JP6024800B2 - Optical sheet, surface light source device, and image display device - Google Patents

Description

  The present invention relates to an optical sheet having excellent finger mark resistance, 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, or reflecting light by refraction, diffraction, interference, or dispersion 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, and a Fresnel lens sheet used for a condenser lens of an overhead projector.
As the optical sheet, a base material, 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, and an optical function An optical sheet having a back surface layer (for example, a mat layer, a hard coat layer, etc.) containing a binder resin on a substrate opposite to the expression part is widely known.

Conventionally, the surface of an optical sheet that has been inadvertently grabbed by hand in various situations, such as the process of producing and packing an optical sheet, the process of cutting out to a predetermined shape, the process of superimposing, or the assembly work of the device. There is a problem that finger prints (fingerprints) are likely to adhere. Even if care is taken not to hold the optical sheet by hand, if the optical sheet accidentally comes into direct contact with the human body, a trace (skin contact trace) may be left on the surface of the optical sheet.
As a conventional method for preventing skin contact marks such as finger marks from adhering to the optical sheet surface, it is known to add an antifouling agent to the optical sheet. In Patent Document 1, the hard coat layer used in the optical laminate is made to contain a silicon-based compound, a fluorine-based compound or a mixture thereof as a stain-proofing agent and / or slipperiness-imparting agent. It describes that when the outermost surface of the hard coat layer is analyzed by XPS, the abundance of silicon atoms is 10% or more and / or the abundance of fluorine atoms is 20% or more ( Claim 1). Moreover, in the Example of patent document 1, the contact angle of artificial fingerprint liquid (JIS K2246) and water with respect to the surface of a hard-coat layer is measured, and antifouling property is evaluated based on the measured value (paragraph 0102). .

JP 2007-264281 A

  The present invention has been made in view of the above circumstances, and imparts excellent finger mark resistance (finger mark adhesion prevention) to the optical function manifesting part of an optical sheet provided with an optical function manifesting part having a convex optical unit. The purpose is to do.

The optical sheet according to the present invention is an optical sheet provided with an optical function expression part in which a plurality of convex optical units having apexes or ridges are arranged on one side of a transparent substrate,
The optical function developing part contains an antifouling agent selected from a silicon compound and a fluorine compound, and the total of silicon atoms and fluorine atoms when the surface is subjected to XPS analysis is 3% or more. In addition, 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.

  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 main body of the image display device.

  ADVANTAGE OF THE INVENTION According to this invention, the surface sheet light source apparatus and image display apparatus provided with the optical sheet which is excellent in the finger mark resistance (finger mark adhesion prevention property) of the optical function expression part which has a convex optical unit, and the said optical sheet are provided. be able to.

It is the typical perspective view showing an example of the optical sheet concerning the present invention. It is typical sectional drawing which showed an example of the laminated constitution of the optical sheet which concerns on this invention. 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 liquid crystal display device which concerns on 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 present invention is provided with an optical function expressing part in which a plurality of convex optical units having apexes or ridges are arranged on one side of a transparent substrate, and a back layer containing a binder resin is provided on the other side. Optical sheet,
The optical function developing part contains an antifouling agent selected from a silicon compound and a fluorine compound, and the total of silicon atoms and fluorine atoms when the surface is subjected to XPS analysis is 3% or more. And the indentation depth when 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,
The back layer contains an antifouling agent selected from silicon compounds and fluorine compounds, and the total of silicon atoms and fluorine atoms when the surface is subjected to XPS analysis is 3% or more. Features.

As a result of investigating the finger mark adhesion of the optical sheet, the present inventors have found that the optical function developing part having a convex optical unit is more easily attached to the optical function developing part than the back layer, and is contained in the optical function developing part. It was found that even if the amount of antifouling agent is the same as the amount of antifouling agent capable of preventing the adhesion of finger marks on the back surface layer, the finger marks adhere to the optical function developing part.
Therefore, as a result of earnest analysis of the cause of the difference in the degree of finger print adhesion between the front and back of the optical sheet, the present inventors have mainly made permanent deformation due to sebum adhesion and pressure on the finger print. I thought there were two types of causes. That is, when trying to grasp the optical function developing part side of the optical sheet by hand, the finger contacts only near the pointed top of the convex optical unit, the contact area is limited, and the finger contact pressure against the optical function developing part Is higher than the contact pressure of the finger on the back surface layer, so the traces that were thought to be particularly fingerprints of the optical function developing part are not only the so-called narrow fingerprints where sebum adheres strongly to the surface, but in addition to this, It was thought that the uneven shape of the trace was also due to the permanent deformation by being transferred by the pressure applied when the finger contacted. This is because the optical function expression part has a protrusion (ridge line or vertex) represented by a triangular prism whose ridge line protrudes to the outermost part, and the protrusion receives a pressure force of a finger in a small area, This is because stress concentrates and deformation remains unexpectedly. Therefore, it was found that finger marks could not be sufficiently eliminated by simply adding a stainproofing agent and / or slipperiness imparting agent.
And when trying to grab the optical function expression part side by hand, the optical function expression part can be deformed according to the shape of the finger to reduce the contact pressure and return to the original convex shape after the finger is released It has been found that if it has a restoring property, permanent deformation due to pressurization can be prevented, and it contributes to improvement of finger mark resistance (finger mark adhesion preventing property).
The present invention has been accomplished based on such knowledge.

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 perspective view showing an example of an optical sheet according to the present invention, and FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of the optical sheet according to the present invention. A cross section (main cut surface) perpendicular to the direction in which the prism extends is shown. In the present invention, the main cut surface includes a normal direction of the plane of the transparent substrate (hereinafter sometimes simply referred to as “thickness direction”) and is a cut surface perpendicular to the ridge line direction of the optical unit. Means.
The optical sheet 10 shown in FIG.1 and FIG.2 is provided with the optical function expression part 12 on the transparent base material 11, and the back surface layer 13 is provided in the side without the optical function expression part 12 of the transparent base material 11. FIG. ing. The optical function developing unit 12 includes a plurality of convex optical units 12a arranged, and FIGS. 1 and 2 show an optical sheet including a prism unit having a triangular prism shape as an example of the optical unit 12a.

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

(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 requirements such as desired transparency and mechanical strength.
The transparent substrate is usually a resin substrate. As the resin material for the transparent substrate, polyester resin such as polyethylene terephthalate and polyethylene naphthalate, (meth) acrylic resin such as polymethyl (meth) acrylate, polycarbonate resin, vinyl chloride resin, polyester resin, cycloolefin polymer (COP) resin And cycloolefin copolymer (COC) resin and the like are preferable.

The transparent base material may have a long shape or a single wafer shape having a predetermined size.
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 image display device, and the transmittance is preferably 85% or more.

(Optical function expression part)
The optical function developing unit is formed by arranging a plurality of convex optical units having apexes or ridges. 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.
The optical sheet according to the present invention expresses a desired function such as condensing, diffusing, refracting or reflecting by modulating light by geometric optical action such as refraction or reflection, for example, in the concave and convex shape of the optical function developing portion. The shape of the optical unit constituting the optical function developing unit can be selected or set as appropriate according to the required performance.
Hereinafter, the specific shape (structure) of the optical function manifesting part when the optical sheet according to the present invention is used as a prism sheet or a lens sheet will be described.

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. (Prism linear array) arranged in a direction orthogonal to (direction).
In the case of the prismatic unit prism (optical unit) as described above, the thickness T of the optical function developing portion (distance from the convex top of the concavo-convex shape to the surface on the transparent substrate side as shown in FIG. 2) is: The ridge line direction may be uniform or non-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.

  In addition, as an example of a specific shape of the concave-convex shape of the optical function developing portion as a prism sheet, an optical unit such as a cone or a pyramid such as a triangle, a square, a pentagon, or a hexagon is two-dimensionally provided on the transparent substrate surface. Are arranged in a plurality.

The shape of the main prism of the unit prism (optical unit) is not particularly limited as long as it has a vertex. However, it may be an isosceles triangle as shown in FIG.
The value of the apex angle of the triangular unit prism (optical unit) on the main cutting plane can be adjusted in the range of 40 to 120 °.

  As a lens sheet, the cyclic | annular or linear Fresnel lens etc. which have a vertex in the convex part of the optical unit which comprises an optical function expression part are mentioned, for example.

  In the present invention, the top of the optical unit may have a typically pointed shape as shown in FIGS. 1 and 2, and although not shown, the vicinity of the top of the cross section in the thickness direction is a blunt apex having a radius of curvature of 1 to 20 μm. But it ’s okay.

  The thickness T (see FIG. 2) of the optical function manifesting part may be appropriately adjusted according to the required performance, and is usually 20 to 1000 μm. Note that the thickness T is the thickness of the maximum portion when the thickness differs in the ridge line direction.

The optical function developing part has an indentation depth of 0.6 μm or more, preferably 0.8 μm or more, measured at an indentation load of 0.5 mN in accordance with ISO14577-1 at the top of the optical unit. is there. Thereby, since the said optical unit has the outstanding shape restoration property, it does not deform | transform permanently by pressurization at the time of a finger | toe contact etc., and the fingerprint resistance of an optical function expression part improves.
The indentation depth can be measured with a microhardness tester (trade name: PICODETOR HM500, indenter is a diamond pyramid type, facing angle 90 °) manufactured by Fisher Instruments Co., Ltd.

The optical function developing part is an active energy ray curable resin composition (hereinafter sometimes simply referred to as “composition”) containing an antifouling agent selected from silicon compounds and fluorine compounds. It can be formed by curing by irradiation.
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 the binder resin of the composition, for example, a conventionally known monofunctional or polyfunctional monomer, oligomer or prepolymer having a (meth) acryloyl group or (meth) acryloyloxy group for forming an optical sheet may be used. it can.
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 include epoxy (meth) acrylate, urethane (meth) acrylate and polyester (meth) acrylate described in JP-A-2009-37204.

  Moreover, the said composition contains the antifouling agent chosen from a silicon-type compound and a fluorine-type compound. Thereby, the optical function expression part becomes difficult to attach the finger trace resulting from sebum, and finger trace resistance improves.

  The silicon compound is preferably a compound in which the terminal or side chain of the compound is modified. Examples of such silicon compounds include those represented by the following general formulas (I) to (III) or (IV).

(In the above formula, R is a methyl group, a fluorine atom, an acrylic group, or a methacryl group as a hydrophobic group, and is a hydroxyl group, a carboxyl group, a polyether group, or an epoxy group as a hydrophilic group, or a mixture thereof. R ₁ is an alkyl group, preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, X is 0 to 1200, and Y is 0 to 1200. .)

  Moreover, a commercial item can also be used as said silicon compound. For example, TSF series made by Toshiba Silicone, X22 series and KF series made by Shin-Etsu Chemical, silaplane series made by Chisso, etc., silicon compounds having no reactive group, SUA1900L10 made by Shin-Nakamura Chemical Co., Ltd. (weight average) Silicon compounds having reactive groups such as molecular weight 4200) and SUA1900L6 (weight average molecular weight 2470), Shin-Etsu Silicone KNS5300, GE Toshiba Silicone UVHC1105 and UVHC8550 can be used.

Specific examples of the fluorine compound include the following general formula:
(A) w- (B) x- (D) y-CF ₃
(In the above formula, A represents one or more groups selected from the group consisting of CF ₂ , CFCF ₂ , and C (CF ₂ ) ₂ ;
B represents OCF ₂ CF ₂ , OCF ₂ CF (CF ₂ ), OCF ₂ C (CF ₂ ) ₂ , OCF (CF ₂ ) CF (CF ₂ ), OCF (CF ₂ ) C (CF ₂ ) ₂ , OC ( CF ₂ ) ₂ CF (CF ₂ ), OC (CF ₂ ) ₂ C (CF ₂ ) represents one or more groups selected from the group consisting of ₂ ;
D represents one or more groups selected from the group consisting of OCH ₂ CH ₂ , OCH ₂ CH ₂ CH ₂ , OC (O) (CH ₂ ) z;
w, x, y, and z represent numbers greater than 0 and less than or equal to 50. )
The thing represented by is mentioned.

  Moreover, a commercial item can also be used as said fluorine-type compound. For example, a megafac series manufactured by Dainippon Ink, Inc., such as MCF350-5, F445, F455, F178, F470, F475, F479, F477, TF1025, F478, F178K and other fluorine-based compounds having no reactive group, Fluorine-based compounds having reactive groups such as Defender TF3001, Defender TF3000, and Defender TF3028 manufactured by Nippon Ink Co., Ltd. can be used.

  The number average molecular weight of the antifouling agent is not particularly limited, but is usually 500 or more and 100,000 or less, preferably the lower limit is 750 or more, more preferably 1000 or more, and preferably the upper limit is 70,000 or less. More preferably, it is 50,000 or less.

  Further, according to a preferred embodiment of the present invention, the antifouling agent is a polyfunctional or polyfunctional polyfunctional group containing a polyorganosiloxane group, a polyorganosiloxane-containing graft polymer, a polyorganosiloxane-containing block polymer, a fluorinated alkyl group or the like. Those comprising acrylate are preferred. As a polyfunctional acrylate, for example, as a bifunctional acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butane Diol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, ethoxylated bisphenol F di (meth) acrylate, 1,6-hexanediol di (meth) acrylate 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerin di (meth) acrylate, neopentyl glycol di (meth) acrylate, pro Xylated neopentyl glycol di (meth) acrylate, pentaerythritol diacrylate monostearate, isocyanuric acid ethoxy modified di (meth) acrylate (isocyanuric acid EO modified di (meth) acrylate), bifunctional urethane acrylate, bifunctional polyester acrylate, etc. Is mentioned. Trifunctional acrylates include pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane EO modified tri (meth) acrylate, isocyanuric acid EO modified tri (meth) acrylate, ethoxylated trimethylolpropane tri Examples include (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, propoxylated glyceryl tri (meth) acrylate, and trifunctional polyester acrylate. Examples of the tetrafunctional acrylate include pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and ethoxylated pentaerythritol tetra (meth) acrylate. Examples of the pentafunctional or higher acrylate include dipentaerythritol hydroxypenta (meth) acrylate and dipentaerythritol hexaacrylate.

The content of the antifouling agent in the composition is appropriately determined such that the total of the abundances of silicon atoms and fluorine atoms when the surface of the optical function developing part is analyzed by XPS is 3% or more, preferably 4 It is determined as appropriate so that it becomes at least%. When the abundance ratios of silicon atoms and fluorine atoms are less than the lower limit value, the fingerprint resistance of the optical function developing portion becomes insufficient. Further, the content of the antifouling agent is preferably determined so that the total abundance of silicon atoms and fluorine atoms when the surface of the optical function developing portion is analyzed by XPS is 28% or less, and is 20% or less. It is more preferable to define as follows. When the abundance ratio of silicon atoms and fluorine atoms exceeds the upper limit, the antifouling agent often has an improvement in finger resistance, and the antifouling agent bleeds out from the surface of the optical function developing portion. The amount will increase.
Incidentally, the content of the antifouling agent actually contained in order to make the abundance of silicon atoms and fluorine atoms on the surface of the optical function developing part as described above varies depending on the antifouling agent used and is appropriately adjusted. Generally, it is 4-20 mass% with respect to the total solid content mass of a composition.

  XPS analysis is to measure a sample (optical function developing part or back layer) with an angle. Specifically, it is performed by easily converting an angle profile into a depth profile by the “maximum entropy method”. Is. XPS is a method for analyzing elements present on the surface of a sample and the composition thereof by X-ray photoelectron spectroscopy. An example of the XPS measurement conditions is the use of Thermo Electron (VG Theta Probe) XPS (X-ray photoelectron spectroscopy) device, the X-ray source is Monochromated Al Kα, the X-ray output is 100 W, and the measurement area is 400 μmφ, the lens can be formed by Angle Resolved, and the measurement angle can be arbitrarily changed. In this invention, it carries out on the conditions of five steps (28 degrees, 38 degrees, 48 degrees, 58 degrees, 68 degrees).

In a preferred embodiment of the optical sheet according to the present invention, the active energy ray-curable resin composition has one (meth) acryloyl group as a (A) active energy ray-curable group in addition to the antifouling agent (meta) ) Acrylic resin (hereinafter may be simply referred to as “component (A)”) and / or (B) (meth) acrylic resin having two (meth) acryloyl groups as the active energy ray curable group (hereinafter referred to as “active component”). (Simply referred to as “component (B)”), (C) polyether-modified dimethylpolysiloxane (hereinafter also referred to simply as “component (C)”), and (D) represented by general formula (4). The total mass of the active energy ray-curable resin composition is the total mass of the active energy ray-curable resin composition (hereinafter, also referred to simply as “component (D)”). 50 quality It is an optical functional expression unit is preferable because easily express indentation depth of the particular range described above is not less than%.
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) is preferably a phenoxyethyl (meth) acrylate (also known as 2-phenoxyethyl (meth) acrylate) and a compound represented by the following general formula (1).

(In General Formula (1), 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 (1) is contained in the composition together with the phenoxyethyl (meth) acrylate, flexibility is imparted to the optical function developing portion which is a cured product of the composition, and the optical Even when an external force is applied to the function-expressing portion and the shape is deformed, it is possible to impart a recoverability that can be restored to the original shape, thereby improving the resistance to finger marks.
In the above general formula (1), 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 developing 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 (1) 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 (2).

(In General Formula (2), 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 general formula (2) is contained in the composition together with the above-described phenoxyethyl (meth) acrylate and the compound represented by the general formula (1), the flexibility of the optical function developing part is further increased. As a result, the restoring ability of the optical function developing part is improved, and the fingerprint resistance can be improved.

  In the general formula (2), 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 (2) 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 (3) is mentioned, for example.

(In General Formula (3), 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 (3), 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 (4) The component (D) is a compound (glycerin epoxy triacrylate) represented by the following general formula (4), and has three active energy ray-curable groups in one molecule. Therefore, the composition can be crosslinked with the component (A) and the component (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 as necessary. A non-reactive acrylic resin, a non-reactive urethane resin, a non-reactive polyester resin, a pigment, a dye or a diffusing agent 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.

Moreover, the said optical function expression part can make the equilibrium elastic modulus measured by a dynamic viscoelasticity measurement 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 . Thereby, since the recoverability of an optical function expression part improves, finger-mark resistance improves.

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.

  It does not specifically limit as a method of forming an optical function expression part in a transparent base material, A conventionally well-known method can be used. For example, as shown in FIG. 2 of JP-A-2009-37204, the above composition is put into a mold having a desired optical function developing part shape, a transparent base material is stacked thereon, and a transparent base material is used using a laminator or the like. And the like, and the composition is cured with ultraviolet rays or the like, and the mold is peeled off or removed.

(Back layer)
The optical sheet which concerns on this invention is equipped with the back surface layer containing the antifouling agent chosen from binder resin, a silicon-type compound, and a fluorine-type compound on the transparent base material without an optical function expression part. Examples of the back layer include a mat layer and a hard coat layer.

The mat layer is a layer having a fine uneven shape, and is formed to impart diffusibility to expand the viewing angle, prevent interference due to close contact with other members, or hide defects in appearance such as scratches. Is done. Furthermore, when the optical sheet is combined with the liquid crystal display panel by forming the fine uneven shape at random, the occurrence of moiré due to the arrangement of the light guide plate of the optical sheet and the pixel arrangement of the liquid crystal display panel is prevented. It can also be prevented. It is also possible to make the reflective dots printed on the acrylic plate for backlight difficult to see.
The mat layer can be formed by, for example, matting agent coating, embossing (embossing) processing by hot pressing, mechanical processing such as sand blasting, casting method (casting) of transparent resin, or the like.
The matting agent is coated, for example, by coating a matting agent paint containing a matting agent in a binder made of a resin and a solvent on the surface of the prism layer opposite to the prism row.
Examples of the matting agent include fine particles such as polymethyl methacrylate (acrylic) beads, polybutyl methacrylate beads, polycarbonate beads, polyurethane beads, calcium carbonate beads, silicone beads, and silica beads. . The fine particles are not particularly limited, but preferably have an average particle size of 1 to 30 μm and a refractive index in the range of about 1.30 to 1.65, and the concentration of beads is 2 to 5% of the binder resin. It is preferable that
As the resin used for the binder of the mat layer, it can be freely selected from thermosetting resins, thermoplastic resins, ionizing radiation curable resins and the like. The refractive index of the resin may be matched with the matting agent as much as possible, or the refractive index of the resin and the matting agent may not be matched in order to control the light output characteristics.
As a coating method of the matting agent paint, various known coating methods such as die coating, gravure coating, and slit reverse coating can be selected.
The thickness of the mat layer is usually 1 to 20 μm.

  The hard coat layer is a layer that imparts scratch resistance and abrasion resistance to the object surface. In the present invention, the hard coat layer exhibits a hardness of H or higher in the pencil hardness test shown in JIS K5600-5-4: 1999. Say.

The hard coat layer is usually formed using an ionizing radiation curable resin. As the ionizing radiation curable resin for forming the hard coat layer, a resin having an acrylate functional group is preferable. Specific examples include relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyether resins, and polyhydric alcohols. . Also, di (meth) acrylates such as ethylene glycol di (meth) acrylate and pentaerythritol di (meth) acrylate monostearate; tri (meth) such as trimethylolpropane tri (meth) acrylate and pentaerythritol tri (meth) acrylate Acrylates; tetrafunctional or higher polyfunctional (meth) acrylates such as pentaerythritol tetra (meth) acrylate derivatives and dipentaerythritol penta (meth) acrylates; monomers of polyfunctional compounds such as; oligomers such as epoxy acrylate and urethane acrylate, etc. Can also be mentioned.
In addition, inorganic particles made of silica, alumina, etc. whose surface is coated to the extent that transparency is not impaired, or organic particles made of polyamide resin, silicon resin, urea resin, etc. are used to form a covalent bond between the particles and the hard coat component. Alternatively, a hard coat layer with improved hardness may be used.

  The means for forming the hard coat layer is not particularly limited. For example, there is a method in which the hard coat layer forming material containing the ionizing radiation curable resin is applied on a transparent substrate and cured by appropriate ionizing radiation. Can be mentioned.

  The film thickness after curing of the hard coat layer is preferably 0.1 μm or more, more preferably 0.8 μm or more, while the film thickness is preferably 100 μm or less, more preferably 20 μm or less. If the film thickness is 0.1 μm or more, sufficient hard coat performance can be easily obtained, and if it is 100 μm or less, sufficient strength can be easily obtained against external impacts.

  In addition, as a back surface layer of this invention, what formed the said mat layer in said hard-coat layer can also be used. In this case, it is preferable to form the back surface layer so that the mat layer is the outermost layer (surface opposite to the transparent substrate). In addition, an antistatic layer, a low refractive layer, or the like may be provided.

The back layer of the present invention contains an antifouling agent selected from silicon compounds and fluorine compounds. As the antifouling agent selected from the silicon-based compound and the fluorine-based compound contained in the back layer, the same ones as described above can be used.
The amount of the antifouling agent contained in the back surface layer is appropriately determined so that the total abundance of silicon atoms and fluorine atoms when the surface of the back surface layer is analyzed by XPS is 3% or more, preferably 4% or more. As appropriate. When the abundance ratio of silicon atoms and fluorine atoms is less than the lower limit value, the fingerprint resistance of the back surface layer becomes insufficient. Further, the content of the antifouling agent contained in the back layer is preferably determined so that the total of the abundances of silicon atoms and fluorine atoms when the surface of the back layer is analyzed by XPS is 28% or less, 20% More preferably, it is determined to be as follows. When the abundance ratio of silicon atoms and fluorine atoms exceeds the upper limit, the antifouling agent often has an improvement in finger resistance, and the antifouling agent bleeds out from the surface of the optical function developing portion. The amount will increase.

(Light diffusion layer)
Although not shown, the optical sheet according to the present invention may be provided with a light diffusion layer to provide a light diffusion function as necessary.
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 diffusion layer may be provided on the surface between the transparent base material and the back surface layer, or may be provided on the surface of the back surface layer opposite to the transparent base material. You may provide between function expression parts. Alternatively, light diffusing fine particles may be internally added to the prism resin portion (optical function developing portion) forming the prism sheet (optical sheet).

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, polymethyl methacrylate (acrylic) beads, polybutyl methacrylate beads, polycarbonate beads, Examples include polyurethane beads, calcium carbonate beads, and silica beads.
In addition, the thickness of a light-diffusion layer is 1-20 micrometers normally.

(Use of optical sheet)
The optical sheet according to the present invention can be used for, for example, a prism sheet used for a backlight of a liquid crystal display device or the like, a Fresnel lens sheet used for a projection screen of a projection television, or the like. 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. 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 back layer 13, the transparent substrate 11, and the optical function expression unit 12 are provided on the light emitting surface 22 side of the light guide plate 21 from the light emitting 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.

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.

(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.
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 are mixed to form a prism portion (optical function developing portion) material for the prism portion composition base formulation A, B, C (hereinafter simply referred to as “base formulation A, B, C”). Prepared). The formulation of each base formulation is that the indentation depth value measured at an indentation load of 0.5 mN in the prism portion after curing is 0.8 μm for base formulation A, 1.5 μm for base formulation B, and base formulation C. Is adjusted to 0.4 μm. Table 1 shows the components and the content (parts by mass) contained in each prism part composition base formulation.

(Prism part composition base formulation A: depth of penetration 0.8 μm)
Phenoxyethyl acrylate (trade name SR339A manufactured by Sartomer): 14.6 parts by mass Orthophenylphenoxyethyl acrylate (also known as 2- (2-biphenylyloxy) ethyl acrylate): 28 parts by mass Bisphenol A diacrylate (EO4 mol-modified) (In general formula (2), 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 ( EO 10 mol modification) (m = n = 5 in general formula (2), and R ¹ and R ³ are all hydrogen atoms, trade name MIRAMER M2100 manufactured by MIWON): 35 parts by mass Bisphenol A epoxy diacrylate (Kyoeisha Chemical Co., Ltd.) Product name FLEA-POA, manufactured by KK Enol A epoxy diacrylate content 49% by mass, phenoxyethyl acrylate content 51% by mass), weight average molecular weight 2000): 2 parts by mass Polyether-modified dimethylpolysiloxane (trade name BYK manufactured by Big Chemie Japan Co., Ltd.) -377), in general formula (3), 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 tri Acrylate (the above general formula (4), trade name DA-314 manufactured by Nagase ChemteX Corporation): 5 parts by mass isocyanuric acid triacrylate (EO 3 mol modified, trade name Aronix M-315 manufactured by Toagosei Co., Ltd.) : 3 parts by mass 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 18 manufactured by Ciba Japan Co., Ltd.) 4): 3 parts by mass Phosphoric ester release agent (trade name Chelex H-18D manufactured by SC Organic Chemical Co., Ltd.): 0.1 parts by mass

(Prism part composition base formulation B: indentation depth 1.5 μm)
Phenoxyethyl acrylate (trade name SR339A manufactured by Sartomer): 12 parts by mass Orthophenylphenoxyethyl acrylate (also known as 2- (2-biphenylyloxy) ethyl acrylate): 32 parts by mass Bisphenol A diacrylate (EO 4 mol modified) ( In general formula (2), 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 (EO 10 mol) Modification) (m = n = 5 in the general formula (2) and R ¹ and R ³ are all hydrogen atoms, trade name MIRAMER M2100 manufactured by MIWON): 42 parts by mass Polyether-modified dimethylpolysiloxane (BIC Chemie Japan) (Trade name BYK-377 manufactured by Co., Ltd.), general formula (3) A = 5, b = 5, c = 30, d = 10, R ¹ and R ² are methyl groups, weight average molecular weight 10800): 0.5 part by mass Glycerin epoxy triacrylate (the above general formula (4), Product name DA-314 manufactured by Nagase ChemteX Corporation: 5 parts by mass 1-hydroxycyclohexyl phenyl ketone (product name Irgacure 184 manufactured by Ciba Japan Co., Ltd.): 3 parts by mass Phosphate ester release agent ( SC Organic Chemical Co., Ltd. trade name Chelex H-18D): 0.1 parts by mass

(Prism composition-based formulation C: depth of penetration 0.4 μm)
Phenoxyethyl acrylate (trade name SR339A manufactured by Sartomer): 19 parts by mass Isobornyl acrylate: 8 parts by mass 4-acryloylmorpholine: 5 parts by mass Bisphenol A diacrylate (EO 4 mol modified) (in formula (2), m = n = 2, and R ¹ and R ³ are all hydrogen atoms, trade name light acrylate BP-4EA manufactured by Kyoeisha Chemical Co., Ltd .: 12 parts by mass Bisphenol A diacrylate (EO2 molar modification) (general formula (2) M = n = 1, R ¹ is all methyl groups, and R ³ is all hydrogen atoms, Kyoeisha Chemical Co., Ltd. trade name Light Acrylate BP-2EM): 27 parts by mass Bisphenol A epoxy diacrylate (Kyoeisha Chemical Co., Ltd.) Product name FLEA-POA manufactured by (Co., Ltd.) 49% by mass of acrylate, 51% by mass of phenoxyethyl acrylate), weight average molecular weight 2000): 16 parts by mass Polyether-modified dimethylpolysiloxane (trade name BYK-377 manufactured by Big Chemie Japan Co., Ltd.), In the general formula (3), a = 5, b = 5, c = 30, d = 10, R ¹ and R ² are methyl groups, weight average molecular weight 10800): 0.5 part by mass Isocyanuric acid triacrylate (EO 3 mol) Modified, trade name Aronix M-315 manufactured by Toagosei Co., Ltd .: 13 parts by mass 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 184 manufactured by Ciba Japan Co., Ltd.): 3 parts by mass Phosphate ester release Agent (SC Organic Chemical Co., Ltd., trade name Chelex H-18D): 0.1 parts by mass

(Matte layer material base formulation)
1% by weight of cross-linked acrylic powder (average particle size: 5 μm) manufactured by Soken Chemical Co., Ltd. was mixed with polyester resin, and an appropriate amount of isocyanate curing agent was added. Using an organic solvent in which equal amounts of methyl ethyl ketone and toluene were mixed, the solid content was diluted to 35% by weight to prepare a mat base material base formulation containing light diffusing fine particles.

Example 1
In the prism part composition base formulation A, the silicon antifouling agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., UT3971) is 1% by mass of the total solid content, and the fluorine antifouling agent (large A silicon-based antifouling agent and a fluorine-based antifouling agent were added and mixed such that Nippon Ink Co., Ltd. (Defenser TF3001) was 0.8% by mass of the total solid content to obtain a prism part composition. In addition, content (mass%) of the said silicon-type antifouling agent and a fluorine-type antifouling agent is a value when the mass of the whole solid content in the composition for prism parts obtained is made into 100%.
In the mat base material base formulation, silicon antifouling agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., UT3971) is 1% by mass of the total solid content, and fluorine antifouling agent (Dainippon Ink Co., Ltd.). A silicon-based antifouling agent and a fluorine-based antifouling agent were added and mixed so that the product, Defender TF3001) was 0.8% by mass of the total solid content, to obtain a mat layer material. In addition, content (mass%) of the said silicon | silicone type | system | group antifouling agent and fluorine-type antifouling agent is a value when the mass of the whole solid content in the material for mat | matte layers obtained is set to 100%.

The mat layer material described above was applied to one side of a 188 μm thick polyethylene terephthalate (PET) transparent substrate (trade name A4300, manufactured by Toyobo Co., Ltd.) to obtain a mat layer having a thickness of about 3 μm.
The above-described composition for a prism portion is supplied to a prism mold in which a concavo-convex shape of a linear arrangement of unit prisms (optical units) as shown in FIG. 1 is formed, and polyethylene terephthalate (PET) on the surface where no mat layer is provided The transparent base material is stacked, pressed with a nip roller, irradiated with ultraviolet light at 780 mJ / cm ² using a high-pressure mercury lamp, and the prism part (optical function developing part) having a large number of unit prisms is cured, The prism mold was peeled off in an integrated state to obtain an optical sheet.
Here, the shape of the unit prism (optical unit) was an isosceles triangular triangular prism having a main cut surface shape of height 25 μm, base 50 μm, and apex angle 90 °. The prism unit (optical function developing unit) has a structure in which a large number of unit prisms are arranged adjacent to each other in a direction orthogonal to the ridge line at an arrangement period of 50 μm so that the ridge lines of the unit prisms are balanced with each other.

When the silicon presence rate and the fluorine presence rate in the prism portion and the mat layer of the obtained optical sheet were measured by XPS analysis, the silicon presence rate in the optical function developing portion was 2%, and the fluorine presence rate was 2%. The silicon abundance ratio was 2% and the fluorine abundance ratio was 2%.
The XPS analysis uses an XPS (X-ray photoelectron spectroscopy) apparatus manufactured by Thermo Electron (VG Theta Probe), the X-ray source is Monochromated Al Kα, the X-ray output is 100 W, the measurement area is 400 μmφ, and the lens is Angle Resolved. The measurement angle was performed in five stages (28 °, 38 °, 48 °, 58 °, 68 °).

  The content (mass%) of the silicon antifouling agent when the total solid content in the prism part composition or mat layer material is 100%, and the silicon in the prism part or mat layer by XPS analysis. Table 2 shows the correlation with the abundance ratio (%), and the content (% by mass) of the fluorine-based antifouling agent when the total solid content in the prism portion composition or mat layer material is 100%. ) And the fluorine abundance ratio (%) in the prism portion or the mat layer by XPS analysis are shown in Table 3. In addition, Table 4 and Table 5 show the abundance ratios of silicon and fluorine by XPS analysis in the prism portion and the mat layer of the obtained optical sheet.

(Example 2)
The amount of the antifouling agent added to the prism part composition base formulation A is adjusted so that the silicon antifouling agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., UT3971) is 4% by mass of the total solid content, and Except having used the composition for prism parts obtained by making a fluorine-type antifouling agent (Dai Nippon Ink Co., Ltd., Defender TF3001) become 3 mass% of the whole solid content, it carried out similarly to Example 1, and using it. An optical sheet was obtained.

(Example 3)
The amount of the antifouling agent to be added to the mat layer material base prescription is such that the silicon antifouling agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., UT3971) is 4% by mass of the total solid content, and fluorine type. An optical sheet in the same manner as in Example 1, except that a mat layer material obtained by using an antifouling agent (Dai Nippon Ink Co., Ltd., Defender TF3001) at 3% by mass of the total solid content was used. Got.

(Examples 4 to 7)
In accordance with Tables 2 and 3, the prism-based composition base formulation A was mixed with a silicon-based antifouling agent (in accordance with Tables 2 and 3 so that the silicon presence rate and the fluorine presence rate by XPS analysis in the prism portion were the values shown in Table 4. Example 1 except that a composition for prism part containing Nippon Synthetic Chemical Industry Co., Ltd. (UT3971) and a fluorine-based antifouling agent (Dai Nippon Ink Co., Ltd., Defensor TF3001) was used. An optical sheet was obtained.

(Examples 8 to 11)
In accordance with Table 2 and Table 3, the anti-fouling agent (Nippon Gosei Co., Ltd.) was added to the mat layer material base formulation so that the silicon presence rate and the fluorine presence rate by XPS analysis in the mat layer were the values shown in Table 4. An optical sheet was obtained in the same manner as in Example 1 except that a mat layer material containing UT3971) manufactured by Chemical Industry Co., Ltd. and a fluorine-based antifouling agent (Dainippon Ink Co., Ltd., Defensor TF3001) was used. It was.

(Example 12)
An optical sheet was obtained in the same manner as in Example 1 except that the prism portion composition base formulation B was used instead of the prism portion composition base formulation A.

(Comparative Example 1)
An optical sheet was obtained in the same manner as in Example 1 except that the prism portion composition base formulation C was used instead of the prism portion composition base formulation A.

(Comparative Example 2)
The amount of antifouling agent to be added to the prism base composition base formulation A is 0.5% by mass of the silicon-based antifouling agent (1% abundance), and the fluorine antifouling agent is the total amount of solids. An optical sheet was obtained in the same manner as in Example 1 except that the prism part composition obtained so as to be 0.3% by mass (existence 1%) was used.

(Comparative Example 3)
The amount of antifouling agent added to the mat layer material base formulation is 0.5% by mass of the silicon-based antifouling agent (existence 1%), and the fluorine antifouling agent is 0. 0% of the total solid content. An optical sheet was obtained in the same manner as in Example 1 except that the mat layer material obtained so as to be 3% by mass (abundance 1%) was used.

(Comparative Example 4)
Instead of the prism part composition base formulation A, the prism part composition base formulation B is used, and the amount of antifouling agent added to the prism part composition base formulation B is determined based on the total solid content of the silicon-based antifouling agent. The composition for a prism part obtained so that 0.5 mass% (existence ratio 1%) of the fluorine-based antifouling agent was 0.3 mass% (existence ratio 1%) of the entire solid content was used. An optical sheet was obtained in the same manner as in Example 1 except that.

(Comparative Example 5)
Instead of the prism portion composition base formulation A, the prism portion composition base formulation C is used, and the amount of the antifouling agent added to the prism portion composition base formulation C is determined so that the silicon-based antifouling agent has a total solid content. Except for using the composition for a prism part obtained by 6 mass% (existence ratio 15%) of the above, and a fluorine-based antifouling agent obtained so that the total solid content is 5 mass% (existence ratio 15%), An optical sheet was obtained in the same manner as in Example 1.

(Measurement of indentation depth)
The indentation depth at the top of the prism portion (optical function developing portion) of the optical sheet obtained in each example and each comparative example was measured at an indentation load of 0.5 mN according to ISO 14577-1. As a measuring instrument, a microhardness tester (trade name: PICODETOR HM500, indenter made of diamond made of diamond, facing angle 90 °) manufactured by Fisher Instruments Co., Ltd. was used. The measurement results of the optical sheets obtained in the examples are shown in Table 4, and the measurement results of the optical sheets obtained in the comparative examples are shown in Table 5.

(Evaluation of presence of finger prints)
The produced optical sheets of Examples and Comparative Examples were cut into A4 size, and the presence or absence of finger marks on the prism portion surface and the mat layer surface was visually observed in a bright room. The evaluation results of the optical sheet obtained in the comparative example are shown in Table 4 with the evaluation result of the optical sheet obtained in the example shown in Table 4 as the one that could not recognize the finger mark and the one that could recognize the finger mark as x. Is shown in Table 5.

The optical sheet according to the present invention has been developed in order to solve the problem of finger marks adhering in the vicinity of the convex top of the optical unit constituting the optical function developing portion when the finger comes into contact.
In the optical sheets obtained in Examples 1 to 12, no finger trace was confirmed in any of the prism part (optical function developing part) and the mat layer (back surface layer). In the prism portion, an antifouling agent selected from silicon compounds and fluorine compounds is contained, and when the surface is subjected to XPS analysis, the total abundance of silicon atoms and fluorine atoms is 3% or more, so that sebum There is no adhesion, and further, by setting the indentation depth at an indentation load of 0.5 mN to 0.6 μm or more, it is considered that there was no permanent deformation due to pressurization, thereby preventing finger marks from adhering. The mat layer contains an antifouling agent selected from a silicon-based compound and a fluorine-based compound, and when the surface is subjected to XPS analysis, the total abundance of silicon atoms and fluorine atoms is 3% or more. It is thought that the adhesion of finger marks could be prevented by preventing the adhesion.
On the other hand, in the optical sheets obtained in Comparative Examples 1, 2, 4, and 5, finger marks were confirmed in the prism portion.
In Comparative Example 1, since the abundance ratio of silicon atoms and fluorine atoms on the surface of the prism part was the same as in the example, it is considered that sebum did not adhere, but the indentation depth at the prism part indentation load of 0.5 mN was Since it was as small as 0.4 micrometer, it is thought that the finger print was formed by pressurization.
In Comparative Example 2 and Comparative Example 4, since the indentation depth of the prism portion was the same as in the example, it is considered that there was no deformation due to pressurization, but the amount of antifouling agent contained in the prism portion was small, and silicon atoms and Since the total abundance of fluorine atoms was as small as 2%, it is considered that finger marks due to sebum adhered.
In Comparative Example 5, since the content of the antifouling agent in the prism portion was too much, finger stains adhered due to bleeding out of the antifouling agent, and gloss unevenness was formed on the surface of the prism portion. In addition, it is considered that finger traces due to pressurization were formed because the indentation depth at the indentation load of 0.5 mN of the prism portion was as small as 0.4 μm. In addition, since the presence rate of the silicon atom and the fluorine atom in the prism part surface was equivalent to the Example, it is thought that there was no adhesion of the finger trace by sebum.
In the optical sheet obtained in Comparative Example 3, finger marks were confirmed on the mat layer. This is because the amount of antifouling agent contained in the mat layer is small, and the total presence rate of silicon atoms and fluorine atoms when XPS analysis of the surface was as small as 2%, so it is considered that finger marks due to sebum adhered. .

DESCRIPTION OF SYMBOLS 10 Optical sheet 11 Transparent base material 12 Optical function expression part 12a Optical unit 13 Back surface layer 20 Surface light source device 21 Light guide plate 22 Light emission surface 23 Side end surface 24 Plateau 25 Light reflection plate 26 Surface light source 30 Liquid crystal display device 31 Liquid crystal cell 110 Movable Panel 120 Polarizing film 130 Load section

Claims (4)

On the one surface side of the transparent base material is an optical sheet provided with an optical function expression part in which a plurality of convex optical units having apexes or ridges are arranged,
The optical function developing part contains an antifouling agent selected from a silicon compound and a fluorine compound, and the total of silicon atoms and fluorine atoms when the surface is subjected to XPS analysis is 3% or more. And the indentation depth when measured by the indentation load of 0.5 mN based on ISO14577-1 in the top part of the optical unit is 0.6 micrometer or more, The optical sheet characterized by the above-mentioned.   The optical function developing part is (A) a (meth) acrylic resin having one (meth) acryloyl group as an active energy ray-curable group and (B) two (meth) acryloyl groups as an active energy ray-curable group. Antifouling selected from at least one selected from (meth) acrylic resin having (C) polyether-modified dimethylpolysiloxane, and (D) a compound represented by the following general formula (4), and a silicon compound and a fluorine compound A (meth) acrylic resin having a (meth) acryloyl group as the (A) active energy ray-curable group, and the (B) active energy. The total mass of the (meth) acrylic resin having two (meth) acryloyl groups as the linear curable group is the active energy. Is at least 50% by weight based on the total solid mass of the line curable resin composition, an optical sheet according to claim 1.
  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.