JPS60184559A - Light-diffusing plastic - Google Patents

Abstract

PURPOSE:To provide the titled plastic through which light source can not be seen and which can be used for brighter lighting fixture, by dispersing transparent fine particles having a specified particle size and refractive index in a transparent plastic having a specified refractive index at a specified concn. CONSTITUTION:A light-diffusing plastic is obtd. by dispersing transparent fine particles (e.g. silica, glass, LiF or CaCO3) which have a refractive index Np satisfying the formula I and an average particle size dmu satisfying the formula IIand contain not more than 5wt% particles having a particle size of 5mu or below, in a transparent plastic having a refractive index Ns [e.g. (meth)acrylic resin, styrene resin, polycarbonate resin or PVC] in such a concentration as to give the max. bending angle (beta value) of 4-10 deg.. Though the plastic is lowly light-diffusible, light source can not be seen therethrough and the plastic is suitable for use as a light-diffusing member for brighter lighting fixture, display or transparent screen, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a light-diffusing plastic suitable for use in lighting covers, lighting signboards, glazing, various displays, or transmission screens for all purposes of diffusing spring light.

(Prior art) In recent years, due to the social demand for energy conservation, attention has been paid to how to effectively utilize energy in lighting equipment, detection displays, etc. Since the energy emitted from the light source is constant, the energy consumption is reduced as much as possible. It is possible to diffuse light in a specific direction without absorbing it, that is, to perform directional diffusion.
This is one of the desirable properties of light-diffusing materials. - From this point of view, when a diffusive material with directional properties is incorporated into a device such as a lighting cover'1fcr;c display, a shape suitable for the material is required. This shape may be a sphere surrounding the light source, or a flat plate with fine irregularities on its surface, or a regular shape such as a lenticular lens. Therefore, it is also desirable that the material be a material that can be easily given these shapes.

Conventionally, diffusive materials for lighting covers, display screens and the like have generally been obtained by dispersing inorganic transparent fine particles in completely transparent plastic. In this case, the transparent plastic used is (styrene resin is used for the metacoacrylic resin 1, and in order to obtain diffusivity, a material with a refractive index different from that of the transparent plastic of the base material, such as barium sulfate, calcium chloride, quartz, etc.) is used. Inorganic transparent fine particles with an average particle size of 1 μm or less, etc., are completely mixed in or coated.
Special Publication No. 46-43189 and Utility Model Publication No. 29-74
See Publication No. 40. ) The light-diffusing glass that has been put into practical use for some time now has very good diffusivity, with a maximum bending angle (β value) of 60° or more. The maximum curve angle (β value) is the maximum brightness (gain) on the original axis when the sample is viewed from the total transmission of parallel rays incident perpendicularly to the sample surface.
iG.

In this case, the angle with the original axis required for the luminance (gain) to decrease by 173 Goi is used and is generally used.

The present inventors investigated various light diffusing materials that can provide directivity and found the following fact. In other words, as long as the zero-source source etc. cannot be seen through, the maximum bending angle (β value)
If t- is made smaller, directivity can be easily imparted and the maximum brightness (gain) can be increased. (2) Conventional light diffusing materials generally have a maximum bending angle (β value) of 20 degrees or more.

However, if the concentration of the light diffusing agent is lowered (that is, the total diffusivity is lowered) and the maximum bending angle (β value) is less than 10', the light source becomes transparent and it cannot be used as a light diffusing material.

The graph in Figure 1 explains this point.
This is methacrylic resin (N5=
1.492) Amorphous silica (Np = 1.46), commercially available as transparent fine particles, was used (this particle size distribution was
) and crystalline silica (Np=1.5
4) (this particle size distribution is shown in Figure 3 (■)). In this graph, the dotted line is the area that can be seen through a fluorescent lamp (30W) when held up at a distance of 5 m. In this way, it can be seen that when the concentration of β value is lower than 106, the diffusion agent becomes transparent when the concentration of β value is lower than 106, as shown in (■) and (■), in case of a diffusing agent that contains more than the total weight of particles with a particle size of 5μ or less. Ru.

Considering commonly used lighting covers, this type of lighting cover is often obtained as a molded product in the shape of a dish, a box, or a sphere by heat-molding a plate-shaped Tsum diffusive plastic. By the way, when such heat forming is performed, the plate-shaped plastic is partially or completely stretched. The extent of this stretching is approximately 174 to 175 at a large change in sheet thickness, but it is required to maintain light diffusivity to such an extent that the light source cannot be seen through even after stretching.

In other words, even after this degree of stretching, the maximum bend is at the corner (
It is necessary to add a sufficient amount of light diffusing agent to the plastic plate from the beginning so that the β value does not exceed 10 degrees.

For this reason, this type of light-diffusing plastic material has traditionally had the disadvantage of high light-diffusing properties and low total light transmittance. Improvements are desired not only in diffusible plastics but also in the various technical fields mentioned above. For this reason, the present inventors first introduced transparent @particles with a relatively large average particle size into a transparent plastic with a maximum bending angle (β value) of 20.
C% Gansho 58-2, which proposed a light-diffusing glasstic characterized by being dispersed at a concentration of ~10°
No. 45788 found that even particles with a relatively small diameter can be put to practical use under smooth conditions.

(Objective of the Invention) That is, the present invention aims to provide all N-RC original diffusive plastics with excellent light diffusion properties that do not allow the light source to be seen through even if the maximum bending angle (β value) is 10° or less. There's something to do.

(Structure of the Invention) The present invention has been made to achieve the above-mentioned object, and its gist is that a transparent plastic having a refractive index of N8 is provided with the following formula (I).

(n) Q, 02≦l NB −Np l≦[Ll ・・・・・・(
1) 4μ≦dμ≦10μ Average particle diameter d that satisfies (II)! 1, refractive index Np and grain size 3
A light-diffusing plastic characterized by dispersing transparent fine particles containing at most 5% by weight of particles smaller than μ at a concentration such that the maximum bending angle (β value) is 4° to 10°. be.

Below, Kion Hane will be explained in more detail.

Transparent plastics of the present invention include (meth)acrylic resin, polystyrene resin, polycarbonate resin, vinyl chloride resin, etc., but are not limited to these.

17'c Transparent fine particles in the present invention include crystalline silica, amorphous silica, glass, concentrated lithium, calcium fluoride, calcium carbonate, barium sulfate, aluminum hydroxide, inorganic substances such as muscovite, and methyl methacrylate. and organic substances such as polymers of various (meth)acrylate derivatives that can be copolymerized with these, but are of course not limited to these.

It is common knowledge that fine particles with a refractive index different from that of the base material are dispersed in order to provide total dispersion properties. ,
It is known that the amount of permeation and diffusion is large. However, if it is too small, even 19, due to the difference in refractive index, the number of collisions of incident light with the diffusing agent will be reduced, so the concentration of the diffusing agent will have to be the same. This is unfavorable from the viewpoint of mechanical properties of the light diffusing material. Therefore, in the present invention, the difference in refractive index between the transparent plastic base material and the transparent fine particles is set to α02 to α1. - Next, the relationship between the refractive index and the average grain size will be explained. The relationship between the refractive index and particle size that gives the maximum hiding power is well-known in many research ministries as F, experimental formulas, and calculation formulas. Among these, the Mitton equation is a typical one. This formula is based on the refractive index 'zNs of the base material and fine particles, N
Let p be the average particle diameter d(
μ) is 15) Np winding, which is expressed by the following formula.

If the transparent plastic base material is a methacrylic resin with a refractive index of 1.492, and λ=LL55μ,
The relationship between the refractive index of transparent fine particles and the average particle diameter that provides the maximum hiding power is as follows.

+ at Np=1.592 (lNp-N5l=0.1)
1=1.9μ, Np=1.512 (1Np−Nsl=[
LO2), d=9-3μ, and as can be seen from this result, with conventional light diffusing materials, the average particle scratching sound of transparent fine particles is 1
It is common knowledge to keep it below 0μ. (Refer to the above-mentioned Japanese Patent Application Laid-open No. 54-15524.) By the way, in order to obtain diffusivity with a maximum bending angle (β value) of 4° to 10°, the refractive index and average particle size of the transparent fine particles conventionally used are However, as a result of further careful study by the present inventors, we found that the following formulas (1) and (II ) [L0
2≦IPIs-Npl≦L11...-(1)4μ≦
dμ≦10μ ・・・・・・・・・・・・・・・One appropriate amount of transparent fine particles having an average particle diameter dμ and a refractive index Np′ that satisfy (If) and containing at most 5% by weight of particles with a particle size of 3μ or less. By dispersing the material, the maximum bending angle (β value) can be increased to 10°.
They discovered that the light source cannot be seen through even below. It should be noted that if the average particle diameter dμ of the transparent fine particles exceeds 10μ, it is undesirable because it tends to cause glare in the diffused light.

Incidentally, transparent fine particles having a particle size distribution in which at most 5 parts by weight of particles with a particle size of 3 μm or less are mixed can be obtained by air selection or sedimentation velocity sieving in water.

(Examples) The present invention will be described in detail below using Examples and Comparative Examples, but the present invention is not limited to these Examples. For example, as the light-diffusing plastic of the present invention, the Fresnel lens and /'E7C can of course be used in a lenticular lens or any other lens shape, or in the form of a spherical two-plate shape, etc. . The maximum brightness (gain) Go and maximum bending angle (β value) in this example were determined as follows.

That is, with the arrangement shown in Figure 2, the light source (1) (collimator, manufactured by Nippon Kogaku Co., Ltd.) is oriented perpendicularly to the entire sample (2) surface, and the illuminance on the sample (2) surface is 10.
Adjust the brightness so that it becomes ft-cd. Also, the light source (
1) and sample (2), sample (2) to 1
A luminance meter (3) (manufactured by Minolta, Auto Spot) was installed facing all samples at a distance of m. At this time, the brightness sound on the surface of sample (2) was measured, f t-L/f t-
The value in cd was set as Go. Furthermore, this luminance meter (3)
It rotates around the center of all samples (2), and the brightness on sample (2) becomes 1/! The maximum bending angle that results in IGO (
β0) All measurements were taken. The 1fc average particle diameter was obtained by creating a cumulative weight histogram of particle diameters from a Coulter Counter (manufactured by Coulter Counter Co., Ltd., TA-[type]), and taking the particle diameter corresponding to 50% of the weight as the average particle diameter.

Examples 1 to 4 Partial polymer of methyl methacrylate (polymerization rate 20%) 1
00 parts (by weight, same hereinafter) contains crystalline silica with an average particle size of 7 μm (refractive index 1.54), amorphous silica with an average particle size of 7 μm (refractive index, 1.46), and a particle size distribution of n et al. The ingredients shown in Figure 3 (■ and ■) were blended in the proportion of the first batter and sufficiently dispersed. Add [101
part of dioctyl sulfosuccinate sodium salt (as a dispersant, mold release agent) and 2.2'-azobis÷2.4
-Dimethylvaleronitrile) (as a polymerization catalyst) was added and dissolved, then degassed and poured into an inorganic glass mold whose thickness was set in advance to be 3+a+. The sheet was immersed in warm water for 180 minutes, and then kept at a temperature of 110°C for 120 minutes to pre-cure the polymerization.After taking the sheet out of the mold, the sheet was held over a 30W fluorescent lamp to check the condition of the light source. When I looked, Izu's eaves weren't transparent either.Go again.

The values of β are shown in Table 1. The optical characteristics of the four samples in this example are shown by curves ■ and ■ in Figure 1.
It can be seen that the light source cannot be seen through the maximum curve even if the angle (°β value) is less than 10°.

In addition, these samples were heated and burned, and the weight per unit area of silica from the ash was calculated, which is shown in Table 1. (The following examples and comparative examples were also prepared in the same manner.) Example 5 Methacrylic resin (Mitsubishi Rayon: Acrybella MD) 1
The particle size distribution with an average particle diameter of 7μ for 00 parts is shown in Figure 3 by the curve [F
] Anatomical silica (refractive index 1.46) gold, 1.
The mixture was mixed in a proportion of 6 parts, uniformly dispersed in a tumbler, and extruded according to a conventional method to produce a sheet with a thickness of 3 sheets.

When this sample was exposed to a light source, it was not visible to a fluorescent lamp. Other evaluation results are shown in the first garment.

Example 6 Crystalline silica with an average particle size of 8 μ and whose particle size distribution is shown by curve G in Figure 3 was used in place of the amorphous silica of Example 5 (
A sheet was prepared in the same manner as in Example 5 (however, 6 parts of A were used). The particle size distribution of the crystalline silica at this time was such that 1.5 parts by weight were 5 microns or less. This sungle was not visible in either the fluorescent lamp or the 100W incandescent lamp. Other evaluation results are shown in Table 1.

Example 7 Polycarbonate resin (manufactured by Mitsubishi Kasei Co., Ltd., Tubarex 7
030. Refractive index 1.59) For I D 0 part,
The same crystalline silica used in Example 6 (refractive index 1.54)
) was blended in 9 parts and uniformly dispersed in a tumbler.

This was made into a pellet by melting it into an extruder, and was then put into the whole pellet injection molding machine to produce a sheet having a thickness of 3rmn. In addition, the particle size distribution of the crystalline silica at this time was 1.5% by weight of 3μ or less. Evaluation results first
Shown in the table.

Example 8 Polystyrene resin (manufactured by Dainippon Ink & Chemicals Co., Ltd., CR3
500, refractive index 1.59) 1.1 parts of crystalline silica (refractive index 1.54) having an average particle size of 6 μm was blended with 100 parts and uniformly dispersed in a tumbler. This material was made into a pellet using an extruder, and then a complete sheet with a thickness of 3 m+ was produced using the entire pellet injection molding machine. All evaluation results are shown in Table 1. Note that the particle size distribution of the crystalline silica used was 4% by weight of 6μ or less.

Example 9 Partial polymer of methyl methacrylate (polymerization rate 20%) 1
Calcium carbonate with an average particle size of 6μ (refractive index 1.5) is added to 00 parts.
8) In the same manner as in Example 1, 8 parts of 'iα were added to obtain a sheet laminated sheet with a thickness of 5 mm using the conventional method of cast polymerization. Show the evaluation results in the first hole. The particle size distribution of the calcium carbonate used was 4% by weight of 3p or less.

Example 10 Partial polymer of methyl methacrylate (polymerization rate 20%) 1
00 parts of aluminum hydroxide with an average particle size of 8 μm (refractive index of 1
．． 57) 1.2 parts of 'li- was blended.

This was subjected to the conventional casting polymerization method in the same manner as in Example 1 to obtain a sheet 2 having a thickness of 3II11. The evaluation results are shown in Table 1. In addition, the particle size distribution of the aluminum hydroxide used was 5μ.
The following was found at 2% by weight.

From the results of the above examples, it has been found that in the examples constituting the present invention, it is possible to obtain a bright diffusive resin composition that is difficult to see through even when the maximum bending angle, which is the area where the transparent housing is formed, is 10 degrees or less. Recognize.

Comparative Examples 1 to 3 Methacrylic resin (Mitsubishi Rayon: Acrivera MD, refractive index 1.49) Anatomical silica with an average particle size of 6 μ per 100 parts (l refractive index 1.46 > (The particle size distribution of this is 6th (indicated by ■ in the figure) in the proportions shown in Table 1, uniformly dispersed in a tumbler, extruded according to a conventional method, and made into a sheet with a thickness of 5 rra. Comparison For Example 1゜2, use the sheet as a light source (30W fluorescent lamp)
), it was not transparent even when viewed by holding it up, but in Comparative Example 3, the light source was visible through it. The maximum brightness (Go) and maximum bending angle (β value) were also measured, and the results are shown in Table 1.

Comparative Examples 4 to 6 Crystalline silica (refractive index 1.54) with an average particle size of 6 μm per 100 parts of methacrylic resin (Mitsubishi Rayon: Acrypera MD, refractive index 1.49) (The particle size distribution of this product is shown in Figure 5. (indicated by (2)) were blended in the proportions shown in Table 1, and a sheet having a thickness of approximately 3 mm was prepared in the same manner as in Comparative Example 1. In Comparative Example 4, the light source was not transparent, but in Comparative Example 5, the light source was visible.

The results of these GO1β values and the weight per unit area of silica are shown in the first thorn. In addition, these samples correspond to the curves ■ and ■ in Figure 2 mentioned above, and the β value is 1.
It can be seen that the light source becomes visible below 0°.

(Effects of the Invention) The present invention has a structure as detailed above, and although it has a conventional structure, it has a low element-diffusion property.
However, it has the property that the light source cannot be seen through it, a property that has never been achieved before, and this is an industrially extremely useful directional light-diffusing plastic that can be used in brighter lighting equipment, display devices, etc. It is for M.

[Brief explanation of the drawing]

Figure 1 is a graph to explain the light diffusivity due to the difference in grain diameter of transparent fine particles in light-diffusing plastic.
The figure is an explanatory diagram of the method for measuring optical properties used in the examples of the present invention, and FIG. 3 is a graph showing the particle size distribution of transparent fine particles used in the examples and comparative examples. (1) ..... original source (2) ..... sample (
32...Luminance meter

Claims (1)

[Claims] 1. In a transparent plastic having a refractive index of N8, the following formula (1), (n) 0.02≦lN5-Np1≦o, 1--- (1) 4μ
≦dμ≦10μ・・・・・・°・ (Transparent fine particles with an average particle diameter dμ that satisfies the old condition, a refractive index equal to Np', and a particle size of 6μ or less mixed in by at most 5 weight) A light-diffusing plastic characterized by being dispersed at a concentration such that the maximum bending angle (β value) is 4° to 10°. '!!Nia C
The light-diffusing glasstic according to claim 1, characterized in that it is made of Vinyl Chloride Vinyl Resin. As transparent fine particles, crystalline silica, anatomical silica,
Claims 1 or 2 are characterized in that at least one of glass, lithium fluoride, calcium fluoride, calcium carbonate, barium sulfate, aluminum hydroxide, and muscovite is used. The light-diffusing plastic described.