Veitch Tech's Liquid Crystal Display Optical Film is an optical film formed by the principle of multiple refraction and focusing of light through the microstructure, and its unique technology and process reduces the absorption of light and ensures that the light penetrates to a higher level of brightness. In addition to increasing the brightness gain, it can also play a light diffusion and atomization function effect through the refraction and scattering of light.
Brightening Film
Brightening Film (BEF) is an optical film that combines a layer of dispersed prismatic structure and a backside light diffusion layer on the surface of PET with very good transparency, using acrylic resin, and using a combination of optical film with a dispersed and consistent prismatic structure, which is used to brighten the upper layer of the LCD to make the light recycling and concentrating of light through the microstructure of the brightening to produce the effect of increasing the brightness, and is designed to be high-brightness, with a diffusion function. High-brightness design with diffusion function, due to the diffusion layer of the substrate, thus eliminating the optical coupling (Wet out) phenomenon, the light display is more uniform, softer.
Diffusion film
Diffusion sheet (DL series) is a very good transparency on the surface of PET, acrylic resin, precision coating of a layer of randomly dispersed micron-structured diffusion particles, on the opposite side of PET and then precision coating of a layer of randomly dispersed micron-structured antistatic particles, used in liquid crystal displays, so that the light through the diffusion layer to produce multiple refraction and circumference, thus playing a homogeneous effect, so that the light display more uniform, so that the light out. This makes the light refracted and reflected by the diffusion layer many times, which plays a role in equalizing the light and makes the light display more uniform and softer.
Reflective film
Reflective film is a film that is manufactured by casting method, doping HR polymer optics and plasticizers in PET resin to achieve the effect of light blocking and high reflection, because the middle layer of the film absorbs light to a certain extent, which reduces the reflection effect. Therefore, a layer of HR dielectric film is added to the surface to achieve better reflection effect and anti-UV yellowing function.
A simple model of an optical film can be used to study its general properties such as reflection, transmission, phase change and polarization. If you want to study the loss, damage, and stability of optical films and other special properties, the simple model will not be able to help, then you must consider the film's crystalline structure, the structure of the body and the surface state, the film's anisotropy and inhomogeneity, the film's chemical composition, the surface contamination and interfacial diffusion, and so on. After considering these factors, it is not only to consider its optical properties, but also to study its physical properties, chemical properties, mechanical properties and surface properties, as well as the penetration and influence between various properties. Therefore, the study of optical thin film jumps out of the scope of optics and becomes a fringe discipline of physics, chemistry, solid state and surface physics.
While the optical phenomenon of thin films was noticed as early as in the 17th century, the study of optical thin films as a subject began after the 1930s, mainly because of the development of vacuum technology to provide the prerequisites for the preparation of various optical thin films. To date, optical thin film has been greatly developed, the production of optical thin film has been gradually moving towards serialization, programming and specialization, but there are still a lot of problems to be further solved in the research of optical thin film, the existing level of optical thin film in a number of work can not meet the requirements and need to be improved. In theory, not only the growth mechanism of thin film needs to be clarified, but also the optical theory of thin film, especially the optical theory applied to very short wavelength band needs to be further improved and refined. In the process, there is still a lack of effective means to realize the precise control of the film deposition parameter, so that the growth of the film has a certain degree of randomness, and the optical constants of the film, the thickness of the film, and the performance of the film have a certain degree of instability and blindness, all of which limits the improvement of the quality of the optical thin film. As far as the optical thin film itself is concerned, in addition to the optical properties that need to be improved and the light losses such as absorption and scattering that need to be reduced, its mechanical strength, chemical stability and physical properties all need to be further improved. In laser systems, the low anti-laser strength of optical thin films is one of the most important issues in optical thin film research. Several commonly used optical thin film components are described below. Also known as transmittance enhancement film, its main function is to reduce or eliminate the reflected light from optical surfaces such as lenses, prisms, plane mirrors, etc., so as to increase the amount of light transmitted by these elements and reduce or eliminate the stray light of the system.
The simplest transmittance-enhancing film is the monolayer film, which is a thin film with a low refractive index plated on the optical surface of an optical part. When the refractive index of the film is lower than that of the substrate material, the reflection coefficients r1 and r2 at the two interfaces have the same phase change. If the optical thickness of the film layer is a quarter of a certain wavelength, the optical range difference between two neighboring beams of light is exactly π, i.e., the vibration direction is opposite, and the superposition results in a reduction of the reflected light at that wavelength from the optical surface. Appropriate selection of the refractive index of the film layer, so that r1 and r2 are equal, when the optical surface of the reflected light can be completely eliminated.
In general, it is difficult to achieve the desired effect of increasing transmission with a single layer of transmittance enhancement film, in order to achieve zero reflection at a single wavelength, or to achieve a good effect of increasing transmittance in a wider spectral region, often using a double-layer, triple-layer, or even more layers of the number of reflectance-reducing film. Figure 1 of a, b, c are plotted on the surface of the Kg glass single-layer, double-layer and triple-layer transmittance-enhancing film of the remaining reflection curve. Its function is to increase the reflectivity of the optical surface. Reflective films are generally categorized into two main types, one is metal reflective film and the other is all-dielectric reflective film. There are also metallic dielectric reflective films that combine the two. General metal has a large extinction coefficient, when the light beam incident from the air to the metal surface, into the metal internal light amplitude rapidly attenuated, so that the light energy into the metal is reduced accordingly, while the reflected light energy increases. The larger the extinction coefficient is, the more rapid the attenuation of the light amplitude is, the less light energy enters the metal, and the higher the reflectivity is. People always choose those metals with larger extinction coefficients and more stable optical properties as metal film materials. In the ultraviolet region commonly used metal film material is aluminum, commonly used in the visible region of aluminum and silver, commonly used in the infrared region of gold, silver and copper, in addition, chromium and platinum are also commonly used as a number of special film film material. As aluminum, silver, copper and other materials in the air is easy to oxidize and reduce performance, so it must be protected by dielectric film. Commonly used protective film materials are silicon oxide, magnesium fluoride, silicon dioxide, aluminum oxide, etc.. The advantages of the metal reflection film is a simple preparation process, the work of a wide range of wavelengths; the disadvantage is that the light loss is large, the reflectivity can not be very high. In order to make the reflectivity of the metal reflective film to further improve the reflectivity of the film can be plated on the outside of the film with a few layers of a certain thickness of the dielectric layer, composed of metal dielectric reflective film. It should be noted that the metal dielectric reflective film increases the reflectivity of a certain wavelength (or a certain wave region), but destroys the neutral reflection characteristics of the metal film. All-dielectric reflective films are based on multi-beam interference. In contrast to a transmittance-enhancing film, the reflectivity of an optical surface can be increased by coating it with a film that has a higher refractive index than the base material. The simplest multi-layer reflective film is made of high and low refractive index of the two materials alternately evaporated into the optical thickness of each layer of a wavelength of a quarter of the film. Under these conditions, the reflected light vectors on each sector of the superposition are vibrated in the same direction. The synthetic amplitude increases with the number of film layers. Figure 2 gives the reflectivity of such a reflective film changes with the number of layers.
In principle, all-dielectric reflective film reflectivity can be infinitely close to 1, but the film's scattering, absorption losses, limiting the film reflectivity. So far, although the reflectivity of high-quality laser reflective film has exceeded 99.9%, but there are a number of work also requires it to continue to improve the reflectivity. Reflective film used in strong laser systems, more emphasis on its anti-laser strength, around to improve the anti-laser strength of such films carried out by the work of such films, so that the research of such films is more in-depth. It is one of the most diverse and structurally complex classes of optical films. Its main function is to split spectral bands. The most common interference filters are cutoff filters and bandpass filters. Cutoff filters allow the spectral region under consideration to be divided into two parts, one that does not allow light to pass (called the cutoff region) and another that requires light to pass fully (called the bandpass region). According to the position of the pass band in the spectral region can be divided into long-wave pass and short-wave pass two kinds, their simplest structure, respectively, where H, L, respectively, represents a thick layer of high and low refractive index, m is the number of cycles. The membrane system with the above structure is called symmetric periodic membrane system. If the spectral region under consideration is very wide or the passband transmittance ripple requirement is very high, the structure of the membrane system will be more complex.
Bandpass filters allow only a section of the spectral band to pass, while all other parts are filtered out, in accordance with their different structures can be divided into Fabry-Perot-type filters, multi-cavity filters, and induced transmittance filters. Fabry-Perot type filter structure and the law-per standard (see Fabry-Perot interferometer) the same, because the transmission spectral band obtained by it are narrower, so it is also called narrow-band interference filters. The transmittance of this filter is very sensitive to the loss of the film, so the preparation of a very high transmittance, half-width and very narrow filter is very difficult. Multi-cavity filters are also called rectangular filters, which can be used as narrow-band bandpass filters and wide-band bandpass filters, and it is also difficult to prepare multi-cavity filters with a wide wave region, high transmittance and small ripples.
The induced transmittance enhancement filter is a class of filters that matches the appropriate dielectric film system on both sides of the metal film to increase the potential transmittance, reduce reflection, and increase the passband transmittance. Although its passband performance is not as good as the full dielectric method - Per filter, but has a very wide cutoff characteristics, so there is still a lot of application value. Especially in the ultraviolet region, the general absorption of dielectric materials are relatively large case, its superiority is more obvious. Figure 3, a, b, c, respectively, give the Fabry-Perot type filters, multi-cavity filters and induced transmittance filters of the typical curve. A film that splits a light beam into two parts according to certain requirements and in a certain way. Spectroscopic film mainly includes wavelength spectroscopic film, light intensity spectroscopic film and polarization spectroscopic film and other categories.
Wavelength beamsplitting film is also called two-color beamsplitting film, as the name implies, it is according to the wavelength region of the beam into two parts of the film. This film can be a cut-off filter or bandpass filter, the difference is that the wavelength spectroscopy film should not only consider the transmitted light and to consider the reflected light, both require a certain shape of the spectral curve. Wavelength spectral films are usually used at a certain angle of incidence, in this case, due to the effect of polarization, the spectral curve will be distorted, in order to overcome this effect, the film must be considered depolarization.
Light intensity spectroscopic film is in accordance with a certain light intensity ratio of the beam into two parts of the film, this film is sometimes only consider a certain wavelength, called monochrome spectroscopic film; sometimes need to take into account a spectral region is called a broadband spectroscopic film; used for the visible light of the broadband spectroscopic film, also known as the neutral spectroscopic film. This film is also often used in oblique incidence, due to the effect of polarization, the polarization of the two beams of light can be a lot of difference in the polarization of the state, in some work, you can not take into account this difference, but in some other work (for example, some interferometers), the requirements of the two beams of light are depolarized, which requires the design and preparation of depolarized film.
Polarized beam splitting film is the use of light oblique incidence when the polarization effect of the film made. Polarization spectroscopy film can be divided into two types of prism type and flat type. Prism-type polarizing films use the polarization effect of the interface at the Brewster angle of incidence (see refraction and reflection of light on the dividing surface). When the beam is always Brewster angle incident to the interface of the two materials, regardless of the number of film layers, the horizontal direction of the vibration of the reflected light is always zero, while the vertical component of the vibration of the light with the increase in the number of film layers and increase, as long as the number of layers is sufficiently large, you can achieve the transmittance beam is basically parallel to the direction of vibration of the light, while the reflected beam is basically perpendicular to the direction of vibration of the light, so as to achieve the purpose of the polarization of the beam of separation, the prism type polarization film is not possible by air incidence. Since it is impossible to reach the Brewster angle at the interface of the two film materials by air incidence, the film must be plated on the prism, when the incident medium is not air but glass. Flat-plate type polarizing film is mainly used in oblique incidence by the dielectric reflective film of the two polarization components of the reflective bandwidth of the different and made. Generally high reflective films, as the angle of incidence increases, the reflection bandwidth of the vertical component gradually increases, while the bandwidth of the parallel component gradually decreases. Select the vertical component of the high reflection area, the parallel component of the high transmission area for the working area can be formed through the parallel component of the reflection of the vertical component of the polarizing film, this polarizing film angle of incidence is generally selected in the base of the Brewster angle near. Prism type polarizing film working wavelength range is wider, polarization can also be made higher, but it is more troublesome to prepare, not easy to make a large, anti-laser strength is also relatively low. Flat plate type polarizer works in a narrower wavelength region, but it can be made very large, and the anti-laser intensity is also higher, so it is often used in strong laser systems.
Figures 4 and 5 give the reflectance spectral curves of the neutral light intensity beam splitter film and the flat plate type polarizing beam splitter film, respectively.