JP2009037984A - Lens sheet, surface light source, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a glare phenomenon in a liquid crystal display device; to restrain sticking between a prism sheet having a light diffusion layer and an optical member arranged adjacent to the prism sheet; and to reduce the occurrence of defects such as moire or a stringy appearance. <P>SOLUTION: In a lens sheet, a first surface 41 is set up to be a prism train formation surface, a second surface 42 is formed by the surface of the light diffusion layer 45, and the light diffusion layer 45 includes a light-transparent light diffusion material in a light-transparent resin. In the light diffusion layer 45, when a surface haze is HA1 and an internal haze is HA2, a ratio of the internal haze HA2 in the whole haze (HA1+HA2) is ≥20%. lens trains include first lens trains 411X having a first height H1, and second lens trains 411Y having a second height H2 lower than the first height H1. At least one of the second lens trains 411Y is arranged between the first lens trains 411X adjacent to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, a surface light source device used as a backlight of the liquid crystal display device, and a lens sheet constituting the surface light source device. In particular, the present invention reduces glare phenomenon called speckle or sparkling in image display of a liquid crystal display device without lowering brightness, further suppresses sticking, and reduces defects such as moire or streaky appearance. The present invention relates to a lens sheet, a surface light source device, and a liquid crystal display device.

  In recent years, color liquid crystal display devices have been widely used in various fields as image display means for portable notebook personal computers, desktop personal computer monitors, portable televisions or video integrated televisions. The liquid crystal display element (liquid crystal panel) used in this liquid crystal display device does not emit light by itself, but serves as an optical shutter. Thus, in order to improve the image display performance of the liquid crystal display device, a surface light source device called a backlight is arranged behind the liquid crystal panel, and the liquid crystal panel is illuminated from the back by the light emitted from the surface light source device. Is generally done.

  Such a backlight is, for example, a fluorescent tube as a primary light source, a light guide, as described in JP-A-2-84618 (Patent Document 1) and Japanese Utility Model Laid-Open No. 3-69184 (Patent Document 2). And a prism sheet as a light deflection element. Among these, the prism sheet is disposed on the light emitting surface of the light guide, and is for improving the optical efficiency of the backlight to improve the brightness. For example, one surface of the translucent sheet Is a lens sheet in which prism rows having an isosceles triangle cross section with apex angles of 60 ° to 100 ° are arranged in parallel at a pitch of 50 μm.

  As the prism sheet, as described in JP-A-6-324205 (patent document 3), JP-A-10-160914 (patent document 4) and JP-A 2000-353413 (patent document 5). In order to provide a function of a light diffusion sheet or a light diffusion film, it has been proposed to form a surface structure having a light diffusion function on the surface opposite to the surface on which the prism rows are formed. In the prism sheet of Patent Document 3, a projection group having a light diffusing function and a height not less than the wavelength of the light source light and not more than 100 μm is formed to improve the luminance of the surface light source device and reduce the luminance variation. In the prism sheet disclosed in Patent Document 4, the brightness of the surface light source device is increased and the viewing angle is increased by forming a light diffusion layer of a coating type, an embossed type, or a sandblast type. In the prism sheet of Patent Document 5, the luminance is improved and the viewing angle is expanded by applying a light diffusing fine particle layer such as transparent beads.

On the other hand, Japanese Patent Publication No. 11-501149 (Patent Document 6) describes that visible light coupling can be prevented by using prism rows of different heights formed on a prism sheet.
Japanese Patent Laid-Open No. 2-84618 Japanese Utility Model Publication No. 3-69184 JP-A-6-324205 JP-A-10-160914 JP 2000-353413 A Japanese National Patent Publication No. 11-501149

  As one of the functions of the surface structure having the light diffusion function of the prism sheet as described above, light is diffused by the respective protrusions, and desired haze (Haze) is expressed, so that the desired luminance and viewing angle can be obtained. Adjustments can be made. Another one of the functions of the surface structure having the light diffusion function of the prism sheet is due to partial close contact with the light diffusion sheet and the liquid crystal panel located on the upper surface of the prism sheet (surface opposite to the prism row forming surface). It is possible to suppress a phenomenon called sticking that generates interference fringes. As a further function of the surface structure having the light diffusion function of the prism sheet, the mat structure or lens formed on the light emitting surface of the light guide or the back surface on the opposite side can be reduced. Examples include so-called defect concealment, which reduces the visibility of surface structural defects such as a row arrangement structure. This defect concealment increases in importance especially when a high-intensity light source is used as the primary light source.

  Thus, when a surface structure having a light diffusing function is formed on the surface opposite to the prism row forming surface of the prism sheet, it has a very strong directivity emitted from the light guide and internally reflected by the prism row of the prism sheet. Light may interfere with the surface structure having a light diffusing function, and a glare phenomenon called speckle or sparkling may occur in which fine particles in the coating film and irregularities on the surface are extremely glazed. In this case, the display image is very difficult to see, and in recent years, there has been a strong demand for solving this glare phenomenon. The above Patent Documents 3 to 5 do not suggest a technical problem of eliminating or reducing such a glare phenomenon.

  In order to suppress the glare phenomenon due to the surface structure having the light diffusion function as described above, the light diffusibility is increased by increasing the amount of fine particles added to the coating film (light diffusion layer) forming the surface structure. It is conceivable to increase. As a result, the glare phenomenon can be reduced to some extent, but the luminance of the surface light source device or the liquid crystal display device is greatly reduced.

  In addition, when the prism sheet is used for a backlight of a liquid crystal display device that constitutes a portable electronic device such as a portable notebook computer or a portable television, it is caused by friction between the liquid crystal panel and the light diffusion layer due to vibration during carrying. There is a problem in that the light diffusing layer is damaged and the liquid crystal display device is defective.

  The surface on the light diffusion layer side of the liquid crystal panel takes various forms depending on the specifications of the liquid crystal display device. For example, those having a minute uneven structure formed for the purpose of anti-glare, smooth having no uneven structure, and having a polarization conversion film on the surface, such as DBEF manufactured by Sumitomo 3M Limited. Among these, when a micro uneven structure for anti-glare is formed, if the surface having the uneven structure and the light diffusing layer are in contact with each other and friction occurs, light diffusion is caused by the high hardness of the anti-glare micro uneven structure layer. The layer is likely to be damaged. On the other hand, when the surface of the liquid crystal panel is a smooth surface without unevenness or when it is composed of the surface of a polarization conversion film, there is a risk that the light diffusion layer may damage these surfaces. The light diffusion layer is required to prevent damage due to friction due to contact with various liquid crystal panel surfaces.

  On the other hand, in accordance with the recent demand for thinning of liquid crystal display devices and the accompanying thinning of surface light source devices, there is a demand for further thinning of the light guides constituting the surface light source devices. Further, a light guide having a wedge-shaped cross section is used in order to improve the light emission performance. In this case, the thickness in the vicinity of the end surface opposite to the light incident end surface on which the primary light source is opposed is particularly small. Therefore, depending on the use conditions such as long-term continuous use of the liquid crystal display device and the surface light source device or use in a high temperature environment, the light guide may be warped, and sticking may occur between the prism row forming surfaces of the prism sheet. , And may cause defects such as moire or streaky appearance.

  Accordingly, the present invention reduces a glare phenomenon in a liquid crystal display device without causing a significant decrease in luminance of the surface light source device or the liquid crystal display device, and a lens sheet such as a prism sheet having a light diffusing layer. An object of the present invention is to suppress sticking with adjacent optical members and reduce the occurrence of defects such as moire or streaky appearance in a surface light source device or a liquid crystal display device.

  Another object of the present invention is to reduce damage to the light diffusing layer of a lens sheet such as a prism sheet due to vibration when the liquid crystal display device is carried, and to prevent occurrence of defects in the surface light source device or the liquid crystal display device. is there.

  The first gist of the present invention is a sheet-like translucent member having a first surface and a second surface, and the first surface is a lens array forming surface formed by forming a plurality of lens arrays in parallel. The second surface is formed by a surface of a light diffusing layer, and the light diffusing layer is a lens sheet containing a light transmissive light diffusing material in a light transmissive resin, and the light diffusing layer has a surface When the haze is HA1 and the internal haze is HA2, the ratio of the internal haze HA2 to the total haze (HA1 + HA2) is 20% or more, and the lens array on the lens array forming surface has the first height. A plurality of first lens rows, and a plurality of second lens rows having a second height smaller than the first height, and at least one of the first lens rows adjacent to each other. A lens comprising a second lens array. It is over door.

  The second gist of the present invention is the lens sheet, wherein the total haze (HA1 + HA2) is 50 to 85%.

  The third gist of the present invention is characterized in that the surface of the light diffusion layer is an uneven surface, the average interval Sm between the unevenness is 150 μm or less, and the ten-point average roughness Rz is 4.0 μm or less. The lens sheet.

  The fourth gist of the present invention is that the translucent light diffusing material has an average particle diameter of 1 to 4 μm and a refractive index difference Δn1 with the translucent resin of 0.03 to 0.10. The refractive index difference Δn2 between the light-transmitting resin and the light-transmitting resin having an average particle diameter of 2 to 10 μm and a refractive index different from that of the first light-transmitting resin is 0.008 or more and 0.08. The lens sheet comprising the following second light transmissive light diffusing material.

  According to a fifth aspect of the present invention, the translucent resin is an acrylic resin, the first translucent light diffusing material is made of silicone resin fine particles, and the second translucent light diffusing material is an acrylic resin. The lens sheet is made of fine particles.

  The sixth gist of the present invention is the first translucent light diffusing material relative to the total amount of the first translucent light diffusing material and the second translucent light diffusing material added to the translucent resin. The lens sheet is characterized in that the ratio of the added amount (the first translucent light diffusing material addition ratio) is 20% by weight or more. If the addition ratio of the first light transmissive light diffusing material is reduced, there is a risk of coloring.

  The seventh gist of the present invention is that the translucent light diffusing material further has an average particle diameter of 5 to 30 μm and has a refractive index different from that of the first translucent light diffusing material. It is the said lens sheet | seat characterized by including.

  An eighth gist of the present invention is the lens sheet, wherein a convex part having a height of 3 to 25 μm is formed on the surface of the light diffusion layer by the third light transmissive light diffusing material. .

  The ninth gist of the present invention is the lens sheet, wherein the lens array is a prism array.

  A tenth aspect of the present invention is the lens sheet, wherein a difference between the first height and the second height is 0.5 to 2 μm.

  An eleventh aspect of the present invention is the lens sheet, wherein a distance between the tops of the first lens rows adjacent to each other is 20 to 1000 μm.

  A twelfth aspect of the present invention is a primary light source, a light guide that is guided by the light emitted from the primary light source, is guided and emitted, and is arranged so that the light emitted from the light guide is received. And the light guide includes a light incident end surface on which light emitted from the primary light source is incident and a light output surface from which the guided light is emitted, and the primary light source includes the light guide. A surface light source device, wherein the surface light source device is disposed adjacent to a light incident end surface of a light body, and the lens sheet is disposed such that the first surface faces a light emitting surface of the light guide. It is.

  A thirteenth aspect of the present invention includes the surface light source device and a liquid crystal panel arranged so that light emitted from a light diffusion layer of the lens sheet of the surface light source device is incident on the liquid crystal panel. A liquid crystal display device comprising an incident surface on which light emitted from a light diffusion layer of a sheet is incident and an observation surface on the opposite side.

  According to the present invention as described above, the ratio of the internal haze HA2 to the total haze (HA1 + HA2) of the light diffusion layer of the sheet-like translucent member of the lens sheet is 20% or more, and the sheet-like translucent light of the lens sheet is obtained. Since the lens array forming surface of the reflective member is formed by disposing at least one second lens array having a different height between adjacent first lens arrays, the luminance of the surface light source device or the liquid crystal display device Without reducing the glare phenomenon in the liquid crystal display device, suppressing sticking between the lens sheet and the optical member disposed adjacent thereto, and moire or in the surface light source device or the liquid crystal display device. The occurrence of defects such as streaky appearance can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a prism sheet as an embodiment of a lens sheet according to the present invention, an embodiment of a surface light source device according to the present invention using the prism sheet, and a liquid crystal display device according to the present invention using the surface light source device. FIG. 2 is a schematic perspective view showing an embodiment, and FIG. 2 is a schematic partial cross-sectional view thereof. In the present embodiment, the surface light source device includes a light guide 3 having at least one side end face as a light incident end face 31 and a light exit face 33 as one surface substantially orthogonal thereto, and the light guide 3. A linear primary light source 1 disposed facing the light incident end surface 31 and covered with the light source reflector 2, a prism sheet 4 as a light deflection element disposed on the light emitting surface of the light guide 3, and a light guide The light reflecting element 5 is disposed so as to face the back surface 34 opposite to the light emitting surface 33 of the body 3. In the present embodiment, the liquid crystal display device includes a surface light source device and a liquid crystal panel (liquid crystal display element) 8 disposed on the light exit surface 42 of the prism sheet 4.

  The light guide 3 is arranged in parallel with the XY plane and has a rectangular plate shape as a whole. The light guide 3 has four side end surfaces, and at least one of the pair of side end surfaces parallel to the YZ plane is a light incident end surface 31. The light incident end face 31 is disposed to face the primary light source 1, and the light emitted from the primary light source 1 enters the light incident end face 31 and is introduced into the light guide 3. In the present invention, for example, the light source may be disposed opposite to another side end face such as the side end face 32 opposite to the light incident end face 31.

  Two main surfaces that are substantially orthogonal to the light incident end surface 31 of the light guide 3 are respectively positioned substantially parallel to the XY plane, and one of the surfaces (the upper surface in the drawing) serves as the light emitting surface 33. By providing the light emitting surface 33 with a directional light emitting mechanism including a rough surface or a lens array, the light incident from the light emitting surface 33 is guided while the light incident from the light incident end surface 31 is guided through the light guide 3. Light having directivity is emitted in a plane (XZ plane) orthogonal to the end face 31 and the light emission face 33. The angle between the peak direction (peak light) of the emitted light luminous intensity distribution in the XZ in-plane distribution and the light emitting surface 33 is defined as α. The angle α is, for example, 10 to 40 degrees, and the full width at half maximum of the emitted light luminous intensity distribution is, for example, 10 to 40 degrees.

  The rough surface and the lens array formed on the surface of the light guide 3 have a luminance within the light emitting surface 33 that the average inclination angle θa according to ISO 4287 / 1-1984 is in the range of 0.5 to 15 degrees. It is preferable from the point of aiming at the degree of uniformity. The average inclination angle θa is more preferably in the range of 1 to 12 degrees, and more preferably in the range of 1.5 to 11 degrees. The average inclination angle θa is preferably set in an optimum range by a ratio (L / d) between the thickness (d) of the light guide 3 and the length (L) in the direction in which the incident light propagates. That is, when using a light guide 3 having an L / d of about 20 to 200, the average inclination angle θa is preferably 0.5 to 7.5 degrees, more preferably 1 to 5 degrees. It is a range, More preferably, it is the range of 1.5-4 degree | times. Further, when the light guide 3 having L / d of about 20 or less is used, the average inclination angle θa is preferably 7 to 12 degrees, and more preferably 8 to 11 degrees.

The average inclination angle θa of the rough surface formed on the light guide 3 is obtained in accordance with ISO 4287 / 1-1984 by measuring the rough surface shape using a stylus type surface roughness meter and setting the coordinate in the measurement direction as x. From the obtained slope function f (x), the following equations (1) and (2)
Δa = (1 / L) ∫ ₀ ^L | (d / dx) f (x) | dx (1)
θa = tan ⁻¹ (Δa) (2)
Can be obtained using Here, L is the measurement length, and Δa is the tangent of the average inclination angle θa.

  Further, the light guide 3 preferably has a light emission rate in the range of 0.5 to 5%, and more preferably in the range of 1 to 3%. By setting the light emission rate to 0.5% or more, the amount of light emitted from the light guide 3 is increased, and sufficient luminance tends to be obtained. Further, by setting the light emission rate to 5% or less, emission of a large amount of light in the vicinity of the primary light source 1 is prevented, attenuation of the emitted light in the X direction within the light emission surface 33 is reduced, and light emission is reduced. The brightness uniformity on the surface 33 tends to be improved. Thus, by setting the light emission rate of the light guide 3 to 0.5 to 5%, the angle of the peak light in the emission light intensity distribution (in the XZ plane) of the light emitted from the light emission surface is the same as that of the light emission surface. Directivity such that the full width at half maximum of the outgoing light intensity distribution (in the XZ plane) in XZ is in the range of 50 to 80 degrees with respect to the normal and perpendicular to both the light incident end face and the light outgoing face. Light having a high emission characteristic can be emitted from the light guide 3, the emission direction can be efficiently deflected by the prism sheet 4, and a surface light source device having high luminance can be provided.

In the present invention, the light emission rate from the light guide 3 is defined as follows. The relationship between the light intensity (I ₀ ) of the emitted light at the edge on the light incident end face 31 side of the light emitting face 33 and the emitted light intensity (I) at a distance L from the edge on the light incident end face 31 side is If the thickness (dimension in the Z direction) of the light guide 3 is d, the following formula (3)
I = I ₀ (α / 100) [1- (α / 100)] ^{L / d} (3)
Satisfying such a relationship. Here, the constant α is the light output rate, and the light guide 3 per unit length (length corresponding to the light guide thickness d) in the X direction orthogonal to the light incident end surface 31 on the light output surface 33. It is the ratio (percentage:%) at which the light is emitted from. The light emission rate α is obtained from the gradient by taking the logarithm of the light intensity of the light emitted from the light emission surface 23 on the vertical axis and (L / d) on the horizontal axis, and plotting these relationships. be able to.

  In the present invention, instead of forming the light emitting mechanism on the light emitting surface 33 as described above, or in combination with this, the light diffusing fine particles are mixed and dispersed in the light guide so as to emit directional light. A mechanism may be added.

  Moreover, in order to control the directivity in the surface (YZ surface) parallel to the primary light source 1 of the emitted light from the back surface 34 which is the main surface to which the directional light emitting mechanism is not provided, It is a prism row forming surface in which a large number of prism rows are arranged in a direction crossing the light incident end surface 31, more specifically in a direction substantially perpendicular to the light incident end surface 31 (X direction). The prism row on the back surface 34 of the light guide 3 can have an arrangement pitch in the range of, for example, 10 to 100 μm, and preferably in the range of 30 to 60 μm. Moreover, the prism row | line | column of the back surface 34 of this light guide 3 can make the apex angle into the range of 85-110 degree | times, for example. This is because the light emitted from the light guide 3 can be appropriately condensed by setting the apex angle within this range, and the luminance as the surface light source device can be improved. More preferably, it is the range of 90-100 degree | times.

  The light guide 3 is not limited to the shape shown in FIG. 1, and various shapes such as a rust shape with a thicker light incident end face can be used.

  The light guide 3 can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more. When forming a surface structure such as a rough surface of the light guide 3 or a surface structure such as a prism array or a lenticular lens array, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. Alternatively, the shape may be imparted simultaneously with molding by extrusion molding, injection molding, or the like. The structural surface can also be formed using heat or a photocurable resin. Furthermore, the surface of a transparent substrate such as a polyester resin, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or the like, or a rough surface made of an active energy ray curable resin is used. A structure or a lens array arrangement structure may be formed, or such a sheet may be bonded and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used.

  The prism sheet 4 is disposed on the light emitting surface 33 of the light guide 3. The prism sheet 4 is made of a sheet-like translucent member, and the two main surfaces, the first surface 41 and the second surface 42, are arranged in parallel to each other as a whole, and are respectively located in parallel with the XY plane. . The first surface 41 that is one main surface (the main surface that faces the light emitting surface 33 of the light guide 3) is a light incident surface, and the other main surface 42 is a light output surface. . The light incident surface 41 is a prism row forming surface in which a plurality of prism rows extending in the Y direction are arranged in parallel to each other. The light exit surface 42 is an uneven surface.

  FIG. 3 shows a schematic partial cross-sectional view of the prism sheet 4, and FIG. 4 shows a schematic partial enlarged cross-sectional view of the prism sheet 4 and the light guide 3. The prism sheet 4 includes a translucent base material 43, a translucent prism array forming layer 44 that is a translucent lens array forming layer, and a light diffusion layer 45. The prism row forming layer 44 includes a prism portion 44a and a relaxation layer 44b. The relaxation layer 44b is a layer having a uniform thickness between the prism portion 44a and the translucent substrate 43 and made of the same material as the prism portion 44a. The relaxation layer 44b relaxes the stress of the prism portion 44a when the resin is cured when the prism row forming layer 44 is formed on the lower surface of the translucent substrate 43, thereby preventing the surface of the prism portion from being deformed due to the occurrence of sink marks. To do. In FIG. 4, the distinction between the prism portion 44 a and the relaxation layer 44 b is not displayed. These translucent base material 43, prism row forming layer 44 and light diffusion layer 45 constitute a sheet-like translucent member. A first prism row 411 </ b> X and a second prism row 411 </ b> Y are formed on the lower surface of the prism row forming layer 44, and the lower surface forms the light incident surface 41. Each of the first and second prism rows 411X and 411Y may be simply referred to as a prism row 411 hereinafter. Further, the upper surface of the light diffusion layer 45 forms a light exit surface 42.

  The material of the translucent substrate 43 is preferably a material that transmits active energy rays such as ultraviolet rays and electron beams. As such a material, a flexible glass plate or the like can be used, but polyethylene terephthalate and polyethylene naphthalate can be used. Polyester resins such as phthalates, acrylic resins such as polymethyl methacrylate, cellulose resins such as diacetyl cellulose and triacetyl cellulose, styrene resins such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, cyclic or norbornene structures Transparent resins such as polyolefins and olefin resins such as ethylene / propylene copolymers, polyamide resins such as nylon and aromatic polyamide, polycarbonate resins, vinyl chloride resins, polymethacrylimide resins Sheet or film is preferred.

  The thickness of the translucent substrate 43 is preferably, for example, 10 to 500 μm, more preferably 20 to 400 μm, and particularly preferably 30 to 300 μm from the viewpoint of workability such as strength and handleability. In addition, in order to improve the adhesiveness between the prism array forming layer 44 made of the active energy ray-curable resin and the transparent base material 43, the surface of the light-transmitting base material 43 is adhesive such as anchor coating treatment. What performed the improvement process is preferable.

  The upper surface of the prism row forming layer 44, that is, the upper surface of the relaxing layer 44 b is a flat surface, and is joined to the lower surface of the translucent substrate 43. The lower surface of the prism array forming layer 44, that is, the light incident surface 41 is a prism array forming surface formed by the surface of the prism portion 44a, and includes a plurality of first prism arrays 411X and a plurality of first prism arrays 411X extending in the Y direction. Two prism rows 411Y are arranged in parallel to each other. The thickness of the prism row forming layer 44 is, for example, 10 to 500 μm. The arrangement pitch P of the prism rows 411 when the first prism row 411X and the second prism row 411Y are not distinguished is, for example, 10 to 500 μm.

  The first prism row 411X has a first height H1, and the second prism row 411Y has a second height H2 that is smaller than H1. The difference ΔH between the first height H1 and the second height H2 is preferably 0.5 to 2 μm. When the height difference ΔH is within this range, the sticking between the top of the prism row 411 and the light emitting surface 33 of the light guide 3 is sufficiently suppressed, and moire or Generation of defects such as streaky appearance can be effectively reduced.

  Four second prism rows 411Y are arranged between the first prism rows 411X adjacent to each other. In the present invention, the number of the second prism rows 411Y disposed between the first prism rows 411X adjacent to each other is not limited to four, and it is sufficient that there is at least one, and the upper limit number thereof is For example, 20, preferably 10.

  FIG. 5 shows an embodiment in which two second prism rows 411Y are arranged between the first prism rows 411X adjacent to each other. FIG. 6 shows an embodiment in which five prism rows 411Y and four prism rows 411Z are alternately arranged between the first prism rows 411X adjacent to each other. . The prism row 411Z has a smaller height than the prism row 411Y, but both are included in the second prism row. For example, the height of the prism row 411Y can be 0.5 μm smaller than the height of the first prism row 411X, and the height of the prism row 411Z can be 0.5 μm smaller than the height of the prism row 411Y.

  The distance S between the tops of the first prism rows 411X adjacent to each other is preferably 20 to 1000 μm. When the distance S is within this range, sticking between the top of the prism row 411 and the light emitting surface 33 of the light guide 3 is sufficiently suppressed, and moire or streak-like appearance in the surface light source device or the liquid crystal display device is achieved. The occurrence of such defects can be effectively reduced.

  As shown in FIG. 4, the prism row 411 includes two prism surfaces 411a and 411b. These prism surfaces may be optically sufficiently smooth surfaces (mirror surfaces) or rough surfaces. In the present invention, the prism surface is preferably a mirror surface from the viewpoint of maintaining desired optical characteristics by the prism sheet. The apex angle θ of the prism row 411 is preferably in the range of 40 to 150 °. In general, in a backlight of a liquid crystal display device, when the prism sheet is disposed so that the prism row forming surface faces the liquid crystal panel, the apex angle θ of the prism row is in the range of about 80 to 100 °. Preferably it is the range of 85-95 degrees. On the other hand, when the prism sheet 4 is arranged so that the prism row forming surface faces the light guide 3 as in the above embodiment, the apex angle θ of the prism row 411 is in the range of about 40 to 75 °, Preferably it is the range of 45-70 degrees.

  The apex angle θ of the prism row 411 is preferably the same for both the first and second prism rows. Thereby, the mold member used for the transfer formation of the prism array forming surface can be easily manufactured only by appropriately changing the cutting depth and the moving pitch distance using the same cutting tool.

  The prism array forming layer 44 is made of, for example, an active energy ray curable resin, and preferably has a high refractive index from the viewpoint of improving the luminance of the surface light source device. Specifically, the refractive index is 1.55. More preferably, it is 1.6 or more. The active energy ray curable resin for forming the prism row forming layer 44 is not particularly limited as long as it is cured with active energy rays such as ultraviolet rays and electron beams. For example, polyesters, epoxy resins , (Meth) acrylate resins such as polyester (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate. Among these, (meth) acrylate resins are particularly preferable from the viewpoint of optical characteristics and the like. As the active energy ray-curable composition used for such a cured resin, a polyvalent acrylate and / or a polyvalent methacrylate (hereinafter referred to as a polyvalent (meth) acrylate) in terms of handleability and curability. , Monoacrylate and / or monomethacrylate (hereinafter referred to as mono (meth) acrylate), and a photopolymerization initiator by active energy rays are preferred. Typical polyvalent (meth) acrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These are used alone or as a mixture of two or more. Examples of mono (meth) acrylates include mono (meth) acrylates of monoalcohols and mono (meth) acrylates of polyols.

  On the other hand, the light diffusing layer 45 includes a plurality of first light transmissive light diffusing materials 452 and second light transmissive light diffusing materials 454 in a light transmissive resin 451, and forms a light transmissive layer. The first light transmissive light diffusing material light diffusing material 452 and the second light transmissive light diffusing material 454 protrude from the surface of the light-transmitting resin 451, so that the surface of the light diffusing layer 45 is formed in an uneven surface.

  The difference Δn1 between the refractive index N2 of the first translucent light diffusing material 452 and the refractive index N1 of the translucent resin 451 is an internal scattering due to the refractive index difference at the interface between the light diffusing material 452 and the translucent resin 451. Is preferably 0.03 or more and 0.10 or less, more preferably 0.04 or more and 0.04 or less, in order to suppress speckle phenomenon and suppress unnecessary scattering at the interface to suppress a decrease in luminance. 09 or less is more preferable, and 0.05 or more and 0.08 or less are particularly preferable.

  The refractive index N3 of the second light transmissive light diffusing material 454 is preferably different from the refractive index N2 of the first light transmissive light diffusing material 452. The second light transmissive light diffusing material 454 has a function of generating surface scattering at the interface between the light diffusing layer 45 and air by forming a convex portion on the surface of the light diffusing layer 45 based on the second light transmissive light diffusing material 454. It is higher than the light diffusing material 452. Therefore, the difference Δn2 between the refractive index N3 of the second light transmissive light diffusing material 454 and the refractive index N1 of the light transmissive resin 451 is preferably 0.00 or more and 0.08 or less, and 0.00 or more and 0.07. The following is more preferable.

  The light diffusing layer 45 may further contain a third light transmissive light diffusing material 455 as necessary. The refractive index N4 of the third light transmissive light diffusing material 455 is preferably different from the refractive index N2 of the first light transmissive light diffusing material 452. The third light transmissive light diffusing material 455 has a function of generating surface scattering at the interface between the light diffusing layer 45 and air by forming a convex portion on the surface of the light diffusing layer 45 based on the third light transmissive light diffusing material 455. It is higher than the light diffusing material 452. Therefore, the difference Δn3 between the refractive index N4 of the third translucent light diffusing material 455 and the refractive index N1 of the translucent resin 451 is preferably 0.00 or more and 0.08 or less, and 0.00 or more and 0.07. The following is more preferable.

  A convex portion having a height of 3 to 25 μm is preferably formed on the surface of the light diffusion layer 45 based on the third light transmissive light diffusing material 455. Such a concavo-convex structure having convex portions can reduce the contact area between the liquid crystal panel and the light diffusing layer 455, and can reduce the visible damage due to friction between the liquid crystal panel and the light diffusing layer. This structure can be suitably used even when the abrasion resistance of the light diffusing layer 45 due to vibration is highly required, such as a backlight for a liquid crystal display device that is assumed to be carried.

  In this case, since a steep slope of the surface that causes total reflection described later may occur, the addition amount of the third translucent light diffusing material 455 is reduced so as to reduce the luminance of the surface light source device as much as possible. It is preferable to do this.

  When the surface haze based on the light diffusion due to the surface uneven structure of the light diffusion layer 45 is HA1, and the internal haze based on the internal refractive index distribution of the light diffusion layer 45 is HA2, the internal haze HA2 occupying the total haze (HA1 + HA2) The ratio is preferably 20% or more. This is because the occurrence of glare can be suppressed by increasing the internal diffusion ratio as well as the surface diffusion and increasing the spatial mixing of the diffused light by diffusing the light inside the light diffusion layer 45. is there. The ratio of the internal haze HA2 to the total haze (HA1 + HA2) is more preferably 40% or more, and particularly preferably 50% or more. The ratio of the internal haze HA2 to the total haze (HA1 + HA2) is preferably 95% or less, more preferably 90% or less.

  The average particle diameter of the first light transmissive light diffusing material 452 is preferably 1 to 4 μm, more preferably 1.5 to 3.8 μm, and particularly preferably 2.0 to 3.5 μm. When the average particle diameter of the first light transmissive light diffusing material 452 is smaller than 1 μm, the light beam that has passed through the light diffusing layer 45 is colored to reduce the color temperature of the surface light source device, or to reduce the defect concealing property. When the average particle diameter of the first light transmissive light diffusing material 452 is larger than 4 μm, the glare phenomenon tends to occur strongly.

  The average particle diameter of the second light transmissive light diffusing material 454 is preferably 2.0 to 10.0 μm, more preferably 2.5 to 9.0 μm, and particularly preferably 3.0 to 8.0 μm. When the average particle diameter of the second light transmissive light diffusing material 454 is smaller than 2 μm, the convex portion formation on the surface of the light diffusing layer 45 becomes insufficient, and the ratio of internal haze increases, so that the luminance decreases. Defect concealment may be reduced, and when the average particle diameter of the second light transmissive light diffusing material 454 is larger than 10 μm, the glare phenomenon tends to occur strongly.

  Further, by including the light diffusing materials 452 and 454 having two different average particle diameters, the unevenness height of the surface of the light diffusing layer 45 becomes uneven depending on the location, and the surface of the light diffusing layer 45 The presence position of both becomes random, and the effect that the film external appearance becomes favorable is produced. On the other hand, even if the average particle diameter of both is the same, the same effect can be exhibited if the type (refractive index or material) of the light diffusing material used is different.

  The average particle diameter of the third light transmissive light diffusing material 455 is preferably 5 to 30 μm, more preferably 8 to 20 μm, and still more preferably 9 to 13 μm. When the average particle diameter of the third light transmissive light diffusing material 455 is less than 5 μm, sufficient convex portions are not formed, and the wear resistance is not sufficiently improved. On the other hand, when the average particle size is larger than 30 μm, the effect of improving glare and unevenness of the liquid crystal display device is not sufficient.

  The particle size distribution of the third light transmissive light diffusing material 455 is preferably narrow. That is, when the particle size distribution is wide, when the light diffusion layer 45 comes into contact with the liquid crystal panel surface, stress concentrates on the tips of a small number of large particles in the third light transmissive light diffusing material 455, causing damage to the particles and liquid crystal panel surface. This is because the damage of the metal tends to increase. For this reason, the standard deviation in the weight distribution of the particle diameter of the third light transmissive light diffusing material 455 is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2 μm or less.

  When the third light transmissive light diffusing material 455 is contained, the difference between the average particle size of the second light transmissive light diffusing material 454 and the average particle size of the third light transmissive light diffusing material 455 is 1 μm or more. Is more preferably 3 μm or more, and particularly preferably 5 μm or more. By using a combination of light diffusing materials with such particle sizes, when the liquid crystal panel surface has a micro uneven structure, the contact between the uneven tip and the surface of the light diffusing layer can be reduced, improving wear resistance. To do.

  The formation method in particular of the light-diffusion layer 45 is not restrict | limited, A suitable system can be employ | adopted. For example, a light-transmitting resin 451 is dissolved in a solvent, and light diffusing materials 452 and 454 and further 455 are added to the solvent to prepare a dope (coating liquid or paint). By applying this dope to the surface of the translucent substrate 43 and drying it to remove the solvent, irregularities due to the light diffusing materials 452 and 454 and 455 are formed on the surface. The shape of the unevenness can be easily adjusted by the content of the translucent resin in the dope, the coating amount, the light diffusing materials 452 and 454, and the average particle diameter of 455. In order to develop the necessary haze, the height of the unevenness can be appropriately adjusted. In addition, the shape of the unevenness to be formed is determined from the shapes of the light diffusing materials 452 and 454 and 455. For example, when a spherical light diffusing material is used, it is like an aggregate of fine concave and convex lenses. Become a shape. If the height of the unevenness is too high, the angle formed with respect to the surface of the light transmissive substrate 43 in a part of the surface of the light diffusion layer 45 exceeds the critical angle of incident light from the light transmissive substrate. It is easy to become. In this case, the light is totally reflected at a part of the emission surface of the light diffusing layer 45 and becomes lost light, which decreases the luminance of the surface light source device. For this reason, it is preferable that the height of the unevenness of the light diffusion layer 45 is set to a height that does not cause a steep slope of the surface that causes total reflection as described above.

  Examples of the solvent used for preparing the dope include general solvents such as toluene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, isopropyl alcohol, and ethanol. Examples of the dope coating method include a coating method using a gravure coat, a lip coat, a comma coater, a roll coater or the like.

  As the translucent resin 451, a light diffusing material 452 and 454 and further 455 can be dispersed, and any transparent resin having sufficient strength can be used without particular limitation. Such translucent resins include polyamide resins, polyurethane resins, polyester resins, acrylic resins and other thermoplastic resins, thermosetting resins, active energy ray curable resins (ionizing radiation curable resins), etc. Among these, it is preferable to select appropriately in consideration of the adhesiveness with the translucent base material 43, the light diffusing materials 452 and 454, and further 455, and the use of an acrylic resin having a high transmittance is preferable. Particularly preferred.

  As the acrylic resin, polymers such as hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, and acrylic acid are preferable. In particular, acrylic polyol containing hydroxyalkyl (meth) acrylate as a monomer unit is dissolved in a solvent such as toluene or methyl ethyl ketone, and mixed with an oligomerized isocyanate such as isocyanate or isocyanurate, or a crosslinking agent such as melamine. An acrylic resin obtained by curing is preferable in terms of strength and adhesion to a translucent substrate. In view of the good dispersibility of the silicone resin fine particles, it is preferable to contain an acrylic alkylate as a copolymer component of the acrylic polyol.

  Moreover, as translucent resin 451, that whose glass transition point is 60 degreeC or more is preferable from a heat resistant viewpoint.

  Note that a leveling agent, a thixotropic agent, a slip agent, an antifoaming agent, an antistatic agent, an ultraviolet absorber, and the like can be added and contained in the translucent resin 451. Among these, by incorporating a leveling agent, aggregation of the light diffusing materials 452 and 454 can be suppressed, and unevenness due to the light diffusing materials 452 and 454 and 455 can be easily formed.

  Moreover, the damage at the time of friction with the liquid crystal panel surface can be prevented by adding a slip agent. As the slip agent, commercially available products such as silicon-based, fluorine-based, paraffin-based, and mixtures thereof can be used without particular limitation, and examples thereof include BYK series manufactured by Big Chemie Japan Co., Ltd.

  Examples of the light diffusing materials 452 and 454 and 455 include inorganic fine particles such as silica, alumina and glass, crosslinked organic fine particles such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine and melamine, and silicone. Resin fine particles can be appropriately selected and used. The light diffusing materials 452 and 454 may be used in any shape such as a sphere, an indeterminate shape, a bowl shape, a spheroid, or a needle shape. Further, the shape of the light diffusing material 455 is preferably a spherical shape in order to reduce friction with the liquid crystal panel surface.

  In order to cope with various types of liquid crystal panel surfaces, the light diffusing material 455 preferably has an appropriate hardness. When the hardness is not sufficient, when the liquid crystal panel surface has a micro uneven structure for anti-glare, the particles may be scraped and cannot play the role of reducing the contact area. On the other hand, if the particles are too hard, the liquid crystal panel surface may be damaged. This is because there are things to give.

  As an example of the light diffusing material 455 having an appropriate hardness, polymethyl methacrylate crosslinked particles containing 20 to 50% of a crosslinking agent can be mentioned. Examples of commercially available products include Sekisui Chemical Co., Ltd. techpolymer development products XX-series. Among these, XX-38B, XX-39B, and XX-71B containing 30% of a crosslinking agent are particularly preferable.

  As the light diffusing material 455, a material having rubber elasticity can also be suitably used for exhibiting wear resistance. This is effective in preventing damage to the surface of the liquid crystal panel, particularly when the surface of the liquid crystal panel is a smooth surface. For example, silicone composite powder KMP-600 series manufactured by Shin-Etsu Chemical Co., Ltd., Techpolymer BMX series, ARX series manufactured by Sekisui Plastics Co., Ltd. may be mentioned.

As the addition amount of the third light transmissive light diffusing material 455, the weight per unit area in the light diffusing layer 45 is preferably 0.001 to 1 g / m ² , more preferably 0.005 to 0.5 g. / M ² , and 0.01 to 0.3 g / m ² is particularly preferable. When it is less than 0.001 g / m ² , the number of convex portions based on the third light transmissive light diffusing material 455 is too small, and the surface of the liquid crystal panel is easily damaged due to the concentration of stress. On the other hand, when it exceeds 1 g / m ² , the steep slope of the surface that causes total reflection increases and the luminance tends to decrease.

  The contents of the first light transmissive light diffusing material 452 and the second light transmissive light diffusing material 454 in the light diffusing layer 45 are the same as the first light transmissive light diffusing material 452 and the second light transmissive light in the light transmissive resin. The addition amount of the first light transmissive light diffusing material 452 is preferably 20% by weight or more, more preferably 50% by weight or more, and still more preferably with respect to the total amount of the light diffusing material 454 added. Is 55% by weight or more, particularly preferably 60% by weight or more. Thereby, the ratio of the internal haze HA2 to the total haze (HA1 + HA2) of the light diffusion layer 45 is set to 20% or more, and it becomes easy to eliminate the glare phenomenon.

  The addition amount of the first light transmissive light diffusing material 452 and the second light transmissive light diffusing material 454 to the light transmissive resin 451 is such that the total haze (HA1 + HA2) of the light diffusing layer 45 is 50 to 85%, and the inside The haze HA2 ratio is preferably determined to be 20% or more. For this reason, the addition amount of the first light transmissive light diffusing material 452 is generally preferably 10 to 20% by weight with respect to the light transmissive resin 451. Similarly, the addition amount of the second light transmissive light diffusing material 454 is preferably 5 to 15% by weight with respect to the light transmissive resin 451. If the content of the light diffusing materials 452 and 454 is less than the above-mentioned amount, the total haze (HA1 + HA2) of the light diffusing layer 45 tends to be lower than 50%, and the viewing angle of the surface light source device tends to be reduced. When the contents of the materials 452 and 454 are larger than the above-mentioned amounts, the total haze (HA1 + HA2) exceeds 85% and the luminance of the surface light source device tends to be lowered.

  The uneven surface of the light diffusion layer 45 is formed such that the average interval (average length of contour curve elements) Sm defined by JIS B 0601-1994 is 150 μm or less, and more preferably 120 μm or less. And more preferably 100 μm or less, particularly preferably 80 μm or less. The uneven surface of the light diffusion layer 45 is formed so that the ten-point average roughness Rz defined in JIS B 0601-1994 is 4.0 μm or less, more preferably 3.5 μm or less. More preferably, it is formed to be 3.0 μm or less. From the viewpoint of preventing sticking with the liquid crystal panel, Rz is 0.5 μm or more, preferably 1.0 μm or more. Forming the uneven surface of the light diffusion layer 45 in this way is particularly important in order to suppress the glare phenomenon.

  A plurality of fine particles such as the light diffusing materials 452 and 454 may aggregate and aggregate in the coating liquid to form secondary particles 453. This aggregation is caused by differences in affinity due to differences in SP values (solubility parameters) between the light diffusing materials 452 and 454, the translucent resin 451, and the solvent, the surface potential of the light diffusing materials 452 and 454, and the doping during coating. It varies depending on the level of viscosity, the length of the leveling time (time from coating to drying), the presence or absence of a leveling agent, and the like. The average spacing Sm between the uneven surfaces tends to increase as the aggregation in the in-plane direction of the coating film becomes significant. Further, the ten-point average roughness Rz of the concavo-convex surface tends to increase when the aggregation in the coating thickness direction becomes significant.

  In addition, in a circular region having a radius of 70 μm at an arbitrary position of the light diffusion layer 45, the number of secondary particles 453 having a major axis of 30 μm or more is 3 or less, preferably 2 or less, and more preferably 1 or less. It is desirable to suppress the glare phenomenon. More preferably, the major axis of 20 μm or less is in the above number range. As shown in the plan view of FIG. 7, the planar shape of the secondary particles 453 formed by aggregating a plurality of light diffusing materials 452 and 454 (illustrated by 452 in the figure) is generally not circular. Therefore, the size of the secondary particles 453 is represented by the major axis D.

  When the aggregated secondary particles are regarded as primary particles, this is the same as the addition of very large particles, and it is very important to suppress aggregation for the reasons described above.

  In the above embodiment, the light diffusing layer 45 is formed by applying a dope containing the translucent resin 451 and the light diffusing materials 452 and 454 and 455, and the added amount of the light diffusing materials 452 and 454 and 455 Therefore, it is possible to easily adjust the haze of the light diffusion layer 45, and it is possible to easily adjust the performance such as the luminance and the viewing angle of the surface light source device.

  However, in the present invention, the light diffusion layer having an uneven surface can be formed by other methods. For example, the uneven surface can be formed by subjecting the surface of the translucent base material to a roughening treatment in advance using chemical etching, sandblasting, embossing roll, or the like. In addition, a coating film made of a light-transmitting resin is separately applied on the light-transmitting substrate, and a concavo-convex structure is imparted to the surface of the light-transmitting resin film formed by using a transfer method using a mold. You may do it. Two or more of the above methods may be combined to form a concavo-convex surface having different concavo-convex structures. The ratio of the internal haze HA2 in the total haze can be arbitrarily controlled by adding a light diffusing material as described above to the resin forming these uneven surfaces.

  As described above, the prism sheet 4 has been described as having the prism row forming layer 44 separately from the translucent base material 43. However, in the present invention, the translucent base material 43 and the prism row forming layer 44 are shared. It can consist of members. That is, a prism row can be formed on the surface of the translucent substrate 43. In this case, the translucent base material 43 can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more.

  FIG. 4 schematically shows the state of light deflection in the XZ plane by the prism sheet 4. This figure shows an example of the traveling direction of peak light (light corresponding to the peak of the outgoing light distribution) from the light guide 3 in the XZ plane. Most of the peak light obliquely emitted from the light emitting surface 33 of the light guide 3 at an angle α is incident on the first prism surface 411a of the prism row 411 and is almost totally reflected by the second prism surface 411b. The light travels substantially in the direction of the normal line of the light exit surface 42 and is diffused and emitted mainly by the surface of the uneven structure of the light diffusion layer 45. Further, in the YZ plane, there is also the action of the prism rows on the light guide back surface 34 as described above, so that the luminance in the normal direction of the light exit surface 42 can be sufficiently improved in a wide range.

  Note that the shape of the prism surfaces 411a and 411b of the prism row 411 of the prism sheet 4 is not limited to a single plane, and can be, for example, a convex polygonal shape or a convex curved surface shape. A narrow field of view can be achieved.

  In the prism sheet 4, the prism array is formed for the purpose of accurately producing a desired prism array shape, obtaining stable optical performance, and suppressing wear and deformation of the top of the prism array during assembly work or use of the light source device. A top flat portion or a top curved surface portion may be formed on the top of the top. In this case, the width of the top flat part or the top curved surface part is preferably 3 μm or less from the viewpoint of suppressing the occurrence of uneven brightness patterns due to the decrease in brightness and the sticking phenomenon as the surface light source device, and more preferably The width of the top flat portion or the top curved surface portion is 2 μm or less, more preferably 1 μm or less.

  The formation of the prism rows as described above is performed on the surface of the synthetic resin sheet by using a mold member having a shape transfer surface for transferring and forming the light incident surface 41 including the prism row forming surface having the prism rows 411. This can be realized.

  FIG. 8 is a schematic diagram showing an embodiment of forming a prism row in the prism sheet.

  In FIG. 8, reference numeral 7 denotes a mold member (roll type) formed by forming a shape transfer surface for transferring and forming the light incident surface 41 on a cylindrical outer peripheral surface. This roll type | mold 7 shall consist of metals, such as aluminum, brass, and steel. FIG. 9 is a schematic perspective view of the roll mold 7. A shape transfer surface 18 is formed on the outer peripheral surface of the cylindrical roll 16. FIG. 10 is a schematic exploded perspective view showing a modified example of the roll mold 7. In this modification, a thin plate-shaped mold member 15 is wound around and fixed to the outer peripheral surface of the cylindrical roll 16. The thin plate-shaped member 15 has a shape transfer surface formed on the outer surface.

  As shown in FIG. 8, the roll mold 7 is supplied with a translucent substrate 9 (43) along its outer peripheral surface, that is, the shape transfer surface. 9, the active energy ray-curable composition 10 is continuously supplied from the resin tank 12 through the nozzle 13. A nip roll 28 for making the thickness of the supplied active energy ray-curable composition 10 uniform is provided outside the translucent substrate 9. As the nip roll 28, a metal roll, a rubber roll, or the like is used. Moreover, in order to make the thickness of the active energy ray-curable composition 10 uniform, the nip roll 28 is preferably processed with high accuracy with respect to roundness, surface roughness, etc. In the case of a rubber roll A rubber having a high hardness of 60 degrees or more is preferable. The nip roll 28 is required to accurately adjust the thickness of the active energy ray-curable composition 10 and is operated by the pressure mechanism 11. As the pressure mechanism 11, a hydraulic cylinder, a pneumatic cylinder, various screw mechanisms, and the like can be used, but a pneumatic cylinder is preferable from the viewpoint of simplicity of the mechanism. The air pressure is controlled by a pressure regulating valve or the like.

  The active energy ray-curable composition 10 supplied between the roll mold 7 and the translucent substrate 9 is preferably maintained at a constant viscosity in order to keep the thickness of the obtained prism portion constant. In general, the viscosity range is preferably in the range of 20 to 3000 mPa · S, and more preferably in the range of 100 to 1000 mPa · S. By setting the viscosity of the active energy ray-curable composition 10 to 20 mPa · S or more, it is necessary to set the nip pressure extremely low or extremely increase the molding speed in order to make the prism portion constant in thickness. Disappear. If the nip pressure is extremely low, the pressure mechanism 11 tends to be unable to operate stably, and the thickness of the prism portion is not constant. On the other hand, when the molding speed is extremely increased, the irradiation amount of the active energy ray is insufficient, and the curing of the active energy ray curable composition tends to be insufficient. On the other hand, by setting the viscosity of the active energy ray-curable composition 10 to 3000 mPa · S or less, the curable composition 10 can be sufficiently distributed to the details of the roll-shaped shape transfer surface structure, and the accuracy of the lens shape is improved. Transfer is difficult, defects due to mixing of bubbles are not easily generated, and productivity is not deteriorated due to an extremely low molding speed. For this reason, in order to keep the viscosity of the active energy ray-curable composition 10 constant, a sheathed heater, a hot water jacket, or the like is provided outside or inside the resin tank 12 so that the temperature of the curable composition 10 can be controlled. It is preferable to install a heat source facility.

After supplying the active energy ray-curable composition 10 between the roll mold 7 and the translucent substrate 9, the active energy beam curable composition 10 is interposed between the roll mold 7 and the translucent substrate 9. In the sandwiched state, the active energy ray irradiating device 14 irradiates the active energy ray through the translucent substrate 9 to polymerize and cure the active energy ray curable composition 10, and the shape transfer formed on the roll mold 7. Transfer the surface. As the active energy ray irradiation device 14, a chemical reaction chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a visible light halogen lamp, or the like is used. The amount of active energy ray irradiation is preferably such that the integrated energy at a wavelength of 200 to 600 nm is 0.1 to 50 J / cm ² . The irradiation atmosphere of active energy rays may be air or an inert gas atmosphere such as nitrogen or argon. Next, the prism sheet composed of the translucent substrate 9 (43) and the prism row forming layer (44) formed of the active energy ray curable resin is released from the roll mold 7.

  Returning to FIG. 1, the primary light source 1 is a linear light source extending in the Y direction. As the primary light source 1, for example, a fluorescent lamp or a cold cathode tube can be used. In this case, as shown in FIG. 1, the primary light source 1 is not only installed to face one side end face of the light guide 3, but is further placed on the opposite side end face as necessary. You can also

  The light source reflector 2 guides the light from the primary light source 1 to the light guide 3 with little loss. As the material, for example, a plastic film having a metal-deposited reflective layer on the surface can be used. As shown in the drawing, the light source reflector 2 avoids the prism sheet 4 and winds from the outer surface of the light reflecting element 5 to the edge of the light emitting surface of the light guide 3 through the outer surface of the primary light source 1. It is attached. On the other hand, the light source reflector 2 can also be wound from the outer surface of the light reflecting element 5 to the light emitting surface edge of the prism sheet 4 through the outer surface of the primary light source 1. A reflection member similar to the light source reflector 2 can be attached to the side end face other than the light incident end face 31 of the light guide 3.

  As the light reflecting element 5, for example, a plastic sheet having a metal vapor deposition reflecting layer on the surface can be used. In the present invention, it is also possible to use a light reflecting layer or the like formed by metal vapor deposition or the like on the back surface 34 of the light guide 3 instead of the reflecting sheet as the light reflecting element 5.

  A transmissive liquid crystal is formed on the light emitting surface (the light exit surface 42 of the prism sheet 4) of the surface light source device including the primary light source 1, the light source reflector 2, the light guide 3, the prism sheet 4, and the light reflecting element 5 as described above. By disposing the panel (liquid crystal display element) 8, a liquid crystal display device using the surface light source device of the present invention as a backlight is configured. The liquid crystal display device is observed by an observer from above.

  Light emitted from the light exit surface 42 of the prism sheet 4 of the surface light source device enters the entrance surface 81 of the liquid crystal panel 8, undergoes modulation according to the image information signal, and exits from the observation surface 82.

  In the present embodiment, since the light diffusion layer 45 of the prism sheet 4 has the above-described characteristics, the glare phenomenon in the liquid crystal display device without causing a significant decrease in the luminance of the surface light source device or the liquid crystal display device. Can be reduced.

  In the above embodiment, particularly when the total haze (HA1 + HA2) of the light diffusion layer 45 is 50% or more, the light diffusion layer 45 of the prism sheet exhibits a sufficient light diffusion function. The arrangement of the light diffusion sheet is not necessary. However, in the present invention, when the total haze is less than 50%, a separate light diffusion sheet is used in combination to further improve the light diffusibility while reducing the glare phenomenon in the liquid crystal display device, thereby increasing the luminance. Can be improved.

  In the above embodiment, a prism sheet having a prism row is used as a lens sheet having a lens row. However, in the present invention, other lens rows such as a lenticular lens having a lenticular lens row are used. Is also possible.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
The prism sheet, the surface light source device, and the liquid crystal display device described with reference to FIGS. 1, 2, and 5 were produced as follows.

  As the translucent substrate 43, a PET film having a thickness of 188 μm (trade name A4300, manufactured by Toyobo Co., Ltd.) was used. An acrylic resin having a refractive index of 1.49 (product name: TF-8, manufactured by Mitsubishi Rayon Co., Ltd.) is used as the translucent resin constituting the light diffusion layer, and a mixed solvent of MEK (methyl ethyl ketone) and toluene (mixing ratio of 50 wt. %) Was dissolved so that the concentration of TF-8 was 20 wt% to prepare a coating solution. As the first light transmissive light diffusing material 452, silicone resin fine particles having a refractive index of 1.42 and an average particle size of 3.0 μm (GE Toshiba Silicone, trade name Tospearl 130) are used. As the material 454, an acrylic resin fine particle (product name XX-49B, manufactured by Sekisui Plastics Co., Ltd.) having a refractive index of 1.49 and an average particle diameter of 5.0 μm is used, and the addition ratio of the first translucent light diffusing material However, 16.875 wt% and 5.625 wt% are added to the coating liquid with respect to the translucent resin so as to be 75 wt% with respect to the total amount of diffusing material added, and the mixture is stirred and mixed. Thus, a coating liquid containing the light diffusing materials 452 and 454 was prepared.

  Using the reverse gravure coating method, the coating solution was applied onto the PET film so that the average thickness after solvent drying was 6 μm and dried. Thus, a light diffusion layer having an uneven structure based on the light diffusing materials 452 and 454, that is, having an uneven surface, was formed on one surface of the PET film. As for the appearance of the obtained film, there was no occurrence of coating spots such as streaks, and a very good appearance was obtained. About a light-diffusion layer, it attached so that a light-diffusion layer may face the light-receiving side using a haze meter (Nippon Denshoku make, brand name NDH2000), total light transmittance (JIS K 7316) Tt, and haze (JIS K 7136). ) Haze was measured. As a result, the total light transmittance was 95.8%, and the haze was 67.0%. Since this haze value is the total haze (HA1 + HA2), in order to further measure the internal haze HA2, a transparent ultraviolet curable resin having a refractive index after curing of 1.52 is formed on the obtained light diffusion layer. After spreading, the surface of the PET film (product name: A4100, manufactured by Toyobo Co., Ltd.) with a thickness of 188 μm was overlaid on the UV curable resin and rubbed with a rubber roll to remove excess resin. The PET film was cured by irradiating with ultraviolet rays from the film side, and then the PET film was released to prepare a PET film having a light diffusion layer with a cured UV curable resin having a thickness of 15 μm and a smooth surface. When the haze of this film was measured in the same manner, it was 48.9%. That is, the internal haze HA2 has this value. Therefore, the ratio of internal haze to total haze was 73.0%.

  In addition, using a surface roughness meter (trade name Surfcom 1500DX-3DF, manufactured by Tokyo Seimitsu Co., Ltd.), a 1 μm probe is used to calculate the average interval Sm and ten-point average roughness Rz of the uneven surface of the light diffusion layer. (JIS B 0601-1994). As a result, the average interval Sm was 70.0 μm, and the ten-point average roughness Rz was 2.9 μm. Moreover, the aggregation state of the light diffusing material in the light diffusing layer was observed with transmitted light at a magnification of 500 times using an optical microscope (manufactured by Olympus, trade name MX61L). As a result, the maximum number of secondary particles having a major axis of 30 μm or more in a circular region having a radius of 70 μm of an arbitrary area on the surface of the light diffusion layer was one.

  A shape transfer surface corresponding to the shape of the prism array forming surface was formed on the surface of three types of JIS brass thin plates having a thickness of 1.0 mm and 400 mm × 690 mm to obtain a mold member. Here, the shape of the target prism array forming surface is the first prism array 411X having an apex angle of θ = 68 ° and a first height H1 of 30.5 μm, and an apex angle of θ = 68 °. The second prism row 411Y having a height H2 of 29.5 μm (the difference ΔH = 1 μm between the first height H1 and the second height H2), and the first prisms adjacent to each other. Two second prism rows 411Y are arranged between the prism rows 411X (see FIG. 5).

  Next, a stainless steel cylindrical roll having a diameter of 220 mm and a length of 450 mm was prepared, and a mold member was wound around the outer peripheral surface and fixed with a screw to obtain a roll mold. The translucent substrate with the light diffusion layer is supplied along the roll mold between the roll mold 7 and the rubber roll, and the translucent substrate is interposed between the rubber roll and the roll mold by a pneumatic cylinder connected to the rubber roll. The material was nipped.

On the other hand, the following ultraviolet curable composition phenoxyethyl acrylate (Biscoat # 192, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 50 parts by weight Hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur 1173 manufactured by Ciba Geigy)
: 1.5 parts by weight was adjusted to a viscosity of 300 mPa · S / 25 ° C.

  This ultraviolet curable composition was supplied to the surface on the opposite side to the surface to which the light-diffusing layer was provided of the translucent base material niped by a rubber roll into a roll mold. While rotating the roll mold, in a state where the ultraviolet curable composition is sandwiched between the roll mold and the translucent substrate, ultraviolet rays are irradiated from an ultraviolet irradiation device to polymerize and cure the ultraviolet curable composition. The prism row pattern on the shape transfer surface of the mold was transferred. Then, it released from the roll type | mold and obtained the prism sheet.

The prism sheet obtained as described above was cut into a 14.1 W (wide) size, and the light emitting surface of a 14.1 W (wide) size acrylic resin light guide with a cold cathode tube arranged on the side surface. As shown in FIG. 1 and FIG. 2, it was placed so that the prism array forming surface faced downward, and the other side surface and the back surface were covered with a reflection sheet to obtain a surface light source device. In this surface light source device, the cold cathode tube was turned on, and the normal luminance and half-value angle were measured using a luminance meter (trade name BM-7, manufactured by Topcon Corporation). As a result, the normal luminance was 2905 Cd / m ² and the half-value angle was 19.8 °.

  A transmissive liquid crystal panel was placed on the prism sheet of the surface light source device obtained as described above. This liquid crystal panel has a 60 ° gloss value of 48.6 on the observation surface measured by a gloss meter (trade name VGS-300A, manufactured by Nippon Denshoku Industries Co., Ltd.) and a 60 ° gloss value of 31.2 on the incident surface. It was a size 14.1 W (wide) liquid crystal panel with a pixel count XGA. In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 2]
The second light transmissive light diffusing material 454 used in Example 1 was changed to silicone resin fine particles having a refractive index of 1.42 and an average particle diameter of 4.5 μm (GE Toshiba Silicone, trade name Tospearl 145). 15.75 wt% and 6.75 wt% with respect to the translucent resin, respectively, so that the addition amount ratio of the first translucent light diffusing material is 70 wt% with respect to the total diffusing material addition amount. Was added to the coating solution and mixed by stirring to prepare a coating solution containing the light diffusing materials 452 and 454, and then a light diffusion layer was formed in the same manner as in Example 1. As for the appearance of the obtained film, there was no occurrence of coating spots such as streaks, and a very good appearance was obtained.

  About the obtained light-diffusion layer, it carried out similarly to Example 1, and measured the total light transmittance and haze. As a result, the total light transmittance was 94.1%, the total haze was 66.3%, and the internal haze HA2 was 57.9%. Therefore, the ratio of internal haze to total haze was 87.3%.

  Further, the average spacing Sm and the ten-point average roughness Rz of the uneven surface of the light diffusion layer were measured in the same manner as in Example 1. As a result, the average interval Sm was 37 μm, and the ten-point average roughness Rz was 2.5 μm. In addition, the maximum number of secondary particles having a major axis of 30 μm or more in a circular region having a radius of 70 μm of an arbitrary area on the surface of the light diffusion layer was one.

Further, a prism row forming layer was formed in the same manner as in Example 1 to obtain a prism sheet, and a surface light source device was produced in the same manner as in Example 1 using this prism sheet. In this surface light source device, the normal luminance and the half-value angle were measured in the same manner as in Example 1. As a result, the normal luminance was 2917 Cd / m ² and the half-value angle was 19.1 °.

  Further, a liquid crystal display device was produced in the same manner as in Example 1 using this surface light source device. In this liquid crystal display device, the glare was observed in the same manner as in Example 1. As a result, there was almost no glare phenomenon, and an easy-to-see image quality with a very smooth texture was obtained. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 3]
In Example 2, acrylic resin fine particles (product name XX-38B, manufactured by Sekisui Plastics Co., Ltd.) having a refractive index of 1.49 and an average particle size of 10 μm are further used as the third light transmissive light diffusing material 455. The second and third translucent light diffusing materials are each added to the coating liquid in an amount of 15.75% by weight, 4.5% by weight, and 2.25% by weight with respect to the translucent resin, respectively. After stirring and mixing to prepare a coating liquid containing the light diffusing materials 452, 454 and 455, a light diffusing layer was formed in the same manner as in Example 1. As for the appearance of the obtained film, there was no occurrence of coating spots such as streaks, and a very good appearance was obtained.

  About the obtained light-diffusion layer, it carried out similarly to Example 1, and measured the total light transmittance and haze. As a result, the total light transmittance was 93.5%, the total haze was 67.6%, and the internal haze HA2 was 56.0%. Accordingly, the ratio of internal haze to total haze was 82.8%.

  Further, the average spacing Sm and the ten-point average roughness Rz of the uneven surface of the light diffusion layer were measured in the same manner as in Example 1. As a result, the average interval Sm was 110 μm, and the ten-point average roughness Rz was 3.4 μm. In addition, the maximum number of secondary particles having a major axis of 30 μm or more in a circular region having a radius of 70 μm of an arbitrary area on the surface of the light diffusion layer was one.

Further, a prism row forming layer was formed in the same manner as in Example 1 to obtain a prism sheet, and a surface light source device was produced in the same manner as in Example 1 using this prism sheet. In this surface light source device, the normal luminance and the half-value angle were measured in the same manner as in Example 1. As a result, the normal luminance was 2892 Cd / m ² and the half-value angle was 19.1 °.

  Further, a liquid crystal display device was produced in the same manner as in Example 1 using this surface light source device. In this liquid crystal display device, the glare was observed in the same manner as in Example 1. As a result, there was almost no glare phenomenon, and an easy-to-see image quality with a very smooth texture was obtained. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

In addition, the scratch resistance was evaluated in the following manner using the films before prism formation obtained in Examples 2 and 3. First, the liquid crystal panel was placed on a horizontal table with the side in contact with the light diffusing layer facing up, and the film piece was placed thereon with the light diffusing layer facing down. A double-sided paper tape (Nystack NW-10 manufactured by Nichiban Co., Ltd.) was attached to the opposite surface of the light diffusion layer so as not to protrude from the film piece. Further, a metal rod having a hemispherical shape with a radius of 5 mm at the tip was fixed to the film piece vertically on the place where the double-sided tape of the film piece was attached. In this state, a downward load of 25 g was applied to the bar to move the liquid crystal panel and the horizontal direction by 25 mm to rub the liquid crystal panel surface and the light diffusion layer. The liquid crystal panel is the same as that used for luminance measurement, and is formed with minute irregularities. In addition, a similar test was performed on another type of liquid crystal panel on which a polarization conversion film (DBEF) was attached. The test was carried out 5 times by changing the location of the film and the liquid crystal panel, and was visually evaluated as follows:
◎ ... No damage at all 5 times;
○: Scratches occurred only once out of 5 times. Scratches are not visible with transmitted light, but only with reflected light;
Δ: scratches occur 2 to 5 times out of 5 times, and the scratches can be visually recognized only by reflected light;
X: Scratches can be visually recognized by both transmitted light and reflected light regardless of the number of scratches.

  When the anti-glare micro uneven type is used as the liquid crystal panel, the light diffusion layer side is used as the observation target, and when the DBEF using panel is used, the DBEF side is used as the observation target (no scratches are generated on the opposite side). .

  The evaluation results are summarized in Table 1.

  It was confirmed that the film of Example 3 had improved wear resistance with respect to the liquid crystal panel having a micro uneven structure as compared with Example 2.

[Example 4]
In the shape of the target prism row forming surface of the prism sheet, the second height H2 of the second prism row 411Y is set to 30 μm (difference ΔH = first height H1 and second height H2 = A liquid crystal display device was produced in the same manner as in Example 1 except that 0.5 μm).

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 5]
In the target prism row forming surface of the prism sheet, the second height H2 of the second prism row 411Y is set to 29 μm (the difference ΔH = the first height H1 and the second height H2 = A liquid crystal display device was produced in the same manner as in Example 1 except that the thickness was 1.5 μm.

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 6]
In the target prism row forming surface of the prism sheet, the second height H2 of the second prism row 411Y is set to 28.5 μm (difference between the first height H1 and the second height H2). A liquid crystal display device was manufactured in the same manner as in Example 1 except that ΔH = 2 μm.

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 7]
Except for the shape of the target prism row forming surface of the prism sheet, four second prism rows 411Y are arranged between the first prism rows 411X adjacent to each other (see FIG. 3). A liquid crystal display device was produced in the same manner as in Example 1.

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Example 8]
In the shape of the target prism row forming surface of the prism sheet, five second prism rows 411Y and four second prism rows 411Z are alternately arranged between the first prism rows 411X adjacent to each other. And the height of the first prism row 411X is 30.5 μm, the height of the second prism row 411Y is 0.5 μm smaller than the height of the first prism row 411X, and the second prism row A liquid crystal display device was manufactured in the same manner as in Example 1 except that the height of the row 411Z was 0.5 μm smaller than the height of the second prism row 411Y (see FIG. 6).

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  Next, the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out, but there was no change in the image before the dryer was charged.

[Comparative Example 1]
A liquid crystal display device was manufactured in the same manner as in Example 1 except that the prism sheet forming surface of the prism sheet had only the first prism array 411X.

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  However, the liquid crystal display device was held in a dryer at 50 ° C. for 10 hours, and then the surface light source device was made to emit light immediately after being taken out. Sticking occurred, and a streaky appearance based on the sticking occurred.

[Comparative Example 2]
In the shape of the target prism row forming surface of the prism sheet, the second height H2 of the second prism row 411Y is set to 28 μm (the difference ΔH = the first height H1 and the second height H2 = A liquid crystal display device was produced in the same manner as in Example 8 except that 2.5 μm).

  In this liquid crystal display device, when the surface light source device is made to emit light, a white image is displayed on the liquid crystal panel, and glare is observed, there is almost no glare phenomenon and an easy-to-view image quality with a very smooth texture is obtained. It was. Also, moire or streaky appearance based on sticking between the prism row forming surface of the prism sheet and the light emitting surface of the light guide, or sticking between the uneven surface of the light diffusion layer of the prism sheet and the liquid crystal panel The occurrence of such defects was not recognized.

  However, when the liquid crystal display device was kept in a dryer at 50 ° C. for 10 hours and then taken out and the surface light source device was made to emit light immediately, a streak-like appearance corresponding to the first prism row was generated.

1 schematically shows a prism sheet as an embodiment of a lens sheet according to the present invention, an embodiment of a surface light source device according to the present invention using the prism sheet, and an embodiment of a liquid crystal display device using the surface light source device. It is a perspective view. It is a typical fragmentary sectional view of FIG. It is a typical fragmentary sectional view of a prism sheet. It is a typical partial expanded sectional view of a prism sheet and a light guide. It is a typical fragmentary sectional view of a prism sheet. It is a typical fragmentary sectional view of a prism sheet. It is a schematic plan view which shows a secondary particle. It is a schematic diagram for demonstrating the manufacturing method of a prism sheet. It is a typical perspective view which shows the roll type | mold used for manufacture of a prism sheet. It is a typical disassembled perspective view which shows the roll type | mold used for manufacture of a prism sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Primary light source 2 Light source reflector 3 Light guide 31 Light incident end surface 32 Side end surface 33 Light emitting surface 34 Back surface 4 Prism sheet 41 Light incident surface 411 Prism rows 411a and 411b Prism surface 411X First prism rows 411Y and 411Z Prism array 42 Light exit surface 43 Translucent substrate 44 Prism array formation layer 44a Prism portion 44b Relaxing layer 45 Light diffusion layer 451 Translucent resin 452 First translucent light diffusing material 453 Secondary particles 454 Second translucency Light diffusing material 455 Third light transmissive light diffusing material 454 Light diffusing material 5 Light reflecting element 7 Mold member (roll type)
8 Liquid crystal panel 81 Incident surface 82 Observation surface 9 Translucent substrate 10 Active energy ray curable composition 11 Pressure mechanism 12 Resin tank 13 Nozzle 14 Active energy ray irradiation device 15 Thin plate member 16 Cylindrical roll 18 Shape transfer surface 28 Nip roll

Claims (13)

It consists of a sheet-like translucent member having a first surface and a second surface, wherein the first surface is a lens array forming surface formed by forming a plurality of lens arrays in parallel, and the second surface is a light diffusion layer The light diffusing layer is a lens sheet containing a light transmissive light diffusing material in a light transmissive resin,
In the light diffusion layer, when the surface haze is HA1 and the internal haze is HA2, the ratio of the internal haze HA2 to the total haze (HA1 + HA2) is 20% or more.
The lens array on the lens array forming surface includes a plurality of first lens arrays having a first height and a plurality of second lens arrays having a second height smaller than the first height. A lens sheet comprising at least one second lens array disposed between the first lens arrays adjacent to each other. The lens sheet according to claim 1, wherein the total haze (HA1 + HA2) is 50 to 85%. The surface of the light diffusing layer is an uneven surface, the average interval Sm of the unevenness is 150 μm or less, and the ten-point average roughness Rz is 4.0 μm or less. The lens sheet according to any one of the above. The translucent light diffusing material has an average particle diameter of 1 to 4 μm, a refractive index difference Δn1 with the translucent resin of 0.03 to 0.10, and an average particle Second light transmissive light diffusion having a diameter of 2 to 10 μm and a refractive index different from that of the first light transmissive light diffusing material and having a refractive index difference Δn2 of 0.00 to 0.08 with respect to the light transmissive resin. The lens sheet according to claim 1, comprising a material. The translucent resin is an acrylic resin, the first translucent light diffusing material is made of silicone resin fine particles, and the second translucent light diffusing material is made of acrylic resin fine particles, The lens sheet according to claim 4. The ratio of the addition amount of the first light transmissive light diffusing material to the total amount of the first light transmissive light diffusing material and the second light transmissive light diffusing material added to the light transmissive resin is 20% by weight. It is the above, The lens sheet as described in any one of Claims 4-5 characterized by the above-mentioned. The translucent light diffusing material further comprises a third translucent light diffusing material having an average particle diameter of 5 to 30 μm and a refractive index different from that of the first translucent light diffusing material, The lens sheet according to any one of claims 4 to 6. The lens sheet according to claim 7, wherein a convex portion having a height of 3 to 25 μm is formed on the surface of the light diffusion layer by the third light transmissive light diffusing material. The lens sheet according to claim 1, wherein the lens array is a prism array. The lens sheet according to claim 1, wherein a difference between the first height and the second height is 0.5 to 2 μm. 11. The lens sheet according to claim 1, wherein a distance between tops of the first lens rows adjacent to each other is 20 to 1000 μm. The primary light source, a light guide that is guided and emitted by light emitted from the primary light source, and the light emitted from the light guide is disposed so as to enter the light. It consists of the lens sheet described in one item,
The light guide includes a light incident end surface on which light emitted from the primary light source is incident and a light output surface from which the guided light is emitted, and the primary light source is adjacent to the light incident end surface of the light guide. The surface light source device is characterized in that the lens sheet is disposed such that the first surface faces the light emitting surface of the light guide. The surface light source device according to claim 12 and a liquid crystal panel arranged so that light emitted from a light diffusion layer of the lens sheet of the surface light source device is incident thereon,
The liquid crystal panel includes an incident surface on which light emitted from a light diffusion layer of the lens sheet is incident and an observation surface on the opposite side.

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