Retardation Film Research Articles

Randomizing polarization of displays for fundamental improvement of color mura caused by birefringence.

Most existing displays utilize polarization technologies to produce images and improve image quality. However, polarized light from displays causes color mura because of the birefringence of the polymer films used. Thus, eliminating color degradation remains a challenge despite the incorporation of complex polarization technologies such as retardation films. Our proposed random depolarization film (RDF) addresses this issue by randomizing the polarization of light from displays. Chromaticity measurements demonstrate that the RDF effectively compensates for color mura due to low-cost polymer films. Notably, the RDF compensation mechanism is independent of the RDF position and light source spectrum. Therefore, the RDF could be an innovative solution for color degradation in existing displays.

Effect of modified MgAl-LDH coating on corrosion resistance and friction properties of aluminum alloy

The in-situ growing approach was utilized in this article to construct the magnesium–aluminum layered double hydroxide (MgAl-LDH) film on the surface of a 1060 aluminum anodized film. To improve the corrosion resistance and friction qualities of aluminum alloy, the MgAl-LDH coating was treated using stearic acid (SA) and thiourea (TU). The aluminum substrate and anodized aluminum film layer corroded to varying degrees after 24 h of immersion in 3.5% (mass) NaCl solution, while the modified hydrotalcite film layer continued to exhibit the same microscopic morphology even after being immersed for 7 d. The results show that the synergistic action of thiourea and stearic acid can effectively improve the corrosion resistance of the MgAl-LDH substrate. The tribological testing reveals that the hydrotalcite film layer and the modified film layer lowered the friction coefficient of the anodized aluminum surface substantially. The results of the simulations and experiments demonstrate that SA forms the dense LDH-TU interlayer film layer by exchanging NO3– ions between TU layers on the one hand and the LDH-SA film layer by adsorption on the surface of LDH on the other. Together, these two processes create LDH-TU-SA, which can significantly increase the substrate's corrosion resistance. This synergistically modified superhydrophobic and retardant hydrotalcite film layer offers a novel approach to the investigation of wear reduction and corrosion protection on the surface of aluminum and its alloys.

Polyvinyl alcohol flame retardant film based on halloysite nanotubes, chitosan and phytic acid with strong mechanical and anti-ultraviolet properties

The research of additive biomass flame retardants is becoming more and more popular. In this work, amino modified halloysite nanotubes (A-HNTs), chitosan (CS) and phytic acid (PA) were introduced into polyvinyl alcohol (PVA) matrix to construct PA/A-HNT/CS/PVA organic-inorganic composite film with hydrogen bond and covalent bond cross-linking network structure. Adding PA/A-HNT/CS can remarkably improve the mechanical strength, UV resistance and thermal stability of PVA film. Compared with control PVA film, the transmittance of composite film in ultraviolet region decreases from 90 % to <15 %, and the tensile strength raises from 19.8 MPa to 31.0 MPa. The thermal decomposition temperature of the composite film increases, the weight loss rate decreases obviously, and the carbon residue can reach 26 wt% at 700 °C. The limiting oxygen index increases from 18.5 % to 32.2 %. Furthermore, the addition of this flame-retardant system can obviously reduce the combustion intensity of PVA, and its flame-retardant grade can reach V-0. It is of great significance to expand the application of PVA and the development of biomass flame retardant.

Negative biaxial retarder made from reactive molecules with X-shaped core structure

Although biaxial retarder films have merits of optical applications, limited numbers of the biaxial retarder have been developed using reactive mesogen (RM) materials. New X-shaped RM (XRM) molecules were synthesized and optical retarder films were fabricated using mixtures of a rodlike RM and the XRM. The in-plane retardation, the out-of-plane retardation and the NZ coefficient of the retarder films were investigated. The retarder films represented negative biaxial property or z-plate property depending on the chemical structure and the concentration of XRM.

Multitone reconstruction visual cryptography based on phase periodicity

The current no-computation grayscale image visual cryptography (VC) can only achieve halftone reconstruction but cannot truly achieve multitone. To solve this problem, we propose the concept of phase periodicity of the λ/2 retarder film and calculate the optical axis angle set with phase periodicity. According to the phase periodicity, we propose a λ/2 retarder film phase periodicity visual cryptography (RPP-VC). In RPP-VC, the secret pixels are encoded as the optical axis angles of nλ/2 retarder films and distributed to n shares. The decoding process does not require computation. The reconstructed image has no pixel expansion and can reach up to 23 tones. The quality of the reconstructed images has been greatly improved and the evaluation indicators of perceived quality are nearly doubled compared with other grayscale image VC schemes. The experimental results verify the feasibility of RPP-VC.

Luminescence-based circular polarization convertors: polarization conversion of linearly polarized photoluminescence from one-dimensionally aligned quantum rods using retardation films

Generation of circularly polarized (CP) light with high purity and light intensity was achieved using a single-, parallel, and multi-layered luminescence-based CP convertor composed of a linearly polarized luminescence (LPL) film and a quarter-wave plate.

A polarization modulated directional backlight autostereoscopic display

AbstractA polarization modulated directional backlight autostereoscopic display is proposed and demonstrated. The system consists of the orthogonally polarized backlight, the Fresnel lens array, a light shaping diffuser film, and a liquid crystal display (LCD) with a microphase retardation film. The autostereoscopic image pair carried by the directional light with different polarization directions is simultaneously projected to different spatial directions. The simulation and experimental results show that the directional projection of parallax images is realized for a high‐quality autostereoscopic display with large viewing angle and continuous viewing volume, hence making it suitable for practical applications.

Regulation of orientation birefringence for cellulose acetate film: The role of crystallization and orientation

Cellulose acetate (CA) based films are widely used in liquid crystal displays due to their outstanding transparency, and a certain orientation birefringence of CA films is required when they are used as retardation films. The regulation of orientation birefringence is usually from the perspective of stretch-induced orientation, while the effects of crystallization behaviors of CA films remain obscure. In this study, the roles of crystallization and orientation on the orientation birefringence of CA films were elucidated. For cellulose diacetate films, the orientation birefringence is dominated by the orientation degree. In comparison, apart from the orientation degree, crystallinity is another key variable to regulate the orientation birefringence of cellulose triacetate and plasticized cellulose triacetate films, originating from the birefringence heterogeneity of the crystalline and amorphous phases. These results provide valuable guidelines for the production of CA-based optical films with excellent optical performance.

Optical anisotropy of retarder film made from mixtures of rodlike and T-shaped reactive molecules: dependence on the chemical structure of T-shaped molecules

Five kinds of T-shaped reactive molecules were newly synthesized for optical retarder films. The retarder films were fabricated using the mixtures of rodlike reactive mesogen (RM) and the T-shaped molecules. The effect of the chemical structure of the T-shaped molecules on the optical anisotropy of the retarder films was investigated. The retarder films with the T-shaped molecules resulted in a greater magnitude of an in-plane retardation. Among the five kinds of the T-shaped molecules, the molecule with five benzene rings along the longitudinal direction and two benzene rings along the lateral molecular direction showed the widest liquid crystalline phase and the largest optical retardation. In addition, the NZ coefficients of the films were greater than 1 implying that the films were negative biaxial.

Generation of periodic and quasi-periodic two-dimensional non-diffractive beams with inhomogeneous polarization

In this work, two-dimensional periodic and quasi-periodic non-diffractive spatial inhomogeneous polarization optical fields are generated, numerically and experimentally, by the superposition of multiple plane waves with different polarizations. For the experimental implementation of the fields, synthetic phase holograms are employed in conjunction with half-wave and quarter-wave retarder films as polarization modulators. The obtained spatially inhomogeneous polarization optical fields show good quality and are in good agreement with numerical results. The proposed method is highly efficient for the generation of these types of optical fields.

Wavelength Dispersion Control of Three-Dimensional Birefringence in Retardation Film for VA-LCD

Wavelength Dispersion Control of Three-Dimensional Birefringence in Retardation Film for VA-LCD

Enhancement of Planar Orientation of Reactive Mesogen Molecules for Optical Retarder Film by Anisotropic Surface Plasma Treatment

We proposed a method for enhancing the planar orientation of reactive mesogen (RM) molecules by means of anisotropic plasma treatment. Anisotropic surface plasma, of which energy density is dependent on the azimuthal angle, was generated by column-shaped ceramic electrodes. The anisotropic plasma was discharged on the surface of a polyvinyl alcohol (PVA) alignment layer before the rubbing process began. The contact angle of the surface was increased from 12° to 83° after plasma treatment, indicating a hydrophobic property of the surface. From the atomic force microscopy (AFM) measurement, it was found that the grain size of the PVA layer was reduced and that the grooved patterns were formed provided that the plasma direction was parallel to the rubbing direction of the surface. Consequently, the planar orientation was enhanced, and the in-plane retardation of the photo-polymerized RM films increased when the parallel plasma was treated on the surface.

Numerical study on oblique stretching of viscoelastic polymer film

• Numerical format for oblique stretching of viscoelastic film is established. • The application scenarios of the membrane hypothesis are expanded. • Detailed numerical procedure and a complete numerical case are provided. • The influence of the y -direction stretching on thickness uniformity is investigated. Oblique stretching is a special approach for the fabrication of polymer film whose product is mainly used in the optical display field, such as compensation films, retardation films, et al. Nonetheless, the previous research reports on oblique stretching processing are still lacking, and the related numerical research is almost blank. This contribution uses the FEM (finite element method) to simulate the oblique stretching process of viscoelastic polymer film for the first time. The differential viscoelastic PTT (Phan-Thien and Tanner) model, one of the most realistic constitutive models is chosen. Furthermore, the polycarbonate melt was rheologically characterized and used as input material parameters in our simulations. Based on the membrane hypothesis and stabilization algorithms like DEVSS (discrete elastic viscous stress splitting), the specific numerical scheme is derived and the algorithm implementation is summarized. Finally, a complete numerical example of oblique stretching is demonstrated and compared with symmetric stretching. Based on the simulation results, the evolution of thickness and the influence of the y -direction stretching on thickness uniformity are further investigated.

P‐12.1: The Optimal Technique of Color Shift Based on Reverse Dispersion Material

Liquid Crystal Display (LCD) has witnessed tremendous development in the past decades. However, there are still some small flaws like L0 light leakage and color shift which are related to material dispersion. Herein, we illustrated two methods to modify the color shift of LCD based on material dispersion. The dispersion characteristic of LC, wave plate and retardation film could markedly impact the dark state light leakage and color shift. We believe that the reverse dispersion material holds a bright future.

47‐5: Distinguished Paper: Development of Reversed‐Dispersion Liquid‐Crystal Film to Improve the Display Quality of HDR‐IPS Panels

We have developed a new reverse dispersion retardation film with a thickness of 4 for IPS panels, which achieves excellent viewing angle performance, notably for oblique contrast ratio and color. HDR‐IPS panels applied this reverse retardation film could achieve a significant improvement of the halo viewing from oblique angle.

39‐2: Student Paper: Fast‐Switchable Scattering Device Based on Liquid‐Crystal Fibonacci Grating

In this work, we proposed a fast‐switchable quasi‐continuous grating (Fibonacci grating) as the scattering device for viewing angle control. The viewing angle varies from nearly 0 to 30 degrees. The proposed device requires a relatively small driving voltage (&lt;10 V), and shows a fast response time (&lt;7 ms), comparing with traditional scattering devices such as high retardation film, polymer dispersed liquid crystal and polymer network liquid crystal, etc. The proposed device shows promising potential in controllable viewing angle and wavefront coding.

Development of reverse dispersion liquid crystal film to improve “halo” of high‐dynamic‐range LCDs

AbstractWe have developed a new reverse dispersion retardation film with a thickness of 4 μm for IPS panels, which achieves excellent viewing angle performance, notably for oblique contrast ratio and color. HDR‐IPS panels applied this reverse retardation film could achieve a significant improvement of the halo viewing from oblique angle.

Flame retardant transparent films of thermostable biopolyimide metal hybrids

The development of flame retardant transparent films is important for electric devices and building materials it but it is still a challenge. Herein, flame retardant films having high optical transparency were developed from the amino acid-based biopolyimide (BPI) salt with aluminum (BPI-COOAl) and copper ions (BPI-COOCu). The microscale combustion calorimetry analysis revealed that for BPI-COOAl, the total heat released (THR) and peak heat released rate were 4.5 W/g and 18.9 kJ/g, respectively. These values were lower than those of its precursors and BPI-COOCu. BPI-COOAl was rated V-0 for the Underwriters Laboratories vertical burning standard test. The polymer also retained a high transparency of more than 80% transmittance at a wavelength of 450 nm. The tensile strength was also preserved at 63.7 MPa. For BPI-COOCu, 14.6 kJ/g THR and 47.1 MPa tensile strength were observed. When a colorful ion such as Cu was used, BPI-COOCu became a flame retardant film that was a green filter. The char formation of Al₂O₃ and Cu₂O in their respective polymer complexes was deduced as the main flame suppression mechanism. The present films of biopolyimide salts are advantageous in showcasing the balance of different essential material properties such as flame retardancy, thermo-mechanical stability, and transparency.

Phosphorus containing group and lignin toward intrinsically flame retardant cellulose nanofibril-based film with enhanced mechanical properties

Cellulose-based film material, due to its remarkable physicochemical properties, environmentally friend and low cost, has been widely applied in many high-end areas. However, the lack of functional properties (e.g., flame resistance) except poor mechanical performance severely hinders their further applications. Herein, bamboo-based phosphorylated cellulose nanofibrils (B-PCNFs) were prepared through a simple two-step method composed of phosphorylation and mechanical grinding process. The resultant film prepared via solvent casting process shows an excellent mechanical strength of 115.9 MPa, remarkable elongation at break of 53.1%, high Young's modulus of 2.5 GPa and impressive work of fracture up to 41.8 MJ m−3, respectively, which should be contributed to the formation of dense and homogeneous polymer networks reinforced by enhanced multiple interactions. When burned against the flame of alcohol lamp (700–800 °C), BHL-PCNF film also delivers appealing structural stability even over 25s, demonstrating a prominent flame resistance. Meanwhile, compared to original one, the peak heat release rate (PHRR) and total heat released (THR) of BHL-PCNF film produce a dramatical reduction, i.e., 87.3% and 86.6% for PHRR and THR, respectively. Based on the evolution of morphological and chemical structure, the highly improved flame resistance is strongly contributed to the synergy of phosphorus containing group and lignin, resulting in a protective layer composed of PxOy compound and carbon layer. The proposed mechanism for the enhanced flame retardant property is also declared and clarified. Thereby, this phosphorylated cellulose-based film that integrates outstanding mechanical performance and excellent intrinsically flame resistance holds promising potential candidate in practical applications, such as flame-retardant packaging materials.

2D/3D mixed frontal projection system based on integral imaging.

Two-dimensional (2D)/three-dimensional (3D) convertible or mixed display is one of the most important factors for the fast penetration of 3D display into the display market. In this paper, we propose a 2D/3D mixed frontal projection system that mainly contains a liquid crystal micro-lens array (LCMLA) and a quarter-wave retarding film with pinholes (QWRF-P). The LCMLA exhibits the focusing effect or no optical effect depending on the polarization direction of the incident lights. The forward incident lights pass through the LCMLA without any bending. After passing through the QWRF-P twice, half of the backward lights change the polarization direction with 90°, and the other half remains. Using our designed system, different display modes, including 2D display, 3D display, and 2D/3D mixed display, can be realized. The unique feature of the proposed 2D/3D mixed frontal projection system is that it can switch the display modes by simply changing the image sources without the need of any active optical devices. Moreover, the proposed system is compact, simple and space-efficient, which is suitable for the application in glassless 3D cinema and home 3D theatre.