DE7135934U - OPTICAL FILTERS - Google Patents

Description

AQ FAK3 EVAEFiT AG

PATENTAL, PARTUNQ LEVERKUSEN * '· Sßp. 1S7I

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Optical filters

Optical filter discs made of singly colored gelatin, be it those of constant density with points of different density, away. Step filter or filter continuously variable Density, have long been known.

Step filters or filters of continuously variable density are used in exposure control devices for photographic recording devices. For example, when measuring light through the lens _f , a step filter is pivoted more or less far in front of the light-measuring element of the exposure control in accordance with the sensitivity of the photographic material, in order to take the film sensitivity into account when measuring the light.

Another application example, preferably for a filter continuously variable density, exists when setting the aperture values of cine film cameras. Here can one Iris diaphragm can only be reduced to a certain value without diffraction phenomena occurring. Another weakening of the recording light is then more or less deep

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Swinging in a filter of continuously variable density , achieved in front of this smallest adjustable aperture.

For coloring the copier light of photographic copier machines and maximum filters made of colored gelatine are used.

When the filters are manufactured using conventional methods, _| Gelatin solution colored accordingly and so much hardener added that the casting solution can be processed for a long enough time for the production of the filter and beyond that the Farbfijtofx does not undergo any change (discoloration) by the hardener. These restrictions lead to underdooing of the hardener, only partially hardened gelatine filters are produced.

The gelatin is placed on a glass plate provided with a release agent poured and pressed a mold over it, through which the thickness of the filtercliicht is changed, and the filter thereby the the desired density curve is obtained. After the gelatine has cooled down, the mold can be removed.

Long before the gelatine is hardened, wedge-shaped or step-shaped filters are used to improve mechanical stabilization poured a Gi.genschicht of transparent gelatin, ao that you have a plane-parallel, partially hardened filter after detachment received from the glass plate.

The partially hardened gelatin filters produced in this way are not sufficiently resistant to climatic influences due to the still existing hydrophilicity. It has been found that changes in the filter occur after a short time under alternating and tropical climates, namely shrinkage of up to 20 pounds, warpage and local thickening, which severely impair the density profile.

Sa protection of the filter before ElimaeinfKissen, eg plates through glass due to the rorgegsbenen dimensions is not possible, it koBBt often sub failure thus equipped modules in autoaatisehen CaBerac. Line use in areas of the tropical climate is not permitted. AG 876 - 2 -

The invention is based on the object of using optical filters to find a colored gelatin layer, which can be produced in a simple manner and which even under extreme humidity

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E3 now became an optical wedge filter with one on one Colored gelatin layer arranged on the support found, that consists of a flexible, transparent layer support, a colored gelatin layer with stepped or continuous increasing layer thickness and corresponding density gradient and a flexible, transparent solid with the colored gelatin layer connected cover sheet consists.

A preferred embodiment of the optical filter according to the invention is shown in the figure. Here 1 means one flexible transparent substrate, 2 the colored wedge

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foil.

Foils made from cellulose esters such as cellulose acetate are used as the substrate or cellulose acetobutyrate, polycarbonate, preferably based on diphenylolpropane, polyesters, in particular based on polyethylene glycol terephthalate or dimensionally stable Carriers made from other transparent and flexible polymers are suitable. The substrates have a thickness of 100-200 /around.

The filter layer consists of hardened gelatin with a dissolved or finely dispersed dye or dye mixture. Suitable dyes are, for example, finely divided silver, finely divided carbon black or organic dyes or Dye mixtures such as those in American patents 2,622,026 and 2,954,349, in German Patent 893,011 and in German Auslegeschrift 1,184,211 are described.

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The cover film consists of a transparent and flexible film made of cellulose or cellulose derivatives such as esters, in particular Cellulose acetate, polyesters or polyolefins such as polypropylene or polyethylene. The cover sheet preferably has a thickness of 60 - loo um.

The optical filters according to the invention are manufactured as follows:

On the support made of the above-mentioned materials, which preferably have an adhesive layer to firmly bond the hydrophilic layer of the colored gelatin to the generally more hydrophobic support _; the colored gelatin layer is applied in the usual way. The casting solution for this filter layer preferably already contains a small amount of hardening agents such as mucochloric acid or inorganic hardening agents such as chrome alum in order to achieve a slight pre-hardening of the filter layer. The colored filter layer is then exposed to a preferably saturated normal atmosphere. This intensive neck hardening is preferably carried out at room temperature and at / reduced pressure, preferably between 10 and 50 Torr, in particular at about 20 Torr. The time for this post-curing can vary within wide limits, depending on the desired degree of curing, the temperature and the partial pressure of Jorm aldehyde. In general, exposure times between 10 hours and several days are sufficient. At a formaldehyde partial pressure of about 20 Torr and room temperature, the exposure time to achieve a sufficient degree of curing is about 2 days. This post-hardening gives highly hardened, relatively hydrophobic gelatin layers of sufficient mechanical stability. It is of particular advantage that in the case of the hardening process according to the invention with a weak pre-hardening when the colored gelatin layer is poured and the post-hardening in a formaldehyde atmosphere, the dyes in the filter layer, which are often sensitive to hardening agents, are not influenced or only to a negligible extent *

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On the gelatin layer that has been cast and hardened in this way the cover sheet is preferably self-adhesive by lamination Foils applied. The lamination prevents warping due to the unequal thermal expansion coefficients of the carrier film and uclaoixie, as there is ax geiatin layer between the parts is located.

Filters produced in this way show no changes in hatred when exposed to alternating and tropical climates. They are therefore suitable for use in the tropics. In the short-term test (storage in water at 20 ^° C. for 10 minutes), the swellability of the filters produced in this way is 50 Ji lower than that of the filters produced by conventional methods. Deformations under extreme humidity or temperature, such as shrinkage or warping, do not occur.

example 1

On a polyethylene glycol terephthalate support, i ^ O / .mu.m thick an adhesive layer according to example 7 of French application 1,455,785 is applied in two applicators:

Composition of the 1st application solution

8 g of a polyester made from isophthalic acid and ethylene

glycol according to preparation example 8 from the French rate cachrift 1.4351785
92 g of 1,2-dichloroethane

Composition of the 2nd application solution

10 g gelatin

50 g of water

1 g maleic acid
615 ml of methanol
14-5 ml of butanol

j 140 ml of acetone

4 g cellulose nitrate (K value 30)
50 ml of methyl glycol

On the subbed film support is a neutral gray colored gelatin filter layer of a coating solution mainly having a viscosity of 14 ep (40 ⁰ C) constructed as follows 876-5 -

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is applied:

10 wt. * Gelatin mp 35 ⁰ C for 2 wt. * 5 * aqueous sodium Chromalaumlöaung Raschit 0.1 wt. *

3.0 wt. * Of a black dye or black dye off mixtures, as described, for example, in the above-mentioned patents,

84.9 wt. * Water

The amount of dye depends on the density of the product to be produced Filters. In the event of changes in the proportion of dye the proportion of water is varied accordingly.

A circular Kei-1 shape is placed on the still liquid gelatin layer, which gives the filter a corresponding density profile, pressed on. After the gelatin has solidified, the mold is removed and dried in circulation at room temperature.

Example 2

On a 200 / U thick cellulose triacetate film is a Adhesive layer of the following composition applied:

12 g gelatin 25 ml water 4 g phthalic acid 0.9 g glyoxal

11 g of a cellulose acetate with 56.0 * acetic acid and a K value of

177 ml of methanol 770 ml of acetone

The gelatin filter layer is applied as in Example 1 described.

The filter produced in this way is now placed in a vacuum cabinet Tree temperature and a partial pressure of 20 Torr formaldehyde Post cured for 48 hours.

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In the storage compartment, the gelatine of the wedge filter has a thickness of 5.0 μm at the thinnest point and 250 μm at the thickest. This layer thickness range corresponds to a filter thickness range from 0.10 to 3.00. An adhesive film made of cellulose acetate, which completely covers the filter, is then applied to the filter layer.

To test the dimensional stability, the filter is stored in an alternating climate according to DIN 50016 for 1000 hours. In addition, ei: ie stress in continuous tropical climate at 4-0 ⁰ C unc 93 # RH üb jr further 1,000 hours made. No changes in shape or density could be observed after storage.

For comparison, a similar round wedge filter is produced in the conventional way by applying the same filter layer to a glass plate, shaping the filter and applying a pure gelatin solution to produce a plane-parallel filter. Such a filter under the above conditions overlaid one, occur so strong distortions and density changes that the filter is no longer usable.

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Claims (2)

Claims 1. Optical wedge filter with a mounted on a substrate colored Grelatineschichc, consisting of a flexible Layer support, a colored gelatin layer with stepwise or continuously increasing layer thickness and the like Density gradient and a flexible, transparent cover sheet firmly bonded to the colored gelatin layer. 2. Wedge filter according to claim 1, characterized in that the substrate has a thickness of 60 - 5QCyUE and the Deek film has a thickness of 60-100 / µm. AG 876 - ⁸ - 713593416.1171