JPH0551480A - Plastics havinig high transmittance and high diffusibility - Google Patents

Abstract

PURPOSE:To obtain a opal plastic having high total light transmittance and diffusing power and resistant to see-through. CONSTITUTION:The objective plastic contains two or more kinds of diffusing materials having different particle diameters dispersed in a plastic matrix. The average particle diameter of the diffusing material having larger diameter is 2-20mum and that of the material having smaller diameter is <=1.5mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opalescent plastic which is excellent in transmittance and diffusivity and has low transparency.

[0002]

2. Description of the Related Art Conventionally, opalescent plastics have been used for lighting equipment panels, shades, signboards, advertising lights, etc., for the purpose of making the lamp image of the light source invisible or diffusing the light of the light source. ing. Therefore, this opalescent plastic usually has a particle size of about 1 in a transparent plastic substrate (acrylic, styrene, polycarbonate, etc.).
It is generally prepared by adding and dispersing a diffusing agent such as barium sulfate having a thickness of μm.

[0003]

However, when the amount of the diffusing agent added is increased in order to make the lamp image of the light source invisible, the transmittance decreases, and conversely, the amount of the diffusing agent added is decreased to increase the efficiency of the device. There was a defect that the lamp could be seen and the thin part of the corner was transparent. Therefore,
An object of the present invention is to provide an opalescent plastic having a high total light transmittance, a high diffusibility, and a low transparency.

[0004]

In order to solve the above problems, the inventors have made various studies. As a result, the present invention has been completed by confirming the following by experiments. That is, the optical characteristics of the opalescent plastic are affected by the difference in refractive index between the diffusing agent and the plastic substrate and the particle size of the diffusing agent. In order to clarify the effect of the particle size of the diffusing agent, two types of diffusing agents, large and small, were added at the same ratio (wt%) to different plastic substrates. The plastic with a large diffusing agent has a small decrease in transmittance and is difficult to see through, but the diffusing property is low, while the plastic with a diffusing agent with a small particle size has a high diffusing property, but is transparent. It was found that the transmittance was low and the transmittance was low. Conventionally, the diffusing agent used is often a single compound having a small average particle size of about 1 μm, and it is transparent when high transmittance is required, or the transmittance is increased to prevent the transparency. There may be no.

Therefore, if a diffusing agent having a large particle size is added to a plastic base material in a necessary amount so that no see-through occurs, and a diffusing agent having a small particle size is mixed so as to have a required diffusivity. , These diffusing agents with different particle sizes complement each other's drawbacks, resulting in high transparency and high diffusivity, and an opaque opalescent plastic compared to those with a single particle size. is there.

Therefore, in the highly permeable and highly diffused plastic according to the present invention, two or more kinds of diffusing agents having different particle diameters are dispersed in the plastic base material, and the average particle diameter of the diffusing agents having different particle diameters is It is 2 μm or more and 20 μm or less for a large particle size, and 1.5 for a small particle size.
It is less than or equal to μm. The plastic substrate used in the present invention is not particularly limited, but examples thereof include transparent plastics such as acrylic, styrene, and polycarbonate.

The substance constituting the diffusing agent may be the same as the ordinary diffusing agent and is not particularly limited, but examples thereof include barium sulfate, alumina and calcium carbonate. The substance forming the diffusing agent having a large particle size and the substance forming the diffusing agent having a small particle size may be the same or different from each other. Further, as the diffusing agent having a large particle size and / or the diffusing agent having a small particle size, two or more kinds of substances may be used in combination, or two or more kinds having an average particle size may be used in combination.

As described above, the optical properties of opalescent plastics are also affected by the difference in refractive index between the diffusing agent and the plastic substrate. For example, when the difference in the refractive index becomes large, the reflectance becomes high and the transmittance becomes low. Therefore, a material having a difference in refractive index within ± 0.2 is usually used. However, in the present invention, the difference in refractive index between the diffusing agent and the plastic substrate is not particularly limited.

No particular limitation is imposed on the blending ratio of the diffusing agent having different particle sizes and different sizes with respect to the plastic substrate.

[0010]

When a diffusing agent having different average particle diameters in a specific range and different in particle size is dispersed in a plastic substrate, the diffusing agent having a large particle diameter prevents see-through and improves permeability. A diffusing agent having a small particle size improves diffusivity.

[0011]

EXAMPLES Examples and comparative examples of the present invention will be shown below, but the present invention is not limited to the following examples. -Examples 1-5 and Comparative Examples 1-5-50 mm x 50 mm by adding and dispersing a diffusing agent in the base resin that constitutes the plastic substrate and injection molding
A test piece of × t2.0 mm was prepared. The constituent material and refractive index of the base resin, the constituent material of the diffusing agent, the refractive index, the average particle diameter (μm) and the addition amount (wt%) to the base resin used in each example are as shown in Table 1 below. is there.
In each of the examples, two types of diffusing agents having large and small particle sizes were used, and in each of the comparative examples, only one type of diffusing agent having a small particle size was used.

The test pieces obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were examined for total light transmittance, diffusivity, and see-through. The total light transmittance was measured by a self-recording spectrophotometer. The diffusivity was determined according to the following formula, with a characteristic value D representing the diffusivity defined by DIN 5036. The larger the characteristic value D, the better the diffusivity.

Diffusivity D = (L20 + L70) / (2 × L5) (In the formula, L5, L20, and L70 are 5 °, 20 °, and 70 ° with respect to the sample when light is incident on the sample at 0 °. The brightness value of the transmitted light at an angle of ° is shown.) See-through is a 100 W incandescent lamp (clear) through the test piece, and it is visually judged whether the filament is visible or not. When it was slightly visible, it was evaluated as Δ, and when it was visible, it was evaluated as ×. At this time, the distance between the incandescent lamp and the test piece was 30 cm, and the distance between the test piece and the eye was 20 cm.

The above results are shown in Table 2 below.

[0015]

[Table 1]

[0016]

[Table 2]

As shown in Tables 1 and 2, Examples 1-5
It was confirmed that the test pieces obtained in Example 1 had almost the same diffusivity as the test pieces obtained in Comparative Examples 1 to 5, but had a high total light transmittance and no transparency. ..

[0018]

EFFECTS OF THE INVENTION The high-transmission and high-diffusion plastics according to the present invention are opalescent plastics having a high total light transmittance, a high diffusibility and a low transparency.

Claims (1)

[Claims] 1. A diffusing agent having two or more kinds of different particle diameters dispersed in a plastic substrate, and an average particle diameter of the diffusing agent having different particle diameters is 2 μm or more 2
0 μm or less, 1.5 μm for small particles
High transmission high diffusion plastic which is: