Reflective film is nearly 50 years developed a new type of functional composites. Micro prismatic reflective film was developed in the late 80 s, due to its high brightness, good durability, at the same time, to overcome the traditional way of prismatic reflective material effective incident Angle is small, observation Angle is small, the reflected beams asymmetric faults, and therefore in need of high brightness of highway transportation is more and more widely used.

1, the reflective principle and structure

1.1 the principle

Micro prismatic reflective principle of reflective film is based on the light in the three-dimensional space, from a certain Angle of incidence, in three perpendicular plane three reflection, then down to reflect the original incident direction, as shown in figure 1.

Depending on the manufacturing process, occurring on the surface of the prism reflection has two kinds: one kind is air - resin (all) of the interface reflection, another kind is aluminum - resin interface reflection.

1.2 according to the different classification structure

According to the Type of the reflection, micro prismatic reflective membrane structure can be divided into two kinds: (as shown in figure 2, figure 3) has a coating Type reflective film (ASTM4956 called Type V Sheeting) and no reflective film coating pattern (called Type in ASTM4956 Ⅳ Sheeting). With reflective film color gray coating type, market prospects.

The two reflective membrane structural differences are:

(1) no coating type reflective film behind the pyramid is the air, thus reflecting the main is total internal reflection, which requires the pyramid must have a stable after air layer, so in no coating type reflective film with a layer of seal (Sealingfilm) (see figure 2), in order to prevent moisture into the air, dust and other impurities, cause the loss of back reflection coefficient.

(2) coating type reflective film coated layer after pyramid, general is aluminum. Mainly reflected in the resin - aluminum on the interface. Has had no seal coating type reflective film.

(3) due to the coating need to closed type reflective membrane, so there are supporting wall, look from the front, is a diamond or hexagonal grid. But not for type coating reflective film.

2, the performance of the micro prismatic reflective film

2.1 optical properties

No matter in such aspects as reflective intensity, wide Angle, micro prism type reflective film are better than a lens type reflective film are greatly improved. Figure 4 is reflective strength of three kinds of products the comparison of the initial value (0.2 ° Angle).

Former micro prismatic reflective film reflected light cone asymmetry, effective incident Angle is small, but after reflection unit and its array of design, basic solved these problems.

2.2 weather resistance

Although type micro prism in after reaching the service life of the reflective membrane, back reflection coefficient fell by 50%, but the back reflection coefficient remained in CD, lx - 1, 400 m 2, far higher than other two kinds of reflective film, as shown in figure 5 (0.2 ° Angle observation, 4 ° Angle of incidence).

3 the key techniques in the manufacturing, micro prismatic reflective film

3.1 key technology

Basic principle of micro prismatic reflective membrane of reflective although simple, but the manufacturing technology is related to materials science, optics, precision machinery manufacturing, and other multi-disciplinary, high technology fields. And, in the aggregate, the key technology of manufacturing micro prismatic reflective film has the following four.

3.1.1 unit structure and the array design

The traditional prismatic negative light materials mainly exist the following disadvantages:

(1) the effective incident Angle is small, when the incident Angle is greater than 20 °, due to total internal reflection phenomenon disappears, the brightness is almost lost.

(2) the observation Angle is small, that is, people can see inverse reflected light in the distance, near but can't.

(3) due to the nature of the three aspects of the reflection unit to reverse the asymmetric shape of reflected light cone is undesirable, the results from the different scanning Angle to observe the different back reflection intensity.

The ways to solve these problems mainly rely on the back reflection unit structure and the design of the array, such as transformation of three plane Angle size, make its have certain distribution, configuration or cell array according to certain rules. But due to the complexity of structure and array design, for the production of motherboards, replica, forming the demoulding after did a lot of difficulties, and implementation.

3.1.2 motherboard and replica

Because of micro prism type reflection unit height is 0.003 ~ 0.015 in 2 ~ 0.381 mm (0.078), and irregular shape, also have certain regularity in the plane arrangement, and the high requirement of forming surface is bright and clean degree, thus motherboard to precision machining. Board itself is not directly involved in the molding, machining is expensive, the area is finite, and mold use weekly is not high. Motherboard replica produce copy available mould and cobble together into any size, so that the industrial production.

3.1.3 determination of base material

As micro prismatic reflective film, the main material is engineering plastics, according to the different requirements of the using performance, choose a different plastic base. Main consideration of the index and solving the problems are: the weather resistance, plastic base of preheating properties and rheological properties, etc. Dar at present according to the different product series, mainly used for PVC, PC, PMMA, PET several kinds of material.

3.1.4 embossing technology

Due to micro prismatic reflective film of high optical performance requirements, therefore its embossing accuracy is quite high, in the process of embossing, are not allowed to appear adverse, bubble flow, defects such as scratches, the process conditions, such as temperature, pressure and so on are also very demanding.

4 the application prospect of

Due to micro prismatic reflective film of high reflective strength and performance of wide Angle, with the constant improvement of the motor speed, the high grade highway of growing, constantly complex road conditions, the application of micro prismatic reflective film market will be more and more wide. But other problems caused by the high strength, such as glare, as well as the practical application of design and background contrast, determines the type of micro prism reflective film type can not completely replace glass beads reflective film.