light source element 10 described above, the non-directional light can be condensed in the front direction using the diffusion plate 14 and the prism sheet 15. This is because light is refracted at the interface between the prism lens formed on the surface 15 and air. That is, the presence of an air layer on the surface of the diffuser plate 14 or the prism sheet 15 increases the difference in refractive index between the surfaces, thereby making it possible to collect omnidirectional light. On the other hand, since the surface has a refractive index difference, there is a problem that light returns to the light guide plate 12 side due to the influence of surface reflection, and as a result, the light utilization efficiency decreases. Further, in order to collect light in the front direction and increase the luminance, a plurality of diffusion plates 14 and prism sheets 15 must be laminated on the light guide plate 12, so that the process becomes complicated.

  In order to remove the influence of the surface reflection on the diffusion plate or the prism sheet, it is conceivable to bond the diffusion plate or the prism sheet and the light guide plate via an adhesive or an adhesive. Also, between the surface light source element and the polarizing functional layer, surface reflection may occur when an air layer is interposed. Therefore, for the purpose of preventing this reflection, the light source element and the polarizing functional layer are bonded together. It is possible to integrate them. As this example, it is known that a light guide plate and a polarizing functional layer are bonded and disposed, and a diffusion plate, a prism sheet, and the like are also disposed as necessary (for example, see Patent Documents 1 to 4). However, as shown in Patent Documents 1 to 4, it is considered difficult to condense light in the front direction only by adhering and arranging the light guide plate and the polarization functional layer. On the other hand, even if a diffuser plate or prism sheet is used for condensing, since the air layer does not intervene when they are bonded and arranged, the condensing function is also suppressed at the same time, so that the desired optical performance is achieved. I can't. Furthermore, since the polarization functional layer, the diffusion layer, and the prism sheet are laminated on the light guide plate, the complexity of the process is not improved.

  Further, a polarizing functional layer in which an optical functional layer such as a diffusion plate, a brightness enhancement film, and a light collecting film is bonded to a polarizing plate is known, and it is also known that a surface light source element can also be bonded ( For example, see Patent Document 5). According to the technique described in Patent Document 5, the yield can be improved and the thickness can be reduced. However, since the diffuser plate and the light-collecting film used have a function due to the difference in refractive index of the internal structure, sufficient optical performance is achieved. Cannot be achieved. Furthermore, since the polarization functional layer, the diffusion layer, the prism sheet, and the like are laminated on the light source as in Patent Documents 1 to 4, the complexity of the process is not improved.

  Furthermore, it is also known that the polarizing functional layer and the light guide plate are bonded together so that light reflection does not occur at the interface between them (see, for example, Patent Documents 6 and 7). However, in the techniques described in Patent Documents 6 and 7, reflection of light at the interface between the polarization functional layer and the light guide plate cannot be sufficiently prevented, and there is a risk that the light use efficiency may be reduced. It is considered that it cannot be used for a backlight for a transmissive liquid crystal display device that requires a viewing angle.

  In addition, a technique for bonding the polarization functional layer to the light guide plate is known (see, for example, Patent Document 8). The technique described in Patent Document 8 is intended to prevent sticking with other members, and to prevent the occurrence of curling and undulation during performance tests such as heat resistance. There is no mention of efficiency improvements.

  In view of the above problems, Patent Document 9 discloses a light guide plate for propagating light incident from one or more light sources provided on a side surface, a polarization functional layer that selectively transmits specific polarized light, and an output. A surface light source element with a polarization functional layer has been proposed, which includes a member in which an emission light control plate for controlling an emission angle of emitted light is laminated via an adhesive, an adhesive, or the like. However, in Patent Document 9, as in the techniques described in the above-mentioned Patent Documents, since a polarization functional layer, a diffusion layer, a prism sheet, and the like are stacked on the light guide plate, the complexity of the process is not improved.

On the other hand, WO 2005/008302 pamphlet (Patent Document 10) discloses a polygonal column or cylinder having an aspect ratio of 2 or more and a difference in refractive index between the major axis direction and the minor axis direction of 0.05 or more in a supporting medium. Describes a reflection type polarizing plate having a structure in which the same direction is distributed. The reflective polarizing plate described in Patent Document 10 has a polarization separation function, but at least a light guide plate is required to be used as a backlight, and control of light collection in the front direction is required. Therefore, depending on the case, it is necessary to laminate a diffusion layer and a prism sheet.
JP-A-9-189811 JP 10-319233 A Japanese Patent Laid-Open No. 11-2722 JP-A-11-52133 JP 2003-315545 A JP 2000-155315 A JP 2003-66236 A JP 2003-315548 A JP 2006-244803 A WO2005 / 008302 pamphlet

  In view of the above problems, an object of the present invention is to provide an optical system that has both a light guiding function and a polarization separation function, can improve luminance, is relatively easy to manufacture, and does not easily cause problems such as delamination. An element, a laminated optical member using the optical element, a surface light source element, and a liquid crystal display device are provided.

  To achieve the above object, an optical element according to the present invention includes a support medium having a pair of facing surfaces facing each other and having an isotropic refractive index, and a plurality of birefringent bodies disposed in the support medium. The birefringent body has an aspect ratio, which is a ratio of the length in the major axis direction to the length in the minor axis direction, of 2 or more, and the difference in refractive index between the major axis direction and the minor axis direction is 0. A plurality of birefringent bodies are arranged side by side along a plane substantially parallel to one opposing surface so that the major axes of the birefringent bodies are directed in substantially the same direction. The difference between the refractive index of the support medium and the refractive index of either the short axis direction or the long axis direction of the birefringent body is 0.03 or less, preferably 0.01 or less, An uneven portion is formed on one side.

  In the present invention, light incident on the optical element from the side surface that intersects the facing surface of the support medium is reflected by the uneven portion formed on one side of the facing surface of the support medium, and the front direction (the uneven portion is Since the light is guided to the opposite surface side opposite to the formed surface, the optical element functions as a light guide plate.

  In the present invention, when the difference between the refractive index of the support medium and the refractive index in the minor axis direction of the birefringent body is 0.03 or less, of the light reflected at the concavo-convex portion and guided in the front direction, Linearly polarized light oscillating in a direction substantially parallel to the major axis direction of the birefringent body is reflected at the interface between the birefringent body and the support medium, and is substantially perpendicular to the major axis direction of the birefringent body (the minor axis of the birefringent body). The linearly polarized light that vibrates in a direction substantially parallel to the direction passes through the optical element. As a result, only linearly polarized light that vibrates in a direction substantially parallel to the minor axis direction of the birefringent body can pass through the optical element. In addition, when the difference between the refractive index of the support medium and the refractive index in the major axis direction of the birefringent body is 0.03 or less, linearly polarized light that vibrates in a direction substantially parallel to the minor axis direction of the birefringent body is birefringent. Linearly polarized light that is reflected at the interface between the body and the support medium and vibrates in a direction substantially perpendicular to the minor axis direction of the birefringent body (direction substantially parallel to the major axis direction of the birefringent body) is transmitted through the optical element. As a result, only linearly polarized light that vibrates in a direction substantially parallel to the major axis direction of the birefringent body can pass through the optical element. Therefore, the optical element exhibits a polarization separation function.

  As described above, the optical element of the present invention can have both a light guide function and a polarization separation function, and can improve luminance.

  Moreover, since the present invention does not require a light guide plate and a polarizing plate to be laminated as in the prior art, the production is relatively simple and problems such as delamination are unlikely to occur. Further, unlike the prior art, light is not reflected at the interface between the light guide plate and the polarizing plate, so that the light utilization efficiency can be improved.

  In the birefringent body, the cross-sectional shape perpendicular to the major axis direction is preferably substantially polygonal or circular, more preferably substantially triangular, and even more preferably substantially equilateral.

  By making the shape of the cross section perpendicular to the major axis direction of the birefringent body substantially triangular, in particular, substantially equilateral triangle, the birefringent body functions as a prism, and the optical element can have a condensing function. In addition, the birefringent body can be easily manufactured by making the shape of the cross section perpendicular to the major axis direction of the birefringent body into a triangle having a small number of vertices, particularly a regular triangle.

  The birefringent body is preferably a fiber.

  As a result, the birefringent body can be easily and highly oriented in the support medium, and the birefringence of the birefringent body is effectively exhibited.

  It is preferable that the concavo-convex portion is a wedge-shaped groove or a V-shaped groove, and a plurality of the wedge-shaped grooves or the V-shaped grooves are formed substantially parallel to the minor axis direction of the birefringent body. As a result, the light incident on the optical element from the long axis direction of the birefringent body is reflected by the wedge-shaped groove or the V-shaped groove, and the front direction (the surface on which the wedge-shaped groove or the V-shaped groove is formed) Can be guided well to the opposite surface side).

  The pitch between the plurality of wedge-shaped grooves or the V-shaped grooves is preferably 10 μm or more, and more preferably 20 μm or more. Thereby, the light incident into the optical element can be guided well in the front direction (on the opposite surface side to the surface on which the wedge-shaped grooves or V-shaped grooves are formed).

  The laminated optical member according to the present invention is formed by laminating the optical element and an optical layer exhibiting another optical function. The optical layer laminated on the optical element is preferably a diffusion plate, a prism sheet, or a brightness enhancement film.

  In the laminated optical member, it is preferable that a diffusion plate is laminated on the optical element, and a prism sheet is laminated on the diffusion plate. Alternatively, in the laminated optical member, it is preferable that a diffusion plate is laminated on the optical element, a prism sheet is laminated on the diffusion plate, and a brightness enhancement film is laminated on the prism sheet.

  A surface light source element according to the present invention includes the optical element or the laminated optical member, a light source disposed on a surface perpendicular to one side of a support medium on which an uneven portion is formed in the optical element or the laminated optical member, and the optical element. Alternatively, the laminated optical member includes a reflector disposed on one side of the support medium on which the concavo-convex portion is formed.

  A liquid crystal display device according to the present invention includes the optical element, the laminated optical member, or the surface light source element, and a liquid crystal cell.

  According to the present invention, an optical element that has both a light guide function and a polarization separation function, can improve luminance, is relatively easy to manufacture, and hardly causes problems such as delamination, and the optical element is used. The laminated optical member, the surface light source element, and the liquid crystal display device can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments.

(Optical element)
As shown in FIG. 3, the optical element 30 according to the present embodiment has a pair of facing surfaces 7 and 8 that face each other, and side surfaces 9a, 9b, 9c, and 9d that are side surfaces of the facing surfaces 7 and 8. A support medium 4 having an isotropic refractive index and a plurality of birefringent bodies 5 disposed in the support medium 4 are provided. Further, an uneven portion 6 is formed on one surface 8 of the pair of opposed surfaces 7 and 8. Further, the side surface 9a and the side surface 9b face each other, and the side surface 9c and the side surface 9d face each other. The side surface 9a is an incident surface for the light L, and the opposite surface 7 opposite to the one surface 8 on which the concavo-convex portion 6 is formed is an output surface for the light L.

  The uneven portion 6 is preferably a wedge-shaped groove or a V-shaped groove, and a plurality of wedge-shaped grooves or V-shaped grooves are preferably formed substantially parallel to the minor axis direction of the birefringent body 5. As a result, the light incident on the optical element 3 from the side surface 9a side (long axis direction of the birefringent body 5) is reflected by the wedge-shaped groove or the V-shaped groove on the one surface 8 side, and the front direction (opposing surface 7). In the normal direction). The wedge-shaped groove means a V-shaped groove in which the cross-sectional shape of the groove is asymmetric.

  The wedge-shaped grooves or V-shaped grooves may or may not be arranged at an equal pitch (interval). Further, the pitch (interval) P between a plurality of wedge-shaped grooves or between V-shaped grooves (as shown in FIG. 3 is a distance from a predetermined portion of a certain groove to a corresponding portion of a groove adjacent thereto, for example, The distance from the bottom of a certain groove to the bottom of the groove adjacent to the groove is preferably 10 μm or more, and more preferably 20 μm or more. As a result, the light incident into the optical element 30 can be favorably guided in the front direction (normal direction of the facing surface 7). When the pitch is less than 10 μm, the light incident into the optical element 30 is difficult to propagate in the front direction (on the facing surface 7 side), and the luminance tends to decrease.

  As for the dimensions of the wedge-shaped groove or the V-shaped groove, the depth of the groove is preferably 5 μm or more, more preferably 10 μm or more, and the width of the groove is preferably 10 μm or more. As a result, the wedge-shaped groove or the V-shaped groove functions geometrically and can reflect and refract light well. If the size of the wedge-shaped groove or the V-shaped groove is too small, the wedge-shaped groove or the V-shaped groove tends to function as a scattering optical. Note that the depth, width, and apex angle of the wedge-shaped groove or V-shaped groove may be uniform or non-uniform. Or the uneven | corrugated | grooved part 6 may be a wedge-shaped or V-shaped protruding item | line, and may be a dot-shaped recessed part and a convex part.

  The film thickness of the optical element 30 is not particularly limited, but is usually in the range of 1 to 3000 μm, preferably 5 to 1000 μm, more preferably 10 to 200 μm. If the optical element 30 is too thin, the polarization separation function tends not to be exhibited. Conversely, if the optical element 30 is too thick, the amount of light absorbed by the optical element 30 tends to increase and the material cost tends to increase. However, these phenomena can be suppressed by setting the film thickness of the optical element 30 within the above range.

  The birefringent body 5 is a column having an aspect ratio of 2 or more, which is a ratio of the length in the major axis direction to the length in the minor axis direction, and the aspect ratio is preferably 5 or more. It is more preferable. For example, a fiber having the above aspect ratio may be used as the birefringent body 5. By using fibers as the birefringent body 5, the birefringent body can be easily and highly oriented in the support medium, and the birefringence of the birefringent body is effectively expressed.

  In this embodiment, when the cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 is a polygon, the length in the minor axis direction (short axis diameter) of the birefringent body 5 is the circumscribing of the polygon. It is defined as the diameter of the circle. When the cross-sectional shape of the birefringent body 5 is a circle, the length in the minor axis direction (minor axis diameter) is defined as the diameter of the circle.

  The refractive index difference between the major axis direction and the minor axis direction (diameter direction of the polygonal circumscribed circle or circle diameter direction) of the birefringent body 5 is 0.05 or more, preferably 0.1 or more. Preferably it is 0.2 or more.

  The plurality of birefringent bodies 5 have a major axis of each birefringent body 5 in substantially the same direction (Z direction) along a plane substantially parallel to one of the opposing surfaces 7 or 8 (hereinafter referred to as an array plane). ) Are aligned side by side. The birefringent body 5 is preferably packed densely in the support medium 4. Note that “substantially the same direction” means not only the case where a plurality of birefringent bodies 5 are completely directed in the same direction, but also the other birefringent body 5 is ± 10 with respect to one reference birefringent body 5. It is an acceptable concept even when it is tilted within a range of about °. The major axis direction of the birefringent body 5 and the side surfaces 9c and 9d of the support medium 4 are substantially parallel, and the major axis direction of the birefringent body 5 and the side surfaces 9a and 9b intersect, preferably orthogonally.

  The difference between the refractive index of the support medium 4 and the refractive index of either the short axis direction or the long axis direction of the birefringent body 5 is 0.03 or less, and preferably 0.01 or less.

  For example, when the difference between the refractive index of the support medium 4 and the refractive index in the minor axis direction of the birefringent body 5 is set to 0.03 or less, and both refractive indexes are substantially matched, the birefringent body 5 is almost in the minor axis direction. Only linearly polarized light that vibrates in parallel passes through the facing surface 7 of the optical element 30. Further, since the birefringent body 5 has birefringence, the refractive index in the major axis direction of the birefringent body 5 does not match the refractive index of the support medium 4. As a result, the linearly polarized light that vibrates in the major axis direction of the birefringent body 5 is reflected at the interface between the birefringent body 5 and the support medium 4. Thus, when the difference between the refractive index of the support medium 4 and the refractive index in the minor axis direction of the birefringent body 5 is 0.03 or less, in the optical element 30, the minor axis direction of the birefringent body 5 is light. Becomes the transmission axis.

  When the short axis direction of the birefringent body 5 is the light transmission axis, the difference between the refractive index of the long axis direction of the birefringent body 5 and the refractive index of the support medium 4 is preferably 0.05 or more, It is more preferably 0.1 or more, and further preferably 0.2 or more. The greater the difference in refractive index, the more efficiently the linearly polarized light that vibrates in the major axis direction of the birefringent body 5 can be reflected, and the film thickness of the optical element 30 can be reduced.

  Thus, when the difference between the refractive index of the support medium 4 and the refractive index in the minor axis direction of the birefringent body 5 is 0.03 or less, the optical element 30 is substantially parallel to the minor axis direction of the birefringent body 5. It is possible to have a polarization separation function that transmits linearly polarized light that vibrates in any direction and reflects linearly polarized light that vibrates in a direction substantially parallel to the long axis direction of the birefringent body 5.

  On the other hand, when the difference between the refractive index of the support medium 4 and the refractive index in the major axis direction of the birefringent body 5 is set to 0.03 or less, and both refractive indexes are substantially matched, the birefringent body 5 is almost in the major axis direction. Only linearly polarized light that vibrates in parallel passes through the facing surface 7 of the optical element 30. Further, since the birefringent body 5 has birefringence, the refractive index in the minor axis direction of the birefringent body 5 does not match the refractive index of the support medium 4. As a result, the linearly polarized light that vibrates in the minor axis direction of the birefringent body 5 is reflected at the interface between the birefringent body 5 and the support medium 4. Thus, when the difference between the refractive index of the support medium 4 and the refractive index in the major axis direction of the birefringent body 5 is 0.03 or less, the major axis axis direction of the birefringent body 5 in the optical element 30 is It becomes the transmission axis of light.

  When the major axis direction of the birefringent body 5 is the light transmission axis, the difference between the refractive index of the birefringent body 5 in the minor axis direction and the refractive index of the support medium 4 is preferably 0.05 or more, It is more preferably 0.1 or more, and further preferably 0.2 or more. As the refractive index difference is larger, the linearly polarized light that vibrates in the minor axis direction of the birefringent body 5 can be reflected more efficiently, and the film thickness of the optical element 30 can be reduced.

  As described above, when the difference between the refractive index of the support medium 4 and the refractive index of the birefringent body 5 in the major axis direction is 0.03 or less, the optical element 30 is substantially parallel to the major axis direction of the birefringent body 5. It is also possible to have a polarization separation function that transmits linearly polarized light that vibrates in any direction and reflects linearly polarized light that vibrates in a direction substantially parallel to the minor axis direction of the birefringent body 5.

  The number of layers of the birefringent body 5 in the support medium 4 is preferably 3 or more, more preferably 5 or more in the thickness direction (Y direction) of the support medium 4. Even when it is difficult to make perfect parallel light perpendicularly incident on the arrangement surface of the birefringent body 5, the optical element 30 can obtain a relatively high polarization separation function by securing the number of layers. Can do.

  Note that when the parallel light is perpendicularly incident on the arrangement surface of the birefringent body 5 and the thickness of the optical element 30 is such that the scattering factor does not need to be taken into consideration, the number of stacked birefringent bodies 5 May be appropriately selected from about 1 to 100 layers, and the optical element 30 can obtain a relatively high polarization separation function even if the number of layers of the birefringent body 5 is only one.

  The cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 is preferably substantially polygonal or substantially circular, more preferably substantially triangular, and more preferably substantially equilateral triangle. In the present embodiment, for convenience of illustration, the cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 is a circle. When the shape of the cross section perpendicular to the major axis direction of the birefringent body 5 is a triangle similar to the apex angle shape of the prism sheet, particularly a regular triangle, the birefringent body 5 functions as a prism, and the optical element 30 Can have a condensing function. In addition, when the cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 is a triangle having a small number of vertices, particularly a regular triangle or a circle, the birefringent body 5 can be easily manufactured.

  The “substantially polygon” in the present embodiment includes not only a regular polygon but also a range in which the angle of each vertex of the regular polygon is about ± 10 ° when the regular polygon is used as a reference. Also included is a figure that includes a figure that fluctuates within the range, and that the length of one side of the regular polygon is based on the length of one side of the regular polygon and the length of the other side fluctuates within a range of about ± 10%. It is a concept that includes not only a figure in which each side is a straight line but also a figure in which each side is slightly curved. Similarly, the “substantially equilateral triangle” in the present embodiment includes not only the equilateral triangle but also the angle of each vertex of the equilateral triangle varies within a range of about ± 10 ° when the equilateral triangle is used as a reference. Including a figure, and also including a figure in which the length of one side of the regular triangle varies within a range of about ± 10% with respect to the length of one side of the equilateral triangle, It is a concept that encompasses not only figures in which each side is a straight line but also figures in which each side is slightly curved. For example, when manufacturing the fiber of the birefringent body 5, each side of the cross section of the fiber may be slightly curved. Further, in this embodiment, when “almost” is given when representing a predetermined angle or a predetermined side length, an angle within a range of about ± 10 ° around the predetermined angle, or a predetermined This means that a side length within a range of about ± 10% around the side length is allowed.

  In addition, “substantially a circle” in the present embodiment is not only an ellipse having an ellipticity of 1 representing the ratio of the major axis to the minor axis (that is, a perfect circle), but also having an ellipticity of about 1 ± 0.1. It is a concept that allows an ellipse inside. For example, when manufacturing the fiber of the birefringent body 5, the cross section may have some ellipticity. The ellipticity of the cross section perpendicular to each major axis direction of the birefringent body 5 is preferably 1 (the cross section is a perfect circle).

  The length of one side of the polygon which is a cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 or the diameter of the circle is usually larger than the wavelength of visible light, preferably 1 μm or more, more preferably 5 μm or more. It is. When the length of one side of the polygon or the diameter of the circle is less than 1 μm, the polarization separation function tends to deteriorate.

  Note that the facing surface 7 and the facing surface 8 of the support medium 4 do not have to be parallel. For example, the optical element 30 may have a wedge shape in which the thickness of the side surface 9a is larger than the thickness of the side surface 9b.

(Material of birefringent body 5)
In principle, various materials exhibiting birefringence can be used as the birefringent body 5, but from the viewpoints of orientation in the support medium 4, stability of the cross-sectional shape, durability, etc., the birefringent body 5 is solid. It is preferable that Among substances that meet such conditions, the birefringent body 5 is made of continuous fiber because it can be easily and highly oriented in the support medium 4 and birefringence is effectively expressed. It is preferable that

  Specific fibers used as the birefringent body 5 include polyolefin and vinyl fibers such as polyethylene, polytetrafluoroethylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, polyacrylonitrile, and poly (4-methyl-1-pentene). , Aliphatic polyamide fibers such as nylon 6, nylon 66 and nylon 46, aromatic polyamide fibers (aramid fibers) such as poly (m-phenylene isophthalamide) and poly (p-phenylene terephthalamide), polyethylene terephthalate and polyethylene For products with product names such as naphthalate, polyester fiber such as poly-ε-caprolactone, “Vectra” sold by Polyplastics, and “Sumika Super” sold by Sumitomo Chemical. Be represented Hetero atoms such as aromatic liquid crystalline polyester fiber, poly (p-phenylenebenzobisoxazole), poly (p-phenylenebenzobisthiazole), polybenzimidazole, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone Examples thereof include fibers, polyimide fibers such as polypyromellitimide, cellulose fibers such as rayon, acrylic fibers such as poly (methyl methacrylate), polycarbonate fibers, and urethane fibers. Among these, it is particularly preferable to use a fiber having an aromatic ring such as a benzene ring or a naphthalene ring and having little or no absorption in the visible light region as the birefringent body 5.

  For the purpose of improving the adhesion between the birefringent body 5 and the support medium 4, the surface of the fiber of the birefringent body 5 may be subjected to various easy adhesion treatments such as corona treatment. Further, for the purpose of improving the birefringence of the fibers of the birefringent body 5, a filler having shape anisotropy such as a low molecular liquid crystal compound or a whisker is added to the birefringent body 5, or the birefringent body 5. Alternatively, a multifilament type polymer inter-array fiber may be used.

  The low molecular liquid crystal compounds added to the fibers of the birefringent body 5 in order to improve the birefringence of the birefringent body 5 include biphenyl, phenylbenzoate, cyclohexylbenzene, azoxybenzene, azobenzene, and azomethine. Compounds having a mesogen (a core unit for expressing liquid crystallinity in a molecular structure) such as benzene, terphenyl, biphenylbenzoate, cyclohexylbiphenyl, phenylpyrimidine, cyclohexylpyrimidine, and cholesterol. The These low-molecular liquid crystal compounds may be dissolved in the fibers or may exist in the domain as long as they are aligned in the long axis direction of the fibers of the birefringent body 5. However, when it exists in a domain, the diameter of the domain is preferably 0.2 μm or less. When the domain diameter is larger than 0.2 μm, the linearly polarized light that vibrates in the direction perpendicular to the long axis of the fiber of the birefringent body 5 tends to be scattered.

  The whisker added to the fiber for the purpose of improving the birefringence of the birefringent body 5 includes sapphire, silicon carbide, boron carbide, silicon nitride, boron nitride, aluminum borate, graphite, potassium titanate, poly Examples include oxymethylene, poly (p-oxybenzoyl), poly (2-oxy-6-naphthoyl) and the like. These whiskers preferably have an average cross-sectional diameter in the range of 0.05 to 0.2 μm. When the average diameter is larger than 0.2 μm, as in the case of the low-molecular liquid crystal compound, linearly polarized light that vibrates in the direction perpendicular to the long axis of the fiber of the birefringent body 5 is scattered, or whisker causes the birefringent body 5 Protrusions may be formed on the fiber surface.

  In the case where a polymer inter-array fiber is used as the birefringent body 5, the polymer inter-array fiber is an array in which island components are dispersed in a sea component. In this case, it is preferable that one of the refractive index in the major axis direction and the minor axis direction of the island component is substantially the same as the refractive index of the sea component. Also in this case, the island component preferably has a diameter of 0.2 μm or less. The island component is preferably present in the sea component at 2 or more, more preferably 4 or more. In addition, a filler having shape anisotropy such as a low-molecular liquid crystal or a whisker may be added to the island component.

(Material of support medium 4)
The material used as the support medium 4 plays a role of fixing the birefringent body, has little or no absorption in the visible light region (transparent in the visible light region), and further birefringent body 5 (fibers). Any material may be used as long as it exhibits good adhesion to the above. Further, as the support medium 4, the difference between the refractive index of the support medium 4 and the refractive index of either the short axis direction or the long axis direction of the birefringent body 5 is 0.03 or less, preferably 0.01. The following materials are used. As such a support medium 4, the following transparent resin can be used. Specifically, acrylic resin such as poly (methyl methacrylate), polyolefin such as polyethylene, polyester such as polyethylene terephthalate, polyether such as polyphenylene oxide, vinyl resin such as polyvinyl alcohol, polyurethane, polyamide, polyimide, epoxy resin, etc. A copolymer using two or more kinds of monomers constituting the above, further a mixture of poly (methyl methacrylate) and polyvinyl chloride in a weight ratio of 82:18, a mixture of poly (methyl methacrylate) and polyphenylene oxide in a weight ratio of 65:35, Non-birefringent polymer blends such as a 71:29 weight ratio mixture of polystyrene and polyphenylene oxide, and a 77:23 weight ratio mixture of styrene / maleic anhydride copolymer and polycarbonate are supported by the support medium. It is exemplified as 4, but not limited thereto. In order to obtain the support medium 4 having a high refractive index, an organic sulfur compound may be used. Examples of organic sulfur compounds include photocuring such as bis (4-methacryloylthiophenyl) sulfide, bis (4-vinylthiophenyl) sulfide, bis [4- (2,3-epoxypropylthio) phenyl] sulfide. However, the present invention is not limited to these. In order to adjust the refractive index of the support medium 4, the aforementioned monomers may be used in combination with other photocurable or thermosetting monomers. These materials for the support medium 4 are polymerization initiators, antioxidants, light stabilizers, heat stabilizers, lubricants, dispersants, ultraviolet absorbers, white pigments, fluorescent whitening agents, as long as the above-mentioned properties are not impaired. An additive such as may be included.

  It should be noted that the composition ratio of the fibers constituting the birefringent body 5 and the substance constituting the support medium 4 is such that even if the cross-sectional shape perpendicular to the major axis direction of the birefringent body 5 is a polygon or a circle, There is no particular limitation as long as it is effectively fixed in the support medium 4.

(Method for manufacturing optical element 30)
In the manufacture of the optical element 30, for example, first, a fiber that is the birefringent body 5 is spun and stretched, and then a nonwoven fabric in which the birefringent body 5 is arranged in one direction is produced. Further, the non-woven fabric of the birefringent body 5 is impregnated with the support medium 4 and fixed to form a structure having a pair of opposed surfaces facing each other. Next, the optical element 30 is obtained by surface-treating one of the pair of opposing surfaces to form the concavo-convex portion 6. In this way, the optical element 30 is formed through four stages of spinning / stretching, nonwoven fabric preparation, impregnation, and surface treatment.

  The spinning / stretching process of the fiber which is the birefringent body 5 and the manufacturing process of the nonwoven fabric may be performed by a known method, and are not particularly limited. As a method of impregnating the non-woven fabric with the support medium 4 and fixing it, the non-woven fabric is immersed in the monomer and / or oligomer which is the precursor of the support medium 4, and then the precursor of the support medium 4 is polymerized by light and / or heat. A method in which the nonwoven fabric is immersed in the polymer solution of the support medium 4 and then the solvent is removed, or the support medium 4 is made into a fine powder, the fine powder is impregnated into the nonwoven fabric, and then the support medium 4 is melted. The method etc. are mentioned. The surface treatment method for forming the concavo-convex portion 6 is not particularly limited, and examples include groove cutting and groove formation with a mold.

  Moreover, the manufacturing method of the optical element 30 is not limited to the above-mentioned thing. For example, the optical element 30 may be manufactured by a melt extrusion method. Specifically, first, when the cross-sectional shape perpendicular to the major axis direction of the birefringent bodies 5 dispersed and arranged in the support medium 4 is a polygon, the discharge port of the extruder is divided by a number of bases. Alternatively, it is possible to adopt a profile extrusion method in which the resin constituting the birefringent body 5 is extruded from every other die into a polygonal shape, and the resin constituting the support medium 4 is extruded from the die between them. After obtaining the structure composed of the support medium 4 in which a plurality of birefringent bodies 5 are arranged by this profile extrusion method, unevenness is shaped on one of a pair of opposed surfaces of the structure. Thereby, the uneven part 6 is formed, and the optical element 30 is obtained. When the shape of the cross section perpendicular to the major axis direction of the birefringent body 5 dispersed and arranged in the support medium 4 is substantially a circle, the discharge port of the extruder is divided by a number of bases, It is possible to adopt a profile extrusion method in which the resin constituting the birefringent body 5 is extruded in a round bar shape from a die that is continuous in the cross section, and the resin constituting the support medium 4 is extruded from the die between them. After obtaining the structure composed of the support medium 4 in which a plurality of birefringent bodies 5 are arranged by this profile extrusion method, unevenness is shaped on one of a pair of opposed surfaces of the structure. Thereby, the uneven part 6 is formed, and the optical element 30 is obtained. In these extrusion methods, different types of molten resins are alternately extruded in a predetermined form from the die of the extruder so that the optical element 30 having the above-described dispersion arrangement structure of the birefringent body 5 is formed. What is necessary is just to design an extruder and a nozzle | cap | die.

  In the present embodiment, the light incident from the side surface 9a of the optical element 30 is reflected by the concavo-convex portion 6 formed on one side 8 of the opposing surfaces 7 and 8 of the support medium 4, and the front direction (the concavo-convex portion 6 is The light is guided in the normal direction of the opposing surface 7 opposite to the formed one surface 8.

  Moreover, in this embodiment, when the difference between the refractive index of the support medium 4 and the refractive index in the minor axis direction of the birefringent body 5 is 0.03 or less, the light is reflected at the concavo-convex portion 6 and guided in the front direction. Linearly polarized light that oscillates in a direction substantially parallel to the major axis direction of the birefringent body 5 is reflected at the interface between the birefringent body 5 and the support medium 4 and is substantially orthogonal to the major axis direction of the birefringent body 5. The linearly polarized light that vibrates in the direction (direction substantially parallel to the minor axis direction of the birefringent body 5) passes through the optical element 30. Further, when the difference between the refractive index of the support medium 4 and the refractive index in the major axis direction of the birefringent body 5 is 0.03 or less, linearly polarized light that vibrates in a direction substantially parallel to the minor axis direction of the birefringent body 5. Is reflected at the interface between the birefringent body 5 and the support medium 4, and linearly polarized light oscillating in a direction substantially perpendicular to the minor axis direction of the birefringent body 5 (direction substantially parallel to the major axis direction of the birefringent body 5) is The light passes through the optical element 30. As a result, only one of the linearly polarized light that vibrates in the short axis direction of the birefringent body 5 and the linearly polarized light that vibrates in a direction substantially parallel to the long axis direction of the birefringent body 5 may pass through the optical element 30. it can. Further, the light reflected at the interface between the birefringent body 5 and the support medium 4 is depolarized due to scattering inside the optical element 30 and reflection on the reflecting plate facing the facing surface 8, so that the light can be reused. It becomes possible.

  Thus, the optical element 30 of this embodiment can have both a light guide function and a polarization separation function.

  In addition, since the present embodiment does not require the light guide plate and the polarizing plate to be laminated as in the prior art, the manufacturing is relatively simple and problems such as delamination are unlikely to occur. That is, it is possible to reduce and eliminate the complexity of the laminating process by consolidating the light guiding function and the polarization separating function into one optical element 30 without laminating the light guide plate and the polarizing plate as in the prior art. . Further, unlike the prior art, light is not reflected at the interface between the light guide plate and the polarizing plate, so that the light use efficiency can be improved.

  In this embodiment, since the interface between the support medium 4 and the birefringent body 5 is not a simple plane, even if the materials of the support medium 4 and the birefringent body 5 are different from each other, the support medium 4 and the birefringent body 5 hardly peel off.

  In the present embodiment, since the support medium 4 to which the birefringent body 5 is fixed is made of an optically isotropic material, the volume fraction of the birefringent body 5 in the optical element 30 is increased. The accompanying decrease in the strength of the optical element 30 can be suppressed as compared with the conventional case. Therefore, it becomes easy to increase each volume fraction of the birefringent body 5.

  Further, in the present embodiment, the birefringent body functions as a prism by making the cross-sectional shape perpendicular to the major axis direction of the birefringent body substantially a triangle, particularly a substantially regular triangle, and the optical element 30 has a condensing function. The light emitted from the opposing surface 7 can be condensed in the normal direction of the opposing surface 7.

(Laminated optical member)
The optical element 30 according to the present embodiment can be used as a laminated optical member by laminating an optical layer showing another optical function on at least one surface when used. For the purpose of forming a laminated optical member, examples of the optical layer laminated on the optical element 30 include a diffusion plate, a prism sheet, and a brightness enhancement film. By laminating these optical layers on the optical element 30, it is possible to control the light collection more precisely, improve visibility, and use efficiency of light such as backlight light of the liquid crystal display device. It is possible to obtain a laminated optical member that can improve the thickness.

  In the laminated optical member in which the diffusing plate is laminated on the optical element 30, the control of the light collection can be made more precise. For example, if a diffuser plate having a high haze (cloudiness value) is used, the luminance on the front side is reduced, but the luminance on the wide viewing angle side is increased. On the other hand, if a diffusion plate having a low haze is used, the luminance on the wide viewing angle side can be improved while suppressing the reduction of the luminance on the front side. By adjusting the haze in this way, it is possible to control light collection more precisely.

  Even with a laminated optical member in which a prism sheet is laminated on the optical element 30, the control of light collection can be made more precise. For example, the degree of light collection can be changed by changing the apex angle of the prism sheet. In addition, by using one prism sheet, the degree of light collection can be changed in the rotation direction around the ridgeline. Furthermore, if two prism sheets are laminated on the optical element 30 so that the respective ridge lines are orthogonal to each other, the degree of light collection can be changed in the rotation direction around each ridge line. The ridge line direction of the prism sheet can be set so as to maximize the light utilization efficiency corresponding to the direction of emission from the light source.

  In the laminated optical member in which the brightness enhancement film is laminated on the optical element 30 according to this embodiment, the light use efficiency can be further improved. An example of the brightness enhancement film is a “DBEF” film (manufactured by 3M). When this film is used, the refractive index of the birefringent body 5 of the optical element 30 is substantially the same as the refractive index of the support medium 4 (in the optical element 30). The transmission axis direction) is preferably parallel to the transmission axis of the “DBEF” film.

  In the laminated optical member in which the diffusion plate is laminated on the optical element 30 and the prism sheet is laminated on the diffusion plate, compared with the case where any one of the diffusion plate and the prism sheet is laminated on the optical element 30. Further, it is possible to control the light collection more precisely.

  As shown in FIG. 4, a laminated optical member 32 in which a diffusion plate 14 is laminated on an optical element 30, a prism sheet 15 is laminated on the diffusion plate 14, and a brightness enhancement film 17 is laminated on the prism sheet 15. Then, compared with the case where any one type or both of the diffuser plate 14 and the prism sheet 15 are laminated, the light condensing can be controlled more precisely, and the light utilization efficiency can be further improved.

  In producing the laminated optical member described above, the optical element 30 and another optical layer are integrated using an adhesive. The adhesive used for this purpose is not particularly limited as long as the adhesive layer is satisfactorily formed. However, from the viewpoint of easy adhesion work and prevention of optical distortion, it is also known as a pressure-sensitive adhesive (also called a pressure-sensitive adhesive). ) Is preferably used.

  Specific examples of the pressure-sensitive adhesive include those based on acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and the like. In particular, like acrylic pressure-sensitive adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to the substrate, and has weather resistance, heat resistance, etc. It is preferable to select and use one that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group with 20 or less carbon atoms, such as methyl, ethyl and butyl groups, and (meth) acrylic acid and (meth) acrylic acid An acrylic monomer having a weight average molecular weight of 100,000 or more obtained by blending and polymerizing a functional group-containing acrylic monomer composed of hydroxyethyl or the like so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower. System copolymers are useful as the base polymer.

  When forming an adhesive layer made of an adhesive on the optical element 30, for example, a 10 to 40 wt% solution is prepared by dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate. The pressure-sensitive adhesive layer may be formed by directly coating on the optical element 30, and the pressure-sensitive adhesive layer is formed on a film that has been subjected to a release treatment in advance, and then transferred onto the optical element 30. An adhesive layer may be formed. The thickness of the pressure-sensitive adhesive layer is appropriately determined according to the adhesive force and the like, but is usually in the range of 1 to 50 μm.

  In addition, the adhesive layer may contain fillers made of glass fibers, glass beads, resin beads, metal powders and other inorganic powders, pigments, colorants, antioxidants, UV absorbers, etc. as necessary. May be. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

(Surface light source element)
As shown in FIG. 4, the surface light source element 31 according to the present embodiment includes a laminated optical member 32 including an optical element 30 and a support medium 4 in which the uneven portion 6 is formed in the optical element 30 included in the laminated optical member 32. You may provide the light source 17 arrange | positioned at the surface perpendicular | vertical to one side, and the reflecting plate 16 arrange | positioned at the single side | surface side of the support medium 4 in which the uneven | corrugated | grooved part 6 was formed in the optical element 30. In the surface light source element 31, the diffusion plate 14, the prism sheet 15, and the brightness enhancement film 17 may be omitted. As shown in FIG. 4, by arranging the light source at a position where the light is introduced into the optical element 30 from the long axis direction of the birefringent body 5, the light can easily enter the optical element 30. Therefore, it is possible to obtain the surface light source element 31 that easily guides the incident light in the front direction and has high light use efficiency. Further, by providing the reflecting plate 16 under the optical element 30 (on the concave-convex portion 6 side), the light can be reflected to the optical element 30 side so that the light can be reused, and the luminance of the surface light source element 31 is improved. be able to.

  The optical element 30, the laminated optical member 32 provided with the optical element 30, and the surface light source element 31 provided with the laminated optical member 30 are a personal computer, a word processor, an engineering workstation, a portable information terminal, and a navigation system. It can be suitably used for display screens using liquid crystal cells, such as liquid crystal televisions and video, and can realize light guiding in the front direction, polarization separation, improvement of luminance, and reduction of power consumption, optical The layer stacking process can be reduced, and the manufacturing can be made easier than before.

(Liquid crystal display device)
The liquid crystal display device according to the present embodiment includes the optical element 30, the laminated optical member 32, or the surface light source element 31, and a liquid crystal cell. As a result, it is possible to improve the utilization efficiency of the backlight light, increase the luminance, and reduce the power consumption.

  The liquid crystal cell used in the liquid crystal display device is not particularly limited. For example, various liquid crystals such as an active matrix drive type liquid crystal cell typified by a thin film transistor type and a simple matrix drive type liquid crystal cell typified by a super twisted nematic type. A liquid crystal display device can be formed using the cell.

  The preferred embodiments of the optical element 30, the laminated optical member 32 using the optical element 30, the surface light source element 31, and the liquid crystal display device according to one embodiment of the present invention have been described above. However, the present invention is not limited to the embodiment.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

<Example 1>
In Example 1, a surface light source element composed of two layers of optical element / reflecting plate was produced by the following procedure.

  First, from a pellet of polyethylene terephthalate (PET) resin (manufactured by Unitika), the cross-sectional shape is approximately a regular triangle, the fiber diameter (triangular circumscribed circle diameter) is 19 μm, and the refractive index in the fiber width direction (short axis direction) is 1. 528, a fiber (birefringent body) having a refractive index in the fiber axis direction (major axis direction) of 1.730, a birefringence of 0.202, and an aspect ratio of 2 or more was produced.

This fiber was wound around a slide glass as densely as possible to produce a birefringent array (birefringent array). On one side of this birefringent array, an ultraviolet curable resin “Aronix” manufactured by Toagosei Co., Ltd. having the same refractive index as the refractive index in the fiber width direction as a supporting medium (product number: UVX-4568, refractive index 1. 528, photopolymerization initiator “IRGACURE184” (made by Ciba Specialty Chemicals Co., Ltd., 5 wt%) was applied, and this was irradiated with ultraviolet rays having a wavelength of 365 nm at an intensity of 1031 mW / cm ² and an integrated light amount of 880 mJ / cm ^2. The UV curable resin was cured. Next, the fiber on the back surface of the slide glass was cut off, and the birefringent array solidified with an ultraviolet curable resin was peeled from the slide glass. In this way, an ultraviolet curable resin (support medium) having a pair of facing surfaces facing each other and having an isotropic refractive index was produced. Further, in the obtained ultraviolet curable resin, a plurality of birefringent bodies are arranged side by side so that the major axes of the birefringent bodies are oriented in substantially the same direction along a plane substantially parallel to one opposing surface. Arranged.

  Next, a plurality of wedge-shaped grooves are formed on one side of the pair of opposing surfaces of the ultraviolet curable resin in parallel with the minor axis direction of the birefringent array (birefringent body). Got. In the formation of the plurality of wedge-shaped grooves, the groove width was changed within the range of 30 to 85 μm, the groove depth was 8 to 25 μm, the apex angle was 120 ° to 105 °, and the pitch size was 260 to 190 μm.

  Next, in the obtained optical element, one white LED (NACW008: manufactured by Nichia Corporation) was disposed on a surface perpendicular to the major axis direction of the birefringent body. Also, a surface light source element was obtained by installing a reflector on the surface of the optical element where the wedge-shaped groove was formed.

A direct current of 18 mA was applied to the LED of the surface light source element thus obtained to cause the surface light source element to emit light. A color luminance meter (BM-7A: manufactured by Topcon Corporation) was disposed above the light emitting surface of the surface light source element, and an analyzer (polarizing plate) was disposed between the color luminance meter and the surface light source element. The polarizing plate is installed so that the absorption axis of the polarizing plate and the major axis direction of the birefringent body of the optical element are parallel (so that the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel). did. Next, the front luminance at the center of the surface light source element was measured by a color luminance meter, and found to be 120 cd / m ² . Next, the polarizing plate was rotated so that the absorption axis of the polarizing plate and the major axis direction of the birefringent body of the optical element were orthogonal (so that the transmission axis of the polarizing plate and the transmission axis of the optical element were orthogonal). However, the front luminance at the center of the surface light source element was 92.5 cd / m ² . It was confirmed that the surface light source element of Example 1 has a polarization separation function.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 2>
In Example 2, a diffusion plate (haze 94.5%, PDA made by IBM) “WorkPad 8602—on the optical element included in the surface light source element manufactured in Example 1 (on the side opposite to the reflection plate). 30j "). Thus, the surface light source element of Example 2 comprised from three layers of a diffuser plate / optical element / reflector board in the thickness direction was obtained.

A direct current of 18 mA was applied to the LED of the obtained surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel to each other is arranged. When the front luminance in the center portion was measured, it was 131 cd / m ² . In Example 2, it was confirmed that the front luminance of the surface light source element was improved as compared with Example 1.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 3>
In Example 3, a prism sheet (“BEF”, manufactured by 3M, pitch size 50 μm, apex angle 90 °) is placed on the diffusion plate of the surface light source element produced in Example 2 (the side opposite to the optical element). Laminated. In this way, a surface light source element of Example 3 composed of four layers of prism sheet / diffusion plate / optical element / reflection plate in the thickness direction was obtained.

A direct current of 18 mA was applied to the LED of the obtained surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel to each other is arranged. The front luminance at the center was measured and found to be 173 cd / m ² . In Example 3, it was confirmed that the front luminance of the surface light source element was further improved as compared with Examples 1 and 2.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 4>
In Example 4, a brightness enhancement film (“DBEF”: manufactured by 3M) was laminated on the prism sheet (on the side opposite to the diffusion plate) of the surface light source element produced in Example 3. Thus, the surface light source element of Example 5 comprised from five layers of a brightness enhancement film / prism sheet / diffusion plate / optical element / reflection plate in the thickness direction was obtained.

A direct current of 18 mA was applied to the LED of the obtained surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel to each other is arranged. When the front luminance in the center portion was measured, it was 213 cd / m ² . In Example 4, it was confirmed that the front luminance of the surface light source element was further improved as compared with Examples 1, 2, and 3.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 5>
In Example 5, a prism sheet (“BEF”, manufactured by 3M, pitch size 50 μm, apex angle 90 °) is formed on the optical element of the surface light source element manufactured in Example 1 (on the side opposite to the reflecting plate). Laminated. Thus, the surface light source element of Example 5 comprised from three layers of a prism sheet / optical element / reflector in the thickness direction was obtained.

A direct current of 18 mA was applied to the LED of the obtained surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel are arranged. When the front luminance in the center portion was measured, it was 147 cd / m ² . In Example 5, it was confirmed that the front luminance of the surface light source element was further improved as compared with Examples 1 and 2.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 6>
In Example 6, a brightness enhancement film ("DBEF": manufactured by 3M) was laminated on the optical element of the surface light source element produced in Example 1 (on the side opposite to the reflector). Thus, the surface light source element of Example 6 comprised from three layers of a brightness improvement film / optical element / reflector in the thickness direction was obtained.

A direct current of 18 mA was applied to the LED of the obtained surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel are arranged. The front luminance at the center was measured and found to be 167 cd / m ² . In Example 6, it was confirmed that the front luminance of the surface light source element was further improved as compared with Examples 1, 2, and 5.

  Furthermore, the obtained surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, bright and good video information could be visually recognized.

<Example 7>
In Example 7, the surface light source element produced in Example 1 was evaluated by the following method. That is, a direct current of 18 mA is applied to the LED of the surface light source element to cause the surface light source element to emit light, and a color luminance meter (BM-7A: manufactured by Topcon Corporation) is disposed above the light emitting surface. A polarizing plate as an analyzer was disposed between the light source elements. The polarizing plate is installed so that the absorption axis of the polarizing plate and the major axis direction of the birefringent body of the optical element are parallel (so that the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel). did. And the angle distribution of the brightness | luminance in the viewing angle range of -70 degrees-+70 degrees was measured by making the front normal direction of a surface light source element into 0 degree. The result is shown in FIG.

  As shown in FIG. 5, as shown in the obtained angular distribution, in Example 7, light is guided to the front, and the light use efficiency and luminance are higher than those in Comparative Example 2 described later. confirmed.

<Comparative Example 1>
By disposing one white LED (NACW008: manufactured by Nichia Corporation) on the end face of the light guide plate (hazy 94.5%, mounted on “WorkPad 8602-30j” which is a PDA manufactured by IBM) The surface light source element of Comparative Example 1 was obtained.

A direct current of 18 mA was applied to the LED of the surface light source element to cause the surface light source element to emit light. A color luminance meter is disposed above the light emitting surface of the surface light source element, and in the same manner as in Example 1, the surface light source element when the transmission axis of the polarizing plate and the transmission axis of the optical element are parallel to each other is arranged. The front luminance at the center was measured and found to be 99 cd / m ² . In Comparative Example 1, it was confirmed that the front luminance of the surface light source element was lower than that in Example 1.

  Furthermore, this surface light source element was bonded to a liquid crystal cell to produce a liquid crystal display device. In this liquid crystal display device, overall dark image information was obtained as compared with Example 1.

<Comparative example 2>
In Comparative Example 2, the surface light source element produced in Comparative Example 1 was evaluated by the following method. That is, a direct current of 18 mA is applied to the LED of the surface light source element to cause the surface light source element to emit light, and a color luminance meter (BM-7A: manufactured by Topcon Corporation) is disposed above the light emitting surface. Then, the angle distribution of luminance in the viewing angle range of −70 ° to + 70 ° was measured with the front direction of the surface light source element being 0 °. The results are shown in FIG. 5 together with the results of Example 7.

  As shown in FIG. 5, in Comparative Example 2, it was confirmed that the front luminance was lower than that of Example 7 described above, and the luminance was low over the measured viewing angles.

<Comparative Example 3>
In Comparative Example 3, the optical element of Example 1 was cut in a cross section parallel to a pair of facing surfaces, a portion where the support medium contains a birefringent body (hereinafter referred to as a polarization functional layer), and the support medium Were divided into a portion (hereinafter, referred to as a light guide layer) having no single birefringent body and having one surface on which a wedge-shaped groove was formed. Next, a layer made of air (hereinafter referred to as an air layer) was interposed between the polarization functional layer and the light guide layer. A surface light source element of Comparative Example 3 having the same structure as Example 1 was produced except that an air layer was interposed between the polarization functional layer and the light guide layer.

Next, when the front luminance in the center part of the surface light source element of Comparative Example 3 was measured in the same manner as in Example 1, it was 87.6 cd / m ² . In Comparative Example 3, it was confirmed that the front luminance of the surface light source element was lower than that in Example 1.

It is a schematic sectional drawing which shows an example of the conventional surface light source element. It is a schematic sectional drawing of a common liquid crystal display panel. It is a perspective schematic diagram of the optical element which concerns on this embodiment. It is a schematic sectional drawing of the lamination | stacking optical member using the optical element which concerns on this embodiment, and the surface light source element using this lamination | stacking optical member. It is a graph which shows angle distribution of the brightness | luminance of each surface light source element of Example 7 and Comparative Example 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 4 ... Support medium, 5 ... Birefringent body, 6 ... Uneven part, 7, 8 ... Opposite surface, 11 ... Light source, 14 ... Diffusing plate, 15 ... Prism sheet , 16 ... reflector, 17 ... brightness enhancement film, 30 ... optical element, 31 ... surface light source element, 32 ... laminated optical member, P ... wedge-shaped grooves or V-shaped Pitch between mold grooves.

Claims (16)

A support medium having a pair of facing surfaces facing each other and having an isotropic refractive index;
A plurality of birefringent bodies disposed in the support medium,
The birefringent body has an aspect ratio that is a ratio of a length in a major axis direction to a length in a minor axis direction of 2 or more, and a refractive index difference between the major axis direction and the minor axis direction is 0.05 or more. Is a pillar body,
The plurality of birefringent bodies are arranged side by side along a plane substantially parallel to one of the opposing surfaces so that the major axes of the birefringent bodies are oriented in substantially the same direction.
The difference between the refractive index of the support medium and the refractive index of either the short axis direction or the long axis direction of the birefringent body is 0.03 or less,
An optical element in which a concavo-convex portion is formed on one surface of the pair of opposed surfaces.   2. The optical element according to claim 1, wherein the birefringent body is substantially polygonal or circular in cross-sectional shape perpendicular to the major axis direction.   The optical element according to claim 1, wherein the birefringent body has a substantially triangular shape in cross section perpendicular to the major axis direction.   The optical element according to claim 3, wherein the birefringent body has a substantially equilateral triangle shape in cross section perpendicular to the major axis direction.   The optical element according to claim 1, wherein the birefringent body is a fiber.   The optical element according to any one of claims 1 to 5, wherein a difference between a refractive index of the support medium and a refractive index in one of a short axis direction and a long axis direction of the birefringent body is 0.01 or less.   The said uneven | corrugated | grooved part is a wedge-shaped groove | channel or a V-shaped groove | channel, and the said wedge-shaped groove | channel or V-shaped groove | channel is formed in multiple numbers substantially parallel to the short-axis direction of the said birefringent body. An optical element according to 1.   The optical element according to claim 7, wherein a pitch between the plurality of wedge-shaped grooves or V-shaped grooves is 10 μm or more.   A laminated optical member formed by laminating the optical element according to claim 1 and an optical layer exhibiting another optical function.   The laminated optical member according to claim 9, wherein the optical layer is a diffusion plate.   The laminated optical member according to claim 9, wherein the optical layer is a prism sheet.   The laminated optical member according to claim 9, wherein the optical layer is a brightness enhancement film.   The laminated optical member according to claim 9, wherein a diffusion plate is laminated on the optical element, and a prism sheet is laminated on the diffusion plate.   The laminated optical member according to claim 9, wherein a diffusion plate is laminated on the optical element, a prism sheet is laminated on the diffusion plate, and a brightness enhancement film is laminated on the prism sheet. The optical element according to any one of claims 1 to 8, or the laminated optical member according to any one of claims 9 to 14, and
A light source disposed on a surface perpendicular to the one surface of the support medium on which the uneven portion is formed in the optical element or the laminated optical member;
A surface light source element comprising: a reflecting plate disposed on the one surface side of the support medium on which the uneven portion is formed in the optical element or the laminated optical member. The optical element according to any one of claims 1 to 8, the laminated optical member according to any one of claims 9 to 14, or the surface light source element according to claim 15.
And a liquid crystal cell.

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