JPS59215096A - Method for recording information in ferroelectric polymer - Google Patents

Abstract

PURPOSE:To enable the economical recording and readout of information by simple handling by applying an electric field to a ferroelectric vinylidene fluoride polymer to store information in a polarized state. CONSTITUTION:A photoconductive layer 2 is superposed on a storage element 1 made of a vinylidene fluoride polymer which is a high molecular ferroelectric substance, and they are held between transparent electrodes 4, 4' to form a laminate. By heating the laminate with light emitted from a flash lamp 6, the temp. of the element 1 is pulsatively raised to clear the whole surface, and voltage is applied between the electrodes 4, 4' of the laminate in an unpolarized state. When a light beam 3 is projected on the selected part S of the upper plane of the laminate, the selected part of the film 2 just under the part S is made electrically conductive, and an electric field is applied from a power source to the selected part S' of the element 1 between the electrode 4 and the selected part of the film 2. The selected part S' of the element 1 is set in a polarized state, so it holds information even after removing the light beam and the electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of recording information using a polymeric ferroelectric material.

JP-A No. 55-126905 discloses that information can be written to a ferroelectric memory material by applying residual polarization using an electric field. It is described that information can be read out using the pyroelectric effect caused by heat, and examples of polymeric ferroelectric materials that are suitable as memory materials include vinylidene fluoride (80-30 cm) and ethylene fluoride (20-70 cm). A vinylidene trifluoride copolymer containing a molar ratio is mentioned.

In this way, an electric field is used to polarize the ferroelectric memory material (vinylidene fluoride-trifluoroethylene copolymer) and information is written into it using the pyroelectric effect caused by light or heat. It has been proposed to read the

Figure 1 shows how the polarization state of a copolymer of vinylidene fluoride and ethylene trisulfide changes as the applied electric field changes.

Furthermore, FIG. 2 shows that the polarization state changes with temperature.

However, it is not known that the polarization state of such materials changes rapidly in response to changes in the applied electric field, and for this reason, it is difficult to industrially store information on such materials. It was unthinkable to use it for reading data.

Furthermore, in order to write a large amount of information into a single element made of such a material, a large number of writing electrodes are inevitably required, which is expected to be very inconvenient to handle. .

An object of the present invention is to provide a method for recording and reading information on vinylidene fluoride polymers, which is easy to handle and economical.

The present invention applies the applied voltage to vinylidene fluoride polymers, especially vinylidene difluoride and ethylene trifluoride copolymers.
The basis for this is the discovery that the polarization in response to - is fast as shown in Figure 3. In FIG. 3, the horizontal axis represents the logarithm of time (seconds), the vertical axis represents the polarization and the time logarithmic differential of the polarization, and the subscripts on the data represent the applied electric field.

In the present invention, vinylidene fluoride polymers refer to vinylidene fluoride homopolymers and vinylidene fluoride polymers containing 50 polymers of vinylidene fluoride.
It refers to a vinylidene fluoride copolymer containing at least Examples include copolymers of ethylene trifluoride and ethylene trifluoride chloride, and copolymers of vinylidene fluoride, ethylene trifluoride, and propylene hexafluoride. Among these materials, a copolymer of vinylidene fluoride and ethylene trifluoride is the most preferred material for the purpose of the present invention.

FIG. 4 shows an example of a method for attaching information in the form of a polarized state to the memory element 1 according to the present invention. A storage element 1 is placed thereon, a photoconductive film 2 whose resistance becomes low F when irradiated with light is placed thereon, and a transparent electrode 4' is placed on top of the photoconductive film 2.
The structure is such that a voltage can be applied between the transparent electrodes 4 and 4'. In order to write and store information, the flash run 7"6'f: is ignited in advance, and the light emitted heats the product 1, raising the temperature of the storage element 1 to the temperature T shown in FIG.
1.9 pulses to clear the entire surface of the memory element 1 into an unpolarized state, and then apply a voltage '' between the transparent electrodes 4 and 4' integral with the memory element 1. When the light beam 3 is projected onto the selected part of the upper plane of the body, the fifth
As shown in the figure, selected portions of the photoconductive film 2 directly below the selected portions S of the transparent electrode 4' are rendered conductive by the projection of the light beam. And transparent i! Pole 4 and photoconductive film 2
An electric field indicated by E1 on the horizontal axis in FIG. 1 is applied to the selected portion S' of the memory element interposed between the selected portion of the power source and the selected portion of the memory element. As a result, the selected portion S' of the storage element 1 remains polarized and retains information even after removal of the light beam and electric field.

The following is a specific method for reading information arranged in this way.

(a) Light is passed through a storage element that records information in the form of an arm turn, which consists of a polarized part and an unpolarized part, and the phase difference δ between the light that passes through the polarized part and the light that passes through the unpolarized part is calculated. (b) Project light onto the storage element and detect the polarization state using refraction at the boundary between the polarized and unpolarized parts of the storage element: (c) Polarized light Light is projected onto the memory element installed at an angle, and the polarized state is detected by detecting the elliptically polarized light that changes in the polarized part using an analyzer: (d) The memory element is locally heated, and the heated part is placed at one end of the element. The polarization change caused by the temperature change at that time is converted from the change in the current flowing between the electrodes placed between the elements to convert the spatially stored information into a time series and generate electrical information. to be detected.

The information recording method according to the present invention does not require a write electrode and can accurately and quickly write all information using the tip of a light beam, making it possible to put into practical use large-capacity disk memories made of polymeric ferroelectric materials.

In FIG. 6, a light beam 3 is projected onto a large-capacity disk memory consisting of a rotating storage area 1 and 8, and information is read out by a light beam 13. An example of a large-capacity disk memory sm configured to read information with a detector 14 is shown.

m7 figure F! As shown in FIG. 7, an embodiment of the incoherent-coherent conversion element stores information of an input image 23 illuminated with incoherent illumination light 22 through a convex lens 24 in a memory element stack 8.

During reading, the coherent light 21 is passed through the polarizer 11, the resulting polarized light 25 is projected onto the storage element stack 8, and only the elliptically polarized light that has passed through the polarized portion of the storage element 1 is sent to the analyzer 1.
2 to obtain a coherent image.

As described above, t'f? according to the present invention? Since a light beam is used for @'s writing, there is no need for a complicated electrode configuration, and since a photoconductor is used, writing is possible even with weak light. According to the present invention, a very low-cost polymeric material can be used as a memory element, and since it is not affected by surrounding magnetism, it can operate reliably even under a magnetically adverse environment. It can also be used for cash cards, etc., which are safe even if they touch keys.

[Brief explanation of drawings]

Figure 1.2 shows the polarization characteristics of polymeric ferroelectric materials as a function of electric field and temperature, respectively. Fig. 3 is a response curve of polarization to an electric field, Fig. 4.5 is an explanatory diagram of the method of writing information in the form of polarization according to the present invention, Fig. 6 is an example of application to a large-capacity disk memory, and Fig. 7 is An example of an incoherent coherent y-sparing element is shown. (In the figure, ]... Memory element, 2... Photoconductive film, 4.4'... Transparent electrode, 8
...Laminated body, 3°13...light beam) Patent applicant: RIKEN Daikin Industries, Ltd. Kazuo Wakasugi, Commissioner of the Patent Office 1. Case Description 1982 Patent Application No. 89. '(No. 78 No. 2, Title of the invention, Method for recording information on polymeric ferroelectric materials 3, Relationship to the case of a person who makes a illicit action Applicant's name (679) RIKEN 4, Agent 5, Amendment Date of order Vol. 7, Supplemental content 1, Page 7 of the specification, line 11, "Only detected by analyzer 12" is corrected to "detected by analyzer 12." 2. Figure 7 is attached. Correct as follows.

Claims (1)

[Claims] A photoconductive layer is layered on a memory element made of vinylidene fluoride polymer, which is a ferroelectric polymer, to form a laminate, and a voltage is applied to the layer to form a laminate, and a selected portion of the photoconductive layer is exposed to light. A method of recording information in a polymeric ferroelectric material, the method comprising recording information by projecting a beam and polarizing selected portions of a storage element.