1 Introduction
Polymer Dispersed Liquid Crystal (PDLC) is a mixture of nematic liquid crystal and polymer material in a certain proportion, and then uses heat curing or ultraviolet curing to initiate phase separation to form micron-level liquid crystal droplet dispersion Structure in a solid polymer matrix. Over the past 30 years, the electro-optical characteristics of PDLC have been thoroughly studied and have application prospects in many fields. The most obvious application is the electronically controlled dimming glass product that is becoming a hot investment. Strained liquid crystal (SLC) is a research field of a new type of electro-optic device obtained by applying tensile, shearing or pressing stress to PDLC products to change the optical properties. It quickly responds to large phase retarders and grating constants. Holographic gratings, scattering filters and scattering polarizers that change with pressure have special applications and attract attention. However, the strained liquid crystal can obviously be developed into a dimming glass without power consumption, and this dimming glass can also develop an alternative display panel.
2 Characteristics and application of SLC dimming glass
The structure of the PDLC electronically controlled dimming glass product is to sandwich the PDLC between ITO transparent conductive films and then the film between the glasses. The structure of SLC dimming glass is to sandwich the PDLC directly between the float flat glass, and the polymer is a very soft polymer adhesive. By pushing or stretching the upper and lower glass pieces from opposite sides or from opposite sides, the phenomenon of changing from the scattering state to the translucent state can occur. The reason for the translucent state is that the liquid crystal droplets change from a spherical shape to a long ellipsoid shape under the action of stress, and the liquid crystal molecules assume a configuration that is oriented along the shear direction, that is, the long axis direction of the ellipsoid. It can be regarded as a uniaxial crystal, with birefringence properties, showing a very light refractive index along the parallel shear direction, and an ordinary light refractive index along the vertical shear direction. The ordinary light refractive index no is equal to the polymer refractive index np, but the extraordinary light refractive index ne is not equal to the polymer refractive index np, so the PDLC film is a scattering polarizer at this time, half of the incident light is transmitted, and the other Half of the light is scattered. SLC dimming glass has the phenomenon of scattered polarized light, and also has a transparent projection screen function in a translucent state. The rear projection effect is better than the front projection effect.
PDLC electronically controlled dimming glass is suitable for making large-area fixed space partitions. The application engineering cases are all luxurious decoration of large institutions, large hotels, and large companies. The price of PDLC film products is very expensive, but now the market demand is increasing, and it has become a hot spot for investment in the special glass industry. In contrast, the new SLC dimmable glass is suitable for making small-area movable partitions and can be applied in a wider range of fields. In shopping malls, SLC dimmable glass can be used to make valuable commodity counters; in the company, SLC dimmable glass can be used to replace electric shutters; in the field of decoration, SLC dimmable glass can be used to make sliding doors and windows, folding doors and windows. SLC dimmable glass can also be used to make high-end gift boxes, such as jewelry, diamond rings, watches, medals, ginseng, cordyceps and other packaging boxes. The existing transparent projection screen is mainly an optical functional film attached to the glass window, SLC dimming glass can also be used as a translucent projection screen in shopping malls and other occasions, the effect is relatively good.
3 Preparation and application of SLC dimming display glass
The SLC dimmable glass technology is a UV curing production process. The float flat glass is cleaned, sprinkled with liner, closed two glasses, poured into a prepolymer and liquid crystal mixture, cured by UV exposure, and installed stainless steel. Frames and devices that can apply shear stress have become SLC dimmable glass products.
The nematic liquid crystal material used in the sample preparation experiment was PDLC005 (provided by Shijiazhuang Luquan New Electronic Material Factory), its birefringence no = 1.517, ne = 1.723; the prepolymer used was 30% epoxy resin DCL3000, 60 % Polyester acrylate MR100, 4% chain transfer agent and 4% photoinitiator TPO, 2% sulfonium salt are formulated into prepolymer; liquid crystal and prepolymer are mixed into liquid crystal adhesive at a mass percentage of 1 to 1. The glass used is 3mm thick float glass (provided by Hebei CSG); the diameter of the spacer microspheres used is 20? M (provided by Shenzhen Nano Technology Co., Ltd.). Clean the glass, spread 20 μm liner powder microspheres on one glass, and then cover another glass. Most of the two glasses overlap, leaving a small part of the step edge that does not overlap (to facilitate the subsequent application of stress experiment). Use a syringe to drip the liquid crystal glue on the glass below the step. The capillary phenomenon makes the liquid crystal glue fill the overlapping part between the two glasses. Place the two glasses with liquid crystal adhesive under a 24W UV lamp for UV curing. Use typed copy film as a mask for selective exposure. The sample is about 30cm away from the lamp and exposed for 5 minutes. The sample changes from transparent before curing to curing Backscatter frosted glass to obtain a patterned product. A glass frame is made of a stainless steel square tube, a key hole is installed on the glass frame, and twisting the key can easily apply shear stress, as shown in the photo in Figure 1. Figure 1 (a) is the sample scattering display state, the key is in the vertical position. Figure 1 (b) is the light blanking state of the sample, the key is in the horizontal position. When shear stress is applied to the product, the product becomes translucent and the character pattern is hidden.
Figure 1 Strained LCD dimming display, (a) display status, (b) blanking status
As we all know, the mainstream technologies of modern display are TFT-LCD, OLED, LED, PDP, E-INK, LCOS, etc. The SLC dimming glass described in this article is naturally a very small variety, which can display fixed characters, such as company name, auspicious Statements, Tang poetry and Song Ci, etc., are expected to have application prospects in the decoration of shopping malls, companies and hotels.
4 Conclusion
Strained liquid crystal (SLC) is a research topic of new application of electro-optic devices in the field of polymer-dispersed liquid crystal (PDLC) with special photoelectric characteristics, and SLC dimming glass is a new derivative of civilian products of PDLC electronically controlled dimming glass. A layer of flexible polymer dispersed liquid crystal film is sandwiched between two pieces of glass; its characteristic is that it can be changed from the scattering state to the translucent state only by applying shear stress without applying power, and the transmittance of the scattering state is less than 5%, and the transparent state is transparent The light rate is close to 50%; the translucent state has the functional effects of scattering polarizers and translucent projection screens; its preparation method is ultraviolet light curing technology. When preparing SLC dimming glass, typed copy film is used as a mask for selective exposure to obtain a patterned product. When shear stress is applied to the product, the product becomes translucent, and the character pattern is hidden. This SLC dimming display glass has application prospects in the decoration of shopping malls, companies and hotels.
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