Pressure-sensitive adhesive identification label

#This invention relates to a pressure-sensitive adhesive label for identification (ID label) which is free from a silicone component and has an antistatic function. More particularly, it pertains to a pressure-sensitive adhesive ID label that is useful for applications to a hard disk drive (HDD) and related components.

#According as HDDs increase the recording density, the floating height of a recording head above a recording disk has ever been decreasing to as small as about 40 nm, which cannot be seen as a “floating height” and is now called “pseudo-contact”. It is expected that “contact” supplants pseudo-contact in a few years. HDD and related components manufactures are challenged to perfectly protect an HDD from contamination with a volatile silicone component which can cause reliability problems, such as head crashes.

#Today, a pressure-sensitive adhesive ID label is stuck to an HDD and its components for furnishing product management information, such as the product number. Some pressure-sensitive adhesive labels contain a silicone compound in the pressure-sensitive adhesive of the pressure-sensitive adhesive layer, a release agent in the release liner protecting the pressure-sensitive adhesive layer, and the like. Even where the pressure-sensitive adhesive contains no silicone compound, the release liner, if its release side has been silicone treated, will contaminate the label (in particular, the pressure-sensitive adhesive layer) with the silicone compound. Where such a label is stuck to an HDD or its component, there is a very high possibility of the label allowing the volatile silicone component to enter the inside of the HDD.

#FIG. 1 is a schematic cross-section of an example of the pressure-sensitive adhesive ID label according to the invention.

#FIG. 2 is a schematic cross-section of another example of the pressure-sensitive adhesive ID label according to the invention.

#FIG. 3 is a schematic cross-section of still another example of the pressure-sensitive adhesive ID label according to the invention.

#The pressure-sensitive adhesive ID label of the invention fundamentally comprises a substrate having a printable surface on one side thereof, a pressure-sensitive adhesive layer provided on the other side of the substrate, and a conductive layer provided between the printable surface and the surface of the pressure-sensitive adhesive layer. The conductive layer is provided between the printable surface and the pressure-sensitive adhesive layer surface and therefore not exposed to the outside. Accordingly, the label maintains both the essential labeling functions of furnishing ID information and adhering to an object to be labeled and additionally exhibits an effective antistatic function ascribed to the conductive layer.

#It is important that the amount of the outgas from a volatile silicone component which generates on heating the pressure-sensitive adhesive label of the invention at 120° C. for 10 minutes is 5 ng/cm2 or less, preferably 1 ng/cm2 or less. As long as this volatile silicone component outgas is controlled to 5 ng/cm2 or lower, vaporization of a volatile silicone component from the label stuck to an HDD or its components can be seen as insubstantial, and the label will not cause corrosion or malfunction of the HDD or the components. If the outgas generated from a volatile silicone component on heating at 120° C. for 10 minutes exceeds 5 ng/cm2, vapor of a volatile silicone component from the label can seriously ruin long-term reliability of the HDD.

#The volatile silicone component outgas can be measured as follows. A given size of a specimen cut out of a pressure-sensitive adhesive ID label is weighed and then heated at 120° C. for 10 minutes in a purge-and-trap (P&T) head-space sampler (HSS) to cold-trap generated organosilicone gas (volatile silicone component) at −120° C. The trapped component is analyzed by gas chromatography/mass spectrometry (GC/MS). The amount of silicone compound-related gas generated on 120° C. heating (e.g., tri- to hexamers of cyclic silicones) is calculated based on n-decane standards and converted to the amount of volatile silicone component outgas per unit area (ng/cm2).