DE1596429A1 - Process for manufacturing optical elements - Google Patents

Description

Eastman Kodak Company, 343 State Street, Rochester, New York State * United States of America

Process for the production of optical elements

The invention relates to a method for simultaneous Manufacture of several transparent polycrystalline optical elements from undeserved th crystalline powders of inorganic

Links.

It has been known to produce individual optical elements permeable to infrared rays from uncompacted crystalline powders of inorganic compounds by hot pressing by subjecting the powders to a high temperature below the melting point and a high mechanical pressure while they are enclosed in a mold ,, that under certain temperature and pressure conditions it is possible to convert inorganic powders into a larger

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You: to condense as 991 of the theoretical density of a single crystal of the same material, then the resulting poly. ·. i '* 3lline element for infrared rays and jii ut-r rule also for more visible. Light is permeable *

So far we have always had individual elements of such thickness through H9j; "verpreäi'iu horp- ^ represents, di" larger ice the thickness äe ^ c-ls Er..iproiii kte desired ortischs' F.le ^ duck is. The ei? Iltea ^ J ^, ^ e, h ^{,: r} pressed blank was then formed into several thin elements, which intestinal elements of the desired size were processed. Outwardly pressed raw in- ^v with egg-size: OuTciünesser of 15.24 c: ir. (6 inches) and a thickness feedforward 1.27 cm ₍₁ S O inch) can be, for. B. xur production of individual pieces vcr>. 0.254 ent (0.1 incU) thick ^ - zt-rsaised, round sanded i * n un £ polished, this tecii ^ ik i ^ t for spontaneous generation both before. Flachscheibenelemer.tiii and of elements close to the Fenn! 'O-iler Do "e, ang ciu ^ ^ t been. Although this result Veι άά satisfactorily working ^ it has yet certain. Disadvantages such as high costs, long production time and the large Expense _f dan as required to the dickei "Auögangsrüliliüge in thin biemeüte for subsequent finishing optiiicke to divide" Further göht eiae not unweiontiicbe Meuge of valuable crystalline material by

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The object of the invention is therefore to create a method

after then it is possible to have several transparencies at the same time optically · EleiMiite to manufacture in due time and without greater «to separate losses of crystalline material from one another,

The invention relates to a method for simultaneous

Produce several transparent polycrystalline optical

Bissient "au" yriver-compacted "crystalline powders of inorganic compounds" characterized in that the powders are made from stacks of several loosely one on top of the other, one blank with less than 991% of the theoretical density. _t H) forms, between every two adjacent soaps, a layer of Ti # imfflat © .rial, which cannot be erased with the blanks, that whoever hot-presses the stack under such temperature and pressure conditions that the density dfy blanks after the hot-pressing over 991 theoretical point of view is * and the resulting elements are transparent separating USA d "S is the Klenente obtained from each other.

Until the stacks are hot-pressed, they are made in a fine hollow shape im te τ use a nechanisch or manual beti; ti} .; biren Ram or plunger.

The invention achieves that: leiciizeitiy Jiielirere ^ irazelne iileiuente »which annaled the right thickness for that as the end product have desired parts, in acceptable

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Jk .'ί

Time can be made without the need for sawing the elements as in the previous methods.

All inorganic compounds which have previously been successful (fa have been hot-pressed. For example:

Magnesium fluorine Canadian patent 646,436

Zinc Sulphide U.S. Patent 3,131,025

Calciuir.fluorid Canadian Patent 701 845

Zinc Selenium Canadian Patent 688 568

Magnesium Oxide U.S. Patent 3,236,595

Canadian patent 731 706 French patent 1 476 Ca dn.i unite 3.1 ur i d Χ

Lanthanum fluoride U.S. Patent 3,206,279

Cadmium Sulphide Canadian Patent 723,556

ZincoxyU Canadian Patent 706,800

Stronti ¹ . : uorid Canadian patent 727 530

Ti r. , iicxyU USA patent :. Ser. λ'ο. 517 937

• JciJr "iuinselej: id USA patent application. Ser. No. 517 965

The optimal temperature, pressure and time conditions are listed in the above-mentioned publications for each particular connection. Temperatures above 30 ° ^u e (S32 ° F) and pressures above 665 kr / cr are generally suitable; ² (9500 psi)

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applied.

The drawing serves to explain the invention in more detail.

Fig. 1 is a fragmentary schematic vertical view Plane, partly in elevation, through a device for cold pressing powders into blanks of less than 99% of the theoretical density, which is then stacked and hot-pressed;

Fig. 2 is a schematic partial vertical view Level through a device for hot pressing a stack of flat blanks and

3 is a schematic partial view in a vertical plane through part of a device for hot pressing a stack of domed blanks.

According to Fig. 1 is a mass (11) from an undeserved Powder of an inorganic compound introduced into the cavity of a press mold (13), whereupon by means of a press ram (15) Pressure is exerted which turns the powder into a flat disk (17) of we s entliclijge lower density than it original powder, cold-pressed. The temperature can be room temperature. The mold can also be heated werclenj, although there is no particular advantage in that.

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Instead of a single blank several may optionally at once in a mold with several Hehlungen and aisammenarbei'enden plunger as used herein bends are cold-pressed * The term "cold pressing", that applied when Pressvu.gang temperature is much lower than the Temperature used later during hot pressing, so d ~ ₅ ; i the resulting blanks are not transparent, but opaque and have a density that is significantly below 991 of the theoretical density.

Cold pressing can be done quickly and the individual blanks, as they are pressed, can be removed and then stacked in an axial orientation for hot pressing. In order to prevent the blanks from melting together, a layer of a m: .t den; Material of the blanks aicht vsrmischbaren Trennmatt .rial (19) inserted between adjacent blanks (Fig. 2). Advantageously, the release material is also mounted under and above the blanks to a slight separation of the stack to ensure from the hot-pressing apparatus. The stack can then be introduced into the cavity of a press mold (2i) within an oven (23), which is electrically heated during the pressing process,

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A press teat or plunger (25) is applied to the top of the stack. The desired pressure is by downward movement of the plunger or piston caused · Preferably, maintaining an inert atmosphere within the furnace (23), which by applying a R & kuyifl "through a line (27) or by introducing a .teerten gas _t vie argon, through the same line

If necessary, the stack can also be inside the mold through alternating introduction of separating materials and raw materials * liagea to be built. '.

The device shown in Fig. 3 is littrieben in the same way. In it a pile of kai tv-: ---- r es-ί th, ntuldenarSig g®wöibt # n blanks (31) , interspersed with spacers ( SS} is pressed inside a mold (33) with an upwardly directed concave Bcdej) (34). The pressure piston (35) has. iz "in this case a convex end, which is adapted to the mold"

You can use any suitable spacers (13) and (32) Material that enables the separation of the Ro'Mn ^ c and they to one: sticking together at the high temperatures and printing prevents the hot-press. Suitable

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Materials consist for example of metal, paper and graphite, suitable metals are copper, molybdenum, titanium and stainless steel, e.g. of the 301 type. A decomposable material such as paper can also be used, as that caused by charring obtained residue causes separation. Ceramic materials such as sintered aluminum oxide can also be used with or without mold release agents such as a colloidal carbon suspension (Aquadag).

Instead of using special spacers, you can use the cold-pressed Blanks also individually with a surface coating made of a release agent, e.g. a colloidal carbon suspension, which can be applied by spraying, brushing or plating. This can be especially true for Processing of complex structures can be advantageous, e.g. in the case of hollow structures, e.g. hollow domes, whereby the total volume the non-compacted feed versus the compacted feed in an asymmetrical manner by a Factor ■ / on distinguishes four or five. There molded spacers made of metal or the like. For complex structures are quite expensive, surface coating agents are used in these Cases preferred.

Instead of a special compression of the powder by cold pressing the compression can preferably be carried out in the same mold (13) or (33) in which the hot pressing takes place.

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be guided. When making flat disks, the correct amount of powder for one blank is put in the shape (13) introduced and then by introducing a Compressed pressure piston that can be activated by hand. Then a spacer (19) is on the Surface brought and another batch of the powder introduced onto the surface of the spacer and compacted. These measures are repeated alternately until the desired size of the stack has been obtained. Then the hot-pressing is carried out as described above.

In a further preferred embodiment, the Powder fillings in the hot press fr) pm (13) or (33) mechanical actuation of the ram or the pressure piston (15) instead of the compression described above pressed by hand. This is particularly advantageous in the manufacture of elements in the form of hollow domes, which are advantageous Way by eh mold release agents, such as. B. a colloidal carbon suspension applied to each blank is brushed or sprayed on, are separated from each other.

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Without the initial formation of loosely packed blanks, it is almost impossible to obtain the eventually hot-pressed Elements of the required exact shapes and Sizes to ensure. Without this important step, the special spacers in the mold become angular and the end product is thicker on one side than the other.

In addition, if the spacers are angular, the various elements can come into contact with one another and melt together. Also, when a surfactant is used, there is a solid surface to form a continuous coating to maintain the separability of the elements is essential.

Appropriately, all internal ones are pressed before the heat Surfaces of the dies and the end of the plunger with a mold release agent, e.g. B. a colloidal carbon suspension overdrawn.

The following examples are intended to illustrate the process of the invention in more detail.

example 1

Manufacture of magnesium fluoride washers

80 g of magnesium fluoride powder: with a ⁴ ner capacity. corresponding to minus 150 mesh ^ minus 150 mesh), are in a * "vindrische

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Fora (11), 9.14 cm (3.6 inches) in diameter, inserted and kait-pressed at room temperature at a pressure of 352 kg / cm (SOOO psi) to a body-0.762 cm (0.300 inches) thick . Nine of these kaltverpressten blanks are stacked ä * nn, wherein stainless steel blades of 0.254 mm ^ 0.010 ineh) thickness are placed between individual blanks. Ali ds fs * disks of the same material are placed on the bottom of the fora (21) and on top of the stack.

The Oim (23) is ^{heated to 704 0} C (1300 ⁰ F). Then the pressure piston (2S) kit is pressed onto a ^{stack of blanks at a pressure of 2110 kg / cm 2} (30,000 psi). A vacuum is applied through the line (2?) And the hot pressing conditions are maintained for 30 minutes, after which Argon is introduced through the line (2?) And the furnace is left to room temperature »

The stack of blanks is then removed from the mold. The individual blanks are separated from each other and from the spacers (19) separately, whereupon they can be further processed

Example 2

Formed
Manufacture of IlOüiX from magnesium fluoride

Structure

4 SiOKK made of magnesium fluoride with a diameter of 7.62 cm (3 inches) were cold pressed in sequence

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of 200 g batches produced in the mold (33). The surfaces of the blanks were each after pulling back the plunger (25) and coated with a suspension of colloidal carbon before the next batch is introduced.

After the surface of the last blank had been painted, the plunger was reinserted and the oven and its contents were ^{heated to 704 °} C. (1300 ^° F.). At the same time, mechanical pressure of 2110 kg / cm (30,000 psi) was applied for 30 minutes while a vacuum was drawn in the oven. The furnace was then allowed to cool, the vacuum was released by introducing argon and the stack was removed from the mold by removing the cylindrical portion of the mold. The individual arched parts were then separated from each other

Example 3 Manufacture of zinc sulphide discs

Using the apparatus shown in Fig. 2, 2 Zi; ^ Sulphide disks with a diameter of 16.51 cm (6 * F inches) by successive cold pressing of £ 00 g batches of zinc sulphide powder with a particle size of less than 0.075 mm (the particles passed through a US standard sieve sizes) at 2110 kg / cm ² (30000 psi), the surface of the first blank having been coated with a suspension of colloidal carbon after the plunger was withdrawn and before the second batch was introduced.

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After the second batch had been cold pressed, the furnace and its contents to 899 ⁰ C (165o F ⁰⁾ was heated for one hour and allowed to pass through glow. A pressure of 2110 kg / cm (30,000 psi) was then applied and maintained for one hour while vacuum was maintained. Then became

The furnace cooled, argon introduced and the hot pressed

Slices removed and separated from each other.

Example 4 Manufacture of calcium fluoride discs

Using the apparatus of FIG. 2, three calcium fluoride disks with a diameter of 17.78 cm (7 inches) by sequentially compressing 500 g

less than

Batches of powder with a fineness corresponding to χχκκχ 0.25 mm
S & XXSXXXKMX (minus 60 mesh) made with a hand operated plunger. Solid graphite cut-off wheels 0.635 cm (1/4 inch) thick were placed on the surface of the first and second blanks after they were made.

Then the plunger (25) was inserted into the mold. The furnace and its contents were heated to 871 ⁰ C (1600 ⁰ F).

2
A pressure of 2100 kg / cm (30,000 psi) was immediately applied and maintained for 1 hour.

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The furnace was then cooled and the vacuum was released by introducing argon. Then, the stack was removed from elements by first cylindrical part of the mold has been removed. The individual elements could easily be separated from each other and from the graphite disks.

Example p Manufacture of zinc selenide discs

There were two discs of zinc selenide with one diameter 7 inches (17.78 cm) by placing a 1/4 indi (0.635 cm) thick graphite disc on the bottom of the mold (21) brought a 1000 g batch of zinc selenide powder with a

less than 0.075 mm fineness, corresponding to ftS ** X * l *** «* XX ** tt (minus 200 mesh) placed in the mold on the disk, the powder compressed by pressing a pressure piston by hand, a second graphite disk on the Brought surface of the first batch and this process was repeated with a second 1000 g batch, adding a third graphite disc, and inserting the plunger (25) into the mold and onto the upper graphite disc.

The furnace and its contents were then heated to 1204 ⁰ C (220O ⁰ F), after 1 hour durchg # * lühen left would. then

a mechanical pressure of 1760 kg / cm (25,000 psi) was applied and maintained for 30 minutes.

The procedure was then as described in the preceding examples, 0098 ^ 3/0378

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Example 6 Manufacture of magnesium oxide doped with lithium fluoride

Successively, four 100 g batches of powdered

less than

Magnesium oxide with a fineness corresponding to mxkxxxIüiS 0.075 na.
HXKIKMK (minus 200 mesh) and a content of 11 lithium fluoride at a pressure of 211 kg / cm (3000 psi) in a mold (21) with a diameter of 7.62 cm (3 inches), with on the surface of the blanks a colloidal carbon suspension was spread on the layer. In addition, graphite disks with a thickness of 0.635 cm (1/4 ing) were placed on the bottom of the mold (under the first? * Blank) and on the upper blank.

Then oven and contents were 8? 1 ° € (1600 ⁰ F) heated and S minutes by glow left was created after which a pressure of 141Ü kg / cm (20 qqg psi) for 1 hour.

The following stages correspond to those described in the introductory examples *.

Example 7 Manufacture of Cadmiuihtellurid

Two batches of 150 g of cadraium tellurium were successively

Less than 0.075 ran powder with a fineness corresponding to ttXXMXXXXÜXXXXKKXXX

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2 (minus 200 mesh) at a pressure of 352 kg / cm (5000 psi) cold pressed in a mold (21) with a diameter of 10.16 cm (4 inches), one on both sides with a molybdenum disk coated with a colloidal carbon suspension, 10.16 cm (4 inches) in diameter and 0.051 cm (0.020 inch) thick was applied to the surface of the first blank prior to the second Batch was introduced.

Ten of the blanks were made by heating the oven and contents

to 788 ° C (145O ⁰ F), anneal for 15 minutes and

2 then applying a pressure of 1760 kg / cm (25,000 psi) hot pressed for 30 minutes.

The subsequent stages corresponded to those in the preceding ones Examples described.

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Claims (11)

* 1b96429 claims 1. Method for the simultaneous production of several transparencies polycrystalline optical elements made from uncompacted, crystalline powders of inorganic compounds, characterized in that the powders are used to form a stack of several loosely one above the other, one density having less than 99% of the theoretical density Blanks forms a layer of separating material that cannot be mixed with the blanks between each two adjacent blanks inserts that the stack is hot-pressed under such temperature and pressure conditions that the density after hot pressing, the blanks are above 99 * of the theoretical density and the elements obtained can be seen through * are tig and that the elements obtained are separated from one another. 2. The method according to claim 1, characterized in that the inorganic compound magnesium fluoride, zinc sulfide, Calcium fluoride, zinc selenide, magnesium oxide, cadmium telluride, lanthanum fluoride, cadmium sulfide, zinc oxide, Strontium fluoride, titanium dioxide or cadmium selenide are used. 009833/0378 ORiGiNAL BATHROOM / 3. The method according to claim 1 or 2, characterized in that »that a sheet or a film is used as the separating material. 4. Process according to Claims 1 to 3, characterized in that the separating material is applied in liquid form to the upper surface of the blanks. 5. Process according to Claims 1 to 4, characterized in that that the blanks are introduced into a hollow mold and pressed therein by means of a press ram. 6. The method according to claim 5, characterized in that layers of the release material between the ram and the Stack and between the surface of the hollow mold and the stack arranges. 7. Process according to Claims T to 6, characterized in that hot pressing is carried out at a temperature above 500 ⁰ C (932 ⁰ F), but below the melting point of the inorganic compound and at a pressure above 665 kg / cm * (9500 psi) . 009833/0378 8. The method according to claims 1 to 7, characterized in that the blanks are crystalline by cold pressing
Powder manufactures. 9 · A method according to claims 1 to 8, characterized in that <characterized in that the individual blanks individual by successively introducing batches of to be compressed powder in a HeißpreSSfOXiR ₉ consecutive cold pressing the einselnen batches and introduction of layers of separator material after the cold pressing a batch and before the introduction the next batch forms. 10. The method according to claim 9, characterized in that the individual batches are pressed mechanically or by hand. 11. The method according to claims 1 to 10, characterized in that blanks are used which are in the shape of discs or Have hollow domes. 00 9833/0378 ORIGINAL BATHROOM Blank page