US3715494A

US3715494A - Projection system

Info

Publication number: US3715494A
Application number: US00110519A
Authority: US
Inventors: E Perlowski
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-01-28
Filing date: 1971-01-28
Publication date: 1973-02-06
Anticipated expiration: 1990-02-06
Also published as: FR2123497A1; FR2123497B1; GB1366320A; DE2203576A1; CA956494A

Abstract

An improved electronic image projection system having a container with a conducting interior and a deformable medium in the container which decreases in resistivity with decreases in thickness in the presence of electrical charge on the surface of the medium is provided by using as the deformable medium a polymeric material having as an additive a 9,10-anthracene derivative.

Description

United States Patent m1 Perlowski, Jr.

[ 1 Feb. 6, 1973 1 1 PROJECTIQN SYSTEM [75 Inventor: Edward F. Perlowski, ,Iiz, Baldwinsville, N.Y [73] Assignee: General Electric Company [22] Filed: Jan. 28, 1971 21 Appl. No.: 110,519

[51] Int. Cl. ..G02b 5/22, H04n 5/72 [58] Field of Search.....252/380, 300, 407, 62.1, 399; 176/33, 40; 117/333; 250/108; 178/7.5 D;

[5 6] References Cited UNITED STATES PATENTS 2,943,147 6/1960 Glenn ..'...l78/7.5 D

3,125,634 3/1964 Murray ct a1. .178/7.5 D

3,125,635 3/1964 Murray et al.. 178/7.5 D

3,125,636 3/1964 Klebe ..l78/7.5 D

3,125,637 3/1964 Klebe ..178/7.5 D

3,288,927 11/1966 Plump .....l78/7.5 D

3,317,664 5/1967 Perlowski .....l78/7.5 D 3,317,665 5/1967 Perlowski ..178/7.5 D

ELECTRON GUN GTHER PUBLICATIONS Chandrosset al iA'c's', 87:14, m 20, 1965 pp. 3,359-3,260 Birks et al., Proc. Roy. Soc. (London), Ser. A,

275( 1360), 135-148( 1963) and Chemical Abstracts,

Vol. 59, p. 5952a, (1963).

Chemical Abstracts, Vol. 64, p. 6898f, (1964), (T.D.S. Hamilton).

Chemical Abstracts, Vol. 65, p. 1,720f, (1966), (Himbuch).

Chemical Abstracts, Vol. 67, p. 103,774t,(1967), (Parker et al.).

Primary Examinerl.eon D. Rosdol Assistant Examiner-Irwin Gluck Attorney-Marvin Snyder [57] ABSTRACT An improved electronic image projection system having a container with a conducting interior and a deformable medium in the container which decreases in resistivity with decreases in thickness in the presence of electrical charge on the surface of the medium is provided by using as the deformable medium a polymeric material having as an additive a 9,10- anthracene derivative.

6 Claims, 2 Drawing Figures SCREEN PATENTEDFEB 6 1975 ELECTRON GUN SCREEN 35 INVENTOR EDWARD F. PERLOW SKI ,JR.

ms ATToflNEY.

PROJECTION SYSTEM This invention relates to a projection system of the electronic type, and more particularly to an electronic image projection system having a container with a conducting interior and a deformable medium in the container that decreases in resistivity with decreases in thickness in the medium, the medium having as a radiation mode depressor substituted 9,10-anthracene.

There is described in U.S. Pat. No. 2,943,147, June 28, 1960, assigned to the same assignee as the present invention, a projection system of the above type employing adeformable medium having a high resistivity which is responsive to a velocity-modulated electron beam. Generally speaking, this projection system, which is illustrated in FIG. 1 of the drawing, comprises an evacuated glass envelope containing an electron gun 1 l for producing an electron beam 13 and deflecting it in a rectangular raster over the surface of a light transmitting deformable medium 15 which is within a portion 17 of the transparent container. An enlarged view of this portion of the assembly is shown in FIG. 2. The beam 13 is preferably velocity-modulated by a television signal applied to the deflection means (not shown) in the electron gun ll. Deformable medium 15 has a central portion 19 of decreased thickness which is deformations are a function of the number of electrons deposited by the beam 13 at the various points on the surface of medium 15. Thus, the amplitudes of these deformations are a function of the modulated electron beam 13.

The deformations on the surface of medium 15 are utilized to diffract light from .a source 23 in an optical system including a lens 24 which projects an image of light source 23 on the surface of medium 15 through a bar and slit system 25. Another lens 29 images the slits of system 25 on the bars of another bar and slit system 31 if there are no deformations on the surface of deformable medium 15. However, any deformations on such surface diffract the transient light so that it passes through the slits in the system 31 with an intensity that corresponds to the amplitudes of the deformations and hence the amplitudes of the applied modulating signal such as a television signal. The light passing through system 29 is imaged by a projection lens 33 on screen 35 by means of mirror 37.

If a conventional deformable medium is utilized at 15 in the illustrated system, the average charge density produces a force on the medium 15 that overcomes the surface tension from the excess medium outside the raster area and decreases the portion 19 of medium 15 to zero thickness. Under such conditions, no deformations can be formed and the system becomes inoperative until the medium is replaced. The above patent teaches that if the medium has the property of decreasing in resistivity with decreasing thickness, portion 19 does not decrease to zero thickness under the pressure of the charges but maintains a thickness which is a function of the magnitude of charge density on the surface of the medium 15. With decrease in resistivity, the

time constant is decreased for the passage of leakage current from the surface of deformable medium 15 to the conducting coating beneath it. This results in an increase in leakage current, decreasing the charge densi-- ty on the surface of the medium 15 and somewhat relieving the pressure. Eventually, an equilibrium condition is reached in which the pressure from the charges on the surface of the medium equals the pressure from the surface tension on the excess medium surrounding the raster at which the thickness at this equilibrium condition'is maintained. The charge density on the surface of the medium never decreases to zero because of such leakage because it is continually being replaced by electrons from beam 13.

The deformable compositions described in the aforesaid U.S. Pat. No. 2,943,147 as suitable for the medium are required to be transparent, be capable of withstanding electron bombardment without significant decomposition, have a viscosity at the operating temperature (between about 25 and 150 C) of approximately 100 to 50,000 centistokes, and the deformable composition must not decompose the conducting coating. The medium must also have a volume resistivity that varies within the range of approximately 10 to 10" ohm-cm., with the average resistivity at the stable thickness being approximately 10 ohm-cm.

Among the deformable media or fluids described in I the above patent are beeswax, methyl silicone fluids,

methyl silicone fluids containing up to 5 percent of phenyl silicones, methylphenyl silicones containing an average of two methyl and phenyl groups per silicon atom in which the mole ratio of methyl groups to silicon atoms is greater than 0 and less than 2, etc. However, it has been found that these deformable fluids are not as stable as one would desire because under the influence of an electron beam, the deformable medium or deformable fluids tend to increase in viscosity and with continued use in the projection system described above, the viscosity increases to a point where gel parti 'cles begin to form and the deformable medium ultimately gels. it is quite obvious that the apparatus can no longer be used with a gelled medium which will not suitably decrease in thickness. 1

The shortcomings of the above media were alleviated by providing typically very specific Friedel-Crafts reaction products of benzyl chloride and aromatic materials such as biphenyl, naphthalene, toluene and benzene, including substituted materials of these types. Typical such projection systems are described, for example, in U.S. Pat. No. 3,317,664 relating to media which are the reaction product of benzyl chloride and naphthalene and in U.S. Pat. No. 3,317,665 relating to the Friedel- Crafts reaction product of benzyl chloride and'biphenyl material and in U.S. Pat. No. 3,288,927 relating to such reaction products of benzyl chloride and benzene, toluene, etc., the above patents being assigned to the same assignee as the present invention.

While material provided by the teaching of the immediately preceding patents had a desirable long-lived suitable viscosity, it was found that under continuous electron bombardment during operating conditions, and particularly at current densities of about 5 microamperes per square inch and over, perturbations or disturbances appear in the raster which detract from or destroy the image. Such disturbances are commonly known as radiation modes and considered to result from localized charge concentration phenomena and/or radiation damage on the surface of the writing medium or fluid.

From the above it will be seen that there is a need for materials which can be used as medium which are not only characterized by long-lived and suitable viscosity under the radiation effects of electrons from beam 13 but which at the same time are resistant to local radiation damage and perturbations of the medi um surface which detracts from, or destroys, clarity of the image. It is therefore a principal object of the invention to provide medium materials which are possessed of desirable long life under irradiation and which are resistant to surface radiation effects.

It has been unexpectedly found that radiation damage to the surface of the writing medium canbe effectively suppressed by addition to the medium of substituted 9,10-anthracene derivatives having the following general formula where each of R and R is selected from the group con sisting of phenyl, benzyl, xenyl, naphthyl and the like. While it is not the present intention to be bound by any theory as to the mode of operation of the present additives, it is believed that they act as a sump for a large portion of the electronic energy impinging upon the light valve or medium surface, the major portion of the beam energy being diverted from the comparatively weak intra-molecular bonds of. the polymeric medium or writing fluid to the more stable anthracene nucleus, such diverted energy then being dissipated in less harmful forms such as heat, and light as opposed to the rupturing of chemical bonds or to the establishing of charged convection cells. lt has been found that the present invention is applicable to light valve materials or writing fluids in general, particularly those having a viscosity at the operating temperature of between about 25 and 150 C of from about 100 to 50,000 centistokes and a volume resistivity ranging from about 10 to l0 ohm-cm. It is thus particularly applicable to the light valve fluids mentioned in the above patents which are incorporated herein by reference.

The amount of the above anthracene material required is relatively small and depends upon the degree of radiation mode suppression desired. Generally speaking, taking this factor into consideration along with the writing current density to be used, critical depth, mobility and the like, amounts of from about 0.1 percent to 3.0 percent by weight of anthracene additive have been found useful.

The following example will illustrate the practice of v the invention, it being realized that it is to be taken as exemplary only and not as limiting in any way.

EXAMPLE There was added to a polybenzyl toluene material exemplified by the above U.S. Pat. No. 3,288,927, 2 percent by weight of 9,10-diphenyl anthracene, the writing fluid so prepared being incorporated in the illustrated apparatus and operated at a current density of 5 microamps per square inch. It was found that even after 163 microamp minutes per square inch of operation, the image was clear and free of disturbances. On the other hand, writing fluids of the U.S. Pat. No. 3,288,927 polybenzyl toluene type used without the anthracene additive are characterized by image clarity disturbing radiation modes appearing on the raster or fluid surface after less than l0 microamp minutes per square inch of operation. Additionally, the resulting modification to the charge conduction process by the 9,l0-diphenyl anthracene additive was found to reduce perturbations in the surface of the fluid and improve overall picture quality.

The particular diphenyl anthracene used had a vapor pressure of 2.3 X 10 Torr at 25 C and l X 10* Torr at 35C.

There is provided, then, by the present invention an improved electronic projection system. As described, the deformable writing medium, by reason of the prescribed additives, results in improved projection system operation and picture quality and is capable of operation over long periods of time at relatively high current densities with little or no loss in image clarity caused by radiation damage to the writing medium surface. lt will be realized that obvious modifications of the invention may be made without departing from the spirit or scope thereof.

What is claimed is: v

l. A projection system comprising a container having a conducting interior, a deformable medium in said container having as a radiation mode suppressant a 9, lO-anthracene derivative represented by the general formula where R and R are each selected from the group consisting of phenyl, benzyl, xenyl, and naphthyl, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject said medium to a deforming force to produce deformations in the surface of said medium, a light source, and an optical system for projecting light from said source as a function of the deformations in the surface of said medium. 7

2. A projection system as in claim 1 wherein R and R are phenyl groups so that said radiation mode suppressant comprises 9, IO-diphenyl anthracene.

3. A projection system as in claim 1 wherein R and R are benzyl groups so that said radiation mode suppressant comprises 9, 10-dibenzyl anthracene.

4. A projection system as in claim 1 wherein R and R are xenyl groups so that said radiation mode suppressant comprises 9, lO-dixenyl anthracene.

5. A projection system as in claim 1 wherein R and R are naphthyl groups so that said radiation mode suppressant comprises 9, IO-dinaphthyl anthracene.

6. A projection system as in claim 1 wherein said radiation mode suppressant is selected from the group consisting of 9,10-diphenyl anthracene, 9,10-dibenzyl anthracene, 9,10-dixenyl anthracene, 9,10-dinaphthyl anthracene, and mixtures thereof.

Claims

1. A projection system comprising a container having a conducting interior, a deformable medium in said container having as a radiation mode suppressant a 9, 10-anthracene derivative represented by the general formula

2. A projection system as in claim 1 wherein R and R'' are phenyl groups so that said radiation mode suppressant comprises 9, 10-diphenyl anthracene.

3. A projection system as in claim 1 wherein R and R'' are benzyl groups so that said radiation mode suppressant comprises 9, 10-dibenzyl anthracene.

4. A projection system as in claim 1 wherein R and R'' are xenyl groups so that said radiation mode suppressant comprises 9, 10-dixenyl anthracene.

5. A projection system as in claim 1 wherein R and R'' are naphthyl groups so that said radiation mode suppressant comprises 9, 10-dinaphthyl anthracene.