JP2010085425A - Lens sheet, planar light source device, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet capable of improving both of the luminance and defect concealment nature of a planar light source device. <P>SOLUTION: A plurality of prism sequences 411 are formed in parallel on the side of a first surface 41 of a sheet-like translucent member having the first surface 41 and a second surface 42. The sheet-like translucent member includes a translucent substrate 43, a light diffusion layer 45 disposed on the side of its one surface, and a translucent prism sequence forming layer 44 disposed on the side of the other surface of the translucent substrate 43. The light diffusion layer 45 contains a first translucent light diffusion material 452 composed of silica particulates of a mean particle diameter 1 to 100 nm in an acrylic translucent resin 451, and a second translucent light diffusion material 452' composed of resin particulates of a mean particle diameter 1 to 15 μm in an acrylic translucent resin 451. The surface on the side opposite to the translucent substrate 43 of the light diffusion layer 45 is formed in an irregular shaped surface based on a part of the first translucent light diffusion material 452 and a part of the second translucent light diffusion material 452'. <P>COPYRIGHT: (C)2010,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 the visibility of surface structure defects in the lens array of the lens sheet in the image display of a liquid crystal display device, or a mat structure or lens array formed on the light exit surface of the light guide or the back surface on the opposite side. The present invention relates to a lens sheet, a surface light source device, and a liquid crystal display device that are intended to reduce the visibility of defects in a surface structure such as an array structure.

  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 includes a fluorescent tube as a primary light source, a light guide, a reflection sheet, a prism sheet as a light deflection element, and the like. 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 triangular cross section with apex angles of 60 ° to 100 ° are arranged in parallel at a pitch of 30 to 50 μm.

  As the prism sheet, as described in JP-A-6-324205 (Patent Document 1), JP-A-10-160914 (Patent Document 2) and JP-A 2000-353413 (Patent Document 3). 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 1, 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 of Patent Document 2, 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 3, the brightness of the surface light source device is increased and the viewing angle is expanded by applying a light diffusing fine particle layer such as transparent beads.

On the other hand, in Japanese Patent Application Laid-Open No. 2005-316450 (Patent Document 4), Japanese Patent Application Laid-Open No. 2006-154838 (Patent Document 5) and Japanese Patent Application Laid-Open No. 11-326608 (Patent Document 6), a transparent substrate is made transparent. An antiglare film is described in which an antiglare layer is formed in which resin fine particles and silica fine particles having an average particle diameter different from that are contained in a light-sensitive resin.
JP-A-6-324205 JP-A-10-160914 JP 2000-353413 A JP-A-2005-316450 JP 2006-154838 A JP 11-326608 A

  As described in Patent Documents 1 to 3, as one of the functions of the surface structure having the light diffusing function of the prism sheet, by diffusing light by each protrusion, and expressing a desired haze (Haze), The target surface light source luminance is adjusted.

  However, in the above prior art, if the amount of fine particles added to the coating film forming the surface structure is decreased with the aim of improving the luminance of the surface light source device, the surface structure defect of the prism row becomes easy to be visually recognized. A surface structure defect such as a mat structure or a lens array arrangement structure formed on the light emitting surface of the light guide or the back surface on the opposite side thereof is likely to be visually recognized, and so-called defect concealment is reduced. That is, it has been difficult to achieve both improvement in luminance of the surface light source device and improvement in defect concealment. Defect concealment increases in importance especially when a high brightness light source is used as the primary light source.

  In addition, Patent Documents 4 to 6 do not have any suggestion regarding the technical problem of improving the defect concealing property.

  Therefore, an object of the present invention is to provide a lens sheet that can achieve both improvement in luminance of a surface light source device and improvement in defect concealment. Another object of the present invention is to provide a surface light source device having such a lens sheet. A further object of the present invention is to provide a liquid crystal display device having the above surface light source device.

According to the present invention, as a solution to any of the above problems,
A plurality of lens rows are formed in parallel on the first surface side of the sheet-like translucent member having the first surface and the second surface,
The sheet-like translucent member includes a translucent base material and a light diffusion layer disposed on one side of the translucent base material, and the surface of the light diffusion layer is the sheet-like shape. Forming a second surface of the translucent member;
The light diffusing layer contains a first light transmissive light diffusing material having an average particle diameter of 1 nm to 100 nm and a second light transmissive light diffusing material having an average particle diameter of 1 μm to 15 μm in the light transmissive resin. A lens sheet,
Is provided.

  In one aspect of the present invention, the translucent resin is an acrylic resin, the first translucent light diffusing material is silica fine particles, and the second translucent light diffusing material is resin fine particles. In one aspect of the present invention, the surface of the light diffusing layer opposite to the side of the light transmissive substrate has at least a part of the first light transmissive light diffusing material and a second light transmissive light diffusion. It is an uneven surface formed based on at least a part of the material. In one aspect of the present invention, the light diffusion layer has a haze of 30% or less and a visibility limit line pair period of 70 μm or more. In one aspect of the present invention, the sheet-like translucent member includes a translucent lens array forming layer disposed on the other surface side of the translucent substrate, and the translucent lens The plurality of lens rows are formed in the row forming layer, and the surface of the translucent lens row forming layer opposite to the side of the translucent substrate is the first surface of the sheet-like translucent member. Is forming. In one aspect of the present invention, the lens array is a prism array.

Moreover, according to the present invention, as a solution to any of the above problems,
Including a primary light source, a light guide that is guided and emitted by light emitted from the primary light source, and the lens sheet that is arranged so that the emitted light from the light guide is received. Become
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. A surface light source device, wherein the lens sheet is disposed such that a first surface of the sheet-like translucent member faces a light emitting surface of the light guide.
Is provided.

Furthermore, according to the present invention, as a solution to any of the above problems,
The surface light source device and a liquid crystal panel arranged so that light emitted from the second surface of the sheet-like translucent member of the lens sheet of the surface light source device is incident,
The liquid crystal panel includes an incident surface on which light emitted from the second surface of the sheet-like translucent member of the lens sheet is incident and an observation surface on the opposite side thereof,
Is provided.

  According to the present invention as described above, there is provided a lens sheet capable of achieving both improvement in luminance of the surface light source device and improvement in defect concealment. The present invention also provides a surface light source device having such a lens sheet, and further provides a liquid crystal display device having the above surface light source device.

  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 other side end surfaces such as the side end surface 32 opposite to the light incident end surface 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 lens array formed on at least one of the two main surfaces of the light guide 3 should have an average inclination angle θa in the range of 0.5 to 15 degrees according to ISO4287 / 1-1984. This is preferable from the viewpoint of achieving uniformity in luminance within the surface 33. 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. High directivity such that the full width at half maximum of the emitted light luminous intensity distribution in the XZ plane 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 emitting face. Light having emission characteristics 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 acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, acrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and moldability. 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. In addition, (meth) acryl is a general term for acrylic and methacrylic.

  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 a surface on which many fine irregularities are formed, that is, an irregular surface.

  In FIG. 3, the typical partial expanded sectional view of the prism sheet 4 and the light guide 3 is shown. The prism sheet 4 is a sheet-like translucent substrate 43 whose both surfaces are flat and parallel to each other, and a translucency disposed on the lower surface side of the translucent substrate 43 (specifically bonded). The light-transmitting prism array forming layer 44 as a lens array forming layer and a light diffusion layer 45 disposed (specifically bonded) on the upper surface side of the light-transmitting substrate 43. These translucent base material 43, prism row forming layer 44 and light diffusion layer 45 constitute a sheet-like translucent member. A prism row 411 is formed on the lower surface of the prism row forming layer 44, and this lower surface forms the light incident surface 41. Further, the upper surface of the light diffusion layer 45 forms a light exit surface 42. The light incident surface 41 corresponds to the first surface of the sheet-like translucent member, and the light exit surface 42 corresponds to the second surface of the sheet-like translucent member. In addition, you may interpose the layer which has appropriate translucency, such as a layer for improving adhesiveness, between the lower surface of the translucent base material 43, and the translucent prism row formation layer 44. Similarly, a layer having an appropriate translucency such as a layer for enhancing the bonding property may be interposed between the upper surface of the translucent substrate 43 and the light diffusion layer 45.

  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 is a flat surface and is joined to the lower surface of the translucent substrate 43. The lower surface, that is, the light incident surface 41 of the prism row forming layer 44 is a prism row forming surface, and a plurality of prism rows 411 extending in the Y direction 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 is, for example, 10 μm to 500 μm.

  The prism row 411 has 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 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 large number of first light transmissive light diffusing materials (light diffusing particles) 452 having an average particle diameter of 1 nm to 100 nm and a large number of first light particles having an average particle diameter of 1 μm to 15 μm in the light transmitting resin 451. 2 translucent light diffusing material (light diffusing particles) 452 ′ is contained. The upper surface of the light diffusion layer 45 is formed on a surface on which many fine irregularities are formed, that is, an irregular shape surface. The fine irregularities are formed based on at least a part of the first light transmissive light diffusing material 452 and at least a part of the second light transmissive light diffusing material 452 '. That is, at least a part of the first light transmissive light diffusing material 452 and at least a part of the second light transmissive light diffusing material 452 ′ protrude from the surface of the light transmissive resin 451 forming the layer. Yes. Here, the protrusion of the light diffusing material 452 and 452 ′ does not necessarily require that the light diffusing material itself is exposed to the outside air. As shown in FIG. It may be covered with a film of resin 451 (a film-like portion existing between the light diffusing material and the outside air).

  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 translucent resin is dissolved in a solvent, and a necessary amount of first and second translucent light diffusing materials 452 and 452 ′ is added to the dope (paint). By applying this dope to the surface of the translucent substrate 43 and drying, irregularities due to the first and second translucent light diffusing materials 452 and 452 ′ 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 of the dope, and the average particle diameter of the first and second translucent light diffusing materials 452, 452 ′. Is possible. In order to obtain necessary luminance and concealability, the shape of the unevenness can be adjusted as appropriate. In addition, the shape of the unevenness to be formed is determined from the shapes of the first and second light transmissive light diffusing materials 452 and 452 ′. For example, when a spherical light diffusing material is used, It becomes a shape like an assembly of convex lenses. 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, or a comma coater.

  The translucent resin 451 can be used without particular limitation as long as it is a transparent resin that can disperse the first and second translucent light diffusing materials 452 and 452 ′ and has sufficient strength. . 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 and the light diffusing material 452 and the like. The use of an acrylic resin having a high light transmittance is particularly preferable.

  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.

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

  Note that the light-transmitting resin 451 can contain a leveling agent, a thixotropic agent, an antistatic agent, an ultraviolet absorber, and the like. Among these, by containing a leveling agent, aggregation of the light diffusing material can be suppressed, and irregularities due to the first and second light transmissive light diffusing materials 452 and 452 ′ can be easily formed.

  As the first light transmissive light diffusing material 452, inorganic fine particles such as silica, alumina, and glass can be appropriately selected and used.

  As the second light transmissive light diffusing material 452 ′, cross-linked organic fine particles such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, and melamine, silicone fine particles, and the like are appropriately selected and used. Can do. In particular, acrylic cross-linked fine particles are excellent in chemical resistance, so there is no occurrence of swelling after being added to the dope, so that the optical characteristics hardly change over time, and since they are excellent in heat resistance, they are particularly preferably used. I can do it.

  The first and second translucent light diffusing materials 452 and 452 ′ can be used regardless of the shape such as a spherical shape, an indefinite shape, or a flat shape.

  By using the first light transmissive light diffusing material 452 and the second light transmissive light diffusing material 452 ′ together, it is easy to realize both improvement in luminance and improvement in concealment. Here, as the index of concealment, the value of “visualization limit line pair period” described in the examples described later can be given. A high visibility limit line pair period value means high concealment, and a low visibility limit line pair period value means low concealment.

  In order to further increase the luminance, the haze of the light diffusion layer 45 is preferably 30% or less. In order to further improve the concealing property, it is preferable that the visibility limit line pair period of the light diffusion layer 45 is 70 μm or more.

  The average particle diameter of the first light transmissive light diffusing material 452 is 1 nm to 100 nm, preferably 10 nm to 80 nm, and more preferably 15 nm to 50 nm. The average particle diameter of the second light transmissive light diffusing material 452 ′ is 1 μm to 15 μm, preferably 1.5 μm to 10 μm, and more preferably 2 μm to 9 μm.

  The content of the second light transmissive light diffusing material 452 ′ in the light diffusion layer 45 is preferably 1 part by weight or more and 30 parts by weight or less, and preferably 2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the light transmissive resin. Is more preferably 4 parts by weight or more and 18 parts by weight or less. When the content of the second light transmissive light diffusing material 452 ′ exceeds 30 parts by weight with respect to 100 parts by weight of the light transmissive resin, it becomes difficult to diffuse the particles in the dope or the light diffusing ability is high. There is a risk that the brightness becomes too low. In addition, if the content of the second light transmissive light diffusing material 452 ′ is too small, there is a possibility that sufficient defect concealing property cannot be obtained.

  A plurality of the first light transmissive light diffusing materials 452 may aggregate and aggregate in the coating liquid to form secondary particles 453. This aggregation is caused by the difference in affinity due to the difference in SP value (solubility parameter) between the first light transmissive light diffusing material 452, the light transmissive resin 451, and the solvent, the surface potential of the first light transmissive light diffusing material 452, Moreover, it changes with the viscosity of the dope at the time of coating, the length of the leveling time (time from coating to drying), the presence or absence of a leveling agent, and the like. As shown in the plan view of FIG. 4, the planar shape of the secondary particles 453 formed by aggregating a plurality of first light transmissive light diffusing materials 452 is generally not circular. Therefore, the size of the secondary particles 453 is represented by the major axis D. The size D of the secondary particles 453 is, for example, not less than 0.5 μm and not more than 10 μm.

  In the above embodiment, the light diffusing layer 45 is formed by applying a dope including the translucent resin 451 and the first and second translucent light diffusing materials 452 and 452 ′. It is possible to easily adjust the haze of the light diffusing layer 45 by the addition amount of the translucent light diffusing material 452, 452 ′, and it is possible to easily adjust the performance such as the luminance and viewing angle of the surface light source device. It is.

  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 acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, acrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and moldability. Such an acrylic resin is a resin containing methyl methacrylate as a main component, and preferably has a methyl methacrylate content of 80% by weight or more.

  FIG. 3 schematically shows how light is deflected 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 uneven surface 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, 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 and use of the surface light source device, A top flat portion or a top curved surface portion may be formed at the top of the row. 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. 5 is a schematic diagram showing an embodiment of forming a prism row in the prism sheet.

  In FIG. 5, reference numeral 7 denotes a mold member (roll mold) 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. 6 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. 7 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. 5, 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. It is preferable that the irradiation amount of the active energy ray is 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 array 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, a cold cathode tube, or a light emitting diode (LED) array 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, it is possible to achieve both improvement in luminance of the surface light source device and improvement in defect concealment.

  In the above embodiment, a prism sheet having a prism array is used as a lens sheet having a lens array. However, in the present invention, other lens arrays such as a lenticular lens having a lenticular lens array can be used. It is.

  In the above embodiment, since the light diffusion layer 45 of the prism sheet exhibits a light diffusion function, no separate light diffusion sheet is disposed thereon. However, in this invention, you may make it further improve the light diffusibility in a liquid crystal display device by using a separate light-diffusion sheet | seat together. The separate light diffusion sheet used in combination is disposed between the prism sheet and the liquid crystal panel so that light emitted from the second surface of the prism sheet enters.

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

[Example 1]
The prism sheet and the surface light source device described with reference to FIGS. 1 to 3 were produced as follows.

(Preparation of translucent substrate)
As the translucent base material, a PET film having a thickness of 188 μm (trade name T910E, manufactured by Mitsubishi Plastics, Inc.) was used.

(Preparation of coating solution)
An acrylic resin having a refractive index of 1.51 is used as the translucent resin constituting the light diffusion layer, and the concentration of the acrylic resin is 40 wt% in a mixed solvent of toluene and butanol (mixing ratio is 60 wt% toluene). So that a solution was prepared. As a photocuring initiator, trade name “Irgacure 184” manufactured by Ciba-Geigy Corporation was used. As the first light transmissive light diffusing material, silica fine particles having a refractive index of 1.47 and an average particle diameter of 25 to 35 nm are used, and as the second light transmissive light diffusing material, an average particle diameter of 5.45 is used. 0 μm acrylic resin fine particles (manufactured by Sekisui Chemical Co., Ltd., trade name XX-95B) were used. These are added in an amount of 100 parts by weight of the translucent resin, respectively, 2.5 parts by weight for Irgacure 184, 8.6 parts by weight for the first translucent light diffusing material, and for the second translucent light diffusing material. It added to the said solution so that it might become 2.0 weight part, and it stirred and mixed and the coating liquid containing the 1st and 2nd light-diffusion material was prepared.

(Coating)
Using the reverse gravure coating method, the coating liquid is applied on the PET film so that the average thickness after solvent drying is 3 μm, dried, polymerized and cured by ultraviolet irradiation, and on one side of the PET film, A light diffusing layer having irregularities based on the first and second translucent light diffusing materials, that is, having an irregular shape surface was formed. The appearance of the obtained light diffusion layer was very good with no coating spots such as streaks. FIG. 8 shows an optical micrograph of the surface of the light diffusion layer.

(Haze measurement)
About the obtained translucent sheet | seat with a light-diffusion layer, it attached so that a light-diffusion layer might face a light-receiving side using a haze meter (Murakami Color Research Laboratory make, brand name HM-150), and haze (JIS K7136). ) Haze was measured. As a result, the haze was 16.0%.

(Visibility limit line pair period measurement)
14.1 inch size total reflection type prism sheet (product name: S268YK, manufactured by Mitsubishi Rayon Co., Ltd.) is used, the emission light peak is in the normal direction of the emission surface (0 ° ± 5 °), and the full width at half maximum of the emission light distribution is Using a directional surface light source device of 17 °, the visibility limit line pair period of the light diffusion layer was measured.

  Directional surface light source device (14.1 inches, surface light source device using total reflection type prism sheet (trade name S268YK, manufactured by Mitsubishi Rayon Co., Ltd.), full width at half maximum of 17 °, peak angle of emitted light 0 ° (normal direction) ± The MTF measurement chart (manufactured by Edmund Optics, resolution target positive, thickness 1.5 mm) was placed on the directional surface light source device with the surface on which the stripe pattern was formed. . A light transmissive sheet with a light diffusing layer was placed thereon so that the light transmissive substrate faced the chart for MTF measurement.

  The directional surface light source device was turned on, and the striped pattern of the MTF measurement chart was visually observed through a light transmissive sheet with a light diffusion layer, and the value of the minimum line pair period (pitch) lp that could be identified was set as the visibility limit. As a result of the measurement, the visibility limit line pair cycle was 85.1 μm.

(Production of roll type for prism array formation)
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 was such that a large number of prism arrays having a pitch P = 50 μm and an apex angle θ = 65 ° were arranged in parallel. 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.

(Shaping the prism row)
The translucent substrate with the light diffusion layer is supplied along the roll mold between the obtained roll mold and the rubber roll, and the pneumatic cylinder connected to the rubber roll transmits light between the rubber roll and the roll mold. The substrate was nipped.

On the other hand, the following ultraviolet-curable composition phenoxyethyl acrylate (Osaka Organic Chemical Co., Ltd. biscoat # 192): 50 parts by weight Bisphenol A-diepoxy-acrylate (Kyoeisha Yushi Chemical Co., Ltd. epoxy ester 3000A): 50 parts by weight 2- Hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur 1173 manufactured by Ciba-Geigy Corporation): 1.5 parts by weight were 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.

(Production of surface light source device)
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.

(Brightness measurement)
In the obtained surface light source device, the cold cathode tube was turned on, and the peak luminance was measured using a luminance meter (trade name BM-7, manufactured by Topcon Corporation). As a result, the peak luminance was 2684 Cd / m ² .

  The numerical values of the translucent light diffusing material and the measured values of the characteristics related to Example 1 are shown in Tables 1 and 2 below. Both brightness and concealment are excellent. In Table 2, the peak luminance is also described as a relative value with 100% of Comparative Example 1 described later as 100%.

  In Tables 1 and 2, Examples are given in Ex. And a comparative example Com. Ex. It is abbreviated.

[Example 2]
The same process as in Example 1 was performed except that the second light transmissive light diffusing material was added to the solution so that the addition amount with respect to 100 parts by weight of the light transmissive resin was 2.5 parts by weight. .

  Tables 1 and 2 below show the numerical values and measured values of the respective characteristics of the translucent light diffusing material in Example 2. Both brightness and concealment are excellent.

[Example 3]
As the second light transmissive light diffusing material, acrylic resin fine particles (product name XX-101B, manufactured by Sekisui Plastics Co., Ltd.) having a refractive index of 1.560 and an average particle size of 4.0 μm are used. The process similar to Example 1 was performed except adding to a solution so that the addition amount with respect to 100 weight part of conductive resin might be 3.0 weight part.

  Tables 1 and 2 below show the numerical values and measured values of the respective characteristics of the translucent light diffusing material in Example 3. Both brightness and concealment are excellent.

[Example 4]
As the second light transmissive light diffusing material, in addition to those used in Example 1, acrylic resin fine particles having a refractive index of 1.540 and an average particle diameter of 2.5 μm (product name XX, manufactured by Sekisui Plastics Co., Ltd.) -102B), and the same steps as in Example 1 except that these are added to the solution so that the addition amount to 100 parts by weight of the translucent resin is 1.7 parts by weight. Executed.

  Tables 1 and 2 below show the numerical values and the measured values of the respective characteristics of the translucent light diffusing material in Example 4. Both brightness and concealment are excellent.

[Comparative Example 1]
(Preparation of coating solution)
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 is Toluene / MEK = 60/40 wt%) was dissolved so that the concentration of TF-8 was 35 wt% to prepare a solution. Acrylic resin fine particles (product name SSX-105, manufactured by Sekisui Plastics Co., Ltd.) having a refractive index of 1.49 and an average particle diameter of 4.5 to 5.5 μm are used as the first second light transmissive light diffusing material. As the second second translucent light diffusing material, acrylic resin fine particles having a refractive index of 1.49 and an average particle diameter of 7.0 to 9.0 μm (trade name SSX-108, manufactured by Sekisui Plastics Co., Ltd.) It was used. These are added in an amount of 23.1 parts by weight for the first second translucent light diffusing material and 9.9 for the second second translucent light diffusing material, respectively, with respect to 100 parts by weight of the translucent resin. It added to the said solution so that it might become a weight part, and it stirred and mixed and prepared the coating liquid containing the 1st and 2nd 2nd light-diffusion material.

(Coating)
Using the reverse gravure coating method, the coating solution was applied onto the PET film used in Example 1 so that the average thickness after solvent drying was 6 μm, and dried. As a result, a light diffusion layer having irregularities based on the first and second second light transmissive light diffusing materials, that is, having an irregular shape surface, was formed on one surface of the PET film.

  Then, the process similar to Example 1 was performed.

  The numerical values of the translucent light diffusing material and the measured values of the characteristics of the comparative example 1 are shown in the following Table 1 and Table 2, respectively. Insufficient brightness.

[Comparative Example 2]
The same process as in Example 1 was performed except that the second light transmissive light diffusing material was not used.

  Tables 1 and 2 below show the numerical values and the measured values of the respective characteristics of the translucent light diffusing material relating to Comparative Example 2. Concealment is insufficient.

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 partial expanded sectional view of a prism sheet and a light guide. 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. It is an optical microscope photograph of the surface of the light-diffusion layer obtained in the Example.

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 output surface 34 Back surface 4 Prism sheet 41 Light incident surface 411 Prism rows 411a and 411b Prism surface 42 Light exit surface 43 Translucent base material 44 Prism row Formation layer 45 Light diffusing layer 451 Translucent resin 452 First translucent light diffusing material 452 ′ Second translucent light diffusing material 453 Secondary particle 5 Light reflecting element 7 Mold member (roll type)
DESCRIPTION OF SYMBOLS 8 Liquid crystal panel 81 Incident surface 82 Observation surface 9 Translucent base material 10 Active energy ray curable composition 11 Pressure mechanism 12 Resin tank 13 Nozzle 14 Active energy ray irradiation apparatus 15 Thin plate-shaped member 16 Cylindrical roll 18 Shape transfer surface 28 Nip roll

Claims (8)

A plurality of lens rows are formed in parallel on the first surface side of the sheet-like translucent member having the first surface and the second surface,
The sheet-like translucent member includes a translucent base material and a light diffusion layer disposed on one side of the translucent base material, and the surface of the light diffusion layer is the sheet-like shape. Forming a second surface of the translucent member;
The light diffusing layer contains a first light transmissive light diffusing material having an average particle diameter of 1 nm to 100 nm and a second light transmissive light diffusing material having an average particle diameter of 1 μm to 15 μm in the light transmissive resin. There is a lens sheet.   2. The translucent resin is an acrylic resin, the first translucent light diffusing material is silica fine particles, and the second translucent light diffusing material is resin fine particles. The lens sheet described in 1.   The surface of the light diffusion layer opposite to the light transmissive substrate side is formed based on at least a part of the first light transmissive light diffusing material and at least a part of the second light transmissive light diffusing material. The lens sheet according to any one of claims 1 to 2, wherein the lens sheet has an uneven surface.   The lens sheet according to claim 1, wherein the light diffusion layer has a haze of 30% or less and a visibility limit line pair period of 70 μm or more.   The sheet-like translucent member includes a translucent lens array forming layer disposed on the other surface side of the translucent substrate, and the plurality of lenses are disposed on the translucent lens array forming layer. A row is formed, and a surface of the translucent lens row forming layer opposite to the translucent substrate side forms a first surface of the sheet-like translucent member. The lens sheet according to any one of claims 1 to 4. The lens sheet according to claim 1, wherein the lens array is a prism array. The primary light source, a light guide that is guided by the light emitted from the primary light source, guided and emitted, and the light emitted from the light guide are arranged to be incident. Comprising the lens sheet according to 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 arranged such that a first surface of the sheet-like translucent member faces a light emitting surface of the light guide. The surface light source device according to claim 7 and a liquid crystal panel arranged so that light emitted from the second surface of the sheet-like translucent member of the lens sheet of the surface light source device is incident,
The liquid crystal panel includes an incident surface on which light emitted from the second surface of the sheet-like translucent member of the lens sheet is incident and an observation surface on the opposite side.

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