JPWO2008038754A1 - Surface light source and liquid crystal display device using the same - Google Patents

Abstract

Provided are a sidelight type surface light source having excellent light utilization efficiency, high brightness and wide viewing angle, and a liquid crystal display device using the same. The surface light source of the present invention includes a light source, a light guide having at least one light incident surface facing the light source, and a light emitting surface substantially orthogonal thereto, and a first light source disposed opposite the light emitting surface. A light source having a plurality of linear grooves or projections substantially parallel to the light emitting surface or a light non-emitting surface on the back surface of the light emitting surface. The first optical film has anisotropic diffusivity, and a direction in which the anisotropic diffusibility is maximum is substantially parallel to a longitudinal direction of the linear groove or linear protrusion. Is arranged.

Description

  The present invention relates to a surface light source for irradiating a liquid crystal display element or the like from the back surface, and a liquid crystal display device equipped with the surface light source.

  Many displays using liquid crystals are used as display devices for personal computers, televisions, mobile phones, and the like. These liquid crystal display elements themselves are not light emitters. For this reason, display is performed by irradiating the liquid crystal display element with light using a surface light source from the back side.

  As the surface light source, there are a direct type in which a plurality of light sources are arranged directly under a liquid crystal display element, and an edge light type in which a light source is arranged so as to face a side end face of a light guide. The direct type is mainly used for TV, and the edge light type is more compact than the direct type in addition to car navigation systems, monitors, and small TVs. It can be used for mobile phones, laptop computers, digital cameras, digital video, etc. Widely used in mobile media and digital home appliance display panels.

  In recent years, with the advancement of microfabrication technology, the fine pitch of pixels has progressed, and higher-definition image display has become possible. However, when the pixels are made finer, the transmittance of the liquid crystal display element is lowered. For this reason, in order to display a high-definition image clearly, a surface light source with higher luminance is required.

  In mobile media applications, they are often used outdoors. In that case, it is used by being driven by a battery. However, of the power consumed at that time, a great amount of power is consumed for the light emission of the surface light source. For this reason, in order to extend the drive time of a mobile medium, the low power consumption of a surface light source is calculated | required. However, simply turning off the power decreases the brightness of the surface light source, and a clear image cannot be obtained outdoors. For this reason, a surface light source with low power consumption and high luminance is required.

  Further, when a liquid crystal display device is used for a monitor or the like, it is required to reduce the number of film members or to replace an expensive prism sheet with a diffusion sheet in order to reduce the cost. For this reason, high efficiency is also required for the surface light source.

  Thus, when an edge light type surface light source is used, there is a strong demand for higher efficiency, higher brightness, and lower cost of the surface light source. A conventional surface light source uses a light diffusive ink dot printing light guide (see, for example, Patent Document 1). However, such a surface light source cannot satisfy these requirements. For this reason, various new sidelight type surface light sources have been developed (see, for example, Patent Documents 2 to 5).

  In Patent Document 2, a surface light source using a light guide in which a plurality of light diffusion patterns arranged in a substantially concentric manner around a light incident surface is formed on a surface opposite to a light emitting surface of the light guide. Is disclosed.

  In Patent Document 3, arc-shaped grooves or protrusions are formed on the surface opposite to the light exit surface at intervals from the light incident surface side, and anisotropy changes concentrically on the exit surface side. A surface light source is disclosed in which a prism sheet in which prisms are arranged concentrically around a light incident surface side on a light guide body on which a hologram pattern is formed is combined with the prism surface facing the light incident surface side of the light guide body. Has been.

  Patent Document 4 discloses a surface light source using a combination of a light guide and a diffusion sheet in which triangular prisms are arranged in a direction perpendicular to the light incident surface on the light exit surface of the light guide.

In Patent Document 5, a prism is formed perpendicular to the prism array of the light guide in a light guide having a prism row formed perpendicular to the light incident surface on the surface opposite to the light exit surface of the light guide. A combination of a prism sheet with a prism surface facing the light incident surface side of the light guide is disclosed.
JP-A-1-107406 (all pages) Japanese Patent No. 3135830 (all pages) JP 2004-111383 A (all pages) JP-A-8-179322 (all pages) JP 11-224516 A (all pages)

  However, in the surface light sources described in Patent Documents 2 and 3, the diffusion pattern elements or the deflection pattern elements are arranged in a substantially concentric or concentric pattern. For this reason, there is a problem that it is difficult to increase the area of the surface light source. In addition, it is difficult to control the viewing angle of the screen from the structural features of the pattern.

  Moreover, in the surface light source described in Patent Document 4, triangular prisms are arranged in a direction in which the cross section is parallel to the lamp. For this reason, there is a problem that sufficient luminance characteristics cannot be obtained.

  In addition, the surface light source described in Patent Document 5 has excellent luminance characteristics by combining a prism array on the light exit surface of the light guide or the back surface thereof and a prism sheet on which prisms perpendicular to the prism array are formed. A surface light source is obtained. However, the viewing angle is about ± 10 °, and the viewing angle characteristics are very poor. In addition, the luminance uniformity is low.

  An object of the present invention is to provide a sidelight type surface light source having excellent light utilization efficiency, high luminance and wide viewing angle, and a liquid crystal display device using the same, in view of the background of the prior art.

  As a result of earnestly examining the above problems, the inventors of the present invention have tried to construct a light source having a specific structure and a film having anisotropic diffusivity in a surface light source. The present inventors have found that a surface light source excellent in efficiency, viewing angle characteristics, and luminance uniformity can be provided, and the present invention has been completed. That is, the present invention is as follows.

  (1) A surface light source according to the present invention is disposed to face a light source, a light guide having at least one light incident surface facing the light source, and a light emitting surface substantially orthogonal thereto, and the light emitting surface. A light source having a plurality of linear grooves or protrusions on the light emitting surface or a light non-emitting surface on the back surface of the light emitting surface. The first optical film has anisotropic diffusibility, and the direction in which the anisotropic diffusibility is maximum is substantially parallel to the longitudinal direction of the linear groove or linear protrusion. It is a surface light source arrange | positioned so that it may become.

The surface light source of the present invention more preferably has any one of the following configurations (2) to (15).
(2) The linear groove or the linear protrusion is at least one selected from the group consisting of a substantially arc shape, a substantially bell shape, a substantially triangular shape, and a substantially trapezoidal shape in cross section perpendicular to the longitudinal direction thereof. The surface light source according to (1) above.
(3) The surface light source according to (1) or (2), wherein the linear groove or the linear protrusion has a longitudinal direction substantially parallel to a light incident surface of the light guide.
(4) The surface light source according to any one of (1) to (3), wherein the linear groove or the linear protrusion is provided on a light non-emitting surface of the light guide.
(5) The surface light source according to any one of (1) to (4), wherein a second optical film is installed on the first optical film.
(6) The first optical film has a half-value width D1max of transmitted light in a direction in which the diffusivity is maximum when light is incident on the first optical film from the normal direction, and the diffusivity is minimum. The surface light source according to any one of the above (1) to (5), wherein a ratio D1max / D1min to a half-value width D1min of transmitted light in the direction is as follows.
(7) The surface light source according to any one of (1) to (6), wherein the first optical film has a transmittance of 45% or more and a haze of 70% or more.
(8) The surface light source according to (6) or (7), wherein the first optical film has the half width D1min of 10 ° or less.
(9) The surface light source according to any one of (5) to (8), wherein the second optical film is a prism sheet having an apex angle of 80 ° to 100 °.
(10) The prism sheet has a length (light guide) direction substantially parallel to a direction in which diffusivity is maximized when light is incident on the first optical film from a normal direction. The surface light source according to (9), which is disposed on the surface.
(11) The angle formed between the slope located on the light source side in the linear groove provided in the light guide and the straight line perpendicular to the light source 1, or the opposite of the light source in the linear protrusion provided in the light guide The surface light source according to (9) or (10), wherein an angle formed by a slope positioned on a side and a straight line perpendicular to the light source 1 is 42.5 ° to 50 °.
(12) The second optical film has a half-value width D2max of transmitted light in a direction in which the diffusibility is maximum when light is incident on the second optical film from the normal direction, and the diffusivity is minimum. The surface light source according to any one of (5) to (8), wherein a ratio D2max / D2min to a half-value width D2min of transmitted light in the direction becomes.
(13) The surface light source according to (12), wherein the second optical film has a transmittance of 50% or more and a haze of 70% or more.
(14) The surface light source according to (12) or (13), wherein the second optical film has the half width D2min of 2 ° to 50 °.
(15) The angle formed between the slope located on the light source side in the linear groove provided in the light guide and the straight line perpendicular to the light source 1, or the opposite of the light source in the linear protrusion provided in the light guide The surface light source according to any one of (12) to (14), wherein an angle formed between a slope positioned on a side and a straight line perpendicular to the light source 1 is 20 ° to 42.5 °.

  The liquid crystal display device of the present invention is equipped with the surface light source of the present invention.

  In the present invention, a light guide body in which a plurality of linear grooves or linear protrusions are provided substantially in parallel is used. Thereby, the emission characteristics can be controlled by controlling the structure of the plurality of linear grooves or linear protrusions. As a result, a surface light source having high luminance and high luminance uniformity can be obtained.

  Further, in the present invention, the longitudinal direction of the linear grooves or linear protrusions and the direction in which the anisotropic diffusivity of the first optical film having anisotropic diffusivity is maximized are arranged substantially in parallel. . Thereby, light can be used efficiently. As a result, a high-luminance surface light source can be obtained.

FIG. 1 is an example of an exploded perspective view showing the relative positional relationship of each member constituting the surface light source of the present invention. FIG. 2 is a diagram illustrating an example in which light sources are arranged on two or more side end surfaces of the light guide 3. FIG. 3 illustrates a preferred arrangement mode of the linear grooves 33 or the linear protrusions 34 when the light guide 3 in the surface light source of the present invention is observed from the light emitting surface 32 side. FIG. 4 illustrates a preferred arrangement mode of the linear grooves 33 or the linear protrusions 34 when the light guide 3 in the surface light source of the present invention is viewed from the light emitting surface 32 side. FIG. 5 is a diagram for explaining linear grooves or linear protrusions that are substantially parallel in the surface light source of the present invention. FIG. 6 illustrates a cross-sectional view perpendicular to the length direction of the linear groove 33 formed in the light guide 3 in the surface light source of the present invention. FIG. 7 illustrates a cross-sectional view perpendicular to the length direction of the linear protrusions 34 formed on the light guide 3 in the surface light source of the present invention. FIG. 8 is a diagram for explaining the definition of the half width. FIG. 9 is a diagram for explaining an angle formed by the longitudinal direction of the linear groove 33 or the linear protrusion 34 and the direction in which the anisotropic diffusion property of the first optical film 5 is maximized. FIG. 10 is a perspective view showing a preferred form of the first optical film in the surface light source of the present invention. FIG. 11 is a perspective view showing a preferred form when the second optical film in the surface light source of the present invention is a prism sheet. FIG. 12 is a diagram for explaining an angle formed by the length direction of the prism and the direction in which the anisotropic diffusion property of the first optical film 5 is maximized. FIG. 13 is a perspective view showing a preferred form when the second optical film in the surface light source of the present invention is an isotropic diffusion sheet. FIG. 14 is a schematic diagram for explaining the light transmission characteristics of the prism sheet. FIG. 15 is a diagram schematically illustrating the light that propagates through the light guide and exits. FIG. 16 is an example showing an emission angle distribution from the central portion of the light exit surface 32 of the light guide 3 when the surface light source of the present invention is in the form of FIG. FIG. 17 shows an example of the emission angle distribution from the central portion of the surface light source when the second optical film is installed on the light guide 3 when the surface light source of the present invention is in the form of FIG. It is. FIG. 18 is a schematic diagram showing measurement points of the luminance of the surface light source in Examples and Comparative Examples. FIG. 19 is a perspective view schematically showing the form of the first optical film produced in Examples and Comparative Examples. FIG. 20 is a perspective view schematically showing the form of the first optical film produced in Examples and Comparative Examples. FIG. 21 is a perspective view schematically showing the form of the first optical film produced in Examples and Comparative Examples.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Reflector 3 Light guide 4 Reflective sheet 5 1st optical film 6 2nd optical film 31 The light-incidence surface of the light guide 3 32 The light emission surface of the light guide 3 33 Linear groove 34 Linear protrusion 35 Light non-emission surface 101 of light guide 3 Brightness measurement point H1 Depth of linear groove 33 H2 Height of linear protrusion 34 θ1 A slope of linear groove 33 on the light source 1 side and a straight line perpendicular to the light source are formed. Angle θ2 Angle formed by the slope of the linear protrusion 34 facing the light source 1 and a straight line perpendicular to the light source θ3 The apex angle of the prism sheet θ4 The longitudinal extension of the adjacent linear groove 33 or linear protrusion 34 Angle θ5 Angle formed by the longitudinal direction (d1) of the linear groove 33 or the linear protrusion 34 and the direction (d2) in which the anisotropic diffusion property of the first optical film 5 is maximized. Θ6 Length direction of the prism (d3) ) And the maximum anisotropic diffusion of the first optical film 5 Angle formed by (d2) θi Incident angle θo Output angle d1 Longitudinal direction of linear groove 33 or linear protrusion 34 d2 Direction in which anisotropic diffusivity is maximized d3 Length direction of prism λi1 From normal direction to prism sheet Incident light λi2 Optimal incident light for the prism sheet λi3 Light incident on the prism sheet at a large incident angle λp1 Light that collides with the linear groove 33 or the linear protrusion 34 substantially parallel to the surface of the light guide 3 λp2 Linear groove 33 Alternatively, light that collides with the linear protrusion 34 from the light emitting surface 32 side of the light guide 3 λp3 Light that collides with the linear groove 33 or the linear protrusion 34 from the surface opposite to the light emitting surface 32 of the light guide 3 λo1 Light that collides with the linear groove 33 or the linear protrusion 34 substantially in parallel with the surface of the light guide 3 and is emitted to the outside of the light guide 3 .lambda.o2 Light emission surface of the light guide 3 with respect to the linear groove 33 or the linear protrusion 34 Light that collides from the side 32 and exits from the light guide 3 Light colliding with the linear groove 33 or the linear protrusion 34 from the surface opposite to the light emitting surface 32 of the light guide 3 and emitted to the outside of the light guide 3 FL1 Thickness of the first optical film FL2 Second optical Film thickness

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is an example of an exploded perspective view showing a relative positional relationship between members constituting the surface light source of the present invention.

  As shown in FIG. 1, the surface light source of the present invention includes a light source 1, a reflector 2, a light guide 3, a reflection sheet 4, a first optical film 5, and a second optical film 6. Have. In the example of FIG. 1, the second optical film 7 is also a component of the surface light source. However, the second optical film 7 may not exist.

[light source]
In the surface light source of the present invention, the light source 1 is a linear light source extending in the y direction of FIG. As the light source 1, for example, a fluorescent tube or a cold cathode tube can be used. Further, as the light source 1, one or a plurality of light emitting diodes (LEDs) arranged in parallel in the y direction of FIG.

  In the example of FIG. 1, an example in which the light source 1 is arranged on one side end surface of the light guide 3, that is, an example in which the number of the light sources 1 is one is shown. The number of light sources 1 to be arranged is not limited to one. FIG. 2 is a diagram illustrating an example in which light sources are arranged on two or more side end surfaces of the light guide 3. As shown in FIG. 2A, two light sources 1 and reflectors 2 are provided on opposite side end faces of the light guide 3 (two light incident surfaces 31), FIGS. 2B and 2C. As shown in FIG. 2, the light source 1 and the reflector 2 are provided on adjacent side end surfaces of the light guide 3 (two light incident surfaces 31 (FIG. 2 (c)) and three (FIG. 2 (b)). ) Is also suitably used as the surface light source of the present invention.

[Reflector]
The reflector 2 is disposed around the light source 1 and effectively makes the light from the light source 1 incident on the light guide. As a characteristic requested | required of the reflector 2, a thing with a high reflectance is preferable, and, specifically, it is preferable that a total light reflectance is 85% or more. More preferably, it is 87% or more, and particularly preferably 90% or more. If the total light reflectance of the reflector 2 is less than 85%, the light emitted from the light source 1 cannot be sufficiently reflected, and the screen luminance may be extremely inferior. In the surface light source of the present invention, a high-luminance surface light source can be obtained by setting the total light reflectance of the reflector 2 to 85% or more.

  As the material of the reflector 2, 1) a resin is used as a main component, and organic and inorganic dyes and fine particles are added to the resin. 2) a resin that is incompatible with the resin component, or organic, One or more materials selected from inorganic particles are mixed and melt extruded, and then stretched in at least one direction to form fine bubbles inside. 3) A gas such as carbon dioxide gas is injected into the molten resin. Extruded, having air bubbles inside, 4) Stacked a plurality of resin layers having different refractive indexes, 6) Deposited metal on at least one side of reflection sheets of 1) to 4), and these Combinations are exemplified, and any of them can be suitably used. Among these, in the surface light source of the present invention, those having apparent whiteness are more preferably used, and 2) is particularly preferably used. Furthermore, a thermoplastic resin to which organic or inorganic fine particles are added is laminated on at least one surface of a film in which fine bubbles are formed inside by a method such as coextrusion, and further stretched, and the surface layer portion is finer than the inner layer portion. A composite film in which bubbles are formed can be particularly preferably used.

  The reflector 2 preferably contains a material imparting resistance to light, that is, a light stabilizer, in order to stably exhibit reflection characteristics over a long period of time. More preferably, the outermost surface layer preferably contains a light stabilizer. Here, the outermost surface layer indicates a layer located on the most surface side when the reflector 2 has a laminated structure, and indicates the layer in the case of a single layer structure. In the case of a laminated structure, there are two outermost surface layers, but it is more preferable that at least the outermost surface layer on the light guide 3 side contains a light stabilizer.

  The material which comprises the reflector 2 can be combined and used according to a use. For example, in order to prevent light leakage to the back of the reflector 2, a metal is vapor-deposited on the back surface, or it is bonded to a colored film such as black or a metal foil.

  Moreover, in the surface light source of this invention, it is also one of the preferable aspects that a light shielding layer, a heat-transfer layer, and a conductive layer are formed on the back surface side of the material which comprises the reflector 2 by printing or vapor deposition.

[Light guide]
The light guide 3 has four side end surfaces. At least one side end surface is a light incident surface 31. The light source 1 faces the light incident surface 31 and is provided substantially parallel to the light incident surface 31. That is, the light guide 3 has two opposing side end surfaces that are substantially parallel to the xz plane and a terminal surface that is a side end surface facing the light incident surface 31. The light guide 3 has two main surfaces. The two main surfaces face each other and are substantially orthogonal to the light incident surface 31. One of the two main surfaces is a light exit surface 32. A surface opposite to the light emitting surface 32 is a light non-emitting surface 35. In the example of FIG. 1, the light exit surface 32 is disposed substantially parallel to the xy plane, and the projection onto the xy plane is substantially rectangular. Further, the projection of the light guide 3 onto the xz plane may have a substantially wedge shape, in addition to a substantially rectangular shape, and a substantially wedge shape in which the film thickness decreases as the distance from the light source 1 increases.

  Light emitted from the light source 1 enters the light guide 3 from the light incident surface 31 of the light guide 3, propagates through the light guide 3, and is emitted from the light exit surface 32.

  In the surface light source of the present invention, the light guide 3 includes an acrylic resin such as methyl methacrylate resin (PMMA), a polycarbonate resin, a polyolefin resin such as polypropylene, polyisobutylene, polybutene, and polymethylpentene, and a cycloolefin resin. It is comprised from the transparent resin material which has fixed refractive indexes, such as.

  In the surface light source of the present invention, a plurality of linear grooves or linear protrusions are provided substantially in parallel on the light non-emitting surface 5 on the back surface of the light emitting surface 32 or the light emitting surface 35. In the example of FIG. 1, a plurality of linear grooves 33 are provided substantially in parallel. A linear protrusion may be provided instead of the linear groove 33. Moreover, the linear groove | channel and the linear protrusion may be mixed. The linear groove or the linear protrusion may be provided on either the light emitting surface 32 or the non-light emitting surface 35, or may be provided on both surfaces.

  There is no particular limitation on the arrangement pattern of the plurality of linear grooves or linear protrusions. 3 shows the arrangement of the linear grooves 33 or the linear protrusions 34 when the light guide 3 in the surface light source of the present invention is observed from the light emitting surface 32 side in the normal direction (z direction in FIG. 1). It is a schematic diagram which shows. As shown in FIG. 3, as the arrangement direction of the linear grooves 33 or the linear protrusions 34 of the light guide 3, the arrangement direction of the linear grooves 33 or the linear protrusions 34 is substantially perpendicular to the light incident surface 31 ( 3 (a)), substantially parallel (FIG. 3 (b)), intermediate (FIG. 3 (c)), and combinations thereof (for example, FIGS. 3 (d) to (i)). Etc. Preferably, a linear groove 33 or a linear protrusion 34 that is substantially parallel to the light incident surface 31 is preferably formed from the viewpoint that particularly high light utilization efficiency can be obtained. More preferably, the linear grooves 33 or the linear protrusions 34 in a direction substantially parallel to the light incident surface 31 are formed denser than the linear grooves 33 or the linear protrusions 34 in other directions. Moreover, this arrangement | sequence does not need to be uniformly formed in the whole surface of the light guide 3, and may be formed partially. Further, different arrangements may be mixed in the same plane, or arrangements that are not in parallel relation may be mixed.

  Moreover, in FIG. 3, although the linear groove | channel 33 or the linear protrusion 34 showed the example continuously formed from one side surface of the light guide 3 to another side surface, it is not necessarily a continuous straight line. As long as the effect of the present invention is not lost, it is bent as shown in FIG. 4, is curved, or is partially disconnected (not shown) and is adjacent to each other. The linear groove 33 or the linear protrusion 34 may be partially out of parallel relation (not shown).

  In the present invention, at least some of the linear grooves or linear projections are provided substantially in parallel. Here, “substantially parallel” means that the angles θ41 and θ42 (hereinafter referred to as θ4) formed by the extension lines in the longitudinal direction of adjacent linear grooves 33 or linear protrusions 34 are 0 ± as shown in FIG. It means within 15 °. In addition, 0 degree means that the extension line of the longitudinal direction of the adjacent linear groove | channel 33 or the linear protrusion 34 does not cross, ie, it is parallel. More preferably, θ4 is within 0 ± 10 °, and further preferably θ4 is within 0 ± 5 °. As shown in FIG. 4, when adjacent linear grooves 33 or linear protrusions 34 are bent or curved as described later, the main direction in the longitudinal direction forms an angle, Let θ4. Further, it is not necessary that all the grooves or protrusions of the plurality of linear grooves 33 or the linear protrusions 34 are formed in parallel, and grooves or protrusions that are not in a parallel relationship may be included.

  The light that has entered the light guide 3 repeats total reflection at the interface between the light guide 3 and the air while entering the light emitting surface 32 and the light non-emitting surface 35 at a critical angle or more. And is not emitted outside the light guide 3. Here, of the light propagating through the light guide 3, the light that collides with the linear grooves 33 or the linear protrusions 34 formed in the light guide 3 is guided by the linear grooves 33 or the linear protrusions 34. The direction of travel is changed by reflection at the body 3 / air interface. As a result, the light is incident on the light emitting surface 32 at a critical angle or less and is emitted to the outside of the light guide 3. That is, in the surface light source of the present invention, in-plane emission characteristics can be controlled by appropriately controlling the shape and arrangement of the linear grooves 33 or the linear protrusions 34 formed in the light guide 3. As a result, a surface light source having high luminance and high luminance uniformity in the surface can be obtained.

  As described above, in the present invention, the linear groove or the linear protrusion may be provided on either the light emitting surface 32 or the light non-emitting surface 35, or may be provided on both surfaces. It is preferable that the linear groove or the linear protrusion is provided on the light non-emitting surface 35 because particularly high light utilization efficiency is obtained and the control of the emission angle distribution is easy. In this case, the light emitting surface 32 of the light guide 3 may be smooth or may be formed with various patterns. When the pattern is formed more than necessary on the light emitting surface 32, the light is propagated to the end surface facing the light incident surface 31 away from the light source 1 (up to the central part when the light source 1 is installed on both sides), before the light propagates. A lot of light is emitted from the light emitting surface 32. For this reason, the in-plane uniformity of luminance may be reduced, or the central luminance may be reduced. Further, it may be difficult to increase the area of the light guide 3. Therefore, when the linear groove or the linear protrusion is provided on the light non-emission surface 35, the light emission surface 32 of the light guide 3 is preferably smooth.

  Here, being smooth means that the surface roughness Ra based on JIS-B0601 (2001 edition) is 50 nm or less. The surface roughness Ra is more preferably 30 nm or less, further preferably 20 nm or less, and most preferably 10 nm or less. In the surface light source of the present invention, by setting the Ra of the light emitting surface 32 of the light guide 3 to 50 nm or less, a surface light source having excellent luminance characteristics can be formed even in a large area.

  FIGS. 6 and 7 are views illustrating a cross-sectional view perpendicular to the length direction of the linear groove 33 or the linear protrusion 34 formed in the light guide 3 in the surface light source of the present invention (x in FIG. 1). -Z plane). 6 shows a cross-sectional view of the linear groove 33, and FIG.

  As shown in FIG. 6, as a preferable shape of the linear groove 33 of the light guide 3, a substantially triangular shape (FIG. 6A), a substantially trapezoidal shape (FIG. 6B), and a substantially arc shape (FIG. 6). (C)), substantially bell-shaped (FIG. 6 (d)), those in which they are deformed (FIG. 6 (e)), and those in which these are mixed. Moreover, the shape similar to these shapes may be sufficient.

  As shown in FIG. 7, as a preferable shape of the linear protrusion 34, a substantially triangular shape (FIG. 7A), a substantially trapezoidal shape (FIG. 7B), a substantially arc shape (FIG. 7C), Examples include a substantially bell shape (FIG. 7D), a deformed shape thereof (FIG. 7E), and a mixture thereof. Moreover, the shape similar to these shapes may be sufficient.

  6 and 7, the cross-sectional shape of the linear groove 33 or the linear protrusion 34 is symmetric. However, the cross-sectional shape is not limited thereto, and the light incident surface 31 side and the opposite side are asymmetric. There may be. Moreover, the linear groove | channel 33 and the linear protrusion 34 may be mixed.

  The angle θ1 formed by the slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 and the straight line perpendicular to the light source 1 or the light source in the linear protrusion 34 provided in the light guide 3 It is preferable that an angle θ2 formed by a slope located on the opposite side of 1 and a straight line perpendicular to the light source 1 is 20 to 50 °. If θ1 or θ2 is within the above range, a surface light source with high light utilization efficiency can be obtained.

  The angle formed between the inclined surface located on the light source 1 side in the linear groove 33 provided in the light guide 3 and the straight line perpendicular to the light source 1 is xy as shown in FIGS. 6 (a) and 6 (b). It is an angle θ1 formed by a straight line L1 parallel to the surface and perpendicular to the light source 1 and a slope located on the light source 1 side of the linear groove 33. 6C to 6E, when the angle formed by the slope changes within one slope, the average value of the slope of the tangent of the slope is a line provided on the light guide 3. The angle θ <b> 1 formed by the slope located on the light source 1 side in the groove 33 and the straight line perpendicular to the light source 1 is defined.

  In addition, the angle formed by the slope located on the opposite side of the light source 1 in the linear protrusion 34 provided on the light guide 3 and the straight line perpendicular to the light source 1 is as shown in FIGS. Is an angle θ2 formed by a straight line L1 parallel to the xy plane and perpendicular to the light source 1 and a slope located on the opposite side of the light source 1 of the linear protrusion 34. 7C to 7E, when the angle formed by the inclined surface changes within one inclined surface, the average value of the tangential inclination of the inclined surface is determined on the side opposite to the light source 1 of the linear protrusion 34. An angle θ2 formed by a slope located at a straight line and a straight line perpendicular to the light source 1 is set.

  Thus, the angle θ1 formed by the slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 and the straight line perpendicular to the light source 1, or the linear protrusion provided in the light guide 3 The light emission characteristics from the light guide 3 can be controlled by controlling the angle θ2 formed between the slope located on the opposite side of the light source 1 in 34 and the straight line perpendicular to the light source 1. If θ1 or θ2 is less than 20 ° or exceeds 50 °, the amount of light emitted from the light guide 3 may decrease. Further, when a plurality of light sources are used, θ1 or θ2 may be the above value between at least one light source and the linear grooves 33 or the linear protrusions 34.

  The slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 or the slope located on the opposite side of the light source 1 in the linear protrusion 34 provided in the light guide 3 is smooth. Is preferred. The term “smooth” as used herein means that when the surface roughness Ra of the slope is measured based on JIS-B0601 (2001 edition), the value is 50 nm or less. More preferably, it is 20 nm or less, More preferably, it is 10 nm or less, Most preferably, it is 5 nm or less. When the surface roughness Ra of the inclined surface of the light guide 3 facing the light source 1 of the linear groove 33 or the linear protrusion 34 exceeds 50 nm, the light reflection efficiency on the surface of the linear groove 33 or the linear protrusion 34 decreases. As a result, the light utilization efficiency of the light guide 3 may decrease. The surface roughness Ra of the slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 or the slope located on the opposite side of the light source 1 in the linear protrusion 34 provided in the light guide 3 is defined. By setting the thickness to 50 nm or less, the light reflection efficiency on the surface of the linear groove 33 or the linear protrusion 34 can be increased. As a result, a surface light source with high light utilization efficiency can be obtained.

  The flat surface between the linear grooves 33 or the linear protrusions 34 preferably has a surface roughness Ra based on JIS-B0601 (2001 edition) of 50 nm or less. More preferably, it is 20 nm or less, More preferably, it is 10 nm or less, Most preferably, it is 5 nm or less. In the present invention, when Ra of the flat surface between the linear grooves 33 or the linear protrusions 34 exceeds 50 nm, up to the end surface facing the light incident surface 31 away from the light source 1 (when the light source 1 is installed on both sides) A large amount of light is emitted from the light emitting surface 32 before the light propagates. For this reason, the in-plane uniformity of the brightness may be reduced, or the center brightness may be lowered. By setting the flat surface Ra between the linear grooves 33 or the linear protrusions 34 to 50 nm or less, a surface light source having excellent luminance characteristics can be formed even in a large area.

  In the surface light source of the present invention, the depth H1 (FIG. 6) of the linear groove 33 of the light guide 3 or the height H2 (FIG. 7) of the linear protrusion 34 is preferably 1 to 500 μm. More preferably, it is 1-200 micrometers, More preferably, it is 1-100 micrometers. If H1 and H2 are less than 1 μm, the size of the linear groove 33 or the linear protrusion 34 is too small and molding is difficult, and even if it can be molded, the direction of light propagating in the light guide 3 The function to change the value may be inferior. Moreover, even if H1 and H2 exceed 500 μm, molding tends to be difficult. By making the depth H1 of the linear groove 33 of the light guide 3 or the height H2 of the linear protrusion 34 within the range of 1 to 500 μm, both the moldability of the light guide 3 and the light utilization efficiency are achieved. be able to.

  Of the light that enters and propagates in the light guide 3, the light that collides with the linear grooves 33 or the linear protrusions 34 changes its traveling direction and enters the light exit surface 32 at an angle that is less than the critical angle. The light is emitted out of the light guide 3. For this reason, as the distance from the light source 1 increases, the amount of light propagating in the light guide 3 decreases. That is, the probability of light collision by location is the same. Therefore, if only the linear grooves 33 or the linear protrusions 34 having the same shape and the same size are formed, the side closer to the light source 1 becomes high luminance in proportion to the amount of light in the light guide 3. In order to make the luminance on the side away from the light source 1 equal to the luminance on the light source 1 side, the probability of collision of light with the linear grooves 33 or the linear protrusions 34 should be increased according to the distance from the light source 1. Specifically, according to the distance from the light source 1, (A) the depth H1 of the linear groove 33 or the height H2 of the linear protrusion 34 shown in FIGS. (C) The depth H1 of the linear groove 33 or the height H2 of the linear protrusion 34 shown in FIGS. 6 and 7 is increased, and the linear groove 33 or the linear protrusion 34 is increased. For example, the pitch may be made finer.

  When the depth H1 of the linear groove 33 is increased or the height H2 of the linear protrusion 34 is increased according to the distance from the light source 1 by the method (A) or (C), the linear groove What is necessary is just to change the depth H1 of 33, or the height H2 of the linear protrusion 34 within the range of 1-500 micrometers.

  Further, the depth H1 of each linear groove 33 or the height H2 of the linear protrusion 34 of the light guide 3 is a uniform depth H1 or height H2 in the length direction of one linear groove or linear protrusion. The depth H1 or the height H2 may be changed. As an example in which the depth H1 or the height H2 changes, when there is a portion in which light from the light source 1 is difficult to reach in the direction parallel to the light source 1, the depth H1 or linear shape of the linear groove 33 at that portion When the height H2 of the protrusion 34 is increased or there is a portion where light is excessively propagated, the depth H1 of the linear groove 33 or the height H2 of the linear protrusion 34 can be decreased. As a result, the amount of emitted light in the plane of the light body 3 can be adjusted, so that a desired luminance distribution can be obtained.

  The pitch P, which is a repeating unit of the linear grooves 33 or the linear protrusions 34 of the light guide 3, is preferably 10 to 1000 μm. More preferably, it is 20-600 micrometers, More preferably, it is 30-400 micrometers. If the pitch P is less than 10 μm, it is too small and molding tends to be difficult. On the other hand, when the pitch P exceeds 1000 μm, the luminance uniformity in the portion where the linear groove 33 or the linear protrusion 34 is formed and the portion where the linear protrusion 34 is not formed may be lowered. In the surface light source of the present invention, by making the pitch P of the linear grooves 33 or the linear protrusions 34 of the light guide 3 within a range of 10 to 1000 μm, both the moldability of the light guide 3 and the light utilization efficiency are achieved. can do. Even when the pitch P of the linear groove 33 or the linear protrusion 34 is changed according to the distance from the light source by the method (B) or (C) described above, it is changed within the range of 10 to 1000 μm. Is preferred.

  The shape of the light incident surface 31 of the light guide 3 is not particularly limited as long as the light source 1 is a linear light source such as a fluorescent tube or a cold cathode tube. On the other hand, in the case of using a light source 1 in which one or a plurality of light emitting diodes (LEDs) are arranged in parallel in the y direction to form a pseudo linear light source, a portion corresponding to the front of the LED becomes a bright line. Or a portion corresponding to the front surface between the LED and the LED may be a dark line. In this case, the shape of the light incident surface 31 may be an uneven shape such as a substantially arc shape, a substantially prism shape, a substantially trapezoidal shape, or a substantially dome shape. By adopting such a shape, not only the light incident efficiency into the light guide 3 can be increased, but also light can be diffused appropriately when light is incident. As a result, the luminance can be made uniform even in the vicinity of the light incident surface 31 of the light guide 3.

  In the surface light source of the present invention, the thickness of the light guide 3 depends on the screen size. Usually, it is 0.1 mm-20 mm, More preferably, it is 0.1 mm-15 mm, More preferably, it is 0.1 mm-10 mm. The thickness of the light guide 3 does not need to be constant, and may decrease as the distance from the light incident surface 31 increases. Further, when the thickness of the light guide 3 is thinner than the thickness of the light source 1, in order to improve the light utilization efficiency, the thickness near the light incident surface 31 of the light guide 3 is increased and the inclined portion is formed. Only the light emitting surface 32 may be thinned.

  The light guide 3 used for the surface light source of the present invention is manufactured as follows. The light guide 3 of the present invention can be produced by methods such as injection molding and imprinting. Further, in the case of a thin light guide having a thickness of 0.8 mm or less, or a light guide having a large area of 15 inches or more in screen size, the linear groove 33 or the linear protrusion 34 is highly accurately and reproducibly reproduced. From the viewpoint that it can be molded, the imprint method is preferred. In addition, when the film thickness of the light guide 3 is 0.8 μm or more and the screen size is 15 inches or less, either injection molding or imprinting can be suitably used.

  In the imprint method, the light guide 3 can be obtained by cutting into a desired shape after molding and polishing the side surface portion.

  The resin constituting the light guide 3 has a constant refractive index such as acrylic resin such as PMMA, polycarbonate resin, polyolefin resin such as polypropylene, polyisobutylene, polybutene, polymethylpentene, and cycloolefin resin. It is preferable to use a transparent resin material.

[Reflection sheet]
The reflection sheet 4 is provided on the light non-emitting surface 35 side of the light guide 3. The reflection sheet 4 reflects the light emitted from the light non-emitting surface 35 of the light guide 3 to the light guide 3. The characteristics, material, structure, etc. of the reflection sheet 4 are the same as those of the reflector 2.

[First optical film]
The surface light source of the present invention is characterized in that a specific first optical film 5 is provided on the light emitting surface 31 of the light guide 3.

In the present invention, the first optical film 5 has anisotropic diffusibility, and the direction in which the anisotropic diffusibility is maximum is substantially parallel to the longitudinal direction of the linear groove 33 or the linear protrusion 34. Is arranged. In this specification, “anisotropic diffusivity” refers to an output angle distribution of light transmitted when a light beam is incident from a direction perpendicular to the film surface using an automatic goniophotometer. Means that the transmitted light spreads differently depending on the measurement direction. A known device may be used for the automatic goniophotometer. For example, an automatic goniophotometer GP200 (Murakami Color Research Laboratory) or an automatic goniophotometer having a function equivalent to or higher than that may be used. Specifically, as shown in FIG. 8, the exit angle on the horizontal axis, when plotted as amount of light on the vertical axis, with respect to the emission amount T ₀ in the normal direction, half of the light intensity (T _0/2) The angle width at this time is defined as a half-value width D, which means that the half-value width D varies depending on the measurement direction. Here, the anisotropic diffusivity is a value measured by making the light incident from a smoother surface.

  Further, “the direction in which the anisotropic diffusibility is maximized” is a measurement direction in which the half-value width D of the transmitted light is maximized. On the other hand, the “direction in which the anisotropic diffusivity is minimum” is a measurement direction in which the half-value width D of the transmitted light is minimum. In the surface light source of the present invention, the direction in which the anisotropic diffusibility of the first optical film 5 is maximized and the length direction of the linear groove 33 or the linear protrusion 34 of the light guide 3 are arranged substantially in parallel. Thereby, the light radiate | emitted from the light guide 3 can be utilized efficiently. As a result, a surface light source with high luminance can be obtained. Here, substantially parallel means, as shown in FIG. 9, the longitudinal direction (d1) of the linear groove 33 or the linear protrusion 34 and the direction (d2) in which the anisotropic diffusion property of the first optical film 5 is maximized. ) Is within 0 ± 15 °. More preferably, θ5 is within 0 ± 10 °, and further preferably within 0 ± 5 °. As described above, when the adjacent linear grooves 33 or the linear protrusions 34 are bent or curved, the main direction and the anisotropic diffusion of the first optical film 5 are maximum. The angle formed by the direction becomes as θ5.

  The first optical film 5 has a half-value width D1max of transmitted light in the direction in which the anisotropic diffusivity is maximized when light is incident from the normal direction, and the difference when the light is incident from the normal direction. It is preferable that the ratio D1max / D1min of the half-value width D1min of transmitted light in the direction in which the direction diffusibility is minimum is 3 or more. More preferably, D1max / D1min is 5 or more, and further preferably D1max / D1min is 7 or more. If D1max / D1min is less than 3, light emitted from the light emitting surface 32 of the light guide 3 may be scattered more than necessary or the luminance may be reduced. By setting D1max / D1min of the first optical film 5 to 3 or more, the light emitted from the light emitting surface 32 of the light guide 3 can be transmitted with high efficiency. As a result, a high-luminance surface light source can be obtained. Moreover, also when using the 2nd optical film 6 mentioned later, a high brightness improvement effect can be acquired.

  The first optical film 5 preferably has a half-value width D1min of transmitted light of 10 ° or less in a direction in which anisotropic diffusivity is minimized when light is incident from the normal direction. More preferably, it is 7 ° or less, and further preferably 5 ° or less. If D1min exceeds 10 °, the light emitted from the light emitting surface 32 of the light guide 3 may be scattered more than necessary or the luminance may be lowered. In the surface light source of the present invention, the light emitted from the light emitting surface 32 of the light guide 3 can be transmitted with high efficiency by setting D1min of the first optical film 5 to 10 ° or less. As a result, a high-luminance surface light source can be obtained. Moreover, also when using the 2nd optical film 6 mentioned later, a high brightness improvement effect can be acquired.

  The first optical film 5 preferably has a total light transmittance of 45% or more. More preferably, the total light transmittance is 50% or more. The total light transmittance here is the amount of light transmitted through the film relative to the amount of incident light when light is incident on the film using a light source (preferably a standard light source, see JIS Z-8720 (2000 edition)). Refers to the ratio. In addition, when uneven | corrugated shape is formed in the one surface of the optical film 5, the value measured by making it enter from a smoother surface is made into the total light transmittance. If both surfaces of the optical film 5 are uneven, or if both surfaces are smooth, the larger value of the values measured by entering from both surfaces is transmitted through the entire light beam. Rate. If the total light transmittance of the first optical film 5 is less than 45%, the light emitted from the light guide 3 may not be used efficiently. Thus, it can be set as a high-intensity surface light source by making the total light transmittance of the 1st optical film 5 into 45% or more.

The first optical film 5 preferably has a haze of 70% or more. More preferably, the haze is 75% or more, and still more preferably, the haze is 80% or more. As used herein, haze refers to the percentage of the amount of light that has been scattered and transmitted away from the incident light beam by 2 ° or more while the incident light passes through the sample from a light source (preferably a standard light source, JIS Z-8720 (2000 version)). H _t ), which is obtained by the following relational expression.
H _t = 100 × (T _d / T _t )
Here, T _d is diffuse transmittance, T _t is the total light transmittance, when the linear transmittance and T _p, is represented by the equation below.
T _t = T _d + T _p

  In addition, when the uneven | corrugated shape is formed in one surface of the optical film 5, the value measured by making it enter from a smoother surface is made into a haze value. In the case where irregularities are formed on both surfaces of the optical film 5 or when both surfaces are smooth, the larger value of the values measured by entering from both surfaces is the haze value. To do. If the haze is less than 70%, light cannot be sufficiently diffused, so that the in-plane luminance distribution as a surface light source and the viewing angle characteristics may be deteriorated. In the surface light source of the present invention, by setting the haze of the first optical film 5 to 70% or more, a surface light source having high luminance and excellent viewing angle characteristics can be obtained.

  The first optical film 5 more preferably has a total light transmittance of 45% or more and a haze of 70% or more. More preferably, the total light transmittance is 50% or more, the haze is 75% or more, particularly preferably the total light transmittance is 50% or more, and the haze is 80% or more. By setting the total light transmittance of the first optical film 5 to 45% or more and the haze to 70% or more, a high-luminance surface light source can be obtained.

  The film used as the first optical film 5 is not particularly limited as long as it has anisotropic diffusibility. FIG. 10 is a diagram showing an example of the first optical film in the present invention. As shown in FIG. 10 (a), rod-like particles (including rod-shaped and spindle-shaped) having a different refractive index from the resin constituting the film are arranged in one direction to develop anisotropic diffusibility. It may be. Alternatively, a plurality of shapes in which the cross section as shown in FIGS. 10B and 10C is curved and arranged in one direction in a stripe shape, or a spindle shape as shown in FIG. An anisotropic diffusivity may be developed by providing irregularities on at least one surface of the film, which is represented by such a shape. Alternatively, a combination of these shapes may be used. The cross-sectional shape may be regular as shown in FIG. 10 (b) or irregular as shown in FIGS. 10 (c) and 10 (d). Among these, it is possible to obtain strong anisotropic diffusibility, and it is easy to control the light diffusibility, so that at least one surface of the film has irregularities on at least one surface. It is more preferable to use one that expresses.

  When a film that exhibits anisotropic diffusivity due to the surface shape is used as the first optical film 5, when the first optical film 5 is placed on the light guide 3, the surface on which the unevenness is provided is an observer. It is preferable to mount so as to be located in the direction. This is because it becomes easy to control the distribution of light emitted from the surface light source.

  The thickness FL1 of the first optical film 5 is preferably 30 to 1000 μm in terms of the handleability and workability of the film. More preferably, it is 50-700 micrometers, Most preferably, it is 75-500 micrometers. Here, when the surface is smooth as shown in FIG. 10 (a), the film thickness FL1 is the thickness of the film, and the shape is provided only on one surface as shown in FIG. 10 (b). The thickness from the apex of the convex part to the surface on the side where the shape is not provided. Moreover, when uneven | corrugated shape is provided in both surfaces, the thickness from the vertex of the convex part of one surface to the vertex of the convex part of the other surface is said. As shown in FIGS. 10C and 10D, when the uneven shape has a different height depending on the location, the average value of the thickness from the apex of the convex portion to the surface on the side where the shape is not provided is It is assumed that the thickness of the optical film (1) 1 is FL1.

  The first optical film 5 is manufactured as follows, for example. As the first optical film 5, as shown in FIG. 10 (a), an optical film containing rod-like particles inside the film is processed into a sheet of resin material in which rod-like particles having different refractive indexes are dispersed. A method in which the sheet is stretched at least in a uniaxial direction so that the rod-shaped particles inside are aligned in one direction, and a resin in which an incompatible thermoplastic resin having a different refractive index is dispersed is dispersed in the sheet. It can be manufactured by a method of extending a thermoplastic resin into a rod shape and arranging it in one direction. The material of the resin material, the rod-like particle, and the incompatible resin is not particularly limited, and any combination having different refractive indexes can be preferably used.

  In addition, as the first optical film 5, as shown in FIGS. 10B to 10D, those that form irregularities on at least one surface of the film are, for example, a coating containing rod-shaped particles on the film surface. It can be manufactured by a method of coating while controlling the direction, a method of providing irregularities on the surface by hairline processing (processing to scratch the film surface), a method of providing irregularities on the surface by a thermal imprint method or a light imprint method, etc. it can. Among these, the thermal imprint method and the optical imprint method are particularly preferable from the viewpoint that the uneven shape and size can be controlled.

  The thermal imprint method is to heat a mold with a fine surface shape and a base resin film (base film), press the mold against the base film, cool, release, and mold surface This is a technique for transferring the shape applied to the base film. The resin used in the thermal imprint method may be a thermoplastic resin or a thermosetting resin, but a highly transparent resin is preferable. Specific examples of resins suitable for thermal imprinting include polyester resins such as polyethylene terephthalate, polyethylene-2, 6-naphthalate, polypropylene terephthalate, and polybutylene terephthalate, polyethylene, polystyrene, polypropylene, polyisobutylene, polybutene, poly Polyolefin resins such as methylpentene, cycloolefin resins, polyamide resins, polyimide resins, polyether resins, polyester amide resins, polyether ester resins, acrylic resins, polyurethane resins, polycarbonate resins, poly A vinyl chloride resin or the like can be used. Among them, polyester resins, polyolefin resins, cycloolefin resins, polyamide resins, acrylic resins are particularly preferred because of the variety of monomer types to be copolymerized and the ease of adjusting the material properties. Alternatively, it is preferably mainly composed of a thermoplastic resin selected from a mixture thereof.

  If these resins have high crystallinity, they may crystallize in the preheating step during thermal imprinting to become white or formability may deteriorate. For this reason, it is preferable to use a low crystallinity, and it is more preferable to use an amorphous resin. For example, in the case of a polyester resin, in order to lower the crystallinity, isophthalic acid, cyclohexanedimethanol, bisphenol A, 2,6-naphthalenedicarboxylic acid, spiroglycol, 9,9′-bis (4-hydroxyethoxyphenyl) ) Resin crystallization can be suppressed by copolymerizing fluorene or the like.

  The photoimprint method is a state in which a photocurable resin layer is applied on a base film and then a mold having a fine surface shape is pressed on the photocurable resin layer, or photocurable on the mold. After applying the resin, the substrate film was overlaid, irradiated with light rays such as ultraviolet rays from the mold side or film side, cured the photocurable resin, and then released, and applied to the mold surface This is a technique for transferring the shape to a resin. Any resin suitable for optical imprinting can be used as long as it reacts within or between molecules by the action of electromagnetic waves and undergoes cross-linking polymerization. Vinyl, vinylidene, acryloyl, methacryloyl can be used in the molecule. Group [Hereinafter, the acryloyl group and the methacryloyl group are collectively referred to as a (meth) acryloyl group. The same expression is used for (meth) acryl, (meth) acrylate, and the like. ] Having a structure such as a maleimide group or an epoxy group can be used. Among these, a compound having a (meth) acryloyl group, an epoxy group, or an oxetane group is preferably used because of its high crosslinking rate. As these compounds that can be crosslinked by irradiation with electromagnetic waves, not only monomers but also those obtained by appropriately mixing prepolymers, oligomers, and / or monomers can be suitably used. Examples of prepolymers and oligomers that can be crosslinked by irradiation with electromagnetic waves include unsaturated polyesters such as condensation products of unsaturated dicarboxylic acids and polyhydric alcohols, polyester (meth) acrylates, polyether (meth) acrylates, polyols (meta ) Acrylate, melamine (meth) acrylate cationic polymerization type epoxy compound.

  The first optical film 5 has various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, and an organic lubricant as long as the effects of the present invention are not impaired. Pigments, dyes, fillers, antistatic agents, nucleating agents, and the like may be blended.

[Second optical film]
In the surface light source of the present invention, it is preferable that the second optical film 6 is mounted on the first optical film 5. Here, the 2nd optical film 6 is a sheet-like thing which can change the outgoing angle distribution from the 1st optical film 5. FIG. When the second optical film 6 is used, the luminance of the surface light source can be increased, the uniformity can be increased, and the viewing angle can be controlled. As a result, the quality as a surface light source can be improved. Examples of the second optical film 6 include a prism sheet and a diffusion sheet having isotropic diffusibility (hereinafter referred to as “isotropic diffusible film”).

(Prism sheet)
FIG. 11 is a diagram showing an example of a prism sheet that can be used as the second optical film 6 in the present invention. As the prism sheet, for example, when the shape is constant over the surface (FIG. 11A), when prisms of various heights are mixed (FIG. 11B), the prism pitches are various. When mixed (FIG. 11 (c)), when various prism apex angles are mixed (FIG. 11 (d)), and combinations thereof can be used. Further, as shown in FIG. 11E, a prism whose apex angle is an arc may be used.

  The apex angle θ3 of the prism of the prism sheet is preferably 80 ° to 100 °. More preferably, θ3 is 83 to 97 °, and further preferably θ3 is 86 to 94 °. If the apex angle of the prism is less than 80 ° or more than 100 °, the utilization efficiency of light from the light guide 3 through the first optical film 5 may be lowered. By setting the apex angle θ3 of the prism sheet within the range of 80 to 100 °, a surface light source with high light utilization efficiency can be obtained. When prisms having different prism apex angles are mixed, the apex angles may be within the above range.

  When a prism sheet is used as the second optical film 6, it is preferable that the length direction of the prism is set substantially parallel to the direction in which the anisotropic diffusion property of the first optical film 5 is maximized. Here, “substantially parallel” means that, as shown in FIG. 12, the angle θ 6 formed by the length direction (d 3) of the prism and the direction (d 2) in which the anisotropic diffusion property of the first optical film 5 is maximum is 0. It means within ± 15 °. More preferably, θ6 is within 0 ± 10 °, and further preferably θ6 is within 0 ± 5 °. By installing in this direction, a surface light source with high light utilization efficiency can be obtained as described later.

  As a manufacturing method of the prism sheet, an optical imprint method is preferably used. After the photocurable resin is applied on the base film, the photocurable resin is applied to the die having the prism shape formed on the photocurable resin layer or pressed onto the die having the prism shape. Then, in a state where the base film is overlaid, it was applied to the mold surface by irradiating light such as ultraviolet rays from the mold side or the film side, curing the photocurable resin and then releasing the mold. The shape can be formed on the film surface. As the resin to be used, the same resins as those mentioned in the case of the first optical film 5 can be used.

(Isotropic diffusive film)
The isotropic diffusive film that can be used as the second optical film 6 is a diffusion sheet having isotropic diffusibility. In this specification, “isotropic diffusibility” means the half-value width D2max of transmitted light in the direction in which the diffusivity is maximum when light is incident from the normal direction of the second optical film 6, and the method This means that the ratio D2max / D2min of the half-value width D2min of transmitted light in the direction in which the isotropic diffusivity is minimum when light is incident from the linear direction is 5 or less. More preferably, D2max / D2min is 3 or less, further preferably 2 or less, and most preferably D2max / D2min is 1.5 or less. Here, the meanings of “the direction in which the diffusibility is maximized”, “the direction in which the diffusibility is minimized”, and “half width” are the same as those in the first optical film 5 described above. When the half width ratio D2max / D2min exceeds 5, there is a possibility that the uniformity will be reduced or the luminance will be greatly changed depending on the viewing angle in the surface light source plane. In the surface light source of the present invention, when an isotropic diffusive film is used as the second optical film 6, the surface light source excellent in viewing angle characteristics and display characteristics can be obtained by setting the half width ratio D2max / D2min to 5 or less. can do.

  Here, when D2max / D2min is larger than 1 and in the range of 5 or less, the direction in which the anisotropic diffusivity of the first optical film 5 is maximized and the direction in which the diffusibility of the second optical film is maximized Is preferably substantially vertical. Here, “substantially perpendicular” means that the angle θ7 formed by the longitudinal direction of the adjacent linear grooves 33 or linear protrusions 34 and the direction in which the second optical film 6 has the maximum diffusibility is within 90 ± 15 °. It means that there is. More preferably, θ7 is within 90 ± 10 °, and further preferably within 90 ± 5 °.

  The isotropic diffusive film preferably has a half-value width D2min of transmitted light in the direction in which the diffusibility is minimized when light is incident from the normal direction, from 2 to 50 °. More preferably, it is 3-30 degrees, More preferably, it is 4-15 degrees. When D2min is less than 2 °, the linear groove 33 or the linear protrusion 34 of the light guide 3 may be visually recognized, the uniformity in the surface light source plane may be reduced, or the luminance may be increased depending on the viewing angle. It can change. On the other hand, if it exceeds 50 °, the light use efficiency may decrease, and the luminance of the surface light source may decrease. In this way, by using an isotropic diffusive film in which the half-value width D2min of transmitted light in the direction in which the diffusibility is minimized is in the range of 2 to 50 °, high brightness, viewing angle characteristics, and uniformity are achieved. An excellent surface light source can be obtained.

  The isotropic diffusive film preferably has a haze of 70% or more. More preferably, the haze is 75% or more, and still more preferably, the haze is 80% or more. The haze is a value measured by making the light incident from a smoother surface. If the haze is less than 70%, light cannot be sufficiently diffused, so that the in-plane luminance distribution as a surface light source and the viewing angle characteristics may be deteriorated. In the surface light source of the present invention, by setting the haze of the second optical film 6 to 70% or more, a surface light source having high luminance and excellent viewing angle characteristics can be obtained. In addition, the definition of haze is the same as the definition of haze in the 1st optical film 6 mentioned above.

  More preferably, the isotropic diffusing film has a total light transmittance of 50% or more and a haze of 70% or more. More preferably, the total light transmittance is 55% or more, the haze is 75% or more, particularly preferably the total light transmittance is 60% or more, and the haze is 80% or more. By setting the total light transmittance to 50% or more and the haze to 70% or more, a surface light source having high luminance, excellent viewing angle characteristics and uniformity can be obtained.

  FIG. 13 shows a specific example of an isotropic diffusive film. As an isotropic diffusive film, for example, a film containing spherical particles having a refractive index different from that of the resin constituting the film (FIG. 13 (a)), a film containing spherical particles is formed on the film surface. (FIG. 13 (b)), a substantially dome-like shape obtained by cutting out a half of a substantially spherical shape (FIG. 13 (c)), or a film having an irregular shape formed on at least one surface of the film, or A combination of these may be used. By adopting such a shape, isotropic diffusibility can be expressed. The cross-sectional shape of these films and uneven shapes may be regular or irregular. An isotropic diffusive film in which unevenness is provided on at least one surface of the film is more preferable in that high diffusibility can be obtained and the light diffusibility can be easily controlled.

  The thickness FL2 of the isotropic diffusive film is preferably 30 to 1000 μm, more preferably 50 to 700 μm, and particularly preferably 75 to 500 μm in terms of the handleability and workability of the film. Here, the thickness FL2 of the film is the thickness when the surface is smooth as shown in FIG. 13 (a), and the shape is provided only on one surface as shown in FIG. 13 (b). The thickness from the top of the convex part to the surface on the side where the shape is not provided is indicated. Moreover, when the shape is provided in both surfaces, the thickness from the vertex of the convex part of one surface to the vertex of the convex part of the other surface is pointed out. As shown in FIG. 13C, when the height varies depending on the location, the average value is the thickness FL2 of the second optical film 6. The thickness of this film is the same for the prism sheet.

  An isotropic diffusive film having isotropic diffusibility inside the film as shown in FIG. 13A is obtained by processing a resin material in which substantially spherical particles having different refractive indexes are dispersed into a sheet shape. be able to. In addition, stretching the sheet uniaxially or biaxially is also preferably performed in terms of improving mechanical strength.

  In addition, in order to give plane stability and dimensional stability to a uniaxially or biaxially stretched film, and to eliminate voids (voids) generated between substantially spherical particles having different refractive indexes and a resin as necessary. Subsequently, an isotropic diffusive film in which spherical particles are dispersed inside the film is manufactured by performing heat treatment (heat setting) in the tenter, and after the heat treatment, uniformly cooling and then cooling to near room temperature.

  Further, as a method for forming an isotropic diffusibility by forming an uneven shape on at least one surface of the film as an isotropic diffusive film, as shown in FIG. And a method of providing irregularities on the surface by a thermal imprinting method or a light imprinting method. About the method by the thermal imprint method or the optical imprint method, it can produce with the method similar to the manufacturing method of the 1st optical film 5.

  In the second optical film 6 used in the present invention, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic absorber, and the like can be used without departing from the effects of the present invention. Lubricants, pigments, dyes, fillers, antistatic agents and nucleating agents may be blended.

[High brightness]
The surface light source of the present invention uses the film having the anisotropic diffusibility as the first optical film 5, the direction in which the diffusibility is maximized, and the linear grooves 33 or the linear protrusions 34 of the light guide 3. Brightness can be increased by arranging them substantially parallel to the direction. Further, by disposing a specific film as the second optical film 6, it is possible to obtain a surface light source having high luminance, excellent viewing angle characteristics, and excellent uniformity, which cannot be achieved by a conventional surface light source. Details will be described.

  First, a mechanism for increasing the brightness will be described. FIG. 14 is a diagram showing the light transmission characteristics of the prism sheet. The light (λi1) incident on the prism sheet from near the normal direction repeats total reflection at the prism / air interface, and as a result, returns to the opposite direction of the normal and does not pass through the prism sheet. The returned light can be reused if it is reflected using a reflective sheet. However, if reflection is repeated, the light beam is lost due to deactivation.

  Next, the light (λi3) incident on the prism sheet at a large angle has a large reflection on the sheet surface. Even if it is incident, it is refracted in the direction opposite to the normal direction at the prism / air interface and becomes stray light. This results in a loss of light.

  On the other hand, light (λi2) incident near an incident angle of ± 30 ° is refracted at the incident surface and the prism / air interface, and can be efficiently polarized in the normal direction. Therefore, in order to increase the luminance using the prism sheet, it is important to increase the λi2 component.

  In the case of a configuration that does not use a prism sheet, it cannot be oriented in the normal direction by refraction at the surface as in the case of using a prism sheet. For this reason, in order to increase the luminance, it is necessary to emit a large amount of the emission angle distribution from the light guide 3 in the normal direction.

  That is, in order to achieve high brightness, it is important to control the type of optical film and the emission characteristics from the light guide 3. Specifically, when a prism sheet is used as the second optical film, it is important to increase the incident light at an incident angle of about ± 30 °. Moreover, when not providing a 2nd optical film, when using an isotropic diffusion sheet as a 2nd optical film, it becomes important to increase the light of a normal line direction. Based on the above concept, a mechanism for increasing the luminance of the surface light source of the present invention will be described with reference to FIGS. The surface light source of the present invention is not limited to these.

  FIG. 15 is a diagram schematically illustrating the light that propagates through the light guide and exits. FIG. 15A is a diagram schematically showing light propagating through the light guide 3. In the example of this figure, a triangular linear groove 33 is formed on the opposite side of the light emitting surface 32 as the light guide 3. The light incident from the light incident surface 31 is parallel to the surface of the light guide 3 and propagates without hitting the light exit surface 32 and the light non-exit surface 35, and the light exit surface 32 of the light guide 3 or the light non-light. There is light that repeats total reflection at the exit surface 35 and propagates through the light guide 3. Of the light propagating in the light guide 3, the light colliding with the linear groove 33 is reflected on the surface of the linear groove 33, and the traveling direction thereof is changed. As a result, the light is incident on the light emitting surface 32 at a critical angle or less, and is emitted to the outside of the light guide 3 (FIG. 15A, λp1, λp2, λp3).

  FIGS. 15B to 15G are diagrams schematically illustrating an optical path of light that collides with the linear groove 33 or the linear protrusion 34. 15B to 15G is an example in the case of the linear groove 33, the same applies to the case of the linear protrusion 34. FIG. FIGS. 15B to 15D show the case where the angle θ1 = 45 ° formed by the slope located on the light source side in the linear groove provided in the light guide and the straight line perpendicular to the light source 1. FIGS. 15E to 15G are examples in the case of an angle θ1 = 40 ° formed between a slope located on the light source side in a linear groove provided in the light guide and a straight line perpendicular to the light source 1. It is. FIGS. 15B and 15E show examples of light colliding with the linear groove 33 substantially parallel to the light guide surface. FIGS. 15C and 15F show the linear groove 33 from the light emitting surface side 35. FIGS. 15D and 15G show examples of light that collides with the linear groove 33 after being reflected from the non-light-emitting surface 35. When θ1 is 42.5 to 50 °, the same principle as when θ1 = 40 ° can be regarded as the same principle as when θ1 = 45 °. In the case of the linear protrusion 34, θ2 is the same as θ1.

  In the case of θ1 = 45 °, as shown in FIG. 15B, the light (λp1) colliding with the linear groove 33 or the linear protrusion 34 substantially parallel to the surface of the light guide 3 is totally reflected on the inclined surface. Then, the light is emitted in the substantially normal direction of the light emitting surface 32 of the light guide 3 (λo1). However, since it actually becomes a shadow of the adjacent linear groove 33, the amount of light that follows this path is small. Therefore, most of the light collides with the linear groove 33 from the light emitting surface side 32 as shown in FIG. 15C, or is reflected from the non-light emitting surface 35 side as shown in FIG. Collides with the linear groove 33. As shown in FIG. 15C, the light λp2 that collides with the linear groove 33 from the light emitting surface 32 side is totally reflected so as to be returned to the light source 1 side at the inclined surface. Further, as shown in FIG. 15D, the light λp3 reflected from the light non-emitting surface 35 side and colliding with the linear groove 33 is totally reflected in the direction opposite to the light source 1 side on the inclined surface. Thus, the light reflected by the inclined surface is refracted and emitted opposite to the normal direction at the light emitting surface 32 (λo2, λo3). That is, in the case of θ1 = 45 °, many light beams can be emitted in a direction inclined obliquely from the normal direction.

  On the other hand, at θ1 = 40 °, as shown in FIG. 15 (e), the light (λp1) colliding with the linear groove 33 substantially parallel to the surface of the light guide 3 is totally reflected on the inclined surface, and the light guide 3 is emitted in the substantially normal direction of the light emitting surface 32 (λo1). However, in actuality, since it becomes a shadow of the adjacent linear groove 33 or linear protrusion 34, the amount of light that follows this path is small. Therefore, most of the light collides with the linear groove 33 from the light emitting surface 32 side as shown in FIG. 15F, or the linear groove 33 from the non-light emitting surface 35 side as shown in FIG. Collide with. As shown in FIG. 15 (f), the light λp 2 that collides with the linear groove 33 from the light emitting surface 32 side is totally reflected so as to return to the light source 1 side on the inclined surface, and is normal to the light emitting surface 32. On the contrary, the light is refracted and emitted (λo2). However, the emission angle θo2 is smaller than when θ1 = 45 °. Further, as shown in FIG. 15G, the light λp3 reflected from the non-light-emitting surface 35 and colliding with the linear groove 33 is totally reflected in the direction opposite to the light source 1 side on the inclined surface. The light reflected by the inclined surface is refracted and emitted opposite to the normal direction at the light exit surface 32 (λo3). The emission angle θo3 is larger than when θ1 = 45 °. When θ1 = 40 °, the angle at which the reflected light enters the exit surface 32 of the light guide 3 is larger than when θ1 is 45 °. For this reason, the amount of light that is totally reflected, returns to the light guide 3 and propagates again in the light guide 3 increases. That is, in the case of θ1 = 40 °, many light beams can be emitted in the normal direction.

  From the above, if the angle θ1 formed between the slope located on the light source side in the linear groove provided in the light guide and the straight line perpendicular to the light source 1 is controlled, the light from the light emitting surface 32 of the light guide 3 It can be seen that the emitted light can be controlled. Specifically, when θ1 is 42.5 ° to 45 °, many rays can be emitted in an oblique direction, and when θ1 is 20 to 42.5 °, many rays can be emitted in the normal direction.

  FIG. 16 is a diagram for explaining an example of an emission angle distribution of outgoing light from the light outgoing surface 32 of the light guide 3 in the surface light source of the present invention. Note that the emission angle distribution described in the example of FIG. 16 is such that, as shown in FIG. 2A, in a surface light source in which two light sources 1 and a reflector 2 face each other with the light guide 3 interposed therebetween, the light guide 3 is an example showing an emission angle distribution from a central portion of the light emitting surface 32 of No. 3; This is an example in which a triangular linear groove 33 is formed in the direction parallel to the light incident surface 31 on the light non-emitting surface 35 side as the light guide 3. 16A and 16B show the emission angle distributions when θ1 = 45 °, and FIGS. 16C and 16D show the emission angle distributions when θ1 = 40 °. 16A and 16C show the emission angle distribution in a plane perpendicular to the length direction of the linear groove 33 (hereinafter simply referred to as a plane perpendicular to the linear groove 33). FIGS. 16B and 16D show emission in a plane parallel to the length direction of the linear groove 33 including the normal direction of the light emission surface 32 (hereinafter simply referred to as a plane parallel to the linear groove 33). Angular distribution.

  FIG. 17 shows an anisotropic diffusion film or isotropic diffusion on the light guide 3 of the surface light source in the form in which the two light sources 1 and the reflector 2 face each other with the light guide 3 interposed therebetween, as shown in FIG. It is an example which shows the outgoing angle distribution from the center part when a film is mounted. 17A and 17B show the emission angle distributions when θ1 = 45 °, and FIGS. 17C and 17D show the emission angle distributions when θ1 = 40 °. 17A and 17C show the emission angle distribution in a plane perpendicular to the linear groove 33. FIG. 17B and 17D show the emission angle distribution in the plane parallel to the linear groove 33. FIG.

  In the surface light source of the present invention, when the angle θ1 = 45 ° of the inclined surface on the light source 1 side of the linear groove 33 of the light guide 3 is a surface perpendicular to the linear groove 33 as shown in FIG. Inside, much light can be emitted in the vicinity of the ± 30 ° direction. On the other hand, in a plane parallel to the linear groove 33, a broad emission angle distribution having a maximum point in the vicinity of the ± 40 ° direction is obtained (FIG. 16B). That is, by controlling the angle θ1 of the inclined surface of the linear groove 33 on the light source 1 side to 45 °, light containing a lot of light in a direction suitable for the prism sheet is emitted in a plane perpendicular to the linear groove 33. Can be made. On the other hand, in other planes (for example, in a plane parallel to the linear grooves 33), a lot of light is emitted in directions other than the direction suitable for the prism sheet. Therefore, if the light can be directed in a direction suitable for the prism sheet, high brightness can be achieved.

  FIGS. 16A and 16B show the emission angle distribution when an anisotropic diffusion film or an isotropic diffusion film is installed on the emission surface 31 of the light guide 3 having the emission angle distribution. When an isotropic diffusive film is used, light is evenly diffused and the emission angle distribution from the light guide 3 is destroyed. In other words, the light emitted from the light guide 3 has a large emission angle of around ± 30 °, but when the light further passes through the isotropic diffusing film, the amount of light around the emission angle of ± 30 ° decreases. For this reason, the amount of light emitted in a direction suitable for the prism sheet is reduced, and the efficiency is lowered. On the other hand, when an anisotropic diffusion film having strong anisotropic diffusivity is arranged such that the direction in which the diffusibility is maximized and the length direction of the linear groove 33 are substantially parallel, they are perpendicular to the linear groove 33. Light can be diffused only in a direction parallel to the length direction of the linear groove 33 (FIG. 17B) without being diffused in any direction (FIG. 17A). As a result, the emitted light can be collected in the normal direction of the light emitting surface 32 in a plane parallel to the linear groove 33 without destroying the emission angle distribution in the plane perpendicular to the linear groove 33. . Thereby, it becomes possible to increase the light of a suitable angle for a prism sheet. That is, when a prism sheet is used as the second optical film 6, the brightness can be increased.

  From the above, when a prism sheet is used as the second optical film 6, the slope between the linear groove 33 provided in the light guide 3 on the light source 1 side and the straight line perpendicular to the light source 1 The angle formed between the inclined surface located on the opposite side of the light source 1 in the linear protrusion 34 provided on the light guide 3 and the straight line perpendicular to the light source 1 is 42.5 ° to 50 °. I know it ’s good.

Further, in the surface light source of the present invention, when the angle θ1 = 40 ° of the slope of the linear groove 33 of the light guide 3 on the light source 1 side is set to the linear groove 33 as shown in FIG. In the vertical plane, a large amount of light can be emitted in the vicinity of the 0 ° direction. On the other hand, in the plane parallel to the linear groove 33, a large amount of light is emitted in the vicinity of the ± 40 ° direction (FIG. 16D). When an anisotropic diffusion film is provided on this light guide, light containing a large amount of light in the 0 ° direction can be emitted in the direction perpendicular to the linear groove 33 (FIG. 17C). Further, even in other planes (for example, in a plane parallel to the linear groove 33), when an anisotropic diffusion film is provided, the light emitted in a direction other than the 0 ° direction is directed in the normal direction of the light emitting surface 32. (FIG. 17D). On the other hand, when an isotropic diffusion film is used, it is 0 ° both in the direction perpendicular to the linear groove 33 and in other planes (for example, in the plane parallel to the linear groove 33), compared to the anisotropic diffusion film. Light emitted in directions other than the direction can be directed in the normal direction of the light exit surface 32 (FIGS. 17C and 17D). That is, by using an anisotropic diffusion film as the first optical film 5 and controlling the angle θ1 of the inclined surface on the light source 1 side of the linear groove 33 to 40 °, the emission of light in the normal direction increases. I understand.

  Thus, the angle formed by the slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 and the straight line perpendicular to the light source 1, or the linear protrusion provided in the light guide 3 If the angle formed between the inclined surface located on the opposite side of the light source 1 in 34 and the straight line perpendicular to the light source 1 is 20 ° to 42.5 °, the emission of light in the normal direction increases. Therefore, under these conditions, it can be seen that a high-luminance surface light source can be obtained even when the second optical film 6 is not used.

  Further, as described above, even when a light diffusion sheet is used as the second optical film 6, if the light in the normal direction is large, the surface light source can have high brightness. That is, also in this case, the angle formed by the slope located on the light source 1 side in the linear groove 33 provided in the light guide 3 and the straight line perpendicular to the light source 1, or the line provided in the light guide 3 It is preferable that the angle formed between the inclined surface located on the opposite side of the light source 1 in the projection 34 and the straight line perpendicular to the light source 1 is 20 ° to 42.5 °.

[Surface light source]
In the surface light source of the present invention having the above configuration, the in-plane luminance uniformity U is preferably 65% or more. More preferably, it is 70% or more, More preferably, it is 75% or more, Most preferably, it is 80% or more. Here, the luminance uniformity U is measured using a color luminance meter at a viewing angle of 1 ° at 25 points in the surface light source shown in FIG. 18A for a screen size of 5 inches or more. In the case of a screen size of 5 inches or less, when the luminance at nine points in the surface light source shown in FIG. 18B is measured at a measurement viewing angle of 0.2 °, respectively, from the maximum luminance Bmax and the minimum luminance Bmin, It is a value calculated from the following formula. A known color luminance meter can be used for measuring the uniformity. For example, it is preferable to use BM-7 / FAST (manufactured by Topcon Co., Ltd.) or equivalent or higher.
U = Bmin / Bmax × 100
By setting the uniformity U to 65% or more in the surface light source of the present invention, good display characteristics can be obtained.

In the surface light source of the present invention, either the vertical viewing angle or the horizontal viewing angle of the screen is preferably 20 ° or more, more preferably the horizontal viewing angle of the screen is 20 ° or more. There should be. More preferably, it is 25 ° or more, and further preferably 30 ° or more. Here, the viewing angle is a color luminance meter, and the central portion of the surface light source is in the range of ± 80 ° in the vertical direction of the screen or the emission angle distribution in the range of ± 80 ° in the horizontal direction of the screen every 2 °. measured output angle on the horizontal axis, when plotted as a vertical axis represents luminance, the luminance B ₀ in the normal direction, the angular width at a half of the luminance (B _0/2) of the (half-value width W) That is. By setting the viewing angle of the surface light source of the present invention to a range of 20 ° or more, the surface light source can be used for a wide range of applications without being limited to the application. A known color luminance meter can be used for measuring the viewing angle. For example, it is preferable to use BM-7 / FAST (manufactured by Topcon Co., Ltd.) or equivalent or higher.

  The surface light source of the present invention is not limited to the above configuration, and within the range in which the effect of the present invention is not lost, on the second optical film 6, between the light guide 3 / first optical film 5, or the first. It is also possible to insert other films between the optical film 5 and the second optical film 6. It is also possible to combine other films. Examples of films that can be used include other diffusion films, prism sheets, visual field control films, reflective polarizing plates, brightness enhancement films, polarization separation sheets, color tone correction films, and the like. As an example of its use, for example, by further disposing a diffusion film on the second optical film 6, the display quality can be improved or a further luminance improvement effect can be obtained. Further, when the reflective polarizing plate is arranged so that the polarization axis thereof coincides with the polarization axis of the liquid crystal display device, it is possible to increase the light use efficiency and achieve higher luminance.

  The surface light source of the present invention is superior to conventional surface light sources in terms of light utilization efficiency, high brightness, and wide viewing angle. Cellular phones, electronic notebooks, notebook PCs, monitors, TVs, various display media It can use suitably for the use which irradiates a liquid crystal display element from a back surface, such as.

  The liquid crystal display device of the present invention is equipped with the above-described surface light source. By using the surface light source of the present invention, a clear liquid crystal display device having high luminance, excellent viewing angle characteristics and uniformity can be obtained.

[Characteristic evaluation method]
As a method for evaluating characteristics in the present invention, the following method is used. As the measuring device, other devices may be used as long as the result is equal to or higher than the following evaluation method.

A. Total light transmittance, haze Using a fully automatic direct reading haze computer HGM-2DP, manufactured by Suga Test Instruments Co., Ltd., the total light transmittance and haze of the film are measured. In the film plane, the measurement was carried out at five locations, and the total light transmittance and haze were determined by the average value. A standard light source (see JIS Z-8720 (2000)) is used as the light source.
Note that the total light transmittance and haze are values measured by making the light incident from a smoother surface when an uneven shape is formed on one surface of the optical film. In addition, when the concave and convex shapes are formed on both surfaces of the optical film, or when both surfaces of the optical film are smooth, the larger of the values measured by entering from both surfaces is measured. Value.

B. Half width Dmax, Dmin, ratio Dmax / Dmin
With an automatic goniophotometer GP200 (manufactured by Murakami Color Research Laboratory Co., Ltd.), a light beam is incident from a direction perpendicular to the film surface, and a relative transmittance is measured every 1 ° to obtain an emission angle distribution.
From the result of the obtained emission angle distribution, a half-value width Dmax in the direction in which the diffusibility is maximized and a half-value width Dmin in the direction in which the diffusibility is minimized are obtained. In the film plane, the same measurement is performed at five different locations, the average values of the half-value widths Dmax and Dmin are obtained, and the half-value width ratio Dmax / Dmin is obtained from these average values.
Note that the half-value widths Dmax and Dmin were measured by making them enter from a smoother surface.

C. Evaluation of light guide shape Using a three-dimensional shape measuring instrument NH-3SP (manufactured by Mitaka Kogyo Co., Ltd.) The depth H1 or the height H2 of the linear protrusion 34, the inclination angle θ1 or θ2 on the light source 1 side, and the surface roughness Ra of the light emitting surface 32 of the light guide are measured.

D. Film cross-sectional structure After cutting out the cross section of the film and depositing platinum-palladium, a photograph is taken with a field emission scanning electron microscope “JSM-6700F” manufactured by JEOL Ltd., and the cross section is observed. In the film plane, the measurement was carried out at five locations. From each cross-sectional photograph, the uneven shape of the film surface (height H, width S, aspect ratio H / S of the convex portion) The dispersion state (dispersion diameter R) inside the film is determined, and the average value of the film surface The uneven shape (height H, width S, aspect ratio H / S of the convex portion) was the dispersion state (dispersion diameter R) inside the film.

E. Luminance, uniformity, viewing angle Light source 1 and reflector 2 as “Lumirror” (registered trademark) E6SV (manufactured by Toray Industries, Inc.), light guide 3, and “Lumirror” E6SL as reflection sheet 4 below light guide 3 Toray Industries, Inc.), the first optical film 5 and the second optical film 6 were arranged on the upper side of the light guide 3 to produce a surface light source. 10 minutes later, using a color luminance meter BM-7 / FAST (manufactured by Topcon Corp.), measuring the luminance at 25 points in the surface light source shown in FIG. For a screen size of 5 inches or less when measured at an angle of 1 °, the luminance at 9 points in the surface light source shown in FIG. 18B was measured at a measurement viewing angle of 0.2 °.

The obtained central luminance was determined according to the following criteria.
1) When a prism sheet is used as the second optical film When 17 inches When the center luminance is 6800 cd / m ² or more: A
When the center luminance is 6700 cd / m ² or more and less than 6800 cd / m ² : B
When the center luminance is 6600 cd / m ² or more and less than 6700 cd / m ² : C
When the center luminance is 6500 cd / m ² or more and less than 6600 cd / m ² : D
When the center luminance is less than 6500 cd / m ² : E

In the case of 7 inches When the center luminance is 7300 cd / m ² or more: A
When the center luminance is 7200 cd / m ² or more and less than 7300 cd / m ² : B
When the center luminance is 7100 cd / m ² or more and less than 7200 cd / m ² : C
When the center luminance is 7000 cd / m ² or more and less than 7100 cd / m ² : D
When the center luminance is less than 7000 cd / m ² : E

In the case of 13.3 inches When the central luminance is 4300 cd / m ² or more: A
When the center luminance is 4200 cd / m ² or more and less than 4300 cd / m ² : B
When the center luminance is 4100 cd / m ² or more and less than 4200 cd / m ² : C
Central luminance 4000 cd / ^{m 2} or more 4100cd / ^{m 2} less than in the case: D
When the center luminance is less than 4000 cd / m ² : E

When 1.8 inches When the center luminance is 6300 cd / m ² or more: A
When the center luminance is 6200 cd / m ² or more and less than 6300 cd / m ² : B
When the center luminance is 6100 cd / m ² or more and less than 6200 cd / m ² : C
When the center luminance is 6000 cd / m ² or more and less than 6100 cd / m ² : D
When the center luminance is less than 6000 cd / m ² : E

2) When an isotropic diffusive sheet is used as the second optical film: In the case of 17 inches When the central luminance is 5500 cd / m ² or more: A
When the center luminance is 5400 cd / m ² or more and less than 5500 cd / m ² : B
When the center luminance is 5300 cd / m ² or more and less than 5400 cd / m ² : C
When the center luminance is 5200 cd / m ² or more and less than 5300 cd / m ² : D
When the center luminance is less than 5200 cd / m ² : E

In the case of 7 inches When the center luminance is 5800 cd / m ² or more: A
When the center luminance is 5700 cd / m ² or more and less than 5800 cd / m ² : B
When the center luminance is 5600 cd / m ² or more and less than 5700 cd / m ² : C
When the center luminance is 5500 cd / m ² or more and less than 5600 cd / m ² : D
When the center luminance is less than 5500 cd / m ² : E

In the case of 13.3 inches When the center luminance is 3300 cd / m ² or more: A
When the center luminance is 3200 cd / m ² or more and less than 3300 cd / m ² : B
When the center luminance is 3100 cd / m ² or more and less than 3200 cd / m ² : C
Central luminance 3000 cd / ^{m 2} or more 3100cd / ^{m 2} less than in the case: D
When the center luminance is less than 3000 cd / m ² : E

In the case of 1.8 inches When the center luminance is 5300 cd / m ² or more: A
When the center luminance is 5200 cd / m ² or more and less than 5300 cd / m ² : B
When the center luminance is 5100 cd / m ² or more and less than 5200 cd / m ² : C
Central luminance 5000 cd / ^{m 2} or more 5100cd / ^{m 2} less than in the case: D
When the center luminance is less than 5000 cd / m ² : E

  In all, A, B, C, and D are good, and E is not good. A, B, C, and D are excellent in this order (A is the most excellent).

Further, the maximum luminance Bmax and the minimum luminance Bmin were obtained from the obtained results, and the uniformity U was calculated from the following formula.
U = Bmin / Bmax × 100
The obtained value was evaluated according to the following criteria. When the uniformity degree U is 80% or more: A
When the uniformity degree U is 70% or more and less than 80%: B
When the uniformity degree U is less than 70%: C
A and B are good, and C is not good. A is the best.

Next, with respect to the central portion of the surface light source, the emission angle distribution in the range of ± 80 ° in the screen vertical direction or ± 80 ° in the horizontal direction of the screen is measured every 2 °. when plotted as luminance, the luminance B ₀ in the normal direction, the angular width at a half of the luminance (B _0/2) a (half-value width W) was viewing angle.

The obtained value was evaluated according to the following criteria. When the viewing angle is 30 ° or more: A
When viewing angle is 25 ° or more and less than 30 °: B
When viewing angle is less than 25 °: C
A and B are good, and C is not good. A is the best.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.
The shape of the light guide used in Examples and Comparative Examples and the production method are as follows.

(Light guide A-1)
Screen size: 17 inches (light guide size: 280 mm long x 349.8 mm wide x 6 mm thick, linear groove forming area: 275 mm long x 349 mm wide, 2.5 mm from the light incident surface. Formed on the exit surface side, smooth surface on the light exit surface side (surface roughness Ra = 8 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 90 °, θ1 = 45 °), and the linear grooves are formed parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 11 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the central linear groove is 33 μm.
Manufacturing method: A mold having the above-mentioned shape inverted and a resin plate of 6 mm thick polycarbonate resin “Iupilon” (registered trademark) HL-4000 (manufactured by Mitsubishi Engineering Plastics) are heated to 160 ° C., Pressed at 500 kN for 30 seconds. Next, after cooling to 80 ° C., the pressure was released to release the mold. The outer periphery of the obtained molded product was cut to adjust the shape, and the light guide 3 was obtained.

(Light guide A-2)
Screen size: 7 inches (92 mm long x 158 mm wide x 300 mm thick, linear groove forming area: 88 mm long x 347 mm wide, linear groove formed on the light non-emitting surface side from the inside of the light incident surface 2.0 mm, light The exit surface is a smooth surface (surface roughness Ra = 9 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 90 °, θ1 = 45 °), and the linear grooves are formed parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 10 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the central linear groove is 36 μm.
Manufacturing method: Using a mold having the above inverted shape, injection molding is performed using polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics), and the length is 92 mm × width 158 mm × thickness 3 mm. A plate-like light guide 3 was obtained.

(Light guide A-3)
Screen size: 13.3 inches (light guide shape: length 186.5 mm × width 289.28 mm × thickness 0.3 mm, linear groove forming area: length 184.0 mm × width 287 mm, 2.5 mm from the light incident surface A linear groove is formed on the non-light-emitting surface side from the inside, and the light-emitting surface side is a smooth surface (surface roughness Ra = 6 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 90 °, θ1 = 45 °), and the linear grooves are formed parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 10 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the linear groove farthest from the light incident surface is 32 μm.
Manufacturing method: Using a mold having the above shape inverted, a resin plate of 0.3 mm thick polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics) is heated to 160 ° C., and then 300 kN. Pressed for 30 seconds. Next, after cooling to 80 ° C., the pressure was released to release the mold. The outer periphery of the obtained molded product was cut to adjust the shape, and the light guide 3 was obtained.

(Light guide A-4)
Screen size: 1.8 inches (light guide size: 40 mm long x 30.5 mm wide x 0.7 mm thick, linear groove forming area: 37 mm long x 30 mm wide, spaced 2.8 mm from the light incident surface) A linear groove is formed on the non-light emitting surface side, and the light emitting surface side is a smooth surface (surface roughness Ra = 10 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 90 °, θ1 = 45 °), and the linear grooves are formed parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 1.8 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the linear groove farthest from the light incident surface is 31 μm.
Manufacturing method: Using a mold having the above-mentioned shape reversed, injection molding was performed using a polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) to obtain a light guide 3.

(Light guide A-5)
Screen size: 17 inches (light guide size: 280 mm long x 349.8 mm wide x 6 mm thick, linear groove forming area: 275 mm long x 349 mm wide, 2.5 mm from the light incident surface. Formed on the exit surface side, smooth surface on the light exit surface side (surface roughness Ra = 8 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 100 °, θ1 = 40 °), and the linear grooves are formed in parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 12 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the central linear groove is 34 μm.
Manufacturing method: A mold with the above shape inverted and a resin plate of 6 mm thick polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics) are heated to 160 ° C., followed by 500 kN for 30 seconds. Pressed. Next, after cooling to 80 ° C., the pressure was released to release the mold. The outer periphery of the obtained molded product was cut to adjust the shape, and the light guide 3 was obtained.

(Light guide A-6)
Screen size: 7 inches (92 mm long x 158 mm wide x 300 mm thick, linear groove forming area: 88 mm long x 347 mm wide, linear groove formed on the light non-emitting surface side from the inside of the light incident surface 2.0 mm, light The exit surface is a smooth surface (surface roughness Ra = 9 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 100 °, θ1 = 40 °), and the linear grooves are formed in parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 11 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the central linear groove is 36 μm.
Manufacturing method: Using a mold with the above shape inverted, injection molding is performed using polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics), and the length is 92 mm × width 158 mm × thickness 3 mm. A plate-like light guide 3 was obtained.

(Light guide A-7)
Screen size: 13.3 inches (light guide shape: length 186.5 mm × width 289.28 mm × thickness 0.3 mm, linear groove forming area: length 184.0 mm × width 287 mm, 2.5 mm from the light incident surface A linear groove is formed on the non-light-emitting surface side from the inside, and the light-emitting surface side is a smooth surface (surface roughness Ra = 7 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 100 °, θ1 = 40 °), and the linear grooves are formed in parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 10 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the linear groove farthest from the light incident surface is 32 μm.
Manufacturing method: Using a mold having the above shape inverted, a resin plate of 0.3 mm thick polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics) is heated to 160 ° C., and then 300 kN. Pressed for 30 seconds. Next, after cooling to 80 ° C., the pressure was released to release the mold. The outer periphery of the obtained molded product was cut to adjust the shape, and the light guide 3 was obtained.

(Light guide A-8)
Screen size: 1.8 inches (light guide size: 40 mm long x 30.5 mm wide x 0.7 mm thick, linear groove forming area: 37 mm long x 30 mm wide, spaced 2.8 mm from the light incident surface) A linear groove is formed on the non-light emitting surface side, and the light emitting surface side is a smooth surface (surface roughness Ra = 8 nm))
Linear groove: The cross-sectional shape is an isosceles triangle (vertical angle 100 °, θ1 = 40 °), and the linear grooves are formed in parallel to the light incident surface at a pitch of 200 μm. The depth of each linear groove varies irregularly in the length direction of the groove. The average depth of the linear groove closest to the light incident surface is 2 μm. The average depth of the linear groove is deeper as the linear groove is farther from the light incident surface. The average depth of the central linear groove is 31 μm.
Manufacturing method: Using a mold having the above-mentioned shape reversed, injection molding was performed using a polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) to obtain a light guide 3.
About the light guide, the angle θ1 formed by the size, form (separate of linear groove or linear protrusion), the formation surface of the linear groove, the inclined surface of the linear groove 33 on the light source 1 side, and a straight line perpendicular to the light source. And the angle θ2 formed by the slope of the linear protrusion 34 facing the light source 1 and the straight line perpendicular to the light source, the depth H1 of the linear groove or the height H2 of the linear protrusion, the linear groove or the linear protrusion The pitch P is summarized in Table 1.

The optical films used in Examples and Comparative Examples are as follows.
(Optical film B-1)
Shape: An approximately sinusoidal random stripe pattern formed by optical interferometry on the film surface (average pitch 15.6 μm, average aspect ratio (= average height / average pitch) 0.63)

Production method: “Adekaoptomer” (registered trademark) KRM-2199 (Asahi Denka Kogyo Co., Ltd.) 10 parts by weight, Aron Oxetane OXT-221 (Toa Gosei Co., Ltd.) 1 part by weight, “Adekaoptomer” 0.25 parts by weight of SP170 (Asahi Denka Kogyo Co., Ltd.) was mixed and stirred to obtain a coating solution. Next, the coating solution was applied to the surface of the mold having a surface shape so that the thickness of the coating film was 50 μm. After the application, a polyester film “Lumirror” # 100U34 (manufactured by Toray Industries, Inc.) was layered on the upper surface of the coating film, and the film was adhered by applying pressure with a roller. Next, after irradiating a total of 1000 mJ / cm ² of ultraviolet rays from the film surface side while maintaining this state, the mold is released, and an optical film having a surface irregularity shape on one surface of the base film is obtained. Obtained.

(Optical film B-2)
Shape: Cylindrical lens shape (Semi-ellipsoidal shape with a longitudinal section of 50 μm in height and 50 μm in width arranged on the film surface at a pitch of 40 μm (see FIG. 19))
Manufacturing method: It was manufactured by the same method as B-1, except that a mold having the above-mentioned shape inverted was used as the mold.

(Optical film B-3)
Shape: A semi-spindle-shaped projection having a major axis of 200 μm, a minor axis of 20 μm, and a height of 20 μm arranged on the film surface. (See Figure 20)
Manufacturing method: It was manufactured by the same method as B-1, except that a mold having the above-mentioned shape inverted was used as the mold.

(Optical film B-4)
Shape: Rod-like particles arranged in one direction inside the film. Average minor axis of rod-like particles 3μm, average major axis 500μm

Production method: In the main extruder, polyethylene terephthalate (PET) as the main resin component constituting the light diffusion film is copolymerized with 10 mol% of isophthalic acid component with respect to the acid unit and 10 mol% of cyclohexanedimethanol component with respect to the glycol unit. Pellets prepared by mixing 94% by volume of the polyester resin (melting point TB: 225 ° C.) and 6% by volume of polymethylpentene (manufactured by Mitsui Chemicals) as a light diffusing element were supplied. Further, a sub-extruder was used separately from the main extruder, and PET (melting point TA: 265 ° C.) pellets were supplied to the sub-extruder. Subsequently, the component layers supplied to the sub-extruder on both side surface layers of the component layer supplied to the main extruder are in a thickness ratio. Sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: 8: The melted three-layer laminate coextrusion was carried out so as to be 1. The extruded resin was cooled by an electrostatic application method onto a cast drum that was rotated at a speed twice the extrusion speed to produce a three-layer laminated sheet. The laminated sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C., and then stretched 3.4 times in the width direction at 110 ° C. through a preheating zone of 95 ° C. with a tenter. Further, the film was heat treated at 235 ° C. for 30 seconds to obtain a film having a thickness of 180 μm containing rod-like particles arranged in the film running direction.

(Optical film B-5)
A diffusion film “TEXCELL” TDS127 manufactured by Toray Sehan was used.

(Optical film B-6)
A diffusion film UTEII manufactured by Millea Nanotech was used.

(Optical film B-7)
Shape: A semi-spindle-shaped protrusion having a major axis of 30 μm, a minor axis of 20 μm, and a height of 20 μm arranged on one surface. (See Figure 21)
Manufacturing method: It was manufactured by the same method as B-1, except that a mold having the above-mentioned shape inverted was used as the mold.

(Optical film B-8)
A diffusion film “TEXCELL” TDA128 made by Toray Sehan was used.

(Optical film B-9)
A diffusion film DX2 manufactured by Kimoto Co., Ltd. was used.

(Optical film C-1)
A 3M prism sheet BEFIII90 / 50T was used.

(Optical film C-2)
A prism sheet THIN-T2 manufactured by Millea Nanotech was used.

(Optical film C-3)
Shape: Prism stripe (vertical angle θ3 = 100 °, pitch 50 μm, height 21 μm)
Manufacturing method: Heated to 160 ° C. a mold (vertical 280 mm × width 350 mm) with the above shape reversed and a resin plate of 0.2 mm thick polycarbonate resin “Iupilon” HL-4000 (manufactured by Mitsubishi Engineering Plastics) Subsequently, pressing was performed at 500 kN for 30 seconds. Next, after cooling to 80 ° C., the pressure was released and the mold was released to obtain an optical film.

  For the optical film, the maximum value Dmax, the minimum value Dmin, Dmax / Dmin, the total light transmittance, the haze, the apex angle θ3 of the prism sheet, the prism pitch, and the prism height are shown in Tables 2 and 3 Shown in

(Example 1-1)
The light guide A-1 is installed so that the surface on which the linear groove is not formed is on the viewer side, and two cold cathode fluorescent lamps (hereinafter referred to as CCFLs) are provided on two opposing light incident surfaces. They were placed one by one, and “Lumiler” E6SV (manufactured by Toray Industries, Inc.) was installed as a reflector around them. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). C-1 as the second optical film on the first optical film B-1, the prism length direction and the direction in which the anisotropic diffusivity of the optical film B-1 is maximized are parallel (that is, θ6 = The surface light source was manufactured by setting it to be 0 °. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 12 V was supplied to the surface light source to light the CCFL.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance 6820 cd / m ² (evaluation A) and the uniformity U were 82% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 46 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 1-2)
A surface light source was produced in the same manner as in Example 1-1 except that B-2 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the center luminance was 6950 cd / m ² (evaluation A), and the uniformity U was 81% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 30 ° in the vertical direction (Evaluation A) and 45 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 1-3)
A surface light source was produced in the same manner as in Example 1-1 except that B-3 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6690 cd / m ² (evaluation C), and the uniformity U was 85% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° (evaluation A) in the vertical direction and 47 ° (evaluation A) in the horizontal direction, and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 1-4)
A surface light source was produced in the same manner as in Example 1-1 except that B-4 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6510 cd / m ² (evaluation D) and the uniformity U was 83% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° (evaluation A) in the vertical direction and 47 ° (evaluation A) in the horizontal direction, and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 1-5)
A surface light source was produced in the same manner as in Example 1-1 except that C-2 was used as the second optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the center luminance was 6740 cd / m ² (evaluation B) and the uniformity U was 82% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 45 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were good ( (See Table 4).

(Example 1-6)
A surface light source was produced in the same manner as in Example 1-1 except that C-3 was used as the second optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance 6720 cd / m ² (evaluation B) and the uniformity U were 80% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 30 ° in the vertical direction (Evaluation A) and 44 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were good ( (See Table 4).

(Example 1-7)
A surface light source was produced in the same manner as in Example 1-1 except that C-4 was used as the second optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6505 d / m ² (evaluation D) and the uniformity U was 80% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 34 ° (evaluation A) in the vertical direction and 46 ° (evaluation A) in the horizontal direction, and it was found that the viewing angle characteristics were good ( (See Table 4).

(Example 1-8)
Using C-1 as the second optical film, the direction in which the anisotropic diffusion property of the first optical film is the largest and the length direction of the prism of the light diffusion film (2) are perpendicular (that is, θ6 = 90 °). A surface light source was produced in the same manner as in Example 1-1 except that the surface light source was arranged so as to be.

10 minutes after lighting, when the luminance of 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6500 cd / m ² (evaluation D) and the uniformity U was 75% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angles were 48 ° (evaluation A) in the vertical direction and 30 ° (evaluation A) in the horizontal direction, and good viewing angle characteristics were exhibited.

(Example 1-9)
Example 1 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 5 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6780 cd / m ² (evaluation B), and the uniformity U was 82% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° (evaluation A) in the vertical direction and 45 ° (evaluation A) in the horizontal direction, and good viewing angle characteristics were exhibited. (See Table 4)

(Example 1-10)
Example 1 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 10 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6670 cd / m ² (evaluation C) and the uniformity U was 81% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angles were 33 ° (evaluation A) in the vertical direction and 44 ° (evaluation A) in the horizontal direction, and good viewing angle characteristics were exhibited. (See Table 4)

(Example 2)
The light guide A-1 is installed so that the surface on which the linear groove is not formed is on the viewer side, one CCFL is disposed on each of the two light incident surfaces facing each other, and as a reflector around it, “Lumilar” E6SV (manufactured by Toray Industries, Inc.) was installed. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). C-1 is used as the second optical film on the optical film B-1, and the prism length direction and the direction in which the anisotropic diffusion property of the optical film B-1 is maximized are parallel (that is, θ6 = 0 °). The surface light source was produced by installing so that. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 12 V was supplied to the surface light source to light the CCFL.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the center luminance was 7350 cd / m ² (evaluation A) and the uniformity U was 82% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 30 ° in the vertical direction (Evaluation A) and 45 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 3)
The light guide A-3 is installed so that the surface on which the linear groove is not formed is on the viewer side, and 49 light emitting diodes (hereinafter referred to as LEDs) are arranged in parallel to the light incident surface, and the periphery thereof As a reflector, “Lumirror” E6SV (manufactured by Toray Industries, Inc.) was installed. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). C-1 is used as the second optical film on the optical film B-1, and the prism length direction and the direction in which the anisotropic diffusion property of the optical film B-1 is maximized are parallel (that is, θ6 = 0 °). The surface light source was produced by installing so that. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 15 V was supplied to the surface light source to light the LED.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 4320 cd / m ² (evaluation A) and the uniformity U was 82% (evaluation A). It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 30 ° (evaluation A) in the vertical direction and 46 ° (evaluation A) in the horizontal direction, and it was found that the viewing angle characteristics were excellent. (See Table 4).

(Example 4-1)
The light guide A-4 is installed so that the surface on which the linear groove is not formed is on the viewer side, three LEDs are arranged in parallel to the light incident surface, and “LUmirror” E6SV is used as a reflector around the LED. (Toray Industries, Inc.) was installed. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusibility is greatest and the direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). ). C-1 is used as the second optical film on the optical film B-1, and the prism length direction and the direction in which the anisotropic diffusion property of the optical film B-1 is maximized are parallel (that is, θ6 = 0 °). The surface light source was produced by installing so that. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

10 minutes after lighting, when measuring the 9-point luminance in the surface light source plane (see FIG. 18B), the central luminance 6470cd / m ² (evaluation A), the uniformity U is 82% (evaluation A), It was found that the center luminance and the uniformity U were excellent. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 45 ° in the horizontal direction (Evaluation A), and it was found that the viewing angle characteristics were excellent. (See Table 5).

(Examples 4-2 to 4-10)
A surface light source was produced by superimposing films similar to those in Examples 1-2 to 1-10 on the light guide in Example 4-1. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

  After 10 minutes of lighting, the 9-point luminance (see FIG. 18B) in the surface light source surface was measured, and it was found that both were excellent in the central luminance and the uniformity U. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, it was found that all showed good viewing angle characteristics (see Table 5).

(Example 5-1)
The light guide A-5 is installed so that the surface on which the linear groove is not formed is on the viewer side, two CCFLs are arranged on each of the two light incident surfaces facing each other, and as a reflector around it, “Lumilar” E6SV (manufactured by Toray Industries, Inc.) was installed. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusibility is greatest and the direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). ). A surface light source was produced by installing B-6 as a second optical film thereon. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 12 V was supplied to the surface light source to light the CCFL.

10 minutes after lighting, the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured. As a result, the central luminance 5510 cd / m ² and the uniformity U were 82%, and the central luminance and the uniformity U were excellent. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angle was 39 ° in the vertical direction and 41 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-2)
A surface light source was produced in the same manner as in Example 5-1, except that B-2 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18) was measured, it was found that the central luminance 5730 cd / m ² and the uniformity U were 81%, and the central luminance and the uniformity U were excellent. It was. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angle was 38 ° in the vertical direction and 40 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-3)
A surface light source was produced in the same manner as in Example 5-1, except that B-3 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5440 cd / m ² and the uniformity U was 84%, and the central luminance and the uniformity U were excellent. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angle was 39 ° in the vertical direction and 40 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-4)
A surface light source was produced in the same manner as in Example 5-1, except that B-4 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source surface (see FIG. 18A) was measured, the central luminance was 5300 cd / m ² and the uniformity U was 82%, which is excellent in the central luminance and the uniformity U. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angles were 40 ° in the vertical direction and 43 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-5)
A surface light source was produced in the same manner as in Example 5-1, except that B-7 was used as the second optical film. In addition, the optical film B-7 is installed so that the direction in which the anisotropic diffusibility is maximum and the direction in which the anisotropic diffusivity of the optical film B-1 is maximum are perpendicular (that is, θ6 = 0 °). did.

10 minutes after lighting, when the luminance at 25 points in the surface light source surface (see FIG. 18A) was measured, the central luminance was 5250 cd / m ² and the uniformity U was 85%, and the central luminance and the uniformity U were excellent. I understood it. In addition, when the distribution of the emission angle from the central portion of the light guide plate was measured, the viewing angle was 40 ° in the vertical direction and 42 ° in the horizontal direction, and it was found that good viewing angle characteristics were exhibited (see Table 6).

(Example 5-6)
A surface light source was produced in the same manner as in Example 5-1, except that B-8 was used as the second optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5370 cd / m ² and the uniformity U was 82%, and the central luminance and the uniformity U were excellent. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angles were 41 ° in the vertical direction and 43 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-7)
A surface light source was produced in the same manner as in Example 5-1, except that B-9 was used as the second optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5210 cd / m ² and the uniformity U was 83%, and the central luminance and the uniformity U were excellent. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angles were 42 ° in the vertical direction and 44 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 5-8)
Example 5 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 5 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5470 cd / m ² and the uniformity U was 82%, which is excellent in the central luminance and the uniformity U. I understood it. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angles were 40 ° in the vertical direction and 40 ° in the horizontal direction, and good viewing angle characteristics were shown. (See Table 6)

(Example 5-9)
Example 5 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 10 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when measuring the luminance at 25 points in the surface light source plane (see FIG. 18A), the central luminance is 5350 cd / m ² and the uniformity U is 81%, which is excellent in the central luminance and the uniformity U. I understood it. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angles were 40 ° in the vertical direction and 40 ° in the horizontal direction, and good viewing angle characteristics were shown. (See Table 6)

(Example 6)
The light guide A-6 is installed so that the surface on which the linear groove is not formed is on the viewer side, one CCFL is disposed on each of the two light incident surfaces facing each other, and as a reflector around it, “Lumilar” E6SV (manufactured by Toray Industries, Inc.) was installed. A reflective sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). A surface light source was produced by installing B-6 as a second optical film on the optical film B-1. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 12 V was supplied to the surface light source to light the CCFL.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5970 cd / m ² and the uniformity U was 82%, which is excellent in the central luminance and the uniformity U. I understood it. Further, when the distribution of the emission angle from the central portion of the light guide was measured, the viewing angle was 39 ° in the vertical direction and 41 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 7)
The light guide A-7 is installed so that the surface on which the linear groove is not formed is on the viewer side, 49 LEDs are arranged in parallel with the light incident surface, and “LUmirror” E6SV ( Toray Industries, Inc.) was installed. A reflection sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). A surface light source was produced by installing B-6 as a second optical film on the optical film B-1. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 15 V was supplied to the surface light source to light the LED.

10 minutes after lighting, when the luminance at 25 points in the surface light source surface (see FIG. 18A) was measured, the central luminance was 3450 cd / m ² and the uniformity U was 82%, which is excellent in the central luminance and the uniformity U. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angles were 40 ° in the vertical direction and 41 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 6).

(Example 8)
The light guide A-8 is installed so that the surface on which the linear groove is not formed is on the viewer side, three LEDs are arranged in parallel with the light incident surface, and “LUmirror” E6SV ( Toray Industries, Inc.) was installed. A reflective sheet “Lumirror” E6SL (manufactured by Toray Industries, Inc.) was installed on the non-observer side of the light guide 3. B-1 is used as the first optical film on the viewer side of the light guide 3, and the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide 3 are parallel (that is, θ5 = 0 °). A surface light source was produced by installing B-6 as a second optical film on the optical film B-1. Note that both the first optical film and (2) were installed such that the uneven surface was on the viewer side. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

After 10 minutes of lighting, the 9-point brightness (see FIG. 18B) in the surface light source surface was measured. As a result, the center brightness was 5340 cd / m ² and the uniformity U was 82%, and the center brightness and the uniformity U were excellent. I understood it. Further, when the emission angle distribution from the central portion of the surface light source was measured, the viewing angles were 39 ° in the vertical direction and 41 ° in the horizontal direction, and it was found that the viewing angle characteristics were good (see Table 7).

(Examples 8-2 to 8-9)
A surface light source was produced by stacking the same films as in Examples 5-2 to 5-10 on the light guide in Example 8-1. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

  After 10 minutes of lighting, the 9-point luminance (see FIG. 18B) in the surface light source surface was measured, and it was found that both were excellent in the central luminance and the uniformity U. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, it was found that all showed good viewing angle characteristics (see Table 7).

(Comparative Example 1-1)
A surface light source was produced in the same manner as in Example 1-1 except that B-5 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6210 cd / m ² and the uniformity U was 81%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 4).

(Comparative Example 1-2)
A surface light source was produced in the same manner as in Example 1-1 except that B-6 was used as the light turning angle film (1).

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6170 cd / m ² (evaluation E) and the uniformity U was 84% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° in the vertical direction (Evaluation A) and 45 ° in the lateral direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 1-3)
A surface light source was produced in the same manner as in Example 1-1 except that B-7 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5960 cd / m ² (evaluation E) and the uniformity U was 85% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 46 ° in the horizontal direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 1-4)
B-1 is arranged as the first optical film except that the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide are perpendicular (that is, θ5 = 90 °) Produced a surface light source in the same manner as in Example 1-1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5680 cd / m ² (evaluation E) and the uniformity U was 84% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° in the vertical direction (Evaluation A) and 47 ° in the lateral direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 1-5)
Except that B-2 is arranged as the first optical film so that the direction in which the anisotropic diffusibility is greatest and the length direction of the linear groove of the light guide are perpendicular (that is, θ5 = 90 °). Produced a surface light source in the same manner as in Example 1-1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6030 cd / m ² (evaluation E) and the uniformity U was 83% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 46 ° in the horizontal direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 1-6)
Except that B-3 was arranged as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide were perpendicular (that is, θ5 = 90 °). Produced a surface light source in the same manner as in Example 1-1.

10 minutes after lighting, the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured. As a result, the central luminance was 5790 cd / m ² (evaluation E) and the uniformity U was 85% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 32 ° in the vertical direction (Evaluation A) and 47 ° in the lateral direction (Evaluation A). It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 1-7)
Example 1 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 20 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 6490 cd / m ² (evaluation E) and the uniformity U was 80% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 35 ° in the vertical direction (Evaluation A) and 42 ° in the lateral direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low.

(Comparative Example 2)
A surface light source was produced in the same manner as in Example 2 except that B-5 was used as the first optical film.

10 minutes after lighting, the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured. As a result, the central luminance was 6710 cd / m ² (evaluation E) and the uniformity U was 84% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 46 ° in the horizontal direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 3)
A surface light source was produced in the same manner as in Example 3 except that B-5 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 3790 cd / m ² (evaluation E) and the uniformity U was 84% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 31 ° in the vertical direction (Evaluation A) and 46 ° in the horizontal direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained image was low. (See Table 4).

(Comparative Example 4-1)
A surface light source was produced in the same manner as in Example 4 except that B-5 was used as the first optical film.

After 10 minutes of lighting, the luminance of 9 points in the surface light source plane (see FIG. 18B) was measured. As a result, the center luminance was 5760 cd / m ² (evaluation E) and the uniformity U was 84% (evaluation A). . Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 30 ° in the vertical direction (Evaluation A) and 45 ° in the horizontal direction (Evaluation A), and good uniformity U and viewing angle characteristics were obtained. It was found that the center luminance of the obtained was low. (See Table 5).

(Comparative Examples 4-2 to 4-7)
A surface light source was produced by stacking the same film as Comparative Examples 1-2 to 1-7 on the light guide of Example 4-1. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

  10 minutes after lighting, when measuring the 9-point luminance in the surface light source surface (see FIG. 18B) and the emission angle distribution from the center of the surface light source, good uniformity U and viewing angle characteristics were obtained. The center brightness was found to be low. (See Table 5).

(Comparative Example 5-1)
A surface light source was produced in the same manner as in Example 5-1, except that B-6 was used as the first optical film.

10 minutes after lighting, when measuring the luminance at 25 points in the surface light source plane (see FIG. 18A), the central luminance was 5150 cd / m ² and the uniformity U was 85%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 42 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6)

(Comparative Example 5-2)
A surface light source was produced in the same manner as in Example 5-1, except that B-8 was used as the first optical film and B-8 was used as the second optical film.

  10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 4100 cd / m 2 and the uniformity U was 84%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 41 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6).

(Comparative Example 5-3)
A surface light source was produced in the same manner as in Example 5-1, except that B-9 was used as the first optical film and B-9 was used as the second optical film.

10 minutes after the lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 4350 cd / m ² , and the uniformity U was 84%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 42 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6).

(Comparative Example 5-4)
The same as Example 5-1 except that B-7 was arranged as the first optical film so that the direction with the largest anisotropic diffusibility and the length direction of the linear groove of the light guide were parallel to each other. Thus, a surface light source was produced.

10 minutes after the lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 4110 cd / m ² and the uniformity U was 81%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 42 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6).

(Comparative Example 5-5)
B-1 is arranged as the first optical film except that the direction in which the anisotropic diffusion property is the largest and the length direction of the linear groove of the light guide are perpendicular (that is, θ5 = 90 °) Produced a surface light source in the same manner as in Example 5-1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 3680 cd / m ² , and the uniformity degree U was 78%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 43 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6)

(Comparative Example 5-6)
Example 1 except that B-1 was installed as the first optical film so that the direction in which the anisotropic diffusibility was greatest and the length direction of the linear groove of the light guide 3 were θ5 = 20 °. A surface light source was produced in the same manner as in -1.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5170 cd / m ² and the uniformity U was 80%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 40 ° in the vertical direction and 40 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6)

(Comparative Example 6)
A surface light source was produced in the same manner as in Example 6 except that B-6 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 5510 cd / m ² and the uniformity U was 84%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 40 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 6)

(Comparative Example 7)
A surface light source was produced in the same manner as in Example 7 except that B-6 was used as the first optical film.

10 minutes after lighting, when the luminance at 25 points in the surface light source plane (see FIG. 18A) was measured, the central luminance was 2790 cd / m ² and the uniformity U was 84%. Further, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 42 ° in the vertical direction and 45 ° in the horizontal direction, and although good uniformity U and viewing angle characteristics were obtained, the central luminance was low. I understood it. (See Table 6)

(Comparative Example 8)
A surface light source was produced in the same manner as in Example 8 except that B-6 was used as the first optical film.

Ten minutes after lighting, the luminance at 9 points in the surface light source plane (see FIG. 18B) was measured. As a result, the central luminance was 4760 cd / m ² and the uniformity U was 84%. In addition, when the distribution of the emission angle from the central portion of the surface light source was measured, the viewing angle was 42 ° in the vertical direction and 45 ° in the horizontal direction, and the center luminance was low although good uniformity U and viewing angle characteristics were obtained. I understood. (See Table 7)

(Comparative Examples 8-2 to 8-7)
A surface light source was produced by superimposing films similar to Comparative Examples 8-2 to 8-7 on the light guide of Example 8-1. A power supply voltage of 3.3 V was supplied to the surface light source to light the LED.

  10 minutes after lighting, when measuring the 9-point luminance in the surface light source surface (see FIG. 18B) and the emission angle distribution from the center of the surface light source, good uniformity U and viewing angle characteristics were obtained. The center brightness was found to be low. (See Table 7).

  The results of the above Examples and Comparative Examples are shown in Tables 4-7. In each table, the type of the light source used, the type of the light guide used, the type of the first optical film, the relationship between the linear groove direction and the maximum diffusion direction of the first optical film, the second optical film The evaluation of the type, the relationship between the maximum diffusion direction of the first optical film and the prism length direction of the second optical film, the central luminance, the uniformity, and the viewing angle are shown.

From Table 4, Examples 1-1 to 1-10 of the configuration of the present invention using a 17-inch light guide A-1 and a prism sheet as the second optical film all have good central luminance, It can be seen that the uniformity and viewing angle characteristics are excellent. Further, Comparative Example 1-3 using the anisotropic diffusion sheet B-7 (Dmax / Dmin = 1.6) having a small anisotropic diffusibility also has a center luminance of a good uniformity U and viewing angle characteristics. Is low. In Comparative Examples 1-1, 1-2, 2, and 3 using isotropic diffusive sheets B-6 and B-6, the center luminance is low although good uniformity U and viewing angle characteristics are obtained. I understand that. Moreover, even if an anisotropic diffusive sheet is used, Comparative Examples 1-4, 1-5, 1-6, where the relationship between the light guide linear groove direction and the maximum diffusion direction of the first optical film is vertical, In Comparative Examples 1-7, which are not parallel, good centrality U and viewing angle characteristics are obtained, but the central luminance is low.

  From Table 5, even if it is a case where a small-sized light guide A-4 is used and a prism sheet is used as a 2nd optical film, Examples 1-1 to 1-10 of the structure of this invention, Examples 2 and 3 are all excellent in excellent center luminance, uniformity, and viewing angle characteristics. In particular, even when the relationship between the maximum diffusion direction of the first optical film and the prism length direction of the second optical film is at a right angle, the central luminance is slightly inferior (Evaluation D), but it can be seen that the device can be used. Further, it can be seen that Comparative Examples 4-1 and 4-2 using the isotropic diffusive sheets B-5 and B-6 have a low degree of central luminance although good uniformity U and viewing angle characteristics are obtained. In addition, Comparative Example 4-3 using the anisotropic diffusion sheet B-7 (Dmax / Dmin = 1.6) having a small anisotropic diffusibility also has a center luminance of a good uniformity U and viewing angle characteristics. Is low. Moreover, even if an anisotropic diffusive sheet is used, the comparative examples 4-4, 4-5, 4-6, in which the relationship between the light guide linear groove direction and the maximum diffusion direction of the first optical film is vertical, It can be seen that Comparative Example 4-7 which is not parallel and has good uniformity U and viewing angle characteristics, but the center luminance is low.

  From Table 6, even when a diffusion sheet is used as the second optical film, Examples 5-1 to 5-9 and Examples 6 and 7 of the configuration of the present invention have good center luminance, It can be seen that the uniformity and viewing angle characteristics are excellent. In addition, Comparative Examples 5-1, 5-2, and 5-3, and Comparative Examples 6 and 7 using isotropic diffusive sheets B-6, B-8, and B-9 have good uniformity U and viewing angle. It can be seen that the center luminance of the obtained characteristic is low. Further, in Comparative Example 5-4 using the anisotropic diffusion sheet B-7 (Dmax / Dmin = 1.6) having a small anisotropic diffusibility, the central luminance of the film having good uniformity U and viewing angle characteristics was obtained. Is low. Further, even when an anisotropic diffusive sheet is used, the relationship between the light guide linear groove direction and the maximum diffusion direction of the first optical film is vertical, and Comparative Example 5-5 is not parallel and Comparative Example 5-6 It can be seen that the center luminance is low although good uniformity U and viewing angle characteristics are obtained.

From Table 7, even if it is a case where a small-sized light guide is used and a diffusion sheet is used as the second optical film, Examples 8-1 to 8-9 having the configuration of the present invention are all good. It can be seen that the center luminance, uniformity, and viewing angle characteristics are excellent. Further, Comparative Examples 8-1, 8-2, and 8-3 using the isotropic diffusive sheets B-6, B-8, and B-9 had good uniformity U and viewing angle characteristics. It can be seen that the central luminance is low. Further, in Comparative Example 8-4 using the anisotropic diffusion sheet B-7 (Dmax / Dmin = 1.6) having a small anisotropic diffusibility, the central luminance of the film having good uniformity U and viewing angle characteristics was obtained. Is low. Moreover, even if an anisotropic diffusive sheet is used, the relationship between the light guide linear groove direction and the maximum diffusion direction of the first optical film is vertical, and Comparative Example 8-5 is not parallel and Comparative Example 8-6 is not parallel It can be seen that although the good uniformity U and viewing angle characteristics are obtained, the central luminance is low.

The surface light source of the present invention is superior to conventional surface light sources in terms of light utilization efficiency, high brightness, and wide viewing angle, and can be suitably used for applications in which a liquid crystal display element is irradiated from the back side. . Further, if the surface light source of the present invention is used, a high-brightness and clear liquid crystal display device can be obtained. Examples of the use include a mobile phone, an electronic notebook, a notebook PC, a monitor, and a TV.

Claims (16)

A light source, a light guide having at least one light incident surface facing the light source, and a light emitting surface substantially orthogonal to the light source, and a first optical film disposed facing the light emitting surface A surface light source,
In the light guide, a plurality of linear grooves or linear protrusions are provided substantially parallel to the light emitting surface or the light non-emitting surface on the back surface of the light emitting surface,
The first optical film has anisotropic diffusivity, and is arranged so that the direction in which the anisotropic diffusibility is maximum is substantially parallel to the longitudinal direction of the linear groove or linear protrusion, Surface light source.   2. The linear groove or the linear protrusion has at least one selected from the group consisting of a substantially arc shape, a substantially bell shape, a substantially triangular shape, and a substantially trapezoidal shape in cross section perpendicular to the longitudinal direction. The surface light source described in 1.   The surface light source according to claim 1, wherein the linear groove or the linear protrusion has a longitudinal direction substantially parallel to a light incident surface of the light guide.   The surface light source according to claim 1, wherein the linear groove or the linear protrusion is provided on a light non-emitting surface of the light guide.   The surface light source according to claim 1, wherein a second optical film is installed on the first optical film.   The first optical film has a half-value width D1max of transmitted light in a direction in which diffusivity is maximum when light is incident on the first optical film from a normal direction, and a direction in which diffusivity is minimum. The surface light source according to claim 1, wherein a ratio D1max / D1min to a half-value width D1min of transmitted light at 3 is 3 or more.   The surface light source according to claim 1, wherein the first optical film has a transmittance of 45% or more and a haze of 70% or more.   The surface light source according to claim 6, wherein the first optical film has a half-value width D1min of 10 ° or less.   The surface light source according to claim 5, wherein the second optical film is a prism sheet having an apex angle of 80 ° to 100 °.   The prism sheet is arranged such that its length (light guide) direction and the direction in which the diffusibility is maximized when light is incident on the first optical film from the normal direction are substantially parallel to each other. The surface light source according to claim 9.   An angle formed by a slope located on the light source side in the linear groove provided in the light guide and a straight line perpendicular to the light source 1, or a position on the opposite side of the light source in the linear protrusion provided in the light guide The surface light source according to claim 9, wherein an angle formed between the inclined surface and a straight line perpendicular to the light source 1 is 42.5 ° to 50 °.   The second optical film has a half-value width D2max of transmitted light in a direction in which the diffusivity is maximum when light is incident on the second optical film from the normal direction, and a direction in which the diffusivity is minimum. The surface light source according to claim 5, wherein a ratio D2max / D2min to a half-value width D2min of transmitted light at 5 is 5 or more.   The surface light source according to claim 12, wherein the second optical film has a transmittance of 50% or more and a haze of 70% or more.   The surface light source according to claim 12, wherein the second optical film has the half width D2min of 2 ° to 50 ° or less.   An angle formed by a slope located on the light source side in the linear groove provided in the light guide and a straight line perpendicular to the light source 1, or a position on the opposite side of the light source in the linear protrusion provided in the light guide The surface light source according to claim 12, wherein an angle formed between the inclined surface and a straight line perpendicular to the light source 1 is 20 ° to 42.5 °. A liquid crystal display device equipped with the surface light source according to claim 1.

Images