Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
  • G02F1/1514—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material
  • G02F1/1523—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material comprising inorganic material

Definitions

• the invention relates to an electro-optical cell, in particular for display purposes, with a working electrode whose optical properties can be controlled electrically, a counter electrode, an ion conductor arranged between the two electrodes and means for applying an electrical field or an electrical current.
• the cell can also be provided with a reference electrode.
• electro-optical cells whose electrochromic effect consists in that the absorption properties of the electrochromic layer for continuous light are changed by applying an electric field or by the action of an electric current such that this layer is transparent to light, for example in a switching state and is completely or partially impermeable in the other switching state.
• the absorption in the electrochromic material is usually frequency selective so that colored ads can be created with the effect.
• Electro-optical cells of this type based on the effect of electrochromy are described, for example, in Green, M. et al. in Solid Films, 38 (1976) 89-100; in Chang, JF et al., Journal of the Electrochemical Society, 122 no.
• Electro-optical devices based on the known electrochromic effect mentioned above require a relatively high power at higher switching frequencies, typically around 100 times the values at 1 Hz that are usual for liquid crystal field effects.
• the invention is based on the object of providing an electro-optical cell which is based on an effect which differs from the known electrochromic effect and therefore does not have the disadvantages of the known electrochromic effect, but does have its advantages.
• an electro-optical cell of the type mentioned at the outset which is characterized in that the working electrode consists of an intercalatable layer structure.
• the working electrode consists of graphite.
• graphite is intended to encompass all known forms of graphite, including, for example, highly oriented pyrolytic graphite (HOPG), vapor-deposited graphite, glass-like graphite, graphite foil (Grafoil, Sigraflex).
• HOPG highly oriented pyrolytic graphite
• vapor-deposited graphite glass-like graphite
• graphite foil Grafoil, Sigraflex
• a layer structure is said to be intercalable if foreign atoms or molecules can be brought mainly between the layers of the starting material by chemical or electrochemical reaction.
• HOPG highly oriented pyrolytic graphite
• vapor-deposited graphite vapor-deposited graphite
• glass-like graphite glass-like graphite
• graphite foil Garfoil, Sigraflex
• a layer structure is said to be intercalable if foreign atoms or molecules can be brought mainly between the layers of the starting material by chemical or electrochemical
• donor and acceptor compounds They are basically two types of graphite intercalation compounds: donor and acceptor compounds.
• a donor compound exists when the intercalated substance donates electrons to the graphite;
• Examples of donor compounds are alkali, alkaline earth and rare earth graphite intercalation bonds.
• Examples of acceptor compounds are transition metal halide, halogen and acid graphite intercalation compounds.
• the present invention is based on the fact that the optical reflection of the layer structure can be electrically controlled by the electrochemical incorporation of foreign atoms.
• the layer structure can be partially intercalated in a preparatory work step.
• the optical change in the surface of the layer structure that can be used for display purposes consists in the color differences that an intercalation compound exhibits at different concentrations of embedded foreign atoms, as well as in the color differences between the embedded and non-embedded state.
• electro-optical displays of the type described can also be used as multi-colored displays.
• the foreign atoms can be injected into the layer structure from a wide variety of ion conductors, which are in different states of matter.
• liquid and solid electrolytes are suitable which either contain the ions required for intercalation or enable them to be fed from a reservoir to the layer structure.
• electrolyte is intended to include the gel or paste-like nature of the same, for example various carbowaxes (polyethylene glycol 200- about 1500).
• an electrical voltage or an electrical current is applied between the working electrode and the counter electrode.
• the condition of the working electrode can be checked by means of a reference electrode.
• electrical leads to the electrodes are provided.
• customary techniques of segmenting the electrode or the counter electrode are used.
• Such segmentation techniques are known from electrochromic cells or from liquid crystal cells.
• Translucent electrodes are known and consist, for example, of glass plates coated with SnO “or InO”.
• Figure 1 is a schematic representation of a display cell according to the invention with transparent electrolyte.
• Figure 2 shows a cell for rear viewing with non-transparent electrolyte.
• Figure 3 shows a cell in which viewing from both sides is possible.
• the section shown in FIG. 1 from an electro-optical display is delimited on the observer side by a sight glass 1 which is coated with a transparent electrode 2, for example made of indium oxide.
• the electrode 2 is segmented to display a pattern. The individual segments are provided with corresponding electrical leads (not shown).
• a layer of a transparent electrolyte 3 borders on the electrode.
• the electrolyte consists of an organic solvent with one or more dissolved salts.
• Suitable solvents are, for example, dimethoxyethane (DME), propylene carbonate (PC), tetrahydrofuran (THF), diethylene glycol dimethyl ether (DIGLYME), dirnethylformamide (DMF), hexamethylphosphoric triamide (HMTP), dirnethylsulfoxide (DMSO) and others.
• DME dimethoxyethane
• PC propylene carbonate
• THF diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• DIGLYME diethylene glycol dimethyl ether
• HMTP hexamethylphosphoric triamide
• DMSO dirnethylsulfoxide
• Suitable salts are especially salts of metals from the alkal
• the electrolyte layer is delimited by a graphite electrode 4, which is connected as a cathode.
• the graphite electrode is located as a layer on a cover glass 5, which closes the arrangement on the other side.
• a cover glass 5 which closes the arrangement on the other side.
• the sealing and spacing between the edges of the two plates is carried out in the usual way, as is known from other cell technologies.
• the graphite layer is partially intercalated in a preparatory step. This is done by applying a voltage of, for example, 3.3 volts for 3 hours. An increase in the applied voltage to 3.8 volts provides a red to yellow color of the graphite layer 4 after about 20 minutes. The display device is thus ready for operation.
• the color can change depending on the polarity applied voltage can be reversibly changed between yellow, orange, red and black.
• peak currents typically 10 mA / cm 2 flow, for example.
• the voltage is only needed to switch the coloring on and off, i.e. during the color display, no power is required for a period of a few minutes to more than 10 minutes.
• the color display can last for a long time
• Times (days) can be maintained by voltage pulses at certain intervals.
• the cell drawn in section in FIG. 2 is, as mentioned, observable from the side facing away from the electrolyte.
• the sight glass 1 is coated with a thin graphite layer 6 in this version.
• the graphite layer has also been pre-intercalated in the manufacturing process in this embodiment.
• a layer of a non-transparent electrolyte 7 is connected to the graphite layer.
• Solid supraion conductors are particularly suitable for this, for example
• Li..N or Li-ß-aluminate Li.
• the electrolyte is delimited by a metal layer 8, which serves as an ion reservoir.
• Either graphite layer 6 / or metal layer 8 can be segmented accordingly for display purposes.
• the contacts between the graphite and the ion conductor or the ion conductor and the metal are preferably produced in a high vacuum of 10 -6 torr or in a high-purity argon atmosphere.
• a high-vacuum argon chamber made of stainless steel was used for this.
• FIG. 3 shows an alternative solution with solid electrolyte. This cell is observable from both sides. It consists of two transparent carrier plates 1, which are provided on the inside with transparent electrode layers 2. On one of the plates is over the
• Solid electrolyte 7 only partially covers the graphite layer, so that viewing from both sides is possible.
• the invention is suitable for all types of displays, but in particular for large-area displays.
• the invention is of particular importance for multicolored electro-optical displays. But even with small displays such as those for watches,
• the properties of the device according to the invention can advantageously be used by computers, instruments etc. or also for video displays.
• the invention is also particularly suitable for the production of multicolored displays.

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• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)

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• 1979
  • 1979-10-16 US US06/195,143 patent/US4343537A/en not_active Expired - Lifetime
  • 1979-10-16 WO PCT/CH1979/000135 patent/WO1980000880A1/de unknown
  • 1979-10-16 JP JP50165579A patent/JPS55500789A/ja active Pending
• 1980
  • 1980-05-07 EP EP79901281A patent/EP0020468A1/de not_active Withdrawn

Non-Patent Citations (1)

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