Transparent cover
A transparent cover is a pocket that is usually made of plastic film ("transparent film") and is closed on two or three sides to protect documents . Common forms are double-sided closed envelopes without a binding margin and three-sided closed envelopes with binding margins for use in ring binders or files . The envelope closed on three sides with perforation on the left edge is also known as a brochure envelope , the unperforated version as a file envelope or transparent envelope . The entrepreneur and inventor and former tax consultant Heinz Ball developed both versions in Bonn in the 1950s and had them produced and sold by NOVO-Organizationsmittel GmbH , which he runs.
Brochure covers are provided with different perforations (such as 4-hole or 11-hole) so that they can be stored not only in folders and loose-leaf binders with two aligning pins or strapping, but also in prospectus albums with multi-ring mechanisms. In addition, there are display books for differently extensive contents in which transparent sleeves are firmly welded in the back.
There are also so-called ID card holders or card holders. In this form, the back is extended and reinforced at the top and in this reinforcement (strip) there is then an elongated hole or a round hole to attach an ID clip.
They are made from transparent, clear or colored films made of PVC or PP . PP covers are indelible, the toner copies or prints contained are not affected by plasticizers in the material. The materials used are grained (mostly for PP covers) or smooth, the latter slightly milky or crystal clear. The standard film thicknesses are in the range from 40 µm (low stress resistance) to 200 µm (for high requirements).
Transparent envelopes are available for the common DIN / ISO 216 paper formats (especially A4, less often A2, A3 and A5) but also in special dimensions (for small-image negative strips, photos, business cards or CDs). Perforations are based on the ISO 838 standard (and its four-hole extension known as "888"). In recent years, however, the so-called euro perforation has become more and more popular in Europe, as this perforation can be used for almost all types of mechanisms or in most countries in Europe.
Transparent covers are also made for use outside the home, which serve as protection against the elements (rain, moisture) and dirt. Such covers are used for maps, for example, but also for mobile data acquisition and communication devices.
Smooth vs. matt / grained / glare-free
In principle, a distinction is made between smooth and grained shells , depending on the surface structure (smoothness vs. roughness). The smooth transparent covers have an almost perfectly smooth and therefore shiny surface that reflects the incident light, similar to normal window glass . The grained covers - also known as glare-free -, on the other hand, have a rough, microscopically wavy , and therefore matt surface that scatters the incident light, similar to matt glass for picture frames . (Compare the use of matt , glare-free , low-reflection or anti-reflective on computer screens .)
Crystal clear vs. colored (milky)
Furthermore, smooth or matt covers (features of the surface structure ) can be either crystal clear, milky or colored. The crystal clear cases are similar to the typical window glass provided with any color or color cast. The milky shells are made of a slightly whitish colored plastic - easily recognizable with the naked eye . There are also clear plastic folders, the yellow, pink and orange colored are. Despite the shimmer of color, these are completely transparent for a text printed on white paper with black ink .
Individual evidence
- ↑ From transparent sleeves to high-tech plastic in: General-Anzeiger , March 12, 2005.
- ↑ Novo celebrates its 110th anniversary in: Print & Production , July 25, 2011.