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Differentiator is touch panel design. Optical bonding technology for curved surfacesINGS SHINANO Co.,Ltd

2019.01.29

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Example of display screen using optical bonding technology for curved surfaces

Points to be noted

  • Support for manufacturing styling-based products with advanced technology
  • Handles processes up to attaching bare chips in addition to bonding the surfaces

In recent years, 2.5D curved surfaces are used for display screens of devices such as smartphones. A 2.5D curved surface generally refers to a surface that is curved to be semi-cylindrical. This shape can be seen on smartphones, digital home appliances, and touch panels on the dashboard of cars in front of the driver, and it is easier to visualize if the whole touch panel is imagined as having a curved shape instead of a semi-cylindrical shape.
Ings Shinano Inc is the company with the optical bonding technology for bonding the parts so that the functions of liquid crystal and touch panels work even in such curved parts.

The “Liquid crystal panel” (A part that displays the screen) and “Touch panel” (A device used to operate computers by directly touching the screen) include parts with special functions such as polarizing plates, and adhesives such as films and resins are used for bonding them. Since adhesive materials used in the screen area of the display directly affects the images displayed, it is required to be optically uniform and transparent.

The fundamental premise up to now was that “Liquid crystal panel” and “Touch panel” are planar. With the curved surfaces, problems such as distortion of images, difficulty in viewing, and differences in appearance of colors are likely to occur. Besides, bubbles may enter when bonding the adhesive materials. For curved surfaces to appear the same from any angle requires advanced technology.
The writer spoke to Mr. Shiratori to find out how the optical bonding technology for curved surfaces was developed.

He said that the use of curved surfaces is still limited in Japan, while its use in the touch panels around the driver seat of overseas cars is increasing. The reason is because of the increase in touch panel size due to the increase in functions such as screens with images for passengers, in addition to the speedometer and car navigation systems.
Curved styling is used for big flat surfaces that are simple in appearance, to make them appealing and for differentiation from other cars.

When the company was founded in 1946, their line of business was related to silkworms, but after 20 years of business, they shifted their business, and now have two pillars of business, modularization of liquid crystal panels and implementation of bare chips.
The company has been engaged in the business of liquid crystal panels for the past ten years. They got the opportunity after accepting an order for assembling liquid crystal panels in the clean room. They initially started with mass production, and after the order moved overseas because of price competition, they began to accept requests for prototype production in addition to large-scale production orders. Most of the orders for prototypes were new and challenging. The company gained expertise as a result of refining the technology to meet the demand.

Scope of support for the creation of display screens

Typically, there are two methods for bonding touch panels. OCA and OCR.
Optical Clear Adhesive (OCA) uses adhesive sheets for bonding. Optical Clear Resin (OCR) uses resin with UV effect and high viscosity, and the bonding process consists of pouring the resin on the bonded surface and then applying UV rays or heat to cure the resin for bonding. The method to be used is determined by the customers and depends on the ease of processing and the materials used.
The company offers both the methods and can handle post-processing in addition to the bonding. Post-processing includes installing back lights on the liquid crystal panel, mounting ICs, reducing the base size, and fixing polarizing plates to complete the liquid crystal panel.

The company deals with auto-ancillaries, medical equipment manufacturers, and manufacturers of liquid crystal panels such as LCD, and Organic Light Emitting Diode (OLED). Since there is an increase in the bonding requirements of curved surface films to the interior touch panels of cars as mentioned above, the company is expecting expansion in this field. Mr. Shiratori said, “We are looking to expand our business to companies that value styling for differentiation from other companies”.

Interview Date: December 27, 2018

 

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We carry out small volume production of semiconductor packaging and liquid crystal panel module mount assembly on contract basis and deal with trial manufacture of each. Please consult us for very small volumes as well.

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