JPS5851242B2 - Light scattering tape or sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides light emitted from point light sources mainly using light emitting diodes, such as table clocks, taxi meters, and numerical displays on various instrument panels of automobiles and airplanes.
The present invention relates to a light scattering tape or sheet that is used when performing desired display by diffusing and scattering light and converting it into planar light.

Conventionally, as this type of display board, there has been a film that diffuses and scatters the point light source of a light emitting diode into a planar light.
This one simply covers one side of the plastic film.
For example, the surface is simply roughened by rubbing inorganic powder, etc. Therefore, when constructing an actual display device, as shown in Figure 1, the light emitting diode chip 0
3 is attached to the surface of the light reflecting plate 05 fixed to the substrate 04,
The light emitted from the chip 03 is overlaid with a rough-surfaced light scattering film 06 that is colored red, green, or yellow to match the spectrum of the light emitting diode, or is combined with a separate colored film. The light is diffused and reflected by the inverted conical light reflecting surface 05A formed on the light reflecting plate 05, and is scattered in a planar manner through the film 06, so that a desired display can be displayed on the front surface of the film.

However, the disadvantage of this conventional product is that it is a part of the display device, so when integrating the entire display device into a finished product, this film and, in some cases, the protective film as well, for example, as shown in Figure 1. It is necessary to use a fastener as shown in 07 to fasten the product, and therefore, the work efficiency in commercializing the product is extremely low, and a decrease in productivity and deterioration in quality are unavoidable.

In addition, in order to eliminate such defects, as shown in FIG. It has come to be possible to consider a device that is integrated with adhesive.

Although this product does not require the use of the above-mentioned fasteners and can improve productivity by increasing work efficiency in manufacturing, the back surface of the film 06 is roughened to prevent scattering. However, the adhesive layer 08 makes the surface smooth, resulting in insufficient light scattering effect.

However, if a separate sheet-like member for a scattering layer is interposed in the middle part of the thickness of the film or the contact surface with the adhesive layer, the light transmittance will be drastically reduced and the desired display effect will not be achieved. There is a drawback that you will not be able to do it.

In view of the above-mentioned circumstances, the present inventors have conducted extensive research and have completed a light-scattering tape or sheet that can eliminate the various drawbacks mentioned above.

The light-scattering tape or sheet according to the present invention includes adhesive microparticles having a median diameter of 5 to 100 microns on at least one side of a light-transmitting base material, which are bonded and integrated with each other.
Alternatively, it is characterized in that it is bonded and integrated via another adhesive layer or a non-adhesive layer, and is coated uniformly or almost uniformly with its surface roughened.

That is, since the tape or sheet of the present invention has an adhesive layer made of adhesive microparticles on at least one side, there is no need to use any fasteners as described above when manufacturing an integrated display device. , it is possible to increase manufacturing efficiency, thereby improving productivity and reducing costs, and because the surface of the microparticles themselves forming the adhesive layer is roughened, the adhesive layer can be used as a layer for light scattering. A flat part where the light scattering effect is hardly reduced due to the presence of the layer, and the phenomenon of straight light propagation is caused by the coalescence of microparticles or the integration through other adhesive layers, etc. The desired light scattering effect can be maintained for many years by reliably suppressing the occurrence of .

In addition, there is no need for a separate scattering layer, or even if one is provided, it can be very thin, so the light transmittance can be greatly improved compared to conventional adhesive types. As a whole, we have obtained a display device that has a high display effect and has high practical value as a display device for light emitting diodes.

The gist of the light-scattering tape or sheet of the present invention is that the light-scattering tape or sheet has 5
~100 microns (hereinafter referred to as μ).

) The acrylic adhesive microparticles 2 having a median diameter of 5 per square meter when combined and integrated
~150 grams (hereinafter referred to as g/rrl).

) to form a rough surface such as a corrugated structure as shown in FIG. Things that should be done and their simple reasons,
Furthermore, improved versions will be enumerated and explained.

The acrylic adhesive fine particles used in the present invention can be obtained by suspension polymerization of an acrylic monomer or the like together with a functional monomer.

In this case, the median diameter of the adhesive microparticles is preferably from 5 to 100 microns, and if possible, it is preferable that the particle diameter is even more uniform.

When the particle size is 5 μm or less, the scattering effect is slightly reduced.

On the other hand, if it exceeds 100μ, the microparticles become visible and the display looks bad and is not suitable.The reason why acrylic adhesive microparticles should not be isolated and separated from each other is if they become isolated and separated from each other. , flat areas occur or tend to occur between the microparticles, and light does not scatter in these areas and travels straight.

Therefore, in order for the light to scatter sufficiently without going straight, the microparticles must strongly coalesce together, or other adhesive layers,
Alternatively, it is necessary to integrate them via a non-adhesive layer so that the adhesive surface layer has a corrugated structure.

An ideal structure is as shown in FIG.

In order for the microparticles to form the above-mentioned structure in which they are integrated with each other, it is not preferable for the microparticles to be strongly cross-linked internally, but rather to be partially dissolved in the good solvent of the acrylic adhesive. The one is good.

Therefore, it is better not to add a large amount of crosslinking agent during polymerization of the adhesive.

It is also preferable to use it in combination with an ordinary solution-based acrylic adhesive; in this case, crosslinking with a polyfunctional isocyanate, polyetherified melamine, etc. increases the cohesive strength of the adhesive tape.

It is common knowledge for those involved in the technology to treat the back side of the tape base material in order to make it into a tape shape, or to create a release film 9 as shown in Figure 4, but when it is made into a tape shape, it is common knowledge that micro particles Although the group may be deformed into a planar structure, it is desirable that the original waveform structure be restored when the release film 9 is peeled off.

The base material in the present invention is not particularly limited, and any material may be used as long as it has excellent light transmittance.The use of a colored film that matches the wavelength characteristics of the light emitting diode used further enhances the gist of the present invention. I will make use of it.

Although the light scattering effect of the adhesive microparticle group in the present invention is extremely excellent, it is also good to add a tape base material with a roughened surface or a light scattering layer to further increase the effect. Of course.

The present invention will be described in detail below using Examples and corresponding Comparative Examples.

Example 1 Adhesive microparticles are prepared with the following composition.

Ion-exchanged water 200 parts by weight Butyl acrylate 90 parts by weight 2-ethylhexyl acrylate 6 parts by weight 2-acrylamide, sodium salt of -2-methylpropanesulfonic acid 4.5 parts by weight Benzoyl peroxide 0.25 parts by weight Anionic interface Activator 4 parts by weight (30% solids solution) The above components are polymerized in a nitrogen stream, and the suspension precipitate with a median diameter of 35 μm is dispersed in toluene to prepare a sticky stock solution.

Next, a commercially available 125 μm thick polyester film is coated with a resin containing a red dye to produce a red film.

In this case, the coating layer is 20μ and the light transmittance is 59
0mm→0%, 650mm→70%, and 700→75%.

The above-mentioned adhesive stock solution was applied to this red film to obtain a tape-like product.

The coating amount was 35 g/m'', and when observed using a 50x magnification looper, it was found that the sticky microparticles were integrated with each other.
It had a wavy structure without a flat surface.

Therefore, in order to examine the degree of scattering, the degree of light scattering (cloudiness)
As a result of measuring with an integrating sphere photoelectric photometer, it was 91%.
It was confirmed that the light scattering property (cloudiness) was extremely excellent.

Next, as shown in Figure 5, this adhesive tape is attached to a light-emitting diode display device for meters to create a figure-eight display, and the dot display is made into a surface display using light-scattering tape. .

Point light was emitted by connecting a 400μ square red light emitting diode 3 to a DC 3■, and the degree of light scattering was observed. As a result, the light was sufficiently scattered over the entire area and no point light source was visible, indicating that it was a good light scattering tape. It was confirmed that the decrease in red light transmittance due to applying the adhesive microparticle group was 3.7%,
There was almost no loss of light energy.

Next, as a comparative example, Example 1. The results are shown in which a normal solution-based adhesive was used instead of the adhesive microparticle group.

Comparative Example 1 Ethyl acetate 200 parts by weight Butyl acrylate 90 parts by weight 2-ethylhexyl acrylate 6 parts by weight Acrylic acid
4 parts by weight Benzoyl peroxide 0
．． 25 parts by weight of these components are polymerized in a nitrogen stream.

Next, Example 1. This adhesive is applied to the red film used in 1 at a solid content of 359/tri' to produce a tape-like product.

The light scattering degree (haze) of this tape is 7.7%, 92.3
% passed through as parallel rays.

The decrease in red light transmittance due to the application of the adhesive was 4.0%, and there was almost no loss of light energy.

Furthermore, when a printing test was carried out by adhering this tape to a light emitting diode display device, a point light source was clearly visible and the display was extremely unclear and could not be used at all.

Example 2 A commercially available 75μ red light scattering film developed for light scattering was coated with Example 1. A similar experiment was conducted.

Although the film is thin, the light transmittance of the original film is the same as that of Example 1. It was only 54.7% of the total.

Next, we conducted an issue display test and found that the display was clear and no point light source was visible.

The decrease in light transmittance due to the application of the adhesive was undetectable within the margin of error.

(2% or less) Comparative Example 2 In place of the adhesive microparticles used in Example 2, Comparative Example 1. It was made into a tape by applying the adhesive used in .

As a result of a light emitting display test, the display was clear, but a point light source was visible, and the appearance was unfavorable.

Example 3 The red film used in Example 1 was mixed with the adhesive microparticles used in Example 1 and the adhesive used in Comparative Example 1 at a solid content ratio of 2:1, and 35 g/
It was applied to the entire surface to a thickness of m.

As a result of observation using a 50x magnification looper, it was found to have a wavy structure without a flat surface.

The light scattering degree of this tape is 90.0%, and in a display test after it was attached to a diode display device, light was sufficiently scattered throughout the entire area, and no point light source was visible, indicating that it is a good light scattering tape. confirmed.

The decrease in light transmittance due to the application of the adhesive was such that it could not be detected within the error range of the meter.

(2% or less) Example 4 Example 1 was applied to one side (smooth side) of a commercially available 125μ roughened polyester film. The same red dye coding was carried out.

The coating thickness was 20μ, and the total light transmittance was 97.0% of that without surface roughening, and almost no decrease in light transmittance due to surface roughening was observed.

Next, Example 1 was applied to the rough surface of this red surface roughened film. 3,597 m of the adhesive microparticles used in the above were applied, formed into a tape, and then bonded to a light emitting diode display device.

Light-emitting diode display test results show that the light is well scattered and
A clear display was seen and no point light sources were seen.

Comparative Example 3 In Example 4, Comparative Example 1. The solid content of the solution-based adhesive used in 35g/rt? After applying it and making it into a tape, it was attached to a light emitting diode display device and a light emitting diode display test was conducted.

As a result, the light scattering effect due to the surface roughening completely disappeared, and a point light source appeared, making it completely unsuitable for use as a display board.

Comparative Example 4 The red film used in Example 1 was coated with the adhesive microparticles used in Example 1 to a thickness of 4.597 d.

As a result of observation using a 50x magnification looper, the microparticles did not coalesce and integrate, and a considerable amount of flat portions were visible, indicating that there was no wavy structure.

The degree of light scattering of this tape was 43.0%, and as a result of a light emitting diode display test, a point light source was clearly visible and it was unsuitable as a light scattering tape.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the light-scattering tape or sheet according to the present invention, and FIGS. 1 and 2 are structural views of the conventional display device, respectively, and FIG. 3 shows the light-scattering tape or sheet according to the present invention. FIG. 4 is an enlarged cross-sectional view of a tape-shaped product, and FIG. 5 is a cross-sectional view of a display device using the tape or sheet of the present invention. 1... Translucent base material, 2... Adhesive microparticles.

Claims (1)

[Scope of Claims] 1. Adhesive microparticles 2 having a median diameter of 5 to 100 microns are bonded together on at least one side of a transparent substrate 1, or other adhesive is used. 1. A light-scattering tape or sheet, characterized in that it is bonded and integrated through a layer or a non-adhesive layer, and is coated uniformly or almost uniformly so that its surface is roughened. 2. The light scattering tape or sheet according to claim 1, wherein the coating amount of the adhesive microparticles 2 is 5 to 150 grams per square meter. 3. The light scattering tape or sheet according to claim 1, wherein the base material 1 is a flexible plastic film.