DE3019100A1 - High resolution scattering screens for optical appts. - coated with scratch-resistant polymethyl methacrylate lacquers contg. powdered quartz - Google Patents

Abstract

The screens are prepd. by applying a scattering lacquer onto glass or plastic carried, using a free-falling lacquer film. The lacquer comprises a clear polymethyl methacrylate contg. 10-20% powdered quartz of particle size 1-10 mu m and/or 10-30 mu m; 0.01-2.0% of a silicone oil, and 1-15% of an acid to dispersion; it has a viscosity of 253-133 cP/20 degrees C. It is applied to the carrier, as a layer 80-250 mu m thick.

Description

Process for the production of lenses with high

Resolving power The invention relates to a method for Manufacture of high-resolution diffusers used in optical devices for displaying pictures, measuring scales, etc. on the way of transmitted light projection come into use. In addition, diffusion lenses of this type are used for uniformly diffuse Illumination of rooms and surfaces in optical device construction application.

It is known to produce lenses for projection purposes by Grinding or etching glass surfaces with a defined roughness (Optik 1, 238, (1946)).

Another well-known method of making proåection screens consists in applying a layer of finely divided inorganic pigments with the help of a film-forming binder on a transparent support plate made of polymethyl methacrylate to fix. (DE-GM 1 834 760).

It is, however, a major disadvantage that diffusion lenses produced in this way only have a very small half-value angle which does not exceed 3 to 5 ° and the resolution in image reproduction is also completely inadequate.

In order to remedy this deficiency, there are methods for the production of diffusion lenses or matt films made from organic polymer mixtures with the addition of scattering agents Polyester dispersions became known. (DD-wP 510903 DD-WP 101 333).

Although the scattering power up to the half-value angle of about 250 could be increased, the resolution is partially insufficient. aside from that decreases with increasing Half-value angle is the permeability of the lenses or foils and thus the brightness of the images. Finally, there is stability of the surfaces with regard to mechanical, climatic and thermal influences inadequate and is not sufficient even with additional protective measures Security guaranteed.

To improve the smear and tensile strength as well as the adhesive strength the scattering layers on plastic carriers, a process has also become known are provided with the plastic carrier disks with a scattering layer; from Nitrocellulose lacquer and finely divided wet-precipitated, highly dispersed silica exists, which has previously been hydrophobicized by treatment with silane compounds (DD-WP 1 12006).

The shortcoming here, however, is that here too the permeability drops sharply at half-value angles over 150. In addition, higher half-value angles can be used than 15 ° can only be achieved by repeated coating, which means an increased technological and time expenditure means. In addition, the 'process is on plastic backing limited.

Another technical solution is that projection screens consist of plastic sheets or films with inorganic pigments, such as z. B.

monoclinic magnesium silicate, calcium silicate, barium sulfate or zinc oxide are filled. (DE-OS 2 201 467).

The disadvantage here, however, is that the given high permeability with insufficient resolution, contrast and scattering power (too small Half an angle) is connected, so that such lenses for use in optical devices are not suitable.

Finally, projection screens have become known in which the Scattering effect through a polymer layer with embedded wax or crystalline Polymer component and also embossed on the surface with a leflticular structure is caused. (DE-OS 2 614 606).

However, the resolving power and the permeability are also important here insufficient.

In summary it can be stated that it is according to the state of the art So far not possible, diffusing screens for back-light projection with high resolution that at the same time have a large half-angle (high scattering power) and have high transparency (image brightness) and are also resistant to mechanical, thermal and climatic influences are stable without additional protective measures.

The aim of the invention is a method of manufacture of diffusing screens with high resolution, with which the mentioned shortcomings and disadvantages be avoided. It should be achieved that with large half-value angles (high Scattering power) at the same time a high resolution and a high permeability is guaranteed.

The object of the invention is to provide a method with which it it is possible to set the half-value angle of the lenses in a range between 80 and 300 can be set selectively and specifically, with a resolution between 22 and 15 pairs of lenses per millimeter and a transmission of at least 50 is guaranteed.

The lenses should also protect against mechanical, thermal and climatic influences be stable. The dimensions of the lenses should be used if necessary can also be larger than 1 m2.

According to the invention, the object is achieved by a method. Manufacturing of diffusing screens with high resolution by applying a diffusing lacquer Glass or plastic carrier released by means of a free-falling lacquer film, which is characterized by this is that in Polymethylmethaorylat clear lacquer 10 to 20 wt .-% quartz powder -with a Grain size from 1 to 10 / um and / or with a ner grain size from 10 'to 30 / um below simultaneous addition of a silicone oil in an amount of 0.01 to 0.02 wt .-% and a dispersing aid in an amount of 1 to 1.5% by weight in the next process step, the viscosity of the scattering paint to a value from 253 cP to 133 cP at. 20 ° C is brought - and the finished paint with the help a casting device in a layer thickness of up to 250 μm, measured in the dry State to which the carrier material is applied.

The diffusion lenses produced by the method according to the invention have a resolution of at least 22 at a half-value angle of 8 ° Line pairs per mm and a transmittance of 30 ° be-80%. in case of a Half-value angle of 30 °, the resolution is at least 15 line pairs per mm with a permeability of at least 55%.

The uniformity of the optical parameters are also achieved with surfaces = 1- m2 guaranteed. The lenses are scratch and smudge-proof and can be up to used at temperatures of-GO0 C without impairing their optical properties will.

The invention is illustrated by the. the following examples explained in more detail.

Example 1: 12% by weight quartz powder with a grain size of. 1 to 10 / um together with 1.5% by weight of a 1% strength xylene solution of a silicone oil (e.g. MM 1-50 from VEB Chemiewerk Nünchritz) and 1.5% by weight Na-Al-silicate dispersion as a dispersing aid (e.g. micro extender A 103 from VEB Chem. Fabrik Fährbrücke) Stirred uniformly in 25% by weight nitro thinner. This mixture is in 60 wt .-% Stir in polymethyl methacrylate paint (e.g. LT 30 from VEB nitrogen works Piesterit-z). With the help of an addition of further nitro thinner, the scattering lacquer is adjusted to a viscosity set between 253 cP and 133 cP at 20 ° C.

This ready-to-use paint is made with the help of a pouring device applied in a free-falling lacquer film to the carrier plates made of glass or plastic, so that the dried scattering film has a thickness between 80 and 100 µm. One The lens produced in this way has a half-value angle of 80 to 100 for a Resolving power of 22 line pairs per mm. Appropriately, the dried Diffuser lenses hardened for 2 to 5 hours at 800C.

To improve the contrast or for physiological purposes The lenses can be colored for reasons. Dyes are suitable Wofanol or Neozapon series, which are soluble in organic solvents. The dyes are used in a single solution, up to 50% instead the amount of nitro thinner used is added to the paint.

Depending on the intended use, the temperature and climatic resistance can be increased by prior to coating with varnish the Surface of the carrier plates with a commercially available matt lacquer or a polyvinyl acetate clear lacquer The diffusion lenses are primed with a layer thickness of 25 to 50 / um then a climate stability of at least 6 days in a humid alternating climate and a temperature resistance of + 55 ° C to -40 ° C. The litter is scratch-resistant and does not need to be specially protected.

Example 2: As described in Example 1, the paint is under Use of 15% by weight quartz powder with a grain size of t to 10 μm produced and applied.

Diffusing screens with a half-value angle of 20 to 25 ° are obtained with a layer thickness of the litter layer in the dried state of t20 to 150 around. The resolving power lies; between 20 and 22 line pairs per millimeter.

If you use the same amount of quartz powder with a particle size between 10 and 30 µm, a resolution is obtained with an unchanged half-value angle of 20 line pairs per millimeter.

Example 3: Corresponding to the procedure described in Example 1 a diffusing screen is produced using a diffusing lacquer, the Share of quartz powder with a grain size of 1 to 10 μm to 18% by weight and the layer thickness' of the dried litter layer is increased to 200 to 250 μm. Diffusing lenses are obtained with its half-value angle between 30 and 350 with a resolution of = 15 line pairs per millimeter.

Claims (1)

Claim. Process for the production of diffusing screens with high resolution by applying a scatter varnish to glass or plastic carrier using a free-falling Lacquer film, characterized in that in polymethyl methacrylate clear lacquer 10 to 20 % By weight quartz powder with a grain size of 1 to 10 μm and / or with a grain size from 10 to 30 / µm with the simultaneous addition of a silicone oil in an amount of 0.01 to 0.02% by weight and a dispersing aid in an amount of 1 to 1.5 Wt .-% are incorporated, in the next process step the viscosity of the scattering lacquer is brought to a value of 253 to 133 cP at 20 ° C and the finished scattering paint measured with the aid of a pouring device in a layer thickness of 80 to 250 μm in the dry state, is applied to the carrier material.