JP2005272700A - Composition curable with active energy ray and optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition capable of forming a high-precision lens array having excellent heat resistance and mechanical properties such as scratch resistance in high productivity. <P>SOLUTION: The composition curable with active energy ray contains (A) a compound curable with active energy ray (excluding the latter components X and Y), (B) an active energy ray sensitive polymerization initiator and (C) at least one kind of compound selected from (X) a fluorine-containing compound curable with active energy ray, (Y) an acid and/or an acid derivative having a ≥8C alkyl group and (Z) a silicone resin. The sum of A and B is 90-99.8 pts. mass and that of the component C is 10-0.2 pts. mass based on 100 pts. mass of the sum of A to C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an active energy ray-curable composition suitable for use in a lens array of an optical sheet such as a prism sheet used for a liquid crystal display backlight or the like, and an optical sheet using the same.

Conventionally, an optical sheet such as a brightness enhancement prism sheet used for a backlight of a liquid crystal display device or the like is manufactured by a press method, a cutting method, an extrusion method, or the like.
However, the press method requires heating, pressurization, and cooling processes for molding, and the cutting method uses a cutting machine to cut out the pattern for each resin plate, which is difficult in terms of productivity. . The extrusion method is suitable for mass production of one kind of optical sheet, but when producing many kinds, the mold must be exchanged for each kind, which is difficult in terms of productivity.

  Under such a background, a technique for forming a lens array such as a prism lens using an active energy ray-curable composition on a sheet-like translucent substrate has been proposed (Patent Document 1). According to this technique, a fine lens array can be formed with high productivity.

  On the other hand, in recent years, with high definition of liquid crystal display devices and the like, high definition has also been promoted for optical sheets such as prism sheets mounted thereon. For example, in a prism sheet for backlight, it is necessary to form a fine lens array with a prism apex angle of 60 to 70 ° and a pitch of several tens of μm, with a sharp tip portion (Patent Document 2, etc.). Further, the backlight prism sheet is disposed between the light guide and the liquid crystal cell so that the prism surface is in contact with the light guide. Therefore, the lens array has higher heat resistance and scratch resistance in order to prevent deformation of the prism tip due to temperature rise due to equipment use and damage to the prism surface (prism tip) when mounted on the backlight. Such mechanical characteristics have been demanded. And the technique of patent document 1 does not fully satisfy this characteristic.

Disclosed is a lens resin composition (Patent Document 3) with improved mold reproducibility, resilience, impact resistance, etc., and a synthetic resin optical material (Patent Document 4) with improved heat resistance, mechanical properties, etc. Yes. These exhibit a certain degree of effectiveness for improving heat resistance and scratch resistance, but none of them are intended for high-definition lens arrays for liquid crystal display device backlights (for example, patents) Reference 4 is directed to cast polymerization using a mold or the like.), Which is insufficient for high-definition applications.
Japanese Patent Publication No. 1-35737 JP-A-8-122536 JP-A-10-114811 Japanese Patent Laid-Open No. 10-130361

  The present invention has been made in view of the above circumstances, and has excellent mechanical properties such as heat resistance and scratch resistance, and can form a high-definition lens array with high productivity, and uses the same. It is an object of the present invention to provide an optical sheet.

  The inventor diligently studied to solve the above problems, and invented the following active energy ray-curable composition and optical sheet.

The active energy ray-curable composition of the present invention comprises an active energy ray-curable compound (A) (excluding components (X) and (Y) described later), an active energy ray-sensitive polymerization initiator (B), and From 90 to 99.8 parts by mass in total, and further from the fluorine-containing active energy ray-curable compound (X), the acid and / or acid derivative (Y) having an alkyl group having 8 or more carbon atoms, and the silicone resin (Z). It is characterized by containing 10 to 0.2 parts by mass of at least one selected compound (C) (provided that the total of components (A) to (C) is 100 parts by mass).
The optical sheet of the present invention includes a lens array formed by molding and curing the active energy ray-curable composition of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the active energy ray-curable resin composition which is excellent in mechanical characteristics, such as heat resistance and abrasion resistance, and can form a high-definition lens array with sufficient productivity can be provided. Further, by using this composition, it is possible to provide a high-quality optical sheet in which the occurrence of optical defects is suppressed when mounted on a backlight or the like or when an apparatus is used.

Hereinafter, the present invention will be described in detail.
"Active energy ray-curable composition"
The active energy ray-curable composition of the present invention comprises an active energy ray-curable compound (A) (excluding components (X) and (Y) described later) and an active energy ray-sensitive polymerization initiator (B), Further, at least one compound (C) selected from a fluorine-containing active energy ray-curable compound (X), an acid and / or acid derivative (Y) having an alkyl group having 8 or more carbon atoms, and a silicone resin (Z). It contains.

In the composition of the present invention, active energy ray curability is imparted to the composition by components (A) and (B), and mechanical properties such as heat resistance and scratch resistance are imparted to a cured product such as a lens array. The Moreover, the improvement of the abrasion resistance etc. of hardened | cured material is aimed at by adding a component (C). Component (C) also exhibits an effect of improving the releasability of the cured product, that is, an effect of improving the releasability from the lens mold when forming the lens array.
In this specification, “scratch” means a phenomenon in which when a lens array surface such as a prism lens is rubbed, an optical defect such as whitening occurs due to local destruction or deformation of the lens tip. To do.

"Ingredient (A)"
The active energy ray-curable compound (A) is not particularly limited as long as it is a compound having active energy ray curability, and a cationic polymerizable compound or a radical polymerizable compound can be used. Examples of the cationic polymerizable compound include monomers having an epoxy group or an oxetane group. In terms of curability, a radical polymerizable compound is particularly preferably used.

  Examples of the radical polymerizable compound include radical polymerizable vinyl group-containing monomers. The amount of the vinyl group is not particularly limited, but is preferably 0.3 to 0.5 mol in a total of 100 g of the components (A) and (B) from the viewpoint of mechanical properties such as heat resistance and scratch resistance of the cured product. .

  Among the radically polymerizable vinyl group-containing monomers, the active energy ray-curable compound (A) includes two or more isocyanate groups in the molecule from the viewpoint of mechanical properties such as heat resistance and scratch resistance of the cured product. Containing urethane (meth) acrylate (urethane di (meth) acrylate and / or urethane poly (meth) acrylate) obtained by reacting an isocyanate compound (a1) having a hydroxyl group with (meth) acrylate (a2) Is preferred. The amount of the urethane bond is not particularly limited, but is preferably 0.1 mol or more in 100 g in total of components (A) and (B) from the viewpoint of mechanical properties such as heat resistance and scratch resistance of the cured product.

  There is no restriction | limiting in particular as an isocyanate compound (a1), Diisocyanate compounds, such as alicyclic aliphatic diisocyanate and aromatic diisocyanate, etc. are mentioned, 1 type (s) or 2 or more types can be used. Of these, alicyclic aliphatic diisocyanates such as isophorone diisocyanate and hydrogenated 4,4′-diphenylmethane diisocyanate are preferably used in consideration of yellowing resistance of the cured product.

  Although there is no restriction | limiting in particular as a hydroxyl-containing (meth) acrylate (a2), 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, glycerol dimethacrylate, pentaerythritol triacrylate etc. are mentioned, 1 type Or 2 or more types can be used. Among them, from the viewpoint of mechanical properties such as heat resistance and scratch resistance of the cured product, a compound having a hydroxyl group and two or more (meth) acryloyl groups in the molecule, in particular, excellent curability of the component (A). A compound represented by the following formula (1), particularly pentaerythritol triacrylate, is preferably used.

（式中、Ｒ_１は水素原子又はメチル基を示す。）

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

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

In the composition of the present invention, the compounding amount of the component (A) is 85 to 99.7 parts by mass, particularly 90 to 99.4 parts by mass with respect to a total of 100 parts by mass of the components (A) to (C). preferable. In the composition of the present invention, the total amount of components (A) and (B) is 90 to 99.8 parts by weight, preferably 95, with respect to 100 parts by weight of the total of components (A) to (C). ˜99.5 parts by mass.
If the blending amount of component (A) or the total amount of components (A) and (B) is less than the above lower limit, mechanical properties such as curability and heat resistance and scratch resistance of the cured product become insufficient, and the above upper limit is exceeded. When it exceeds, the compounding quantity of a component (C) will decrease too much, and the effect of adding this, ie, the improvement effect, such as abrasion resistance, and the mold release improvement effect of hardened | cured material will not express significantly.

"Ingredient (B)"
The active energy ray sensitive polymerization initiator (B) is selected according to the type of the component (A). That is, when component (A) is a cationic polymerizable compound, a cationic polymerization initiator is used, and when component (A) is a radical polymerizable compound, a radical polymerization initiator is used.
The radical polymerization initiator is not particularly limited as long as it generates radicals in response to active energy rays such as ultraviolet rays and visible rays. Specific examples thereof include benzoin, benzoin monomethyl ether, benzoin isopropyl ether, benzophenone, diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenyl. Carbonyl compounds such as propan-1-one, sulfur compounds such as tetramethylthiuram disulfide, acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, visible light sensitive radical polymerization such as camphorquinone An initiator etc. are mentioned. These can use 1 type (s) or 2 or more types.

  The blending amount of the polymerization initiator (B) may be appropriately set so that the total amount with the component (A) is within the above blending amount range, but with respect to 100 parts by mass in total of the components (A) to (C). 0.01 to 5 parts by mass, particularly 0.1 to 3 parts by mass is preferable. When the blending amount of the component (B) is less than the lower limit, the curability of the composition is insufficient, and when it exceeds the upper limit, the cured product is easily colored yellow.

"Ingredient (C)"
In the present invention, the fluorine-containing active energy ray-curable compound (X), which has an effect of improving the mechanical properties such as scratch resistance of the cured product and the effect of improving the releasability of the cured product, has 8 carbon atoms. At least one compound selected from acids and / or acid derivatives (Y) having an alkyl group and silicone resin (Z) is used.

(Compound (X))
The fluorine-containing active energy ray-curable compound (X) is not particularly limited as long as it has reactivity with the component (A), but the reactivity with the component (A), the scratch resistance of the cured product, etc. Fluorine-containing (meth) acrylates are preferably used from the viewpoints of improvement and improved mold release of the cured product. Specific examples thereof include trifluoroethyl acrylate, trifluoroethyl methacrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, heptadecafluorodecyl methacrylate and the like, and one or more are used. Can do. Among them, trifluoroethyl acrylate is preferably used because of its high reactivity with the component (A) and high curability.

(Compound (Y))
The acid and / or acid derivative (Y) having an alkyl group having 8 or more carbon atoms is not particularly limited, but is a dimer from the viewpoint of improving the scratch resistance of the cured product and improving the release property of the cured product. An acid and / or a derivative thereof, particularly dimer diol and / or di (meth) acrylate of dimer diol is preferably used.
Examples of the dimer diol having an alkyl group having 8 or more carbon atoms include Pripol 2033 (trade name) manufactured by Unikema Co., Ltd., and di (meth) acrylate having an alkyl group having 8 or more carbon atoms is esterified as an example. And the like. Compound (Y) can use 1 type (s) or 2 or more types.

(Compound (Z))
The silicone resin (Z) is not particularly limited, but polyether-modified polydimethylsiloxane and the like are preferably used from the viewpoint of improving the scratch resistance of the cured product and improving the release property of the cured product. Further, as the silicone resin (Z), two or more types having different molecular weights or structures can be used in combination.

  As the component (C), among the above compounds, the compound (Y), particularly dimer diol, is preferably used because the effect of improving the scratch resistance of the cured product is large.

  The compounding amount of component (C), which is at least one compound selected from compounds (X) to (Z), is 10 to 0.00 with respect to a total of 100 parts by mass of components (A) to (C). 2 parts by mass, preferably 5 to 0.5 parts by mass. If the blending amount of the component (C) is less than the above lower limit, the effect of adding this does not appear remarkably, and if it exceeds the above upper limit, the heat resistance of the cured product is lowered, and further, the component (C ) Is excessively present, an optical defect may occur.

(Other ingredients)
The composition of the present invention includes an antioxidant, an anti-yellowing agent, an ultraviolet absorber, a bluing agent, a pigment, an anti-settling agent, an antifoaming agent, an antiwear agent, and a friction reducing agent as necessary. Various additives such as an antistatic agent and an antifogging agent may be contained.

Although the viscosity of the composition of this invention is not specifically limited, It is preferable that the viscosity in 50 degreeC is 50-500 mPa * s, especially 100-400 mPa * s.
When the viscosity at 50 ° C. is less than the above lower limit, the fluidity of the composition becomes high, and the composition tends to flow out of the lens mold when the lens array is formed, and it tends to be difficult to obtain a lens array having a uniform thickness. If the viscosity at 50 ° C. exceeds the above upper limit, the fluidity of the composition decreases, and it tends to be difficult to fill the lens mold with the composition when forming a lens array, and bubbles are involved. This tends to make it difficult to form a high-definition lens array free from optical defects. Furthermore, the workability of injecting the composition into the lens mold also tends to decrease.

The Vickers hardness at 20 ° C. of the cured product of the composition of the present invention is 12 to 25, preferably 14 to 23.
When the Vickers hardness is 12 or more, the cured product has good mechanical properties such as scratch resistance and mechanical strength as a lens array such as a prism sheet for a high brightness backlight. On the other hand, if the Vickers hardness exceeds 25, the hardness of the cured product becomes too high, and there is a risk of damage to other members (backlight guide or the like) that come into contact with the Vickers hardness.

  According to the active energy ray-curable composition of the present invention having the above configuration, a high-definition lens array having excellent mechanical properties such as heat resistance and scratch resistance can be obtained. In addition, the composition of the present invention is excellent in curability and mold releasability, and a high-definition lens array having a desired pattern can be easily obtained by simply injecting the composition into a lens mold and curing and releasing the composition. Can be formed with good productivity.

"Structure of optical sheet"
The optical sheet of the present invention is characterized by comprising a lens array formed by molding and curing the above active energy ray-curable composition of the present invention.
The present invention can be preferably applied to an optical sheet having a lens array on the surface of a translucent substrate such as a film, a sheet, or a plate. In particular, the present invention can be preferably applied to a prism sheet used for a liquid crystal display device backlight or the like.

  Hereinafter, the structure of an optical sheet according to an embodiment of the present invention will be described with reference to the drawings, using a backlight prism sheet as an example. An example of a backlight including the prism sheet will also be described. FIG. 1 is a perspective view showing a state mounted on a backlight, and FIG. 2 is a sectional view in the thickness direction of the prism sheet. In FIG. 1, the base material of the prism sheet is not shown.

  As shown in the figure, the prism sheet 3 of the present embodiment is generally composed of a translucent substrate 1 such as a film, a sheet, or a plate, and a lens array 2 formed thereon.

The material of the substrate 1 is not particularly limited as long as it transmits an active energy ray, but transparent synthetic resins such as glass, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylimide resin, and polyester resin are used. . From the viewpoint of light transmittance as a backlight, a transparent synthetic resin is usually used. The substrate 1 may be subjected to treatments such as antistatic and antireflection.
The lens array 2 may be provided directly on the substrate 1, but may be provided via the adhesion improving layer 4. The adhesion improving layer 4 can be formed by separately providing an easy adhesion layer made of an acrylic resin, a urethane resin, or the like, or by roughening the surface layer portion of the substrate 1.

The lens array 2 is obtained by molding and curing the active energy ray-curable composition of the present invention described above, and has a large number of triangular prisms 2a arranged in one direction at a predetermined pitch (prism array).
In the backlight prism sheet 3, it is preferable that the thickness of the lens array 2 is about 0.1 to 3 mm, the prism apex angle is about 50 to 75 °, and the prism pitch is about 10 to 500 μm.

  The prism sheet 3 may be provided with a diffusion function for the purpose of widening the outgoing light distribution or obtaining a smoother outgoing light distribution. As a diffusion function imparting method, the surface of the substrate 1 or the lens array 2 is roughened by mixing a diffusion material such as resin fine particles or inorganic fine particles into the substrate 1 or the lens array 2. For example, a lens array intersecting with the prism 2a array may be formed on the surface opposite to the array 2.

  The backlight 20 shown in FIG. 1 includes a linear light source 12 such as a fluorescent lamp, a light guide 13 that guides light emitted from the light source 12 to the liquid crystal cell side (the upper side in the drawing), and a liquid crystal of the light guide 13. The prism sheet 3 is mounted on the cell side. On the opposite side of the light guide 13 from the liquid crystal cell, a reflective layer 14 made of a reflective film, a reflective vapor deposition layer or the like is formed. In order to effectively introduce light from the light source 12 to the light guide 13, the side of the light source 12 not facing the light guide 13 is covered with a reflector 15 such as a case or film coated with a reflective agent on the inside. Yes.

  The light guide 13 is made of a synthetic resin having a high light transmittance such as an acrylic resin, a polycarbonate resin, or a vinyl chloride resin. One side surface of the light guide body 13 is opposed to the light source 12 to form a light incident surface. The light incident on the light guide 13 is repeatedly reflected, propagates in the light guide 13 and is emitted from the surface on the liquid crystal cell side. The light emitting surface of the light guide 13 is subjected to a roughening process such as sandblasting, and formation of concave and convex patterns such as a prism array and a lenticular lens array, so that directional light is emitted. It has become.

  The prism sheet 3 is arranged so that the lens array 2 side is the light guide 13 side. Moreover, it is preferable to arrange each prism 2a and the light source 12 substantially in parallel. The traveling direction of the light emitted from the light guide 13 is changed to the observer side by the total reflection action of the prism 2a. As a result, the amount of light emitted to the observer side increases, and high-luminance display is possible.

In addition, this invention is applicable not only to the said form but to any backlight, if it is a backlight provided with the prism sheet.
For example, the present invention can also be applied to a backlight in which a prism sheet is arranged so that the lens array 2 is on the liquid crystal cell side via a diffusion sheet on the light exit surface side of the light guide. In this case, the prism apex angle is preferably 80 to 130 °. In addition, the present invention can also be applied to a backlight in which a plurality of prism sheets are stacked on the light exit surface of the light guide.

"Production method of optical sheet"
The optical sheet manufacturing method of the present invention will be described using the prism sheet 3 as an example. The optical sheet of the present invention can be produced by either a batch production method or a continuous production method.

  Based on FIG. 3, the batch production method will be described. In FIG. 3, (a) is a perspective view of a lens mold, and (b) and (c) are schematic sectional views showing a casting process and a releasing process, respectively.

  First, a lens mold 6 shown in FIG. 3A on which a desired prism pattern is formed is prepared. Although it does not specifically limit as the lens type | mold 6, Metal type | molds, such as aluminum, brass, steel, synthetic resin type | molds, such as a silicone resin, a urethane resin, an epoxy resin, an ABS resin, a fluororesin, and a polymethylpentene resin, these And a mixture of various metal powders. In particular, a metal mold is preferably used in terms of heat resistance and strength.

As shown in FIG. 2B, the active energy ray-curable composition 5 of the present invention is injected and extended into the prepared lens mold 6 and covered with a translucent substrate 1. An adhesion improving layer 4 is formed on the substrate 1 in advance as necessary.
Next, active energy rays are irradiated from the substrate 1 side to cure the composition 5. Thus, the prism sheet 3 in which the base material 1 and the lens array 2 are in close contact with each other is obtained at the same time as the composition 5 is molded and the lens array 2 is formed.
As the active energy ray light source, a chemical reaction chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a visible light halogen lamp, sunlight, or the like can be used. Although irradiation energy is not specifically limited, It is preferable to irradiate so that the integrated energy of the wavelength of 200-600 nm may be 0.1-5 J / cm < ² >. The irradiation atmosphere of active energy rays may be air or an inert gas such as nitrogen or argon.
Finally, the prism sheet 3 is released from the lens mold 6 as shown in FIG.

Next, the continuous production method will be briefly described with reference to FIG. The figure is a diagram showing an example of a continuous production method manufacturing apparatus.
In this system, a cylindrical lens mold 7 having a desired prism pattern on the surface is used as a lens mold. Specific examples thereof include those in which a prism pattern is directly formed on the surface of a cylindrical object and those in which a thin plate on which a prism pattern is formed is wound around a core roll and fixed. Further, the same material as that of the lens mold 6 is used.

  The illustrated apparatus includes a tank 9 that stores the active energy ray-curable composition 5 of the present invention, and a supply nozzle 10 that supplies the composition 5 onto the substrate 1. The tank 9 is provided with heat source equipment such as a sheathed heater and a hot water jacket inside or outside the tank so that the temperature of the composition 5 to be stored can be controlled. Further, a nip roll 8 made of various rubber rolls or the like is provided in the vicinity of the nozzle 10 so as to face the cylindrical lens mold 7, and the active energy is opposed to the cylindrical lens mold 7 on the downstream side thereof. A line-emitting light source 11 is provided. As the active energy ray emission light source 11, the same one as in the batch production method is used.

The translucent base material 1 is continuously supplied so as to travel along the cylindrical lens mold 7, and the composition 5 in the tank 9 passes through the pipe from the supply nozzle 10 and the base material 1 and the cylindrical lens mold. 7 is injected. At this time, the thickness of the composition 5 to be injected is made uniform by the gap between the cylindrical lens mold 7 and the nip roll 8.
The composition 5 is held between the base material 1 and the cylindrical lens mold 7 and is irradiated with active energy rays while entering the prism pattern of the cylindrical lens mold 7. The active energy ray is emitted from the active energy ray emission light source 11, and is irradiated to the composition 5 through the substrate 1. As a result, the composition 5 is cured and the lens array 2 is formed, and at the same time, the prism sheet 3 in which the substrate 1 and the lens array 2 are in close contact is obtained. The active energy ray irradiation conditions are the same as in the batch production method.

  Since the optical sheet of the present invention is provided with a lens array obtained by using the active energy ray-curable resin composition of the present invention, optical defects at the time of mounting on a backlight or the like or when using equipment are used. High quality with suppressed generation. In addition, since the lens array can be formed with high productivity, it is excellent in productivity and suitable for the production of various types.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by the following example.
"Synthesis of urethane (meth) acrylate"
(Synthesis example 1) Urethane polyacrylate (A-1)
In a 5 L glass container, 1110 g of isophorone diisocyanate (manufactured by Daicel Huls, IPDI) as an isocyanate compound (a1), 2 g of di-n-butyltin dilaurate as a catalyst, and 2,6-di-tert-butyl as a polymerization inhibitor -4-methylphenol 1.5g was thrown in and it heated at 70 degreeC, stirring. While maintaining the liquid temperature and stirring, 3129 g of pentaerythritol triacrylate (NK ester A-TMM-3L manufactured by Shin-Nakamura Chemical Co., Ltd.) was added dropwise as the hydroxyl group-containing (meth) acrylate (a2) over 5 hours. Furthermore, the liquid temperature was kept at 70 ° C. for 8 hours to synthesize urethane polyacrylate (A-1) (IPDI / PETA).
The progress of the reaction was confirmed by titration analysis of the amount of isocyanate groups, and the time when 96% or more of the isocyanate groups disappeared was regarded as the end point of the reaction.

(Synthesis example 2) Urethane polymethacrylate (A-2)
Urethane polymethacrylate (A-2) (IPDI / GDMA), except that the hydroxyl group-containing (meth) acrylate (a2) was changed to 2394 g of glycerin dimethacrylate (Kyoeisha Chemical Co., Ltd., light ester G-101P) Got.

(Synthesis example 3) Urethane diacrylate (A-3)
Isocyanate compound (a1), hydrogenated 4,4′-diphenylmethane diisocyanate (Desmodur W manufactured by Sumika Bayer Urethane), 1310 g, hydroxyl group-containing (meth) acrylate (a2), 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry) 4-HBA) A urethane diacrylate (A-3) (HMDI / HBA) was obtained in the same manner as in Synthesis Example 1 except that it was changed to 1512 g.

(Synthesis example 4) Urethane diacrylate (A-4)
Urethane diacrylate (A-4) (IPDI / HEA), except that the hydroxyl group-containing (meth) acrylate (a2) was changed to 1218 g of 2-hydroxyethyl acrylate (HEA manufactured by Osaka Organic Chemical Industry). Got.

"Preparation of the mixture"
Prior to the preparation of the present invention and a comparative active energy ray-curable composition, components (A) and (B) were mixed well at 40 ° C. with the compositions shown in Table 1 to obtain a uniform solution (M-1 ) To (M-3) were obtained.
In the table, the unit of the blending amount represents part by mass. Moreover, (A-1)-(A-4) is the urethane (meth) acrylate obtained by the said synthesis example, and another component shows the following commercial item. In the same table, the amount of vinyl groups in the mixture and the amount of urethane bonds are described together.
(A-5): Nonabutylene glycol dimethacrylate (A-6): Ethylene oxide modified bisphenol A diacrylate (number of modifications with ethylene oxide 10)
(B-1): 2-hydroxy-2-methyl-1-phenylpropan-1-one

(Examples and comparative examples)
At 40 ° C., the mixture (M) and components (C) ((X) to (Z)) obtained above were mixed well with the compositions shown in Tables 2 and 3 to obtain a uniform solution, and an active energy ray-curable composition. Got. In the table, the unit of the blending amount represents part by mass, and each abbreviation of component (C) represents the following compound.
(X-1): Trifluoroethyl acrylate (Biscoat 3F manufactured by Osaka Organic Chemical Industry)
(Y-1): Dimer diol (Unipolma Prepol 2033)
(Z-1): Polyether-modified polydimethylsiloxane (BYK-302 manufactured by Big Chemie Japan)
(Z-2): Polyether-modified polydimethylsiloxane (BYK-331 manufactured by BYK Japan)

Using the obtained composition, a prism sheet was produced using the apparatus shown in FIG.
As the translucent base material (1), a PET film (“A4100” manufactured by Toyobo Co., Ltd.) provided with an adhesion improving layer (4) (one obtained by applying a resin for improving adhesiveness on the surface of the base material) on one side. A thickness of 125 μm) was used.
As the cylindrical lens mold (7), an electroless nickel plating is applied to a brass thin plate in which a large number of prismatic prisms having a prism apex angle (α (see FIG. 3A)) of 65 ° are connected in series at a pitch of 50 μm. The one subjected to the above was wound around a stainless steel cylindrical core roll having an outer diameter of 220 mm and a length of 450 mm, and was rotated at a speed of about 3 m / min.
The composition (5) in the tank (9) was kept at 40 ° C.
As the active energy ray light source 11, an ultraviolet irradiation device having a lamp emission length of about 50 cm and 6 kW (120 W / cm) was used, and ultraviolet rays were irradiated so that the irradiation amount (integrated light amount) became 1 J / cm ² .

(Evaluation items and evaluation methods)
The following evaluation was performed about the obtained composition and prism sheet.
<Vickers hardness>
The obtained active energy ray-curable composition was injected into a cell in which a pair of Pyrex (registered trademark) glass (thickness: 3 mm) was arranged to face each other at intervals of 1 mm. On the other hand, a high-pressure mercury lamp is irradiated from one side so that the integrated energy at a wavelength of 200 to 600 nm is 0.7 J / cm ^2, and the same irradiation is performed from the other side to obtain a 1 mm thick cured product. Got. The cured product was taken out of the cell, and the Vickers hardness at 20 ° C. was measured at a load of 98.07 mN using a microhardness meter (MXT70-UL type manufactured by Matsuzawa Seiki Co., Ltd.).

<Viscosity>
The viscosity at 50 ° C. of the obtained active energy ray-curable composition was measured using an E-type viscometer (EHD type manufactured by Toki Sangyo Co., Ltd.).
<Injection workability>
The workability of the composition into the lens mold was evaluated according to the following criteria.
○: There is no entrainment of bubbles and the composition can be injected well into the lens mold without any gaps.
X: Bubbles are involved, and the composition cannot be injected well.

<Heat resistance>
The obtained prism sheet was placed on an acrylic plate (3 mm thick) so that the lens array surface was on the lower side. A glass plate having the same dimensions as the prism sheet was further placed thereon, and a load of 0.8 g / cm ² was applied. In this state, it was put in a drier and heated at 60 ° C. for 6 hours.
○: The lens array surface is the same as before the test.
X: An optical defect such as deformation occurred on the lens array surface by heating.

<Abrasion resistance 1>
With respect to the lens array surface of the obtained prism sheet, the appearance change of the lens array surface when scratched with a nail in a direction perpendicular to the prism ridgeline direction was visually observed and evaluated according to the following criteria.
○: The tip of the lens array is deformed but not destroyed.
X: The tip of the lens array was destroyed and the scratched locus was whitened.

<Abrasion resistance 2>
The obtained prism sheet was placed on a smooth metal table so that the lens array surface was on the upper side. A test piece cut out from an acrylic plate (3 mm thick) was placed thereon, and reciprocated 50 times in a direction perpendicular to the ridge line direction of the prism under a load of about 60 g / cm ² . The appearance change of the lens array surface was visually observed and evaluated according to the following criteria.
○: The lens array surface is the same as before the test.
X: Optical defects such as whitening occurred on the lens array surface.

(result)
The results are shown in Tables 2 and 3.
As shown in the table, the active energy ray-curable compositions obtained in Examples 1 to 6 have a Vickers hardness of 14 to 15 at 20 ° C, a viscosity of 140 to 270 mPa · s at 50 ° C, and a lens. The workability of injection into a mold was excellent, and the obtained prism sheet lens array had good heat resistance and scratch resistance.
Using the obtained prism sheet, the backlight shown in FIG. 1 is configured. The lens array surface is damaged when mounted on the backlight, the prism tip is thermally deformed when the backlight is used, and whitening occurs due to vibration. Thus, a high-quality and high-brightness backlight was obtained.

  On the other hand, in Comparative Examples 1 and 3 in which the component (C) was not blended, the scratch resistance of the obtained lens array was poor. In addition, in Comparative Examples 2, 4, and 5 in which a composition having a Vickers hardness of less than 12 was prepared even when the component (C) was blended, the obtained lens array had poor heat resistance and scratch resistance. there were.

  The technology of the present invention can be preferably applied to optical sheets such as prism sheets for liquid crystal display device backlights and the like.

It is a perspective view which shows the structure of the backlight provided with the optical sheet of one Embodiment which concerns on this invention. It is sectional drawing which shows the structure of the optical sheet of one Embodiment which concerns on this invention. It is process drawing which shows an example of the manufacturing method of the optical sheet of this invention. It is a figure which shows the other example of the manufacturing method of the optical sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent base material 2 Lens array 3 Prism sheet

Claims (3)

90 to 99.8 parts by mass in total of the active energy ray-curable compound (A) (excluding components (X) and (Y) described later) and the active energy ray-sensitive polymerization initiator (B);
Further, at least one compound (C) selected from a fluorine-containing active energy ray-curable compound (X), an acid and / or acid derivative (Y) having an alkyl group having 8 or more carbon atoms, and a silicone resin (Z). An active energy ray-curable composition comprising 10 to 0.2 parts by mass (provided that the total of components (A) to (C) is 100 parts by mass).   An optical sheet comprising a lens array formed by molding and curing the active energy ray-curable composition according to claim 1.   The optical sheet according to claim 2, wherein the lens array has a Vickers hardness of 12 to 25 at 20 ° C.

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