JP6751566B2 - Light transmission direction control sheet - Google Patents

Description

The present invention relates to a light transmission direction control sheet through which only light rays having a specific incident angle are transmitted among the incident light bundles. More specifically, the present invention relates to a light transmission direction control sheet capable of realizing a narrow viewing angle when installed on a lighting, a display screen of various information display devices, or the like.

A peep prevention body that is installed on the display screen of information display devices such as mobile information terminals and automatic cash deposit payment machines, and can prevent peeping from the left and right sides and the opposite side without impairing visibility from the front side of the display screen. Is disclosed (Patent Document 1). The peep prevention body includes an antiglare layer in which light transmission bands and shading bands are alternately arranged, a translucent adhesive layer provided on one surface of the antiglare layer, and the adhesive layer. It has a three-layer structure in which a translucent layer provided on the other surface of the antiglare layer on the opposite side is laminated. The sticking layer is used by sticking to the display screen of the information display device.

Japanese Patent No. 3675752

It is required to improve the convenience of the user by incorporating the light transmission direction control sheet (peeping prevention body) inside the mobile information terminal. The translucent layer provided in the peep prevention body of Patent Document 1 has a sufficient thickness for the purpose of increasing the rigidity of the peep prevention body, and is not suitable for use in a narrow terminal. When the translucent layer of the peep prevention body is removed for the purpose of reducing the thickness, minute irregularities inevitably formed during manufacturing are exposed on the surface of the antiglare layer. Since light is diffusely reflected by the unevenness, the haze value becomes high, and there is a problem that the image transmitted through the antiglare layer cannot be clearly seen and the antiglare layer itself cannot be clearly seen. If this peep prevention body is adhered to the display screen, the above diffused reflection of light can be suppressed, but since it is difficult to see through (see through) the peep prevention body before bonding, the quality inspection of the peep prevention body is performed. There is a problem that makes it difficult to do.
Further, in the conventional peep prevention body, the refractive index of the transparent resin constituting the translucent layer and the refractive index of the transparent resin constituting the antiglare layer are different, so that the light transmittance is lowered due to the difference in the refractive index. There is also a problem that occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light transmission direction control sheet having an excellent light transmittance and capable of visually inspecting quality.

[1] A louver layer in which light transmission bands and light-shielding bands are alternately and repeatedly provided, a first transparent resin layer provided on the first surface of the louver layer, and a second surface of the louver layer. The second transparent resin layer is provided, and the difference between the refractive index of the light transmitting band and the refractive index of the first transparent resin layer, and the refractive index of the light transmitting band and the refractive index of the second transparent resin layer are provided. The difference between the two is less than 0.1, respectively.
[2] The arithmetic average roughness (Ra) of at least one of the outer surface of the first transparent resin layer and the outer surface of the second transparent resin layer is 0 μm to 3.0 μm, according to [1]. Light transmission direction control sheet.
[3] The light transmission direction control sheet according to [1] or [2], wherein the light transmission band, the first transparent resin layer, and the second transparent resin layer are formed of silicone rubber.
[4] The thickness of the louver layer is 200 μm to 500 μm, the thickness of the first transparent resin layer is 10 μm to 20 μm, and the thickness of the second transparent resin layer is 10 μm to 20 μm [1]. ] To the light transmission direction control sheet according to any one of [3].

According to the light transmission direction control sheet of the present invention, the interfacial reflection at the interface between the louver layer and the first and second transparent resin layers is reduced, so that the light transmittance is excellent. As a result, it is possible to suppress a decrease in the brightness of the installed display screen and obtain a sufficiently bright display screen even when the brightness of the backlight is set low. In addition, the power consumption of the backlight can be reduced. Further, since it has an excellent light transmittance, a quality inspection can be easily performed visually. Since these excellent effects are sufficiently exhibited even when the light transmission direction control sheet of the present invention is thinned, it can be easily incorporated inside the information display device.

It is sectional drawing which shows an example of the light transmission direction control sheet which concerns on this invention.

As shown in FIG. 1, the light transmission direction control sheet 10 according to the present invention has a louver layer 1 in which a light transmission band 2 and a light shielding band 3 are alternately and repeatedly provided, and a first surface of the louver layer 1. A first transparent resin layer 4 provided and a second transparent resin layer 5 provided on the second surface of the louver layer 1 are provided.
Each light transmission band 2 and each light shielding band 3 are formed along the thickness direction of the louver layer 1. In other words, the light transmission band 2 and the light shielding band 3 are alternately and repeatedly provided in the width direction (the direction orthogonal to the thickness direction) of the louver layer 1. In the louver layer 1, light is transmitted through the light transmission band 2 sandwiched between the light-shielding bands 3 along the thickness direction of the louver layer 1, that is, the thickness direction of the light transmission direction control sheet 10.

In the light transmission direction control sheet 10, the difference between the refractive index of the light transmission band 2 and the refractive index of the first transparent resin layer 4 and the difference between the refractive index of the light transmission band 2 and the refractive index of the second transparent resin layer 5 are Each is less than 0.1. Here, the difference between the refractive indexes is an absolute value.

In the present invention, the "refractive index" is the refractive index of the member with respect to vacuum, and means the absolute refractive index. This refractive index is obtained in accordance with the A method of JIS K 7142: 2014 (ISO489: 1999) "Plastic-How to obtain the refractive index".

The difference between the refractive index of the light transmittance band 2 and the refractive index of the first transparent resin layer 4 is less than 0.1, preferably less than 0.01, and more preferably zero, so that the difference from the louver layer 1 is zero. Interfacial reflection at the interface of the first transparent resin layer 4 is reduced, and the light transmittance is improved. Similarly, the difference between the refractive index of the light transmittance band 2 and the refractive index of the second transparent resin layer 5 is less than 0.1, preferably less than 0.02, and more preferably the substantial difference is zero. Interfacial reflection at the interface between the layer 1 and the second transparent resin layer 5 is reduced, and the light transmittance is improved. As a result, the light transmission direction control sheet 10 has excellent light transmission.

When the surface of the louver layer 1 is exposed without the transparent resin layer being provided, diffused reflection of light occurs on the exposed surface, so that the light transmission band 2 and the light shielding band 3 constituting the louver layer 1 pass through the louver layer 1 It is difficult to visually confirm that they are arranged regularly. On the other hand, by providing the first transparent resin layer 4 and the second transparent resin layer 5, the light transmission band 2 and the light shielding band 3 constituting the louver layer 1 are regularly viewed through the light transmission direction control sheet 10. It can be visually confirmed that they are arranged. As a result, quality control can be easily performed.

The arithmetic average roughness (Ra) of at least one of the outer surface (surface facing the outside) 4a of the first transparent resin layer 4 and the outer surface 5a of the second transparent resin layer 5 is preferably 0 μm to 3.0 μm. 0.0 μm to 0.5 μm is more preferable, and 0.0 μm to 0.2 μm is even more preferable.
Within the above range, the outer surface has smoothness equivalent to that of a mirror finish, and light scattering on the outer surface is further suppressed. As a result, it is possible to visually confirm that the light transmission band 2 and the light shielding band 3 constituting the louver layer 1 are regularly arranged through the first transparent resin layer 4 and the second transparent resin layer 5. It will be even easier. That is, quality control can be performed more easily. Further, it is possible to improve the optical characteristics such as the light transmittance of the light transmission direction control sheet 10.
In the present specification, the numerical range of "lower limit value to upper limit value" means a numerical range of "greater than or equal to the lower limit value and less than or equal to the upper limit value" unless otherwise specified.

From the viewpoint of improving the transparency of the light transmission direction control sheet 10, the arithmetic mean roughness (Ra) of both the outer surface 4a of the first transparent resin layer 4 and the outer surface 5a of the second transparent resin layer 5 is preferable as described above. The range is preferable.

In the present invention, the "arithmetic mean roughness (Ra)" is obtained in accordance with JIS B 0601: 2013 (ISO4287: 1997) "Specifications of Geometric Characteristics of Products".

[Material of light transmission band]
The material of the light transmission band 2 constituting the louver layer 1 is not particularly limited as long as it satisfies the above-mentioned relationship of refractive index, and for example, a resin having high transparency is preferable. Specifically, the light transmittance (light transmittance) when light is transmitted in the thickness direction of the louver layer 1 is 75% or more, preferably 85%, with respect to only the light transmission band 2 of the louver layer 1. A resin material having high transparency as described above is preferable. For example, highly transparent thermoplastic resins and thermocurable resins are used, and specific examples thereof include cellulose-based resins, polyolefin-based resins, polyester-based resins, silicone resins, polystyrene resins, polyvinyl chloride resins, acrylic resins, and polycarbonates. Examples include resin. Of these, silicone resin is preferable, and silicone rubber is particularly preferable in terms of heat resistance.

As the silicone rubber, for example, a silicone rubber composition generally called mirabable rubber, which comprises a diorganopolysiloxane having a molecular chain end sealed with a hydroxysilyl group or a vinylsilyl group and an organic peroxide; is bonded to a silicon atom in the molecule. A so-called addition reaction in which an organohydrogenpolysiloxane having at least three hydrogen atoms (= SiH bonds) bonded to a silicon atom in the molecule and a platinum-based catalyst are blended with the diorganopolysiloxane having at least two vinyl groups. Examples include mold organosilicone rubber compositions.

[Material of shading band]
The material of the light-shielding band 3 constituting the louver layer 1 is not particularly limited, and for example, the resin listed above is used as the material of the light transmission band 2 and a colorant such as a pigment or a dye is added thereto. Colored resins are suitable. The resin material forming the light transmitting band 2 and the resin material as the base material of the light transmitting band 3 may be the same or different, but the adhesiveness between the light transmitting band 2 and the light transmitting band 3 It is preferable that both resin materials are the same from the viewpoint that

The color tone of the light-shielding band 3 may be such that black, red, yellow, green, blue, light blue, etc. can be obtained as long as sufficient light-shielding property can be obtained. The color tone and light-shielding property of the light-shielding band 3 can be adjusted by the type and amount of the colorant added. Specifically, the light transmittance when irradiating light in the thickness direction of the louver layer 1 with respect to only the light shielding band 3 of the louver layer 1 is 20% or less, preferably 5% or less. It is preferable to have. Further, since the color tone of the light-shielding band is the color tone that is recognized when the louver layer 1 is viewed, it is preferable to design it in consideration of decorativeness.

Specific examples of the colorant include general organic pigments such as carbon black, iron oxide, titanium oxide, yellow iron oxide, disazo yellow, and phthalocyanine blue, or inorganic pigments. The colorant may be used alone or in combination of two or more. When a black pigment is not used, it is preferable to use a white pigment in combination in order to obtain good light-shielding properties.

[Width of light transmission band and shading band]
The widths of the light transmitting band 2 and the shading band 3 (thickness in the lateral direction of FIG. 1) can be freely set. The light transmittance of the louver layer 1 can be adjusted by the ratio of the width of the light transmission band 2 to the width of the light shielding band 3. The range of the viewing angle (visible angle) can be adjusted by the width of the light transmission band 2 and the thickness of the louver layer 1.

The width of the light transmission band 2 is preferably 100 to 200 μm, more preferably 120 to 150 μm, in consideration of achieving both prevention of peeping and good visibility of the display screen. The width of the light-shielding band 3 is preferably 10 to 50 μm, more preferably 10 to 30 μm. By adjusting each width within the above range, for example, a light transmission direction control sheet 10 having a light transmittance of 80% or more and a viewing angle of 90 to 120 ° can be obtained.

[Material of transparent resin layer]
The materials of the first transparent resin layer 4 and the second transparent resin layer 5 are not particularly limited as long as they satisfy the above-mentioned relationship of refractive index, and for example, the above-mentioned resin is suitable as the material of the light transmission band 2. .. A material having a light transmittance of 75% or more in the thickness direction of each transparent resin layer is preferable, and a material having a light transmittance of 85% or more is more preferable.

Specific examples thereof include cellulose-based resins, polyolefin-based resins (particularly cycloolefin polymers), polyester-based resins, silicone resins, polystyrene resins, polyvinyl chloride resins, acrylic resins, and polycarbonate resins. Suitable silicone rubbers include those exemplified in the above-mentioned light transmission band.
Among the above, silicone resins that are closer to the refractive index of air (1.003) than thermoplastic resins such as polycarbonate and PET (refractive index = 1.59 to 1.60) and have less loss of light transmittance due to interfacial reflection. (Refractive index = 1.43) is preferable, and silicone rubber (refractive index = 1.40 to 1.43) is more preferable in terms of heat resistance. When the transparent resin layers 4 and 5 are made of silicone rubber, the adhesion of the outer surfaces 4a and 5a of the transparent resin layer is remarkably improved (a feeling of tackiness can be imparted). Therefore, the transparent resin layer is brought into close contact with the surface of the display screen. The light transmission direction control sheet 10 can be easily installed.

The resin constituting each transparent resin layer contains, if necessary, additives known in the field of resin films such as ultraviolet absorbers, infrared absorbers, and colorants for the purpose of improving weather resistance and design. May be done.

The material of the first transparent resin layer 4 and the material of the second transparent resin layer 5 may be the same or different, but they are the same from the viewpoint that it is easy to satisfy the above-mentioned refractive index relationship. It is preferable to have. From the same viewpoint, it is more preferable that the materials of the first transparent resin layer 4 and the second transparent resin layer 5 and the material of the light transmission band 2 of the louver layer 1 are the same.

[Thickness of each layer]
The thickness of the louver layer 1 is preferably 100 μm to 5000 μm, more preferably 150 μm to 1000 μm, and even more preferably 200 μm to 500 μm. When the thickness of the louver layer 1 is within the above range, the viewing angle (visible angle) can be easily controlled.
The thickness of the first transparent resin layer 4 and the second transparent resin layer 5 is preferably 1 μm to 100 μm, more preferably 5 μm to 50 μm, and even more preferably 10 μm to 20 μm, respectively. When the thicknesses of the first transparent resin layer 4 and the second transparent resin layer 5 are in the above ranges, the rigidity and thinning of the light transmission direction control sheet 10 can be balanced.

The total thickness of the louver layer 1, the first transparent resin layer 4, and the second transparent resin 5 is preferably 100 μm to 5000 μm, more preferably 150 μm to 1000 μm, and even more preferably 200 μm to 500 μm.
When the thickness of each layer is equal to or greater than the lower limit of the above range, the rigidity of the light transmission direction control sheet 10 is increased, the operability when installed near the display screen of the information display device is improved, and the viewing angle (visible) is improved. Angle) can be easily controlled.
When the thickness of each layer is not more than the upper limit of the above range, the light transmission direction control sheet 10 is sufficiently thinned and can be easily incorporated into the information display device.

[Any transparent member]
A transparent member such as an arbitrary transparent layer or a transparent film may be provided on at least one of the outer surface 4a of the first transparent resin layer 4 and the outer surface 5a of the second transparent resin layer 5, for example, a known adhesive layer. Examples include an adhesive layer, a transparent film, and a protective sheet.

Examples of the material of the adhesive layer include an elastomer-based adhesive, an acrylic-based adhesive, a urethane-based adhesive, a rubber-based adhesive, and the like. Examples of the elastomeric pressure-sensitive adhesive include pressure-sensitive adhesives containing silicone rubber, silicone gel, urethane rubber, urethane gel and the like. When an elastomeric pressure-sensitive adhesive is used, it is preferable to apply a known mirror finish to the surface of the pressure-sensitive adhesive layer in order to enhance its transparency.

From the viewpoint of improving the optical characteristics of the light transmission direction control sheet 10, the refractive index of the above-mentioned arbitrary transparent layer, transparent member such as a transparent film, the light transmission band 2, the first transparent resin layer 4, and the second The difference from the refractive index of each constituent material of the transparent resin layer 5 is preferably less than 0.1, more preferably less than 0.02, and preferably substantially zero.
Further, from the viewpoint of improving the optical characteristics of the light transmission direction control sheet 10 and simplifying the sheet structure, other transparent members are provided on the outer surfaces of the first transparent resin layer 4 and the second transparent resin layer 5. It is preferable not to.

[Manufacturing method of light transmission direction control sheet]
The louver layer 1 constituting the light transmission direction control sheet 10 can be manufactured by, for example, the following method. First, a plurality of first sheets having a desired thickness made of the constituent material of the light transmission band 2 and a plurality of second sheets having a desired thickness made of the constituent material of the light-shielding band 3 are alternately laminated. Then, by heating and pressurizing, a block body in which these a plurality of sheets are integrated is formed.

Next, the louver layer 1 is obtained by slicing the block body on a cut surface perpendicular to the sheet surface. The thickness at the time of slicing (slice width) corresponds to the thickness of the louver layer 1. By slicing the block body on a surface inclined with respect to the sheet surface, the angle formed by the surface of the louver layer 1 and the shading band 3 can be adjusted.

The method of laminating the louver layer 1 and the transparent resin layers 4 and 5 and integrating them is not particularly limited, and a known method can be appropriately used.
As an example, there is a method of forming the first transparent resin layer 4 by applying a material for forming the first transparent resin layer 4 to the first surface of the louver layer 1 and curing the material. The second transparent resin layer 5 can be formed on the second surface of the louver layer 1 by the same method.

The light transmission direction control sheet 10 is obtained by laminating the louver layer 1 and the transparent resin layers 4 and 5 and forming the integrated laminate into a desired shape. The planar shape of the light transmission direction control sheet 10 is not particularly limited, and a shape such as a rectangle, a polygon, a circle, or an ellipse may be appropriately adopted according to the shape of the display screen to be installed.

[Use of light transmission direction control sheet]
By installing the light transmission direction control sheet 10 so as to cover the display screen in the vicinity of the display screen of the information display device, so-called peeping can be prevented. As an installation method, for example, the outer surface 4a of the first transparent resin layer 4 or the outer surface 5a of the second transparent resin layer 5 of the light transmission direction control sheet 10 formed in a rectangular shape is used as a transparent substrate constituting the display screen of the information display device. There is an installation method that makes it adhere to. The light transmission direction control sheet 10 may be installed on the outer surface of the device and exposed to the outside, or may be installed inside the device and installed in a state where it is difficult to be recognized from the outside. When the light transmission direction control sheet 10 is incorporated inside the information display device, for example, the outer surface 4a of the first transparent resin layer 4 is closely fixed to the transparent substrate constituting the display screen inside the device, and the second is It is preferable that the outer surface 5a of the transparent resin layer 5 is closely fixed to the transparent substrate forming the outer surface (a part of the housing) of the device. That is, it is preferable that the light transmission direction control sheet 10 is installed in a state of being closely sandwiched between two transparent substrates of the information display device which are separated from each other and face each other. When installed in this way, the air layer does not intervene between the two transparent substrates of the information display device and the transparent resin layers 4 and 5 of the light transmission direction control sheet 10, so that the decrease in light transmittance is suppressed. can do.

The extension direction of the light transmission band 2 (and the light shielding band 3) of the installed light transmission direction control sheet 10 and the side of the display screen frame may be parallel or non-parallel. In order to prevent the occurrence of moire fringes, the extension direction of the light transmission band 2 may be tilted with respect to the display screen frame (a bias angle may be added).

Examples are given below, but the present invention is not limited to these examples.
[Example 1]
The light transmission direction control sheet 10 shown in FIG. 1 was manufactured.
First, as a material for the light transmission band 2, a first sheet having a thickness of 125 μm made of transparent silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., trade name; KE-153-U) having a refractive index of about 1.43 is used. I prepared it.
Separately, as the material of the light-shielding band 3, the thickness is made of transparent silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KE-153-U) to which 15 parts by mass of carbon black is added to 100 parts by mass. A second sheet of 10 μm was prepared.
A plurality of first sheets and a plurality of second sheets were alternately laminated, and heated, vulcanized, and pressurized to form a block body in which the plurality of sheets were integrated.

The louver layer 1 was prepared by slicing the block body with a cut surface perpendicular to the sheet surface to a thickness of 310 μm.
Since the surface of the louver layer 1 was roughened by slicing, diffused reflection of light occurred on the surface, and the louver layer 1 appeared cloudy. Therefore, it is difficult to see through the single louver layer 1, and it is not possible to visually confirm whether or not the light transmission band 2 and the light shielding band 3 are regularly arranged.

Next, a liquid silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KE-1987) having a refractive index of about 1.43 was applied to the surface of the mirror-finished PET film using a screen printing machine. It was applied to a thickness of about 20 μm, and this coated surface was placed on the first surface of the louver layer 1 and heat-vulcanized and adhered. Then, the PET film was peeled off to form the first transparent resin layer 4 made of silicone rubber. In the same manner, a second transparent resin layer 5 made of silicone rubber was formed on the second surface of the louver layer 1 to obtain a light transmission direction control sheet 10.

When the light transmission direction control sheet 10 before the PET film was peeled off was visually observed through the light transmission direction control sheet 10, the light transmission bands 2 and the light shielding bands 3 constituting the louver layer 1 were regularly arranged, and the product was a good product without defects. Was easily confirmed.
Moreover, when there was a defect, it was easily confirmed visually that black spots or white spots were scattered irregularly.

The arithmetic average roughness (Ra) of the outer surface of each of the transparent resin layers 4 and 5 of the light transmission direction control sheet 10 obtained by peeling the PET film is measured by a surface roughness measuring machine (manufactured by Kosaka Laboratory Co., Ltd., trade name). : SE600), Ra was 0.1 μm on both sides, which was a smooth mirror surface equivalent to the surface of the mirror-processed PET film.
When the light transmittance of the light transmission direction control sheet 10 was measured using a haze meter (manufactured by Nippon Denka Kogyo Co., Ltd., trade name: NDH2000), the total light transmittance was 80% and the haze was 3. .. Here, the haze is calculated by the formula “haze (%) = Td / Tt × 100”. In the formula, Td represents the diffusion transmittance and Tt represents the total light transmittance.
The viewing angle of the light transmission direction control sheet 10 was about 65 ° in a plane orthogonal to the longitudinal direction in which the light transmission band 2 and the light shielding band 3 of the louver layer 1 were extended.

[Example 2]
A light transmission direction control sheet 10'was produced in the same manner as in Example 1 except that a rough-surfaced PET film was used.

When the light transmission direction control sheet 10'before peeling off the PET film was visually observed through it, the light transmission bands 2 and the light shielding bands 3 constituting the louver layer 1 were regularly arranged, and it was a good product without defects. I was able to confirm that easily.
In addition, when there was a defect, it was possible to easily visually confirm that black spots or white spots were scattered irregularly.

Examples show the arithmetic average roughness (Ra), light transmittance, haze, and viewing angle of the outer surfaces of the transparent resin layers 4 and 5 of the light transmission direction control sheet 10'of Example 2 obtained by peeling the PET film. When measured in the same manner as in 1, Ra = 2.6 μm, total light transmittance = 73%, haze = 41, viewing angle = about 65 °. The haze value was higher than that of Example 1, and the total light transmittance was lowered.

[Example 3]
A light transmission direction control sheet 10 ”was produced in the same manner as in Example 1 except that a PET film that had not been mirror-finished was used.

When the light transmission direction control sheet 10 "before peeling off the PET film was visually observed, the light transmission bands 2 and the light shielding bands 3 constituting the louver layer 1 were regularly arranged, and it was a good product without defects. I was able to confirm that easily.
In addition, when there was a defect, it was possible to easily visually confirm that black spots or white spots were scattered irregularly.

Examples show the arithmetic average roughness (Ra), light transmittance, haze, and viewing angle of the outer surfaces of the transparent resin layers 4 and 5 of the light transmission direction control sheet 10 "of Example 3 obtained by peeling the PET film. When measured in the same manner as in 1, Ra = 0.2 μm, total light transmittance = 78%, haze = 6, viewing angle = about 65 °.

[Comparative Example 1]
An epoxy adhesive (refractive index: about 1.55) having a thickness of 10 μm is applied to both surfaces of the louver layer 1 produced in Example 1, and the outer surface is mirror-finished via the adhesive layer on each surface. Each of the applied polycarbonate films having a thickness of 30 μm (refractive index: about 1.58) was adhered.
Through the above steps, a light transmission direction control sheet of Comparative Example was obtained, each of which had an adhesive layer and a polycarbonate film on both sides of the louver layer 1.

When the light transmission direction control sheet provided with the polycarbonate film on both sides was visually observed through the light transmission direction control sheet, the light transmission band 2 and the light shielding band 3 constituting the louver layer 1 were regularly arranged, and the product was a good product without defects. Was easily confirmed.
In addition, when there was a defect, it was possible to easily visually confirm that black spots or white spots were scattered irregularly.
However, as shown in the following results, the optical characteristics were inferior to those of the light transmission direction control sheet 10 of Example 1. It is considered that the cause of this is that large interfacial reflection occurred at each interface of the louver layer 1, the adhesive layer, and the polycarbonate film.

When the arithmetic average roughness (Ra), light transmittance, haze, and viewing angle of the outer surface of each polycarbonate film of the light transmission direction control sheet of Comparative Example 1 were measured in the same manner as in Example 1, Ra = 0.1 μm, all. The light transmittance was 77%, the haze was 6, and the viewing angle was about 65 °.
The haze value was higher than that of Example 1, and the total light transmittance was lowered.

[Comparative Example 2]
A light transmission direction control sheet was produced in the same manner as in Comparative Example 1 except that a roughened polycarbonate film (refractive index: about 1.58) was used.

When the light transmission direction control sheet provided with the polycarbonate film on both sides was visually observed through the light transmission direction control sheet, the light transmission band 2 and the light shielding band 3 constituting the louver layer 1 were regularly arranged, and the product was a good product without defects. Was easily confirmed.
In addition, when there was a defect, it was possible to easily visually confirm that black spots or white spots were scattered irregularly.
However, as shown by the results in Table 1, the optical characteristics were inferior to those of the light transmission direction control sheet 10 of Example 1. It is considered that the cause of this is that large interfacial reflection occurred at each interface of the louver layer 1, the adhesive layer, and the polycarbonate film.

The results of Examples 1 to 3 and Comparative Examples 1 and 2 are extracted and shown below. In Table 1, the "difference in refractive index" means the difference between the refractive index of the light transmission band (1.43) and the refractive index of the first transparent resin layer (1.43) in the examples, and is a comparative example. Means the difference between the refractive index of the light transmission band (1.43) and the refractive index of the epoxy adhesive (1.55). Further, "Ra" means the arithmetic mean roughness of the outer surface of the first transparent resin layer in the examples, and means the arithmetic mean roughness of the outer surface of the polycarbonate film in the comparative example.

From the results in Table 1, it is clear that the lower the arithmetic mean roughness Ra of the outer surface of the light transmission direction control sheet, the better the optical characteristics. Furthermore, from the results of Example 1 and Comparative Example 1 in which Ra is the same, it is clear that the optical characteristics are improved when the difference in refractive index is less than 0.1.

Although the present invention has been described above with reference to specific examples, it goes without saying that the technical scope of the present invention is not limited to the scope described in the above examples. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. Further, it is clear from the description of the scope of claims that the form to which such a modification or improvement is added may be included in the technical scope of the present invention.

The light transmission direction control sheet of the present invention is, for example, installed on the display screen of various information display devices and used as a sheet to prevent peeping, or attached to a lighting device or a sensor device and used as an optical filter. be able to.

1 ... Louver layer, 2 ... Light transmission band, 3 ... Shading band, 4 ... First transparent resin layer, 4a ... Outer surface of first transparent resin layer, 5 ... Second transparent resin layer, 5a ... Second transparent resin layer Outer surface, 10 ... Light transmission direction control sheet

Claims (3)

A louver layer in which light transmission bands and shading bands are alternately and repeatedly provided, a first transparent resin layer provided on the first surface of the louver layer, and a second surface provided on the second surface of the louver layer. With a transparent resin layer,
The light transmission band, the first transparent resin layer, and the second transparent resin layer are formed of silicone rubber.
Each of the first transparent resin layer and the second transparent resin layer constitutes an outer surface,
The difference between the refractive index of the light transmission band and the refractive index of the first transparent resin layer is less than 0.01 , and the difference between the refractive index of the light transmission band and the refractive index of the second transparent resin layer is less than 0.02. der is,
No other transparent member is provided on the outer surfaces of the first transparent resin layer and the second transparent resin layer.
The thickness of the louver layer is 200 μm to 500 μm, the thickness of the first transparent resin layer is 10 μm to 20 μm, and the thickness of the second transparent resin layer is 10 μm to 20 μm.
Light transmission direction control sheet. The light transmission direction control sheet according to claim 1, wherein the arithmetic mean roughness (Ra) of at least one of the first transparent resin layer and the second transparent resin layer is 0 μm to 3.0 μm. The light transmission direction control sheet according to claim 1 or 2 , wherein the total light transmittance of the light transmission direction control sheet is 80% or more.

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