uringand Bonding
Plastic clothespins left outside can become brittle and easy to break.
Most people have experienced this.
This is a result of the plastic being exposed to the ultraviolet (UV) rays of the sun.
Using the chemical energy of ultraviolet light, it is possible to change substancesat the molecular level and join them together.
That is the power of UV curing and bonding technology.

UV curing is what takes place when a specially formulated light-curable resin (photocurableresin) is irradiated with ultraviolet light at a wavelength of 200 to 400 nm (nanometers).The
history of UV curing is quite extensive, going back to the 1970s when it was developed as aprinting technology capable of speeding the drying of ink on materials such as metal and plastic.
The technology made it possible to obtain good printing results on such surfaces by mixing ink
with photocurable resin and irradiating the surface immediately after printing to instantly harden
the ink.

Ultraviolet instant curing equipment
UNICURE system
Main applications: LCD panels, touch
panels, electronic components, printing,etc.

Use subsequently spread to curing of paint and application of protective coatings to surfaces,and now UV curing technology is used to join together the delicate miniature components ofdevices that are not amenable to screw fastenings, such as televisions and Smartphones, as well
as joining elements that require high light transmissivity, such as camera lenses.

Light = Glue?!
Today, in order to further reduce the size of components, even the microns-thick application of
curable resin has been eliminated, as VUV joining technology is used to bond components ofdifferent composition together directly. This process irradiates substances with 172-nm vacuum
ultraviolet (VUV) to activate their surfaces and combine what were formerly objects of different
composition into a single substance. Truly, light is glue.

LCD panel bonding system
Main applications: Joining of LCD panels
used in devices such as televisions,
Smartphones and tablet PCs

This technology not only facilitates the miniaturization of objects, but also eliminates worries
about joined objects becoming separated — a particular concern with embedded medicaldevices — as well as concerns about gasification of resin bonding agents.
Joining objects together: It is a task that looks simple, but it is the optical technologies of UV
curing and VUV bonding that are essential to the further development of electronic products.

“Curing and bonding with light” The Mechanism
Matter is composed of molecules consisting of linked atoms, such as oxygen and hydrogen, carbon and nitrogen, and ultraviolet light is capableof breaking the bonds between such linked atoms. The bonds of molecules in photocurable resin are also broken by ultraviolet light, and thesmaller molecules that result seek out others with which to bond, resulting in molecules that are larger. (This process is referred to as aphotopolymerization reaction.) As a result, the structure of matter is altered (to high-molecular compounds) and its color and hardness changes.
■ UV curing
Photocurable resin

C

Light × curable resin = Curing and bonding

UV irradiation

Substance A

Substance A

Substance A

Substance B① Ultraviolet irradiation of special
resin (photocurable resin)

Substance B② Atomic bonds are broken andreformed

Substance B③ The result is instant hardeningof the formerly liquid resin.

⇒Liquid

Photopolymerization
reaction⇒Hardened■ VUV bonding
VUV irradiation
CH3CH3PDMS

OH

CH3Si O Si O Si(Polydimethylsiloxane)

OH

Glass

H 2O

OH

Glass

① Irradiation of material to bejoined with 172-nm VUV(vacuum ultraviolet)

OH

OH

OH

Si O Si O Si

PDMS

H 2O
OH
OH

OH

OH

OH

Glass

② Surface is altered and hydroxyl
groups are deposited

OH
OH

OH
OH

Si O Si O Si

PDMS

③ Water (H2O)
is released

H2 O

GlassOOOSi O Si O Si

PDMS

④ Joining