Effect of Mixed Light Difusion Agent on Properties of PC Light Diffusion Material

With the improvement of people’s awareness of energy conservation, the utilization rate of light-emitting diode (LED) light sources in production and life is gradually increasing, and it has been widely used in automobiles, household lighting and other fields. However, due to the unique luminous characteristics of LED light source, the luminous intensity of single light source is high, and it is easy to produce disability glare to human eyes. When the car meets together, it is more likely to have communication accidents. Therefore, it is necessary to flatten the LED light source, and the light diffusion material can soften the LED light source, that is, adding light-diffused material in front of the LED light source .

Polycarbonate (PC) is an ideal photodispersant. The common light diffusing materials in the market are polymethyl methacrylate (P M M A) crosslinked microspheres, polyphenylene (PS) crosslinked microspheres and organic silicon microspheres. When PS light diffuser is used, the haze of PC light diffusion board is small, which can not play a good light diffusion effect; when silicone light diffuser is used alone, the light transmittance is small, which can not meet the brightness requirements of PC light diffusion plate. In order to solve this problem, PC optical diffusion plates with high light transmittance and high fog were prepared by compounding three kinds of common optical diffusers and making use of synergistic effect.

1 Test part

1.1 Test raw materials.
P C; P M M A crosslinked microsphere light diffusion agent, particle size 3.0 μ m, PS crosslinked microsphere light diffuser, particle size 3.0 μ m, Wanda silicone microsphere, WD-103, particle size 2.8 μ m;

1.2 Test instruments and equipment.
Electrothermal constant temperature blast drying box, GZX-9070B; High-Speed Mixer, GH200DY; Twin Screw Extruder, SHJ-35; plastic injection Molding Machine, HY600; Microcomputer Controlled Electronic Universal material testing Machine, NQT-10; Electron Analyzer balance, TG3213A. UV-visible spectrometer, UV2450, Japanese Shimadzu; integrating sphere (ISR-2200), Shimadzu, Japan.

1.3 sample preparation.
The PC and the light diffuser are accurately weighed, in which the mass fraction of the light diffuser is 10%. It was dried at 100 °C for 12 hours in an electric constant temperature oven, then mixed at a high speed for 5 min in a high-speed mixer, and then melted and blended in a twin-screw extruder after waiting for 3 min. Extruder temperature.

The degree is set as follows: zone 1, 215 °C, 2, 225 °C, 3, 235 °C, 4, 245 °C, 5, 250 °C, 6, 255 °C, the head is 250 °C, and the speed of the screw is 80 r/min. light diffusion masterbatch was prepared by extrusion.
The quasi-accurate mass fraction of light diffusion masterbatch and PC base material is 400g (in which the mass fraction of light diffuser is 1.5%). It is first mixed at high speed for 3 min in a high-speed mixer, and then it is molded by injection molding machine.

PC light diffuses sheet material. The temperature of the injection molding machine is set as follows: 5 segments 220 °C, 4 segments 240 °C, 3 segments 270 °C, 2 segments 280 °C, 1 section 285 °C, injector, 280 °C. The rotating speed of the screw main engine is 30r/ min. The PC light diffusion plate material is placed in electrothermal constant temperature drying. It will be tested after 4 hours in the box.

1.4 performance testing.
According to GB/T 2410 Mel 2008, the light transmittance (Tt), the effective light diffusion coefficient (Td) of the light diffusion material and the haze (Td/Tt) were measured. The greater the number of light diffusivity, the better the effect of light source diffusion.
According to GB/T 1040.1 Mel 2006, the tensile strength and bending strength were tested. According to GB/T 1043.1 Mel 2008 test, notch impact strength.

2 results and discussion.

2. 1 study on the optical energy and shadow response of the complex system. Three kinds of light diffuser, PMMA, PS and silicone microsphere, were used to PC light diffusion plate light 42 when used alone and two kinds of compound. 2016 28 (3) MODERN PLASTICS PROCESSING AND APPLICATIONS. The impact of learning performance is shown in Table 1.

Light Diffusion Agent	Transmittance	Haze	Effective light diffusion coefficient
Not Added	85.7	2.5	2.14
PMMA	75.0	92.9	69.7
PS	74.5	23.5	17.5
PMMA/PS(1:3)	83.0	29.0	24.1
PMMA/PS(1:1)	62.6	96.6	60.5
PMMA/PS(3:1)	74.1	94.1	69.7
Silicone Base	37.3	98.9	36.9
PMMA/ Silicone base( 1:3 )	61.6	95.5	58.8
PMMA/ Silicone base( 1:1 )	71.3	89.5	63.8
PMMA/ Silicone base( 3:1 )	80.9	65.1	52.7
PS/ Silicone base( 1:3 )	60.9	96.9	59.0
PS/ Silicone base( 1:1 )	74.9	83.3	62.4
PS/ Silicone base( 3:1 )	77.5	41.3	32.0

It can be seen from Table 1 that when the mass ratio of PMMA to PS is 1:3, the light transmittance reaches a higher value of 83%. This is due to the synergism between PS and PMMA, which makes the overall particle size of the light diffuser larger, thus the light transmittance of the light diffusion plate is improved.
When the mass ratio of PMMA to PS is 1: 1, the haze reaches a higher value of 96.6%. This is due to the fact that the content of PMMA is consistent with that of PS. Due to the existence of two kinds of light diffuser with different refractive indexes in the system, the probability of refraction and reflection of light in PC light diffusion plate is increased, and the haze is higher. When the mass ratio of PMMA to PS is 3:1, the effective light diffusion coefficient reaches the maximum value of 69.7%, which can achieve a better light diffusion effect, which may be due to the addition of a small amount of PS is not enough to affect the haze of PC light diffusion plate, while the refractive index of PS is close to that of PC substrate, and a small amount of PS has little effect on light transmittance.

When the PMMA/ silicone system is added to the PC light diffusion plate, with the increase of the proportion of silicone, the light transmittance decreases and the haze increases. The reason is that silicone light diffuser is a kind of light diffuser with a “core-shell” structure. In addition, it can increase the probability of reflection and refraction of light passing through PC light diffusion plate, and increase haze. Because each reflection and refraction of light requires the loss of energy, the light transmittance decreases. When the mass ratio of PMMA to organosilicon is 3: 1, the light transmittance is 80.9%, and when the mass ratio of PMMA to organic silicon is 3: 1, the light transmittance is 80.9%. At 1: 3, the haze is larger, which is 95.5%, and when the ratio of PMMA to silicone is 1:1, the effective light diffusivity is larger, which is 63. 8%, which is better than that of organic silicon light diffuser alone.

When PS and silicone are used alone, the mass fraction of 1.5% can not meet the requirements of optical properties. It is found that PS can increase the light transmittance and organosilicon can increase the haze in the composite system. With the increase of the proportion of PS in the composite system, the light transmittance of PC light diffusion plate increases gradually, and the haze decreases rapidly. The effective light diffusion coefficient is larger when the mass ratio of PS to silicone is 1: 1, which is 62.4%, which is larger than that of PS and silicone as a single optical diffuser, and the light diffusion effect is good. The reason for the improvement of light transmittance of PS is that its refractive index is close to that of PC substrate, and the deflection angle of light refraction is smaller, and the reason for organosilicon to improve haze is due to the existence of “core-shell” structure, which increases the probability of light reflection and refraction.

2.2 effect of compound system on mechanical properties.

The effect of Light diffuser formula on the tensile strength, bending strength, notched impact strength and properties of PC photodiffusion plate materials, as shown in Table 2.

It can be seen from Table 2 that the mechanical properties of PC light diffuser do not change much compared with the phase ratio of PC light diffuser added with single optical diffuser, and the mechanical properties of PC light diffuser are not affected by different proportions of compound optical diffusive.It can be seen from Table 2 that the addition of compound light diffuser has little effect on the mechanical properties of PC light diffusion plate material compared with the phase ratio of single light diffuser. Because the content and particle size of the compound light diffuser are basically the same, it has little effect on the mechanical properties of PC light diffuser.

3 conclusion.

A) the compounding of PMMA cross-linked microspheres, PS cross-linked microspheres, and silicone cross-linked microspheres can meet the requirements of PC optical diffusion plate through synergistic effect.

B) in the PMMA-PS composite system, when the mass ratio of the composite is degree, bending strength, notched impact strength, and the influence of properties, as shown in Table 23: 1, the effective optical diffusivity of PC materials reaches a higher value.
As shown. The haze was 69.7%, which was higher than that of PC optical diffusion plate with only PMMA. Table 2 effect of light diffuser on the mechanical properties of PC materials in the composite system of PMMA and organosilicon when the mass of the composite is 1: 1, the effective optical diffusivity is larger, which is 63.8%, which is better than that of using a single optical diffuser. In the composite system of PS and silicone, the effective light diffusivity at 1:1 is 62.4%, the light transmittance is 74.9%, and the haze is 83.3%. It meets the requirements of real application and is larger than that of PS and silicone as a single optical diffuser, and the effect of light diffusion is good.

C) the mechanical properties of PC Light diffuser with compound optical diffuser are similar to those with single optical diffuser.