JP2008304524A - Anti-abrasion multilayer lens film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-abrasion multilayer lens film which is hardly damaged during assembling work and after assembling and has satisfactory optical performance. <P>SOLUTION: The anti-abrasion multilayer lens film is prepared by integrating a back surface layer 3 made of a specified acrylic resin on one surface of a lens layer 2 which is made of polycarbonate and has a lens surface 2a on the other surface thereof according to melt coextrusion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a scratch-resistant multilayer lens film suitable for liquid crystal display devices such as liquid crystal televisions, computers and word processors. More specifically, the present invention relates to a scratch-resistant compound lens having a lens function that is hard to be scratched and easy to handle. It relates to a layer lens film.

  In recent years, liquid crystal display devices have been used in various fields, and various performances are required depending on the respective applications. For office automation equipment, personal computers, word processors, etc., there are strong demands for weight reduction, thinning, high definition, and power saving. Furthermore, for liquid crystal display devices, a wider field of view, wider screen, and higher brightness are required. The demand is getting stronger.

  In order to meet these requirements, the light from the backlight is diffused according to the application, or conversely, the directivity of the light is changed, that is, the light in an unnecessary direction is redirected and condensed on the front of the observer. Therefore, it is common to use a film or a sheet having a lens function (hereinafter collectively referred to as a lens film).

  In order to prepare such a lens film, generally, a method of forming a lens structure made of a resin curable by light, heat or electron beam on the surface of biaxially stretched polyethylene terephthalate as a base material, A method of forming the pattern by pressing a mold engraved with a three-dimensional pattern after integrating a transparent resin on it, and forming a lens film provided with the pattern without using a substrate The method to use is used. Among these, the method of integrally forming the lens film is preferable in that the thickness of the lens film itself can be easily adjusted and the lens pattern does not come off from the substrate due to the adhesiveness with the substrate.

  When the method of integrally forming the lens film is adopted, the properties required for the resin used as the material of the lens film include high transparency, dimensional stability, moisture resistance, and the like. Thus, it is desired to have impact resistance so as not to be damaged by the impact when the lens film is punched into a desired shape, and scratch resistance so as not to be scratched even if it is rubbed against the surface of the liquid crystal display device during handling. Furthermore, in order to improve the lens function, a material having a high refractive index is preferable.

A material that satisfies all of the above preferred characteristics has not been found, but polycarbonate is well known as a material that satisfies many of these properties, and since it is relatively inexpensive, it has been frequently used as a material for prism films. (For example, refer to Patent Document 1 and Non-Patent Document 1). However, the lens film made of polycarbonate has the disadvantage of being inferior in surface hardness and scratch resistance, and the scratch resistance is inferior in pencil hardness of about B or 2B, and the lens film on the surface of the backlight or liquid crystal panel. When the film is applied, the back surface of the lens film may be scratched.
More specifically, in a backlight of a liquid crystal display device, a light diffusing film is usually installed on a light guide plate, and this light diffusing film is provided with irregularities so as to cause scattering on the surface. The unevenness is formed by roughening the surface of the resin or by arranging organic or inorganic particles on the surface of the resin. Further, a color filter is provided on the surface of the liquid crystal panel, but this color filter also has irregularities due to the setting of the matrix. Any of these irregularities is harder than polycarbonate.
On the other hand, the lens film is usually placed on the light diffusing film or the liquid crystal panel with the lens surface facing the light emitting side, so the back surface of the lens film is in contact with the unevenness of the light diffusing film or the color filter. As a result, scratches occur.

As a method for eliminating this drawback, a method of performing a hard coat treatment by applying a resin that is cured by heat, light, or ionizing radiation on the back surface is known (for example, see Patent Document 2). Furthermore, there are a method of physical vapor deposition in the gas phase and a method of vapor deposition by chemical reaction, both of which have the disadvantage that productivity is low and cost is high.
On the other hand, a transparent resin containing methacrylic resin or methyl methacrylate has high transparency and hardness, and has excellent pencil hardness of 4H with respect to scratch resistance, and is used as a material for a member having a lens function. Since it is inferior in impact resistance, it is difficult to form a film alone and cut it into an appropriate shape for use.
In addition, it is conceivable to attach a coating film having high transparency and scratch resistance to the back surface of a lens film made of polycarbonate with an adhesive or the like.
Japanese Patent No. 3030792 JP 11-326607 A Nikkei Material No. 136 (1993)

In view of such circumstances, the present invention eliminates the problems of the prior art, has scratch resistance that can be applied to a large screen of a liquid crystal television, is not only less likely to cause scratches during assembly work, etc. A scratch-resistant multilayer lens film that does not easily cause scratches and that does not impair optical performance such as light condensing performance, redirection performance by refraction, and light transmission, which are important properties of a lens film. There is.
As a result of diligent research to solve the above-mentioned conventional problems, the present inventors pay attention to the fact that polycarbonate has a good affinity with acrylic resin, and melt coextrusion of this polycarbonate and a specific acrylic resin. It is found that it can be easily bonded without using an adhesive, and as a result, polycarbonate has excellent dimensional stability and moisture resistance, has a high refractive index, and acrylic resin has a high hardness, so that it can be incorporated into liquid crystal display devices. In addition, the present invention was completed by finding that a lens film having excellent optical performance such as light transmission can be formed in addition to being excellent in scratch resistance and being excellent in scratch resistance even in an apparatus after being incorporated. It was.

  The present invention has been made to achieve the above object, and claim 1 of the present invention includes a lens layer having a three-dimensional pattern having a lens function on one surface, and a back surface layer formed on the other surface of the lens layer. The lens layer is made of polycarbonate, and the back layer is made of polymethyl methacrylate, methyl methacrylate of 15% by weight to less than 100% by weight and styrene of more than 0% by weight to 85% by weight. The following copolymer (total is 100% by weight), methyl methacrylate is 60% by weight or more and less than 100% by weight and the copolymerizable monomer is more than 0% by weight and 40% by weight or less (total is 100 (% By weight) copolymer, made of an acrylic resin with a hardness equal to or higher than that of polycarbonate. The resin constituting the lens layer and the resin constituting the back layer are integrated by melt coextrusion. It is the contents of scratch resistance multilayer lens film, characterized by being.

  According to a second aspect of the present invention, a three-dimensional pattern having a lens function is a prism in which a cross section is triangular and a number of triangular prisms having adjacent bases are arranged so that the top ridges are substantially parallel; the cross section is semicircular or semicircular A convex lenticular lens in which a large number of semicircular cylinders or semi-elliptical cylinders that are elliptical and adjacent to each other are arranged so as to be substantially parallel; a semicircular or semi-elliptical shape having a concave surface in cross section and a large number of adjacent side surfaces Concave lenticular lens with concave semi-cylindrical or concave semi-ellipsoidal columns arranged in parallel; Pyramid-type quadrangular pyramid, cubic corner-like trigonal pyramid, and solid shape selected from hemisphere The scratch-resistant multilayer lens film according to claim 1, wherein the scratch-resistant multilayer lens film is selected from the following: a pattern formed or a pattern formed by perforating the three-dimensional shape from a plane.

  According to a third aspect of the present invention, there is provided the scratch-resistant multilayer lens film according to the first or second aspect, wherein either one or both of the lens layer and the back surface layer contains light diffusing particles. Content.

  According to a fourth aspect of the present invention, there is provided the scratch-resistant multilayer lens film according to claim 1 or 2, wherein an uneven structure having a light diffusion function is provided on the outer surface side of the back surface layer. To do.

  Claim 5 of the present invention includes the scratch-resistant multilayer lens film according to claim 4, wherein the uneven structure having a light diffusion function is a random uneven structure or a linear uneven structure. .

  According to a sixth aspect of the present invention, there is provided the scratch-resistant multilayer lens film according to the fifth aspect, wherein the ten-point average roughness Rz in the concavo-convex structure is 0.1 to 2.0 μm. .

According to the scratch-resistant multilayer lens film of the present invention (hereinafter sometimes referred to as “scratch-resistant lens film” or simply “lens film”), a three-dimensional structure having a lens function on one surface of a lens layer made of polycarbonate. Since the pattern is provided, a lens sheet having excellent optical performance utilizing the high refractive index of polycarbonate can be obtained.
Further, a back surface layer made of an acrylic resin having a hardness equal to or higher than that of polycarbonate is provided on the other surface (hereinafter referred to as a lens surface) provided with a three-dimensional pattern having a lens function, that is, the opposite surface. Therefore, even when the lens sheet of the present invention is incorporated in a liquid crystal display device or the like, the lens sheet is protected by the back surface layer and is hardly damaged.
In addition, the acrylic resin used in the present invention has a high affinity with polycarbonate, and can be easily integrated without using an adhesive or the like by melting and co-extruding these resins. There is no light reflection caused by the difference in refractive index between the layers or between the back layer and the adhesive layer, and the entire lens film is excellent in light transmittance.

  As a three-dimensional pattern having a lens function that can be employed in the lens sheet of the present invention, a prism in which a large number of triangular prisms having a triangular cross section and adjacent bases are arranged so that the top ridges are substantially parallel; the cross section is semicircular Or a convex lenticular lens in which a large number of semi-cylindrical or semi-elliptical columns that are semi-elliptical and adjacent to each other are arranged in parallel to each other; semi-circular or semi-elliptical with a concave surface in cross section A concave lenticular lens in which a large number of concave semicircular cylinders or concave semielliptical cylinders are arranged in parallel; a three-dimensional shape selected from a pyramidal quadrangular pyramid, cubic corner-like triangular pyramid, and hemispherical object The pattern which protruded in this, or the pattern which drilled this solid shape from the plane can be illustrated, and, thereby, the lens sheet which has desired optical performance is obtained.

By adding light diffusing particles to one or both of the lens layer and the back surface layer, or providing an uneven structure with a diffusing function on the outer surface side of the back surface layer, the lens function and the diffusing function can be used in combination. A scratch-resistant lens sheet having both of the above can be obtained.
Examples of the concavo-convex structure having a diffusion function include a random concavo-convex structure or a linear concavo-convex structure. If the 10-point average roughness Rz in the concavo-convex structure is 0.1 to 2.0 μm, There is no significant hindrance to optical performance. In addition, even if a slight scratch occurs on the lens surface or the back surface, there is a feature that is difficult to visually recognize.

  As shown in FIG. 1, the scratch-resistant multilayer lens film of the present invention is formed on the lens layer 2 having a three-dimensional pattern having a lens function on one surface and on the other surface of the lens layer. A multi-layer lens film comprising a back layer 3, wherein the lens layer 2 is made of polycarbonate, and the back layer 3 comprises 15% by weight or more and less than 100% by weight of polymethyl methacrylate and methyl methacrylate and 0% by weight of styrene. More than 85% by weight (total 100% by weight) of copolymer, methyl methacrylate is 60% by weight or more and less than 100% by weight and the copolymerizable monomer is more than 0% by weight and more than 40% by weight. % Or less (total is 100% by weight) of a copolymer, made of an acrylic resin having a hardness equal to or higher than that of polycarbonate, and the resin constituting the lens layer 2 and the resin constituting the back layer 3 are melt co-pressed. Characterized in that it is integrated by out.

  Of the scratch-resistant multilayer lens film 1 of the present invention, the lens layer 2 is made of polycarbonate. The polycarbonate used for this invention is a normal polycarbonate which has bisphenol A as a main component, and all the commercially available polycarbonate resins can be used conveniently. This resin usually has a refractive index of 1.58 and a light transmittance of 90% or more, and can be suitably used as a lens sheet material.

  The back layer 3 used in the present invention is made of a specific acrylic resin. This acrylic resin needs to have a high affinity with polycarbonate so that it adheres to the lens layer 2 without using an adhesive, and also protects the lens layer 2 made of polycarbonate from scratches. It must be excellent in terms of scratch resistance. A typical example of an acrylic resin that satisfies such conditions is polymethyl methacrylate. In addition, a copolymer of styrene and methyl methacrylate may be used. The copolymer of methyl methacrylate is 15% by weight or more and less than 100% by weight and styrene is more than 0% by weight and 85% by weight or less (total is 100% by weight). A polymer can be indicated. In still another example of the copolymer, methyl methacrylate is 60% by weight or more and less than 100% by weight, and monomers copolymerizable therewith are more than 0% by weight and 40% by weight or less (total is 100% by weight). The copolymer of these is mentioned.

  The affinity with polycarbonate increases as the amount of methyl methacrylate increases, and polymethyl methacrylate, which is a homopolymer of methyl methacrylate, is most preferable, but if methyl methacrylate is contained in an amount of 15% by weight or more. Sufficient affinity is obtained and can be integrated by melt coextrusion.

  The scratch resistance varies depending on the amount of methyl methacrylate and the type of copolymerizable monomer used, but the higher the amount of methyl methacrylate, the higher the amount of methyl methacrylate. Most preferred is methyl methacrylate. Polycarbonate has a pencil hardness of about B to 2B, whereas polymethyl methacrylate has a pencil hardness of 4H.

  In addition, the copolymer composed of methyl methacrylate and a monomer copolymerizable therewith is copolymerizable because the amount of methyl methacrylate is 60% by weight or more and the hardness is higher than that of polycarbonate. It is necessary to select the type and amount of monomer.

  Examples of the copolymerizable monomer include various methacrylic acid esters or acrylic acid esters, vinyl acetate, acrylonitrile, vinyl chloride, various vinylidene compounds, and the like. These may be used alone or in combination of two or more as required.

As these copolymerizable monomers, styrene is particularly preferable.
Copolymers of methyl methacrylate and styrene are superior to polycarbonate in terms of hardness, regardless of the proportion of styrene and methyl methacrylate, so the amount of methyl methacrylate can be determined considering only adhesiveness. it can. As described above, if the amount of methyl methacrylate is 15% by weight or more, the adhesiveness to the polycarbonate is sufficient. Consequently, methyl methacrylate is 15% by weight or more and less than 100% by weight, and styrene is 0% by weight. % Can be freely selected from the range of 85% by weight or less.

The lens layer 2 is provided with a three-dimensional pattern having a lens function.
The method for forming a three-dimensional pattern having a lens function is not particularly limited. After the resin is formed into a multi-layer film, the film is pressed with an embossing roll or the like to emboss a predetermined film. An example is a method of forming a three-dimensional pattern on a predetermined film simultaneously with extrusion by pressing with a roll having a desired three-dimensional pattern formed on a cooling roll at the time of extrusion.

  The three-dimensional pattern is not particularly limited as long as it has a desired optical performance. However, a prism in which a large number of triangular prisms having a triangular cross section and adjacent bases are arranged so that the top ridges are substantially parallel; A convex lenticular lens having a circular or semi-elliptical shape and a plurality of semi-cylindrical columns or semi-elliptical columns adjacent to each other arranged in parallel to each other; a semicircular or semi-elliptical shape having a concave surface in cross section Concave lenticular lens in which a large number of adjacent concave half-cylinders or concave semi-elliptical cylinders are arranged in parallel; a three-dimensional shape selected from pyramid-type quadrangular pyramids, cubic corner-like pyramids, and hemispheres Or a pattern in which this three-dimensional shape is perforated from a plane.

When a three-dimensional pattern having such a shape is employed, for example, when the cross section is a triangle, it becomes a prism film and has the ability to collect light in the normal direction of the film together with a circular cross section.
More specifically, if a film having a prism having a triangular cross section and a prism in which a number of triangular prisms whose bases are adjacent to each other is arranged so that the top ridges are substantially parallel to each other, the incident surface can be viewed from various directions. When the incident light is incident, it is easy to condense in the apex direction of the triangle, and in the normal direction of the lens film when the triangular shape of the prism is isosceles. This triangular shape usually has an apex angle in the range of 60 degrees to 120 degrees. When the incident light in a specific direction is most, the shape of a triangular prism with equilateral or unequal sides is designed so as to obtain outgoing light in a required direction.

  In addition, when a cubic corner-like pyramid or pyramid type quadrangular pyramid is used, a scratch-resistant lens film having a retroreflective optical performance returned to the light source direction in addition to the ability to collect light can be obtained.

In addition to the above lens function, the scratch-resistant lens film 1 of the present invention can be provided with a light diffusion function. Specifically, either one or both of the lens layer 2 and the back surface layer 3 contain light diffusing particles, or an uneven structure having a light diffusing function is provided on the outer surface side 3a of the back surface layer, or both are used in combination. can do.
By providing these light diffusing functions, it is possible to have both a lens function and a diffusing function, and to improve the quality of screens such as interference fringes generated with other optical members used with the scratch-resistant lens film of the present invention. It has the effect of preventing accidental changes.

As examples of the light diffusing particles, commonly used inorganic particles and organic particles can be used, but it is preferable to select a type having a high total light transmittance and a large haze.
Specifically, examples of the inorganic particles include aluminum silicate, calcium silicate, silica, alumina, calcium carbonate, and the like. Examples of the organic particles include cross-linked polyacrylate and silicon resin.
The diameter of the light diffusing particles is preferably 0.5 μm to 25 μm. Even if the particle diameter is less than 0.5 μm or more than 25 μm, the diffusion function is deteriorated.
Although it does not specifically limit as a compounding quantity of light diffusable particle | grains, Usually, it is 0.5 weight part-20 weight part with respect to 100 weight part of resin of a lens layer or a back surface layer. However, these particles can also be used as fillers to improve hardness if the particle size and refractive index are adjusted, so the acrylic resin constituting the back layer should be blended in a range that does not impair the adhesion to polycarbonate. I can do it.

The scratch-resistant lens film 1 of the present invention can also be provided with a concavo-convex structure having a light diffusing function such as a random concavo-convex structure or a linear concavo-convex structure on the outer surface 3a of the back layer.
Examples of the linear concavo-convex structure include V-shaped, U-shaped, quadrangular, and trapezoidal cross-sections, and examples of the planar view include a linear shape, a wavy shape, and a circular arc shape.
The method for forming the concavo-convex structure having a light diffusion function is not particularly limited, but, as in the case of forming a three-dimensional pattern having a lens function, after the resin is formed into a multilayer film, the film is pressed with an embossed sheet or the like. By embossing a predetermined film, or pressing with a cooling roll at the time of co-extrusion and simultaneously pressing using a roll having a desired uneven pattern, the uneven film is formed on the predetermined film. An example of the method is a concavo-convex structure.

  Providing the concavo-convex structure on the outer side surface 3a of the back surface layer has an effect of not only making it difficult to see the scratches and preventing changes such as interference fringes but also making the scratches less likely to occur during assembly operations. Furthermore, when an appropriate random uneven structure is employed, the coefficient of friction with other surfaces is lowered, so that the occurrence of scratches can be prevented when they are rubbed. However, if the light diffusing function is too large, the optical function of the lens structure 2 is hindered, so an appropriate range needs to be selected.

The degree of unevenness of the uneven structure can be read with the surface roughness defined by JISB0601 by observation with a leather microscope. In this case, the average roughness Ra and the sum of the average value of the heights up to the fifth in the reference length and the average value of the depths up to the fifth in the valley are the 10-point average roughness. Rz is defined as this value, and this value can be represented as surface roughness. In particular, the latter Rz often represents the actual condition of a random uneven surface.
Rz is preferably 0.1 to 2.0 μm. When this value is larger than 2.0 μm, the optical function of the lens is lowered, and when it is smaller than 0.1 μm, the diffusion function is reduced.

  The thickness of the scratch-resistant lens film 1 of the present invention is not particularly limited, but when wound around a core material or the like to form a roll product, the rollable thickness is preferably 500 μm or less. The thickness configuration of the lens layer polycarbonate and the back layer acrylic resin is not particularly limited, but if the back layer acrylic resin is too thick, the end portion may be chipped when punched. Is larger. In order to improve the scratch resistance, considering that the thickness of the acrylic resin of the back layer is about 10 μm, it is preferably about 10 μm to 50 μm.

The lens layer 2 made of the polycarbonate and the back layer 3 made of a specific acrylic resin are integrated by melt coextrusion to form a scratch-resistant lens film.
A method for producing the scratch-resistant lens film 1 by coextrusion will be described with reference to FIG. FIG. 2 is a schematic view showing an example of a resin multilayer method by coextrusion.
First, the polycarbonate and the acrylic resin are respectively melted by using different melt extruders 4A and 4B, and both melted resins are fed to the feed block 5b through the gear pump 5a, and are laminated in a rectifying manner by the feed block 5b. From the die 5c, although not shown in the figure, a film is formed so that the polycarbonate layer is on the cooling roll 6a side between the metal cooling roll 6a and the rubber roll 6b on which a three-dimensional pattern having a lens function is engraved. Extrude into.
The extruded molten resin of polycarbonate and acrylic resin is cooled by the cooling roll 6a, and at the same time, a three-dimensional pattern engraved on the surface of the cooling roll 6a is transferred and formed on the surface of the polycarbonate layer. In addition, in cooling, in order to completely bond the polycarbonate layer (lens layer) and the acrylic resin layer (back surface layer), it is desirable to further sandwich the pressure between the cooling roll 6a and the cooling roll 6a ′ opposed thereto. . The combination of the rolls 6a and 6b: 6a ′ for sandwiching the extruded resin is not limited to the above-described rolls, and examples thereof include a combination of a metal roll and a rubber roll, a metal roll and a metal belt, a metal roll and a metal elastic roll, and the like.
When co-extrusion of polycarbonate and acrylic resin, if necessary, in the case of a combination of a metal roll and a rubber roll, in order to increase the protection and durability of the rubber roll surface, further avoid copying this rough surface, or A support 7 can be interposed to give a specific shape. An example of the support includes a biaxially stretched polyethylene terephthalate film. In the figure, reference numeral 7a denotes a support feeder and 7b denotes a support winder.
The cooled lens film 1 may be wound around a core material using a winder 8 to form a roll product, or may be cut into an appropriate shape and size to be bundled. When a support is used, the support is peeled and removed from the lens film, and then a rolled product is formed or cut.

  Various methods of using the scratch-resistant lens film of the present invention can be considered. When used as a backlight of a liquid crystal display device, the lens structure 2 is generally arranged and used on a light diffusion plate so that the surface of the lens structure 2 becomes a light exit surface. Furthermore, when it is desired to concentrate the light further, the same or similar scratch-resistant lens film may be used in an overlapping manner. The backlight used may be either a direct type or an edge light type. In particular, in a wide-screen liquid crystal television, the scratch-resistant lens film of the present invention is suitable when a direct type diffused light source is used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited only to these Examples.

(Creation of scratch-resistant lens film)
Example 1
Polycarbonate (Panlite L-1250Y manufactured by Teijin Chemicals Ltd.) is sufficiently dehumidified and dried, and then introduced into a screw-type extruder A (caliber 90 mm, L / D32). The extruder has a maximum set temperature of 285 ° C. and a tip set temperature of 260. It set so that it might become ° C.
On the other hand, after sufficiently dehumidifying and drying polymethyl methacrylate (Sumipec HT25x, manufactured by Sumitomo Chemical Co., Ltd.), it is put into a screw-type extruder B (caliber 45, L / D28), and the extruder is set at a maximum set temperature of 260 ° C. and the tip is set. The temperature was set to 260 ° C.
The above resin is fed through a gear pump to a co-extrusion feed block maintained at 260 ° C. at a discharge rate of 85 kg / hr for polycarbonate and 8 kg / hr for polymethyl methacrylate. Then, it was discharged from the tip of the lip set at a die temperature of 265 ° C.
Thereafter, the coextruded resin was pressed through a gap between a metal cooling roll and a rubber roll to obtain a scratch-resistant lens film. On the surface of the cooling roll, an isosceles triangle having an apex angle of 90 degrees is linearly arranged with a period of 50 μm, and the polycarbonate layer of the co-extruded resin is used as the cooling roll side. The methyl layer was the rubber roll side, and a 100 μm biaxially stretched polyethylene terephthalate film was sandwiched between the polymethyl methacrylate layer and the rubber roll.
Then, after further cooling the laminate with a cooling roll, the polyethylene terephthalate film is peeled and removed, and a scratch-resistant lens film comprising a polycarbonate layer (lens layer) and a polymethyl methacrylate layer (back layer) is used as a core material. The product was wound up into a roll product.
The resulting scratch-resistant lens film had a thickness of 240 μm. Considering the amount of resin fed into the coextrusion feed block, the thickness of the polycarbonate layer (lens layer) is estimated to be about 220 μm, and the thickness of the polymethyl methacrylate layer (back layer) is estimated to be about 20 μm. The

Example 2
In place of the polymethyl methacrylate in Example 1, a copolymer of 40% by weight of styrene and 60% by weight of methyl methacrylate (Estyrene MS-600 manufactured by Nippon Steel Chemical Co., Ltd., pencil hardness 3H) was used. A scratch-resistant lens film was prepared in the same manner as in 1.

Example 3
In place of the polymethyl methacrylate of Example 1, a copolymer of 80% by weight of styrene and 20% by weight of methyl methacrylate (Estyrene MS-200 manufactured by Nippon Steel Chemical Co., Ltd., pencil hardness 2H) was used. A scratch-resistant lens film was prepared in the same manner as in 1.

Comparative Example 1
A lens film was produced in the same manner as in Example 1 except that the coextrusion feed block of Example 1 was not used and the extruder A was directly connected to a die to produce a polycarbonate single-layer lens film (thickness 240 μm). It was created.

Comparative Example 2
A commercially available acrylic sheet made of polymethyl methacrylate (Sumitomo Chemical Co., Ltd. Sumipec: registered trademark) was used.

  About the lens film obtained by said Example and comparative example, the abrasion resistance test was done with the following method, and also the punching characteristic and the lens characteristic were measured. The results are shown in Table 1.

(Abrasion resistance test)
1. Pencil hardness of back surface layer It was drawn on the back surface of the lens film with pencils of various hardnesses, and then the presence or absence of scratches on the back surface of the lens film was examined. The result is expressed as the maximum hardness at which no scratch is generated.

2. Vibration test A diffusion film D124Z (manufactured by Tsujiden Co., Ltd.) is placed on a 4 mm thick milky white acrylic flat plate used for the light guide plate so that the concavo-convex surface is on top. After the four sides were fixed so that the (methyl acid layer) was in contact, vibration was applied with a testing machine. Then, the back surface layer of the lens film was observed visually and with a microscope. The results are shown by visual impression and the size of the scratches measured by microscopic observation.
(Vibration conditions)
Testing machine: EMICF 600BA / FAEO8 manufactured by Emic Co., Ltd.
Vibration cycle: Up and down from 20 Hz to 400 Hz in 11 minutes, this is taken as one cycle and vibrates in the vertical, horizontal and height directions for 1 hour each.
Amplitude: 0.075 mm up to 50 Hz, 50 Hz or more is due to amplitude regulation by a constant acceleration of 1.5 G.
Evaluation method: The bottom of the light guide plate is illuminated and visually observed from the oblique direction of the lens film. In addition, since the generation | occurrence | production of a damage | wound receives a vibration to the height and width, a damage | wound is easy to become spherical and the diameter can be observed with a microscope.

(Punching characteristics)
Using a 297 mm × 211 mm A4 size rectangular single-edged Thomson die, a polyethylene terephthalate film having a thickness of 200 μm is laid as a backing plate on a stainless steel plate, and a sample film is placed thereon and punched to check for damage.

(Lens characteristics)
Measured by the ability to scatter light from the back of the prism and collect it in the normal direction. A cold cathode ray tube is provided at the lower part of the light guide plate, a diffusion film D124z is placed on the light guide plate, and a luminance meter (Luminance Colorimeter BM5A manufactured by TOPCON Co., Ltd.) is installed at a position 60 cm away from the lens film. It is indicated by Cd / m ² and indicates the number of times when the lens film is not used, and the luminance when the lens film is not used is 1858 Cd / m ² .
The results of carrying out the above various tests are shown in the table.

  As described above, the scratch-resistant multilayer lens film of the present invention comprises a lens layer made of polycarbonate having a three-dimensional pattern having a lens function on one surface, and an acrylic resin formed on the other surface of the lens layer. Multi-layer lens film composed of a back layer, and the back layer is made of a specific acrylic resin with high hardness and excellent scratch resistance, so that it is difficult to be scratched during or after assembly. In addition, because the lens layer and the back layer are multi-layered by coextrusion without using an adhesive, it is excellent in productivity and due to the difference in refractive index between the lens layer and the adhesive layer and between the back layer and the adhesive layer. Since there is no light reflection that occurs, the entire lens film is highly transparent, and is particularly useful as a lens film used on the surface of a large-screen liquid crystal display device.

It is the schematic which shows the basic composition of an abrasion-resistant multilayer lens film. It is the schematic which shows an example of the multilayer method of resin by co-extrusion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Abrasion-resistant multilayer lens film 2 Lens layer 2a Lens surface 3 Back surface layer 3a Outer side surface 4A, 4B Melt extruder 5a Gear pump 5b Feed block 5c Dice 6a, 6a 'Cooling roll 6b Rubber roll 7 Support body 7a Support body feeding machine 7b Support Winder 8 Lens Film Winder

Claims (6)

A multilayer lens film comprising a lens layer having a three-dimensional pattern having a lens function on one surface and a back surface layer formed on the other surface of the lens layer,
The lens layer is made of polycarbonate,
The back layer is composed of a polymethyl methacrylate, a copolymer of 15 to 100% by weight of methyl methacrylate and a styrene of more than 0% by weight and 85% by weight or less (total of 100% by weight). 60% by weight or more and less than 100% by weight and the copolymerizable monomer is selected from a copolymer of more than 0% by weight and 40% by weight or less (total is 100% by weight), and has a hardness equal to or higher than that of polycarbonate. Made of acrylic resin,
A scratch-resistant multilayer lens film, wherein the resin constituting the lens layer and the resin constituting the back surface layer are integrated by melt coextrusion.   A prism having a three-dimensional pattern having a lens function and a triangular cross section with adjacent bases arranged so that the top ridges are substantially parallel; a semi-circular or semi-elliptical cross section with many adjacent bases Convex lenticular lenses in which the semi-cylindrical or semi-elliptical cylinders are arranged so as to be substantially parallel; a semicircular or semi-elliptical shape having a concave surface in cross section, and a number of concave semi-cylindrical or concave semi-elliptical cylinders adjacent to each other Concave lenticular lenses arranged so as to be substantially parallel; a three-dimensional shape selected from a pyramid-shaped quadrangular pyramid, cubic corner-like trigonal pyramid, hemispherical, or a three-dimensional shape The scratch-resistant multilayer lens film according to claim 1, wherein the scratch-resistant multilayer lens film is selected from a pattern perforated from a plane.   3. The scratch-resistant multilayer lens film according to claim 1, wherein light diffusing particles are contained in either one or both of the lens layer and the back surface layer.   The scratch-resistant multilayer lens film according to claim 1, wherein a concavo-convex structure having a light diffusion function is provided on the outer surface side of the back surface layer.   5. The scratch-resistant multilayer lens film according to claim 4, wherein the uneven structure having a light diffusion function is a random uneven structure or a linear uneven structure.   The scratch-resistant multilayer lens film according to claim 5, wherein a ten-point average roughness Rz in the concavo-convex structure is 0.1 to 2.0 μm.

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