Method for manufacturing view angle control film

Abstract

To provide a method for manufacturing a view angle control film which can manufacture a louver layer having a narrow pitch.SOLUTION: A method for manufacturing a view angle control film includes the steps of: surface modifying both of main surfaces of a transparent resin sheet, coating a colored silicone coating material containing a light-shielding material onto each of the main surfaces, drying and curing the colored silicone coating material, and thereby obtaining a plurality of laminated sheets where light-shielding layers are formed on one main surface and the other main surface of the transparent resin sheet; and surface modifying the light-shielding layers constituting both of the main surfaces of the plurality of laminated sheets, then overlapping, bonding and laminating the laminated sheets while contacting the mutual light-shielding layers, and thereby obtaining a laminated block where the laminated sheets are bonded to each other; and cutting out a louver layer from the laminated block.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a viewing angle control film.

Background Art

[0002] Conventionally, a sheet-like viewing angle control body or anti-peeping body installed in an information display body such as a display has been known (for example, Patent Documents 1 and 2). By installing a viewing angle control body on the display screen, it is possible to prevent leakage of information due to peeping from the side. In addition, a legitimate viewer located in front of the display can read the information displayed on the display through the viewing angle control body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The louver layer, which is the main body of the viewing angle control body, is a sheet with a striped pattern in which strip-shaped light transmission bands and light shielding bands are alternately and repeatedly arranged along the plane direction. The repetition pitch of these light transmission bands or light shielding bands is a major factor in determining the visible angle of the viewing angle control body. In recent years, since displays have high resolution, moiré may occur due to interference with the above pitch of the viewing angle control body. In order to prevent such interference, it has been required to narrow the above pitch of the louver layer.

[0005] However, in the conventional method for manufacturing a viewing angle control member, it has been difficult to narrow the pitch. In the conventional manufacturing method, a transparent silicone sheet and a black silicone sheet containing carbon black as a light shielding material are alternately laminated, and the obtained laminated block is sliced in the thickness direction to cut out a louver layer. Here, the thickness of each of the transparent sheet and the black sheet corresponds to the width of the light transmission band and the light shielding band in the louver layer. In order to narrow the pitch, it is necessary to reduce the thickness of each of the transparent sheet and the black sheet. However, since an extrusion method or a calendar roll method is applied to alternately laminate the transparent sheet and the black sheet, a certain thickness is required for each sheet, and there is a limit to reducing the thickness.

[0006] The present invention provides a method for manufacturing a viewing angle control film capable of manufacturing a louver layer with a narrow pitch.

Means for Solving the Problems

[0007] [1] A step of subjecting both main surfaces of a transparent resin sheet to a surface modification treatment, applying a colored silicone paint containing a light shielding material to each main surface, and drying and curing to obtain a plurality of laminated sheets in which light shielding layers are formed on one main surface and the other main surface of the transparent resin sheet; After subjecting the light shielding layers forming both main surfaces of the plurality of laminated sheets to a surface modification treatment, while bringing the light shielding layers into contact with each other, the laminated sheets are overlapped and pressure-bonded and laminated to obtain a laminated block in which the laminated sheets are adhered to each other; A method for manufacturing a viewing angle control film, comprising a step of cutting out a louver layer from the laminated block. [2] The method for manufacturing a viewing angle control film according to [1], further comprising a step of forming a transparent protective layer on at least one of both main surfaces of the louver layer. [3] The method for manufacturing a viewing angle control film according to [1] or [2], wherein the method for subjecting both main surfaces of the transparent resin sheet to a surface modification treatment is excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation. [4] The method for surface modification treatment of the light shielding layer is excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation, and the method for manufacturing a viewing angle control film according to any one of [1] to [3]. [5] The method for applying the colored silicone paint is a coater method or a printing method, and the method for manufacturing a viewing angle control film according to any one of [1] to [4]. [6] The thickness of the transparent resin sheet is 30 to 90 μm, and the thickness of the light shielding layer is 0.5 to 5.0 μm, and the method for manufacturing a viewing angle control film according to any one of [1] to [5].

Effect of the Invention

[0008] According to the present invention, a viewing angle control film provided with a narrow pitch louver layer can be easily manufactured.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, a method for manufacturing a viewing angle control film will be described. The dimensions and the like of the drawings exemplified in the following description are merely examples, and the present invention is not necessarily limited thereto, and can be appropriately changed and implemented without changing the gist thereof.

[0011] Fig. 1(a) shows a state of surface modification treatment of one main surface of the transparent resin sheet 10. The symbol P represents plasma treatment, which is an example of surface modification treatment. The transparent resin sheet 10 may be made of any resin that is transparent and allows light to pass through. For example, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and general-purpose resins such as polystyrene and polyolefin can be mentioned. It is preferable that the transparent resin sheet 10 has high heat resistance. Considering that the thickness of the transparent resin sheet 10 corresponds to the width of the light transmission band of the louver layer, for example, it may be appropriately set within the range of 30 to 90 μm, 40 to 80 μm, 45 to 70 μm, or 50 to 60 μm. The thickness of the transparent resin sheet 10 is determined as the average of the values measured at any 10 or more locations.

[0012] Specific methods for performing the surface modification treatment include, for example, excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation. Here, the surface modification treatment refers to a treatment that improves the wettability with water or polar solvents by imparting polar functional groups containing oxygen (such as hydroxyl groups, carboxyl groups, carbonyl groups, etc.) to at least a part of the surface of the transparent resin sheet 10. Known conditions for the surface modification treatment may be applied so that the wettability is improved.

[0013] FIG. 1(b) shows a state where a colored silicone paint containing a light-shielding material is applied to one main surface of the surface-modified transparent resin sheet 10 to form a coating film 15. As the liquid silicone, which is a material of the colored silicone paint, those that are cured by heat or active energy rays are preferable, and commercially available products can be used. The paint may contain an appropriate solvent. As the light-shielding material, which is a material of the colored silicone paint, powders of light-shielding materials are preferable, and carbon particles such as carbon black are more preferable. For example, by adding 5 to 15 parts by mass of carbon black to 100 parts by mass of liquid silicone and mixing well, a colored silicone paint suitable for coating can be obtained.

[0014] As a method for applying the colored silicone paint, for example, coater methods such as comma coater and spin coater, and printing methods such as screen printing and offset printing are preferable from the viewpoint of being able to apply thinly. The thickness of the coating film 15 of the colored silicone paint is appropriately set in consideration of the fact that the thickness of the light-shielding layer 20 formed after drying and curing corresponds to the width of the light-shielding band of the louver layer.

[0015] FIG. 1(c) shows a state in which the coating film 15 formed on one main surface of the transparent resin sheet 10 is dried and cured to form the light-shielding layer 20. The symbol G represents a state in which the solvent is vaporizing. The specific method of drying and curing is not particularly limited, and a known method according to the properties of the paint is applied. For example, a method of irradiating infrared rays using a heater, a method of blowing warm air, etc. can be mentioned.

[0016] The thickness of the light-shielding layer 20 after drying and curing of the coating film 15 is appropriately set, for example, in the range of 0.5 to 5.0 μm, 1.0 to 4.0 μm, 1.0 to 3.0 μm, 1.5 to 2.5 μm. The thickness of the light-shielding layer 20 is determined as the average of values measured at any 10 or more locations.

[0017] After the light-shielding layer 20 is formed on one main surface of the transparent resin sheet 10, the light-shielding layer 20 is formed in the same manner on the other main surface of the transparent resin sheet 10. Thereby, a laminated sheet 30 in which the light-shielding layers 20 are formed on both main surfaces of the transparent resin sheet 10 respectively is obtained. In addition, in this embodiment, the case where the surface modification treatment is performed one side at a time and the light-shielding layer 20 is formed one side at a time has been described, but the surface modification treatment may be performed on both sides simultaneously, or the light-shielding layer 20 may be formed on both sides simultaneously.

[0018] FIG. 2(a) shows a state in which the light-shielding layer 20 forming one main surface of the laminated sheet 30 is surface-modified. The symbol P represents plasma treatment which is an example of the surface modification treatment. Similarly, the surface modification treatment of the light-shielding layer 20 forming the other main surface is performed. Specific methods for performing surface modification treatment include, for example, excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation. Here, the surface modification treatment refers to a treatment that makes at least a part of the surface of the light-shielding layer 20 of the laminated sheet 30 capable of direct adhesion (solid-to-solid adhesion) without using an adhesive. Known conditions of the surface modification treatment may be applied so as to improve the adhesiveness.

[0019] FIG. 2(b) shows a state in which the laminated sheets 30 subjected to the surface modification treatment are overlapped and pressed. Since the surface of the light-shielding layer 20 is in a state where solid-to-solid adhesion is possible due to the previous surface modification treatment, the surfaces of the laminated sheets 30 to be adhered can be naturally adhered by bringing them into contact with each other. At this time, it is preferable to apply an appropriate pressure to expel the air between the laminated sheets 30.

[0020] The number of laminated sheets 30 laminated is not particularly limited and is appropriately set according to the area of the louver layer to be produced. The larger the number of laminated sheets, the wider the area of the louver layer cut out from the laminated block 40 can be. For example, 100 to 10,000 sheets can be mentioned.

[0021] By solid-to-solid adhering the desired number of laminated sheets 30, the repeating pitch of the transparent resin sheet 10 can be made smaller (narrower) when viewed in the stacking direction. If solid-to-solid adhesion is not performed and each laminated sheet 30 is adhered with another adhesive layer interposed therebetween, the repeating pitch of the transparent resin sheet 10 will become wider by the thickness of the adhesive layer.

[0022] FIG. 2(c) shows a state in which the laminated block 40 is sliced in the thickness direction. For example, by inserting a metal blade from the upper surface to the bottom surface of the laminated block 40, the louver layer 50 can be cut out. Reference numeral K indicates the position where the metal blade is inserted.

[0023] FIG. 3(a) shows the cut-out louver layer 50. The louver layer 50 is a sheet having the x-y plane as the main surface. The light transmission bands derived from the transparent resin sheet 10 and the light shielding bands derived from the light shielding layer 20 extend parallel to each other in the x-axis direction. The light transmission bands and the light shielding bands are repeated alternately at a constant pitch in the y-axis direction. The thickness direction of the louver layer 50 is the z-axis direction. Light incident parallel to the z-axis passes through the light transmission bands of the louver layer 50. A part of the light incident obliquely with respect to the z-axis is blocked by the light shielding bands. The thicker the louver layer 50 is, the less light can pass through unless it is substantially parallel to the z-axis, and the so-called viewing angle becomes narrower. Also, the narrower the repetition pitch of the light transmission bands of the louver layer 50 is, the narrower the viewing angle becomes.

[0024] FIG. 3(b) shows a state in which the transparent protective layer 60 is formed on both main surfaces of the louver layer 50. The transparent resin layer 60 is preferably a transparent film made of a transparent resin. For example, a film made of a relatively hard transparent resin such as polycarbonate or poly(meth)acrylate is preferred. As a method of adhering the transparent protective layer 60 to the main surface of the louver layer 50, an adhesive may be used. An adhesive made of a liquid silicone paint that becomes a transparent silicone rubber after curing is more preferred from the viewpoint of enhancing adhesiveness.

[0025] By the manufacturing method described above, a viewing angle control film made of the louver layer 50 provided with the transparent protective layer 60 on both main surfaces can be obtained.

Example

[0026] A PET sheet (A4360 manufactured by Toyobo Co., Ltd.) with a thickness of 50 μm was prepared as the transparent resin sheet, and its both surfaces were surface-modified by plasma treatment. A colored silicone paint was applied to one main surface of the PET sheet with enhanced wettability by the spin coater method. Here, the paint was prepared as follows. 10 parts by mass of carbon black (Denka Black Li400; manufactured by Denka Co., Ltd.) was added to 100 parts by mass of liquid silicone rubber (KE2061-70A / B; manufactured by Shin-Etsu Chemical Co., Ltd.), kneaded, and diluted twice by adding toluene to obtain a colored silicone paint. The coating film applied to the PET sheet was dried and cured at 145 °C, and a light-shielding layer (thickness after curing: 2 μm) was formed on one main surface. Similarly, a light-shielding layer was formed on the other main surface to obtain a laminated sheet. After surface modification by plasma treatment of the surfaces of the light-shielding layers of the plurality of laminated sheets produced, these surfaces were overlapped while being in contact with each other, laminated, and solid-phase adhered by applying a load of about 2 kg to obtain a laminated block. A louver layer was cut out from the laminated block to obtain a viewing angle control film (length × width × thickness: 50 mm × 100 mm × 0.20 mm) composed of the target louver layer. Furthermore, polycarbonate films were adhered to both main surfaces of the louver layer with an adhesive.

[0027] A schematic diagram of the laminated structure when the main surface of the louver layer obtained in this example is viewed in plan is shown in FIG. 4. Since the width of the light-transmitting band derived from the PET sheet is 50 μm and the width of the light-shielding band derived from the light-shielding layer is 4 μm, the repeating pitch of the light-transmitting band is 54 μm. Such a louver layer with a narrow pitch was difficult to manufacture by conventional methods, but this could be realized by the present invention. Also, the louver layer has become thinner than before, and the total light transmittance has improved. Moiré is less likely to occur even when installed in a high-resolution display such as an organic EL.

Explanation of Reference Numerals

[0028] 10... transparent resin sheet, 15... coating film, G... gas from which the solvent has vaporized, P... plasma treatment, 20... light-shielding layer, 30... laminated sheet, 40... laminated block, K... position to be sliced, 50... louver layer, 60... transparent protective layer

Claims

1. A step of surface-modifying both main surfaces of a transparent resin sheet, applying a colored silicone paint containing a light-shielding material to each main surface, and drying and curing to obtain a plurality of laminated sheets in which light-shielding layers are formed on one main surface and the other main surface of the transparent resin sheet; After surface-modifying the light-shielding layers forming both main surfaces of the plurality of laminated sheets, while bringing the light-shielding layers into contact with each other, overlapping and pressing the laminated sheets together to laminate them, thereby obtaining a laminated block in which the laminated sheets are adhered to each other; A step of cutting out a louver layer from the laminated block; A method for manufacturing a viewing angle control film, comprising:

2. The method for manufacturing a viewing angle control film according to claim 1, further comprising a step of forming a transparent protective layer on at least one of both main surfaces of the louver layer.

3. The method for manufacturing a viewing angle control film according to claim 1, wherein the method of surface-modifying both main surfaces of the transparent resin sheet is excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation.

4. The method for manufacturing a viewing angle control film according to claim 1, wherein the method of surface-modifying the light-shielding layer is excimer light irradiation, plasma irradiation, corona irradiation, or UV light irradiation.

5. The method for manufacturing a viewing angle control film according to claim 1, wherein the method of applying the colored silicone paint is a coater method or a printing method.

6. The method for manufacturing a viewing angle control film according to any one of claims 1 to 5, wherein the thickness of the transparent resin sheet is 30 to 90 μm and the thickness of the light-shielding layer is 0.5 to 5.0 μm.

Images