Uses and properties of photochromic compounds

Abstract The use and properties of photochromic compounds are discussed. Its performance shows a certain color change, and the exposure changes from one color to another under ultraviolet radiation. Then it changes back to a colorless state after the light source is removed. Its use is very wide, for example, can be used to make decorations on decorative ornaments and production of optical recording elements.

Keywords Photochromic compound ink

Abstract This paper expounds applications and properties of photochromic compounds.Photochromic compound is characterized of changing from one colour to another under UV radiation and returned to be colourless after removal of the light source.It has a wide of applications,such as for decorative patterns and Optical recording elements.

Key words photochromism;compound;ink

First, the use of photochromic materials

The use of photochromic materials is very extensive. The reason why people are interested in the properties of photochromic materials: First, because it has photosensitizing properties of photochromism under different intensity and wavelength light irradiation, it is also used in the industry in addition to general decorative and packaging materials. Protection against human eye and human damage caused by strong light radiation such as nuclear explosion test. The second is that due to the reversible cycling performance of different intensity and wavelength light irradiation energy, various kinds of optical shutters, video media, and information storage components in computers can be produced. In particular, after the laser appears, various necessary light intensities are provided. It promoted its application in information data processing systems. Third, it is sensitive to varying degrees of heat and discoloration, can be used as a temperature indicator to control chemical polyfluorene reactions. Its performance on photosensitivity, reversibility, and thermal sensitivity to heat is described below.

1. Based on the photosensitivity of photochromic materials to discoloration of light of different intensities and wavelengths, its use is as follows.

(1) Used as decorations and protective packaging materials: art designs on decorations such as wigs, lipsticks, nail polishes, root carvings, lacquer carving crafts, tie, headscarf, indoor curtain fabrics, wall paper, T-shirts, toys, billboards, etc. , Printing materials can be paper, textiles, plastics, metal plates, wood and so on. According to the design, the pattern text needs different color and different kinds of photochromic materials. Adding such materials to auxiliaries such as adhesives, thinners, surfactants, etc. for general inks or coatings, mixing them into color inks or coatings, and then screen printing, offset printing, pad printing, transfer printing, or computer-controlled printing. Jet printing and other methods, even brushing method with manual brush onto the substrate to make the above products or semi-finished products.

Some photochromic materials become black, blue, and yellow due to light, and can be made into packaging films, color filters, dimming glass windows for buildings, screen glasses for automobiles and airplanes, gun sights, periscopes, and various Radiation control equipment. NCR used its special color change as a camouflage and did a lot of research on how to match the colors of people and equipment with the surrounding environment to achieve camouflage. They painted the photochromic material on various types of ordnance weapons for permanent camouflage, that is, different seasons and different daily sunlight intensity, still have effective camouflage effect.

(2) As a self-developed holographic recording camera: A new type of auto-developing dry photographic technology was developed using the photosensitivity of photochromic materials. Apply a thin layer of photochromic substances (such as spiropyrans, fulgides, oximes, fluorenone, beta-tetrakalone) to various supports (paper, transparencies, glass plates). Etc.) These materials are not sensitive to visible light and are only sensitive to ultraviolet light to form a colored image. A black-and-white negative film is obtained by a masking technique. The resolution of this imaging method is high and no operational error occurs. Images can be recorded and eliminated repeatedly. It can also be used in color photography and color films, and it has been reported that such auto-develop technology has been officially used in Hollywood film companies for filming. It can also be used in X-ray microphotography and biophotography.

(3) As a radiation meter: Photochromic materials are particularly sensitive to strong light, so they are used to make dosimeters for strong light radiation. Dosimeters are simple, inexpensive, and durable. It can measure ionizing radiation and detect doses of ultraviolet rays, X-rays, gamma rays, and the like. If they are painted on the outside of the spacecraft, the dose of high radiation can be measured quickly and accurately.

Used as a light color filter and filter to control the intensity of radiation. The discoloration of the photochromic is related to the light intensity. It changes color with the intensity of the incident light. If a multi-layer photochromic sheet is continuously used, the light intensity can be continuously reduced to become a filter. In this way it will protect the eyes and body from the glare. The United States company Corming glass work company manufactures goods for Bestlit photogray light guide can be used for daylight protection, flash protection. The strobe in the light guide device developed by NCR Company of USA, when the nuclear explosion ignites with the electron detector, makes the light color film develop color, this can filter out the harmful strong radiation. This device has been used for US Air Force equipment.

2. According to the reversible cycling performance of photochromic materials, its use is as follows.

(1) Make a note memory component of a computer. When the photochromic material is irradiated with light of different intensity and wavelength, the color of the repeated cycle can be reverted, and the color can be faded. The memory element made of the photochromic material can have the information "with" and "with" of the ferromagnetic memory. No exchange operation is comparable. With this chemical recording element, the density of the recorded information is so large that it is hard to imagine that the computer optical memory element manufactured by ITEK using a photochromic material can handle up to one billion information units, which is equal to 1200 standards (waves). Banded computer. Its ability to store information can record a 1,245-page Bible book on a piece of 5cm2 light color. The Cyanamid type 51-14e, a cyanamide company, has a resolution of 1580/mm. It is recorded and can be chemically "fixed". The "written" textual information is fixed and stored for a long period of time. It is no longer sensitive to all light.

Photochromic materials can be used for information encoding and storage. The reversibility of photochromic patches is used for password storage. The first set of codes is recorded by the UV light of wavelength λ1, and can be eliminated by Uis light of wavelength λ"1. Thus, several sets of codes can be recorded on the same photochromy, respectively read out with different wavelengths of light, so that both are simultaneously provided. We had technology that storage was also micronized.

The use of organic photochromic compounds as optical storage media has the following advantages: 1 high storage density, can theoretically achieve molecular B, storage density up to 1015b/cm2 (1 bit/cm2), in fact, as long as the laser Can achieve the smallest spot, can use it to record; 2 large signal to noise ratio, good fatigue resistance; 3 high sensitivity, fast speed, can quickly write and erase information; 4 anti-magnetic properties and thermal stability; 5 can save information for a long time, easy to process, low toxicity, and low price.

(2) Make an information display. It is used to make the navigation command center to control the dynamic display screen, use the ultraviolet laser light emitted by the cathode ray tube to develop and write, or use the ultraviolet laser to achromatize the video. For example, a 100 [mu]m thick polyester base is coated with a 4 [mu]m thick acrylic-B72 resin containing 20% ​​spiropyran photochromic material and a stabilizer is added to make a light color film. It can get a 1.5m × 1.5m image at a distance of 4.5m. Stitching with three materials also allows color display. Such devices can be used in aeronautical communications radar control systems, tactical spacecraft positioning, navigation equipment. The dynamic photochromic display helps the operator to adjust the position and speed of the engine. Photochromic wafers can be used as the main part of optical fax information processing to transmit optical faxes from satellites repeatedly.

(3) Make Photochromic Micro Image. Microfilm technology has a history of more than 100 years. With the continuous advancement of science and technology, the capacity of microfilming has been increasing. However, the larger the scale, the greater the distortion. Using PCMI technology can partially eliminate this defect, which can be reduced, corrected, and then reduced. A PCMI machine developed by the National Cach Register of the United States uses a photochromic sheet as a temporary master memory, and then performs photocopying from a photochromic plate. The storage photochromic crystal material is provided by Carson Labs. It can record 19 200 (10cm x 12.7cm) maps in a 5.3cm x 24cm x 21.8cm volume. You can quickly take out any projection at any time. On the 10cm x 12.7cm screen, it is very convenient to use, and it is now more convenient to store them in a computer.

3. According to the thermosensitivity of photochromic materials due to thermal discoloration and their chemical and physical properties, their uses are as follows.

(1) Use its thermal sensitivity to make temperature indications. NCR and Boring used AgI-HgI2 to display temperatures of 80°F, 115°F, 250°F, 300°F, and 425°F, and studied a variety of photochromic materials capable of sensitive discoloration at low temperatures to indicate the temperature scale.

(2) A photomask plate and a photoresist circuit board were fabricated. The spiropyran is applied to a primed polyester film or copper plate, and a patterned reticle is overlaid on it. A UV lamp is placed on the mask to expose the spiropyran to discolor when the light passes through the transparent part of the mask plate. The opaque part renders the spiropyrans unexposed to their original color. The spiropyrans that have been exposed to light remain less soluble in gasoline than unlighted ones. After chemical etching, the spiropyran was removed with solvent toluene. Due to the high resolution of spiropyran, a high resolution reticle or printed circuit board can be produced.

(3) Used as a chemical analysis reagent or to control the polymerization reaction. The photochromic material can be complexed with some metal ions to develop color. Spiropyran is particularly sensitive to trace amounts of acid and can be used as a chemical analysis reagent.

The color-changing material generates ions or free radicals upon irradiation, allowing the reaction to begin or terminate. The anti-cis-isomer is mainly cis in the light, so as to ensure that the main cis-compound participates in the polymerization in the polymerization reaction.

Second, the history of photochromic materials, photochromic phenomenon

1. The development of photochromic materials

In 1976, Meer first reported the color change of potassium dinitromethane in the light. In 1889, T. Phipson painted modern zinc-white paint on the gate, turning black during the day and turning white in the evening, causing the manufacturer's interest. In 1900, Marckwald observed that the organic compound Benzo-1-Naphthglidine and tetrachloro-2-naphthalenone turned from colorless to purple under sunlight or other strong light source, and returned to a dark place and returned to Primary colors confirm that this phenomenon is a photo-induced reversible phototropy reaction. In 1958, Hirshbery called this phenomenon photochromism, and proposed that photochromism and photobleaching cycles can constitute a chemical model, which can be used in chemical information storage. In the 1960s, light-colored glass was put on the market as the first product of light-color interactive materials. With the development of science and technology, people have synthesized many valuable organic and inorganic compounds, as well as metal-organic complexes such as: silver tetracyanophthalide silver (AgTCNQ), tetracyanophthalide xanthone (CuTCNQ) Metal organic electron transfer complexes are a class of bistable materials with optical and optoelectronic effects that have been used for photoreversible storage. The establishment of new theoretical and new test methods, such as X-ray, nuclear magnetic resonance, fluorescence analysis, Raman spectroscopy, and the application of lasers, can test the chemical structure of reactants, products and intermediates, giving light The development and application of color-changing materials have created a bright future. It is worth noting that the U.S. defense department has done a lot of work on photochromic materials, some of which can be found in AD reports and patents.

2. Photochromism

The general reaction of photochromism can be expressed by the following formula:

The B state is usually in a thermodynamically unstable or metastable state. It is not only in the electronic junction