Luminescent tape —— How much do you know？
Luminescent tape is made of aluminate system, silicate system and sulfide / sulfur oxide system. It can also be called luminous tape, glow in the dark tape and photoluminescent tape.
In the natural light, fluorescent lamps, incandescent lamps and other light sources after a certain period of time, can continue to shine overnight, people have been accustomed to call it luminous film.
According to their application, they can be divided into two categories: organic light emitting products made of organic materials and inorganic materials combined with inorganic products.
The main application environment of light emitting materials is organic light-emitting products. With the expansion of applications, the varieties of luminous products are increasing.
In the preparation of organic light-emitting products, a lot of technical difficulties should be solved, such as:
- The contradiction between the refinement of luminescent materials and the decrease of luminescence properties
- Dispersion and poor settlement of luminescent materials due to the inconsistent density or particle size of the products
- Weatherability of organic light emitting products used outdoors
- Problems in the production of luminous products, such as uneven contraction of light emitting plate and uneven luminescence.
Photoluminescent tape structure
Luminescent tape is a kind of functional film with multilayer structure with light storing and luminescent material.
It is usually composed of transparent protective layer, luminous layer, reflective layer, pressure-sensitive adhesive layer and removable release paper layer, as shown in Fig. 1.
Each layer has different components and functions, and details are described below.
Fig. 1 Luminescent tape structure
Fig. 1 Luminescent tape structure
Composition of each layer of luminescent tape
The ordinary luminescent tape is composed of five parts: transparent protective layer, luminous layer, reflecting layer, self adhesive layer and release paper layer.
The transparent protective layer is a transparent film made of organic resin, which can protect the luminous layer and improve the luster of the luminous film.
Luminescent layer
The luminescent layer is made of light storing luminescent material, carrier resin, plasticizer, auxiliary agent and solution.
The thickness of the layer depends on the use, and the brightness of the luminous film increases with the increase of the thickness of the luminous layer.
When the luminous layer reaches a certain thickness, the brightness of the luminous film is no longer increased.
The thickness of the luminescent layer is usually in the range of 0.02 ~ 2.0mm, and the mass percentage of the material is:
Carrier resin 20% ~ 95%
Light storing luminescent materials 5% ~ 80%
Plasticizer 0 ~ 60%
Additives 0 ~ 30%
In a word, the brightness of the light emitting film varies with the type of the luminescent material, the content of the luminescent material and the thickness of the luminous layer.
Reflective coating
Because the luminescence of the luminous layer spreads to both sides, the reflecting layer is added on one side of the luminous layer, and the luminous reflection of one side is emitted together with the luminescence of the other side, so that the brightness of the luminous layer can be doubled.
Reflective layer can be white or light colored film or paper, also can be light or white paint coating, white effect is best. The thickness can be controlled from 0.01 to 0.5mm.
The coating is coated with carrier resin, plasticizer, additive, pigment and filler, and the mass percentage of each component is as follows:
Carrier resin 10% ~ 98%
Plasticizer 0 ~ 60%
Additives 0 ~ 30%
Pigment 2% ~ 80%
Packing 0 ~ 40%
The adhesive layer usually selects acrylic resin or rubber resin, so that the luminous film has self-adhesive function.
The release paper is a universal coated paper, which acts as an insulating adhesive.
Method for preparing luminescent tape
There are many methods for the preparation of luminescent films. The basic principle is to disperse light emitting materials uniformly in organic medium and form thin films. There are usually three basic methods for industrial production.
Blow molding
The flow chart of the luminous film prepared by blow molding method is shown in Fig. 2.
The process is as follows:
Fig. 2 Process flow diagram of luminous film prepared by blow molding
① According to the design of the formula, weighing a variety of materials into the mixer, mixing materials evenly;
② The mixed material is made into luminous plastic granule;
③ The luminous plastic particles are sent into the extruder of the blow molding unit, heated and extruded, blown and cooled to form, and then the tube can be rolled up to obtain a cylindrical luminous film;
④ The tubular luminous film is cut open or printed with white reflecting layer to obtain the luminous film;
⑤ The transfer coating process is used to prepare the pressure-sensitive adhesive for the luminous film, and the finished product is cut and packaged.
Fig. 2 Process flow diagram of luminous film prepared by blow molding
Advantages and disadvantages of luminescent films prepared by blow molding
Advantages are mainly reflected in:
- Compact equipment and low investment;
- Width and thickness of easy control film;
- The edge effect of film without extrusion has high yield and low cost;
- The intensity of the luminous film is high.
The disadvantages are shown as follows:
- The cooling rate is too small and the film is poor in transparency.
- The film thickness deviation is larger.
- Mixing machine, extruder for material cutting larger, etc.
Calender method
Calendering is the main method for the production of plastic film and sheet, it is already close to the viscous flow temperature of plasticized thermoplastic plastics through a series of counter rotating roller gap level, so that the material under compression and extension, into a certain thickness, width and surface finish of the plastic film products.
Most of the plastics used for calendering are thermoplastic amorphous plastics, most of which are pvc.
The process flow chart of the luminous film prepared by calendering method is shown in Fig. 3.
Fig. 3 flow chart of making luminous film by calendering method
Fig. 3 flow chart of making luminous film by calendering method
Advantages and disadvantages of luminescent tape prepared by calendering method
Advantage is:
- It has large production capacity, high speed and continuous production
- Product quality is good
- Flexible polyvinyl chloride film with a thickness of 0.05 ~ 0.5nm and a hard polyvinyl chloride sheet with a thickness of 0.25 ~ 0.7nm
- Comparison of blow molding process
Disadvantages are:
- Huge equipment
- Higher investment
- Maintenance complexity
- In the production process, the light emitting film will be subjected to repeated extrusion and shearing, and its performance will be affected.
Spread plate
Coating method is to use luminous material and organic resin to make luminous paint.
Using coating technology, the prepared luminous resin coatings are coated on different substrates.
The coating is made of gel, plasticizing or drying process to make luminous film.
The process flow chart of the preparation of luminescent film by coating method is shown in fig. 4.
The luminescent film prepared by coating method has the following advantages:
- Linkage production line can be used;
- The production process is stable and the quality is easy to control;
- The production efficiency is high, the production speed of the linkage production line is 3 ~ 50m/min, up to 100m/min;
- It can be suitable for the production of various products. Such as film products, artificial leather, flooring and so on.
The main drawback is the relatively large equipment, auxiliary equipment more.
Fig. 4 Process flow chart of luminescent film prepared by coating method
Fig. 4 Process flow chart of luminescent film prepared by coating method
Other methods
The luminescent tape is produced in large quantities by industrialized production method, which needs larger investment.
Small amount of luminescent tape can be made by screen printing method.
Specific methods are as follows:
① Light emitting material and transparent ink (ink blending oil) are blended into luminous ink;
② Making screen with 80~150 purpose polyester monofilament mesh;
③ Choose white, light or transparent substrates.
Using luminescent ink on the choice of good substrate printing, to ensure that the luminous coating to meet the design requirements of the thickness. If the selected substrate is transparent, a white coating is printed after the luminescent layer has been printed.
Comparison of properties of various luminescent films
The luminescent tape made of ZnS: Cu and Co light storing material in aluminate system, silicate system and sulfide system has low luminous intensity and short afterglow time, which is difficult to meet the requirement of luminous throughout the night.
For example, in German standard 67510-4, the main technical indicators of luminous properties of the luminescent film made by ZnS: Cu, Co are shown in table -1. The light resistance and weather resistance of the light emitting film are poor.
Table -1 German standard 67510-4 ZnS Cu, Co made luminous film luminous performance of the main technical indicators
The light storage material adopts ZnS and aluminate complex, and the luminescent film is not ideal.
WEALLIGHT, such as PLO, SB and REO, was used to produce blue, green, red and other color luminescent films. The films had high afterglow brightness, long afterglow time, good light resistance and good weatherability.
The luminescent properties of blue, green and red light emitting films produced by WEALLIGHT are compared with those of the previous ZnS based luminescent films by table -2.
Table -2 afterglow brightness and afterglow time of various luminous films
Note: the SB (blue) in the table refers to the light emitting film made of SB (blue) powder.
Application of luminescent tape
The new light storage luminescent materials have a wide range of applications: building decoration, transportation, military facilities, fire safety, daily life products and other fields.
Especially, it plays an important role in the field of fire safety related to people’s life and property safety.
Sep. 2002, the American “Newsweek” in the “9·11” event of the first anniversary of the 《Five Who Survived》, reported the World Trade Center South Tower survivors escape insider.
Among them, there is a description of the use of the light-emitting material produced by the luminous belt in smoke smell choking nose and dark corridor indicating the escape of people in the building. Excerpts are as follows:
Application of luminescent film in safety signs
Installation of luminous self-luminous evacuation sign system in buildings.
In June 1994, Germany developed a national standard for light storing self-luminous products (DIN67510-3) for evacuation. The standard specifies the performance requirements and setting requirements of luminous self-luminous evacuation sign system products. The standard has been adopted by European countries.
The United States is used Underwriters Laboratories UL 1994 standard, California Building Code (California Building Code) by the mandatory standard. This standard is adopted in most of the United States and some provinces in Canada.
Japan adopted the JIS Z 9100 (luminous safety signs board) standard formulated in February 1, 1987, which stipulated the performance requirements of refuge and escape sign products.
In April 2001 Chinese, People’s Republic of China Bureau of the Ministry of public security fire “building fire protection design standard”, “fire protection design of tall buildings” and “code for fire protection design of civil air defense works” by local provisions, mandatory requirements set light evacuation signs.
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