UA119707C2 - METHOD OF MANUFACTURING OPTICAL DIFFUSER - Google Patents

Abstract

The invention relates to optoelectronics, in particular to methods of manufacturing an optical diffuser. Optical diffusers are widely used in liquid crystal displays, projection systems and other devices where there is a need to form a lighting beam with specified parameters. Optical diffusers can also be used in tracking systems for moving objects. A method of manufacturing an optical diffuser in the form of a relief microstructure, according to the invention, includes applying a carbide conical indenter with an angle at the apex (120… 160) o conical recesses on a metal substrate, which is further used as a stamp for thermopressing embossed microstructure in the form of conical projections polymeric material. The present invention allows to provide high light transmission and reduce the proportion of scattered light in optical diffusers while ensuring quality and high repeatability of the optical diffuser by manufacturing them in the form of embossed microstructure with different predetermined angles of deflection of scattered radiation and radiation. 1

Description

relief microstructure with different predetermined angles of deflection of scattered radiation and with different placement of depressions on the metal substrate.

The invention relates to optoelectronics, in particular to methods of manufacturing an optical diffuser. Optical diffusers are widely used in liquid crystal displays, projection systems and in other devices where there is a need to form a lighting beam with specified parameters. Optical diffusers can also be used in tracking systems for moving objects.

Today, methods based on the holographic creation of diffraction gratings, methods using microspheres placed in a polymer matrix, and methods of forming 3D structures based on halftone lithography are used for the manufacture of optical diffusers.

The inventor knows many similar solutions for manufacturing an optical diffuser, among which the following are the closest in terms of essential characteristics.

There is a known method of manufacturing an optical diffuser, in which the use of holographic structures in the form of diffraction gratings is proposed for the manufacture of an optical diffuser ("Creation of optical diffusers on silver halide photographic materials with the help of multiplex holograms", N.M. Ganzherly, S.N. Gulyaev, I.A. Maurer, D.F. Chernykh. Journal of technical physics, 2014, volume 84, issue 12). In order for the hologram to scatter the incident radiation in a three-dimensional physical angle, it is necessary that its structure be more complex, consisting of many diffraction gratings oriented at different angles in the hologram plane.

The indicated method consisted in the fact that a thin amplitude multiplex hologram was created as a result of the interference of two flat beams on a photographic plate at a given angle by M/2 identical exposures, between which the photographic plate was turned by a small fixed angle around the normal to its surface, the value of which determined the number of plane waves M. After processing the multiplex hologram, it was a collection of many amplitude gratings rotated relative to each other. To obtain a usable optical diffuser, it is necessary to convert the amplitude hologram-diffuser into a highly efficient relief-phase structure. As a result of the photochemical processing of the hologram, the silver image was completely removed from the photoemulsion, which leads to the formation of a purely relief-phase structure of the holograms. When illuminating a multiplex hologram, each of the elementary gratings created beams of the 1st order, which in the Fourier plane of the lens gathered into a ring filled with luminous points.

The disadvantage of the proposed method is that the optical properties of phase holograms-diffusers depend significantly on the nonlinear transformation of the amplitude structure to the phase structure.

In addition, the optical diffuser is made of soft polymer material, which complicates its operation. Optical diffusers with a certain set of characteristics for use in specific systems can be manufactured by the holographic method.

In some technical devices, optical diffusers are required, which disperse the light flux to small angles (10-20)7 without significantly reducing the light transmission coefficient of the optical system (A.V. Dmitriev, A.V. Mvanov, A.R. Khokhlov, Numerical propagation modeling of light through a diffuser. Fundamental and Applied Mathematics, 2009.

Vol. 15, Mo. 6. pp. 33-41). As a rule, the designs of such diffusers are based on the use of microspheres placed in a polymer matrix, which scatter the light stream at the required angle.

The disadvantage of this analogue is that one or more layers of material transparent to the used spectrum range can be used, and each of the layers contains the specified microscopic particles of another substance.

Some of the shortcomings are eliminated in the known method of manufacturing optical diffusers, which is taken as a prototype (patent 05 6410213, published on 06/25/2002). According to the specified patent, a photosensitive layer deposited on a substrate of optically transparent material is exposed with focused laser radiation, followed by selective etching of the photosensitive layer, during which non-irradiated areas are removed. A relief-phase structure is formed on the substrate, which directs the incident light into a ring located at a certain angle. According to the link per:/Lumly.grorpogopisz5.sot/epdipeegea-aitivegv-iptoptaiyop/ (Epaipeeted Riyizeg5) the principle of operation of an optical diffuser with an artificially formed ZO relief-phase structure is schematically presented in the first image.

The disadvantage of the proposed method of the prototype is that the relief-phase structure of the diffuser is made of a soft polymer material placed on an optically transparent substrate. It is possible to make a metal stamp from a polymer original with the subsequent production of copies on an optically transparent material (polycarbonate, polymethyl methacrylate).

The invention is based on the task of ensuring high light transmission and 60 reducing the proportion of unscattered light in optical diffusers while simultaneously ensuring the quality and high repeatability of optical diffuser characteristics by manufacturing them in the form of a relief microstructure with different predetermined angles of deflection of scattered radiation and with different placement of depressions on metal substrate.

The problem is solved by the fact that the method of manufacturing an optical diffuser in the form of a relief microstructure, according to the invention, includes applying a carbide conical indenter with an angle at the top of (120...160)7 conical depressions on a metal substrate, which is later used as a stamp for thermopressing a relief microstructures in the form of conical protrusions on an optically transparent polymer material.

At the same time, the distance between the centers of adjacent recesses with a diameter of Ю can be from

Oya0.050 to Yu0.50.

At the same time, the application of conical recesses can be carried out with an indenter with a surface roughness not worse than K2 0.80.

The following cause-and-effect relationship exists between the set of essential features of the invention and the technical result that is achieved.

In the process of research, the inventors determined that in order to improve the operational characteristics and manufacturability of manufacturing the optical diffuser, it is manufactured in the form of a relief microstructure with specified characteristics. In particular, according to one of the features of the invention, the method includes applying a carbide conical indenter with an angle at the top (120...160)7" of conical depressions on a metal substrate, which is later used as a stamp for thermopressing a relief microstructure in the form of conical protrusions on an optically transparent polymer material. The conical shape of the recesses on the stamp allows for the subsequent formation of conical protrusions on the diffuser, which ensure the uniform distribution of the intensity of the deflected light in the annular zone (the annular zone is each section of the optical system, which is 4 distances from its axis). Deviation from the conical shape leads to an increase in the share of light scattered at random angles and an uneven distribution of light intensity in the ring zone, to random scattering and a decrease in transmittance.

The use of optically transparent polymer material allows to ensure the operation of the optical diffuser, as it is characterized by the necessary physical and chemical characteristics and is able to acquire a given shape after processing.

The inventors also established during the creation of experimental samples that the angle of the indenter determines the angle of scattered (deflected) light, that is, the angle of deflection of optical radiation by the diffuser. In the course of research, it was established that in order to ensure the optimum deflection angle of the diffuser, the angle at the top of the indenter should be in the range (120...160)7, which will ensure the deflection angle of the optical radiation by the diffuser is only within 5...10".

The inventors also established that in order to obtain a diffuser that deflects the maximum amount of light into a ring (each section of the optical system, distant from its axis at a distance of 4 (annular zone), gives an image of a light point in the form of a ring), conical elements must occupy the maximum area on the substrate surface. It is not possible to place the depressions too close due to the deformation of the neighboring conical depressions. In the process of research, it was found that the optimal distance between the centers of the depressions is the range from О-0.050 to ря0.50. The table shows data on the influence of the placement of conical recesses on the efficiency of the manufactured diffusers.

Table 1

Dependence of the fraction of scattered light on the distance between the centers of recesses of recesses of light 7 o030 | 7777780

According to the table, placing recesses at a greater distance than the specified range leads to a significant increase in the proportion of unscattered light, which reduces the efficiency of the optical diffuser. Placing recesses at a shorter distance can lead to deformation of the shape of the adjacent recess, which in turn leads to an uneven distribution of intensity after the diffuser.

In the course of research, conical depressions were created on the substrate, which was then used as a stamp for the manufacture of diffusers on a transparent polymer material.

The material of the stamp must be plastic at the same time so that it is possible to create conical depressions on it with a hard alloy indenter and ensure the production of a large number of copies. Obtaining the necessary number of copies is possible only with the use of a stamp, the melting point of which material is significantly higher, by 300-500", than the melting point of the material from which the diffusers are made. Such requirements for the material of the stamp are met by metals with a Brinell hardness of 24...40 kgf /mm". Thus, the substrate for the manufacture of diffusers must be metal to ensure the necessary performance characteristics. Only the correct selection of the material of the metal stamp makes it possible to obtain diffusers with defined light-technical characteristics. Obtaining indentations on the die with a mirror-like metal surface is a necessary condition for obtaining diffusers that scatter light in a narrow predetermined angle with a minimal fraction of scattered light at arbitrary angles.

It is known that the quality of the surface of the cones, on which light is scattered, has the greatest influence on the quality of diffusers. When light is scattered by cones with a mirror surface, the deflection occurs at a certain angle, determined by the angle of the conical protrusions. The presence of scratches on the surface of the cones leads to the appearance of light streams deflected at random angles.

The part of randomly scattered light, depending on the quality of the indenter processing, can vary from 2 to 15 95. Thus, in the research process, it was established that the indenter should have a certain surface roughness. In particular, the inventors established that the optimal surface roughness is a roughness no worse than K; 0.80. Surface roughness of the indenter

IN; 0.80 and less provides transparent optical roughness of polymers during thermopressing

From optical scattering elements. When the roughness of the indenter is greater than K; 0.80 during thermopressing, the surface of the conical scattering elements will be opaque and matte. The established roughness of the working surface of the indenter indicates that this working surface is polished, which allows the optical quality of the conical microrelief to be ensured during the manufacture of diffusers and, as a result, the least loss of the light flux when it passes through the diffuser.

The proposed method involves making conical depressions on a metal substrate with a carbide conical indenter. Making the indenter a hard alloy allows you to ensure a mirror surface of the indenter (with a roughness not worse than K;: 0.80), since the surface of hard alloys, for example, such as hard steel, can be polished to a mirror surface.

The drawings explain the essence of the invention.

In Fig. 1 shows the placement of conical recesses on the surface of the metal substrate (diameter 1.0 mm);

In Fig. 2 shows a view of the light-scattering surface formed on the surface of a substrate made of an optically transparent polymer material, in particular polycarbonate (the diameter of the conical protrusions is 1.0 mm).

Illustrative materials explaining the claimed invention, as well as given examples of a specific implementation of the method in no way limit the scope of claims set forth in the formula, but only explain the essence of the invention.

The method of manufacturing an optical diffuser is carried out as follows.

Example 1.

According to the proposed method, an optical diffuser was produced by applying a relief microstructure to a substrate made of aluminum alloy B95 with a carbide conical indenter with an angle at the top of 150", by thermopressing on a substrate made of polycarbonate with a relief microstructure.

Indentors made of hard steel (hardness not less than 850 NM10) or tungsten carbide (hardness not less than 1500 NM10) were used, the surface of which can be polished to a mirror. The most durable among known aluminum alloys - VU95 - was used for the manufacture of stamps, on which, during indentation, the formation of conical recesses with a mirror surface is ensured. Polycarbonate was used as an optically transparent polymer material. because Thermopressing was carried out with a stamp with a temperature of 100-120"C on a plastic substrate also heated to 90-1007C at a pressure of 5-10 kg/mm. The time of applying pressure to the stamp was 20-80 seconds.

The conical recesses were placed on the metal substrate in such a way that the distance between the centers of the recesses with a diameter О equal to 0.8 mm was 0.88 mm (Ож0.10)3. The manufactured optical diffuser was a transparent substrate, on the surface of which a relief structure was formed.

The manufactured optical diffuser provides a light transmission coefficient of more than 90 95 with a simultaneous reduction of the unscattered component to 1-3 95. Fig. 2 shows an image of the light-scattering surface formed on the surface of the polycarbonate substrate.

Example 2.

According to the proposed method, an optical diffuser was made by applying a relief microstructure to a substrate made of aluminum alloy B95 with a carbide conical indenter with an angle at the top of 150", by thermopressing on a substrate made of polycarbonate with a relief microstructure. The materials and conditions of thermopressing are described in example 1.

The conical recesses were placed on the metal substrate in such a way that the distance between the centers of the recesses with a diameter of 0.8 mm was 0.84 mm (0О-0.050)3. The manufactured optical diffuser was a transparent substrate, on the surface of which a relief structure was formed. The manufactured optical diffuser provides a light transmission coefficient of more than 90 95 with the value of the non-scattered component up to 2-4 95. The increase in the value of the non-scattered component is associated with a partial deformation of the shape of the depressions on the metal original.

Example 3.

According to the proposed method, an optical diffuser was made by applying a relief microstructure to a substrate made of aluminum alloy B95 with a carbide conical indenter with an angle at the top of 150", by thermopressing on a substrate made of polycarbonate with a relief microstructure. The materials and conditions of thermopressing are described in example 1.

The conical recesses were placed on the metal substrate in such a way that the distance between the centers of the 0.8 mm diameter recesses was 1.2 mm (00.50). The manufactured optical diffuser was a transparent substrate, on the surface of which a relief structure was formed. The manufactured optical diffuser provides a higher light transmission coefficient

From 90 95 with the value of the non-scattered component to 5-6 95. The increase in the value of the non-scattered component is due to the fact that part of the light is not scattered on the microprotrusions.

Thus, the proposed invention makes it possible to ensure high light transmission and reduce the proportion of unscattered light in optical diffusers while simultaneously ensuring the quality and high repeatability of optical diffuser characteristics due to their manufacture in the form of a relief microstructure with different predetermined angles of deflection of scattered radiation and with different placement of depressions on metal substrate.

Claims (3)

FORMULA OF THE INVENTION 1. The method of manufacturing an optical diffuser in the form of a relief microstructure, which is characterized by the fact that it includes applying a carbide conical indenter with an angle at the top of (120...160)2 conical depressions on a metal substrate, which is later used as a stamp for thermopressing a relief microstructure in the form conical protrusions on an optically transparent polymer material. 2. The method according to claim 1, which differs in that the distance between the centers of adjacent recesses with a diameter of О is from О--0.05 О to Ю-0.50. 3. The method of manufacturing an optical diffuser according to claim 1, which is characterized by the fact that the application of conical recesses is carried out with an indenter with a surface roughness of KE 0.80. they are in Z still a with 5 OK OO eV ok XX x OV Fig. 2 00 Computer keyboardA. Krulevskyi (00000000 Ministry of Economic Development and Trade of Ukraine, 12/2 M. Hrushevsky St., Kyiv, 01008, Ukraine SE "Ukrainian Institute of Intellectual Property", Glazunova St., 1, Kyiv - 42, 01601