Products & Solutions

Structure of color resist

What is color resist?

Color resist is a kind of colorant based ink used in  color filters. It is called color “resist” for its resistance towards chemical and physical applications during the manufacturing process. Color resist is also known as resist ink.

Image of RGB pattern of color filter
Color resist consists of colorants (pigments or dyes), polymers, photosensitive materials and solvents. When the ink is exposed to ultraviolet (UV) light, the exposed area becomes insoluble and can resist the etching process. Adding such properties to the ink is a crucial step in manufacturing a color filter

A color filter consists of a glass substrate coated by three types of color resist (RGB; red, green and blue) in a specific pattern. Since each spot of color resist (sub pixel) is very small, it is difficult to color each dot one by one.

Here, the color resist property proves useful. By applying color resist to the entire surface, masking the areas to be removed, and exposing the desired portions to ultraviolet light for curing (insolubilization), it is possible to selectively retain color resist in specific areas after etching with a developing solution. This process allows for obtaining RGB patterns on the glass substrate. (This kind of color resist is called a negative resist.)

Image of color resist patterning

Ingredients of color resist

Color resist is manufactured by mixing the mill base, which consists of colorants, resin and solvent, with a photo initiator and various additives for UV triggered polymerization.

Ingredients color resist and their functions
Ingredients of color resist Functions
Colorant ■Determines spectroscopic character.
Normally, a mixture of two or more colorants (Main colorant & toning colorant) is used.
Resin ■Gives dispersion stability when absorbed onto pigment surface.
■Gives adherence towards the glass substrate.
■Gives alkali developability.
Solvent ■Adjusts viscosity and dryness.
■Gives coating suitability.
Monomer ■Gives insolubility via polymerization and cross-linking (photocurability).
Photo initiator ■Initiates polymerization reaction in the UV irradiated area (photocurability).
Dispersant ■Gives dispersion stability to colorant.
Additives ■Prevents coating defect (leveling agent, etc.)
■Gives preservation stability.

Our color resist

Image photo of workers at the production site
Our color filter materials for FPDs were developed using the nano-level dispersion technology of the artience group. This technology has been accumulated through the development of printing inks and coating materials. By sufficiently utilizing our strength of being able to develop and produce color resist as well as its ingredients (high-performance pigments), we are contributing to the improvement of color displays.

Refinement and dispersion technology of pigments

Color materials for electronics such as FPDs require a high transmission ratio of light. In order to achieve this, the technology to refine the pigment particles at nano-level is essential. With this technology, we are able to adjust the pigment size according to various applications.

TEM image of pigments with a particle size of 30 nm thanks to technology that makes the pigment ultra-fine.

Making pigment particles disperse uniformly is also essential to improve the transmission ratio. By processing the pigment surface, we are able to stabilize the uniformly dispersed state and avoid any precipitation. With this technology, we are able to provide highly functional color materials with good fluidity (which makes it easier to apply to a substrate) and high transmission, suited for use in electronics.

TEM image of pigments particles uniformly dispersed and stabilized in liquid

Development of new colorants (OPTLION™ GREEN)

OPTLION™ GREEN is a brand-new colorant developed by our company. Currently, we have 2 types, OPTLION™ GREEN 8880 and OPTLION™ GREEN 8890. By applying them to a color filter, the real beauty of nature can be reproduced more vividly and brightly. In addition, by applying OPTLION™ GREEN, the color gamut will be expanded and enhance the color reproduction performance of the display.

Images using OPTLION™ GREEN

Color gamut of OPTLION™ GREEN