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Light curing sensitizers

Light curing resins are synthetic resins that chemically change from liquid to solid as a polymerization reaction is started when irradiated with light of a specific wavelength. While they have been used for plate making such as screen printing for a long time, they are still used today in a wide range of applications, including adhesives for electronic materials, resist inks, gel nails, and UV resins for handcraft. The most familiar example of the use of light curing resin is in dental treatment. It is popularly used nowadays to fill teeth that are cut to remove dental cavities, since it can be cured in a short period of approximately 20 seconds by ultraviolet irradiation. In general, curing is done under ultraviolet light (UV) with a wavelength of 200 to 400 nm, but the use of LEDs as light sources has attracted attention in recent years due to their advantages that include longer life, lower operating costs, and lower power consumption. However, it is possible that the mixtures that used to cure under UV will not solidify as expected when UV-LEDs, which have shorter wavelength bands, are used. With this being one of the impacting factors, thiol sensitizers that can cure the resins at a lower energy are attracting renewed attention.

Application example

  • Adhesives for electronic materials
  • resist Ink
  • Chain transfer agents
  • Crosslinking agent
  • dental Materials
  • UV resin for handcraft

Sensitization

The use of a thiol as a sensitizer in light curing resins improves the double-bond reaction rate, rather than curing without it. In addition, the rate of improvement increases as the amount added is larger. This is ascribed to the sensitization effect and the effect of suppressing oxygen inhibition by thiol addition. Measure the machine:Real-Time FT-IR
measurement conditions:room temperature,Air atmosphere
UV lamp radiation value E(abs): 100[mW/cm2]
  • monomer

    Trimethylolpropane triacrylate 100parts

  • initiator

    1-Hydroxycyclohexylphenylketone 2parts

  • sensitizer

    TMMP, PEMP, DPMP 0~10parts

Oxygen inhibition restraint

When thiol was used as a sensitizer for a light curing resin, the thin film was completely cured in air without oxygen inhibition, regardless of the olefin species of acrylate and allyl ether. When thiol was not used, curing was inhibited by diffusion of oxygen from the air, and the resin did not cure at all under UV irradiation for 1 minute in the air. Surface tackiness caused by insufficient curing remained even after UV irradiation for 10 minutes.

atmosphere
Air
N2
thiols
Addition
Addition
No addition
No addition
No addition
Olefinic acid
Allyl Ether
Acrylate
Acrylate
Acrylate
Acrylate
UV irradiation
1min.
10min.
1min.
Surface condition

Completely curing

Completely curing

insufficient curing

insufficient curing(Sticky)

Completely curing

film thickness:5μm UV lamp radiation value E(abs): 2 [mW/cm2] thiols:PEMP

Improved adhesion

By adding thiol as a sensitizer to a light curing resin, tensile shear adhesion strength was improved 2 to 3-fold compared to that without the addition of thiol.
Measure the machine:Autograph(Tensile shear adhesion strength)
test method:Compliant with JIS K6850:1999
Adhesive substrate:PMMA
  • monomer

    Trimethylolpropane triacrylate 100parts

  • initiator

    1-Hydroxycyclohexylphenylketone 2parts

  • sensitizer

    TMMP, PEMP, DPMP 5parts

Line up

Product

Product
Structural formula

Viscosity
(mPa・s) [25℃]

TMMP
TMMP-LV
TMMP-HS
150
PEMP
PEMP-LV
PEMP-HS
510
DPMP
2800
TEMPIC
600
EGMP-4
50
BDMP
55
Multhiol Y-2
64
Multhiol Y-3
100
Multhiol Y-4
150
PXDT

<10
(50℃)

The values shown above are typical values,not guranteed values.

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