Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements

Definitions

• This invention relates to an improved fluid, light-modulating medium for the projection of self-erasing, rapid decay images in apparatus of the kind wherein a fluid, light-modulating medium is deformed into defraction and/ or refraction gratings by the impression of electron charges thereon as a function of electrical signals corresponding to the images.
• improved electronic projection systems are provided which are capable of projecting a brighter image.
• Apparatus employing such a fluid, light-modulating medium is described, for example, in US. Pat. 2,943,- 147-Glenn, Jr., wherein is disclosed a projection system comprising an evacuated glass envelope containing an electron gun for producing an electron beam, which is deflected in a rectangular raster over the surface of a light-transmitting, electron-deformable, light-modulating medium contained within a portion of the transparent glass envelope.
• the electron beam is modulated, as by a television signal applied to the deflection means.
• the deflected electrons strike a portion of the light-modulating medium in the raster area traversed by the electron beam, and these electrons are electrically attracted to a conductive coating over which the light-modulating medium is supported.
• these electrons strike the surface of the medium, they produce deformations in this surface with the amplitude of the deformations being a function, along with other parameters, of the number of electrons deposited by the electron beam at various points over the surface of the raster area.
• the amplitude of these deformations are a function of the electron beam modulation. Repetitive rates of more than one image per second are employed and this is possible because of the rapid decay of each image such that the same area of fluid is employed for the formation of a quick sucession of images.
• the fluid, light-modulating medium is a thin layer of light-transmittable fluid in which the electron beam forms phase diffraction gratings and/or refraction gratings in the form of alternate hills and valleys caused by the deforming effect of the electron beam.
• the adjacent valleys are spaced apart by a predetermined distance such that each portion of light incident on a respective small area or point of the medium is deviated in a direction orthogonal to the direction of the valleys.
• the intensity of the deviated light is a function of the depth of the valley and diminishes as autoerasure of the deformation occurs wherein the hills and valleys just diminish and the fluid is ready for the writing of a new image.
• CQT critical quieting thickness
• the depth of fluid at which the CQT occurs becomes manifest in the following manner.
• each fluid has its own capacity to conduct electric charges impressed on its surface through the fluid to the ground plane base, i.e., the conductive layer. It is believed that this charge transfer occurs both by electrical conduction phenomena and by various flow patterns coordinated with the raster lines. If the thickness of the fluid is greater than the CQT, flow patterns uncoordinated with the raster lines or with the modulated signals are generated in the fluid. These uncoordinated flow patterns deform the surface resulting in the deviation of light not resulting from signal modulation. This phenomenon is known as optical noise or noise.
• this uncoordinated flow occurs as the current density of the electron beam is increased from zero to some value beyond which a sudden and widespread initiation of uncoordinated flow occurs in the fluid.
• the fluid thickness at this depth is at the CQT for this value of current.
• Operation with a fluid thickness of less than the CQT value is desirable because the noise referred to hereinabove is destructive of the signal-modulated image. More effective operation, greater flexibility for this system and an improved image production are achieved by increasing this value of the CQT whereby operation with a thickener layer of fluid without noise is made possible.
• the preferred combination was a polybenzyltoluene fluid in which polystyrene was dissolved.
• the amount of polystyrene that had to be dissolved to give the desired viscoelastic behavior was dependent upon the linearity of the polystyrene as well as upon its molecular weight. Because of this variation, they disclose a very simple test for determining whether or not a particular fluid had viscoelasticity by dipping a pointed probe into the liquid and then withdrawing it.
• the liquid does not have their requisite viscoelasticity, no connection remains between the end of the probe and the surface of the liquid upon withdrawal of the probe. If the liquid does have the desired viscoelasticity, a thread or filament having a length-to-diameter ratio of about 100 to 1, or greater remains, connecting the probe and the surface of the liquid as the probe is moved away from the surface. Commonly such threads could be drawn to lengths of over /2 inch. As a practical consideration, the thread test is conducted at the operating temperature at which the fluid is to be used in the projection system.
• the polybenzoyltoluene fluid can be the polybenzyltoluene fluid obtained by condensing benzyl chloride with toluene in the presence of a Friedel- Crafts catalyst to produce a fluid having a viscosity of at least 100 centistokes (cs.) at 25 C. which is separated from the lower boiling fractions by distillation.
• a fluid is described in the above-referenced Plump Pat. 3,288,927.
• a preferred and improved polybenzyltoluene is prepared by condensation of benzyl alcohol with toluene in the presence of an acidic catalyst as described in the copending application of Charles E. Timberlake, Ser. No. 92,178, filed Nov. 23, 1970 and assigned to the same assignee as the present invention. This material, likewise, is distilled to provide a fraction having a viscosity of at least 100 centistokes at 25 C.
• Thes fluids are modified by dissolving an amount of polystyrene sufficient to attain the desired viscoelastic behavior in the fluid. Simultaneously, or as a separate step,
• tris(3-phenylpropyl)phosphat is dissolved in the fluid.
• the amount of the latter material is determined by the properties one desires to obtain. Very small amounts in the order of 0.1-1 percent will have some effect on increasing the CQT of the fluid but still further gains are obtained by use of still larger amounts. However, the further gain in CQT must be measured against the fact that larger amounts of the tris(3-phenylpropyl)phosphate decrease the viscoelastic nature of the fluid. This can be compensated to some extent by increasing the amount of polystyrene added or the molecular weight of the polystyrene used can be increased.
• the amount of polystyrene dissolved in the polybenzyltoluene is best described as that amount suflicient to provide viscoelastic behavior to the fluid and the amount of tris(3-phenylpropyl)phosphate is best described as the amount sufficient to increase the critical quieting thickness of the fluid but insufficient to destroy the viscoelastic behavior of the fluid. There is no need to use larger amounts of either of these materials than is required to obtain the desired properties.
• EXAMPLE 1 A polybenzyltoluene fluid in which there was dissolved 2 percent by weight polystyrene was used as the base fluid, light-modulating medium. Using the procedure given in U.S. Pat. 3,541,992, the CQT of the base fluid was found to be 12.711. at 1000 centistokes. When 4% tris(3-phenylpropyl)phosphate was dissolved in this same base fluid, the CQT was increased to 16p. at 1000 centistokes, an increase of 26%.
• Example 2 When Example 1 was repeated, except using a different polybenzyltoluene in which 2% polystyrene was dissolved, the critical thickness increased from 13.1 1 at centistokes to 17.3, at 1000 centistokes, an improvement of 32%, by dissolving 4% by weight tris(3-phenylpropyl) phosphate in the polystyrene modified fluid.
• the increase in the CQT obtained by this invention permits these fluid, light-modulating mediums to be used in a thicker layer in the electronic projection systems thereby resulting in an improved system because of the increased brightness of the image which can be projected therefrom.
• a composition of matter consisting essentially of a polybenzyltoluene fluid having a viscosity of at least 100 centistokes at 25 C. in Which there is dissolved a suflicient amount of polystyrene to provide viscoelastic behavior to said fluid and a sufficient amount of tris(3- phenylpropyl)phosphate to increase the critical quieting thickness of said fluid but insuflicient to destroy the viscoelastic behavior of said fluid.
• a fluid, light-modulating medium for use in apparatus in which a thin layer of said fluid, light-modulating medium is supported on a conducting plane located relative to means for producing an electron beam so that said beam is directed at said plane to build up charge in said fluid, light-modulating medium, which charge produces self-erasing deformation in the surface of said layer, each said deformation acting to dilfract light directed at said layer from a light source in a light optical system, the
• diffracted light being projected by the optical system as a 15 function of each deformation to form self-erasing, rapid, decay images, the improvement wherein said fluid is the composition of claim 1.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Transforming Electric Information Into Light Information (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)
• Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22965227

Family Applications (1)

Country Status (5)

Family Cites Families (4)

• 1972
  • 1972-05-18 US US00254696A patent/US3766081A/en not_active Expired - Lifetime
• 1973
  • 1973-05-07 CA CA171,113A patent/CA998523A/en not_active Expired
  • 1973-05-15 JP JP5325573A patent/JPS5620524B2/ja not_active Expired
  • 1973-05-16 DE DE2324652A patent/DE2324652C2/de not_active Expired
  • 1973-05-18 FR FR7318130A patent/FR2185036B2/fr not_active Expired

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