JP3515301B2 - Optical film and display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film and a display device used for electric appliances, office automation equipment, measuring instruments, etc.
More specifically, the present invention relates to an optical film and a display device in which a pattern or a color provided on a display pattern can be visually recognized only when a light source is turned on.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a clear display even in the presence of external illumination or sunlight, and accordingly, the following proposals have been made. ing.

In JP-A-7-84533, as shown in FIG. 1, a transparent layer 12 having a light-scattering property and a light-shielding layer 13 surrounding the transparent layer 12 are formed on the surface of a transparent substrate 11. Further, the light transmitting layer 12, the light shielding layer 13 and the transparent substrate 1
An optical film is disclosed in which a matte layer 14 having translucency is formed on the surface of No. 1. In this optical film, when the light source 17 arranged on the side where the light transmitting layer 12 and the light shielding layer 13 are not formed (the transparent substrate 11 side) is turned on, the light transmitting layer 12 looks bright and the light source 17 is turned on. When not present, the transparent layer 12 is invisible.

In Japanese Patent Laid-Open No. 58-214189, as shown in FIG. 2, a metal thin film 22 is provided on the surface of a transparent substrate 21, and a display pattern 23 is provided between the metal thin film 22 and a light source 27. Has been proposed so that the display pattern 23 is displayed only when the light source 27 is turned on.

[0005]

SUMMARY OF THE INVENTION By the way, Japanese Patent Laid-Open No. 7-
According to the optical film described in Japanese Patent No. 84533, there is no difference between the transmittance of light from the light incident side of the film and the transmittance of light from the display surface side, and therefore external light incident from the display surface is stray light. Therefore, the display pattern may be seen even when the light source is not turned on, or the contrast of the pattern or color displayed at the time of turning on may be reduced due to stray light. In addition, in this optical filter, when a strong matte layer is formed to reduce the light transmittance to reduce stray light, a powerful light source is required to obtain the desired brightness, which makes the device expensive. Or a large amount of energy is required to drive the light source.

On the other hand, according to the optical film described in Japanese Patent Laid-Open No. 58-214189, since the reflection of the metal vapor deposition portion is large, the pattern or color displayed when the light source is turned on becomes difficult to see due to the influence of external light. It may end up.

The present invention has been made in view of the above circumstances, and provides an optical film having a high contrast which is not easily affected by external light and can easily identify a display pattern when the light source is turned on. An object is to provide an inexpensive display device using an optical film.

[0008]

In order to achieve the above object, the optical film of the present invention has the following structure as shown in FIG.
It is composed of a transparent base material 1, a light absorption layer 2 formed on one surface of the transparent base material 1, and a large number of transparent beads 3 ... At the same time, a part of the transparent beads 3 ... Is exposed from the light absorption layer 2, and the colored transparent layer 4 is provided on the surface on the side where the beads 3 ... With such a structure, high contrast display is possible.

That is, as shown in FIG. 4, the transparent beads 3 ... Are closely adhered to the light-incident surface of the optical film of the present invention with a part of the transparent beads 3 exposed from the light-absorbing layer 2. As described above, most of the incident light a from the light source is once converged by the lens action of the transparent beads 3 and then diffused and emitted at the interface with the transparent substrate 1.

On the other hand, of the light incident on this optical film, most of the light a ′ that has not entered the transparent beads 3, that is, the light that is not subjected to the lens action by the transparent beads 3, is mostly due to the light absorption layer 2. It is absorbed and blocks the forward transmission of the optical film. Further, the ambient light b incident from the front side (light emission side) of the optical film is the light absorption layer 2
However, since most of the light is absorbed here, there is less possibility of passing through the transparent beads 3 and becoming stray light.

Therefore, in the optical film of the present invention, the desired light can be effectively derived and the contrast of the displayed pattern or color can be enhanced. The term "transparent" as used in the present invention means that the desired light, that is, the light that should be transmitted through the lens, can be transmitted, and is up to a range including so-called semi-transparency.

Here, in the optical film of the present invention, as shown in FIG. 5, the colored transparent layer 5 formed on the exposed surface of the beads 3 is formed into a desired pattern shape by a screen printing method or the like. It may be processed. Further, a rigid transparent substrate may be bonded to the surface of the transparent base material 1 on the light emitting side via a transparent adhesive.

Further, an antireflection layer for suppressing or controlling the reflection of light may be formed on the surface of the transparent substrate 1 on the light emitting side. As a forming method thereof, there is a method of forming irregularities on the surface of a transparent substrate. For example, transparent resin such as polyester resin, acrylic resin, vinyl resin, etc. is mixed with fine powder such as styrene and acrylic, and rolls. Examples thereof include a method of forming on the surface of the transparent base material by a coating method, a screen printing method or the like. Further, such an antireflection layer may be formed by providing a single layer or multiple layers of a metal oxide thin film of SiO ₂ , TiO ₂ , Al ₂ O ₃ or the like by a vacuum deposition method or the like.

The light absorbing layer used in the optical film of the present invention is preferably made of a resin colored with a black or gray pigment or dye, and the coloring is red,
It may be green, blue or a mixed color thereof.

The transparent beads used in the optical film of the present invention can be composed of, for example, glass beads, plastic beads and the like. The diameter of the transparent beads is not particularly limited, but it is preferably 100 μm or less.

The refractive index of the transparent beads is preferably 1.4 or more. The refractive index is preferably 1.4 or more. When the refractive index is in this range, the incident light is sufficiently condensed and is hardly absorbed by the light absorption layer, and the brightness of the image light can be further increased. This is because. Furthermore, the refractive index of the transparent beads is more preferably 1.55 to 1.95,
More preferably, it is 1.60 to 1.90.

The transparent colored layer used in the optical film of the present invention is a polyester resin colored with a dye or a pigment,
A transparent resin such as an acrylic resin or a vinyl resin can be formed on the transparent beads by a known method, followed by drying. Further, the display pattern can be formed by forming the transparent colored layer in an arbitrary pattern by the screen printing method.

The method for producing the optical film of the present invention is not particularly limited, but for example, a step of forming a light absorbing layer on a transparent substrate and a large number of transparent beads on the light absorbing layer. Dispersing and arranging steps, pressing the dispersed and arranging transparent beads toward the transparent substrate, and softening the light absorbing layer to embed a part of each transparent bead in the light absorbing layer, and lowering the temperature of the light absorbing layer. Can be manufactured through the steps of solidifying the light absorption layer and fixing the transparent beads, and forming the colored transparent layer on the transparent beads.

As shown in FIG. 6, the display device of the present invention has an optical film F having the above-mentioned features and a light source 7 arranged on the side of the optical film F to which the transparent beads 3 are fixed. And a light-shielding housing (for example, made of stainless steel) 6 that houses the optical film F and the light source 7.

[0020]

FIG. 3 is a schematic sectional view showing an example of an embodiment of the optical film of the present invention. The optical film shown in FIG. 3 is composed of a transparent base material 1, a light absorbing layer 2 formed on one surface of the transparent base material 1, and a large number of transparent beads fixed to the light absorbing layer 2. 3 ... 3, a part of each transparent bead 3 ... 3 is exposed from the light absorption layer 2, and the colored transparent layer 4 is provided on the bead exposed surface.
Is characterized by the formation of.

In such an optical film, the light absorption layer 2 is formed (coated) on the transparent substrate 1 to be in a solidified or semi-solidified state, and the transparent beads 3 are formed on the light absorption layer 2.
.... 3 are dispersedly arranged with one layer, that is, with a single particle arrangement,
Then, by using a pressing device or the like, the transparent beads 3 ...
The transparent beads 3 ...
Part of the light-absorbing layer 2 is embedded in the light-absorbing layer 2
Can be prepared by a process of solidifying by natural cooling or forced cooling, and then forming the colored transparent layer 4 of a predetermined pattern on the transparent beads 3.

The embodiment shown in FIG. 3 shows an example in which the colored transparent layer 4 is formed on the entire exposed surface of the transparent beads 3, .. 3, but as shown in FIG. 3 ...
The colored transparent layer 5 formed on the exposed surface of 3 may be processed into a desired pattern shape by a screen printing method or the like.

FIG. 6 is a schematic vertical sectional view showing an example of an embodiment of the display device of the present invention. The display device shown in FIG. 6 is composed of the optical film F shown in FIG. 5, the light source 7, and a housing 6 that houses them.

The housing 6 is a rectangular container made of a light-shielding material such as stainless steel, and has an opening only on the front surface (display surface), and the optical film F is provided in the opening 6A.
However, the light emitting side (transparent substrate 1 side) is arranged so as to face the front side.

The light source 7 is arranged in the back central portion of the housing 6 so as to face the transparent beads 3 of the optical film F.
Only when the light source 7 is turned on, the pattern drawn by the colored transparent layer 5 is displayed.

[0026]

EXAMPLES Specific examples of the optical film and display device of the present invention will be described below. Example 1 The optical film shown in FIG. 3 was produced as follows.

First, a polyester hot melt adhesive (manufactured by Toyobo Co., Ltd., trade name: Byron 30) is formed on one surface of a flat transparent substrate 1 made of polyester resin.
0) To 100 parts by weight, a light absorbing layer 2 containing 3 parts by weight of black carbon was applied by a knife coater so that the thickness after drying would be 10 μm, and then refracted on the light absorbing layer 2. Transparent beads 3 ··· 3 (glass beads are used) having a rate of 1.80 and an average particle diameter of 55 μm are densely arranged, and the temperature is 130 ° C. and the pressure is 4 kg / by hot pressing with a pressing device.
After holding at cm ² for 10 minutes, it was cooled to room temperature to obtain a transparent bead-filled film in which transparent beads 3 were embedded.

Thereafter, a resin prepared by mixing 0.1 part by weight of a red pigment with 100 parts by weight of the transparent polyester resin on the bead-filled film was applied over the entire surface by a knife coater to form a transparent colored layer 4.

When the light transmittance of the optical film thus produced was measured, the total light transmittance was 40% when light was incident from the transparent colored layer 4 side, and the opposite direction (transparent substrate). The total light transmittance was 8% when light was incident from the side). Example 2 A pattern composed of a transparent colored layer in which 0.1 part by weight of a red pigment was mixed with 100 parts by weight of a transparent polyester resin on the transparent bead 3 side of a transparent bead-filled film produced in the same manner as in Example 1. The (colored transparent layer 5) was screen-printed to obtain an optical film F shown in FIG.

Optical film F produced in this way
Is the opening 6 of the stainless steel housing 6 having the structure shown in FIG.
In A, the transparent colored layer 5 was arranged so as to be located inside the housing, and the light source 7 was arranged inside the housing 6 at the position shown in the figure.

When the display device having the above-mentioned structure is taken out outdoors during the day and the influence of external light is examined, the pattern printed on the optical film F, that is, the colored transparent layer 5 is discriminated without turning on the light source 7. It was difficult. Further, when the display device was placed outdoors and the light source 7 was turned on in the daytime, the printed pattern could be clearly confirmed. [Comparative Example 1-1] The optical film shown in FIG. 7 was produced by the following procedure.

First, an antireflection layer 14 is formed by printing an ink containing a matting agent on one surface of a flat transparent substrate 11 made of polyester resin, and a stripe-shaped pattern is formed on the opposite surface. The light shielding layer 13 was formed. Next, the transparent layer 12 was formed on the portion where the light-shielding layer 13 was absent with an ink containing silica powder, and then the antireflection layer 14 was formed on the surfaces of the light-shielding layer 13 and the transparent layer 12.

The total light transmittance of the transparent layer of the optical film thus produced was 40% on both the front and back surfaces. [Comparative Example 2-1] The same pattern 15 as in Example 2 was formed on one surface of the optical film produced in the same manner as in Comparative Example 1-1.
Was screen-printed to obtain an optical film having a structure shown in FIG.

This optical film was attached to the display device shown in FIG. 6 in place of the optical film F according to the above-mentioned Example 2, and the effect of outside light in the daytime outdoors was examined. The printed pattern 15 could be discriminated in a state in which was not lit. Further, when the display device was placed outdoors and the light source 7 was turned on in the daytime, the printed pattern 15 could not be clearly confirmed and the contrast was low. [Comparative Example 1-2] The optical film shown in FIG. 9 was produced by the following procedure.

On one surface of a flat transparent substrate 21 made of polyester resin, a 300 Å metal thin film 21 made of a nickel-chromium alloy was formed. The total light transmittance of this vapor-deposited film was 20% on both the front and back surfaces. [Comparative Example 2-2] The same pattern 25 as in Example 2 was formed on one surface of the optical film produced in the same manner as in Comparative Example 2-1.
Was printed to obtain an optical film having a structure shown in FIG.

This optical film was attached to the display device shown in FIG. 6 in place of the optical film F according to the second embodiment, and the effect of outside light during the daytime outdoors was examined. It was not possible to discriminate the printed pattern 25 in the state where was not lit. When the display device was placed outdoors and the light source 7 was turned on during the day, the display surface was dark and the contrast of the printed pattern 25 was low.

[0037]

As described above, according to the optical film of the present invention, a light absorbing layer is formed on one surface of a transparent substrate, and a large number of transparent beads are fixed to the light absorbing layer. By providing a colored transparent layer on the surface where the transparent beads are exposed from the light absorbing layer, the transmittance of light from the light emitting side of the film is smaller than the transmittance of light from the light incident side of the film. Therefore, the display pattern is less likely to be affected by outside light, the display pattern is not visible when the light source is not lit, and the display pattern can be easily identified when the light source is lit so that the display pattern is high in contrast.

Further, according to the display device of the present invention, since the optical film having the above-mentioned characteristics is used, it is possible to obtain a display having a desired brightness without requiring a strong light source. Cost reduction and energy saving can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a conventional configuration example of an optical film.

FIG. 2 is a schematic cross-sectional view showing another conventional configuration example of an optical film.

FIG. 3 is a schematic sectional view showing an example of an embodiment of an optical film of the present invention.

FIG. 4 is an explanatory view of the action of the optical film of the present invention.

FIG. 5 is a schematic sectional view showing another example of the embodiment of the optical film of the invention.

FIG. 6 is a schematic sectional view showing an example of an embodiment of a display device of the present invention.

FIG. 7 is a schematic cross-sectional view showing Comparative Example 1-1 of the optical film of the invention.

FIG. 8 is a schematic cross-sectional view showing an optical film used in Comparative Example 2-1 of the display device of the present invention.

FIG. 9 is a schematic cross-sectional view showing Comparative Example 1-2 of the optical film of the invention.

FIG. 10 is a schematic sectional view showing an optical film used in Comparative Example 2-2 of the display device of the invention.

[Explanation of symbols]

F Optical filter 1 Transparent base material 2 Light absorption layer 3 ・ 3 Transparent beads 4,5 Colored transparent layer 6 housing 7 light source

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-313891 (JP, A) JP-A-6-308895 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09F 13/12-13/16 G03B 21/62

Claims (4)

(57) [Claims] 1. A transparent base material, a light absorbing layer formed on one surface of the transparent base material, and a large number of transparent beads composed of one layer fixed to the light absorbing layer, and An optical film in which a part of transparent beads is exposed from the light absorbing layer, and a colored transparent layer is provided on the surface on the side where the beads are exposed. 2. The optical film according to claim 1, wherein the colored transparent layer is processed into a predetermined pattern. 3. The optical film according to claim 1, wherein the transparent beads have a refractive index of 1.4 or more. 4. The optical film according to claim 1, 2 or 3, a light source arranged on the side of the optical film to which the transparent beads are fixed, and a light-shielding housing that accommodates the optical film and the light source. Display device.