JP2011021114A - Ionizing radiation-curable resin composition for optical sheet, and optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet having excellent restorability and having a concavo-convex configuration hard to be scratched and an ionizing radiation-curable resin composition for forming such an optical sheet. <P>SOLUTION: The ionizing radiation-curable resin composition for an optical sheet comprises at least a phenoxyethyl (meth)acrylate, an ethylene oxide-modified and/or a propylene oxide-modified phenoxyethyl (meth)acrylate, and an ethylene oxide-modified and/or a propylene oxide-modified bisphenol A di(meth)acrylate. The optical sheet uses the ionizing radiation-curable resin composition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical sheet used as a prism sheet of a backlight for a liquid crystal display device, and an ionizing radiation curable resin composition for forming the optical sheet.

In recent years, with the rapid development of display technology such as liquid crystal display devices, there is an increasing demand for optical sheets used for the liquid crystal display devices having new functions and higher quality. As such an optical sheet, for example, a prism sheet used for a backlight of a liquid crystal display device, a lenticular lens sheet used for stereoscopic photography or a projection screen, and a Fresnel lens sheet used for a condenser lens of an overhead projector, The diffraction grating used for a color filter etc. can be mentioned.
The optical sheet usually has a substrate and a fine concavo-convex shape on the surface with a predetermined refractive index on the substrate, and the concavo-convex shape includes a plurality of unit concavo-convex structures such as unit prisms and unit lenses. Generally, it is formed by arranging. In addition, the optical sheet expresses a desired function by modulating light by a geometric optical action such as refraction and reflection, or a wave optical action such as diffraction in the uneven shape. The shape of the resin material constituting the concavo-convex shape and the unit concavo-convex structure is determined according to the above.

  Among the above optical members, for example, a prism sheet (optical sheet) used as a backlight of a liquid crystal display device, etc., is further disposed on the prism portion (uneven shape) of the optical sheet, and another optical sheet or diffusion plate Alternatively, a diffusion film is laminated and used. When manufacturing such a laminated body, the prism part of the said optical sheet may be worn out by an impact or a vibration.

  Further, the optical sheet is disposed on the light exit surface on the display panel side in both the edge light type surface light source device and the direct type surface light source device. In addition, the edge light type surface light source device usually enters light source light from one end face of a plate-like light guide such as a transparent acrylic resin, and the liquid crystal panel from a light exit surface that is one surface of the light guide. The direct-type surface light source device is a device in which a liquid crystal panel and a reflecting plate are arranged in a manner sandwiching the light source, and usually from the light source. Is reflected on the back surface of a liquid crystal panel or the like by a reflector.

When the prism portion included in the optical sheet is in contact with a light guide plate, a (light) diffusion film, or a liquid crystal display panel or other adjacent member that the surface light source device has, the heat and pressure applied in the process etc. There is a so-called “mountain collapse” problem that the top part of the unit prism is crushed, and further, there is a problem that the prism part and the light guide plate come into contact with each other and the top part of the unit prism is chipped.
Such a problem of deformation or chipping at the top of the unit prism causes display unevenness such as a white spot (white pattern) on the display surface of the display device, thereby degrading display performance.
In particular, when the concavo-convex shape has a sharp convex portion such as a prism, the above-described concavo-convex shape of wear, chipping, and crushing is remarkable. Of course, in the case of other concavo-convex optical sheets, there is a similar tendency to some extent.

In order to improve the above problems, conventionally, materials used for the prism portion have been used that have a high elastic modulus and the shape of the formed unit prism is difficult to deform (for example, Patent Document 1).
The optical article (optical sheet) comprising the ionizing radiation curable resin composition described in Patent Document 1 is a cured product that does not have a yield point in a stress-strain curve, and the applied stress is within the elastic limit. When released from stress, it is restored to its original shape by the elastic restoring force, and permanent distortion (deformation) does not occur.
However, when the stress applied to the optical article exceeds the elastic limit, there is a problem that the optical article is cracked.

On the other hand, the lens part (prism part) described in Patent Document 2 has specific physical properties, so that even if the unit prism attached to the surface of the prism part is deformed due to some external factor, the lens part (prism part) is based on this. Restorability that can be restored to the shape of is given, and it is possible to maintain the desired shape.
However, the resilience of the prism portion is not sufficient to solve the problem of deformation due to external force applied to the prism portion. In addition, since the restoration property is imparted, the prism portion is easily chipped, and the restoration property and the scratch resistance are not compatible.

Japanese Patent Laid-Open No. 9-61601 JP 2009-37204 A

  The present invention has been made in view of the above-mentioned problems, and has an excellent restorability and an optical sheet having an uneven shape that is difficult to be damaged, and an ionizing radiation curable resin for forming the optical sheet. An object is to provide a composition.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using an ionizing radiation curable resin composition for an optical sheet containing a specific component, and have completed the present invention. .
That is, the ionizing radiation curable resin composition for optical sheets according to the present invention includes at least phenoxyethyl (meth) acrylate represented by the following chemical formula (1), ethylene oxide-modified and / or propylene oxide represented by the following chemical formula (2). It includes a modified phenoxyethyl (meth) acrylate and an ethylene oxide-modified and / or propylene oxide-modified bisphenol A di (meth) acrylate represented by the following chemical formula (3).

(In the chemical formula (1), R ¹ is a hydrogen atom or a methyl group.)

(In the chemical formula (2), R ¹ and R ² are each independently a hydrogen atom or a methyl group, and k is a positive integer of 2 to 6.)

(In Formula (3), each R ¹ is independently a hydrogen atom or a methyl group. Each R ³ is independently a hydrogen atom or a methyl group, and n and m are n + m = 2 to 20, respectively. Is a positive integer chosen to be.)

The ionizing radiation curable resin composition for an optical sheet of the present invention includes phenoxyethyl (EO-modified) and / or propylene oxide-modified (PO-modified) phenoxyethyl having the above specific structure together with phenoxyethyl (meth) acrylate. By including the (meth) acrylate, the cured product is given flexibility, the cured product is hardly damaged, and even if the cured product is deformed by an external force applied, the original shape can be restored. Restorability can be imparted. In addition, the ionizing radiation curable resin composition contains bisphenol A di (meth) acrylate modified with ethylene oxide (EO modification) and / or propylene oxide (PO modification) having the specific structure together with the above components. Thereby, the softness | flexibility of hardened | cured material further increases and it can make the thing of the restoreability of the said hardened | cured material excellent.
Here, the EO-modified or PO-modified monomer (the EO-modified or PO-modified phenoxyethyl (meth) acrylate and the EO-modified or PO-modified bisphenol A di (meth) acrylate) are the original molecules. Since the molecular chain becomes longer and the freedom of movement of the molecule increases, the flexibility of the EO-modified or PO-modified monomer increases. Thereby, the ability to absorb or disperse the external force of the cured product is improved, and the cured product is considered to be hardly damaged.

In the ionizing radiation curable resin composition for optical sheets according to the present invention, the content of the phenoxyethyl (meth) acrylate is 15 to 30 weights with respect to the total weight of the ionizing radiation curable resin composition for optical sheets. % Is preferable from the viewpoint of improving adhesion to the substrate when a substrate such as surface-treated polyethylene terephthalate (PET) is used to support the cured product.
In addition, the total weight of the ionizing radiation curable resin composition usually means the total weight of solids not including a solvent, and when the ionizing radiation curable resin composition includes a solvent, the solvent is excluded. It means the total weight of the total solid content.

  In the ionizing radiation curable resin composition for an optical sheet according to the present invention, it is preferable to further contain orthophenylphenoxyethyl (meth) acrylate from the viewpoint of increasing the refractive index after curing.

  In the ionizing radiation curable resin composition for an optical sheet according to the present invention, it is preferable to further contain fluorenedin (meth) acrylate from the viewpoint of increasing the refractive index after curing and making it difficult to be damaged.

  In the ionizing radiation curable resin composition for an optical sheet according to the present invention, the refractive index after curing of the curable resin composition is preferably 1.56 or more from the viewpoint of improving luminance.

The optical sheet which concerns on this invention consists of hardened | cured material of the ionizing radiation-curable resin composition for optical sheets which concerns on this invention, and has an uneven | corrugated shape provided with several unit uneven structure.
The optical sheet of the present invention is not easily damaged, and has an excellent resilience that can be restored to the original shape even when the shape is deformed by applying external force to the uneven shape.
Therefore, according to the present invention, it is possible to provide an optical sheet capable of maintaining a desired shape without easily damaging the uneven shape.

In the optical sheet according to the present invention, the concavo-convex equilibrium elastic modulus (80 ° C., 1 Hz) measured by dynamic viscoelasticity measurement is less than 2.0 × 10 ⁷ Pa and the glass transition temperature (Tg). It can be set to 10 ° C. or higher and 40 ° C. or lower.

The ionizing radiation curable resin composition for an optical sheet of the present invention is excellent in resilience that the cured product is hardly damaged and can be restored to its original shape even when the cured product is deformed by an external force. Can be granted.
Moreover, the optical sheet of this invention cannot maintain the shape of uneven | corrugated shape easily, and can maintain a desired shape.

It is the schematic which shows an example of the optical sheet of this invention. It is the schematic which shows an example of the optical sheet of this invention. It is a figure which shows the apparatus for measuring a restoring property and a damage property. 4 (a) to 4 (d) are schematic views of an optical sheet for illustrating a method for evaluating restorability and scratchability. It is a perspective view which shows an example of a surface light source device provided with the optical sheet of this invention. It is a schematic perspective view which shows an example of a liquid crystal display device provided with the surface light source device shown in FIG.

The present invention is described in detail below.
In the present invention, (meth) acrylate represents acrylate and / or methacrylate.
1. Ionizing radiation curable resin composition for optical sheets The ionizing radiation curable resin composition for optical sheets according to the present invention is a resin that is cured by ionizing radiation typified by ultraviolet rays or electron beams. 1) phenoxyethyl (meth) acrylate represented by the following chemical formula (2), ethylene oxide-modified and / or propylene oxide-modified phenoxyethyl (meth) acrylate, and ethylene oxide represented by the following chemical formula (3) It contains bisphenol A di (meth) acrylate modified and / or modified with propylene oxide.

(In the chemical formula (1), R ¹ is a hydrogen atom or a methyl group.)

(In the chemical formula (2), R ¹ and R ² are each independently a hydrogen atom or a methyl group, and k is a positive integer of 2 to 6.)

(In Formula (3), each R ¹ is independently a hydrogen atom or a methyl group. Each R ³ is independently a hydrogen atom or a methyl group, and n and m are n + m = 2 to 20, respectively. Is a positive integer chosen to be.)

  The phenoxyethyl (meth) acrylate represented by the chemical formula (1) is contained in the ionizing radiation curable resin composition in order to enhance the adhesion of the resin, and the content thereof is the total weight of the ionizing radiation curable resin composition. The content is preferably 15 to 30% by weight, more preferably 20 to 30% by weight, and particularly preferably 22 to 27% by weight. If it is less than 15% by weight, when using a substrate for supporting a cured product, particularly a polyester resin substrate represented by polyethylene terephthalate, the adhesion to the substrate may be impaired, exceeding 30% by weight. In this case, there is a risk that predetermined physical properties such as viscosity and recoverability cannot be maintained.

The EO-modified and / or PO-modified phenoxyethyl (meth) acrylate represented by the chemical formula (2) is contained in the ionizing radiation curable resin composition together with the phenoxyethyl (meth) acrylate. Flexibility is imparted to the cured product of the ionizing radiation curable resin composition, the cured product is less likely to be scratched, and can be restored to its original shape even when an external force is applied to the cured product and the shape is deformed. Can be provided with a high level of resilience.
In the above chemical formula (2), k is a positive integer of 2 to 6, and preferably a positive integer of 2 to 4, more preferably a positive integer of 2 to 3, from the viewpoint of enhancing the flexibility of the cured product. is there.

  The content of the EO-modified and / or PO-modified phenoxyethyl (meth) acrylate is preferably 5 to 20% by weight, more preferably 5 to 15% by weight based on the total weight of the ionizing radiation curable resin composition. %, Preferably 5 to 10% by weight. If it is less than 5% by weight, the restoring property may be impaired. If it exceeds 20% by weight, the prism ridge may be scraped or worn.

Further, the EO-modified and / or PO-modified bisphenol A di (meth) acrylate represented by the chemical formula (3) is contained in the ionizing radiation curable resin composition together with the above two components, so that the ionizing radiation can be obtained. The flexibility of the cured product of the curable resin composition is further increased, and the restorability of the cured product can be improved.
In the above chemical formula (3), n and m are positive integers selected so that n + m = 2 to 20. Examples of the individual values of n and m, and combinations of both are, for example, n = 1, m = 1, n + m = 2, n = 1, m = 3, n + m = 4, n = 2, m = 2. n + m = 4, n = 4, m = 6, n + m = 10, n = 2, m = 8, n + m = 10, n = 5, m = 5, n + m = 10, n = 8, m = 12, n + m = 20, n = 10, m = 10, and n + m = 20. Further, from the viewpoint of enhancing the flexibility of the cured product, n and m are preferably selected such that n + m = 2 to 12, and more preferably n + m = 4 to 10.

  The content of the EO-modified and / or PO-modified bisphenol A di (meth) acrylate is preferably 25 to 50% by weight, more preferably 30 to 45%, based on the total weight of the ionizing radiation curable resin composition. It is preferable that it is weight%, and it is preferable that it is 35 to 45 weight% especially. If it is less than 25% by weight, there is a risk of scraping the tip of the concavo-convex part such as a prism ridge line and wearing it.

  Further, the phenoxyethyl (meth) acrylate represented by the chemical formula (1) and the EO-modified and / or PO-modified phenoxyethyl represented by the chemical formula (2) contained in the ionizing radiation curable resin composition of the present invention. The total amount of (meth) acrylate and EO-modified and / or PO-modified bisphenol A di (meth) acrylate represented by the chemical formula (3) is based on the total weight of the ionizing radiation curable resin composition. It is preferably 45 to 80% by weight, more preferably 55 to 75% by weight, and particularly preferably 65 to 75% by weight. By setting the total amount of the essential components within the above range, predetermined physical properties such as viscosity, restorability, and adhesion can be obtained.

  When the ionizing radiation curable resin composition of the present invention has a refractive index of 1.56 or more after being cured, a prism sheet as shown in FIG. 1 is formed from the cured product of the resin composition, as shown in FIG. In the case of use in a form incorporated in a surface light source device, it is preferable from the viewpoint of improving luminance. From the viewpoint of setting the refractive index to a high refractive index of 1.56 or more, the ionizing radiation curable resin composition preferably contains orthophenylphenoxyethyl (meth) acrylate. When the ionizing radiation curable resin composition contains orthophenylphenoxyethyl (meth) acrylate, the content thereof may be 5 to 25% by weight with respect to the total weight of the ionizing radiation curable resin composition. It is preferably 8 to 15% by weight. If the amount is less than 5% by weight, the luminance may be lowered. If the amount is more than 25% by weight, predetermined physical properties such as recoverability and scratch resistance may not be maintained.

In addition, the ionizing radiation curable resin composition of the present invention preferably contains a full orange (meth) acrylate having high curing reactivity in order to make the cured product difficult to be damaged. When the ionizing radiation curable resin composition contains full orange (meth) acrylate, the content thereof is preferably 5 to 20% by weight with respect to the total weight of the ionizing radiation curable resin composition, Further, it is preferably 5 to 15% by weight, and particularly preferably 7 to 13% by weight. If the amount is less than 5% by weight, the predetermined refractive index may not be obtained. If the amount exceeds 20% by weight, predetermined physical properties such as viscosity and recoverability may not be maintained.
Further, since full orange (meth) acrylate has an effect of increasing the refractive index after curing, it is used in combination with the above orthophenylphenoxyethyl (meth) acrylate to increase the refractive index after curing without impairing the adhesion. be able to. From such a point of view, the content of fluorange (meth) acrylate is preferably 30 to 180 parts by weight, more preferably 50 to 150 parts by weight with respect to 100 parts by weight of orthophenylphenoxyethyl (meth) acrylate. In particular, the amount is preferably 80 to 130 parts by weight.

Moreover, the ionizing radiation curable resin composition of the present invention may contain a polyfunctional monomer in order to impart an appropriate hardness to the cured product.
Examples of the polyfunctional monomer include dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, ethylene oxide-modified isocyanuric acid tri (meth) acrylate, pentaerythritol tri (meth) acrylate, penta Examples include erythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide-modified or propylene oxide-modified trimethylolpropane tri (meth) acrylate, and the like.
Further, the content of the polyfunctional monomer is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, especially 0 based on the total weight of the ionizing radiation curable resin composition. It is preferably ˜3% by weight. If it exceeds 10% by weight, the cured product may become too hard and the restorability may be impaired.
In addition, when the ionizing radiation curable resin composition does not contain the polyfunctional monomer, it contains the full orange (meth) acrylate having a high curing reactivity in order to give the cured product appropriate hardness and make it difficult to be damaged. It is preferable to do.

  The ionizing radiation curable resin composition of the present invention can contain a photopolymerization initiator as an optional component when the composition is cured with ultraviolet rays or visible rays. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopro Pan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-hydroxy-2-methyl-1-phenyl-propane-1-ketone, 2,4 , 6-trimethylbenzoyldiphenylphosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) -phosphine oxide, etc. It is. These can be used alone or in combination of two or more. The addition amount of the photopolymerization initiator is about 0.1 to 5% by weight with respect to the total weight of the ionizing radiation curable resin composition.

(Other ingredients)
In addition to the above components, the ionizing radiation curable resin composition of the present invention contains silicone, antioxidant, polymerization inhibitor, thickener, mold release agent, antistatic agent, UV stabilizer, UV absorber, A foaming agent, a solvent, a non-reactive acrylic resin, a non-reactive urethane resin, a non-reactive polyester resin, a pigment, a dye, a diffusing agent, and the like can be used in combination.
The ionizing radiation curable resin composition of the present invention is usually the total amount of the above-mentioned essential components contained in the ionizing radiation curable resin composition and components that form a matrix of the optical sheet after curing other than the essential components. However, it is appropriately prepared so as to be usually 90% by weight or more with respect to the total weight of the ionizing radiation curable resin composition.

2. Optical sheet The optical sheet according to the present invention is made of a cured product of the ionizing radiation curable resin composition for optical sheets according to the present invention, and has an uneven shape formed by arranging a plurality of unit uneven structures on the surface thereof. Features.
The optical sheet of the present invention is not easily damaged, and has an excellent resilience that can be restored to the original shape even when the shape is deformed by applying external force to the uneven shape.
Therefore, according to the present invention, it is possible to provide an optical sheet capable of maintaining a desired shape without easily damaging the uneven shape.
In addition, the optical sheet is roughly classified according to its action mechanism, such as a prism sheet or a lens sheet, and the like, in a concavo-convex shape, light is modulated by geometric optical action such as refraction and reflection, and condensed. Those that exhibit desired functions such as diffusion, refraction, and reflection, and those that exhibit desired functions such as diffraction and spectroscopy by modulating wave optics such as diffraction, such as diffraction gratings and holograms There is.
Among these, specific shapes (structures) of the prism sheet are exemplified. A prismatic unit prism (unit uneven structure) such as a triangular prism (see FIG. 1), a quadrangular prism, a pentagonal prism, etc. ) Arranged in a direction orthogonal to) (prism linear array), triangular pyramid (or triangular frustum), quadrangular pyramid (or quadrangular frustum), or circular pyramid (or frustum), etc. A unit in which a large number of prisms (pedestal) or conical (pedestal) unit prisms are arranged in two directions on the surface of the transparent substrate is mentioned.
In addition, when a specific shape (structure) of the lens sheet is exemplified, a unit lens (unit uneven structure) having a curved column shape such as a semi-cylindrical or semi-elliptical column is arranged in a direction perpendicular to the ridge line direction (extending direction). Multiple arrayed lenses (lenticular lens), hemisphere, or spheroid half-curved unit lenses (unit uneven structure) arrayed in multiple directions on the surface of the transparent substrate (amber eye lens) ) Or an annular or linear Fresnel lens.
In the following, a typical example of the prism sheet in which unit prisms are arranged will be described in detail.

FIG. 1 is a schematic view showing an example of the optical sheet of the present invention. The optical sheet 1 of the present invention has a prism portion 2 composed of a plurality of triangular prism unit prisms 3 on one surface. The prism unit 2 is a prism group in which a large number of unit prisms 3 are arranged so that their ridge lines are parallel. The optical sheet 1 having the prism portion 2 can be used in a single-sheet configuration, but in order to control the light diffusion angle in two directions (vertical direction, left and right direction), two optical sheets having the prism portion 2 are used. 1 may be laminated so that the ridgelines are orthogonal. In this case, the direction of the prism surface (prism top) of the prism unit 2 is the same in both directions because it has the highest light transmittance, but the prism tops of the prism unit 2 face each other. You may comprise.
Further, the structure of the unit prism 3 is not particularly limited as long as it can exhibit an optical function. For example, the structures of the various structures described above are also used.
In addition, the thickness from the prism top part of the prism part 2 to the plane part 2a (surface on the side where the prism part of the optical sheet does not exist) is usually about 20 to 1000 μm.
In FIG. 1 and FIG. 2, the unit prism has an isosceles triangle in the shape of the main cutting plane (cross section orthogonal to the ridgeline), but it may be an unequal triangle depending on the required optical characteristics. . The value of the apex angle of the triangle on the main cutting plane is 90 degrees in the example of FIG. 1, but various values can be taken within a range of about 40 to 120 degrees depending on the required characteristics.
1 and 2, the apex of the prism forms an ideal triangular prism having a sharp point, but the main cutting plane may be configured so that the vicinity of the apex is a circle having a radius of curvature of about 1 to 10 μm. Such a shape can mechanically and geometrically distribute stress concentrated on the top and reduce top deformation and chipping. Therefore, this form of shape is preferable in view of improving the scratch resistance and restoring property in combination with the action of the ionizing radiation curable resin composition specific to the present invention.

The prism portion 2 of the present invention can have an equilibrium elastic modulus (80 ° C., 1 Hz) measured by dynamic viscoelasticity measurement of less than 2.0 × 10 ⁷ Pa. Equilibrium modulus of the prism portion 2 (80 ℃, 1Hz) is more preferably in the range of ^{0.5 × 10 7 Pa~1.7 × 10 7} Pa, more preferably 0.8 × ¹⁰ 7 Pa to It is in the range of 1.7 × 10 ⁷ Pa. By setting the equilibrium elastic modulus (80 ° C., 1 Hz) of the prism portion 2 to less than 2.0 × 10 ⁷ Pa, the prism portion (optical sheet) of the present invention is excellent in shape restoration. it can.

  In addition, the prism portion 2 of the present invention has a maximum value of loss tangent (tan δ), which is a ratio of loss elastic modulus (E ″) and storage elastic modulus (E ′) measured by dynamic viscoelasticity measurement, to 0.6. The maximum value of the loss tangent (tan δ) of the prism portion 2 is more preferably in the range of 0.7 to 3.0, and still more preferably in the range of 0.8 to 2. The maximum value of the loss tangent (tan δ) of the prism portion 2 is in the range of 0.6 to 3.0, so that the glass transition temperature (Tg) of the prism portion 2 is 10 C. to 40 ° C., more preferably 10 ° C. to 30 ° C., and even more preferably 15 ° C. to 28 ° C. By setting the glass transition temperature (Tg) within the above range, Change the shape of the prism unit (optical sheet) unit prism It can be excellent in wear resistance of things.

Here, the equilibrium elastic modulus (80 ° C., 1 Hz), loss tangent (tan δ), and glass transition temperature (Tg) can be measured with a dynamic viscoelasticity measuring apparatus. In the dynamic viscoelasticity measuring apparatus, the storage elastic modulus (E ′) corresponding to elasticity, the loss elastic modulus (E ″) corresponding to viscosity, and the ratio of E ″ and E ′, which reflects vibration absorption The temperature dependence, frequency dependence, etc. of the tangent (tan δ) can be measured, and the glass transition caused by the intramolecular structure of the cured resin constituting the prism part 2 (the top part of the unit prism 3) is determined based on the measurement result. Temperature (Tg), equilibrium elastic modulus, etc. can be evaluated. In the present invention, measured at a tensile sine wave and a frequency of 1 Hz, the temperature showing the maximum value of the loss tangent (tan δ) is the glass transition temperature (Tg), and the storage elastic modulus (E ′) at 80 ° C. is the equilibrium elastic modulus. did.
As the dynamic viscoelasticity measuring device, “Viscoelastic Spectrometer” (trade name) manufactured by SII Nano Technology Co., Ltd. and “Rheogel E4000” (trade name) manufactured by UBM Co., Ltd. are used. Can be mentioned.

Since the prism part (optical sheet) of the present invention has the specific physical properties described above, the shape of the unit prism included in the prism part is not easily damaged, and a desired shape can be maintained.
The restoration property and scratch resistance of the prism portion can be evaluated by the following methods.
That is, as shown in FIG. 3, a test piece 12 (prism portion) is set on the movable platen 11 of the abrasion resistance tester, and the load portion 14 is placed on the test piece 12 via a polarizing film 13 having an area of 12 cm ^2. Apply a load of 250 g. The bottom surface of the load portion is a donut shape having an outer diameter of 20 mm and an inner diameter of 10 mm, and the bottom area is 2.36 cm ² . The state of the top of the test piece 12 (prism portion) when the movable platen 11 is moved in one direction for 20 seconds in the direction of the arrow in FIG. Evaluate by observation. An example of the measuring apparatus is “AB-301 Gakushin Type Friction Fastness Tester” (trade name) manufactured by Tester Sangyo Co., Ltd.

In addition, the evaluation criteria of resilience and scratch resistance are as follows.
[Restorability evaluation]
Evaluation 5: No deformation of the shape was confirmed by microscopic observation (with a magnification of 100 to 1000).
Evaluation 4: Although deformation of the shape was confirmed by microscopic observation (with a magnification of 100 to 1000), it was not visually confirmed on the backlight.
Evaluation 3: Although visually confirmed on the backlight, it was restored to its original shape within 10 minutes at room temperature (25 ° C.).
・ Evaluation 2: Although visually confirmed on the backlight, it was not restored to its original shape within 10 minutes at room temperature (25 ° C.), but when heated to 35 ° C., it was restored to its original shape within 5 minutes. Has been restored.
・ Evaluation 1: Although it was visually confirmed on the backlight, it was not restored to its original shape within 5 minutes after heating at 35 ° C., but it was restored to its original shape when heated at 80 ° C. for 1 minute. .
[Scratch resistance evaluation]
Evaluation 5: No scratch was observed by microscopic observation (with a magnification of 100 to 1000).
Evaluation 4: One flaw was confirmed by microscopic observation (with a magnification of 100 to 1000), 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.
The microscope observation is performed by appropriately adjusting the magnification of the microscope within a range of 100 to 1000 times.

Here, the restoration property evaluation 3 and the scratch resistance evaluation 5 are, for example, after the depression of the width L of the polarizing film 13 is formed on the top of the unit prism of the test piece 12 (prism portion) (FIG. 4A )), A case where the prism shape is restored to the original shape within 10 minutes at room temperature (25 ° C.), and no scratches are confirmed by microscopic observation (FIG. 4B). The restoration evaluation 3 and the scratch resistance evaluation 3 are smaller than the width L of the polarizing film 13 and the recess L of the polarizing film 13 at the top of the unit prism of the test piece 12 (prism portion), for example. After the width l is formed (FIG. 4C), the prism shape is restored to the original shape within 10 minutes at room temperature (25 ° C.), but remains on the surface near the top of the prism without being restored. 2 to 3 scratches are formed, and the scratches are visually confirmed on the backlight (FIG. 4D).
In addition, the restoration property evaluation of the prism portion of the present invention is preferably an evaluation of 3 or more, more preferably an evaluation of 4 or more, and particularly preferably an evaluation of 5 or more. Further, the scratch resistance evaluation of the prism portion is preferably an evaluation of 3 or more, more preferably an evaluation of 4 or more, and particularly preferably an evaluation of 5 or more.

The prism portion 2 of the present invention can exhibit a specific function in combination with the shape of the unit prism 3 by having a desired refractive index. Therefore, the refractive index of the prism portion 2 is
Depending on the use of the optical sheet of the present invention, the relationship with the shape of the unit prism 3 is not particularly limited as long as it is within a range in which a desired function can be expressed, but is usually 1.50 or more. Is preferable, and it is further preferable to be within the range of 1.50 to 1.60. When the refractive index of the prism portion 2 is within the above range, for example, when the optical sheet of the present invention is used as a prism sheet of a backlight for a liquid crystal display device, the viewing angle and the luminance of the liquid crystal display device can be compatible. Thus, it becomes easy to control the shape of the unit prism 3.

(Other layers)
In the optical sheet of the present invention, as shown in FIG. 2, a transparent substrate 4 that supports the prism portion 2 is provided on the surface of the optical sheet 1 opposite to the surface on which the plurality of unit prisms 3 are formed. May be.
The transparent base material 4 acts as a base material for the prism portion 2 and acts to transmit most of the light from the light source to the prism portion 2 side. The transparent base material 4 may be a light-transmitting base material made of a resin material, and in particular, a base material having a transmittance of 85% or more is preferably used.
Although the thickness of the transparent base material 4 is not specifically limited, Usually, it exists in the range of 50-500 micrometers which can be rolled.

  As the transparent substrate 4, for example, a transparent substrate composed of a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, an acrylic resin such as polymethyl methacrylate, a polycarbonate resin, or a polystyrene resin can be preferably exemplified.

  The optical sheet 1 of the present invention can be provided with a light diffusion function. For example, as shown in FIG. 2, the light diffusing function is provided by providing a light diffusing layer 5 on at least one surface of the transparent base material 4, or so-called mat treatment (formation of light diffusing fine irregularities). ).

  The light diffusing layer 5 illustrated in FIG. 2 is an arbitrary layer that is preferably provided, and may have any function of diffusing light, and is formed on a general light diffusing sheet. For example, a layer in which light diffusing fine particles are dispersed in a translucent resin can be applied. The light diffusion layer 5 may be provided on the surface S2 opposite to the prism forming surface of the transparent substrate 4, or between the prism-side surface S1 of the transparent substrate 4 and the prism portion 2 (illustrated). May not be provided).

As translucent resin which comprises the light-diffusion layer 5, resin similar to said transparent base material 4 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 the light diffusion layer 5 is usually in the range of 1 to 20 μm.

(Use of optical sheet)
Examples of the optical sheet of the present invention include a prism sheet used for a backlight of a liquid crystal display device or the like, a Fresnel lens sheet or a lenticular sheet used for a projection screen such as a projection television. The optical sheet of 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>
FIG. 5 is a perspective view showing an example of a surface light source device including the optical sheet of the present invention. The surface light source device 20 of FIG. 5 is a so-called edge light type surface light source device, and a light guide 22 that emits light introduced from at least one side end surface 22A from a light emission surface 22B as one surface; The light source 24 is provided on the light emitting surface 22B of the light guide 22 through, for example, a (light) diffusion film 21, and the light is emitted. The optical sheet 1 according to the present invention, which transmits light emitted from the surface 22B, is provided.

  The light guide 22 is a plate-like body made of a translucent material, and is configured to emit light introduced from the left side end surface 22A in FIG. 5 from the upper light emission surface 22B. The light guide 22 is made of a light-transmitting material similar to the material of the optical sheet 1, but is usually made of acrylic or polycarbonate resin. The thickness of the light guide 22 is usually about 1 to 10 mm, and the thickness may be constant over the entire range, or as shown in FIG. 5, it is the thickest at the position of the side end face 22A on the light source 24 side. The taper shape may be gradually thinned in the opposite direction. In order to emit light from a wide surface (light emission surface 22B), the light guide 22 preferably has a light scattering function added to the inside or the surface thereof.

The light source 24 causes light to enter the inside from at least one side end face 22 </ b> A of the light guide 22, and is disposed along the side end face 22 </ b> A of the light guide 22. The light source 24 is not limited to a linear light source as shown in FIG. 5, and a point light source such as an incandescent bulb or LED (light emitting diode) may be arranged in a line along the side end face 22A. . A plurality of small flat fluorescent lamps may be arranged along the side end face 22A.
When the apex angle of the unit prism is less than 80 degrees, the prism portion 2 side is arranged in the direction facing the light guide 22 side, contrary to the case of FIG.

  On the light emission surface 22 </ b> B of the light guide 22, the above-described optical sheet 1 according to the present invention is provided, for example, via a (light) diffusion film 21. The optical sheet 1 is provided so that the opposite surface of the prism portion 2 becomes the light emission surface 22B of the light guide 22.

  The light reflecting plate 26 is provided on a surface opposite to the light emitting surface 22B of the light guide 22 and is provided on a side end surface other than the side end surface 22A, and reflects light emitted from these surfaces to reflect the light. 22 for returning to the inside. As the light reflecting plate 26, a thin metal plate deposited with aluminum or the like, or white foamed PET (polyethylene terephthalate) is used.

<Display device>
6 is a schematic perspective view illustrating an example of a liquid crystal display device including the edge light type surface light source device illustrated in FIG. A liquid crystal display device 30 shown in FIG. 6 is a liquid crystal panel 32 that is a flat light-transmitting display, and an edge light type surface light source that is disposed on the back surface of the liquid crystal panel 32 and that irradiates the liquid crystal panel 32 from the back surface. Device 20. The liquid crystal display device 30 is a so-called backlight type liquid crystal display device, and is configured to illuminate each pixel forming a liquid crystal screen from the back side with light emitted from the surface light source device 20.

  Since the liquid crystal display device 30 includes the surface light source device 20 including the optical sheet according to the present invention as a constituent member, the display surface does not cause display unevenness such as a white spot (white pattern) and is stable and good. Display performance can be provided.

  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 exhibits the same function and effect. Are included in the technical scope.

  Hereinafter, the present invention will be described more specifically with reference to examples. These descriptions do not limit the present invention.

Example 1
On a PET film having a thickness of 125 μm (Lumirror T-60: trade name, manufactured by Toray Industries, Inc.), a resin composition 1 having a composition shown in Table 1 below was applied so that the thickness of the coating film was 150 μm. Using a mercury soot, the resin composition 1 was irradiated with ultraviolet rays at 780 mJ / cm ² to cure the coating film. Then, the coating film of the said resin composition 1 was peeled from the said PET film, and this was made into the sample for dynamic viscoelasticity evaluation.

(Examples 2-6 and Comparative Examples 1-2)
Samples for dynamic viscoelasticity evaluation of each example and comparative example were prepared in the same manner as in Example 1 using resin compositions 2 to 8 having the compositions shown in Table 1 below.

＊１）フェノキシエチルアクリレート（ＳＲ３３９Ａ：商品名、サートマー社製）
＊２）フェノキシエチルアクリレート（ＥＯ２モル変性）（ライトアクリレート Ｐ−２００Ａ：商品名、共栄社化学（株）製）
＊３）アクリロイルモルホリン（ＡＣＭＯ：商品名、（株）興人製）
＊４）イソボルニルアクリレート（ライトアクリレート ＩＢ−ＸＡ：商品名、共栄社化学（株）製）
＊５）オルトフェニルフェノキシエチルアクリレート（ＮＫエステル Ａ−ＬＥＮ−１０：商品名、新中村化学工業（株）製）
＊６）オルトフェニルフェノキシエチルアクリレート（ＭＩＲＡＭＥＲ Ｍ１１４２：商品名、ＭＩＷＯＮ社製）
＊７）ビスフェノールＡジアクリレート（ＥＯ４モル変性）（ライトアクリレート ＢＰ−４ＥＡ：商品名、共栄社化学（株）製）
＊８）ビスフェノールＡジアクリレート（ＥＯ１０モル変性）（ＭＩＲＡＭＥＲ Ｍ２１００：商品名、ＭＩＷＯＮ社製）
＊９）ビスフェノールＡジメタクリレート（ＥＯ２モル変性）（ライトアクリレート ＢＰ−２ＥＭ：商品名、共栄社化学（株）製）
＊１０）フルオレンジアクリレート（オグソール Ｆ−５５０３：商品名、大阪ガスケミカル（株）製）
＊１１）フルオレンジアクリレート（オグソール Ｆ−５０１０：商品名、大阪ガスケミカル（株）製）
＊１２）ジペンタエリスリトールヘキサアクリレート（カプロラクトン２モル変性）（ＫＡＹＡＲＡＤ ＤＰＣＡ−２０：商品名、日本化薬（株）製）
＊１３）イソシアヌル酸トリアクリレート（ＥＯ３モル変性）（アロニックス Ｍ−３１５：商品名、東亞合成（株）製）
＊１４）ビスフェノールＡエポキシジアクリレート（分子量２０００）（ＦＬＥＡ−ＰＯＡ（全重量に対するビスフェノールＡエポキシジアクリレートの含有量４９重量％、フェノキシエチルアクリレートの含有量５１重量％）：商品名、共栄社化学（株）製）
＊１５）フェノキシレジン（ＰＡＰＨＥＮ ＰＫＨＪ：商品名、インケム社製）
＊１６）１−ヒドロキシシクロヘキシルフェニルケトン（ＩＲＧＡＣＵＲＥ１８４：商品名、チバ・ジャパン株式会社製）
＊１７）２，４，６−トリメチルベンゾイルジフェニルホスフィンオキサイド（ルシリンＴＰＯ：商品名、ＢＡＳＦ社製）
＊１８）有機シリコーン（ＫＦ６１８：商品名、信越化学工業（株）製）

* 1) Phenoxyethyl acrylate (SR339A: trade name, manufactured by Sartomer)
* 2) Phenoxyethyl acrylate (EO 2 mol modified) (Light acrylate P-200A: trade name, manufactured by Kyoeisha Chemical Co., Ltd.)
* 3) Acryloylmorpholine (ACMO: trade name, manufactured by Kojin Co., Ltd.)
* 4) Isobornyl acrylate (Light acrylate IB-XA: trade name, manufactured by Kyoeisha Chemical Co., Ltd.)
* 5) Orthophenylphenoxyethyl acrylate (NK ester A-LEN-10: trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.)
* 6) Orthophenylphenoxyethyl acrylate (MIRAMER M1142: trade name, manufactured by MIWON)
* 7) Bisphenol A diacrylate (EO4 mol modified) (Light acrylate BP-4EA: trade name, manufactured by Kyoeisha Chemical Co., Ltd.)
* 8) Bisphenol A diacrylate (EO 10 mol modified) (MIRAMER M2100: trade name, manufactured by MIWON)
* 9) Bisphenol A dimethacrylate (EO 2 mol modified) (Light acrylate BP-2EM: trade name, manufactured by Kyoeisha Chemical Co., Ltd.)
* 10) Full orange acrylate (Ogsol F-5503: trade name, manufactured by Osaka Gas Chemical Co., Ltd.)
* 11) Full orange acrylate (Ogsol F-5010: trade name, manufactured by Osaka Gas Chemical Co., Ltd.)
* 12) Dipentaerythritol hexaacrylate (caprolactone 2 mol modified) (KAYARAD DPCA-20: trade name, manufactured by Nippon Kayaku Co., Ltd.)
* 13) Isocyanuric acid triacrylate (EO 3 mol modified) (Aronix M-315: trade name, manufactured by Toagosei Co., Ltd.)
* 14) Bisphenol A epoxy diacrylate (molecular weight 2000) (FLEA-POA (bisphenol A epoxy diacrylate content 49% by weight, phenoxyethyl acrylate content 51% by weight based on the total weight): trade name, Kyoeisha Chemical Co., Ltd. ) Made)
* 15) Phenoxy resin (PAPHEN PKHJ: trade name, manufactured by Inchem)
* 16) 1-hydroxycyclohexyl phenyl ketone (IRGACURE 184: trade name, manufactured by Ciba Japan Co., Ltd.)
* 17) 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO: trade name, manufactured by BASF)
* 18) Organic silicone (KF618: trade name, manufactured by Shin-Etsu Chemical Co., Ltd.)

(Evaluation)
(1) Dynamic viscoelasticity evaluation Dynamic viscoelasticity evaluation was performed using each sample produced in Examples 1-6 and Comparative Examples 1-2. The evaluation was performed using a dynamic viscoelasticity measuring apparatus (manufactured by SII Nano Technology, model number: DMS6100) under the conditions of a tension sine wave, a frequency of 1 Hz, a strain amplitude of 0.05%, and a heating rate of 3 ° C./min. The maximum value of loss tangent (tan δ), glass transition temperature (Tg), and equilibrium elastic modulus (80 ° C., 1 Hz) were measured. The results are shown in Table 2.

(Example 7)
After dropping the resin composition 1 having the composition shown in Table 1 above onto a prism mold having a linear arrangement of unit prisms, a polyethylene terephthalate substrate (PET, trade name: A4300, thickness: 125 μm Toyobo) Made by Co., Ltd.) and the entire surface of the PET was pressure-bonded to the resin composition 1 with a laminator.
Next, the resin composition 1 was irradiated with ultraviolet rays at 780 mJ / cm ² using a mercury soot to cure the prism portion having a large number of unit prisms and integrated with the polyethylene terephthalate substrate. Then, the optical sheet of Example 7 was obtained by peeling the prism type.
Here, the unit prism has a triangular prism shape. More specifically, the main cut surface of the unit prism has an isosceles triangle shape with a height of 25 μm, a base of 50 μm, and an apex angle of 90 °. A plurality of unit prisms 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 unit prisms are in equilibrium with each other, and the surface has a concavo-convex shape of the prism linear array. A prism type was obtained.

(Examples 8-12 and Comparative Examples 3-4)
Using the resin compositions 2 to 8 having the compositions shown in Table 1 above, optical sheets of the respective examples and comparative examples were produced in the same manner as in Example 7.

(Evaluation)
(2) Refractive index The optical sheet obtained above was cut into a length of 20 mm and a width of 10 mm as a test piece. Using a refractometer (trade name: NAR-1T SOLID, manufactured by ATAGO) for the refractive index of the test piece, the test piece temperature was 25 ° C., and the D line (λ = 589 nm) of the sodium atom spectrum was JIS K7105. Measured according to.
(3) Restorability and scratch resistance The test piece 12 was obtained by cutting the optical sheet obtained above into a length of 150 mm and a width of 40 mm. Abrasion testing machine shown in FIG. 3 (trade name: AB-301, tester Ltd.) on the surface of the movable platen 10 side of the loading section 14 of the lower polarizing film 13 of the area 12cm ² (trade name: H25, The surface opposite to the mat layer of Dai Nippon Printing Co., Ltd. was faced and fixed so that the lower polarizing film 13 was wound around the load portion 14. Next, the test piece 12 (prism portion) was placed on the movable plate 11 so that the top portion of the test piece 12 (prism portion) faces the load portion 14 side. A load of 250 g is applied to the load portion 14 so that the mat layer of the lower polarizing film 13 is rubbed against the top of the test piece 12 (prism portion), and the movable platen 11 is moved in a single direction for 20 seconds with a moving distance of 100 mm. After moving under the condition of a speed of 5 mm / s, the state of the top of the test piece 12 (prism part) was observed by visual observation and microscopic observation (digital microscope VHX-200N, manufactured by Keyence Corporation). In addition, the evaluation criteria of resilience and scratch resistance are as follows. The results are shown in Table 3.
[Restorability evaluation]
Evaluation 5: No deformation of the shape was confirmed by microscopic observation (magnification 500).
Evaluation 4: Although deformation of the shape was confirmed by microscopic observation (magnification 500), it was not visually confirmed on the backlight.
Evaluation 3: Although visually confirmed on the backlight, it was restored to its original shape within 10 minutes at room temperature (25 ° C.).
Evaluation 2: Although visually confirmed on the backlight, it was not restored to its original shape within 10 minutes at room temperature (25 ° C.), but when heated to 35 ° C., it was restored to its original shape within 5 minutes. Has been restored.
・ Evaluation 1: Although it was confirmed visually on the backlight, it was not restored to its original shape within 5 minutes after heating at 35 ° C., but it was restored to its original shape when heated at 80 ° C. for 1 minute. .
[Scratch resistance evaluation]
Evaluation 5: No scratch was confirmed by microscopic observation (magnification 500).
Evaluation 4: One flaw was confirmed by microscopic observation (magnification 500), 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.

(Summary of results)
From Tables 2 and 3 above, phenoxyethyl (meth) acrylate, ethylene oxide modified (EO modified) phenoxyethyl (meth) acrylate having a specific structure, and ethylene oxide modified (EO modified) having a specific structure were obtained. In Examples 7 to 12 using the resin compositions 1 to 6 containing bisphenol A di (meth) acrylate, the evaluation of restorability was 5. Moreover, in Examples 7-12, evaluation of damage resistance improved by increasing content of the bisphenol A di (meth) acrylate which modified | denatured 10 mol of ethylene oxide contained in a resin composition.
On the other hand, in Comparative Example 3 using the resin composition 7 not containing phenoxyethyl (meth) acrylate modified with 2 moles of ethylene oxide, the evaluation of resilience was 2, and the evaluation of scratch resistance was 2. Further, in Comparative Example 4 using the resin composition 8 not containing phenoxyethyl (meth) acrylate modified with 2 moles of ethylene oxide, the evaluation of restoration property was 1, and the evaluation of scratch resistance was 1.

DESCRIPTION OF SYMBOLS 1 Optical sheet 2 Prism part 2a Plane part 3 Unit prism 4 Transparent base material 5 Light diffusion layer 10 Measuring apparatus 11 Movable board 12 Test piece (prism part)
DESCRIPTION OF SYMBOLS 13 Polarizing film 14 Load part 16 Scratch 20 Surface light source device 21 (Light) diffusion film 22 Light guide 22A Side end surface 22B Light emission surface 24 Light source 26 Light reflector 30 Liquid crystal display device 32 Liquid crystal panel S1 One surface of a transparent substrate S2 The other side of the transparent substrate

Claims (7)

At least phenoxyethyl (meth) acrylate represented by the following chemical formula (1), ethylene oxide-modified and / or propylene oxide-modified phenoxyethyl (meth) acrylate represented by the following chemical formula (2), and the following chemical formula (3) An ionizing radiation curable resin composition for an optical sheet comprising the bisphenol A di (meth) acrylate modified with ethylene oxide and / or propylene oxide.

(In the chemical formula (1), R ¹ is a hydrogen atom or a methyl group.)

(In the chemical formula (2), R ¹ and R ² are each independently a hydrogen atom or a methyl group, and k is a positive integer of 2 to 6.)

(In Formula (3), each R ¹ is independently a hydrogen atom or a methyl group. Each R ³ is independently a hydrogen atom or a methyl group, and n and m are n + m = 2 to 20, respectively. Is a positive integer chosen to be.)   2. The ionizing radiation curable composition for an optical sheet according to claim 1, wherein the content of the phenoxyethyl (meth) acrylate is 15 to 30 wt% with respect to the total weight of the ionizing radiation curable resin composition for an optical sheet. Resin composition.   The ionizing radiation curable resin composition for an optical sheet according to claim 1, further comprising orthophenylphenoxyethyl (meth) acrylate.   The ionizing radiation-curable resin composition for an optical sheet according to any one of claims 1 to 3, further comprising a full orange (meth) acrylate.   The ionizing radiation-curable resin composition for an optical sheet according to any one of claims 1 to 4, wherein the refractive index after curing of the curable resin composition is 1.56 or more.   The optical sheet which consists of hardened | cured material of the ionizing radiation-curable resin composition for optical sheets as described in any one of Claims 1 thru | or 5, and has an uneven | corrugated shape provided with several unit uneven | corrugated structure. The equilibrium elastic modulus (80 ° C., 1 Hz) of the concavo-convex shape measured by dynamic viscoelasticity measurement is less than 2.0 × 10 ⁷ Pa, and the glass transition temperature (Tg) is 10 ° C. or more and 40 ° C. or less. The optical sheet according to claim 6.

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