JPH01271701A - Light diffusing body and screen for which the same body is used - Google Patents

Abstract

PURPOSE:To obtain the light diffusing body having a high light diffusion effect by specifying the content of gas in the light diffusing body of the light diffusing body constituted by holding or adhering fine hollow grains contg. the gas. CONSTITUTION:The fine hollow grains 2-4 contg. the gas are held or adhered to the light diffusing body by a holding material 1 having 1.3-1.8 refractive index of light to air. The incident light entering the light diffusing body from a light source body is expanded in exit angle at every reflection or/and transmission by the boundary faces of the fine hollow grains 2-4. An observer is thereby enabled to view the video magnified in the angle of field. The light diffusing body having the high light diffusing effect is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light diffuser in which light incident from a light source is diffused inside and can be emitted at a wide angle.

[Prior Art] In recent years, large display devices such as electronic bulletin boards, spherical screens, etc., in which a large number of optical fiber end faces are arranged on a display surface to form a large-area display surface, have become popular.

However, in optical fibers, the light emission angle of the strand itself relative to the air (the angle of the light emitted with respect to the optical fiber axis) is no more than 30 to 60 degrees even if various materials are used for the core and sheath. There is a drawback that even if an observer observes at an angle exceeding this, the pixels of the strand itself cannot be visually recognized by the observer. Therefore, for example, when the display surface is made larger, the effect is not fully exhibited and there is a problem that the display is not very impressive.

Conventionally, in order to solve such problems and increase the viewing angle, the end face of the optical fiber is cut at an acute angle with respect to the optical fiber axis, as in the case of the diffuser disclosed in Japanese Patent Application Laid-Open No. 61-86709. A light scattering material with crystal fine particles dispersed in a transparent base material such as plastic, such as the diffuser disclosed in Japanese Utility Model Application Publication No. 61-41203, can be used as an optical fiber. A diffuser that is fixed to the end face of the light emitting part and utilizes the phenomenon that light incident on the light scattering body is reflected and/or transmitted by fine crystal particles, and furthermore, a diffuser disclosed in JP-A-53-130055. It is known that on the surface of a curved screen on which tens of thousands of optical fiber end faces are arranged, a plate-shaped light diffusion layer is bent according to the curved surface of the screen, and is closely covered with the optical fiber end face. .

[Problems to be Solved by the Invention] However, in the diffuser disclosed in Japanese Patent Laid-Open No. 61-86709, the optical fiber end face has an acute angle face, and this face acts as a kind of prism, so that the incident light is 'f'A
There is a problem in that the NR force is also emitted in the opposite direction, which is disadvantageous in terms of brightness.

In addition, the diffuser disclosed in Japanese Utility Model Application Publication No. 61-41203 does not have a sufficient light diffusing effect with ordinary crystalline fine particles alone, and other light diffusing means are needed to obtain a higher light diffusing effect. For example, it was necessary to attach polyhedral beads or apply light-diffusing fine powder to the surface in contact with air.

Furthermore, even in the diffuser disclosed in Japanese Patent Application Laid-Open No. 53-130055, it is difficult to bend the light diffusion layer according to the curved surface of the screen and closely cover the end face of the optical fiber. For this reason, a method of attaching a diffuser to the output end of each optical fiber can be considered, but since the number of diffusers that must be fixed to the end face of each optical fiber is enormous, it is very time-consuming to attach the light diffuser. There was a problem that it took a while.

An object of the present invention is to provide a light diffuser with a high light diffusion effect by solving the above-mentioned conventional problems, and a further object of the present invention is to provide a screen on which the light diffuser can be easily attached. purpose.

[Means for Solving the Problems] The gist of the present invention for solving the above problems is as follows.

In the present invention, the refractive index of light with respect to air is 1.3 to 1.8.
A light diffuser formed by holding or adhering a hollow microfluid containing a gas with a holding agent, and the content of the gas to the light diffuser is 5 to 70% by volume. It is characterized by

Here, the light diffuser of the present invention refers to a plurality of hollow fine particles having a gas such as air or nitrogen sealed inside to reflect and/or transmit the light incident from the light source body. It consists of a body and a holding agent, which is a binder for binding the hollow fine particles, and its properties may be liquid or solid. This light diffuser is used, for example, in a light guide using an optical fiber, a screen including a display, and the like.

As for the hollow fine particles, since the light diffusion effect of the present invention utilizes the difference in the refractive index of light between the air enclosed in the hollow fine particles and the holding agent, any material with the above-mentioned refractive index difference may be used. There are no particular limitations, and for example, spherical fine particles such as hollow glass spheres and plastic spheres with a diameter of several μm to 300 μm called microballoons are preferable. Further, thin pieces of hollow fibers made of acrylic, polyester, etc. may also be used. Among these hollow fine particles, hollow glass spheres are more preferable because of their uniform particle size and low light transmission loss.

On the other hand, the holding agent is preferably one that can hold the above-mentioned hollow fine particles that are appropriately dispersed and that can transmit incident light without attenuation, such as epoxy resin, styrene resin, polycarbonate resin, acrylic acid resin, etc. Ester resins, vinyl acetate resins, ethylene vinyl acetate resins, polyester resins, polyamide resins, silicone resins, and the like are preferred. Among these resins, epoxy resins and acrylic acid ester resins are more preferred from the viewpoint of transparency, adhesiveness to the light source, and the like.

Further, the optical refractive index of the retaining agent with respect to air needs to be within the range of 1.3 to 1.8 in order to exhibit the light diffusion effect of the present invention.

It can be said that it is preferable to mix the hollow fine particles into the retaining agent in a larger amount, as this increases the chances of light diffusion within the retaining agent.
If too much hollow fine particles are mixed in, the strength of the entire light diffuser will decrease, so it is necessary to adjust the amount to 5 to 70% by volume. A more preferable mixing amount within this range is 10 to
It is 50% by volume. In addition, the thicker the coating thickness of the retention agent, the greater the light diffusion effect, but the coating thickness that satisfies these conditions is such that the amount of hollow fine particles mixed into the retention agent is 10 to 5.
In the case of 0% by volume, the thickness is preferably 60 to 500 μm, more preferably 100 to 300 μm.

In addition to the screen in which a plurality of optical fiber end faces are arranged to form an image plane, the image plane may be made of any material and may have a planar or curved shape.

The method for producing a light diffuser of the present invention is obtained by dispersing the above-mentioned hollow fine particles in a holding agent as uniformly as possible, and then drying or leaving it for a certain period of time to solidify. As a method for dispersing the hollow fine particles as uniformly as possible in the holding agent, manual stirring using a propeller type stirrer with a small shearing force or a spatula is sufficient. The light diffuser can be attached to the light source body by coating it with a coating device such as a knife coater or reverse roll coater if the light source body is flat, or by coating it with a coating device such as a knife coater or reverse roll coater, or if the light source body is curved. In some cases, there are methods such as applying a liquid light diffuser prepared in advance with a brush or spraying with an air gun.

The diameter of the hollow fine particles of the present invention is not particularly limited, but as mentioned above, those commonly used have a diameter of 1 μm to 300 μm.
Since it is a fine particle of about 100 m in size and the average viscosity of the holding agent is about several centipoise to several thousand centipoise, there is no problem even if it is handled as a liquid when applied with the above-mentioned coating device.

Furthermore, when the light diffuser of the present invention is not in a liquid form but is formed into a plate shape, film shape, etc., it may be bent and fixed to the light source body. In order to mold the light diffuser into a plate shape, the liquid light diffuser may be dried and molded, or hollow fine particles with a melting point higher than that of the resin may be added to the resin chip for the above-mentioned retainer. It may be mixed in the form, melted and extruded from a die, and then cooled and solidified.

The light diffuser of the present invention may be used for a screen using a large number of optical fibers as described above, but is not particularly limited. It can be widely applied to dispersants to eliminate uneven lighting for shadow removal, reflective sheets with a reflective layer on the back for nighttime reflection, safety clothing for traffic control, etc., and its range of applications is extremely wide.

[Operation] The incident light that enters the light diffuser from the light source passes through the holding agent and reaches the hollow fine particles. Here, when a certain incident light is reflected at the interface between the hollow fine particles and the gas contained in the hollow fine particles, the cutting edge passes through the hollow fine particles and is re-transmitted into the hollow fine particles. It is refracted when it enters the holding agent from the hollow fine particles. At this time, the optical refractive index of the gas included in the hollow fine particles is 1/1 of the optical refractive index of the holding agent.
Since the light is as small as 3 to 1/1.8, the light is emitted in a direction in which the light is diffused in conjunction with the shape of the light diffuser.

In other words, the viewer's viewing angle is expanded.

[Example] Next, an example of the light diffuser of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross-sectional view of a light diffuser 5 according to the present invention in which a plurality of hollow fine particles 2 to 4 are dispersed in a holding agent 1. , parallel ray L1
, L2...L6 are transmitted and/or reflected and are again emitted to the outside air side B.

In the figure, 6 indicates a core 7 made of polymethyl methacrylate (core diameter 486 μm) and a core 7 made of fluorine-based polymer (
It is an optical fiber consisting of a sheath 8 with a sheath outer diameter of 500 μm), and although only one fiber is shown in the figure, in reality, a plurality of fibers are arranged. These optical fibers have an outer diameter of 400 m.
m, 1.5 to 2.5 m on a spherical screen 9 with a thickness of 3 mm
The end faces of the spherical screen are bonded at intervals of m in a state that they are aligned with the outer peripheral surface of the spherical screen.

The hollow microparticles 2 are commercially available glass spheres (“Hollow Glass Bubbles Scotchlite”, manufactured by 3M) with an average particle diameter of 60 μm (wall thickness: 2 to 3 μm) in which nitrogen-based scum 10 is enclosed. This is a water-based acrylic latex (Paaska ACE #20) which is the retention agent 1.
00'', Kansai Pane 1 (manufactured by Co., Ltd.), thoroughly stirred and dispersed, and then applied to the outer peripheral surface of the spherical screen 9 and air-dried.The thickness of the obtained light diffuser 5 after air-drying was When measured, it was 150 μm.

Here, a halogen lamp was irradiated from the other end 11 of the optical fiber 6, and the brightness in a direction of 180 degrees with respect to the optical fiber axis from the position on the outside air side B of the output end face of the optical fiber 6 was measured using a brightness meter.

The results are shown in the examples in the table.

[Comparative Example] Next, FIG. 2 shows the light diffuser 5- when a solid glass bulb 2- is used instead of the glass bulb 2 in which nitrogen 10 is sealed as shown in the above embodiment. Showing a cross-sectional view, glass bulb 2-
Of the light incident from the light source side A, parallel rays L1-1L
2"'..."6- is transmitted and emitted to the outside air side B.

In the figure, the hollow fine particles 2' have a particle diameter of 40 to 70μ.
Solid spherical glass beads distributed in the range of m ('Blasting Beads', manufactured by Toshiba Baroti 12 Corporation)
, and the number is the light diffuser 5 under the same conditions as in the above example.
′ was obtained.

Then, the brightness at the output end face of the optical fiber 6- was measured in the same manner as in the example.

The results are shown in the comparative example in the table below.

In this table, the viewing angle refers to the angle with respect to the optical fiber axis when a certain luminance becomes 1/10 of the peak intensity in the luminance distribution at the end face of the optical fiber.

From the above results, it can be seen that the light diffuser 5 of the present invention has a wide light emission angle of 154 degrees, which is approximately 2.4 times wider than the viewing angle of 64 degrees for solid spherical glass beads. .

Therefore, when the light diffuser of the present invention is applied in a liquid form to an image surface such as a spherical screen on which a huge number of optical fibers are arranged, even if the image surface is a curved surface or has some unevenness. Since it can be applied in a short time even if there is a problem, it has the excellent effect of making it easier to attach the light diffuser.

[Effects of the Invention] In the light diffuser of the present invention, the hollow fine particles containing gas have a gas content of 5 to 70% due to the retention agent having a refractive index of light relative to air of 1.3 to 1°8. Since the hollow particles are held or bonded at a certain volume %, the incident light that enters the light diffuser of the present invention from the light source is expanded in its emission angle each time it is reflected and/or transmitted at the boundary surface of the hollow particles. Therefore, an excellent effect is achieved in that the viewer can view an image with an enlarged viewing angle. Therefore, when this diffuser is used, for example, on the image surface of a spherical screen where the end faces of optical fibers are arranged, the entire screen surface is extremely bright, instead of the periphery of the spherical screen being dimly lit as in the case of conventional spherical screens. You can get a powerful image.

Furthermore, when the light diffuser of the present invention is made into a liquid and applied to an image surface such as a spherical screen on which a huge number of optical fibers are arranged, even if the applied surface is a curved surface, there may be some unevenness. Since it can be applied in a short time even if the light diffuser is applied, a screen can be obtained that allows easy attachment of the light diffuser.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the light diffuser of the present invention;
FIG. 2 is a sectional view showing a comparative example of a light diffuser. 1: Retention agent 2-4: Hollow fine particles 2-: Solid glass beads 5.5-: Light diffuser 6.6-: Optical fiber 7.7-: Core 8.8-: Sheath 9: Spherical screen 10 : Encapsulated gas (nitrogen)

Claims (2)

[Claims] (1) A light diffuser in which a hollow microfluid containing gas is held or bonded with a holding agent having a refractive index of light with respect to air of 1.3 to 1.8, the light diffuser having a refractive index of 1.3 to 1.8. A light diffuser characterized in that the gas content is 5 to 70% by volume. (2) A screen in which a plurality of optical fiber end faces are arranged, the light diffuser according to claim 1 being coated on the screen surface.