Products and equipment for photopolymer stamp making

Rubber stamps are mainly used for administrative applications, as a   signature of a company, administration, commercial entity or individual. However other kind of stamps are available, such as daters specifically used to date documents or numberers to affix numbers on document series.

In France, company stamp  is required to process most documents such as contracts, quotes or delivery notes.  Signature is generally made next to or on the company stamp, with date.

Stamp is also widely used in scrapbooking applications, to customize creations : cards, announcements, albums, Christmas cards, birthdays… Multiple accessories are available for using rubber stamps in a different way : embossing powder, multi-color ink, metallic inks ...

Finally, stamps are also used in specific applications: outdoor use with UV inks, tracking information (for instance  ampoules,  with acid inks), textile marking for  clothes…

Historically, texts were arranged and images were engraved by typographic workers then gathered together  and tightened inside a forme. Then a matrix made of wax and other materials was placed on top and the whole  was placed inside a heating press to imprim patterns inside softened wax.

After cooling, the wax mold was covered with rubber and parchment paper  and placed again in the heating press so  that rubber can flow inside mold depth and produce relief for stamps. The resulting rubber sheet was cut into stamps.

Development of computers allowed to give up cumbersome manufacturing tools (lead character fonts, presses..) and use computer-aided publication and photosensitive polymers

Now, stamp manufacturing process consists of several easy steps:
-  patterns to be reproduced are drawn on a computer
-  a film is printed to get a negative
-  photopolymer  liquid resin is exposed through the negative to get a photopolymer stamp, or hard photopolymer plate is exposed to produce a cliche

- photopolymer cliche is pressed into a matrix board to get a mold for rubber (rubber stamps) or premix gel (pre inked stamps) moulding
 

In case of rubber stamps, two manufacturing solutions are possible : laser engraved rubber or rubber molded in a matrix board. These two techniques are to be compared to photopolymer resin technique

Photopolymer liquid advantages

• faster processing  (25  -30 minutes).
• a single small sized machine necessary
• very low  equipment depreciation therefore low stamp cost price

Photopolymer liquid drawbacks

• ink restitution not so good  (polymer closed structure)
• resistance not so good over time
• resistance to alcohol-based inks not so good

Laser/conventional rubber advantages

• better resistance to inks (especially alcohol-based ones).
• more resistant over time
• better ink restitution  (rubber por
• choice of colors, nobler material.

Laser engraved rubber advantages

• Fast processing  (3 minutes 30 s) for a single stamp with a laser engraver

Conventional rubber advantages

• lower equipment cost, compared to laser
• Cost for  additional copies of a same stamp is very low and processing very fast : once the mold (with patterns in hollow) is obtained, only rubber is necessary and fast vulcanized.

Laser engraved rubber drawbacks

• high investment cost (laser engraver)
• long engraving time (2 hours 40 for A4 size, including  40 stamps, with a 30 w machine) that can be reduced using a  higher power laser tube.
• important maintenance :  90 % of rubber material need to be removed and release a lot of dust that dirty the machine.
• same work and same cost for additional copies of a same stamp

Conventional rubber drawbacks :

• longer processing time for the first  copy  (1 hour  10  for a 40 stamp A4 size)

Production of photopolymer stamps is very easy and does not require important equipment.

Once a positive film is printed  (laser or inkjet printer), all other operations are made in the same Thermogravor machine including  3 parts: exposure, engraving, drying.

Negative film is processed in the exposure part of the machine, then developed and fixed in trays

Liquid resin is

     - exposed  in the  exposure part of the machine

     - washed out in the engraving part of the machine

     - post exposed  in the exposure part of the machine

    -  dried in the drying part of the machine.

Space-saving, easy to use and designed by Thermoflan, Thermogravor  machine  allows the manufacture of photopolymer stamps up to A4 format.

Characteristics of 3 stamp types are summarized in the table below:

As a result:

Photopolymer stamps require low investment; their production is relatively economical and fast.

Conventional rubber stamps are interesting for large volume and additional copies of a same stamp (scrapbooking for instance)

Laser speed is interesting for small quantities, larger quantities requiring significant investment (100 w power). Also, it is important not to forget laser maintenance cost.

Thermoflex 50 v resin: with the help of ANVAR (French agency for research valuation)  and  National School of Chemistry of Montpellier, we have developed a photopolymer resin for  direct stamp production. Available in different hardnesses, our resin has a quality / price advantage never offered in stamp making

Advantages of our resin are :

Working conditions :
Thermoflex 50 V does not require  the St Andrew’s  cross on the label. This simply means  that this is a much safer product to work with.

Odor :
Thermoflex 50 V is an odourless liquid photopolymer.

Engraving / Water washable  :
Thermoflex 50 V can be easily  washed out with  compatible wash out detergent solution.

Adhesion :Thermoflex 50 V  adheres well to the backing film.

Tackfree :
Thermoflex 50 V has no tackiness

Ink transfer and image definition:

Elasticity of the polymer  improves the image definition. Thermoflex 50 V is more elastic and can produce sharp, clear prints.

Longer life  :
Due to proper hardness and flexibility,  photopolymer plate has a longer  press life  and the plates  have a higher resistance to abrasion

Wick effect :
Unlike most resins on the market,  Thermoflex 50 V  resin does not absorb aqueous parts of ink. As a result there is no risk for ink pads to dry faster then expected. 

Resistance to UV light  :
UV does not alter  Thermoflex 50 V resin 

Appearence :

Thermoflex 50 V is  a green, transparent photopolymer material