Teikoku Printing Inks Mfg. Co., Ltd.

Technical Topics No.125

Q&A about adhesion in FIM/IMD

In response to questions about the adhesion between the printed ink and the injected resin, the following schematic is provided. This schematic shows the test method of the adhesion between the printed sheet and the injected resin. Also provided below is a summary of Frequently Asked Questions (FAQs) about the FIM/IMD process.

1. Test method of the adhesion between printed film and injected resin.

(1A) Test specimen preparation
A printed sheet is inserted into a mold for the test panel and then insert molding will be done.

(1B) Adhesion test.
Cut 10mm width strip in the specimen and pull it out to peel it from the specimen at a 180 degree angle using Tensilon at 300mm/min. speed.

2. FAQs

Topic 1: Binder

Q1.	What is a "binder?"
A1.	A Binder is an adhesive that enhances the adhesion between a 2pack ink and an injected resin. Teikoku offers two types of binders. IMB 009 is suitable to MIR Mirror inks. IMB 003 is for 2pack inks and contains safer solvents.

Q2.	Why is a binder needed when using 2pack printing ink?
A2.	2pack inks generally make a highly-bridged hard surface which would not be softened by the injection heat. As a result, it will not adhere to the injected resin. To remedy this, Teikoku offers binders which easily adhere to both the printed ink surface and the injected resin.

Q3.	What is the difference between IMB 009 Binder and IMB 003 Binder?
A3.	IMB 009 Binder is for mirror inks. When it will be printed on the overprinting ink layer on the backside of mirror ink, it will not harm the mirror effect. It has excellent heat resistance and is very stable under the heat conditions of injection molding. IMB 003 has good adhesion to a wide variety of injected resins such as PC, PC/ABS, ABS, PMMA, AS, etc.

Topic 2: Adhesion

Q4.	Why, when the ink sheet is peeled from the injected resin, does some ink remain--sometimes on one side or other times on both sides?
A4.	When ink remains only on printed sheet, adhesion between the injected resin and the binder is not strong enough. If there is ink only on the injected resin, adhesion between the printed sheet and the binder is not strong enough. If you can see ink on both sides, the binder adheres to both the printed sheet and the injected resin but the binder layer itself was destroyed. It is a cohesion failure.

Q5.	Why does the printed sheet peel off from the injected resin?
A5.	It may be because of the mismatching of injection resin printed ink layer and the binder. Please contact the Teikoku rep.

If you have been operating without any problem and suddenly peeling has occurred, please check following points:

(1)	Thickness of the binder:
	When the binder becomes very thin, binding will be decreased. T200-250 mesh and 7-15 micron dry thickness is standard.

(2)	Drying conditions of the binder:
	If the binder is not dried completely, the strength of the ink layer will be lessened and may cause a cohesion failure.

(3)	Additives:
	If any additives such as defoamer were added, this may cause insufficient adhesion.

(4)	Temperature of injection resin:
	If the temperature of the injected resin is not high enough, the ink layer and/or binder may not melt easily and cause a malfunction. The temperature of the injection resin and the mold should be set at a higher level.

For additional help with printing and molding conditions and shape of products, please contact the Teikoku rep.