JP2008090068A - Light controlling film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more selectively receive light incident on a film at a shallow angle and to give a light controlling property to a single polymer resin film itself by using a light controlling film which can transmit incident light without scattering in the film to simplify a manufacturing step of a light controlling film and to provide the film at a low cost. <P>SOLUTION: In a transparent high polymer resin film, about in parallel with a molecule aligning direction of the high polymer resin film and in a film thickness direction, a stripe-shaped craze region is uniformly provided in an inclined direction to a film thickness direction and optical anisotropy is given to a single film itself. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light controllable film, and more particularly, to a polymer resin film imparted with optical anisotropy that selectively transmits light incident on the film.

  In conventional light control films, louver films are known as light collimating films, light control films, and light directing films. For example, U.S. Pat. No. Re. No. 27,617 discloses a method of making a light control film by scraping a billet of layers in which plastics having different optical densities are alternately stacked, in the thickness direction. U.S. Pat. No. 3,198,860, Japanese Examined Patent Publication No. Sho 62-38142, Japanese Patent Laid-Open No. Hei 4-232719, etc. also disclose a method of cutting a film from a billet.

  However, in the technique of cutting a film from the billet, the process starts with forming a billet, and a process of obtaining a thin film with a wide width from the billet. A smoothing process is required. Since both of these require high technology and a large amount of capital investment, it cannot be expected that products will be provided at low cost.

  Japanese Patent Laid-Open No. 64-77001 proposes a “light control plate and method for manufacturing the same” having a uniform film quality that selectively scatters only specific incident light. The light control plate described in this publication can selectively scatter only incident light having a specific angle without bonding sheets made of a resin composition in two phases. Is obtained.

  However, in the light control plate described in JP-A No. 64-77001, the resin composition is made of a compound having one or more polymerizable carbon-carbon double bonds in the molecule having a difference in refractive index. Therefore, since it is necessary to cure the resin composition after applying the resin composition on the substrate, the manufacturing process is complicated and disadvantageous in terms of cost.

  In JP-A-9-166702, a transparent plastic single layer or multilayer film, wherein at least one of the films is substantially perpendicular to the surface and is optically anisotropic due to uniform crazing (cracking) in a certain direction A light control film having properties and a method for producing the same are disclosed.

  In order to selectively receive more light incident at a shallow angle with respect to the film surface, install the light source so that the incident angle is deeper away from the film surface, or tilt the film itself with respect to the light source. It is necessary to arrange it.

  In the light control film disclosed in Japanese Patent Laid-Open No. 9-166702, when the film itself is disposed obliquely with respect to the light beam, crazing (cracking) of the light control film is substantially omitted from the film surface. Because it is formed perpendicularly, light incident at a shallow angle is reflected at crazing (cracks) at an acute angle, so that light is easily scattered within the film, and light incident at a shallow angle with respect to the film surface is scattered. It is not a light control film that can be transmitted without any problems.

U.S. Pat. No. Re. 27,617 US Pat. No. 3,198,860 JP-B 62-38142 JP-A-4-232719 JP-A 64-77001 JP-A-9-166702

  The present invention is an invention devised in view of the problems of the prior art as described above, and its object is to selectively receive more light incident at a shallow angle with respect to the film. A light-controllable film that can transmit received light without scattering in the film, by providing light controllability to a single polymer resin film itself, simplifying the manufacturing process, and inexpensive It is to provide.

  In order to solve the above-mentioned problems, means taken by the present invention will be described below with reference to the drawings. The structure of the light controllable film according to claim 1 is such that the transparent polymer resin film 10 is substantially parallel to the molecular orientation direction of the polymer resin film 10 as shown in FIGS. The striped craze 20 region in the oblique direction is uniformly provided in the thickness direction of the film, and optical anisotropy is imparted to the single film itself.

  The craze 20 region referred to here includes both a surface craze appearing on the surface of the polymer resin film 10 and an internal craze generated therein, and refers to a region having a fine crack-like pattern. The craze 20 is composed of molecular bundles (fibrils) and voids, and has a structure similar to a sponge as a whole.

  Since the light controllable film of the present invention is provided with striped crazes 20 regions that are substantially parallel to the molecular orientation direction of the transparent polymer resin film 10 and oblique to the thickness direction of the film, FIG. As shown in FIG. 4, light that is shallowly incident between the crazes 20 formed in an oblique direction in the thickness direction of the film is transmitted as it is, or reflected at a shallow angle and transmitted through the film. In this case, the occurrence of irregular reflection within the thickness of the film is rare.

  The range of the light controllability of this film varies depending on the angle and depth of the craze with respect to the thickness direction of the polymer resin film 10 and the difference in thickness of the polymer resin film 10 itself. That is, since this light controllability is expressed by a craze generated in a single polymer resin film 10 itself, the film can be generated by specifying the polymer resin film and the craze generated in the film 10 itself. It is easy to standardize the range of light controllability.

  As shown in FIGS. 5 and 6, the light controllable film manufacturing method formed by forming a craze has a transparent polymer resin film 10 held in a tensioned state with a tip 41 having an acute angle. 40 is pressed to bend the polymer resin film 10 substantially in parallel with the molecular orientation direction to form a local bent portion 11, and then the polymer resin film 10 is brought into contact with the tip of the support 40. On the other hand, by pulling in the direction perpendicular to the folding line in the bent portion, a continuous stripe-shaped craze 20 region can be formed substantially parallel to the molecular orientation direction of the polymer resin film.

  In the manufacturing process described above, by adjusting the angle of the support 40 having an acute angle at the tip 41 pressed against the surface of the transparent polymer resin film 10 held in a tension state, the surface of the support 40 is brought into contact with the film surface. Thus, a light controllable film can be obtained in which striped crazes 20 are uniformly provided in an oblique direction substantially parallel to the molecular orientation direction of the polymer resin film 10 and in the thickness direction of the film.

  As described above, as an effect of the present invention, the transparent polymer resin film that is generally used has an angle dependency on transmitted light in a simple process of applying a specific crazing process, that is, A light controllable film having optical anisotropy can be produced with high productivity.

  Therefore, the light controllable film of the present invention does not require a special and expensive material or a complicated manufacturing process. Therefore, the light controllable film is very inexpensive as compared with the conventional film, and is wide and long. Because it can be freely manufactured, there are almost no restrictions on dimensions, and it has the functions of a diffusion sheet and a light guide plate in the backlight, and it is widely used not only in the electrical field such as various displays but also in the building material field such as window glass and indoor partitions The light controllable film that can be provided is produced.

  As shown in FIGS. 1 and 2, the light controllable film 60 of the present invention has a striped pattern in the transparent polymer resin film 10 that is substantially parallel to the molecular orientation direction and oblique to the film thickness direction. Since the craze 20 region is provided, as shown in FIG. 3, the light incident substantially parallel between the crazes 20 formed in a stripe shape is transmitted as it is. Further, as shown in FIG. 4, the light incident on the film surface at a shallow angle is reflected by the craze at a shallow angle and transmitted through the film, so that the directionality of the light becomes constant.

  In addition, the light controllable film 60 of the present invention is a light controllable film that also functions as a diffusion film by scattering incident light in the film by adjusting and arranging the angle of the film relative to the light source.

  As a result, the transparent resin film 10 exhibits so-called light controllability that occurs when light incident through the film 10 travels straight and reflects depending on an incident angle in the craze 20 region. That is, this light controllability is expressed by the single polymer resin film 10 itself. The range of the light controllability varies depending on the angle and width of the craze with respect to the thickness direction of the polymer resin film 10, the depth of the craze, the thickness of the polymer resin film 10 itself, and the like.

  Next, in the method for producing a light controllable film, as shown in FIG. 5 or FIG. 6, a support 40 having a sharp tip 41 on the transparent polymer resin film 10 held in tension is provided. Since it presses, the local bending part 11 is formed there substantially parallel to the molecular orientation direction of the polymer resin film 10. A craze 20 is generated in the bent portion 11. Moreover, what is necessary is just to select arbitrarily the angle of the bending part 11 of the polymer resin film 10 formed by pressing the support body 40 according to the thickness of the polymer resin film 10, a hardness, etc. FIG.

  In the manufacturing process described above, by adjusting the angle of the support 40 having an acute angle at the tip 41 pressed against the surface of the transparent polymer resin film 10 held in a tension state, the surface of the support 40 is brought into contact with the film surface. Thus, a light controllable film can be obtained in which striped crazes 20 are uniformly provided in an oblique direction substantially parallel to the molecular orientation direction of the polymer resin film 10 and in the thickness direction of the film.

  In addition, in the light controllable film obtained by the said manufacturing method, as shown in FIG. 7 of the measurement result described in an Example below, the fall of tensile strength is hardly seen. This is because the fibrils generated in the craze 20 bear the stress.

The light controllable film and the method for producing the same according to the present invention will be described below in detail with reference to the drawings. However, these are representative ones, and the present invention is not limited to these examples. .

  As shown in FIGS. 1 and 2, the light controllable film according to the present example has a molecular orientation direction of a transparent polymer resin film 10 made of polyvinylidene fluoride (PVDF) having a thickness of 25 μm, which is generally commercially available. Striped craze 20 regions having an interval of about 20 μm are provided substantially in parallel and obliquely in the thickness direction of the film (within a range of approximately 90 to 60 degrees with respect to the film surface). The craze 20 penetrates not only the surface of the polymer resin film 10 but also in its thickness direction, but does not penetrate in part but stops in the middle of the thickness direction.

  In the present embodiment, polyvinylidene fluoride is used as the transparent polymer resin film 10, but other than this, as long as the craze 20 can be formed, for example, polystyrene, polyethylene, polypropylene, polyester, polyamide, etc. May be adopted. Polyvinylidene fluoride has a wide use temperature range from a low temperature to a high temperature, has flexibility, is excellent in mechanical properties, has extremely good weather resistance, does not change transparency and flexibility, and is excellent in chemical resistance. Therefore, when used in applications requiring these conditions, it is desirable to employ polyvinylidene fluoride as the polymer resin film 10.

  Next, examples of the method for producing a light controllable film according to the present invention will be described below. As shown in FIG. 5 or FIG. 6, in this embodiment, an auxiliary tool 50 (hereinafter simply referred to as an auxiliary tool) that adjusts the tension of the polymer resin film 10 by moving up and down by a spring and a screw, and a tip 41 has an acute angle. A crazing device including the support 40 is used. First, the front end portion 41 of the support 40 is pressed against the surface of the transparent polymer resin film 10 made of polyvinylidene fluoride having a thickness of 25 μm held in a tension state and bent, and the polymer resin film 10 is bent. A constant tension is applied by the auxiliary tool, and the polymer resin film 10 is pulled in the direction of the arrow while contacting the support 40.

  Thereby, a continuous craze 20 region is formed substantially parallel to the molecular orientation direction of the polymer resin film 10. By changing this tension, the interval between the crazes 20 and the width of the craze 20 itself can be adjusted.

  As described above, when the polymer resin film 10 is pulled, for example, a winder (not shown) including a winding roller may be employed. The angle of the tip 41 of the support 40 may be arbitrarily selected, and the bending angle of the polymer resin film 10 may be adjusted by moving the auxiliary tool 50 up and down, adjusting the height of the support 40 itself, or the polymer resin film. What is necessary is just to select arbitrarily by the change of 10 pull angles, etc. Further, the support 40 may be fixed by attaching a roller (not shown) rotatably supported at the tip end portion 41 thereof. Since this roller rotates freely according to the movement of the polymer resin film 10, the surface of the film 10 is prevented from being damaged.

  In the manufacturing process described above, by adjusting the angle of the support 40 having an acute angle at the tip 41 pressed against the surface of the transparent polymer resin film 10 held in a tension state, the surface of the support 40 is brought into contact with the film surface. Thus, a light controllable film can be obtained in which striped crazes 20 are uniformly provided in an oblique direction substantially parallel to the molecular orientation direction of the polymer resin film 10 and in the thickness direction of the film.

  In the light controllable film of the present invention, the craze 20 region can be impregnated with additives such as a colorant and a stabilizer. In this case, the craze 20 itself is composed of molecular bundles and voids, and is similar to the sponge structure as a whole. An additive layer is formed, and in addition to the action of the invention according to claim 1, functions according to use can be expressed.

  When this additive is a colorant, color variations according to the use of the polymer resin film 10 can be obtained, and transmission of light can be suppressed. When the additive is an ultraviolet absorber, the polymer resin film 10 itself is prevented from being deteriorated or discolored by absorbing ultraviolet rays. In the case where the additive is a stabilizer, molecular decomposition or the like is suppressed. These functions improve the durability of the polymer resin film 10 itself. When the additive is a plasticizer, the polymer resin film 10 is plasticized to improve its flexibility.

  As the colorant to be impregnated in the Craze 20 region, those excellent in dispersibility, heat resistance, weather resistance, water resistance, chemical resistance and the like are desirable. For example, oil-soluble dyes as dyes, azo-based, phthalocyanine-based, anthraquinone-based, quinacridone-based organic pigments, and oxides, sulfides, lead chromates, ferrocyanides, silicates, carbon blacks, etc. as inorganic pigments . In addition to the above colorants, the additive layer includes UV absorbers such as benzotriazole and 2-hydroxy-4-methoxy-benzophenone, flame retardants such as phosphate esters and halogenated hydrocarbons, inorganic lead, metal soap, organic Stabilizers such as tin compounds and plasticizers such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP) can be said to be suitable for use.

With respect to the light controllable film according to the present invention thus obtained, the tensile strength was measured by the following method. A sample having a thickness of 25 μm × length 15 mm × width 3 mm is attached to a tensile tester (not shown) manufactured by Toyo Baldwin Co., Ltd., and pulled at a tensile speed of 10 mm / min until the sample breaks. From this tensile test result, the tensile strength (σ) is obtained using the following equation.
σ = P / S
Here, P is the maximum load applied to the sample, and S is the cross-sectional area of the sample.

  From this measurement, the results shown in FIG. 14 were obtained. It can be seen from FIG. 7 that there is almost no decrease in the tensile strength of the light controllable film due to the formation of crazes.

It is perspective explanatory drawing which shows the Example of the light controllable film which concerns on this invention. It is sectional explanatory drawing which shows the Example of the light controllable film which concerns on this invention. It is explanatory drawing which shows the state in which light entered into the light controllable film which concerns on this invention. It is explanatory drawing which shows the state from which the incident angle of the light in FIG. 3 differs. It is explanatory drawing which shows one Example of the manufacturing method of the light controllable film which concerns on this invention. It is explanatory drawing which shows the support body vicinity in FIG. It is a graph which shows tensile strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polymer resin film 11 Bending part 20 Craze 30 Press body 40 Support body 41 Front-end | tip part 50 Auxiliary tool 60 Light controllable film which concerns on this invention

Claims (1)

  A transparent polymer resin film is provided with striped craze regions that are substantially parallel to the molecular orientation direction of the polymer resin film and that are oblique in the thickness direction of the film, and are optically different from each other. A light controllable film characterized by imparting directionality.

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