It is generally believed that the bonding mechanism of optical lens is that the mechanical bonding, physical adsorption, electric attraction, mutual diffusion, chemical bond formation and other actions between optical materials and optical glue make the optical parts and optical glue produce bonding force to combine optical parts. The binding force is related to the adhesive material and lens material. What are the requirements for optical lens bonding materials in the manufacturing process? What are the common ones?

Requirements for optical lens gluing materials

The optical adhesive is mainly used for bonding between optical lenses. In order to ensure the bonding quality of optical lenses, the adhesive must meet the following requirements:

(1) Colorless and transparent, high transmittance, no fluorescence, similar to the refractive index of glued parts

(2) During curing, the volume shrinkage rate is small, and no internal stress is generated on the bonding surface

(3) With good mechanical strength, the rubber layer will not crack due to vibration and impact

(4) ) Good chemical stability, no chemical reaction with optical materials, and no deformation after long-term use

(5) Good environmental protection, non-toxic and harmless

(6) With good thermal stability, it can work within a temperature range of 70~70 ℃ without breaking the adhesive layer, degumming or causing dislocation of parts

(7) The gluing process is simple and easy to disassemble.

What are the common optical lens bonding materials?

The adhesives used in optical lens gluing mostly belong to organic macromolecular polymers, which can be roughly divided into four development stages: natural fir resin adhesive → epoxy resin adhesive → methanol adhesive → optical photosensitive adhesive. At present, the development of optical photosensitive adhesive is relatively rapid, and the commonly used brands are GBN-501, GGJ-1, GGJ-2, etc.

The natural fir resin adhesive has simple bonding process and poor high and low temperature performance, which often causes degumming, causing the lens center and prism angle to move, making the instrument lose the requirements of the original design.

The epoxy resin adhesive has small shrinkage and good optical image quality, but it has a long curing time, complex process, high toxicity and is easy to cause skin allergy, which restricts the mass production.

The technology of methanol adhesive bonding is complex, and the shrinkage of the adhesive is very large, which often leads to the deterioration of the image quality of optical parts. The aging resistance of the adhesive layer is poor, the use time is not long, and it is easy to change color or degumm, resulting in a decrease in light transmittance.

The photosensitive adhesive is easy to use and has high efficiency (it can be completely dried in about 12 minutes under ultraviolet light), small shrinkage, good image quality of optical lens, good aging resistance, unchanged color of the adhesive layer after long-term use, and the light transmittance is still not less than 90%. The brand GGJ-1 GBN-501 photosensitive adhesive is suitable for gluing lenses and prisms with automatic centering. GGJ-2 is extremely viscous and nearly solid, suitable for gluing optical parts in the center of instruments or by hand.

Inspection after optical lens gluing

The relative geometric position and optical properties of glued parts, such as eccentricity, image tilt, focal length, top focal length, image quality, resolution and aperture, can be inspected on special instruments. The adhesive layer and surface quality can be inspected visually or with the aid of a magnifying glass according to technical requirements. Attention shall be paid to the following matters during gluing: in the effective hole diameter of the gluing piece, the color of the glue layer shall be close to and colorless: the defect grade of the gluing piece shall be calculated according to the sum of the defects of the two gluing surfaces according to the drawings, and the defects of the non gluing surfaces shall be calculated separately for each surface. Other defects, such as glue opening, mildew, oil stain, etc., are not allowed to have non developing defects beyond the effective aperture.

The thickness difference of lens glue layer before and after gluing is generally measured by optical comparator. The center error of the glued lens shall be checked with a centering instrument. The angle of the glued prism shall be checked with a goniometer, a light tool, etc. The surface deformation of glued parts is caused by the internal stress caused by the adhesive layer solidification or temperature change. Generally, the surface accuracy of the glued parts before and after gluing is measured by interference method, and then the deformation caused by gluing is calculated according to the distortion of the relevant patterns; The resolution or star point inspection can also be performed on the glued parts; It can also be tested by learning transfer function instrument. The focal length of the glued lens is usually measured with a light tool holder or a focal length meter. For the glued layer of the glued parts, interference fringes are allowed to be seen under reflected light. In addition, for the trial production of new products, shear strength, earthquake resistance and high and low temperature resistance tests should also be carried out.