1. Explanation of professional terms
OCA (Optically Clear Adhesive), optical adhesive, is a special adhesive used to bond transparent optical components (such as lenses, etc.). It has the characteristics of colorless and transparent, light transmittance above 90%, good bonding strength, can be cured at room temperature or medium temperature, and has the characteristics of small curing shrinkage. To be brief, OCA is a layer of special double-sided adhesive with optical transparency.
LOCA (Liquid Optical Clear Adhesive), liquid optical adhesive (also known as OCR), is a special adhesive used for bonding transparent optical components. It is colorless and transparent and has a light transmittance of more than 98%. Good bonding strength, can be cured at room temperature or medium temperature, and has the characteristics of low curing shrinkage and resistance to yellowing. Compared with traditional OCA tapes, LOCA has its special advantages in certain application fields, which can solve some of the limitations faced by OCA tapes.
UV-OCA (also known as SCA optical glue on the market), that is, UV optical glue, the glue needs to be cured by UV ultraviolet rays.
2. Advantage and disadvantage comparison
Advantages of OCA process:
1). Reduce glare, reduce the loss of light emitted by the LCD, increase the brightness of the LCD, provide high transmittance, and reduce energy consumption;
2). Increase the contrast, especially the contrast under strong light;
3). The surface connection has higher strength;
4). It can effectively avoid Newton's ring;
5). The surface of the product is smoother;
6). Without borders, expand the visible area;
Disadvantages of OCA process:
1). The surface of the OCA film is sticky. When the release film is peeled off, it is easy to leave marks on the surface, and it is easy to produce bubbles when bonding. Easy to absorb dust and impurities to cause secondary pollution.
2). In the process of bonding OCA film and FILM, uneven manual pressure may cause bubbles to wrinkle.
3). The flowability of OCA is poor, and it is difficult to fill the gully of the ITO circuit or fill the ink when it is attached to the sensor or cover glass.
4). The bonding performance of OCA is not strong, and the product that fits well has the risk of rebound.
5). OCA is not conducive to large-size lamination, low production efficiency, and high labor cost.
6) OCA cannot effectively increase the strength of the screen and the ability of explosion-proof. After fitting, the screen has poor anti-explosion effect, is not resistant to falling, and the screen is easily damaged.
The advantages of LOCA over OCA are as follows:
Colorless and transparent, light transmittance is above 98%, good bonding strength, and can be cured at room temperature or medium temperature. At the same time, it has the characteristics of low curing shrinkage and resistance to yellowing. Compared with traditional OCA tapes, LOCA has special advantages in certain application fields and can solve the limitations faced by OCA tapes. Characteristics of liquid optical adhesive LOCA.
1). High light transmittance (total transmittance>99%)
2). The bonding strength is high and it is easy to fold the glue and repair the unqualified bonded parts.
3). High adhesion, high weather resistance, water resistance, high temperature resistance, UV resistance, long-term use will not cause yellowing, peeling and deterioration of the product.
4)．Can be used for super wide temperature application like automotive products.
The disadvantages of LOCA:
1). When LOCA is cured, it is difficult to cure the frame and FPC completely, and need to be cured again.
2). LOCA glue overflow is difficult to control, and glue overflowing to the edge is difficult to clean. Especially for large-size fittings (such as 15.6-inch 50-inch 72-inch), the glue overflow is difficult to control, the production cost is high, and the production efficiency is low;
3). The LOCA process is relatively complicated and needs to go through the process of dispensing graphics, pre-curing, and curing. Products need to be transported to different stations three or four times. The labor cost of production is also higher.
4). LOCA is easier to produce bubbles. It is easy to produce bubbles in the process of dispensing, leveling, and covering the sensor or cover glass.
5). In the process that LOCA is more prone to leveling, the thickness of the glue per unit area of leveling may be different.
6). During the curing process of LOCA, movement on the conveyor belt may cause displacement. The larger the sensor or cover glass area, the easier it will be.
Advantages of SCA process:
The SCA (UV-OCA) process overcomes all the shortcomings of the above two processes, and mainly has the following advantages:
1). Good filling performance, no bubbles, no glue overflow at the edges;
2). Adapt to a wide range of fitting sizes, medium and large sizes are more advantageous;
3). Strong rework performance;
4). Strong bonding performance;
5). The surface of SCA optical adhesive is non-sticky, easy to operate during lamination, quick adjustment, and high alignment accuracy;
6). SCA optical glue can flow under certain conditions of hot pressing, which eliminates the possibility of air bubbles;
7). SCA optical glue is a neutral product, which is not corroded and damaged by external moisture and water vapor, and it is excellent to protect the appearance of the product and the stability of the ITO circuit;
8). The SCA optical glue processing hot-pressing equipment can be used in large quantities at one time, with high work efficiency and large production capacity;
9). The production methods of SCA optical glue are diversified, and multiple sizes of bonding can be achieved in the same hot-pressing process;
10). The bonding method of SCA can obviously increase the strength and explosion-proof performance of the cover plate;
11). Excellent weather resistance, no yellowing;