DD127943B1 - PHOTOCHROMES MATERIAL WITH IMPROVED SENSITOMETRIC PROPERTIES - Google Patents

Description

VEB film factory Wolfen Wolfen, the 22. 8. 1979

PN 671 / Wi / Br

Int.Cl. G 03 с 1/733

-Ί- 195 397

Potochromic material with improved sensitometric

properties

Field of application of the invention

The invention relates to a room temperature radiation sensitive composite of photochromic layers consisting of a number (> 1) of monolayers containing a photochromic compound dispersed in an organic binder ©

Characteristic of the known technical solutions

After G.H. BROWN "Photochromism", Techniques of Chemistry, Wiley-Interscience, 1971. It is already known that certain photochromic compounds, dissolved in a liquid or embedded in a polymer, are colorless or slightly colored at room temperature and are colored by irradiation with ultraviolet light. The color may disappear again if the dyed product is stored in the dark or exposed to visible light. The photochromic compounds have a variety of uses, e.g. for optical switches, in microfilm, for normal reproduction purposes, in photoelectric meters, etc.

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The photochromic compounds are dissolved in a variety of solvents or embedded in various organic binders and optionally applied to suitable support. Also known is a multilayer material, but this was developed with the aim of achieving a stable gray image hue by mixing several individual colors (GB P 1 236 423) · However, neither in this nor in other patents is reported a line- grade gradation behavior of photochromic materials required for reproduction purposes in the photographic industry.

The gradation-f "is defined as f = Δ Ε

Δ IgCI ₀ .t;

and thus serves as a measure of the contrast reproduction of the recording material in comparison to the original · The previously used photochromic materials have, according to their own investigations, only an insufficiently large linear range of the blackening curve. However, this is decisive for the gradation behavior of the layers and thus also for the reproduction of originals. This leads to a falsification of the original information, which is associated with a limitation of the applicability. When changing the irradiation intensity, the change in the gradation also has a negative effect on the reproduction.

Object of the invention

The object of the invention is to provide a photochromic material suitable for reproduction purposes, which better reproduces the original information and thus can be applied more versatile.

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Explanation of Wegeng the invention

The object of the invention is the preparation at room temperature to radiation sensitive photochromic layers or layer associations, the improved for reproduction purposes sensitometric properties insbegondere rectilinear _s gradation behavior comprise. According to the invention the object is achieved in that the photosensitive layer or the composite layer consists of polymer layers containing different concentrations of a photochromic compound and are arranged so that the concentration of the photochromic compound along the direction of irradiation increases. As a result of this arrangement, the receptivity of the material increases along the direction of irradiation (that is, into the interior of the layer).

As photochromic compounds, all members of all known photochromic substance classes, e.g. Spiropyrans, triphenylmethane dye leuco compounds, anils, hydrazones, stilbenes, sydnones, semicarbazones, osazones, o-nitrobenzyl derivatives, azo compounds, formazans, azines, triazenes, aziridines, indigo and thioindigo derivatives, aminocampher derivatives, anthrones, thiosulfonates, indene oxides, N-nitroso-N alkylanilines, cyclobutane derivatives, thymine derivatives, cyclohexadiene derivatives, benzofuran derivatives, benzophenones, dihydropyrenes, N-benzylideneaminopiperidines, hexaarylbiimidazolyls, octaphenylbipyrryls, etc., may be used.

The idea is based on the following theoretical consideration: A layer structure S consists of η (^ 1) single layers S ^ (n, i integer, 1 £ i <n), of which S-. lie on the surface of S and p ₁ respectively under S ^ (see. also principle sketch) e The surface of S will irradiated with a (vertical) current ^) monochromatic light of the write wavelength 2.beta.

195 397

(T)

UU ₂ <*>

♦ n-1 <*>

Schematic diagram for construction and exposure of a layered composite

Let the coordinate χ run with the beam direction and have its origin at the layer surface "The image of the layer S ₁ on the x-axis is the interval (X _1-1 <x <.x _i ) (1 <i <£ n, x _Q = »o). The single layer S ₁ is hit at χ = X _1-1 , that is, at its surface, by a certain luminous flux ^ _1-1 Ct), which makes up only a part of φ (namely, that of the part of the composite above Sj was not absorbed) and released at χ = X ₁ (usually) again lower luminous flux (J) ₁ (t), which now hits the subsequent layer S ₁₁ , or »emerges from the underside of the dressing S when i = η was ·

If one understands for 1 <U <n under D ₁ ^S ((|), t) or D ₁ ¹ (φ, t) the optical density of the write light current i> irradiated detail layer S. in light of write or «Reading wave

length and under D (<J> ₀ , t) the optical density of the laminar structure (yes with the write current (J) applied

1953

, t) ~ Σ2 D ₁ ¹ (^ ₁ Ct), t) (1)

becomes) at reading light, then:

[= 1

+ -D^s

ψ, (ΐ) = {/ - ^{1 Tl} - ^{1 for}

¹ φ, for i = o

If we choose (of course compatible with each other) monolayers of whose density behavior is well known (depending on consistency, thickness and exposure) and builds a layer system on, it can be (with appropriate procedures here are border crossings ^х · ".- t-

oo permissible) because of the overlapping (1) of the individual

Strengths require that the gradation Ъ D / <9n of the resulting total layer (H = ty t: exposure) deviate only insignificantly from a given constant over a large exposure range {h ^ CH <H ₂ J:

The photochromic layers of the invention or · layer dressings can be manufactured by the usual film manufacturing techniques _o

The outwardly falling concentration gradient of the photochromic compound can firstly be generated in a technologically suitable manner within a polymer layer. Secondly, the goal is achieved by making individual layers of polymer one on top of the other

_ _β . 195 397

This means coating first with a highly concentrated polymer solution and subsequently with lower concentrated solutions. At minimum, two layers of different sensitivity are necessary, but the number of individual layers is not limited.

Insulating intermediate layers can be present according to the invention between and / or over the differently sensitive photochromic layers; likewise, inactive filter layers can be incorporated according to the invention.

According to the intended use, especially polymer films, glass plates, paper sheets and metal substrates serve as underlays, but there is also the possibility that a backing is dispensed with and the polymer binder strengthens with sufficient layer and stability itself serves as the carrier substance.

The polymer binders used are polystyrene, polyvinyl butyral, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, polyacrylates, polymethacrylates, polyvinyl formal, polyamides, polyvinylidene chloride and copolymers thereof. Due to the increasing sensitivity within the photochromic layer or of the layer composite along the direction of irradiation, a linearization of the blackening curve E / lg (I.t.) is achieved and thus an improved gradation behavior.

A further advantage of the photochromic layers or layer composites according to the invention is the greatest degree of independence from the intensity of the irradiation light. For example, intensity fluctuations of the light source during the reproduction process do not change the sensitometric data of the photochromic material (compare FIGS. The invention makes it possible to provide a reproduction material based on technologically readily available photochromic compounds without any further additives.

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The materials according to the invention are distinguished by high color density and improved sensitometric behavior, in particular straight-line gradation, and can be processed in the dry state.

The photochromic material can be reused several times, since the information written in by means of ultraviolet light can be erased by irradiation with visible light or by storage in the dark.

The layer or layer dressings have a high resolving power and, when suitable supports are selected, are virtually grainless and transparent

The invention will be described with reference to some embodiments, which are only illustrative and not intended to limit the invention,

example 1

A 20% solution of piacryl / polyvinyl acetate in cyclohexanone / dichloroethane (1: 1) containing 6'-nitro-1,3,3-1-trimethylindolinobenzospiropyran (6 ^f -Iiitro-BIPS) is suitably made 6 l strong Layer applied to a PETP film, so that a concentration gradient of 0.05 mol / kg o. · 0.35 mol / kg б'-lTitro-BIPS is built up falling outward in the polymer layer. This layer is dried in the dark. The dried transparent material on irradiation with ultraviolet light (L = 365 nm) gives a red-violet image with a gradation of about 1.0 over a working range of ΔE> 1.0. By irradiation with visible light (Jt = 577 nm), this color image can be deleted again «Thus, the material is used several times ·

Example 2

A 20% solution of piacryl / polyvinyl acetate in cyclohexanone / dichloroethane (1: 1) and 5 % dibutyl phthalate (referred to

1953 397

to the binder reagent) as a plasticizer containing 0.3 mol / kg of''-nitro-BIPS is suitably applied to a PETP film as a 3.5 μm thick film, above which is an equal binder layer, the 0, 15 mol / kg of 6'-nitro-BIPS, also 3.5 / um thick, poured and in turn a 2 / um strong empty binder protection layer. Ba is dried in the dark. The dried material on UV irradiation gives a red-violet image with a gradation of about 1.30 over a working range of 4E> 1.0.

By irradiation with visible light of this color image is deleted, also the color disappears when stored in the dark · The material is used several times ·

Example 3

A 20% solution of piacryl / polyvinyl acetate in cyclohexanone / dichloroethane (1: 1) and 5 % dibutyl phthalate as plasticizer containing 0.3 mol / kg 6'-iitro-BIPS is applied to a glass plate as a 3 / um thick layer When applied, an equal 2 / lim thick binder layer is poured which contains 0.2 mol / kg 6 ^f -liitro-BIPS and, in turn, a 2 / um thick binder layer containing 0.1 mol / kg b'-nitro-BIPS contains. The material is dried in the dark. The dried composite is exposed to ultraviolet light to form a red-violet image with a gradation of about 1.05 over a working range of ΔE> 1.0.

Irradiation with visible light or storage in the dark causes the color to be extinguished. The material can be used several times ·

The advantage of the material suitable for reproduction purposes is in particular the rectilinear gradation over a working range of ΔE> 1.0 and its greatest independence from the intensity of the irradiation light, whereby no change in the sensitometric data occurs during the reproduction process.

«* 9 -

Claims (3)

-9- 195 397 invention claim A photochromic material consisting of a photosensitive layer or a photosensitive composite and optionally a protective layer, characterized in that the photosensitive layer or layer consists of polymer layers containing different concentrations of a photochromic compound and arranged so that the concentration of the photochromic compound increases along the direction of irradiation O 2. Photochromic material according to item 1, characterized in that there are insulating intermediate layers between some or all of the individual layers of the composite layer. 3 · Photochromic material, according to items 1 and 2, characterized in that the composite layer contains photochemically inactive filter layers. For this ... JLSeiten Zekkungen