Manufacturing method for ultrathin white covering film

The present invention relates to a manufacturing method for an ultrathin white covering film for a printed circuit board.

As one of main raw materials of LED light bars, a white covering film has been widely applied. At present, the white covering film mainly has two manufacturing methods. The first method is to use a white polyimide film, coat a layer of adhesive on a surface of the white polyimide film and compound the white polyimide film with a release material. The other method is to use an ordinary yellow polyimide film, coat a layer of white ink on a surface of the ordinary yellow polyimide film, coat a layer of adhesive on another side of the yellow polyimide film and compound the yellow polyimide film with a release material.

However, since the price of the white polyimide film is very expensive, the white polyimide film is not often applied in a market. Most of users still select a method for coating a layer of white ink on the ordinary yellow polyimide film.

With the development of thinning of products, higher and higher requirements are also proposed for the thickness of the white covering film. The manufacturing method for the pure white polyimide film is difficult to satisfy this need currently because on one hand, the price is excessively expensive, and on the other hand, a covering property and other characteristics after the products become thinner are difficult to be realized simultaneously. However, the manufacturing method for coating a layer of white ink on the ordinary yellow polyimide film is also difficult to satisfy a thinning need because the thickness is difficult to be reduced due to existence of three layers such as a polyimide layer, an adhesive layer and a white ink layer in spite of low price.

The purpose of the present invention is to provide a manufacturing method for an ultrathin white covering film. Compared with an existing manufacturing method for coating a layer of white ink on an ordinary yellow polyimide film, the manufacturing method reduces a polyimide film, reduces a use part from three layers to two layers, can greatly reduce the thickness of a product, can also make an appearance of the product better, and greatly reduces the price relative to the manufacturing method for the pure white polyimide film.

The present invention is also suitable for ink of other colors except for white.

To solve the above technical problem, the present invention adopts the following technical solution to realize.

A new technical line for production of the white covering film is adopted: after white ink is coated on one side of a pressure sensitive adhesive of the protecting film, an adhesive is coated on an ink surface and compounded with a release material. Specific description is as follows.

The white ink and the adhesive used in the present invention can be prepared according to existing known preparation methods.

The white ink and the adhesive are prepared according to of formulation requirements as follows: stripping a release layer of the protecting film, coating ink on one side with the pressure sensitive adhesive, drying and solidifying through an oven, coiling, coating the adhesive on a surface of the ink, compounding a release material after drying and solidifying through the oven, coiling, controlling the curing to a needed adhesive overflow quantity, cutting according to a required width, inspecting the appearance, and packing and warehousing. A flow is as follows:

preparing the white ink and the adhesive→coating the white ink and drying→coating an adhesive and drying→compounding the release material and coiling→curing→cutting→inspecting the appearance→packing.

The white ink is an epoxy series, a polyacrylate series, a saturated polyester series or an organic silicon series, and is preferably polyester series ink. A thickness of the above white ink is 11 to 24 and preferably 8 to 15 μm. A drying condition of the above white ink is to achieve a drying effect of 1 to 3 min at 160° C. to 190° C., and preferably a drying effect of 2 min at 190° C.

The adhesive is an epoxy series, a polyacrylate series or a polyester series, and preferably the epoxy series. A thickness of the above adhesive is 10 to 25 μm. A drying condition of the above adhesive is to achieve a drying effect of 1 to 3 min at 150° C. to 170° C., and preferably to achieve a drying effect of 1.5 min at 160° C.

The protecting film is a high to temperature resistant protecting film. A base material used for the above protecting film is a high to temperature resistant polyester series. The pressure sensitive adhesive used for the above protecting film is a polyacrylate series, a polyurethane series or an organic silicon series, and preferably an organic silicon series adhesive. A stripping force between the pressure sensitive adhesive used for the above protecting film and the ink is 15 to 40 CN/5 cm, and preferably 15 to 25 CN/5 cm.

The release material is release paper or a release film, and preferably the release paper. A release force of the above release paper is 5 to 20 CN/5 cm, and preferably 8 to 15 CN/5 cm.

The present invention has the beneficial effects that: the white ink is coated on the surface of the protecting film and can form a film; meanwhile, a bonding force between the ink and the adhesive is strong enough; and sizes of the stripping force between the protecting film and the ink and the release force between the adhesive and the release material are appropriate for convenient operation, thereby achieving effects of reducing the thickness and the cost without using the polyimide film, protecting the surface of the ink by using the protecting film and also facilitating operation during use.

FIG. 1 is a diagram of manufacturing steps of a manufacturing method for an ultrathin white covering film in the present invention.

FIG. 2 is a structural diagram of an ultrathin white covering film in the present invention.

32 . adhesive layer; 33 . release material; 34 . white ink layer; and 35 . protecting film

The present invention is further described below in combination with embodiments.

Step S 101 : preparing the white ink and the adhesive: preparing according to existing preparation methods respectively.

Step S 102 : coating the white ink on the protecting film and drying to form a white ink layer ( 34 ): setting oven temperature of a coating machine (such as 80° C., 110° C., 140° C., 170° C., 190° C., 190° C., 160° C. and 120° C.; to dry the adhesive as far as possible, setting 190° C. as much as possible without influencing the appearance of the surface of the adhesive; setting drying time of 1.5 to 2 min), a speed (such as 8 to 12 m/min) and other parameters according to characteristics of the white ink; coating the surface of the pressure sensitive adhesive of the protecting film ( 35 ) to a needed thickness (such as 15 μm); drying through a drying tunnel; and coiling after generating a solidifying reaction, wherein a drying condition is to achieve a drying effect of 1 to 3 min at 160° C. to 190° C.

Step S 103 : coating the adhesive layer ( 32 ) on the white ink and drying to form a adhesive layer ( 34 ): setting oven temperature of a coating machine (such as 80° C., 110° C., 140° C., 160° C., 160° C., 160° C., 120° C. and 70° C.; to dry the adhesive as far as possible, setting 160° C. as much as possible without influencing the appearance of the surface of the adhesive; setting drying time of 1 to 1.5 min), a speed (such as 10 to 15 m/min), etc. according to characteristics of the adhesive (such as the epoxy series); coating the surface of the coated ink to a needed thickness (such as 15 μm); drying through a drying tunnel; and generating some solidifying reactions, wherein a drying condition is to achieve a drying effect of 1 to 3 min at 150° C. to 170° C.

Step S 104 : compounding the release material ( 33 ) on the adhesive layer ( 32 ) and coiling under certain compound temperature and compound pressure: compounding under a set temperature (such as 50° C. to 70° C.) and pressure (such as 147.1 to 294.1 KPa) and coiling.

Step S 105 : curing to obtain the ultrathin white covering film, wherein a curing procedure is to place the coiled material in an oven with a set temperature (preserving heat at 40° C. to 60° C. for 2 to 30 hr) to enable the adhesive to generate a reaction until an adhesive overflow quantity reaches a needed degree (such as 0.05 to 0.15 mm).

Then, cutting, inspection and packing are performed conventionally.

A cutting procedure is to cut the coiled material on a cutting machine to a needed width and cut off scraps.

An inspection procedure is to inspect the product appearance of the cut material on an inspection machine and remove products with bad appearances.

A packing procedure is to pack the qualified products after inspection according to packing requirements.

When the ultrathin white covering film manufactured by the present invention is used for FPC processing, operation is easy; the protecting film ( 35 ) can perform a good protection effect on the surface of the ink in an entire FPC flow; and finally the protecting film ( 35 ) is stripped off. Since no polyimide layer is used, an entire thickness is greatly reduced and an ultrathin purpose is achieved.

Remark 1: The ink is first coated on a carrier film and then the adhesive is coated on the surface of the ink for test.