JPH047954Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a light diffusion film suitable for use in various lighting devices, display devices, etc., and is particularly effective in preventing the occurrence of uneven illumination when illuminating a display surface. The present invention also relates to an improved light diffusing film that can provide a uniformly illuminated display surface.

[Conventional technology]

Generally, various lighting devices, display devices, etc. use light bulbs, LEDs, etc. that are point light sources as light sources, so the illuminance decreases in inverse proportion to the square of the distance.
Therefore, it is difficult to uniformly illuminate a large display surface over the entire surface, so the easiest way to do this is to increase the number of light sources, for example, or to
-Using a diffuser plate as seen in Publication No. 130880,
By diffusing the light from the light source, a uniformly illuminated display surface is obtained.

[The problem that the idea attempts to solve]

However, the former method of increasing the number of light sources not only increases the number of parts but also makes the design of the reflector complicated, which not only causes an increase in cost, but also has the disadvantage of increasing power consumption and heat generation.

On the other hand, with the method of using a diffuser plate in the latter cited publication, conventionally, simply using a plate of uniform thickness would reduce the amount of light transmitted as the distance from the light source increases, resulting in a uniformly illuminated display surface. Therefore, the thickness of the diffuser plate is made thicker closer to the light source in order to equalize the amount of transmission. However, since such a diffuser plate must be manufactured using a mold, there are problems in that the manufacturing cost is high and the space behind the film is narrowed by the thickness of the plate.

The purpose of this invention is to solve the above-mentioned problems and provide a light diffusing film that can provide a uniformly illuminated display surface with a simple configuration of changing the diffusivity of the film surface. .

[Means to solve the problem]

In order to achieve the above objectives, this idea prints a coating film containing light-diffusing particles on a transparent or translucent base film, and also changes the printing state depending on the position of the film surface to adjust the diffusion rate to the light source. The closer the area is to the larger the area, the larger the area is.

[Effect]

In this invention, the diffusion rate of the light diffusion film is increased closer to the light source, so even if the film thickness is thin and constant, the amount of light transmitted increases as the film moves away from the light source.

〔Example〕

This invention will be described in detail below based on embodiments shown in the drawings.

Figure 1 shows the first light diffusing film according to this invention.
FIG. 2 is a sectional view of a display device incorporating the film, FIG. 3 is a front view of the device, and FIG. 4 is a plan view of the device.

In FIG. 1, a light diffusing film 1 includes a band-shaped base film 2 that is transparent or translucent and has a low diffusivity, in other words, a high transmittance. A diffusion coating film 3 containing light diffusing particles is printed and formed on the central portion A shown in FIG. Since the thickness of the diffusion coating film 3 is extremely small, the thickness of the light diffusion film 1 can be considered to be approximately constant.

In Figs. 2 to 4, reference numeral 4 denotes a horizontally long case with an open front surface and a reflective surface 5 on the inner surface;
6 is a light source inserted into the case 4 from the center of the back of the case 4, 7 is a lamp cap that covers the light source 6, 8 is a liquid crystal display that covers the front opening of the case 4, and 9 is a printed circuit board. These constitute a display device 10, and the above-mentioned light diffusion film 1 is adhered to the back surface of the liquid crystal display 8, with the center of the diffusion coating 3 corresponding to and corresponding to the light source 6. .

Thus, in this configuration, when the light emitting surface of the liquid crystal display 8 is illuminated from behind by the light source 6, the light is diffused and transmitted by the light diffusion film 1, but in this case, the light is diffused near the light source 6. The amount of light that passes through the diffuse coating part 3 with a large transmittance (low transmittance) is small, and the diffuse coating part 3 is far from the light source 6.
Both end portions B of the base film 2 that are not coated with
(FIG. 1), the amount of light that diffuses and passes through the light diffusing film 1 is approximately equal over the entire surface, and the illuminated display surface of the liquid crystal display 8 is illuminated over the entire surface. Therefore, it is possible to emit light with substantially uniform brightness. Furthermore, since the base film 2 can be a film with a low diffusivity (high transmittance), there is little loss of light and brighter illumination of the display surface is possible, and there is no need to provide multiple light sources 6. Fewer parts and less power consumption.
Moreover, if the number of light sources is small, the amount of heat generated is also small, and the influence on the liquid crystal display 8 can be suppressed.

Further, since the light diffusing film 1 uses the base film 2 having a constant thickness, the film can be easily manufactured without requiring a mold, and since the thickness is approximately constant, it can be used even in a narrow space.

There are two types of liquid crystal display 8: positive type (type with dark characters and bright surroundings) and negative type (type with bright characters and dark surroundings). This is a problem because they can be distinguished by the color, but with negative type, there is almost no need to worry about this.

FIG. 5 is a front view showing a second embodiment of this invention. In this embodiment, the diffusion coating film 3 is formed by dot printing instead of solid printing, so that the diffusion rate of the light diffusion film 1 is continuously reduced as it moves away from the portion A that is close to the light source. This configuration has the advantage that the amount of transmitted light, in other words, the difference in brightness can be further reduced.

FIG. 6 is a front view showing a third embodiment of this invention, in which a portion of the base film 2 close to the light source,
Three diffusion coatings with different diffusion rates 20, 21, 22
are printed in layers to maximize the diffusion rate of the diffusion coating film 20 and to minimize the area.
The diffusion coefficient of the diffusion coating film 21 is made the smallest and the area is made large, and the diffusion coefficient and area of the diffusion coating film 21 are set to values intermediate between those of the above two diffusion coating films 20 and 22.

Note that the coating film pattern by dots or multiple printing can be made into various patterns as long as the illumination display surface has approximately uniform brightness. For example, a concentric pattern as shown in Fig. Conceivable.

[Effect of idea]

As explained above, the light diffusing film according to this invention is produced by printing a diffusing coating on a transparent or semi-transparent base film with a low diffusivity, and
Since the diffusion rate is made to increase closer to the light source, the amount of light transmitted through the light diffusion film can be made almost equal over the entire surface using a small number of light sources, and the display surface can be illuminated uniformly. enable. In addition, since a film with a low diffusion rate can be used as the base film, there is less light loss and a brighter illumination effect can be obtained, and not only can various patterns be easily produced, but the film itself is also easy to produce and does not require a mold. It has great practical effects, such as being able to be provided at a low price and having a thin and constant film thickness that allows it to be used even in narrow spaces.

[Brief explanation of drawings]

FIG. 1 is a front view showing the first embodiment of this invention;
Fig. 2 is a sectional view of the display device, Fig. 3 is a front view of the device, Fig. 4 is a plan view of the device, Fig. 5 is a front view showing a second embodiment of this invention, and Fig. 6 is a front view of the device. FIG. 7 is a front view showing a third embodiment of this invention, and FIG. 7 is a front view showing a fourth embodiment of this invention. 1... Light diffusion film, 2... Base film, 3... Diffusion coating film, 4... Case, 6... Light source, 8... Liquid crystal display, 20, 21, 22... Diffusion coating film.

Claims (1)

[Scope of utility model registration request] A coating film containing light diffusing particles is printed on a transparent or semi-transparent base film, and the printing condition is varied depending on the position of the film surface, so that the diffusion rate is increased closer to the light source. light diffusing film.