JPH09166702A - Light-controlling film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wide and long film having angle dependence of transmission for light by a simple production process. SOLUTION: A film 2 comprising a transparent plastic single layer film such as polyethylene or a multilayered film produced by laminating a plastic film with other films is dipped in a solvent which does not dissolve the film 2 and/or in a soln. of a surfactant for a specified time at specified temp. Then the film is wound on a roll 9 having 5-50mm diameter to give distortion to the film so that craze is uniformly produced perpendicular to the film surface and parallel to the width direction of the roll 9. Thus, a light-controlling film having angle dependence of transmission for light can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control film and a method for manufacturing the same, and more particularly, to a plastic film which has a transparent optical anisotropy for selectively blocking light incident on the film at a shallow angle. It is related to the technology that can be given to.

[0002]

2. Description of the Related Art Light control films are conventionally known as light ray-collimating plastic films, light ray control films, light directing films, or louver films, and are well known. For example, US Patent R
e. No. 27,617 (Olsen)
A method is disclosed for making a light control film by shaving the billet of alternating layers of relatively low optical density and relatively high optical density layers in the thickness direction. In addition, U.S. Pat. No. 3,198,860 and Belgian Patent 559,15
Japanese Patent, Japanese Patent Publication No. 62-38142, JP-A-4-
No. 232719 is known, but all are patents relating to a method of shaving a film from a billet.

However, there are various problems in the manufacturing method of cutting a film from these billets. Primarily,
Forming the billet itself is a costly and time consuming task. Secondly, the abraded surface becomes an irregular surface, which impairs the light transmission and thus makes the surface optically smooth, for example, by heating and pressing or laminating a protective film. Is required. Thirdly, it is a very difficult task to obtain a thin film having a constant thickness from a billet as wide as possible and long.

Further, in Japanese Patent Laid-Open No. 2-97904, a transparent resin is compression-molded by using a mold in which a large number of grooves are machined to form a transparent film having a large number of grooves, and then the inside of the grooves is formed. Disclosed is a method for producing a light control film by making a light absorbing material. However, even with this method, the groove becomes large in terms of the machining accuracy of the groove of the die and the accuracy of compression molding, and the light absorption becomes unnecessarily large. It is difficult to stand the side surfaces vertically, which causes a drawback that the controllability of light is reduced.

Further, as a method for improving these drawbacks, a method of forming a transparent film having a large number of grooves using a photocurable resin and forming a light shielding layer inside the grooves, or a method of forming a transparent film A method has been proposed in which a laminated film having a liquid crystal layer sandwiched between them is formed and the liquid crystal layer is oriented so that the light transmittance has an angle dependency. However, these methods also have problems that the manufacturing process is complicated and that a special material is used, so that the cost is increased.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its object is to use a very general and inexpensive material, and The purpose of the present invention is to enable a wide and long light control film to be manufactured with high productivity by a simple manufacturing process.

[0007]

[Means for Solving the Problems] In order to solve the above problems, as a result of earnest research, as a result, among commonly used plastic films, for example, dipping in a solvent that does not dissolve the film itself or an interface lubricant is used. If you do, there is a phenomenon called fine cracking called crazing. This is caused by an increase in internal stress of the plastic material due to the solvent or the surfactant, and is accompanied by a decrease in transparency and other physical properties. Therefore, it is usually avoided to avoid the occurrence of the plastic material. Is used. In the present invention, conversely, by positively controlling and adding this crazing generation condition, it is possible to uniformly form cracks in a certain direction perpendicular to the surface on the plastic film, whereby the light transmittance of the film is increased. It has been found that the angle dependence can be given to the present invention, and the present invention has been completed.

That is, the invention described in claim 1 is a transparent plastic single-layer or multi-layer film,
At least one layer of the film is a light control film, which is characterized by having optical anisotropy due to uniform crazing (cracking) in a certain direction substantially perpendicular to the surface.

In the invention according to claim 2, the layer having optical anisotropy due to the crazing is a polystyrene film, a polymethylmethacrylate film,
The light control film according to claim 1, which is one of a polycarbonate film and an amorphous polyethylene terephthalate film.

The invention according to claim 3 is a method of manufacturing a light control film, which comprises the following steps (1) and (2). (1) A step of immersing a transparent plastic single-layer or multi-layer film in a solvent that does not dissolve the film and / or a solution of a surfactant at a predetermined temperature and for a predetermined time. (2) Then, by pulling the film in a solution of the solvent and / or a surfactant or from a solution of the solvent and / or a surfactant and winding the film on a roll to give a strain, A step of forming a uniform craze on the film, which is substantially perpendicular to the surface and parallel to the width direction.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of materials and processing methods used in the light control film and the manufacturing method thereof of the present invention will be described. First, as described above, the light control film of the present invention is a transparent plastic single-layer or multi-layer film, and at least one layer of the film is substantially perpendicular to the surface, and uniform crazing in a certain direction ( It is a light control film having optical anisotropy due to cracking.

When the film is a single layer,
It is necessary that the film itself is not dissolved by a specific solvent and / or a surfactant, and that it is easy to form crazes. Examples of such a film include a polystyrene film, a polymethylmethacrylate film, a polycarbonate film, and an amorphous polyethylene terephthalate film (A
-PET film) and the like.

When the film is a multi-layer film, at least one of the films is a film capable of forming crazes without being dissolved by the above-mentioned specific solvent and / or surfactant, and other layers. Is preferably used as a base film or a protective film, which is not dissolved by the specific solvent and / or surfactant and does not cause craze. Such a transparent film which does not cause craze can be obtained by selecting the film for forming the craze and the specific solvent and / or surfactant used in combination with the film, and then selecting the solvent and / or the surfactant. A film that is stable with respect to the above may be appropriately selected and used.

Therefore, when any one of the above polystyrene film, polymethylmethacrylate film, polycarbonate film and amorphous polyethylene terephthalate film is used as a film for forming crazes, it is dipped to form crazes. As the solvent for facilitating, for example, alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, hydrocarbons such as hexane and heptane, and ketones such as acetone and methyl ethyl ketone, or,
These mixed liquids are mentioned, and it can be appropriately selected and used from these. In this case, as the film on the side of the multilayer film where the craze is not formed, for example, a biaxially oriented polyethylene terephthalate film (OPET) or a biaxially oriented nylon film (O
N) A biaxially oriented polypropylene film (OPP) or the like can be used.

In the above description, alcohols and other solvents are exemplified as the immersion liquid used for facilitating formation of crazes on the film, but a surfactant may be used in addition to the solvent. Among these surfactants, those having particularly strong penetrating power are preferable, and examples thereof include polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, alkylbenzene sulfonate, dialkyl sulfosuccinate, and a mixture thereof. Further, the solvent and the surfactant may be used at the same time.

As a laminating method for producing the above-mentioned combination of multilayer films, any of conventionally known dry lamination method, extrusion lamination method and the like can be used, but in order to maintain transparency as much as possible, dry lamination method is used. Method is preferred. In the case of the dry lamination method, the adhesive to be used may be a two-component reaction type urethane adhesive such as polyol and isocyanate, or a photo-curing type or electron beam-curing type adhesive.

The light control film of the present invention is a transparent plastic single-layer or multi-layer film as described above.
A film with optical anisotropy that selectively blocks light incident at a shallow angle to the film by uniformly forming crazes that are substantially perpendicular to the surface and parallel to the width direction. First, the craze forming method will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating the main part of an embodiment of the light control film manufacturing apparatus of the present invention. The light control film manufacturing apparatus 1 of FIG. 1 has a film supply unit 3 for supplying a transparent plastic single-layer or multi-layer film 2 and a predetermined solvent and / or surfactant solution 4 for the film 2. The dipping tank 5 equipped with the guide rolls 6a, 6b, 6c, 6d for dipping at the temperature and time, and by applying the strain by winding the film after the dipping on the strain imparting roll 9 having a diameter of 5 to 50 mm, A craze forming section 8 (which may be provided in the dipping tank) for uniformly forming crazes parallel to the width direction and substantially perpendicular to the film surface, a solvent remaining in the film, and / or a surfactant. It is composed of a drying or washing / drying section 10 for removing the agent, and a winding section 11 for winding the film.

The roll-shaped long film 2 continuously supplied from the film supply unit 3 is fed into a dipping tank 5 filled with a solution 4 of a solvent and / or a surfactant, and dipped for a certain period of time. After that, it moves to the craze forming unit 8. At this time, the immersion time varies depending on the material and thickness of the film and the type of immersion liquid.
It is determined by adjusting the path (length) in the dipping tank and the film feeding speed so that the dipping can be performed for the required time. Further, the temperature of the immersion liquid may be room temperature when a solvent is used, but when a solution of a surfactant is used, it can be heated to accelerate permeation.

Then, the film 2 moved to the craze forming section 8 is pressed against the surface of the strain imparting roll 9 having a diameter of 5 to 50 mm to give an internal strain parallel to the width direction, and as a result, the film surface is subjected to the internal strain. Crazes that are substantially vertical and parallel to the width direction are uniformly formed. The depth and density of crazes formed on the film depend on the immersion time in a solvent,
Because it is affected by the radius of curvature of the strain imparting roll,
With the type of film material, thickness, type of solvent, etc.,
It is also necessary to determine the diameter of the strain imparting roll in an appropriate range. Usually, the diameter of the strain imparting roll is preferably 5 to 50 mm, more preferably 5 to 20 mm.

When the diameter of the strain imparting roll is less than 5 mm, the density of the craze is already sufficient, and there is no need for it. Rather, the strain applied to the film becomes too strong, and the workability also deteriorates. It is not preferable because it exists. On the other hand, when the diameter of the strain imparting roll exceeds 50 mm,
The strain applied to the film is weakened and the density and depth of the craze are lowered, which is not preferable. In the formation of the craze as described above, when the film used is a multi-layer film, that is, a laminated film of a film that forms the craze and a film that does not form the craze, the film side that forms the craze gives strain. The film is supplied so that it is located outside the roll.
By distorting the film in such an orientation,
It is possible to effectively form crazes.

The film on which the craze is formed as described above is then sent to the drying or washing / drying section 10 to remove the solvent and / or the surfactant remaining in the film, and then wound up. Taken up in part 11. The light control film thus obtained may be used by cutting it to a required size as it is, but further, a transparent film, a resin plate, a glass plate or the like may be laminated on one side or both sides of the light control film before use. May be. The light control film by such craze uses a cheap material and can obtain a wide and long film in a simple process. Therefore, the cost is significantly higher than that of the conventional light directing film and louver film. Since it can be downed, it can be widely used not only in the field of electric appliances such as various displays, but also in the field of building materials such as window glass and interior partitions.

FIG. 2 is a schematic diagram for explaining the light control function of the light control film of the present invention. In FIG. 2, the light control film 12 of the present invention has a transparent plastic film 13 having striped crazes 14 which are substantially perpendicular to the surface of the film and are parallel to the surface of the film. The incident light 15a that is substantially vertical, that is, the incident light 15a that is substantially parallel to the craze 14 is transmitted, but the incident light 15b at a shallow angle (oblique angle) with respect to the film surface is reflected and scattered by the craze and blocked. It Therefore, the light control film
When the other side is seen through 12, it has a light control function that the other side can be seen from a certain range of angles, but cannot be seen from an angle outside the range.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 As a transparent plastic film, a biaxially stretched polystyrene film having a thickness of 300 μm (hereinafter OP
S) [manufactured by Santo Clear Mitsubishi Chemical Co., Ltd.] was immersed in isopropyl alcohol for 1 minute at room temperature using the apparatus shown in FIG. 1 and then wound around a strain-applying roll having a diameter of 10 mm for half a round to form crazes. Subsequently, the residual solvent was dried with warm air to prepare the light control film of Example 1.

(Example 2) A multilayer film was used as a transparent plastic film, and a biaxially oriented polystyrene film having a thickness of 100 μm (manufactured by Santo Clear Mitsubishi Chemical Co., Ltd.) (film for forming crazes) and a thickness 10
A 0 μm biaxially oriented polyethylene terephthalate film [Lumirror T-60 Toray Co., Ltd.] (a film that does not form crazes) was laminated by a dry lamination method to form a transparent multilayer film. Then, this film was attached to the device shown in FIG. 1 so that the OPS side was on the outside with the strain imparting roll portion, and the film was treated under the same conditions as in Example 1 to form crazes in the OPS, and the light of Example 2 was used. It was used as a control film.

Example 3 An amorphous polyethylene terephthalate film (hereinafter referred to as A-PET) having a thickness of 400 μm (manufactured by Denki Kagaku Kogyo Co., Ltd.) was used as a transparent plastic film, and the apparatus shown in FIG. 1 was used. After immersing in hexane at room temperature for 30 seconds, it is wound around a strain-applying roll having a diameter of 5 mm for a half turn to form a craze.
The residual solvent was dried with warm air to prepare the light control film of Example 3.

Example 4 As a transparent plastic film, a polycarbonate film having a thickness of 400 μm (manufactured by Iupilon Mitsubishi Gas Chemical Co., Inc.) was used.
After dipping in a 30 wt% aqueous solution of polyoxyethylene alkyl ether at 40 ° C. for 2 minutes with the device shown in
A semicircle was wound around a strain-applying roll having a diameter of 10 mm to form crazes, and then the remaining surfactant component was washed off with water and dried with warm air to prepare a light control film of Example 4.

(Evaluation and Results) With respect to the light control films of Examples 1 to 4 prepared as described above, the angle dependence of the transmission visibility was measured and evaluated by the following method, and the results are shown in Table 1. It was The outline of the measuring method is shown in FIG. (Measurement method) A paper on which 10.5 points of characters are printed is placed on a horizontal surface, a light control film of a sample is fixed in parallel at a position 20 mm above the sample, and a cylinder having a diameter of 10 mm is passed from above the film of the sample, The angle (θ) was gradually changed from the vertical (0 °) in the plane orthogonal to the craze direction of the sample film, the letters on the lower paper were visually read, and the visibility was evaluated according to the following criteria. . (Evaluation Criteria) ○: legible △: legible although somewhat blurred ×: not legible

[0028]

[Table 1] As is clear from the results shown in Table 1, it is understood that the light control films of Examples 1 to 4 all have angular dependence in their transmission visibility. Therefore, according to the present invention, it is possible to manufacture a wide and long light control film having an angle dependency in transmission visibility by using an inexpensive transparent plastic film and by a simple manufacturing process.

[0029]

As described above in detail, according to the present invention, a generally used transparent plastic film is dipped in a solution of a specific solvent and / or a surfactant and wound on a roll. The light control film having the angle dependency of the transmitted light, that is, having the optical anisotropy can be produced with high productivity by a simple process of giving distortion by applying. Therefore, the light control film of the present invention does not require a special and expensive material or a complicated manufacturing process, and thus is much cheaper than a conventional one, and a wide and long one can be freely used. Since it can be manufactured in the same manner, there is almost no size restriction, and it is possible to provide a light control film which can be widely used not only in the electric field such as various displays but also in the field of building materials such as window glass and indoor partitions.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating the main part of an embodiment of a light control film manufacturing apparatus of the present invention.

FIG. 2 is a schematic view for explaining a light control function of the light control film of the present invention.

FIG. 3 is a schematic diagram illustrating a method for measuring the angle dependence of transmission visibility of the light control film of the present invention.

[Explanation of symbols]

1 Light Control Film Manufacturing Equipment 2 Film 3 Film Supply Section 4 Solvent and / or Surfactant Solution 5 Immersion Tanks 6a, 6b, 6c, 6d Guide Roll (Diameter 75 mm or More) 7 Cover 8 Craze Forming Section 9 Strain-Giving Roll (Diameter 5 to 50 mm) 10 Drying or washing / drying section 11 Rolling up section 12 Light control film 13 Transparent plastic film 14 Clazes 15a, 15b Incident light

Claims (3)

[Claims] 1. A single-layer or multi-layer film of transparent plastic, characterized in that at least one layer of the film has optical anisotropy due to uniform crazing in a certain direction substantially perpendicular to the surface. A light control film. 2. The layer having optical anisotropy due to crazing is any one of a polystyrene film, a polymethylmethacrylate film, a polycarbonate film, and an amorphous polyethylene terephthalate film. Light control film. 3. A method for producing a light control film, which comprises the following steps (1) and (2): (1) A step of immersing a transparent plastic single-layer or multi-layer film in a solvent that does not dissolve the film and / or a solution of a surfactant at a predetermined temperature and for a predetermined time. (2) Then, by pulling the film in the solution of the solvent and / or the surfactant or from the solution of the solvent and / or the surfactant and winding it on a roll to give a strain, A step of forming uniform crazes on the film, which are substantially perpendicular to the surface and parallel to the width direction.