Hard coat vs Scratch coat

[LKahn]

A hard coat and a scratch coat are two entirely different coatings. How do you describe the difference?

[Chris Ryser]

A hard coat and a scratch coat are two entirely different coatings. How do you describe the difference?

There is no such thing in the books as a scratch coat which is actually slang for " Scratch resistant coating"

A hard coat is made from a resin applied on the surface of a substrate, either by spinning or dipping and the cured by polymerisation, which is initialized either by heat (thermocure) or by a high intensity UV light that has a peak around 365nm (UV cure). It either bonds to substrate mechanically or chemically (primer, depending on substrate materials).

The resulting layer will have a harder surface than the original substrate and depending of the resulting hardness will be less prone to scatching.
This type of coating can be tested and classified according to standard test's.

Scratch Resistant Coatings can vary from one to another company offering them. Some of them are air dryable varnishes and others are made with polysiloxanes (silicon). This type of coatings will not withstand standard testing and have to be used according to manufacturers instructions.
Their efficiency can be from good to bad and should be checked carefully against claims made by their vendors.

[LKahn]

I have a technical definition.
I looking for a non-technical description, the way most people describe these two difference finished.

Also, as a note, technically, a Hard Coat protects against penetration. A Scratch Resistant coating protects against abrasion. These are often confused. The analogy is steel, hard to penetrate, but easy to scratch.

[Chris Ryser]

Also, as a note, technically, a Hard Coat protects against penetration

Penetration of what....................? :bbg:

[LKahn]

Often a Hard Coat is necessary for some plastic substrates such as polycarbonate to pass the drop ball test. Additionally, the Hard Coat coating may exhibit properties of adhesion which is valuable when used in conjunction with other types of coatings such as AR. Often AR coatings have poor adhesion and the Hard Coat is used as an intermediate layer or primer. I put the question out to the community to gather general responses. How do most describe a Hard Coat?

[Aarlan]

Funny, I've always used the terms interchangeably.

AA

[sharpstick777]

For most of us, the terms mean exactly the same thing. Everything now is determined by the AR you use, and hard coating is included with any decent AR process. Most labs spin coat the lens so they use pre hardcoated blanks (most progressives are pre-hardcoated), surface the back and then spin coat it the back only.

A few labs dip coat the lenses, but first strip the existing manufactures hard coat, then dip, then AR.

The other difference is that some hard coats are NOT tintable, and some are, but you don't have as good of durability.

[Robert Martellaro]

Often a Hard Coat is necessary for some plastic substrates such as polycarbonate to pass the drop ball test. Additionally, the Hard Coat coating may exhibit properties of adhesion which is valuable when used in conjunction with other types of coatings such as AR. Often AR coatings have poor adhesion and the Hard Coat is used as an intermediate layer or primer. I put the question out to the community to gather general responses. How do most describe a Hard Coat?

Cushion or primer coat. The hardcoat provides abrasion and scratch resistance and other capabilities.

Scroll down to page 14.

http://www.bimas.lt/akys/literatura/lesiai_dangos.pdf