Since the luminous intensity of the LED is relatively high and relatively concentrated, it is easy to cause glare and glare in the practical application. In this case, light diffusing materials have been widely used.
Light diffusing material refers to a material that can transmit light and effectively scatter light. It can convert point and line light sources into line and surface light sources. Generally, light diffusing particles with different refractive index of transparent substrate are added to transparent base. Prepared in the material. It can be used in the backlight module of a liquid crystal display, and can also be used in a surface light source such as a signboard or a window.
The Dow Corning E-Powder product line is a crosslinked silicone elastomer white powder with an average particle size of approximately 2 um and stable heat resistance. It can be used in substrates with high temperature processing requirements such as polycarbonate, and has different functional groups. Grades such as methacryloxy (grade 30-424), epoxy (grade EP-2601), etc. are available.
This article will introduce the use of E-Powder products as a light diffusing agent in polycarbonate and compare it with other commercial light diffusing agent products.
Experimental part
1. Formula of light diffusing material
Since the amount of the light diffusing agent added is small, in order to better disperse in the polycarbonate substrate, the masterbatch having a light diffusing agent concentration of 5% is first formed, and then diluted with polycarbonate to form a light diffusing material. .
In Table 2, for example, a final concentration of 0.05% of the light diffusing agent in the polycarbonate is used, and the final concentration can be adjusted correspondingly with the amount of the mother batch diluted.
2. experiment procedure
The polycarbonate was dried at 110 ° C for 3 hours, and a 5% concentration of light diffusing agent masterbatch supported on a polycarbonate was prepared on a twin-screw extruder. Then, the granules were diluted with polycarbonate on a twin-screw extruder according to different parent particle addition ratios, and finally a light diffusing material having different light diffusing agent concentrations was obtained. Test samples were made using an injection molding machine and tested.
3. Test items and methods
Results and discussion
1. Optical performance: sample thickness 1.5mm
In general, light transmittance and haze are technical indicators often used to characterize optical properties. Light transmittance is expressed as a percentage of the ratio of the luminous flux of the transmitted material to the incident luminous flux; haze, also known as turbidity, is the degree of unclear material, such as the appearance of a cloud or turbidity, with scattered light flux and transmitted material. The percentage of the luminous flux ratio is expressed. In the application of light diffusion, haze is difficult to accurately characterize the actual effect of light diffusion. Therefore the light diffusion angle is used to describe this optical property.
The light diffusion angle (also referred to as FWHM-full width half maximum) is the angle corresponding to half of the maximum light intensity in light diffusion, and generally does not exceed 60°. As shown in Table 5, when the haze of the light diffusing agent 3 was 90%, the light diffusion angle was only 0°; correspondingly, when the haze of 30-424 was 90%, the light diffusion angle was 60°.
As can be seen from Fig. 1, through the light diffusion model made by 30-424, the light becomes uniform and soft, the light source is not visible, and the light diffusion effect is better; and the light made by the light diffusing agent 3 is light. Diffusion template, the light is concentrated and glare, and the light source can be seen.
It can be seen that the magnitude of the light diffusion angle corresponds to the actual light diffusion effect, and is closer to the practical application of light diffusion than the value of the haze. The glare effect of the light diffusing agent 2 is between 30-424 and the light diffusing agent 3, and the values ​​of their light diffusing angles also correspond.
As shown in Table 5, in the case where the addition amount is 0.5%, the light diffusion angle of 30-424 is much larger than that of the light diffusing agent 1, and even larger than the light diffusing agent 2 of 0.8%, so 30-424 has a very good Light diffusion effect. The transmittance and light diffusion angle of EP-606 and EP-2601 are relatively balanced.
In this experiment, the light diffusion angle of the light diffusing agent 3 at the added amount of 0.8% was 0° because the amount of the acrylic light diffusing agent added was generally 2% or more in order to have a good light diffusing effect.
2. Mechanical properties and flame retardant properties:
It can be seen from Table 6 that 30-424 has the least influence on the impact strength of polycarbonate compared to other light diffusing agents, because the silicone elastomer powder has a crosslinked structure, which is relatively soft and can help. Polycarbonate releases internal stress. However, the above several kinds of light diffusing agents have no significant influence on the tensile strength and tensile modulus of polycarbonate. As for the flame retardant properties, after adding the above several light diffusing agents, as with pure polycarbonate, they are all UL 94 1.6 mm V2 grades.
3. Flow performance:
In order to simulate the effect of different light diffusing agents on melt flow and stability during the actual extrusion process of plastics, the heating time during the MFI experiment was extended (as shown in Figure 2). It can be seen from Fig. 2 that at a temperature of 300 degrees, as the heating time is extended, the melt index of the light diffusing agent added is smaller than that of the light diffusing agent 1 added, and the melt flow is relatively small. Sex is more stable. This feature can be helpful in extrusion molding of plastic tubes and sheets, because for extrusion molding, the stability of the melt directly affects the quality and productivity of the product.
It can be seen from the experimental comparison that the E-powder series of light diffusing agents can provide very good light diffusion effects. By choosing different grades of the E-powder series, a good balance of light transmission and light diffusion can be achieved. The 30-424 light diffusion effect is particularly pronounced under the same amount of addition, which means that 30-424 can be added less to achieve the same light diffusion effect than other commercial light diffusing agents, thereby reducing costs.
Light diffusing material refers to a material that can transmit light and effectively scatter light. It can convert point and line light sources into line and surface light sources. Generally, light diffusing particles with different refractive index of transparent substrate are added to transparent base. Prepared in the material. It can be used in the backlight module of a liquid crystal display, and can also be used in a surface light source such as a signboard or a window.
The Dow Corning E-Powder product line is a crosslinked silicone elastomer white powder with an average particle size of approximately 2 um and stable heat resistance. It can be used in substrates with high temperature processing requirements such as polycarbonate, and has different functional groups. Grades such as methacryloxy (grade 30-424), epoxy (grade EP-2601), etc. are available.
This article will introduce the use of E-Powder products as a light diffusing agent in polycarbonate and compare it with other commercial light diffusing agent products.
Experimental part
1. Formula of light diffusing material
Since the amount of the light diffusing agent added is small, in order to better disperse in the polycarbonate substrate, the masterbatch having a light diffusing agent concentration of 5% is first formed, and then diluted with polycarbonate to form a light diffusing material. .
In Table 2, for example, a final concentration of 0.05% of the light diffusing agent in the polycarbonate is used, and the final concentration can be adjusted correspondingly with the amount of the mother batch diluted.
2. experiment procedure
The polycarbonate was dried at 110 ° C for 3 hours, and a 5% concentration of light diffusing agent masterbatch supported on a polycarbonate was prepared on a twin-screw extruder. Then, the granules were diluted with polycarbonate on a twin-screw extruder according to different parent particle addition ratios, and finally a light diffusing material having different light diffusing agent concentrations was obtained. Test samples were made using an injection molding machine and tested.
3. Test items and methods
Results and discussion
1. Optical performance: sample thickness 1.5mm
In general, light transmittance and haze are technical indicators often used to characterize optical properties. Light transmittance is expressed as a percentage of the ratio of the luminous flux of the transmitted material to the incident luminous flux; haze, also known as turbidity, is the degree of unclear material, such as the appearance of a cloud or turbidity, with scattered light flux and transmitted material. The percentage of the luminous flux ratio is expressed. In the application of light diffusion, haze is difficult to accurately characterize the actual effect of light diffusion. Therefore the light diffusion angle is used to describe this optical property.
The light diffusion angle (also referred to as FWHM-full width half maximum) is the angle corresponding to half of the maximum light intensity in light diffusion, and generally does not exceed 60°. As shown in Table 5, when the haze of the light diffusing agent 3 was 90%, the light diffusion angle was only 0°; correspondingly, when the haze of 30-424 was 90%, the light diffusion angle was 60°.
As can be seen from Fig. 1, through the light diffusion model made by 30-424, the light becomes uniform and soft, the light source is not visible, and the light diffusion effect is better; and the light made by the light diffusing agent 3 is light. Diffusion template, the light is concentrated and glare, and the light source can be seen.
It can be seen that the magnitude of the light diffusion angle corresponds to the actual light diffusion effect, and is closer to the practical application of light diffusion than the value of the haze. The glare effect of the light diffusing agent 2 is between 30-424 and the light diffusing agent 3, and the values ​​of their light diffusing angles also correspond.
As shown in Table 5, in the case where the addition amount is 0.5%, the light diffusion angle of 30-424 is much larger than that of the light diffusing agent 1, and even larger than the light diffusing agent 2 of 0.8%, so 30-424 has a very good Light diffusion effect. The transmittance and light diffusion angle of EP-606 and EP-2601 are relatively balanced.
In this experiment, the light diffusion angle of the light diffusing agent 3 at the added amount of 0.8% was 0° because the amount of the acrylic light diffusing agent added was generally 2% or more in order to have a good light diffusing effect.
2. Mechanical properties and flame retardant properties:
It can be seen from Table 6 that 30-424 has the least influence on the impact strength of polycarbonate compared to other light diffusing agents, because the silicone elastomer powder has a crosslinked structure, which is relatively soft and can help. Polycarbonate releases internal stress. However, the above several kinds of light diffusing agents have no significant influence on the tensile strength and tensile modulus of polycarbonate. As for the flame retardant properties, after adding the above several light diffusing agents, as with pure polycarbonate, they are all UL 94 1.6 mm V2 grades.
3. Flow performance:
In order to simulate the effect of different light diffusing agents on melt flow and stability during the actual extrusion process of plastics, the heating time during the MFI experiment was extended (as shown in Figure 2). It can be seen from Fig. 2 that at a temperature of 300 degrees, as the heating time is extended, the melt index of the light diffusing agent added is smaller than that of the light diffusing agent 1 added, and the melt flow is relatively small. Sex is more stable. This feature can be helpful in extrusion molding of plastic tubes and sheets, because for extrusion molding, the stability of the melt directly affects the quality and productivity of the product.
It can be seen from the experimental comparison that the E-powder series of light diffusing agents can provide very good light diffusion effects. By choosing different grades of the E-powder series, a good balance of light transmission and light diffusion can be achieved. The 30-424 light diffusion effect is particularly pronounced under the same amount of addition, which means that 30-424 can be added less to achieve the same light diffusion effect than other commercial light diffusing agents, thereby reducing costs.
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