Sept. 10,1946. 7 MHYMAMR " - , 2,407,280‘ ’ MOLD FOR USE IN THE MANUFACTURE OF OPTICAL ELEMENTS Filed Sept. v2, 1942v ‘ “ ‘ BY ‘ IN\%ILOR. m 2,407,280 Patented Sept. 10, 1946 211407.280‘; ‘ ‘ MoL-D’FoRZUsEtN'?HE JI'FAGTUREJoFW OPTICAIJFELEMENTS‘K @SSiE?QiIiW-Q . Mat Po amidConpora' CambridgcoWlS$¥ on; Cambridge, Mass.,-,a.cor-. pit'ratiaa.or'nelawareg Application‘S'eptEmbeirZ, 19dgltserial<N6£>45?§031ir ' sic'laini'se (01. 1893911.. This invention relates-9 can:improvedwmoldzfori usein themanufactureiof: optical elements formed; of. polymerized? synthetic. plasti'ospresinsr and :like: materials.v . ; surfaces; which cantheyrepeatedlyi'reeused, and? thesei'elements ‘P should- preferablyyv be~~bonded~ itoe ‘i gether and maintained :inliproper'position :bye m adhesive. or : aicementéwhichtmay;‘be-readilygape An object of the inventionisrtotprovideza mold; temperatures to‘ Which'tthe ‘moldsv are“ ’ subjected-r. ofithe; character? describediscomprising a. plurality of. elements having;opticallysmooth molding sure ‘ facesand. a water-soluble: cement for sealingstlieis during‘athe-polymerization'ofthe:plastic/material“~ therein. With plastic'materialsrof .therclass-‘heree “ tofore described polymerizatiomtenrpe'rature‘siarea ingi them. ?xedly-‘in 'position'» during thertmoldin‘g 10.. preferably maintained not greatlje irr'excess‘roftgo joints; between; said imoldinggelement‘s : 811d~§h01de process.< degrees-0.. , , h p . i . . ' V . .. . . Another.v obj ecteofyi the :inyention qis‘ 'theeprovih: sion of a water-solubl wcementwhichis resistant. to temperatures at: which the polymerization process takes place. Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the prod uct possessing the features, properties and rela Thiseinvention contem ilategthe-userof:aewatere ‘ soluble rand-J51‘ preferably; a"! refractory cementli as: 1 the material employedi-in sealing and- bonding to?) 15 gether the mold walls. The mold may be assem bled by placing the glass wall elements in a suit able J'i'g, and while they are held in position in the jig, for example by leaf springs or other means, they are sealed along their adjacent edges and cemented together by applying thereto the tion of elements which will be exempli?ed in the preferred adhesive or cement in the form of a following detailed disclosure and the scope of the thick paste. The cement may then be rapidly application of which will be indicated in the dried and it quickly sets and hardens. claims. The drawing illustrates in perspective a por For a fuller understanding of the invention reference should be had to the following detailed 25 tion of a mold for use in themanufacture of prisms. The mold walls ID are shown as made description, taken in connection with the accom of glass, the preferred material, and they are panying drawing, which represents partially in bonded together and held in position by the water perspective and partially in section one embodi soluble cement [2. A bottom plate I4 is also held ment of the invention. There is today a pressing demand for large 30 in position by the cement I2. A preferred material for use as the bonding quantities of optical elements, ‘such as prisms, material in the present invention is the refractory lenses and the like. This invention is concerned water-soluble cement sold under the trade name with the provision of molds adapted for use in “Insalute.” Other suitable cements may be em the production of such elements from synthetic plastic or resinous materials which are introduced 35 ployed. For example, a mixture of sodium sili cate with a suitable ?ller, such as wood flour, into the mold in a partially polymerized or mono pumice or the like has been found satisfactory. meric state and then polymerized substantially In this instance the ?ller acts primarily to prevent completely and until they form hard, transparent shrinkage of the sodium silicate as it hardens in optical elements. Materials which have been found particularly useful in the production of 40 contact with the mold walls and thus prevents such molded plastic optical elements are cyclo strain and distortion thereof. Either of the ce hexyl methacrylate, styrene, methyl methacrylate, ments described may be removed readily from the and similar materials. ‘ ‘ molds after the polymerization of the plastic A considerable percentage of the cost of the therein has been completed by immersing the molded optical element resides in the cost of the 45 mold in water, as the cements are water-soluble. mold. The light-transmitting surfaces of the ele It is to be understood that other water-soluble ment are preferably molded in contact with cements which are adapted to withstand the glass elements having optically smooth surfaces. molding temperatures may be used, and all such and these are expensive. It will be apparent that in the production of large quantities of molded 50 cements are to be deemed as falling within the scope of the invention. ’ optical elements it is highly desirable that the It should perhaps be pointed out that with the mold may be readily and rapidly assembled and use of water-soluble cements as bonding mate that it should be easily removed from the ?nished rials in molds employed for the purpose de article. It should comprise elements, and par scribed, a preferred plastic material for use in ticularly those elements having optically smooth 2,407,280 4 connection with the production of the molded optical elements is one which shows very little substantially optically smooth, and a water-solu ble cement bonding said walls together and com water absorption when polymerized, and cyclo prising sodium silicate. hexyl methacrylate is to be preferred in this connection, as its water-solubility in the sub 2. A mold for use in the formation of an op tical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of mold walls having molding sur faces substantially optically smooth, and a water soluble cement bonding said walls together and stantially completely polymerized state is ex tremely low. Other materials which may be satisfactorily employed in the production of molded optical elements in the manner described, and which are to be preferred when molds em bodying‘the present invention are employed, be cause of the low water absorption of their poly mers, are styrene, homologues of styrene, methyl 10 comprising sodium silicate and a ?ller.‘ 3. Amold for use in the formation of an opti cal element of polymerized synthetic plastic ma terial or the like, comprising, in combination, a cyclohexyl methacrylate, menthyl methacrylate, ‘plurality of mold walls having molding surfaces phenyl methacrylate and homologues of phenyl 15 substantially optically smooth, and a water-solu methacrylate. ble cement bonding said walls together, said Since certain changes may be made in the cement comprising also a water-insoluble ?ller. above product and different embodiments of the invention could be made without departing from its scope, it is intended that all matter contained 20 in the above description or shown in the accom panying drawing shall be interpreted as illus trative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all the generic and 4. A mold for use in the formation of an opti cal prism of polymerized synthetic plastic mate rial or the like, comprising, in combination, a plurality of glass mold walls forming a pris matic mold cavity and having molding surfaces substantially optically smooth, and a water-solu ble cement bonding said walls together and com prising sodium silicate. speci?c features of the invention herein de 26 5. A mold for use in the formation of an opti scribed, and all statements of the scope of the cal prism of polymerized synthetic plastic mate invention which, as a matter of language, might rial or the like, comprising, in combination, a be said to fall therebetween. plurality of glass mold walls forming a prismatic What is claimed is: 30 mold cavity and having molding surfaces sub 1. A mold for use in the formation of an opti stantially optically smooth, and a water-soluble cal element of polymerized synthetic plastic ma cement bonding said walls together and compris terial or the like, comprising, in combination, a ing sodium silicate and a ?ller. plurality of mold walls having molding surfaces - MARK HYMAN, JR. Certi?cate of Correction Patent No. 2,407,280. ' September 10, 1946. MARK HYMAN, JR. It is hereby certi?ed that error appears in the printed speci?cation of the above numbered patent requiring correction as follows: Column 4, line 33, after “?ller.” and before the signature to the speci?cation insert the following claim 6. A mold for use in the formation of an optical element of poly merized synthetic plastic material or the like, comprising, in combina tion, a plurality of mold walls having molding surfaces substantially optically smooth, and a water-soluble cement bondin said walls together, said cement comprising also a water-insolub e ?ller and showing substantially no contraction upon hardening. and in the heading to the printed speci?cation, line 8, for “5 claims” read 6‘ claims; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in'the Patent Of?ce. Signed and sealed this 22nd day of July, A. D. 1947. [Hm-1 LESLIE FRAZER, “We ‘ i _ First Assistant Oommissz'omwofPatents.