JP2016001322A - Optical sheet, surface light source device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet having excellent restoring property and scratch resistance even when the sheet has a convex optical unit, and requiring no protective sheet in a production process and during transportation, and to provide a surface light source device and an image display device having the optical sheet.SOLUTION: The optical sheet includes an optical function developing part comprising a plurality of convex optical units having ridgelines arrayed on one surface side of a transparent substrate. The optical function developing part is made of a cured product of an active energy ray-curable resin composition containing an acrylic resin and/or a methacrylic resin. A dent depth in an apex of each optical unit measured by a specified denting load is a specified value or more. When an acute angle formed by the ridgeline of the optical unit and an edge of the optical sheet is defined as a bias angle, an angle θ of the smallest angle in the bias angles on the respective edges satisfies 2°≤θ≤45°.

Description

  The present invention relates to an optical sheet having a bias angle, and a surface light source device and an image display device including the optical sheet.

In a display such as a liquid crystal display device, an optical sheet having a function of condensing, converging, diffusing, deflecting light, reflecting, or the like by refraction, diffraction, interference, or dispersion of light is used. Examples of such an optical sheet include a prism sheet used for a backlight (surface light source device) such as a liquid crystal display device, a lenticular lens sheet used for a stereoscopic photograph, a projection screen, and the like.
The optical sheet usually has a base material and a concave-convex optical function manifesting part in which a plurality of convex optical units such as unit prisms or unit lenses having a predetermined refractive index are arranged on the base material. The optical sheet is manufactured by cutting out into a rectangular shape from a large-area original fabric of the optical sheet.

  Conventionally, when a convex optical unit is provided on the surface of the optical sheet, when the optical sheet is stacked or wound during the manufacturing process or transportation, or when the optical sheet is subjected to heat or pressure during the manufacturing process, the optical unit There is a problem that a so-called “mountain collapse” occurs in which the vicinity of the top of the optical unit is damaged or broken, or the top of the optical unit is crushed. In addition, such problems such as scratches, breakage, and crushing of the top of the optical unit cause display unevenness such as white spots (white pattern) on the display surface of the display device provided with the optical sheet, thereby reducing display performance. It will contribute. Therefore, in the conventional optical sheet in which breakage, mountain crushing, and the like are likely to occur, a protective sheet is attached to the surface of the optical function developing portion (Patent Document 1). However, in order to simplify the work process and reduce the cost, it is desirable that the optical sheet does not require a protective sheet.

JP 2010-77168 A

  The present invention has been made to solve the above-mentioned problems, and even if it has a convex optical unit, it has excellent resilience and scratch resistance, and does not use a protective sheet during the manufacturing process and transportation. It is an object of the present invention to provide an optical sheet that may be provided, a surface light source device including the optical sheet, and an image display device.

  As a result of intensive studies by the present inventor, a specific indentation depth at a specific indentation load at the top of the optical unit of the optical sheet is set to a specific value or more, and the bias angle formed between the edge of the optical sheet and the ridge line of the optical unit is determined. The inventors have found that the above problems can be solved by setting the angle within a specific range, and have completed the present invention.

That is, the optical sheet of the first aspect according to the present invention is an optical sheet provided with an optical function expressing portion in which a plurality of convex optical units having ridge lines are arranged on one side of a transparent substrate,
The optical function manifesting part consists of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin,
The indentation depth measured at an indentation load of 0.5 mN according to ISO14577-1 at the top of the optical unit is 0.6 μm or more,
When the acute angle formed between the edge line of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest bias angle of each edge is 2 ° ≦ θ ≦ 45 °. Features.

Moreover, the optical sheet of the second aspect according to the present invention is an optical sheet provided with an optical function expressing part in which a plurality of convex optical units having ridge lines are arranged on one surface side of a transparent substrate,
The optical function manifesting part consists of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin,
The indentation depth measured at an indentation load of 300 mN according to ISO 14577-1 at the top of the optical unit is 15 μm or more,
When the acute angle formed between the edge line of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest bias angle of each edge is 2 ° ≦ θ ≦ 45 °. Features.

  In the optical sheet according to the present invention, the active energy ray curable resin composition is (A) an acrylic resin and / or methacrylic resin having one active energy ray curable group, and / or (B) active energy ray curable. An acrylic resin and / or a methacrylic resin having two functional groups, (C) a polyether-modified dimethylpolysiloxane, and (D) a compound represented by the following general formula (1), and (A) and (B) The total mass of is preferably 50% by mass or more based on the total solid mass of the active energy ray-curable resin composition.

  The surface light source device according to the present invention includes the optical sheet according to the present invention on the light emission surface side of the surface light source.

  The image display device according to the present invention is characterized in that the surface light source device according to the present invention is arranged on the back side of the image display device main body.

  Even if the optical sheet which concerns on this invention is provided with the convex optical unit, it is excellent in a recoverability and scratch resistance, and it is not necessary to use a protection sheet at the time of a manufacture process and transportation.

It is the typical top view and front view showing an example of the optical sheet concerning the present invention. It is the typical front view which showed an example of the cutting direction at the time of cutting out the optical sheet which concerns on this invention from the large area original fabric of an optical sheet. It is typical sectional drawing which showed an example of the surface light source device which concerns on this invention. It is typical sectional drawing which showed an example of the image display apparatus which concerns on this invention. It is the schematic which showed typically the evaluation method of the restoring property and damage resistance in this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

In the present invention, (meth) acrylic resin represents acrylic resin and / or methacrylic resin, and (meth) acrylate represents acrylate and / or methacrylate.
In the present invention, the resin is a concept including a polymer in addition to a monomer and an oligomer.
In the definition of film and sheet in JIS-K6900, a sheet is thin and generally refers to a flat product whose thickness is small for the length and width, and the film is extremely thick compared to the length and width. A thin, flat product that is small and has an arbitrarily limited maximum thickness, typically supplied in the form of a roll. Therefore, it can be said that a film having a particularly thin thickness among the sheets is a film, but the boundary between the sheet and the film is not clear and is difficult to distinguish clearly. Therefore, in the present invention, the meaning of both a thick sheet and a thin sheet is meant. Is defined as “sheet”.
In the present invention, the molecular weight means a weight average molecular weight which is a polystyrene equivalent value measured by gel permeation chromatography (GPC) in a THF solvent when having a molecular weight distribution, and when having no molecular weight distribution, It means the molecular weight of the compound itself.

(Optical sheet)
The optical sheet according to the first aspect of the present invention is an optical sheet provided with an optical function manifesting part in which a plurality of convex optical units having ridge lines are arranged on one side of a transparent substrate, wherein the optical function manifestation The indentation is made of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin, and measured at an indentation load of 0.5 mN according to ISO14577-1 at the top of the optical unit. When the depth is 0.6 μm or more and the acute angle formed by the edge of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest angle among the bias angles of each edge is 2 ° ≦ θ ≦ 45 °.

  The optical sheet of the second aspect according to the present invention is an optical sheet provided with an optical function developing part in which a plurality of convex optical units having ridge lines are arranged on one surface side of a transparent substrate, wherein the optical function is expressed. Part is made of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin, and an indentation depth measured at an indentation load of 300 mN at the top of the optical unit in accordance with ISO14577-1. Is defined as 15 μm or more, and when the acute angle formed by the edge of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest bias angle of each edge is 2 ° ≦ θ ≦ 45 °.

In the present invention, the “bias angle” is “an acute angle formed between the ridge line of the optical unit and the edge of the optical sheet”, that is, when the ridge line of the optical unit hits the edge of the optical sheet and stops. When the straight line extended in the direction in which the ridgeline of the unit extends and the straight line extended in the direction in which the edge of the optical sheet extends, an acute angle (angle less than 90 °) and an obtuse angle (angle 90 °) around the intersection Super angle) occurs, which means an acute angle. Since the optical sheet of the present invention is obtained by cutting out from a large-area original sheet of the optical sheet, the cutting direction when cutting out is the same as the extending direction of the edge after being cut out. Therefore, in the present invention, the “bias angle” can also be defined as “an acute angle formed by the ridgeline of the optical unit and the cutting direction of the optical sheet”.
In the optical sheet of the present invention, the angle θ of the bias angle having the smallest angle among the bias angles of the respective edges is set to 2 ° ≦ θ ≦ 45 °. Therefore, when the optical sheet of the present invention is cut out from the large-area original fabric into a predetermined shape, the angle θ of the bias angle having the smallest angle among the bias angles generated in each cutting direction in relation to the ridge line of the optical unit is 2 The angle between the ridge line direction and the cutting direction of the optical unit existing on the original fabric is adjusted so that ° ≦ θ ≦ 45 °.
In the optical sheet of the present invention, the optical units are usually arranged so that the ridge lines thereof are substantially parallel. In the present invention, “substantially parallel” means within a range of less than ± 1 °, particularly less than ± 0.5 ° from a truly parallel state.

Conventionally, when a convex optical unit is provided on the surface of the optical sheet, the vicinity of the top of the convex optical unit may be damaged or damaged if the optical sheet is stacked or wound during the transportation process. There was a problem that the mountain was crushed. Therefore, the protective sheet was stuck on the surface of the optical function expression part of an optical sheet. However, in order to simplify the work process and reduce the cost, it is desirable that the optical sheet does not require a protective sheet.
The inventor of the present invention has an excellent in restorability and scratch resistance by making the indentation depth (micro hardness) at a specific indentation load equal to or greater than a specific value in the optical function manifesting part. It was discovered that even without covering the surface with a protective sheet, it is possible to obtain an optical sheet that is free from damage, breakage, and crushing near the top of the convex optical unit.
However, when such an optical sheet is cut out from a large-area original fabric without being covered with a protective sheet, a new problem arises that burrs and whiskers are generated at the edge that is a cut portion. The burr (the remaining part protruding from the cut surface) is generated when the contact part with the blade of the cutting tool is deformed and restored after cutting. Beard is caused by a portion incompletely cut at the contact portion with the blade being stretched by the blade and extending beyond the limit of elastic stress. If the microhardness of the top of the optical unit is a specific value or more, the flexibility of the optical unit increases, so if the protective sheet is not attached, the blade of the cutting tool tends to slip or slip during cutting, Since the inclined surface of the convex optical unit to be cut (hereinafter sometimes simply referred to as “inclined surface”) is likely to be deformed at the contact portion with the blade or an incompletely cut portion is generated, It is thought that beards are likely to occur. Even if the microhardness of the optical function developing part is not less than a specific value, burrs and whiskers do not occur if they are covered with a protective sheet, but in that case, a protective sheet must be used. In other words, such an optical sheet does not require a protective sheet from the viewpoint of preventing scratches, breakage, crushing, etc., but a protective sheet is still necessary in order to eliminate burrs and whiskers at the edge. Met.
On the other hand, the optical sheet according to the present invention is intended to eliminate the need for a protective sheet, and even if a protective sheet is not used during the manufacturing process and transportation, the convex optical unit has resilience and scratch resistance. It is an optical sheet that not only excels, but also is less prone to burrs and whiskers at the edges. The reason why the optical sheet of the present invention is less likely to cause burrs and whiskers at the edge is that the ridge line of the optical unit and the cutting direction have a bias angle within the above range at the time of cutting from a large-area original fabric. The contact point between the blade and the slope becomes a point contact, and the entire blade and the slope do not contact at the same time, and the blade is gradually cut. Therefore, slippage and displacement are less likely to occur between the slope and the blade, and at the contact portion with the blade. This is probably because deformation and incomplete cutting are less likely to occur.
In addition, since the optical sheet according to the present invention is less likely to have burrs and whiskers at the edges, the yield in the manufacturing process is improved.
In the present invention, the protective sheet means a sheet commonly used for protecting the optical sheet by sticking to the surface, such as a protective sheet for preventing scratches.

Hereinafter, the optical sheet according to the present invention will be described in detail with reference to the drawings. In FIG. 1 and subsequent drawings, for convenience of explanation, the vertical and horizontal dimension ratios and the dimension ratios between the layers are exaggerated as appropriate instead of the actual dimensions.
FIG. 1 is a schematic plan view and a front view showing an example of an optical sheet according to the present invention.
An optical sheet 10 shown in FIG. 1 includes an optical function expression unit 12 on a transparent substrate 11. In the optical function manifesting part 12, a plurality of convex optical units 13 are arranged so as to have a ridge line 13L. The optical unit 13 has a top portion 14 and a slope 15, and a ridge line 13 </ b> L of the top portion 14 is indicated by a dotted line. An acute angle (bias angle) formed by the ridgeline 13L of the optical unit 13 and each edge 16a, 16b, 16c, 16d of the optical sheet is indicated by a hatched portion, and the angle of the smallest bias angle of each edge is θ To do.

  Hereinafter, the transparent base material, the optical function developing part, and the light diffusion layer that can be appropriately provided as necessary, which are components of the optical sheet according to the present invention, will be described.

(Transparent substrate)
The optical sheet of the present invention is usually provided with a layer of an optical function developing part on a transparent substrate. A transparent base material is not specifically limited, The transparent base material used for the conventionally well-known optical sheet can be used. As the transparent substrate, for example, those described in JP2009-37204A can be used.
The material and thickness of the transparent substrate may be appropriately selected in consideration of required properties such as desired transparency and mechanical strength.
The transparent substrate is usually a resin substrate. The resin material of the transparent substrate includes polyester resins such as polyethylene terephthalate and polyethylene naphthalate, (meth) acrylic resins such as polymethyl (meth) acrylate, polycarbonate resins, vinyl chloride resins, polymethacrylimide resins, polyester resins, cycloolefins Polymer (COP) resin and cycloolefin copolymer (COC) resin are preferred.

The thickness of the transparent substrate is usually preferably 50 to 500 μm, but is not limited thereto.
As the light transmittance of the transparent substrate, 100% is ideal for installation on the front surface of the display device, and the transmittance is preferably 85% or more.
The transparent base material may be subjected to a conventionally known mat treatment (formation of light diffusive minute irregularities), an antistatic treatment or an antireflection treatment on the surface thereof as necessary. Further, a matte treatment, an antistatic treatment, an antireflection treatment or the like may be performed between the transparent resin and the base material, or these may be used in any combination.

(Optical function expression part)
An optical function expression part consists of hardened | cured material of the active energy ray curable resin composition containing a (meth) acrylic resin, and has an uneven | corrugated shape provided with a some optical unit. The optical function manifesting part is usually formed on a transparent base material, but the transparent base material and the optical function manifesting part may be integrally formed. In this case, although not particularly limited, it is preferable to laminate and mold the optical function-expressing portion on the transparent substrate using an active energy ray-curable resin composition described later.

In the optical sheet of the first aspect according to the present invention, the indentation depth measured at an indentation load of 0.5 mN in accordance with ISO14577-1 at the top of the optical unit is 0.6 μm or more.
In the optical sheet of the second aspect according to the present invention, the indentation depth measured at an indentation load of 300 mN according to ISO14577-1 at the top of the optical unit is 15 μm or more.
The indentation depth is a micro hardness tester manufactured by Fisher Instruments Co., Ltd. (trade name: PICODETOR HM500, indenter is a diamond pyramid type, facing angle of 90 °) in accordance with ISO 14577-1. The value measured in.

  As described above, when the indentation depth at a specific indentation load at the top of the optical unit is equal to or greater than a certain value, the shape of the optical unit has excellent recoverability and is hardly damaged.

  The optical sheet is a prism sheet or lens that expresses a desired function such as condensing, diffusing, refraction, or reflection by modulating light by a geometric optical action such as refraction or reflection in the optical function manifesting part from its action mechanism. A sheet or the like is roughly classified into a diffraction grating or a hologram that modulates light by a wave optical action such as diffraction in an optical function manifesting unit and expresses a desired function such as diffraction or spectroscopy.

  FIG. 1 shows a triangular prism as a representative example of the “convex optical unit having a ridge line”. However, as other examples of the optical function manifesting part used in the present invention, a polygonal prism and a lenticular lens are shown. The present invention is applied to an optical function manifesting part in which a plurality of convex optical units whose ridgelines extend in a straight line are arranged in parallel adjacently, such as a linear Fresnel lens.

  Illustrating the specific shape (structure) of the optical function manifesting part as a prism sheet, prismatic unit prisms (optical units) such as triangular prisms (see FIG. 1), quadrangular prisms, pentagonal prisms, etc. are orthogonal to the ridge line direction. Examples include a large number of prisms arranged in the direction (prism linear array). In the case of a prismatic unit prism, the thickness T (the length from the convex top of the concavo-convex shape to the surface on the transparent substrate side as shown in FIG. 1) is uniform in the ridge line direction. It does not have to be uniform. For example, it may be different in the ridge line direction so that it is higher as it is closer to the peripheral portion and lower as it is closer to the central portion.

The shape of the unit prism in the cut surface including the normal direction of the plane of the transparent substrate (hereinafter simply referred to as “thickness direction”) and orthogonal to the ridge line direction, that is, the main cut surface is isosceles as shown in FIG. A triangle may be used, or an unequal triangle may be used although not shown.
The value of the apex angle of the triangular unit prism in the cross section in the thickness direction can be adjusted in the range of 40 to 120 °.

  The top of the unit prism may have a pointed shape as shown in FIG. 1 or may be a blunt apex with a radius of curvature of 1 to 10 μm near the top of the cross section in the thickness direction (not shown). If the top of the unit prism in the cross section in the thickness direction has such a blunt apex, stress concentrated mechanically and geometrically on the top can be dispersed, and deformation, chipping or crushing of the top can be reduced or suppressed.

  As an example of a specific shape of the optical function manifestation part as a lens sheet, a lenticular lens in which a large number of curved columnar unit lenses (optical units) such as a semi-cylindrical column or a semi-elliptical column are arranged in a direction orthogonal to the ridge line direction, And a linear Fresnel lens.

  The thickness T of the optical function manifesting portion (the thickness of the portion that becomes the maximum when the thickness varies in the ridge direction) may be appropriately adjusted according to the required performance, and is usually 20 to 1000 μm.

  The optical function manifesting part of the present invention may select or set the shape of the optical unit as appropriate according to the required performance.

The optical function manifesting part of the present invention can have an equilibrium elastic modulus measured by dynamic viscoelasticity measurement of less than 2.0 × 10 ⁷ Pa. Equilibrium modulus of the optical functional expression unit, more ^{preferably, 0.5 × 10 7 Pa~1.7 × 10} 7 Pa, even more preferably at ^{0.8 × 10 7 Pa~1.7 × 10 7} Pa .
By setting the equilibrium elastic modulus of the optical function developing part to less than 2.0 × 10 ⁷ Pa, it is possible to impart excellent restoration properties to the optical sheet according to the present invention.

The optical function developing part is a loss tangent which is a ratio of a loss elastic modulus (hereinafter simply referred to as “E”) measured by dynamic viscoelasticity measurement and a storage elastic modulus (hereinafter simply referred to as “E ′”). (Hereinafter simply referred to as “tan δ”) can be 0.6 to 3.0. The maximum value of tan δ of the optical function manifesting part is more preferably 0.7 to 3.0, still more preferably 0.8 to 2.0. By setting the maximum value of tan δ of the optical function developing part to 0.6 to 3.0, the glass transition temperature (hereinafter simply referred to as “Tg”) of the optical function developing part is 10 to 40 ° C., more preferably 10 -30 ° C, more preferably 15-28 ° C.
By setting Tg within the above range, the shape of the optical unit of the optical function manifesting part can be deformed and excellent in wearability.
In the present invention, the temperature indicating the maximum value of the loss tangent (tan δ) when measured with a tensile sine wave and a frequency of 1 Hz is Tg, and the storage elastic modulus (E ′) at 80 ° C. is the equilibrium elastic modulus. .

Here, the equilibrium elastic modulus, tan δ and Tg can be measured with a dynamic viscoelasticity measuring apparatus. In the dynamic viscoelasticity measuring device, the temperature dependency, frequency dependency, etc. of tan δ reflecting E * corresponding to elasticity, E ″ corresponding to viscosity, and the ratio of E ″ and E ′, which reflects vibration absorption. The Tg, equilibrium elastic modulus, etc. resulting from the intramolecular structure of the cured resin that forms the optical function developing part (the top part of the optical unit) can be evaluated based on the measurement result.
In addition, as a dynamic viscoelasticity measuring apparatus, SII nanotechnology Co., Ltd. brand name viscoelasticity spectrometer DMS6100 can be mentioned.

When the optical sheet of the present invention has the specific physical properties described above, the shape of the optical function-expressing portion of the optical sheet is hardly impaired, and a desired shape can be maintained.
In addition, the restorability of the optical function-expressing part of the optical sheet according to the present invention is preferably “3” or more, more preferably “4” or more, and particularly preferably evaluation “ 5 ".
The scratch resistance of the optical function-expressing portion of the optical sheet according to the present invention is preferably “3” or more, more preferably “4” or more, and particularly preferably evaluation “ 5 ".

The optical function developing part of the optical sheet according to the present invention is made of a cured product of an active energy ray-curable resin composition containing a (meth) acrylic resin (hereinafter sometimes simply referred to as “composition”).
In the present invention, the “active energy ray” is not only an electromagnetic wave having a wavelength in a non-visible region such as visible light, ultraviolet rays and X-rays, but also an active energy ray, which is a general term for particle beams such as electron beams and α rays. Radiation having an energy quantum sufficient to cause a crosslinking reaction or a polymerization reaction to a molecule having a curable group is included. As the active energy ray, ultraviolet rays are preferable.

As this (meth) acrylic resin, a monofunctional or polyfunctional monomer having a (meth) acryloyl group or (meth) acryloyloxy group as a conventionally known active energy ray-curable group for forming an optical sheet, a prepolymer ( Thru | or oligomer) etc. can be used.
Examples of the monofunctional monomer include vinyl monomers, (meth) acrylic acid ester monomers, and (meth) acrylamide derivatives described in JP-A-2009-37204.
Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, bisphenol A polyethoxydiol di (meth) acrylate and pentaerythritol tri (meth) acrylate described in JP-A-2009-37204.
Examples of the reactive prepolymer (or oligomer) include epoxy (meth) acrylate, urethane (meth) acrylate and polyester (meth) acrylate described in JP-A-2009-37204.

In a preferred embodiment of the optical sheet according to the present invention, the active energy ray-curable resin composition is (A) an acrylic resin and / or a methacrylic resin (hereinafter referred to as an active energy ray-curable group) having one (meth) acryloyl group. And / or (B) an acrylic resin and / or a methacrylic resin having two (meth) acryloyl groups as the active energy ray-curable group (hereinafter simply referred to as “( B) component ”), (C) polyether-modified dimethylpolysiloxane (hereinafter sometimes simply referred to as“ component (C) ”) and (D) a compound represented by the general formula (1) ( Hereinafter, it may be simply referred to as “component (D)”), and the total mass of (A) and (B) is the total solid mass of the active energy ray-curable resin composition. Not less than 50 mass% against the optical functional expression unit is preferable because easily express indentation depth of the particular range described above.
Hereinafter, these components (A) to (D) will be described in order.

(A) (Meth) acrylic resin having one (meth) acryloyl group as an active energy ray-curable group (A) The component (A) component has a (meth) acrylic group having one (meth) acryloyl group as an active energy ray-curable group It is a resin and may be a chain aliphatic or cyclic alicyclic or aromatic (meth) acrylic resin containing a hetero atom such as a halogen atom, sulfur atom, oxygen atom or nitrogen atom. The monofunctional (meth) acrylic resin described in JP 2009-37204 A can be used.

  The component (A) preferably includes phenoxyethyl (meth) acrylate (also known as 2-phenoxyethyl (meth) acrylate) and a compound represented by the following general formula (2).

（一般式（２）中、Ｒ^１及びＲ^２は、それぞれ独立に水素原子又はメチル基であり、Ｘは、水素原子又は炭素数１〜１０の鎖状の脂肪族炭化水素、脂環式炭化水素若しくは芳香族炭化水素であり、ｋは２〜６の整数である。）

(In General Formula (2), R ¹ and R ² are each independently a hydrogen atom or a methyl group, and X is a hydrogen atom or a C 1-10 chain aliphatic hydrocarbon or alicyclic carbonization. (It is hydrogen or an aromatic hydrocarbon, and k is an integer of 2 to 6.)

When the compound represented by the general formula (2) is contained in the composition together with the phenoxyethyl (meth) acrylate, flexibility is imparted to the optical function developing part which is a cured product of the composition, and the optical It is possible to make the function-expressing portion difficult to be damaged and to provide a recoverability that can be restored to the original shape even when an external force is applied to the optical function-expressing portion and the shape is deformed.
In the general formula (2), k is a positive integer of 2 to 6, and is preferably 2, 3 or 4 and more preferably 2 or 3 from the viewpoint of increasing the flexibility of the optical function manifesting part. .

(A) A component may be used individually by 1 type and may be used in combination of 2 or more type.
(A) 20-50 mass% is preferable with respect to the total solid content mass of a composition.
And it is preferable that it is 15-30 mass%, and, as for phenoxyethyl (meth) acrylate with respect to the total solid content mass of a composition, it is more preferable that it is 22-27 mass%.
Moreover, it is preferable that the compound represented by the said General formula (2) with respect to the total solid content mass of a composition is 5-20 mass%, and it is more preferable that it is 5-15 mass%.

  The total mass ((A) + (B)) of the component (A) and the component (B) described later is preferably 50% by mass or more based on the total solid mass of the composition, and is from 85 to 95. More preferably, it is mass%. By setting the total mass to 50% by mass or more with respect to the total solid content mass of the composition, the optical function developing part easily develops the indentation depth in the specific range described above.

(B) (Meth) acrylic resin having two (meth) acryloyl groups as active energy ray-curable groups (B) Component is (meth) acrylic having two (meth) acryloyl groups as active energy ray-curable groups It is a resin and may be a chain aliphatic or cyclic alicyclic or aromatic (meth) acrylic resin containing a hetero atom such as a halogen atom, sulfur atom, oxygen atom or nitrogen atom. The bifunctional (meth) acrylic resin described in JP 2009-37204 A can be used.
The component (B) is preferably a compound represented by the following general formula (3).

（一般式（３）中、Ｒ^１及びＲ^３は、それぞれ独立に水素原子又はメチル基であり、ｎ及びｍは、ｎ＋ｍ＝２〜２０を満たす正の整数である。）

(In General Formula (3), R ¹ and R ³ are each independently a hydrogen atom or a methyl group, and n and m are positive integers satisfying n + m = 2 to 20.)

  When the compound represented by the chemical formula (3) is contained in the composition together with the above-described phenoxyethyl (meth) acrylate and the compound represented by the general formula (2), the flexibility of the optical function developing portion is further increased. In addition, it is possible to make the recoverability of the optical function developing part excellent.

  In the general formula (3), n and m are positive integers satisfying n + m = 2 to 20. Examples of the individual values of n and m and combinations of both are, for example, m = 1, n = 1, m + n = 2, m = 3, n = 1, m + n = 4, m = 2, n = 2. m + n = 4, m = 6, n = 4, m + n = 10, m = 8, n = 2, m + n = 10, m = 5, n = 5, m + n = 10, m = 12, n = 8, m + n = 20, m = 10, n = 10, and m + n = 20. Further, from the viewpoint of increasing the flexibility of the cured product, n and m are preferably selected such that m + n = 2 to 12, and more preferably m + n = 4 to 10.

  The content of the compound represented by the general formula (3) is preferably 25 to 50% by mass, more preferably 30 to 50% by mass, particularly 35 to 35% by mass with respect to the total solid mass of the composition. It is preferable that it is 45 mass%.

(C) Polyether-modified dimethylpolysiloxane (C) component imparts slipperiness to the optical function manifesting part, and acts to alleviate the addition of external force when other members contact the uneven shape of the optical function manifesting part. Have.
In addition, when the composition is cured, the non-reactive component (C) is a network structure in which the component (A), the component (B), and the component (D) described later are cross-linked. It is presumed that it also works to fill the gaps in the mesh.

The component (C) preferably has a weight average molecular weight of 5000 to 25000.
As such (C) component, the compound represented by following General formula (4) is mentioned, for example.

（一般式（４）中、ａは１〜５の整数、ｂは１〜５の整数、ｃは１〜３０の整数及びｄは１〜７０の整数であり、かつ、ｃ≦ｄを満たし、Ｒ^１及びＲ^２はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。）

(In General Formula (4), a is an integer of 1 to 5, b is an integer of 1 to 5, c is an integer of 1 to 30, and d is an integer of 1 to 70, and c ≦ d is satisfied, R ¹ and R ² are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

  In the general formula (4), when a, b, c and d satisfy the above ranges, the properties as a polymer are expressed, and an appropriate solubility or dispersibility in the composition is obtained, and the optical function developing portion is leveled. There is an advantage that it is easy to impart properties and slipperiness as an agent.

Examples of commercially available products of component (C) include BYK-302, BYK-307 and BYK-330 manufactured by Big Chemie Japan, and KF-618 and KF- manufactured by Shin-Etsu Chemical Co., Ltd. 640 etc. are mentioned.
As a derivative of the component (C), a trade name BYK-377 manufactured by Big Chemie Japan Co., Ltd. into which a hydroxyl group has been introduced can be preferably used.

  The content of the component (C) is preferably 0.1 to 1% by mass and more preferably 0.2 to 0.7% by mass with respect to the total solid content of the composition.

(D) Compound Represented by General Formula (1) Component (D) is a compound represented by the following general formula (1) (glycerin epoxy triacrylate), and has three active energy ray-curable groups in one molecule. Therefore, it can be crosslinked with the above components (A) and (B) when the composition is cured, and has a function of generating many crosslinking points.
In addition, (D) component has a flexibility derived from the CHO- _(CH 2 O-) 2 moiety.
Thus, (D) component, the optical functional expression unit has the function of imparting toughness by flexibility derived from the number of crosslinking points and CHO- (CH ₂ O-) 2 moiety.

  As a commercial item of (D) component, Nagase ChemteX Co., Ltd. brand name DA-314 is mentioned, for example.

  (D) Content of a component becomes like this. Preferably it is 1-10 mass% with respect to the total solid content mass of a composition, More preferably, it is 2-7 mass%.

In addition to the above components, the composition of the present invention contains silicone, antioxidant, polymerization inhibitor, thickener, mold release agent, antistatic agent, ultraviolet absorber, antifoaming agent, solvent, A reactive acrylic resin, a non-reactive urethane resin, a non-reactive polyester resin, a pigment, a dye, a diffusing agent, or the like can be used in combination.
In the composition of the present invention, the total amount of the components that form the matrix of the optical sheet after curing other than the essential components and the essential components contained in the composition is usually based on the total mass of the composition. Usually, it is appropriately prepared so as to be 90% by mass or more.

(Light diffusion layer)
In the optical sheet according to the present invention, a light diffusing layer may be provided as needed to impart a light diffusing function.
The light diffusion layer is an arbitrary layer that is preferably provided, and may have any function of diffusing light, and a layer formed on a general light diffusion sheet can be used.
For example, a layer in which light diffusing fine particles are dispersed in a translucent resin can be applied. The light diffusing layer may be provided on the surface of the transparent substrate opposite to the optical function developing portion, or may be provided between the transparent substrate and the optical function developing portion.

As translucent resin which comprises a light-diffusion layer, resin similar to the said transparent base material can be mentioned.
Further, as the light diffusing fine particles, light diffusing fine particles generally used for a light diffusing sheet are used. For example, acrylic beads such as polymethyl methacrylate beads and polybutyl methacrylate beads, polycarbonate beads , Polyurethane beads, calcium carbonate beads and silica beads.
In addition, the thickness of a light-diffusion layer is 1-20 micrometers normally.

(Optical sheet manufacturing method)
The optical sheet of the present invention is obtained by cutting out the large-area original sheet of the optical sheet having the above-described layer configuration into a shape having a specific bias angle. FIG. 2 is a front view schematically showing an example of a cutting direction when cutting out the optical sheet according to the present invention from a large-area original sheet of the optical sheet. As shown in FIG. 2, the angle θ of the smallest angle among the bias angles (shaded portions) formed by the ridgeline 13L of the optical unit and the cutting directions 17a, 17b, 17c, and 17d is set to be 2 ° ≦ θ ≦ 45 °. Further, by cutting out the large-area original fabric 10 ′ into a rectangular shape along the cutting directions 17a, 17b, 17c, and 17d, an optical sheet according to the present invention as shown in FIG. 1 is obtained.
The optical sheet according to the present invention has a bias angle of 2 ° ≦ θ ≦ 45 ° which is the smallest among the bias angles formed by the respective edges and the ridge lines of the optical unit, so that the edges are not variably formed. And beards are less likely to occur. This is because, in the cutting process, the contact point between the blade of the cutting tool and the slope of the optical unit to be cut is a point contact, and the entire blade and the slope are not simultaneously contacted and gradually cut. This is thought to be because slippage and displacement are unlikely to occur between them.
The bias angle can be adjusted to a suitable angle from the viewpoint of preventing moire as long as the angle θ of the smallest bias angle is within the above range.

  The shape of the optical sheet of the present invention is not particularly limited as long as the angle θ of the smallest bias angle of each edge can be within the specific range, but is usually rectangular (rectangular, square). However, the edge of the optical sheet may have notches or protrusions (tabs, rims, etc.) for assembly, and the difference between two adjacent corners in a complementary angle relationship. May be a small trapezoid or a parallelogram.

  The method for producing a large-area original sheet of the optical sheet according to the present invention is not particularly limited as long as the above-described specific indentation depth can be obtained, and a conventionally known method can be used. For example, as shown in FIG. 2 of JP-A-2009-37204, the above-described composition is put into a mold having the shape of a desired optical function developing portion, a transparent base material is stacked thereon, and a transparent substrate is laminated using a laminator or the like. The material is pressure-bonded to the composition, and the composition is cured with ultraviolet rays or the like to form an optical function developing portion. Next, an optical sheet including an optical function manifesting part having a desired concavo-convex shape on a transparent substrate is obtained by peeling or removing the mold having the shape of the optical function manifesting part.

  The method of cutting out the large-area original fabric into a predetermined shape is not particularly limited.For example, a method of placing the original fabric on a support base and cutting it by bringing a cutting blade such as a Thomson blade into contact with the press mechanism, , Mechanical cutting with scissors or a cutter knife.

(Use of optical sheet)
The optical sheet according to the present invention can be used for, for example, a prism sheet used in a backlight of a liquid crystal display device or the like, a Fresnel lens sheet or a lenticular sheet used in a projection screen such as a projection television. The optical sheet according to the present invention can be suitably used in any of these, but among them, it can be suitably used as a prism sheet for a backlight for liquid crystal display devices.

(Surface light source device)
The surface light source device according to the present invention includes the above-described optical sheet of the present invention on the light emission surface side of the surface light source. Since the surface light source device according to the present invention uses the optical sheet according to the present invention, it is possible to prevent a decrease in yield due to the generation of foreign matter generated from burrs, whiskers, etc. of the optical sheet in the assembly process, resulting from scratches on the optical sheet, etc. The occurrence of uneven display is suppressed. As the surface light source used in the surface light source device according to the present invention, those having various specifications (forms) can be used, and there is no particular limitation. The surface light source device of the present invention is formed by placing the above-described optical sheet of the present invention on the light emission surface side of a surface light source in the form of a so-called edge light type, direct type, EL (electroluminescence) type or the like. Composed.
FIG. 3 is a schematic cross-sectional view showing a form of the surface light source device according to the present invention using an edge light type surface light source as an example of the surface light source device including the optical sheet according to the present invention. In the surface light source device 20 of FIG. 3, the transparent base material 11 and the optical function manifesting part 12 are provided on the light emission surface 22 side of the light guide plate 21 from the light emission surface 22 side.
3 is an edge light in which light is incident on the light guide plate 21 from the light source 24 provided on at least one side end surface 23 of the light guide plate 21 and light is emitted from the light emission surface 22. This is an edge light type surface light source device using a mold surface light source 26.

The light guide plate is a plate-like body made of a translucent material. The light guide plate 21 of FIG. 3 is configured to emit light introduced from the left side end surface 23 from the upper light emitting surface 22.
The light guide plate may be a conventionally known light guide plate, and may be formed of a light-transmitting material similar to the optical sheet or the transparent substrate.
The light guide plate is usually made of acrylic resin or polycarbonate resin.
The thickness of the light guide plate is usually 1 to 10 mm, and the thickness may be constant over the entire range. As shown in FIG. 3, when the light source 24 is provided on one end side, the side on which the light source 24 is provided. The end surface 23 side may be the thickest, and the taper shape may be gradually thinner toward the opposite side of the side end surface 23.
The light guide plate is preferably provided with a light scattering function inside or on the surface in order to emit light from the light emitting surface.

In the case of the edge light type surface light source device, the light source is for making light incident inside from at least one side end surface thereof, and is disposed along the side end surface of the light guide plate.
The light source is not particularly limited, and a linear light source such as a cold cathode tube may be used, or point light sources such as incandescent light bulbs and LEDs (light emitting diodes) may be arranged in a line along the side end surface. A plurality of small flat fluorescent lamps may be arranged along the side end surface.
When the apex angle of the optical unit is less than 80 degrees, the optical function expression unit 12 side of the optical sheet 10 is arranged in the direction facing the light guide plate 21 side, contrary to the case of FIG.

As shown in FIG. 3, light emitted from the side opposite to the light emission surface 22 of the light guide plate 21 or the like on the surface opposite to the light emission surface of the light guide plate or a surface other than the light emission surface. A light reflecting plate 25 may be provided for returning to the inside and emitting from the light emitting surface 22.
As the light reflecting plate, a thin metal plate deposited with aluminum or the like, or white foamed PET (polyethylene terephthalate) is used.
In addition, as a surface light source device, it can replace with the edge light type surface light source device used in the said embodiment, and can also use a direct type | mold surface light source device and an electroluminescent (EL) type surface light source device.

(Image display device)
The image display device according to the present invention is characterized in that the above-described surface light source device according to the present invention is arranged on the back side of the main body of the image display device. Since the image display device of the present invention includes the surface light source device of the present invention, it is possible to obtain stable and good display performance without causing display unevenness such as a white spot (white pattern) on the display surface.
Examples of the image display device include a liquid crystal display device using a liquid crystal cell as the image display device body. In the present invention, the liquid crystal cell refers to a module in which a liquid crystal compound is sealed with glass or the like, and may be a module including other members such as a polarizing plate or a color filter.

  FIG. 4 is a schematic sectional view showing an example of a liquid crystal display device including the edge light type surface light source device shown in FIG. A liquid crystal display device 30 shown in FIG. 4 includes a liquid crystal cell 31 and a surface light source device including the optical sheet 10 on one side thereof (on the back side (the side opposite to the side on which image display is observed in the liquid crystal display device)). 20 is provided.

  The liquid crystal display device may be a transmissive liquid crystal display device having a surface light source device (backlight) on the back side of the liquid crystal cell, or both reflected light display by external light and display by the backlight on the back side. It may be a transflective liquid crystal display device capable of achieving the above.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

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

First, the following components were mixed to prepare Composition 1 and Composition 2 that are materials for the optical function developing portion.
(Composition 1)
Phenoxyethyl acrylate (trade name SR339A manufactured by Sartomer): 9 parts by mass Orthophenylphenoxyethyl acrylate (also known as 2- (2-biphenylyloxy) ethyl acrylate): 36 parts by mass Bisphenol A diacrylate (general formula (3) M = n = 2, and R ¹ and R ³ are all hydrogen atoms, Kyoeisha Chemical Co., Ltd. trade name light acrylate BP-4EA): 8 parts by mass Bisphenol A diacrylate (m in general formula (3) = N = 5 and R ¹ and R ³ are all hydrogen atoms, trade name MIRAMER M2100 manufactured by MIWON Co., Ltd .: 42 parts by mass Polyether-modified dimethylpolysiloxane (trade name BYK-377 manufactured by Big Chemie Japan Co., Ltd.) ), In general formula (4), a = 5, b = 5, c = 30, d = 10 , R ¹ and R ² are methyl groups, weight average molecular weight 10800): 0.5 parts by mass Glycerin epoxy triacrylate (the above general formula (1), trade name DA-314 manufactured by Nagase ChemteX Corporation): 5 masses 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 184, manufactured by Ciba Japan Co., Ltd.): 3 parts by mass Phosphate ester release agent (trade name Chelex H-18D, manufactured by SC Organic Chemical Co., Ltd.): 0 .1 part by mass

(Composition 2)
Phenoxyethyl acrylate (trade name SR339A manufactured by Sartomer): 18.9 parts by mass Isobornyl acrylate: 8 parts by mass 4-acryloylmorpholine: 5 parts by mass Bisphenol A diacrylate (in formula (3), m = n = 2 And R ¹ and R ³ are all hydrogen atoms, Kyoeisha Chemical Co., Ltd. trade name light acrylate BP-4EA): 12 parts by mass Bisphenol A diacrylate (in general formula (3), m = n = 1, R ¹ is all methyl group, R ³ is all hydrogen atom, trade name light acrylate BP-2EM manufactured by Kyoeisha Chemical Co., Ltd .: 27 parts by mass Bisphenol A epoxy diacrylate (trade name FLEA manufactured by Kyoeisha Chemical Co., Ltd.) -POA, (content of bisphenol A epoxy diacrylate with respect to the total mass 49 mass%, Enoxyethyl acrylate content 51% by mass), weight average molecular weight 2000): 16.1 parts by mass Isocyanuric acid triacrylate (EO 3 mol modified, trade name Aronix M-315 manufactured by Toagosei Co., Ltd.): 13 masses 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 184, manufactured by Ciba Japan Co., Ltd.): 3 parts by mass Phosphate ester release agent (trade name Chelex H-18D, manufactured by SC Organic Chemical Co., Ltd.): 0 .05 parts by mass

(Example 1)
After the composition 1 prepared above is applied to a prism type in which the concave and convex shape of the optical function developing part as shown in FIG. 1 is formed, a transparent base material (Toyobo Co., Ltd.) made of polyethylene terephthalate (PET) with a thickness of 125 μm Co., Ltd., trade name A4300) was stacked, and the entire surface of the PET transparent substrate was pressure-bonded to the composition 1 with a laminator.
Next, using a mercury lamp, the composition 1 is irradiated with ultraviolet rays at 780 mJ / cm ² , the prism portion having a large number of unit prisms is cured, and integrated with a PET transparent substrate to form an optical function developing portion. did. Then, the large area original fabric of the optical sheet was obtained by peeling the prism mold.
Here, the shape of the optical unit (unit prism) included in the optical function manifesting portion was an isosceles triangular prism shape having a main cut surface shape with a height of 25 μm, a base of 50 μm, and an apex angle of 90 °. In addition, the optical function manifesting part is a unit in which a plurality of optical units are arranged adjacent to each other in the direction orthogonal to the ridge line at an arrangement period of 50 μm so that the ridge lines of the optical units are parallel to each other.
Subsequently, using a cutting tool having a Thomson blade in a frame shape, the bias angle formed by the ridgeline of the optical unit and the cutting direction (the edge of the optical sheet after cutting) from the large-area original sheet of the obtained optical sheet Among them, an optical sheet was obtained by cutting out a rectangle of 0.75 m (horizontal) × 0.40 m (vertical) so that the angle θ of the smallest bias angle was 2 °.

(Examples 2 to 6)
An optical sheet was obtained in the same manner as in Example 1 except that the angle θ of the smallest bias angle was changed as shown in Table 1.

(Comparative Example 1)
Other than cutting the optical sheet from the large-area original fabric so that the edge of the optical sheet after cutting (the cutting direction of the large-area original fabric) and the ridgeline of the optical unit are parallel (bias angle is 0 °) In the same manner as in Example 1, an optical sheet was obtained.

(Comparative Example 2)
First, a protective sheet (a 38 μm thick polypropylene base material coated with a rubber-based adhesive material) is bonded onto the large-area original optical function developing portion of the optical sheet obtained in the same manner as in Example 1. did. After that, the optical sheet is cut out from the large-area original sheet so that the edge of the optical sheet after cutting (the cutting direction of the large-area original sheet) and the ridge line of the optical unit are parallel (bias angle is 0 °). Except that, an optical sheet was obtained in the same manner as in Example 1.

(Comparative Example 3)
An optical function developing part is formed using the composition 2 instead of the composition 1, and the edge of the optical sheet after cutting (the cutting direction of the large-area original fabric) and the ridge line of the optical unit are parallel (the bias angle is 0). The optical sheet was obtained in the same manner as in Example 1 except that the optical sheet was cut out from the large-area original fabric so that

(Comparative Example 4)
Optical in the same manner as in Example 1 except that the angle θ of the smallest bias angle among the bias angles formed by the ridgeline of the optical unit and the cutting direction (the edge of the optical sheet after cutting) is 1 °. A sheet was obtained.

(Measurement of indentation depth)
In conformity with ISO 14577-1, the indentation load is 0 using a micro hardness tester manufactured by Fisher Instruments Co., Ltd. (trade name PICODETOR HM500, indenter is a diamond pyramid type, facing angle 90 °). The indentation depth at 5 mN and 300 mN was measured. The measurement results are shown in Table 1. In addition, the optical sheet obtained in Comparative Example 2 was measured for indentation depth with the protective sheet peeled off.

  The optical sheet produced in each example and each comparative example was evaluated for the burr / whisker occurrence rate, the restoring property of the optical function developing part, and the scratch resistance by the following methods and evaluation criteria. The evaluation results are shown together in Table 1.

(Burr and beard incidence)
The state of occurrence of burrs and whiskers at the edge of the optical sheet obtained in each example and each comparative example was visually observed.
Of the number of manufactured optical sheets (the number of processing), the ratio of the number of burrs that can be visually recognized, that is, the burr generation rate (%) and the number of processed optical sheets (the number of processing) The ratio of the number of sheets that could visually recognize the occurrence of the occurrence, that is, the total of the beard generation rate (%) was defined as the burr and beard generation rate (%).

(Restorability and scratch resistance)
(Evaluation method)
FIG. 5 is a schematic view schematically showing a method for evaluating resilience and scratch resistance in the present invention. As shown in FIG. 5, an optical sheet as a test piece on the movable platen 110 of an abrasion resistance tester. 10 was set so that the transparent substrate 11 side was positioned on the movable platen 110 side, and a load of 2.45 N (250 gf) was applied to the load portion 130 via the polarizing film 120 having an area of 12 cm ^{2 on} the test piece. And the state of the top part of the optical function expression part 12 when moving the movable board 110 to the arrow 140 direction of FIG. 5 for 20 second at the speed of 5 mm / s was evaluated by visual observation and microscope observation.

A test piece obtained by cutting the obtained optical sheet into a length of 150 mm and a width of 40 mm was used. In Comparative Example 2, the obtained optical sheet was cut into the size with the protective sheet adhered, and then the protective sheet was peeled off and used as a test piece.
As a measuring device, a trade name AB-301 Gakushin type friction fastness tester manufactured by Tester Sangyo Co., Ltd. was used.
As the polarizing film, a product name H25 manufactured by Dai Nippon Printing Co., Ltd. with an area of 12 cm ² was used, and the mat layer side was arranged facing the test piece.
The microscope used the brand name digital microscope VHX-200N by Keyence Corporation.
In addition, the bottom surface of the load portion has a donut shape with an outer diameter of 20 mm and an inner diameter of 10 mm, and the bottom area is 2.36 cm ² .

(Restorability evaluation)
Evaluation 5: No deformation of the shape was confirmed by microscopic observation.
Evaluation 4: Although deformation of the shape was confirmed by microscopic observation, it was not confirmed by visual observation on the backlight.
Evaluation 3: Although deformation of the shape was confirmed visually on the backlight, it was restored to the original shape within 10 minutes at room temperature (25 ° C.).
・ Evaluation 2: Deformation of the shape was confirmed by visual observation on the backlight, and the original shape was not restored within 10 minutes at room temperature (25 ° C.), but when heated to 35 ° C., the original shape was restored within 5 minutes. Restored shape.
Evaluation 1: Deformation of the shape was confirmed visually on the backlight, and even when heated at 35 ° C., the original shape was not restored within 5 minutes, but when heated at 80 ° C. for 1 minute, the original shape Restored.

(Scratch resistance evaluation)
Evaluation 5: No scratch was confirmed by microscopic observation.
Evaluation 4: One flaw was confirmed by microscopic observation, but no flaw was visually confirmed on the backlight.
-Evaluation 3: Two to three scratches were confirmed visually on the backlight.
Evaluation 2: Many scratches (streaks) were visually confirmed on the backlight.
Evaluation 1: It was confirmed that the entire prism surface was scraped by visual observation on the backlight.
In the restoration evaluation and scratch resistance evaluation, the microscope observation was performed by appropriately adjusting the microscope magnification within a range of 500 times.

The optical sheets obtained in Examples 1 to 6 have an indentation depth of 0.6 μm or more measured at an indentation load of 0.5 mN, or an indentation depth of 15 μm or more measured at an indentation load of 300 mN. In addition, the scratch resistance was good. In addition, since the smallest bias angle θ was in the range of 2 ° to 45 °, even if there was no protective sheet, the occurrence rate of burrs and whiskers was small (0 to 2.7%).
The optical sheet obtained in Comparative Example 1 has an indentation depth of 2.8 μm measured at an indentation load of 0.5 mN in accordance with ISO 14577-1, and an indentation depth measured at an indentation load of 300 mN is 20. Since the thickness was 8 μm, the restorability and scratch resistance were good. However, since the bias angle was 0 ° (the ridge line and the edge of the optical unit were parallel), the occurrence rate of burrs and whiskers was as high as 13% in the absence of the protective sheet.
Since the optical sheet obtained in Comparative Example 2 was cut in a state where a protective sheet was stuck on the optical function developing portion of the optical sheet obtained in Comparative Example 1, the restoration property and scratch resistance were good, and・ The beard incidence was as low as 1%.
That is, the optical sheets of Comparative Example 1 and Comparative Example 2 have high recoverability of the convex optical unit. Therefore, in Comparative Example 1 having no protective sheet, the incidence of burrs and whiskers was high when the bias angle was 0 °. However, in Comparative Example 2 which was cut with the protective sheet adhered, even if the bias angle was 0 °, the problem of generation of burrs and whiskers did not occur.
The optical sheet obtained in Comparative Example 3 had an indentation depth of 0.3 μm measured at an indentation load of 0.5 mN and an indentation depth of 13.8 μm measured at an indentation load of 300 mN. Even when the angle was set to 0 ° (the ridge line and the edge of the optical unit were parallel), no burr or whisker was generated, but the resilience and scratch resistance were poor. Incidentally, the optical sheet of Comparative Example 3 is a conventional optical sheet that is liable to cause crushing or the like because of its low recoverability of the convex optical unit. Absent.
The optical sheet obtained in Comparative Example 4 has an indentation depth of 2.8 μm measured at an indentation load of 0.5 mN according to ISO 14577-1, and an indentation depth of 20 indented measured at an indentation load of 300 mN. Since the thickness was 8 μm, the restorability and scratch resistance were good. However, since the smallest bias angle was set to 1 °, the occurrence rate of burrs and beards was as high as 10.9%. Therefore, it was found that if the restoration rate of the convex optical unit is increased, the generation of burrs and whiskers cannot be prevented if the bias angle is too small.

DESCRIPTION OF SYMBOLS 10 Optical sheet 10 'Large-area original fabric of optical sheet 11 Transparent base material 12 Optical function expression part 13 Optical unit 13L Edge line 14 Top part 15 Slope 16a, 16b, 16c, 16d Edge 17a, 17b, 17c, 17d Cutting direction 20 surface Light source device 21 Light guide plate 22 Light emission surface 23 Side end surface 24 Light source 25 Light reflection plate 26 Surface light source 30 Liquid crystal display device 31 Liquid crystal cell 110 Movable plate 120 Polarizing film 130 Load section

Claims (4)

An optical sheet provided with an optical function expressing part in which a plurality of convex optical units having ridge lines are arranged on one surface side of a transparent substrate,
The optical function manifesting part consists of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin,
The indentation depth measured at an indentation load of 0.5 mN according to ISO14577-1 at the top of the optical unit is 0.6 μm or more,
When the acute angle formed between the edge of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest angle among the bias angles of each edge is 2 ° ≦ θ ≦ 45 °,
The active energy ray-curable resin composition is (A) an acrylic resin and / or methacrylic resin having one active energy ray-curable group, and / or (B) an acrylic resin having two active energy ray-curable groups. And / or methacrylic resin, (C) polyether-modified dimethylpolysiloxane and (D) a compound represented by the following general formula (1), and the total mass of (A) and (B) is the active energy ray An optical sheet, which is 50% by mass or more based on the total solid mass of the curable resin composition.

An optical sheet provided with an optical function expressing part in which a plurality of convex optical units having ridge lines are arranged on one surface side of a transparent substrate,
The optical function manifesting part consists of a cured product of an active energy ray-curable resin composition containing an acrylic resin and / or a methacrylic resin,
The indentation depth measured at an indentation load of 300 mN according to ISO 14577-1 at the top of the optical unit is 15 μm or more,
When the acute angle formed between the edge of the optical unit and the edge of the optical sheet is defined as the bias angle, the angle θ of the smallest angle among the bias angles of each edge is 2 ° ≦ θ ≦ 45 °,
The active energy ray-curable resin composition is (A) an acrylic resin and / or methacrylic resin having one active energy ray-curable group, and / or (B) an acrylic resin having two active energy ray-curable groups. And / or methacrylic resin, (C) polyether-modified dimethylpolysiloxane and (D) a compound represented by the following general formula (1), and the total mass of (A) and (B) is the active energy ray An optical sheet, which is 50% by mass or more based on the total solid mass of the curable resin composition.

  A surface light source device comprising the optical sheet according to claim 1 or 2 on a light emission surface side of a surface light source. An image display device in which the surface light source device according to claim 3 is arranged on the back side of the image display device body.

Images