JP4487808B2 - Lens sheet and manufacturing method thereof - Google Patents

Description

The present invention, in order to carry out electromagnetic shielding measures, according to the lens sheet and a manufacturing method thereof to use as a front plate such as plasma display.

In recent years, peripheral electronic devices malfunction due to electromagnetic waves generated from electronic devices, and influences on the human body can be considered. Therefore, it is necessary to take measures against electromagnetic wave damage to shield electromagnetic waves generated from electronic devices.
In a plasma display such as a plasma TV (television) device, as the screen size increases, countermeasures against electromagnetic waves are urgently required from the viewpoint of preventing malfunction of peripheral electronic devices and preventing influence on the human body. In order to block electromagnetic waves, it is necessary to use a conductive material such as metal to cover the periphery of the electronic device with this conductive material and to ground this conductive material. For example, in a plasma display, electromagnetic wave shielding is performed by applying a transparent conductive resin coat or a transparent conductive film to a cover on the surface of a display screen.

  As another electromagnetic wave shielding measure for plasma display, for example, as shown in Patent Document 1, an ionizing radiation curable resin layer is provided on the flat surface of a lenticular sheet in which a cylindrical lens is arranged in parallel on one side. A proposal has been made to provide an electromagnetic wave shielding function by forming a light-shielding black stripe pattern in a portion cured in a stripe shape by irradiation and containing a conductive filler in the pattern.

Japanese Patent Laid-Open No. 10-282309

However, in the electromagnetic wave shielding measures disclosed in the above-mentioned Patent Document 1, since the black stripe pattern containing the conductive filler is striped, electromagnetic waves may leak from the gap between the stripes, so the shield is not sufficient, There was a problem that the shielding effect was not good.
The present invention has been made in view of the above-described problems and was devised to effectively solve this problem. The object of the present invention is to use a microlens instead of a cylindrical lens and to form a light shielding pattern in two directions, vertical and horizontal. so as to, you have to shield the unnecessary light, to provide a lens sheet and a manufacturing method thereof capable of improving the electromagnetic wave shielding properties.

The invention according to claim 1 is provided corresponding to the plurality of microlenses on the other surface of the film, a film having light permeability, a plurality of microlenses provided on one surface of the film. a plurality of ultraviolet-curing resin portion having light transmittance of frustoconical and, the other of the on the side plurality of ultraviolet curable resin of the film to the side remote from the other surface with truncated portion A lens sheet comprising: a light shielding layer having an electromagnetic wave shielding function provided so as to fill a gap between each other.

The invention according to claim 2 is characterized in that , in the invention of claim 1, the light shielding layer is formed of a mixture of a black paint and a conductive material.

The invention according to claim 3 includes a first step of forming a plurality of microlenses on one surface side of a light-transmitting film and forming an ultraviolet curable resin layer on the other surface side of the film, and the first step. after the irradiated plurality of ultraviolet rays toward the microlens side of the ultraviolet curable resin layer, spaced apart side from the other surface to cure the ultraviolet curable resin layer of the ultraviolet has passed region截A second step of forming a plurality of ultraviolet curable resin portions having a truncated cone shape as a head; a third step of removing the uncured ultraviolet curable resin layer after the second step; after the third step, the other surface of the film, urchin by said plurality of ultraviolet-curing resin portion buried, form a light-shielding layer having an electromagnetic wave shielding function with a mixture of black paint and the conductive material A fourth step of, after the fourth step, to have, a fifth step of exposing the end face of the truncated portion by removing the surface layer portion of the spaced side from the other surface of the film in said light blocking layer This is a method for manufacturing a lens sheet.

According to the present invention , electromagnetic wave shielding characteristics can be improved.

Examples 1 to 3 of the lens sheet and the manufacturing method thereof according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a partially enlarged sectional view showing Example 1 of a lens sheet having a shielding function according to the present invention, FIG. 2 is a process diagram showing a manufacturing method of the lens sheet shown in FIG. 1, and FIGS. It is a partial expanded sectional view which shows Example 2, 3 of the lens sheet which has a shield function based on this.
As shown in FIG. 1, the lens sheet 1 having an electromagnetic wave shielding function has a transparent film 2 made of, for example, a polymer resin film. A plurality of (many) microlenses 4 arranged vertically and horizontally in an array are attached and fixed (or formed integrally with the film base) on one side (right side in the figure, arrow) which is one side of the film 2. This right surface is the light incident surface a (arrow A indicates the light incident direction). The microlens 4 is formed in a substantially hemispherical shape, for example. A light shielding layer 8 having a transparent optical path 6 and an electromagnetic wave shielding function is formed on the other surface of the film 2, that is, on the side opposite to the light incident surface a. This optical path 6 is formed integrally with the film base (film 2). The optical path 6 is provided in a position corresponding to the microlens 4 and has a size (aperture) and a shape that allows the light collected by the microlens 4 to pass therethrough. Specifically, it has a truncated cone shape. Note that b indicates the exit surface of the optical path 6. The portions other than the optical path 6 are filled with the conductive material 8a, so that the light is blocked or cut.

  Specifically, the light shielding layer 8 is made by mixing a conductive material with a black paint so as to have an electromagnetic wave shielding function as described above. This conductive material is made of metal, carbon, or a composite thereof, and an electromagnetic wave shielding effect is exhibited by mixing this with a black paint. The black paint is mixed with a binder resin, and a thermoplastic resin is generally used as the binder resin. For example, acrylic resin, epoxy resin, saturated polyester resin, polyvinyl chloride resin, polyvinyl acetate resin, and phenol. Examples thereof include resins and urethane resins.

  Examples of the metal of the conductive material include aluminum, nickel, copper, and iron that can be formed into various shapes such as powder, flakes, and fibers. The conductive carbon is preferably one having a resistivity of 1 Ωcm or less. The addition amount of the metal of the conductive material and the simple substance or composite of carbon is preferably in the range of 10 to 100% by weight with respect to the binder resin. When the amount added is less than 10%, the electromagnetic shielding effect is small. Conversely, when the amount added is more than 100% by weight, the dispersibility of the material and the fluidity of the coating liquid are deteriorated. Further, the thickness of the light shielding layer 8 is required to be 0.1 μm or more in order to have an electromagnetic wave shielding effect.

For example, a plasma display 10 is installed on the light incident side (right side) of the lens sheet 1, and light (image) is condensed and emitted from the display 10 on the left emission side.
Thus, in the present invention, instead of the cylindrical lens used in the conventional lens sheet, instead of this, the microlens 4 is arranged in parallel on the surface of the transparent film 2, and the light shielding layer 8 is gathered from the microlens 4. Since the optical path 6 is formed only in the portion through which the emitted light passes, the light shielding black pattern is not in a stripe shape in one direction but in a substantially stripe shape in two directions in the vertical and horizontal directions. The characteristics can be improved.

Next, a method for manufacturing the lens sheet 1 will be described with reference to FIG.
First, as shown in FIG. 2A, a microlens 4 is formed on one surface (upper surface) of a transparent film 2 made of a polymer resin film, and an ultraviolet curable resin layer 12 is formed on the other surface (lower surface) with a thickness of 20 μm. Apply by thickness. As the film 2, a 75 μm thick PET film was used. The microlens 4 is substantially hemispherical and has a radius of 50 μm.
Next, as shown in FIG. 2B, ultraviolet rays UV parallel to the film 2 are irradiated from the microlens 4 side to cure the portion of the ultraviolet curable resin layer 12 through which light passes.
Next, as shown in FIG. 2C, the ultraviolet curable resin layer 12 is washed with a solvent such as IPA (iso-propyl alcohol) or acetone, and an uncured portion 12A (FIG. )) Is removed to form a frustoconical optical path 6. The height of the optical path 6 of the light formed at this time is about 15 μm.

Next, as shown in FIG. 2D, the light shielding layer 8 is applied to a thickness of, for example, 20 μm so that the optical path 6 is completely buried on the side where the optical path 6 is formed. The components of the light shielding layer 8 were 22 parts by weight of acrylic resin, 15 parts by weight of conductive carbon black, and 63 parts by weight of solvent (MEK / toluene = 1: 1).
Next, as shown in FIG. 2 (E), the light shielding layer 8 formed on the optical path 6 was removed by polishing and the end face of the optical path 6 was exposed to produce a lens sheet 1 having an electromagnetic wave shielding function. . The ratio (opening ratio) of the area (opening area) where light is emitted at this time was 70%.

<Comparative example>
As a comparative example, a lens sheet was prepared as follows.
A cylindrical lens was formed on one side of the film 2 made of a polymer resin instead of the microlens 4 of FIG. Subsequent steps were performed in the same manner as in FIGS. At this time, the radius of the cylindrical lens is 50 μm. The light shielding layer 8 is polished until the ratio of the light emitting area (opening area) reaches 70%. The aperture ratio was the same as in the example.
The electromagnetic wave shielding characteristics of the lens sheet having the electromagnetic wave shielding function produced as described above were measured by the following method. The shielding effect is expressed by the following formula.
SE = 20 log (Eb / Ea)
SE: Shielding effect (dB)
Eb: incident electric field strength (v / m)
Ea: Conducted electric field strength (v / m)
As a result of the measurement, in the example (embodiment) of the present invention, the electromagnetic wave shielding effect was 70 dB, but in the comparative example, it was 55 dB, and it was confirmed that the electromagnetic wave shielding effect of the lens sheet of the present invention was large.
Also, as an example of a microlens, a microlens having a substantially circular bottom surface is shown, but the same effect can be obtained when the microlens is in close contact and the bottom surface has a substantially elliptical shape, a substantially hexagonal shape, a substantially polygonal shape, etc. The bottom surface is not limited to a microlens having a substantially circular shape.

  As described above in detail, the lens sheet having an electromagnetic wave shielding function of the present invention can obtain a higher electromagnetic wave shielding effect than a conventional lens sheet using a cylindrical lens and having an electromagnetic wave shielding function.

The first embodiment of the present invention shown in FIG. 1 described above is an example in which the light shielding layers 8 and 8a are filled and formed in all thickness directions other than the optical path 6 except for the exit surface 6. FIG. 3 and FIG. In each of the lens sheets 1B and 1C of Examples 2 and 3 of the present invention, the light shielding layers 8b and 8c are provided on the exit surface side surfaces (exposed surfaces) of the lens sheets 1B and 1C, respectively, excluding the exit surface b of the optical path 6. The example which formed is shown. The lens sheet 1B of Example 2 shown in FIG. 3 protrudes from the exit surface b of the optical path 6 to form a light shielding layer 8b. The lens sheet 1 </ b> C of Example 3 shown in FIG. 4 is provided with a light shielding layer 8 c so as to be substantially flush with the exit surface b of the optical path 6.
Even with such a configuration, a high electromagnetic shielding effect substantially equivalent to that of the first embodiment can be obtained.

It is a partial expanded sectional view which shows Example 1 of the lens sheet which has a shield function based on this invention. It is process drawing which shows the manufacturing method of the lens sheet shown in FIG. It is a partial expanded sectional view which shows Example 2 of the lens sheet which has a shield function based on this invention. It is a partial expanded sectional view which shows Example 3 of the lens sheet which has a shield function based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lens sheet, 2 ... Film, 4 ... Micro lens, 6 ... Optical path, 8, 8a, 8b, 8c ... Light shielding layer, 10 ... Plasma display, 12 ... Ultraviolet curable resin layer, 12A ... Uncured part.

Claims (3)

A film having optical transparency;
A plurality of microlenses provided on one surface of the film;
A plurality of ultraviolet curable resin portions having light transmittance in a truncated cone shape provided on the other surface of the film so as to correspond to the plurality of microlenses and having a side separated from the other surface as a truncated head When,
A light shielding layer having an electromagnetic wave shielding function provided so as to fill a gap between the plurality of ultraviolet curable resin portions on the other surface side of the film;
A lens sheet comprising: The lens sheet according to claim 1, wherein the light shielding layer is formed of a mixture of a black paint and a conductive material. A first step of forming a plurality of microlenses on one side of the film having light permeability and forming an ultraviolet curable resin layer on the other side of the film;
After the first step, the irradiated plurality of ultraviolet rays toward the microlens side of the ultraviolet curable resin layer, spaced from the other surface said by curing the ultraviolet curable resin layer of the ultraviolet has passed region A second step of forming a plurality of ultraviolet- curing resin portions having a truncated cone shape having the truncated side as a truncated head;
A third step of removing the uncured UV curable resin layer after the second step;
After the third step, a light shielding layer having an electromagnetic wave shielding function is formed using a mixture of a black paint and a conductive material so that the plurality of ultraviolet curable resin portions are buried on the other surface side of the film. The fourth step;
After the fourth step, a fifth step of removing the surface layer portion of the light shielding layer on the side away from the other surface of the film to expose the end surface of the head portion;
A method for producing a lens sheet, comprising:

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