Pressure sensitive adhesive contains a radiation-sensitive acrylic polymer

Pressure-sensitive adhesives (often referred to simply as “PSA”) and the method of polymerizing compositions to prepare pressure-sensitive adhesives are known from the prior art. For example, Us Patent No.4,181,752(Martens et al.) discloses a one-step US patent for the preparation of a standard viscous pressure-sensitive adhesive by irradiating a polymerizable substance containing a radiation-sensitive acrylate at an integrated flux rate of approximately 0.1-7 mW/cm ‘in the near-UV region No.6,174,931B1(Moon et al.) discloses a multistage radiation method for the preparation of acrylic series compositions such as adhesives or pressure-sensitive tapes.

The first phase of radiation is electromagnetic radiation at a lower integral flux rate (i.e. 0.1-20 mW/cm ‘) to allow the monomer to undergo a lower degree of conversion, and in the next phase, electromagnetic radiation at a higher integral flux rate (i.e., greater than 20 mW/cm2) to allow the monomer to undergo basically complete photopolymerization. Us Patent No.6.040,352 discloses a method for preparing an adhesive composition that consists of irradiating a free radical polymerizable composition under a monochromic radiation source with spectral output peaks in the wavelength region of approximately 250 to 600mm.

Uv radiation with low integrated flux rates (e.g., about 0.1-20 mW/cm) can be used to form high molecular weight acrylate polymers, which are particularly useful as pressure-sensitive adhesives with high-performance properties (e.g., high static shear strength). However, even after a long time of radiation, a small amount of unpolymerized material remains in general polymerized materials, which are not suitable for some applications. Therefore, there is still a need to improve the method of polymerization of compositions to prepare pressure-sensitive adhesives.

We need to provide a method that can achieve a higher degree of polymerization (i.e., a higher degree of transformation) in significantly less time without sacrificing physical properties than previously known techniques using a single light source or combination of light sources. Surprisingly, it has been found that, in practice with the present invention, the second light source preferably has emission wavelengths mostly in the region of about 200-280nm, although there is evidence that such light sources alone do not produce high-performance pressure-sensitive adhesives.