JP5556039B2 - Prism sheet - Google Patents

Description

  The present invention relates to a prism sheet.

  2. Description of the Related Art In liquid crystal display devices such as notebook computers and mobile phones, surface light emission is used on the back side of a liquid crystal display surface to cause light to enter a light guide plate to emit light. In such a liquid crystal display device, a prism sheet for concentrating and emitting light from a surface light source in a specific direction is used in order to use light obtained from the light source more efficiently.

For example, as shown in FIG. 3, a back having a reflection sheet 101, a light guide plate 102, and a prism sheet 105 placed in order, and having a light source 103 and a light source reflection film 104 on the side surface of the light guide plate 102. A light system 100 is used.
In this backlight system 100, light emitted from the light source 103 is incident on the light guide plate 102 by the light source reflection film 104 and aligned in a certain direction by the prism sheet 105, and then the liquid crystal display surface is turned on.
In the prism sheet 105, a unit prism or a lens is formed on one surface of a translucent base material, and a light diffusion layer is provided on the other surface. In the liquid crystal display device described above, the prism surface of the prism sheet 105 is placed in contact with the light guide plate 102.

In recent years, liquid crystal display devices have been increasingly carried and used as typified by mobile phones and mobile personal computers. For this reason, it is often assumed that the liquid crystal display device is vibrated or strongly pressed, and the prism sheet 105 may be damaged such as scratches. In addition, when the prism sheet 105 is brought into direct contact with a liquid crystal panel having irregularities formed on the back surface, the prism sheet 105 is more easily damaged. If the light diffusing layer of the prism sheet 105 is damaged, it causes deterioration in quality such as a decrease in luminance and a non-uniform surface emission state.
In order to improve durability of a surface light source lens film in which a lens layer and a mat layer are integrated with respect to such a problem, a surface light source lens film using an ultraviolet curable resin is disclosed. (For example, patent document 1).
Further, an invention is disclosed in which damage is prevented by forming an uneven light diffusing layer on the surface of an optical sheet by adding particles or the like (for example, Patent Document 2).
Furthermore, in order to reduce the thickness and weight of the liquid crystal display device, it is required to reduce the thickness of the prism sheet. In reducing the thickness of the prism sheet, warpage of the prism sheet becomes a problem. In order to solve such a problem, a prism sheet using an active energy ray-curable resin is disclosed (for example, Patent Document 3).

Japanese Patent No. 3827832 Japanese Patent No. 3913870 International Publication No. 2006/041089 Pamphlet

However, when an uneven surface is formed with particles on the diffusion surface of the prism sheet, there is a possibility that the particles will fall off due to rubbing. When particles on the diffusion surface fall off, the dropped particles rub the sheet itself and cause scratches, resulting in a decrease in luminance and quality. In addition, the use of particles in the light diffusion layer has a problem in that the quality of the display such as speckles and texture spots is reduced due to aggregation of the particles themselves.
On the other hand, in order to form an uneven surface in the light diffusion layer without adding particles and to give scratch resistance, the resin must be thinned unless the resin permeability to the uneven pattern forming surface is appropriate. There was also a problem that could not be achieved. And even if the prism sheet is made thin, it is required to prevent warping.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a prism sheet that has excellent scratch resistance, prevents deterioration of luminance and quality, and does not warp even when it is thinned.

The prism sheet of the present invention is a prism sheet having a light diffusion layer having a prism layer on one surface of the translucent base material and an uneven surface formed on the other surface of the translucent base material. And the light diffusion layer is obtained from an active energy ray-curable resin composition having the following components (a) to (d) as main components, the viscosity at 50 ° C. being 200 mPa · s or less. .
Component (a): aliphatic urethane (meth) acrylate compound having a structure derived from pentaerythritol and / or dipentaerythritol and 9 or more polymerizable double bond groups (30 to 60 parts by mass)
(B) Component: (meth) acrylate compound (5 to 55 parts by mass) having two (meth) acryloyl groups having no urethane bond and having a molecular weight of 500 or more and a tan δ peak of the cured product of less than 70 ° C.
(C) Component: An aliphatic compound (5 to 50 parts by mass) having a viscosity at 25 ° C. of 50 mPa · s or less.
(D) Component: A polymerization initiator.
[However, the sum of the component (a), the component (b), and the component (c) is 100 parts by mass. ]
The cured product of the active energy ray-curable resin composition preferably has a loss tangent tan δ peak temperature of 60 ° C. or higher, and a tensile elastic modulus at 25 ° C. of 2.7 GPa or higher.

  According to the prism sheet of the present invention, it is excellent in scratch resistance, prevents deterioration in luminance and quality, and can prevent warping even when it is thinned.

It is sectional drawing which shows one Embodiment of the prism sheet of this invention. It is a schematic diagram which shows one Embodiment of the manufacturing apparatus used for implementation of this invention. It is a perspective view which shows an example of a backlight system.

An example of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a prism sheet 10 showing an example of an embodiment of the present invention.
As shown in FIG. 1, the prism sheet 10 has a prism layer 20 formed on one surface of a translucent substrate 14. The prism layer 20 is configured by arranging a plurality of triangular prism-shaped prism rows 18 in one direction at a predetermined pitch on the intermediate layer 16. On the surface of the translucent substrate 14 opposite to the surface on which the prism layer 20 is formed, the light diffusion layer 12 having irregularities on the surface is formed.

(Light diffusion layer)
The shape of the uneven surface formed on the surface of the light diffusion layer 12 is not particularly limited, and can be determined according to the material of the contacted object on the surface of the light diffusion layer 12 and the degree of diffusion required for the prism sheet 10. . For example, the arithmetic average roughness Ra can be 0.05 to 2.0 μm, and the 10-point average roughness Rz can be 0.5 to 10 μm.
Moreover, although the thickness of the light-diffusion layer 12 is not specifically limited, For example, it is preferable to determine in the range of 1-12 micrometers. If it is thinner than 1 μm, it becomes difficult to transfer the diffusion structure, and if it is thicker than 12 μm, the amount of the resin composition used increases, so that it is not possible to satisfy the demand for thinning, and the flexibility of the sheet is lowered. is there.

  The active energy ray-curable resin composition of the light diffusing layer 12 is a fat having a structure derived from component (a): pentaerythritol and / or dipentaerythritol, and nine or more polymerizable double bond groups. Group urethane (meth) acrylate compound (30 to 60 parts by mass) and (b) component: two (meth) acryloyl groups having no urethane bond and having a molecular weight of 500 or more and a tan δ peak of the cured product of less than 70 ° C. (Meth) acrylate compound (5 to 55 parts by mass), (c) component: aliphatic compound (5 to 50 parts by mass) having a viscosity at 25 ° C. of 50 mPa · s or less, and (d) component: polymerization And a viscosity at 50 ° C. of 200 mPa · s or less. In addition, the viscosity in this invention means the value measured with the B-type viscometer.

<(A) component>
The component (a) is an aliphatic urethane (meth) acrylate having a structure derived from pentaerythritol and / or (di) pentaerythritol and nine or more polymerizable double bond groups. The component (a) is a component that causes a polymerization reaction or a cross-linking reaction by irradiating active energy such as ultraviolet rays in the presence of a radical polymerizable photopolymerization initiator and the like. Gives sex. As the component (a), for example, those obtained by reacting the component (a1): a triisocyanate compound and the component (a2): (di) pentaerythritol are preferable.

  As the component (a1), either alicyclic aliphatic or aliphatic may be used. For example, hexamethylene diisocyanate (HDI), cyclic trimer of HDI, and the like can be mentioned. As the component (a1), one type may be used alone, or two or more types may be used in combination.

  The component (a2) is not particularly limited, and examples thereof include pentaerythritol triacrylate (PETA) and dipentaerythritol pentaacrylate. The component (a2) can be used alone or in combination of two or more.

  The reaction between the component (a1) and the component (a2) can be easily carried out by heating at 60 to 100 ° C. using a tin-based compound such as dibutyltin dilaurate as a catalyst. . Since the component (a) to be obtained generally has a high viscosity, a reactive diluent such as (meth) acrylate having a low viscosity that does not directly participate in the reaction may be used during the synthesis.

  Examples of the component (a) thus obtained include mixtures of aliphatic urethane (meth) acrylates represented by the following structural formulas (1) to (7). By using such a component (a), excellent scratch resistance and heat resistance can be imparted to the resulting cured product.

  (A) In the structure of a component, it is preferable that the molar ratio of the hydroxyl group with respect to an isocyanate group exists in the range of 1.0-1.5. If this molar ratio is 1.0 or more, the remaining unreacted isocyanate groups in the resin composition can be reduced, and the storage stability can be improved. Moreover, if this molar ratio is 1.5 or less, content of an unreacted hydroxyl-containing compound can be reduced and the physical property of hardened | cured material can be strengthened.

  The compounding amount of the component (a) in the active energy ray-curable resin is 30 to 60 parts by mass, preferably 40 to 55 parts by mass with respect to 100 parts by mass in total of the components (a) to (c). If it is less than the lower limit of the above range, the desired tensile elastic modulus of the cured product cannot be obtained, and the prism sheet 10 may be warped on the prism surface side. Further, the desired tan δ peak cannot be obtained, and there is a possibility that sufficient heat resistance cannot be imparted to the cured product of the active energy ray-curable resin composition (hereinafter sometimes referred to as a resin composition). When the upper limit of the above range is exceeded, the viscosity of the resin composition becomes high and thin film molding becomes difficult.

<(B) component>
The component (b) is a (meth) acrylate compound having two (meth) acryloyl groups having no urethane bond and having a molecular weight of 500 or more and a cured product having a tan δ peak of less than 70 ° C. The component (b) is a component that causes a polymerization reaction or a crosslinking reaction by irradiation with active energy rays such as ultraviolet rays in the presence of a radical polymerizable photopolymerization initiator. Furthermore, it is a component for mainly improving the moldability of the light-diffusion layer 12, and providing a softness | flexibility and abrasion resistance by mixing with (a) component.

As the component (b), for example, aliphatic di (meth) acrylate having a molecular weight of 500 or more, hydrogenated bisphenol A, or F-based di (meth) acrylate is preferable. For example, di (meth) acrylate of polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polybutylene glycol, caprolactone-modified di (meth) acrylate of hydroxypivalic acid neopentyl glycol ester, ethylene oxide of hydrogenated bisphenol A has an addition number of 4 Examples include di (meth) acrylate having a mole or more and di (meth) acrylate having an addition number of ethylene oxide of hydrogenated bisphenol F of 4 moles or more.
Among them, di (meth) acrylate of polybutylene glycol, di (meth) acrylate having an addition number of ethylene oxide of hydrogenated bisphenol A, and di (meth) having an addition number of ethylene oxide of hydrogenated bisphenol F of 6 mol or more. Acrylate is preferable in terms of adjusting the tensile elastic modulus of the cured product of the resin composition.

  Furthermore, the compounds represented by the following general formulas (I) and (II) are preferable in that they do not lower the scratch resistance of the light diffusion layer 12.

As the component (b), one type may be used alone, or two or more types may be used in combination.
Although the compounding quantity of (b) component in an active energy ray curable resin composition is not specifically limited, It is 5-55 mass parts with respect to a total of 100 mass parts of (a)-(c) component, 10-40 A mass part is preferable and 15-35 mass parts is more preferable. If it is less than the lower limit of the above range, the effect of reducing the viscosity of the active energy ray-curable resin composition may not appear, and further, the toughness of the cured product is lowered and the effect of improving scratch resistance is sufficient. May not develop. When the upper limit of the above range is exceeded, the tensile modulus of the cured product becomes too low, and in the preferable thickness range of the light diffusion layer 12 (1 to 12 μm), the prism sheet 10 is warped on the prism surface side. This is because there is a fear.

<(C) component>
The component (c) is an aliphatic compound having a viscosity at 25 ° C. of 50 mPa · s or less. The component (c) is a component that decreases the viscosity of the active energy ray-curable resin composition. (C) As a component, for example, as diacrylate, hydroxypivalate neopentyl glycol diacrylate (HPN), polyethylene glycol 200 diacrylate (PE-200), polyethylene glycol 300 diacrylate (PE-300), polyethylene glycol 400 diacrylate (PE-400), polypropylene glycol 400 diacrylate (PP-400), 1,6-hexanediol diacrylate (HDDA), 2-ethyl-2butyl-propanediol diacrylate (C9A), 1,9 -Nonanediol diacrylate (L-C9A), neopentyl glycol diacrylate (NPA), tricyclodecane dimethanol diacrylate (DCP), etc. are mentioned.
Examples of the compound containing both acrylate and methacrylate include 2-hydroxy-3-acryloxypropyl methacrylate (G201P).

As the component (c), one type may be used alone, or two or more types may be used in combination.
(C) The compounding quantity of a component is 5-50 mass parts with respect to a total of 100 mass parts of (a)-(c) component, Preferably it is 10-45 mass parts. When the blending amount of the component (c) is less than the lower limit value of the above range, the viscosity of the resin composition becomes too high, and when the blending amount exceeds the upper limit value of the above range, it occupies the resin composition of the component (a) and the component (b). This is because the ratio is lowered and the effect of improving the heat resistance and scratch resistance of the cured product is not sufficiently exhibited.

<(D) component>
The component (d) is a polymerization initiator. The component (d) is specifically a photopolymerization initiator or a thermal polymerization initiator. Examples of the photopolymerization initiator include benzophenone, 4,4-bis (diethylamino) benzophenone, 2,4,6-trimethylbenzophenone, methyl orthobenzoylbenzoate, 4-phenylbenzophenone, t-butylanthraquinone, 2-ethylanthraquinone, Thioxanthone such as 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone; diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl- Such as phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone Tophenone; benzoin ether such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4- Examples include acylphosphine oxides such as trimethylpentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; methylbenzoylformate, 1,7-bisacridinylheptane, and 9-phenylacridine. Moreover, you may use a commercially available photoinitiator. These may be used alone or in combination of two or more.

  When using a thermosetting reaction, examples of the thermal polymerization initiator include methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxy octoate, t -Organic peroxides such as butyl peroxybenzoate and lauroyl peroxide; azo compounds such as azobisisobutyronitrile; N, N-dimethylaniline, N, N-dimethyl-p-toluidine as the organic peroxide And redox polymerization initiators combined with amines such as A commercially available thermal polymerization initiator may be used. These may be used alone or in combination of two or more.

The photopolymerization initiator and thermal polymerization initiator described above may be used alone or in combination.
(D) The compounding quantity of a component is not specifically limited, Preferably it is 0.01-10 mass parts with respect to a total of 100 mass parts of (a)-(c) component, More preferably, it is 0.05-5 mass parts. Particularly preferred is 0.1 to 4 parts by mass. When the blending amount of the component (d) is less than the lower limit of the above range, there is a possibility that sufficient curability by the active energy ray of the active energy ray-curable resin composition cannot be obtained. If the upper limit of the above range is exceeded, the light diffusing layer 12 may be colored yellow, or the adhesion to the substrate may be lowered.

<(E) component: other components>
Furthermore, the active energy ray-curable resin composition of the light diffusing layer 12 includes, as necessary, component (e): antistatic agent, antioxidant, ultraviolet absorber, light stabilizer, leveling agent as other components. In addition, various additives such as a heat stabilizer, a coating material modifier, a flame retardant, a polymerization inhibitor, a photopolymerization accelerator, a sensitizer, and a release agent may be contained.
(E) The compounding quantity of a component will not be specifically limited if it is a range which does not affect the essential hardening of this invention. For example, it is preferably 0 to 10 parts by mass, more preferably 0 to 4 parts by mass with respect to 100 parts by mass of the total amount of the components (a) to (c).

  The viscosity at 50 ° C. of the active energy ray-curable resin composition of the light diffusion layer 12 in the present invention is 200 mPa · s or less, preferably 30 to 150 mPa · s. This is because when the viscosity at 50 ° C. exceeds 200 mPa · s, it is not possible to reduce the thickness when the light diffusion layer 12 is laminated.

  The tan δ peak of the cured product of the active energy ray-curable resin composition of the light diffusion layer 12 is not particularly limited, but is preferably 60 ° C. or higher. This is because when the tan δ peak is 60 ° C. or higher, the heat resistance of the cured product of the active energy ray-curable resin composition can be improved.

  The cured product of the active energy ray-curable resin composition of the light diffusion layer 12 preferably has a tensile elastic modulus of 2.7 GPa or more. This is because, when the tensile elastic modulus is 2.7 GPa or more, the warp prevention effect of the prism sheet 10 is further improved even when the light diffusion layer is made thinner.

(Translucent substrate)
The translucent substrate 14 is not particularly limited as long as it transmits active energy rays. For example, a film made of a resin such as an acrylic resin, a polycarbonate resin, a polyester resin, a vinyl chloride resin, or a polymethacrylimide resin, Sheets, plates, etc. can be used. In addition, other treatments such as antistatic, antireflection, and adhesion prevention between substrates can be performed. The thickness of the translucent base material 14 is not specifically limited. It is considered that the warp of the prism sheet 10 can be reduced as the thickness of the translucent substrate 14 is increased. However, since the prism sheet 10 having a small thickness is generally required, the thickness of the translucent substrate 14 is preferably, for example, 50 to 200 μm. Further, the translucent substrate 14 may have a surface treatment portion for improving the adhesion with the prism layer 20. Examples of the surface treatment include those having easy adhesion made of polyester resin, acrylic resin, urethane resin, and the like. Moreover, what roughened the surface of the translucent base material 14 may be used.

(Prism layer)
The prism layer 20 includes an intermediate layer 16 and a prism array 18. Although the thickness of the prism layer 20 is not specifically limited, For example, it is preferable to determine in the range of 15-100 micrometers. This is because when the value is less than the lower limit of the above range, the reproducibility of the prism shape becomes difficult, and when the value exceeds the upper limit of the above range, the prism pitch becomes large, and moire occurs due to interference with the pixel pitch of the liquid crystal panel.

<Prism array>
The shape of the prism row 18 is not particularly limited, and can be appropriately determined according to the performance required for the prism sheet 10. For example, in a prism sheet for a high-brightness backlight, it is preferable that the height of the prism row 18 is about 15 to 75 μm, the prism apex angle is about 45 to 75 °, and the pitch of the prism row 18 is about 10 to 70 μm.

  The material of the prism row 18 is not particularly limited. For example, the prism row 18 is made of an active energy ray-curable resin and has a refractive index of about 1.48 to 1.6. The active energy ray-curable resin for forming the prism array is not particularly limited as long as it is cured with active energy rays such as ultraviolet rays and electron beams. For example, polyesters, epoxy resins, polyesters ( Examples include (meth) acrylate resins such as (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate. Among these, (meth) acrylate resins are particularly preferable from the viewpoint of optical characteristics and the like. Such an active energy ray-curable resin composition includes a polyfunctional acrylate and / or a polyfunctional methacrylate (hereinafter referred to as polyfunctional (meth) acrylate), a monoacrylate and / or a polyfunctional acrylate in terms of handleability and curability. Or what has a photopolymerization initiator by a monomethacrylate (henceforth mono (meth) acrylate) and an active energy ray as a main component is preferable. Typical polyfunctional (meth) acrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These are used alone or as a mixture of two or more. Examples of mono (meth) acrylates include mono (meth) acrylates of monoalcohols and mono (meth) acrylates of polyols.

<Intermediate layer>
The material of the intermediate layer 16 is the same as that of the prism row 18.
The thickness of the intermediate layer 16 only needs to have a sufficient volume that can reduce the deformation of the prism array 18 due to curing shrinkage, and is preferably determined in the range of 1 to 15 μm, for example.

(Production method)
The manufacturing method of the prism sheet 10 of the present invention includes the light-transmitting base material containing the component (a), the component (b), the component (c), and the component (d). Applying the active energy ray-curable resin composition having a viscosity at 50 ° C. of 200 mPa · s or less, and the active energy ray-curable resin composition applied to the translucent substrate to the light diffusion layer. A step of pressing a surface on which a concavo-convex pattern corresponding to the concavo-convex shape is formed, and a step of irradiating an active energy ray through the translucent substrate to cure and shape the active energy ray-curable resin composition It has.
An example of the manufacturing method of the prism sheet 10 of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram showing an example of a prism sheet manufacturing apparatus used for carrying out the present invention. This manufacturing method is a method of forming irregularities on the surface of the light diffusion layer 12 with a cylindrical mold.
The manufacturing apparatus 40 includes a mold roll 46, a nip roll 48, a fixed roll 49, an active energy ray light source 50, and a tank 42. The tank 42 is provided with a nozzle 44. The nip roll 48 is installed such that the axial direction of the nip roll 48 and the axial direction of the mold roll 46 are parallel to each other, and an arbitrary gap is provided between the nip roll 48 and the mold roll 46. A fixed roll 49 is arranged on the secondary side of the mold roll 46. The active energy ray light source 50 is disposed so that the peripheral surface of the mold roll 46 can be irradiated with energy rays.

  The mold roll 46 is a cylindrical roll having an uneven pattern on the surface corresponding to the unevenness on the surface of the light diffusion layer 12. Examples of the concavo-convex pattern include those formed directly on the surface of a cylindrical object, and those obtained by winding and fixing a thin plate on which a concavo-convex pattern is formed around a core roll. The material of the mold roll 46 is not particularly limited. For example, the mold roll 46 is made of a metal mold such as aluminum, brass, or steel, and is made of a synthetic resin such as a silicone resin, a urethane resin, an epoxy resin, an ABS resin, a fluorine resin, or a polymethylpentene resin. Examples of the mold include those obtained by plating these materials and those obtained by mixing various metal powders. In particular, a metal mold is preferable in terms of heat resistance and strength, and is suitable for continuous production. More specifically, the metal mold has advantages such as being resistant to polymerization heat generation, hardly deforming, hardly scratched, temperature controllable, and suitable for precision molding.

The active energy ray emission source 50 is not particularly limited, and includes a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp (manufactured by Fusion UV System), a visible light halogen lamp, a xenon lamp, and sunlight. Can be used.
The material of the nip roll 48 is not particularly limited, and examples thereof include a rubber material.

The translucent substrate 14 is wound around the nip roll 48 and the mold roll 46, and transferred so as to be wound along the peripheral surface of the mold roll 46. And it is wound around the fixed roll 49 arrange | positioned at the secondary side of the type | mold roll 46. FIG. During this time, the active energy ray-curable resin composition 54 is injected from the nozzle 44 between the translucent substrate 14 and the peripheral surface of the mold roll 46. At this time, the nip roll 48 presses the translucent substrate 14 in the direction of the mold roll 46, and an arbitrary tension is applied to the translucent substrate 14 by the nip roll 48 and the fixing roll 49, thereby translucent The substrate 14 is transferred while being pressed with a constant force on the peripheral surface of the mold roll 46. For this reason, the film thickness of the active energy ray-curable resin composition injected into the gap between the mold roll 46 and the nip roll 48 is made uniform. The active energy ray curable resin composition 54 is held between the mold roll 46 and the translucent substrate 14 and enters the concavo-convex pattern forming surface of the mold roll 46, while the active energy ray light source 50. Is irradiated with active energy rays. The active energy ray passes through the translucent substrate 14 and is irradiated to the active energy ray curable resin composition 54. In this way, the active energy ray curable resin composition 54 is cured to form the sheet 56 in which the unevenness of the surface of the light diffusion layer 12 is formed and the light diffusion layer 12 is formed on the translucent substrate 14. The sheet 56 is transferred along the peripheral surface of the fixed roll 49 while changing the traveling direction while being wound up.
Next, by providing the prism layer 20 on the surface of the obtained sheet 56 opposite to the surface on which the light diffusing layer 12 is provided, the prism sheet 10 having the light diffusing layer 12 on which the unevenness is formed is manufactured. Can do.

  The “application step” corresponds to the above-described step of “injecting the active energy ray-curable resin composition 54 from the nozzle 44”. In the “step of pressing the surface”, “the nip roll 48 presses the translucent substrate 14 in the direction of the mold roll 46” and “the translucent substrate 14 is fixed on the peripheral surface of the mold roll 46”. "Pressing with force" corresponds. The “step of curing and shaping” corresponds to the above-mentioned “irradiation of active energy rays from the active energy ray emission source 50 in a state of entering the concave / convex pattern forming surface of the mold roll 46”.

The atmosphere at the time of active energy ray irradiation may be air or an inert gas such as nitrogen or argon. The irradiation energy is not particularly limited, but the accumulated energy in the wavelength range of 200 to 600 nm, preferably 320 to 390 nm is, for example, 0.1 to 10 J / cm ² , preferably 0.5 to 8 J / cm ^2. Irradiation is preferred. The irradiation time of the active energy ray is determined by the illuminance of the light source used and the necessary irradiation amount of the active energy ray-curable resin, but is preferably determined in the range of 0.1 to 10 seconds from the viewpoint of productivity.

  The method for providing the prism layer 20 is not particularly limited, and for example, a method similar to that for the light diffusion layer 12 described above can be used. Specifically, the shape pattern of the prism row 18 is formed on the surface of the mold roll 46, and the active energy ray-curable resin composition 54 is changed to a resin used for the prism layer 20, and the same method as the light diffusion layer 12 is performed. Can be formed.

  The manufacturing method of the prism sheet 10 is particularly a method in which an active energy ray-curable resin composition is applied between the light-transmitting substrate 14 and is cured and shaped while pressing on the surface on which the concavo-convex pattern is formed. Without being limited thereto, the active energy ray-curable resin may be applied to the translucent substrate 14 or may be applied directly to the mold. Moreover, you may use a type | mold like the above-mentioned type | mold roll 46, and apply | coated the active energy ray-curable resin composition to the translucent base material 14 mounted in the horizontal surface, and the board which engraved the uneven | corrugated pattern It may be cured and shaped while pressing with a shaped mold. In addition, the active energy ray-curable resin composition is applied to the translucent base material 14 cut to the desired size of the prism sheet 10, and is cured and shaped while pressing with a mold in which an uneven pattern is engraved. A batch method may be adopted.

According to the present invention, the active energy which has (a) component, (b) component, (c) component, and (d) component in a light-diffusion layer, and the viscosity in 50 degreeC is 200 mPa * s or less. By using the linear curable resin composition, high scratch resistance can be exhibited. Moreover, since it does not contain particles, it is possible to prevent the occurrence of damage due to missing particles and the deterioration of quality such as speckles and texture spots due to aggregation of particles. In addition, it is possible to obtain a prism sheet that does not warp even when it is thinned.
Furthermore, heat resistance can be improved by setting the tan δ peak of the cured product of the active energy ray-curable resin composition to 60 ° C. By setting the tensile elastic modulus of the cured product of the active energy ray-curable resin composition to 2.7 GPa or more, it is possible to further prevent warpage.
According to the present invention, the active energy which has (a) component, (b) component, (c) component, and (d) component in a light-diffusion layer, and the viscosity in 50 degreeC is 200 mPa * s or less. A prism sheet can be easily produced by applying a linear curable resin composition to a light-transmitting substrate, pressing a mold having a concavo-convex pattern, and irradiating active energy rays.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, it is not limited to an Example.
(Evaluation means)
<Evaluation of scratch resistance>
For the abrasion resistance test, a 5 mm square PET film (thickness: 188 μm) is attached to the center of the head of the smooth type friction element of the dyeing friction fastness tester (model RT-200, manufactured by Daiei Chemical Seiki Co., Ltd.). A 15 mm square anti-glare type polarizing film was attached so as to cover the concave and convex surface. A glass plate having a thickness of 2 mm is fixed to the test table, and the light diffusion layer of the prism sheet is attached to the surface of the glass plate. The state of the diffusion layer was visually evaluated. The case where damage was confirmed was rated as x, and the case where damage was not confirmed was marked as o.

<Evaluation of warpage>
The produced prism sheet was cut into a vertical direction of 195 mm and a width of 309 mm with the direction perpendicular to the prism ridge line direction as a test piece. The test piece was left in an environment of 60 ° C. and a relative humidity of 30% for 4 hours with the prism surface facing up. The amount of warpage was measured by placing on a flat stage in an environment of 23 ° C. and 50% relative humidity, observing the vertical distances of the four corners from the stage surface using a microscope, and evaluating the average value. When there was no prism warp or when the degree of warp was small, the same measurement was performed with the prism surface down for confirmation. The warp was marked as “+” on the prism side and “−” on the light diffusion layer side.

<Evaluation of tensile modulus, loss tangent (tan δ) peak>
<< Preparation of test piece >>
Two glass molds having a mirror finish on the inner surface and two 70 mmφ glass molds were arranged at an interval of 200 μm, and the periphery was surrounded by polyester tape to produce a mold. Then, an active energy ray-curable resin composition is injected into the mold, and ultraviolet rays of 1000 mJ / cm ² are cast by a conveyor type UV irradiation device (10 inch D bulb, manufactured by Fusion UV Systems Japan Co., Ltd.). The cured product of the plate-shaped resin composition was obtained.

<< Measurement of tensile modulus and tan δ peak >>
By the following method, the tan δ peak is obtained from the tan δ profile as the tensile elastic modulus as the dynamic elastic modulus E ′. A test piece was prepared by cutting a cured product of a plate-like resin composition into a length of 30 mm and a width of 10 mm. The dynamic elastic modulus E ′ is measured using a dynamic viscoelasticity measuring device (DMS6100, manufactured by Seiko Instruments Inc.) under the conditions of a tensile mode, a frequency of 10 Hz, a heating rate of 3 ° C./min, and a sampling rate of 15 seconds. went.

<Measurement of viscosity>
The viscosity was measured for the resin composition at 50 ° C. with a B-type viscometer (TVB-10, Toki Sangyo Co., Ltd., rotor No. 10) using a small amount of adapter.

(Production Example 1) Production of light diffusing layer A die roll having a diameter of 200 mmφ and a length of 3400 mm, coated with copper of 300 μm thickness, and further plated with nickel to prevent copper oxidation, Blasting was performed while rotating this. For blasting, a blast nozzle of 8 mmφ is installed at a distance of 290 mm from the surface of the mold roll, and the abrasive is sprayed on the front surface of the mold roll at a discharge pressure of 0.5 MPa toward the rotation center of the mold roll. A mold roll having a fine uneven shape was produced. As the abrasive, glass beads having a particle size of 45 μm or less (J400, manufactured by Potters Barotini) were used.
Next, the mold roll and the rubber nip roll were arranged in parallel as in the manufacturing apparatus 40 of FIG. A 188 μm thick PET film (T910E, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) coated on both sides to improve adhesion between the active energy ray curable resin composition between the mold roll and the rubber nip roll. The translucent base material which consists of was supplied along the type | mold roll. And the said translucent base material was nipped between the rubber nip roll (rubber hardness 90 degree | times) and a type | mold roll.
The translucent substrate was moved at a speed of 8 m / min while supplying the active energy ray-curable resin composition to the mold roll side of the translucent substrate nipped by the rubber nip roll. . While rotating the mold roll, ultraviolet rays (metal halide lamp, 120 W / cm) were irradiated from an ultraviolet irradiation device to polymerize and cure the active energy ray-curable resin composition, thereby transferring the irregularities on the shape transfer surface of the mold roll. Then, it released from the type | mold roll and obtained the laminated body in which the light-diffusion layer was formed in one surface of the translucent base material.

(Production Example 2) Production of prism layer The side opposite to the side on which the light diffusion layer is formed between the mold roll on which a plurality of patterns corresponding to the shape of the prism row are formed and the rubber nip roll (rubber hardness 20 degrees). The laminate obtained in “(Production Example 1)” was supplied so that the surface of the sheet was on the mold roll side. The translucent substrate was moved at a speed of 5 m / min while supplying the active energy ray-curable resin composition to the mold roll side of the translucent substrate nipped by the rubber nip roll. . While rotating the mold roll, a prism layer was formed by irradiating ultraviolet rays (high pressure mercury lamp, 240 W / cm × 2 lamps) from an ultraviolet irradiation device, and a prism row and an intermediate layer were integrated to obtain a prism sheet. . As the prism row, prism rows having an apex angle of 68 ° were arranged at pitches of 50 μm and 30 μm.

(Synthesis Example 1) Preparation of Urethane Acrylate Compound (UA1) Into a glass flask, 117.6 g (0.7 mol) of hexamethylene diisocyanate and 151.2 g of isocyanurate type hexamethylene diisocyanate trimer as an isocyanate compound (0 3 mol), as a (meth) acryloyl compound having a hydroxyl group, 128.7 g (0.99 mol) of 2-hydroxypropyl acrylate and 693 g (1.54 mol) of pentaerythritol triacrylate, and dilauric acid as a catalyst 100 mass ppm of di-n-butyltin and 0.55 g of hydroquinone monomethyl ether as a polymerization inhibitor are added and reacted at a temperature of 70 to 80 ° C. until the residual isocyanate concentration becomes 0.1 mass% or less, Urethane acrylate compound A product (UA1) was obtained.

Synthesis Example 2 Synthesis of Urethane Acrylate Compound (UA2) In a glass flask, 151.2 g (0.3 mol) of hexamethylene diisocyanate cyclic trimer as an isocyanate compound, and dipentayl as an acryloyl compound having a hydroxyl group 577 g (1.1 mol) of erythritol pentaacrylate, 100 mass ppm of di-n-butyltin dilaurate as a catalyst, 0.30 g of hydroquinone monomethyl ether as a polymerization inhibitor, and neopentyl glycol dihydroxypivalate as a diluent 82.7 g (2.65) mol of acrylate was charged and reacted at 50 ° C. until the residual isocyanate concentration became 0.1% by mass or less to obtain a urethane acrylate compound (UA2).

Example 1
<Light diffusion layer>
As an active energy ray-curable resin composition for forming a light diffusion layer, a resin composition A was obtained by mixing according to the following formulation. Using the obtained resin composition A, the viscosity at 50 ° C., the tan δ peak, and the tensile modulus were measured, and the results are shown in Table 1.
(B) Component: As a (meth) acrylate compound having two (meth) acryloyl groups having no urethane bond and having a molecular weight of 500 or more and a tan δ peak of the cured product of less than 70 ° C., an acrylate PBOM (the above (I ) Compound in which l = 9 in the formula, manufactured by Mitsubishi Rayon Co., Ltd.) 25 parts by mass (c) Component: As an aliphatic compound having a viscosity at 25 ° C. of 50 mPa · s or less, New Frontier HPN (hydroxypivalic acid) Neopentyl glycol diacrylate (Daiichi Kogyo Seiyaku Co., Ltd.) ... 20 parts by mass (d) Component: Irgacure 184 (1-hydroxycyclophenyl ketone, manufactured by Ciba-Geigy Corporation) ... 1 as a polymerization initiator .6 parts by mass Urethane acrylate compound UA2 prepared in Synthesis Example 2 55 parts by mass Was by using the resin composition A, in accordance with Production Example 1 described above was shaped light diffusing surface of the nip pressure as 0.12 MPa. Here, UA2 includes (a) component: a structure derived from pentaerythritol and / or dipentaerythritol, an aliphatic urethane (meth) acrylate compound having nine or more polymerizable double bond groups, Component (c): Since both of the aliphatic compounds having a viscosity at 25 ° C. of 50 mPa · s or less are included, the mass fraction of (a) :( b) :( c) :( d) is 42.5 : 25: 32.5: 1.6.

<Prism array>
As an active energy ray-curable resin composition for forming a prism array and an intermediate layer, RP4000S (manufactured by Mitsubishi Rayon Co., Ltd.) was used and a prism array with a nip pressure of 0.12 MPa and a pitch of 50 μm was used according to the above Production Example 2. The prism sheet A was obtained by shaping. The obtained prism sheet A was evaluated for scratch resistance and warpage, and the results are shown in Table 1.

(Example 2)
A resin composition B was obtained in the same manner as in Example 1 using the following formulation as the active energy ray-curable resin composition for forming the light diffusion layer. Using the obtained resin composition B, the viscosity at 50 ° C., the tan δ peak, and the tensile rate were measured, and the results are shown in Table 1. Also, using the obtained resin composition B, a prism sheet was obtained in the same manner as in Example 1 except that the nip pressure at the time of forming the light diffusion layer was 0.2 MPa and the nip pressure at the time of prism formation was 0.13 MPa. B was obtained. The obtained prism sheet B was evaluated for scratch resistance and warpage, and the results are shown in Table 1.
(B) Component: Acryester PBOM ... 20 parts by mass (c) Component: New Frontier HPN ... 25 parts by mass (d) Component: Irgacure 184 ... 1.6 parts by mass Urethane acrylate compound UA2 ... 55 parts by mass Since UA2 includes both the component (a) and the component (c), the mass fraction of (a) :( b) :( c) :( d) is 42.5: 20. : 37.5: 1.6.

(Example 3)
A resin composition C was obtained in the same manner as in Example 1 using the following formulation as the active energy ray-curable resin composition for forming the light diffusion layer. Using the obtained resin composition C, the viscosity at 50 ° C., the tan δ peak, and the tensile modulus were measured, and the results are shown in Table 1. Also, using the obtained resin composition C, a prism sheet was obtained in the same manner as in Example 1 except that the nip pressure at the time of forming the light diffusion layer was 0.1 MPa and the nip pressure at the time of prism formation was 0.16 MPa. C was obtained. The obtained prism sheet C was evaluated for scratch resistance and warpage, and the results are shown in Table 1.
(A) Component: Urethane acrylate compound UA1 ... 50 parts by mass (b) Component: Acryester PBOM ... 33 parts by mass (c) Component: PE-200 (polyethylene glycol 200 diacrylate, Daiichi Kogyo Seiyaku Co., Ltd.) Made) ... 17 parts by mass (d) Component: Irgacure 184 ... 1.6 parts by mass

(Example 4)
A prism sheet D was obtained in the same manner as in Example 1 except that the nip pressure at the time of forming the light diffusion layer was 0.5 MPa, the prism pitch was 30 μm, and the nip pressure at the time of prism formation was 0.2 MPa. The obtained prism sheet D was evaluated for scratch resistance and warpage, and the results are shown in Table 1.

(Comparative Examples 1 and 2)
As the active energy ray-curable resin composition for forming the light diffusion layer, the resin composition (RP4000S) used for forming the prism row is used, the nip pressure at the time of forming the light diffusion layer is 0.26 MPa, A prism sheet E-1 was obtained in the same manner as in Example 1 except that the nip pressure was set to 0.13 MPa (Comparative Example 1). A prism sheet E-2 was obtained in the same manner as in Example 1 except that the nip pressure during prism formation was 0.10 MPa (Comparative Example 2). When the warpage of the obtained prism sheet was evaluated, a light diffusion layer of 15 μm or more was required to cancel the warp. Judged to be out of specification. Further, for RP4000S, the viscosity at 50 ° C., the tan δ peak, and the tensile modulus were measured, and the results are shown in Table 1.

(Comparative Example 3)
In a 2 L separable flask of a polymerization reaction vessel, 106 parts by mass of toluene, 71 parts by mass of methyl ethyl ketone (MEK), 69 parts by mass of methyl methacrylate (MMA), 25 parts by mass of ethyl acrylate (EA), 5 parts by mass of hydroxyethyl methacrylate (HEMA) And 1 part by mass of MAA were weighed, and bubbling with nitrogen was performed for 30 minutes while stirring. Then, after adding 0.45 mass part of azobisisobutyronitrile (AIBN) as a radical polymerization initiator, it heated up at 90 degreeC and hold | maintained in that state for 5 hours. Further, 1 part by weight of AIBN was added and held for 4 hours, and then cooled to room temperature to complete the reaction. In this way, a solution of acrylic resin A was obtained.
The acrylic resin A has a molecular weight of 75100, a hydroxyl value of 21.6 mgKOH / g, an acid value of 2.1 mgKOH / g, and a tan δ peak of 61 ° C., and the heating residue of the acrylic resin A solution is 36.0% by mass. Met.
Silicone resin fine particles (refractive index: 1.42, average particle size: 3.0 μm, true specific gravity: 1.32, trade name: Tospearl 130, manufactured by GE Toshiba Silicones Co., Ltd.) as a light diffusing material ) 70 mass%, acrylic resin fine particles as second light diffusing material (refractive index: 1.49, average particle size: 3.0 μm, true specific gravity: 1.20, trade name: XX-57B, Sekisui Plastics Co., Ltd.) A 30% by mass mixture was obtained.
As a solvent, a mixed solution of 40% by mass of MEK and 60% by mass of toluene was prepared.
The cross-linking agent (Duranate TPA-100: manufactured by Asahi Kasei Chemicals Corporation) was weighed so as to be 7.2% by mass with respect to 92.8% by mass of the acrylic resin A solid content.
Then, 258 parts by mass of the acrylic resin A solution, 28 parts by mass of the light diffusing material, 328 parts by mass of the solvent, and 7.2 parts by mass of the crosslinking agent are mixed with stirring to prepare a coating liquid for forming the light diffusing layer. did.
The coating liquid was applied to one side of a PET film (T910E, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) by a reverse gravure coating method to form a light diffusion layer having an uneven surface. A prism was shaped in the same manner as in Example 1 except that the nip pressure was 0.20 MPa on the side opposite to the light diffusion layer of the obtained film.

As in Examples 1 to 4 in Table 1, all of the resin compositions A to C, which are active energy ray-curable resin compositions having the components (a) to (d), have a viscosity at 50 ° C. of 200 mPa · s or less. The cured products of the resin compositions A to C had a tan δ peak of 60 ° C. or higher.
And as Examples 1-4, although resin composition A-C was able to form the light-diffusion layer by the thickness of 10 micrometers or less, resin of the comparative examples 1 and 2 is a light-diffusion layer for canceling curvature. The thickness exceeded 10 μm. From this, it was found that the resin compositions A to C can be easily thinned.
Further, in Examples 1 to 4, it was found that the warpage of the prism sheet is less than 1 mm, and is excellent in preventing warpage even when the thickness is reduced.
The prism sheets of Examples 1 to 4 were not damaged in the scratch resistance test. On the other hand, in Comparative Example 3, damage was observed in the scratch resistance test. From this, it turned out that Examples 1-4 which used resin composition AC for a light-diffusion layer are excellent in abrasion resistance.

10, 105 Prism sheet 12 Light diffusion layer 14 Translucent substrate 20 Prism layer

Claims (3)

Having a prism layer on one side of the translucent substrate;
On the other surface of the translucent base material is a prism sheet having a light diffusion layer with irregularities formed on the surface,
The light diffusion layer is obtained from an active energy ray-curable resin composition having the following components (a) to (d) as main components and having a viscosity at 50 ° C. of 200 mPa · s or less. .
Component (a): an aliphatic urethane (meth) acrylate compound having a structure derived from pentaerythritol and / or dipentaerythritol and nine or more polymerizable double bond groups ( 40 to 55 parts by mass) .
(B) Component: A (meth) acrylate compound (5 to 35 parts by mass) having two (meth) acryloyl groups having no urethane bond and having a molecular weight of 500 or more and a tan δ peak of the cured product of less than 70 ° C.
Component (c): 25 diacrylate viscosity at ℃ is less than 50mPa · s (10 ~50 parts by weight).
(D) Component: A polymerization initiator.
[However, the sum of the component (a), the component (b), and the component (c) is 100 parts by mass. ]   2. The prism sheet according to claim 1, wherein the cured product of the active energy ray-curable resin composition has a peak temperature of tan δ of 60 ° C. or higher.   The prism sheet according to claim 1 or 2, wherein the cured product of the active energy ray curable resin composition has a tensile elastic modulus at 25 ° C of 2.7 GPa or more.

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