Industry Focus

As a new type of human-computer interaction input medium, touch screen has the characteristics of simple, intuitive, convenient and humanized operation of each program interface, and has become one of the common and effective human-computer interaction problem input methods. In recent years, with the rapid development of 5G technology, Internet of Things, cloud computing, big data and other information technologies, more requirements have been put forward for touch products that are one of the mediums of human-computer interaction, such as ultra-large size, high-definition display, fast response, precise touch, etc., and the lamination technology of the touch screen has also developed from the traditional frame to the full lamination technology.

Full lamination technology, is to use optical glue to the panel and touch screen in a seamless way completely bonded together, because there is no air layer between the layers, can effectively reduce the loss of light reflection and light transmission, effectively isolate dust and other foreign matter and water vapor ingress, compared with the traditional frame technology, with better display effect and smooth touch operation and other advantages, has been widely used in communication services, banking and finance, education and training, entertainment facilities, industrial control, medical equipment and other industries.

As one of the important raw materials for full lamination, optical adhesive is mainly divided into two categories according to the form of the product, one is solid OCA optical tape, and the other is liquid OCR (Optical Clear Resin), which is subdivided into acrylic OCR and silicone liquid OCR. Silicone liquid OCR has the characteristics of colorless and transparent after curing, light transmittance of more than 98%, small curing shrinkage, and yellowing resistance. In the lamination process, silicone liquid OCR only needs to carry out the dispensing-lamination-leveling-degassing-curing process to complete the lamination, strong versatility, a glue can correspond to a number of different products, the size of the laminated product is not high, the gap filling is good, can be applied to large size, curved surface and various more complex structures and interfaces of the lamination.

Compared with acrylate OCR, silicone OCR can be cured at room temperature or medium temperature, with small curing shrinkage, yellowing resistance, high temperature and humidity resistance and cold and hot shock performance, and has obvious advantages in medium and large size touch screen products and automotive, industrial control, medical equipment and other industries with high requirements for environmental testing.

The performance of optical adhesive will directly affect the display effect and performance of the touch screen, so the choice of optical adhesive is very important when fully laminating. On the market, various optical adhesive materials have different properties, each has its own advantages and disadvantages in the process of use, customers need to choose according to the laminating equipment and process used in their respective products, product size and shape, materials used for lamination, surface conditions, use performance, etc., so how to distinguish the performance of optical adhesives, so that it matches the laminated products and obtains excellent performance, it is particularly important.

Generally, the performance of optical adhesives can be judged from the following aspects:

1. The appearance of optical adhesive materials: whether it is colorless and transparent, whether there is foreign matter, whether there is color difference of the material, etc.;

2. Bonding performance: whether the bonding performance of the product laminating surface is good;

3. Matching of lamination process: select the appropriate optical adhesive according to the equipment and process;

4. Advantages and disadvantages of weather resistance and yellowing resistance: compare the changes of optical adhesive products before and after aging, bonding strength, light transmittance and yellowing index;

5. Repairable performance: whether the overflowing glue is easy to clean and rework;

6. Storage stability of products: pay attention to storage conditions and shelf life;

7. Environmental performance requirements: preferably low VOC and low toxicity products.

In addition to the selection of optical glue, there are also many matters that need to be paid attention to in the use of optical glue, because it may need to go through different components mixing, dispensing, deaeration and curing process links in the process of use, and the precautions for use are briefly described as follows:

During the storage and use of UV-cured OCR glue, it should be protected from light, especially the light band that can be cured, so as to avoid gel curing; For two-component OCR, when mixing, it is necessary to accurately measure according to the ratio requirements and ensure uniform mixing; Thermosetting OCR needs to pay attention to the mixing process, the temperature of the glue itself and the temperature and humidity of the environment need to be controlled to avoid curing due to excessive temperature, and excessive humidity to make the glue fail; In the process of lamination, deaeration and other process operations, OCR glue should pay attention to the correlation between the environmental conditions of the glue and the curing conditions of the glue, so as to avoid problems such as exceeding the operation time, gel curing, and blocking equipment pipelines during use; UV-cured OCR needs to ensure that the energy of UV light exposure is sufficient; Thermoset OCR needs to meet the temperature and time required for curing to ensure complete curing; During the use of OCR glue, attention should be paid to all materials that are in direct contact with the glue, and must not contain related substances that can poison the catalyst, otherwise OCR will not be cured or incompletely cured.

Silicone liquid OCR glue has strong versatility, good gap filling, suitable for the bonding of various sizes of products, curved surfaces and complex surfaces, can be suitable for the bonding of a variety of transparent optical materials, such as PMMA, PC, PET, glass, LCD and TP and other related electro-optical materials bonding, can effectively ensure the product display effect and brightness, and has excellent durability and bonding effect, widely used in intelligent vehicle display terminals, education electronic whiteboards, conference intelligent interactive terminals, gaming display screens, Public advertising screens and other fields.

With the rapid development of display technology, as well as the development of flexible screens and large-size screens, the differentiation of terminal application products is becoming more and more obvious, and customized products will be the future development trend. Liquid OCR because of its liquid flow state, with strong applicability, good gap filling, suitable for a variety of different shapes, sizes and complex structure of products, bubbles easy to remove, high bonding yield and other advantages, in the application of large size, curved lamination, special-shaped products has obvious advantages, will be one of the future development trends, with small curing shrinkage, weather resistance and yellowing resistance and other excellent comprehensive properties of low VOC, non-toxic, environmentally friendly silicone OCR will have a broad market development space and application prospects.