DE102008041377A1 - Dispersion, useful for preparing film, which is useful e.g. in optoelectronics, and microelectronics, comprises indium tin oxide particles, alkyloxacarboxylic acid, a thermoplastic binder e.g. polyvinyl butyral, and solvent e.g. alcohols - Google Patents

Abstract

Dispersion comprises: (a) 5-60 wt.% of indium tin oxide particles having an average particle diameter of less than 200 nm; (b) 0.1-5 wt.% of alkyloxacarboxylic acid as dispersing agent; (c) 1-20 wt.% of a thermoplastic binder; and (d) 30-90 wt.% solvent, where the sum of the components (a)-(d) is at least 98 wt.%. Independent claims are included for: (1) method for producing a flexible, transparent and electrically conductive film with a thickness of 1-50 mu m applied on a base, comprises applying the dispersion on the base by a film casting process under the formation of a film, drying the film and detaching from the base; and (2) the flexible, transparent and electrically conductive film with a thickness of 1-50 mu m applied on a base, obtained by the method.

Description

The The invention relates to a dispersion containing indium tin oxide Process for producing a transparent, conductive Film by means of this dispersion and the film itself.

transparent electrically conductive oxides (TCOs) are becoming increasingly important in the manufacture of electronic components as transparent electrodes. The materials become classic using cost-intensive PVD processes such as sputtering or vapor deposition, at comparatively high temperatures deposited as thin layers.

transparent electrically conductive oxides, so-called TCOs, have a great potential for use as transparent electrodes for a wide variety of technical applications and already increasing in production of high-tech products, such as solar cells, flat screens (TFTs) and liquid crystal displays (LCDs) used.

The Processing of TCOs into layers and structures takes place, for example, via classic PVD processes, such as sputtering and vapor deposition.

layers can also be produced by means of film casting become. This is a dispersion on a moving carrier applied, the liquid phase removed, the film optionally from Carrier detached and thermally treated.

In DE-A-19840527 discloses an indium tin oxide powder which is to be further processed by the method of film casting. No information is given in what form and under what conditions this should be done.

In DE-A-10119911 discloses a dispersion containing indium tin oxide particles and a catalytic agent capable of degrading the dispersant. This dispersion can be used in film casting processes. No information is given in what form and under what conditions this should be done.

In WO2006 / 125636 discloses a method in which a dispersion of inorganic nanoparticles by means of the film casting technique is applied to a substrate. When the dispersion is dried, flakes are obtained.

in the The prior art is not a process for producing transparent, Conductive films, which also self-supporting and are flexible, known.

task The present invention was therefore such a film and a To provide methods for their preparation. It was still a task To provide dispersion used in this process can.

definitions:

Under transparent in the sense of the invention is a maximum transmission of the films in the range of 500 nm to 580 nm of at least 60%, usually from 60 to 92%.

Under flexible in the context of the invention is the mechanical behavior of a film according to the invention, corresponding to a thermoplastic below the glass transition point.

Under an agglomerate are held together by cohesion To understand primary particles. The preserved spatial Structures as such are manageable, disintegrate upon exposure of shear energy in primary particles isolated from each other. In addition, it is possible that the agglomerates according to the invention also a small proportion Contain firmly bonded primary particles. The number of firmly bonded primary particles is usually 2 to 10. The agglomerates can, for example be obtained by spray drying.

Under completely or largely completely from each other isolated primary particles is according to the Invention to understand a powder. The mean primary particle diameter can be 2 to 50 nm. According to the invention can the powder by the action of shear forces from a Agglomerate can be obtained.

at The indium tin oxide is essentially a mixed oxide of indium and tin. Indium and tin can be found in one or in different oxidation states. For example In (+ I) and / or In (+ III) as well as Sn (+ II) and / or Sn (+ IV) are present. Sn is preferably present as Sn (+ IV). If necessary, you can Indium and tin also partially present as In (0) or Sn (0).

at the indium tin oxide is a tin-doped indium oxide, d. H. the proportion of tin oxide is less than the proportion of indium oxide. The proportion of tin, based on the sum of indium, calculated as In, and tin, calculated as Sn, is for example 2 to 10 wt .-%. The indium-tin oxide of the present invention has as crystalline phase predominantly or completely cubic indium tin oxide.

The indium tin oxide according to the invention may contain impurities. The acceptable level depends on the purpose. By way of example, SO ₄ ^2- , Co, Cu, Fe, Ni, Pb, Zn, K or Na can be contained via the starting materials. By using pure educts SO ₄ ^2- , Ca, Co, Cu, Fe, Ni, Pb and Zn can be brought to less than 0.005 wt .-% and Na, K to less than 0.01 wt .-%. Compounds introduced via the process, for example NH ₄ ⁺ and Cl ^- can be virtually completely removed if necessary. In general, less than 1 wt .-%, preferably less than 0.1 wt .-%, impurities based on the surface-modified indium tin oxide present.

Under Surface modification is to be understood as organic Molecules and / or fragments of such molecules, usually not more than 24 in total, especially not more than 18 in total and more preferably no more than 12 carbon atoms have, via a covalent or ionic bond and / or polar (dipole-dipole interaction) or van der Waals forces bound to the particle surface. Fragments can for example, by a partial thermal degradation of the organic Molecules are created. In the present invention the surface modification by the proportion of carbon expressed.

Under Sheet resistance will be the ohmic resistance below understood that on a coating with a uniform Layer thickness is obtained when a square area of any Contacted size on two opposite edges and the current as a function of the (DC) voltage is measured. The sheet resistance is measured in ohms and marked with ohms / sq. The determination of sheet resistance can also after other procedures, such as. B. the four-point measurement respectively.

• a) 5 bis 60 Gew.-%, bevorzugt 15 bis 55 Gew.-%, besonders bevorzugt 30 bis 45 Gew.-%, Indiumzinnoxid-Partikel mit einem mittleren Partikeldurchmesser von weniger als 200 nm,
• b) 0,1 bis 5 Gew.-%, bevorzugt 0,2–1,5 Gew.-%, Alkyloxacarbonsäure als Dispergiermittel,
• c) 1 bis 20 Gew.-%, bevorzugt 3 bis 10 Gew.-%, eines thermoplastischen Bindemittels,
• d) 30 bis 90 Gew.-%, bevorzugt 40 bis 80 Gew.-%, Lösungsmittel,

enthält, wobei die Summe der Bestandteile a) bis d) wenigstens 98 Gew.-% beträgt und wobei sich alle Prozentangaben auf die Dispersion beziehen.The invention relates to a dispersion which contains indium tin oxide particles and in each case one or more dispersants, organic binders and solvents, wherein the dispersion

• a) from 5 to 60% by weight, preferably from 15 to 55% by weight, particularly preferably from 30 to 45% by weight, of indium-tin oxide particles having a mean particle diameter of less than 200 nm,
• b) from 0.1 to 5% by weight, preferably from 0.2 to 1.5% by weight, of alkyloxacarboxylic acid as dispersant,
• c) 1 to 20% by weight, preferably 3 to 10% by weight, of a thermoplastic binder,
• d) from 30 to 90% by weight, preferably from 40 to 80% by weight, of solvent,

contains, wherein the sum of the components a) to d) is at least 98 wt .-% and wherein all percentages refer to the dispersion.

The Dispersion according to the invention is characterized an ideal viscosity for film casting 1 to 20 Pa · s, preferably from 4 to 10 Pa · s, at each 20 ° C off.

• a) einen Anteil an Indium von 90 bis 98, besonders bevorzugt 93 bis 96 Gew.-%, Zinn von 2 bis 10, besonders bevorzugt 4 bis 7 Gew.-%, Kohlenstoff von 0,01 bis 0,1 Gew.-% aufweisen, wobei die Summe dieser Anteile mindestens 99 Gew.-% bezogen auf die Summe von Indium, Zinn und Kohlenstoff ist,
• b) auf der xy-Farbskala Werte von x = 0,300 bis 0,320 und y-Werte von y = 0,330 bis 0,360,
• c) eine BET-Oberfläche von 30 bis 100 m²/g, bevorzugt 30 bis 60 m²/g, und
• d) einen Pulverwiderstand von 0,5 bis 5 Ohm·cm aufweisen.

The surface-modified indium tin oxide particles may preferably be agglomerates which

• a) a proportion of indium of 90 to 98, more preferably 93 to 96 wt .-%, tin of 2 to 10, particularly preferably 4 to 7 wt .-%, carbon of 0.01 to 0.1 wt .-% the sum of these fractions being at least 99% by weight, based on the sum of indium, tin and carbon,
• b) on the xy-color scale values of x = 0.300 to 0.320 and y-values of y = 0.330 to 0.360,
• c) a BET surface area of 30 to 100 m ² / g, preferably 30 to 60 m ² / g, and
• d) have a powder resistance of 0.5 to 5 ohm cm.

Of the Proportion of Indiumzinnoxidpartikel in the dispersion preferably 30 to 45 wt .-%.

The mean particle diameter D _{50 of} the surface-modified indium-tin oxide particles in the dispersion is preferably 50 to 150 nm and more preferably 60 to 120 nm. The mean particle diameter D ₅₀ can be determined, for example, by means of dynamic light scattering.

Of the mean primary particle diameter of the surface modified Indium tin oxide particles is preferably 10 to 50 nm and particularly preferably 20 to 40 nm and is determined by means of high-resolution Transmission Electron Microscopy (HRTEM) and gas absorption / desorption BET.

Preparation of the invention in the Dispersion of surface-modified indium tin oxide particles present:

• • Behandlung bei Temperaturen von 240°C bis 260°C unter reduzierenden Bedingungen,
• • Abkühlen auf Raumtemperatur und lagern an der Luft, nachfolgend
• • Behandlung bei Temperaturen von 270°C bis 310°C unter reduzierenden Bedingungen.

The surface-modified indium-tin oxide particles are obtainable by a process in which a surface-modified agglomerate of indium tin oxohydrate is dried in air at temperatures of more than 150 ° C. and less than 310 ° C., and subsequently under reducing conditions, for example in the presence of forming gas, calcined. The calcination is carried out in two stages, the second calcination step being carried out at a higher temperature than the first one. The two-stage calcination includes the steps

• Treatment at temperatures of 240 ° C to 260 ° C under reducing conditions,
• • Cool to room temperature and store in air, below
• • Treatment at temperatures from 270 ° C to 310 ° C under reducing conditions.

The individual treatment steps can have one Period of 0.5 to 8 hours.

• • Indium, gerechnet als In, von 93 bis 96 Gew.-%,
• • Zinn, gerechnet als Sn, von 4 bis 7 Gew.-%,
• • Kohlenstoff von 0,01 bis 0,1 Gew.-% auf,
• • wobei die Summe dieser Anteile mindestens 99 Gew.-% bezogen auf die Summe von Indium, Zinn und Kohlenstoff ist, vor.

The starting material for the preparation of the surface-modified indium tin oxide particles used in the dispersion according to the invention is indium tin oxohydrate. Preferably, the indium-tin-oxohydrate is present as a surface-modified agglomerate in a proportion

• Indium, calculated as In, from 93 to 96% by weight,
• Tin, calculated as Sn, from 4 to 7% by weight,
• Carbon from 0.01 to 0.1% by weight,
• • wherein the sum of these proportions is at least 99% by weight, based on the sum of indium, tin and carbon.

The agglomerates have a mean aggregate diameter of 5 to 50 microns, preferably 10 to 20 microns, and can be divided by simple dispersion predominantly or completely into primary particles. The BET surface area of the agglomerates of indium tin oxohydrate is preferably 50 to 200 m ² / g and more preferably 80 to 140 m ² / g.

• a) eine wässerige Lösung, welche Indium- und Zinn-Verbindungen und ein oder mehrere oberflächenmodifizierende Komponenten enthält, auf einen pH-Wert von 3,5 bis 4,5 einstellt, von gelösten Reaktionsprodukten und nicht umgesetzten Einsatzstoffen des Reaktionsgemisches abtrennt, und
• b) die erhaltene Dispersion einer Sprühtrocknung unterzieht.

The surface-modified agglomerate can, as in the European patent application of 06 May 2008 with the application number 08103837.4 can be obtained by

• a) an aqueous solution containing indium and tin compounds and one or more surface-modifying components, adjusted to a pH of 3.5 to 4.5, separated from dissolved reaction products and unreacted starting materials of the reaction mixture, and
• b) subjecting the resulting dispersion to spray-drying.

• • gesättigte oder ungesättigte Mono- und Polycarbonsäuren (vorzugsweise Monocarbonsäuren) mit 1 bis 24 Kohlenstoffatomen, wie zum Beispiel Ameisensäure, Essigsäure, Propionsäure, Buttersäure, Pentansäure, Hexansäure, Acrylsäure, Methacrylsäure, Crotonsäure, Citronensäure, Adipinsäure, Bernsteinsäure, Glutarsäure, Oxalsäure, Maleinsäure, Fumarsäure, Itaconsäure, Stearinsäure und insbesondere 3,6,9-Trioxadecansäure sowie die entsprechenden Anhydride;
• • Mono- und Polyamine, insbesondere solche der allgemeinen Formel R_3-nNH_n, worin n = 0, 1 oder 2 ist und die Reste R unabhängig voneinander Alkylgruppen mit 1 bis 12, insbesondere 1 bis 6 und besonders bevorzugt 1 bis 4 Kohlenstoffatomen darstellen, beispielsweise Methyl, Ethyl, n- und i-Propyl und Butyl; Polyethylenamine;
• • Säureamide, insbesondere Caprolactam;
• • Aminosäuren, insbesondere β-Alanin, Glycin, Valin, Aminocapronsäure, Leucin und Isoleucin;
• • Dicarbonylverbindungen mit 4 bis 12, insbesondere 5 bis 8 Kohlenstoffatomen, wie zum Beispiel Acetylaceton, 2,4-Hexandion, 3,5-Heptandion, Acetessigsäure, Acetessigsäure-C₁-C₄-Alkylester wie Acetessigsäureethylester, Diacetyl und Acetonylaceton;
• • Tenside, z. B. kationische, anionische, nicht-ionische und amphotere Tenside. Bevorzugt werden nicht-ionische Tenside, wobei Polyethylenoxid-Derivate besonders bevorzugt sind. Es kann sich dabei um Derivate mit gesättigten oder ungesättigten (Mono)carbonsäuren handeln, insbesondere mit Carbonsäuren mit mehr als 7, bevorzugt mehr als 11 Kohlenstoffatomen, beispielsweise Polyethylenoxid-Derivate mit Stearin-, Palmitin- oder Ölsäure. Es kann sich auch um Derivate mit Sorbitanestern handeln, wobei als Carbonsäure beispielsweise die vorstehend genannten in Frage kommen. Weiter können Polyethylenoxid(mono)alkylether, beispielsweise mit Alkoholen mit mehr als 7, bevorzugt mehr als 11 Kohlenstoffatomen.

Suitable surface modifying components are

• Saturated or unsaturated mono- and polycarboxylic acids (preferably monocarboxylic acids) having 1 to 24 carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, acrylic acid, methacrylic acid, crotonic acid, citric acid, adipic acid, succinic acid, glutaric acid, oxalic acid, maleic acid , Fumaric acid, itaconic acid, stearic acid and in particular 3,6,9-trioxadecanoic acid and the corresponding anhydrides;
• • Mono- and polyamines, especially those of the general formula R _3-n NH _n , wherein n = 0, 1 or 2 and the radicals R are independently alkyl groups having 1 to 12, especially 1 to 6 and particularly preferably 1 to 4 carbon atoms represent, for example, methyl, ethyl, n- and i-propyl and butyl; Polyethylene amines;
• Acid amides, in particular caprolactam;
• Amino acids, especially β-alanine, glycine, valine, aminocaproic acid, leucine and isoleucine;
• Dicarbonyl compounds having from 4 to 12, in particular from 5 to 8, carbon atoms, for example acetylacetone, 2,4-hexanedione, 3,5-heptanedione, acetoacetic acid, C ₁ -C ₄ -acylacetic acid esters, such as ethyl acetoacetate, diacetyl and acetonylacetone;
• • surfactants, e.g. Cationic, anionic, nonionic and amphoteric surfactants. Nonionic surfactants are preferred, with polyethylene oxide derivatives being particularly preferred. It may be derivatives with saturated or unsaturated (mono) carboxylic acids, in particular with carboxylic acids having more than 7, preferably more than 11 carbon atoms, for example polyethylene oxide derivatives with stearic, palmitic or oleic acid. It may also be derivatives with sorbitan esters, wherein as the carboxylic acid, for example, the above-mentioned come into question. Further, polyethylene oxide (mono) alkyl ethers, for example, with alcohols having more than 7, preferably more than 11 carbon atoms.

The surface modifying components can used singly or as a mixture. Especially preferred Compounds are 3,6,9-trioxadecanoic acid, β-alanine and caprolactam.

Of the Proportion of the surface-modifying component used is based on the sum of the indium and tin compound, preferably 2 to 30 wt .-%, more preferably 2 to 6 wt .-%.

Of the pH in the range of 3.5 to 4.5 can be achieved, for example, by primary, secondary, tertiary aliphatic or aromatic Amines, tetramethylammonium hydroxide, NaOH, KOH, ammonia, ammonium hydroxide or mixtures thereof. Particular preference is given to using ammonium hydroxide. It has proved to be advantageous, the reaction mixture 1 to 24 hours in this pH range. Subsequently It is advantageous to adjust a pH of 9 to 9.5. This can be done by the same connections, which also at the Adjustment to the pH range of 3.5 to 4.5 have been used.

advantageously, The salts generated in the reaction from the reaction mixture separated. This has, especially for the separation of ammonium salts, a cross-flow filtration proven that can be performed so that the conductivity the dispersion is preferably less than 5000 μS / cm, preferably less than 2000 μS / cm.

following For example, the reaction mixture may be concentrated by evaporation.

The solids content of the dispersion which is to be spray-dried is preferably 10 to 50 wt .-%, based on the dispersion.

The Spray drying is preferred at temperatures of 100 up to 150 ° C performed.

Next the production of indium tin oxohydrate as starting material for in the dispersion of the invention present surface-modified indium tin oxide particles Dispersants are also an essential part of the invention Dispersion itself. This contains as a dispersant Alkoxycarboxylic. Alkyloxacarboxylic acids are compounds, in addition to one or more carboxyl groups in addition Oxygen atoms within the remaining alkyl chain of the carboxylic acid wear. Oxacarboxylic acids are usually in the form of mono- or dicarboxylic acids. According to the invention the use of Oxamonocarbonsäuren preferred. Within of the chain radical of the carboxylic acid may be in the case of oxa acids an oxygen atom or two and more oxygen atoms provided be. The latter are called oligooxacarboxylic acids, their use according to the invention also preferred is. Further preferred embodiments are those in which the oxacarboxylic acid 6 to 12, in particular 8 to 10 chain atoms having. The carbon atoms of the carboxyl group are counted. Again, oligooxacarboxylic acids with the corresponding Chain lengths are preferred, d. H. Oxa acids with several oxygen atoms within the chain. In particular, according to the invention trioxacarboxylic acids be used. Of these trioxacarboxylic acids is 3,6,9-trioxadecanoic acid to be particularly preferred.

One further constituent of the dispersion according to the invention is a thermoplastic binder, which preferably from the Group consisting of polyvinyl acetals, polyvinyl alcohols, acetalized Polyvinyl alcohols, polymethyl methacrylates, polyvinyl chlorides, Polyacrylates, cellulose derivatives, latex binders, polyvinylpyrrolidones, Polyurethanes, polyethylenes, polypropylenes, polyiosbutylenes, Polybutenes, polyamides, polyimides, polytetrafluoroethylene, polycarbonates, Polyethers and polyepoxides is selected.

Especially polyvinyl acetals are preferred and polyvinyl butyrals from this group used. The best results are with polyvinyl butyrals having a molecular weight of 30,000 to 120,000 g / mol, in particular preferably used at 40,000 to 70,000 g / mol. Furthermore, the polyvinyl butyral have a hydroxyl content of about 10 to 30 wt .-%.

The Dispersion according to the invention may further comprise a or more plasticizers included. These are preferably from the group consisting of triethylene glycol di-2-ethylhexanoate, Dimethyl phthalate, n-butyl phthalate, butyl benzyl phthalate, dibutyl phthalate, Dioctyl phthalate, dioctyl adipate, 2-ethylhexyl diphenyl phosphate, tricresyl phosphate and triphenyl phosphate selected. The proportion of plasticizer in the dispersion according to the invention is preferred 0.5 to 10 wt .-% and particularly preferably 1.5 to 5 wt .-%.

The Dispersion according to the invention further comprises one or more solvents. These can be organic Solvent, water or mixtures thereof. In the As a rule, the solvent used is organic. Prefers may include alcohols, monoalkyl ethers of polyols, esters, ethers and ketones, furans and amides.

suitable Alcohols may be: methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, 2,6-dimethylheptanol-4, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, Methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, Diacetone alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol, Diethylene glycol, dipropylene glycol, hexanediol, octanediol, triethylene glycol, Tripropylene glycol and glycerin.

Suitable monoalkyl ethers of polyols may be:
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethyl butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylenglykolmonopropylether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, Propylenglykolonomethylether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether and Dipropylenlycolmonopropylether.

Suitable esters may be: diethyl carbonate, ethylene carbonate, propylene carbonate, methyl acetate, ethyl acetate, gamma-butyrolactone, gamma-valerolactone, n-propyl acetate, iso-propyl acetate, n-butyl acetate, iso-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate , 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, n-nonyl acetate, methyl acetoacetate, ethyl acetate toacetat, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Propylenglykolmonopropyletheracetat, Propylenglykolmonobutyletheracetat, dipropylene glycol monomethyl ether, Dipropylenglykolmonoethyletheracetat, glycol diacetate, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, iso-amyl propionate, diethyl oxalate, di-n-butyl oxalate, Methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, diethyl malonate, dimethyl phthalate and diethyl phthalate.

suitable Ethers may be: dipropyl ether, diisopropyl ether, dioxane, Tetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, Ethylene glycol dipropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, Propylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and diethylene glycol dipropyl ether.

suitable Ketones may be: acetone, methyl ethyl ketone, methyl n-propyl ketone, Methyl n-butyl ketone, diethyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, Ethyl n-butyl ketone, methyl n-hexyl ketone, di-1-butyl ketone, trimethylnonanone, Cyclohexanone, 2-hexanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, Acetophenone, acetylacetone, 2,4-hexanedione, 2,4-heptanedione, 3,5-heptanedione, 2,4-octanedione, 3,5-octanedione, 2,4-nonanedione, 3,5-nonanedione, 5-methyl-2,4-hexanedione and 2,2,6,6-tetramethyl-3,5-heptanedione.

Especially preferred solvents are selected from the group consisting of ethanol, isopropoxyethanol, propylene glycol phenyl ether, propane diols such as 1,2-propanediol and 1,3-propanediol, diacetone alcohol and butanediols such as 1,4-butanediol.

Of the Solvent content may preferably be 40 to 80% by weight, based on the dispersion amount.

The dispersion according to the invention may additionally contain further particles, preferably electrically conductive or semiconductive particles. Examples of these are ZnO, SnO or Cd ₂ SnO ₄ .

to Preparation of the dispersion of the invention can for example, mills, kneaders, roller mills, high-energy mills, where two or more predispersion streams at pressures from 1000 to 4000 bar collide against each other, are used. In particular, ball mills may be like planetary ball mills or stirred ball mills, mortar mills, Taumelmischer and three-roll chairs are used.

One Another object of the invention is the production of a flexible, transparent and electrically conductive foil with a Thickness of 1 to 50 μm, in particular 5 to 25 μm, applied as such or on a base, in which one the Dispersion according to the invention by means of a film casting process on a pad to form a film, the film dries and in case the film is preserved as such should be, this dissolves after drying of the substrate.

Suitable substrates are, for example, metals, ceramics, glasses, semiconductors or plastics. The plastics may comprising PLEXIGLAS ^® (PMMA; Evonik Degussa), for example, from the group to be selected, PET, polycarbonate or PVC.

It is possible, the film as such or on a substrate applied, at temperatures of 100 to 800 ° C, preferably 150 to 500 ° C, more preferably 200 to 250 ° C to be treated in the air. By the thermal aftertreatment the conductivity of the film can be increased. The aftertreatment is preferred over a a period of 5 minutes to 20 hours, more preferably 10 minutes to 5 hours. At high temperatures increases the conductivity of the film while the flexibility decreases. By variation of temperature and residence time can each have a desired conductivity and flexibility.

Prefers For the purposes of the invention is a method in which no thermal After treatment takes place.

One Another object of the invention is a flexible, transparent and electrically conductive foil having a thickness of 1 to 50 μm applied as such or on a substrate, obtainable according to the invention Method.

The The composition of the film will vary with the process parameters. Thus, a film which is not thermally post-treated substantially the same ratios of indium tin oxide, alkoxycarboxylic acid, thermoplastic binder and optionally plasticizer as the dispersion, while the solvent is predominant or has been completely removed.

If a thermal aftertreatment is carried out, partial decomposition of the organic constituents may occur, which depends on the temperature and the post-treatment time, so that the ratios of indium tin oxide, alkoxycarboxylic acid, thermoplastic binders and optionally plasticizers may vary in the film NEN.

One Another object of the invention is the use of the flexible, transparent and electrically conductive film in lamination process for Production of multi-layer systems, in optoelectronics, microelectronics, Chip packages, large scale integrated circuits, capacitors, Piezo actuators and sensors.

Examples

analytics:

To determine the electrical conductivity and the transmission, the films are cut into approximately 10 × 20 mm ² and 30 × 60 mm ² large samples.

The Transmission of the films in the visible wave spectrum is by means of of a UV / VIS / IR spectrometer (Lambda 19, Perkin Elmer, USA).

Example 1:

Preparation of surface-modified indium tin oxide

151.1 kg of indium (III) chloride, 12.6 kg of tin (IV) chloride · 5 H ₂ O and 6.25 kg of caprolactam are added to 460.4 kg of water and stirred. After a clear solution is formed, it is heated to 50 ° C. Subsequently, 122.8 kg of ammonium hydroxide solution (25% strength) are added dropwise with stirring. The suspension is stirred for a further 24 hours. Subsequently, 208.52 kg of ammonium hydroxide solution are added. Ammonium chloride is separated by cross-flow filtration: permeate flow 260-300 kg / m ² h. The conductivity of the suspension is 1018 μS / cm. Subsequently, the liquid phase is separated by spray drying. For this purpose, 20 l / h of the obtained after the separation of ammonium chloride suspension with a solids content of 9.6 wt .-% with the aid of 8 Nm ³ / h of air in a dryer (operating temperature 300 ° C, conical temperature 110 ° C, exhaust air temperature 115 ° C). There are obtained agglomerates of indium tin oxohydrate with a content of In of 94.96 wt .-%, Sn of 4.99 wt .-% and C of 0.042 wt .-%. The BET surface area (after DIN 66131 ) is 121 m ² / g, the tamped density (based on DIN EN ISO 787/11 ) 684 g / l, the loss on drying (2 h at 105 ° C.) 4.4% by weight, the loss on ignition (2 hours at 1000 ° C.) 18.0% by weight, the D ₅₀ ⁵⁾ value ( Cilas) 12.8 μm.

The Agglomerates are initially at 300 ° C over dried in air for 1 h and subsequently in an oven at a temperature of 250 ° C over held for 1 h in a Formiergasatmosphäre. After cooling to room temperature, the solid becomes at room temperature over a period of 8 h in air stored and subsequently at a temperature of 275 ° C over held for 1 h in a Formiergasatmosphäre.

The resulting surface-modified indium-tin oxide particles have a content of In of 94.98% by weight, of Sn of 4.99% by weight and of C of 0.025% by weight. The crystal phase is cubic. The BET surface area (after DIN 66131 ) is 48 m ² / g, the powder resistance is 1 ohm · cm, the tamped density (based on DIN EN ISO 787/11 ) 1035 g / l, and the xy color value 0.309 / 0.339.

Example 2:

Preparation of an inventive dispersion

To 50 g of ethanol and 0.82 g of 3,6,9-trioxadecanoic 27.4 g of indium tin oxide particles described in Example 1 are introduced. The dispersion is carried out for 24 h in a tumble mixer (Turbula, Willy A. Bachofen) using 1-2 mm grinding balls of stabilized ZrO ₂ . Subsequently, 7.8 g of polyvinyl butyral having a molecular weight of 40,000 to 70,000 g / mol, and 3.9 g of benzyl phthalate (ferro) are added and the dispersion is homogenized for a further 24-48 h. Before casting, the thus prepared dispersion is sieved and degassed at a reduced pressure (200 mbar) for about one hour.

The indium tin oxide particles have a D ₅₀ value of 80 to 100 nm determined by means of dynamic light scattering.

The Dispersion has a content of indium tin oxide of 31 wt .-% and shows pseudoplastic behavior, with no hysteresis, like them is marked by undesired thixotropic effects becomes.

One Increase in the shear rate leads to a decrease in the viscosity, which gives a homogeneous discharge of the dispersion during the Casting process when passing under the cutting guaranteed.

The Dispersion is fluid, causing the potting facilitates thin layers. With declining shear rate it comes to a re-stiffening of the dispersion, which is a bleeding the generated structure and a separation of the dispersion components counteracts after passing the doctor blade.

In 1 the rheological behavior of the dispersion of Example 2 according to the invention is shown. The viscosity in Pas is plotted against the shear rate in s ^-1 . With declining shear rate the dispersion stiffenes again, which counteracts bleeding of the generated structure as well as segregation of the constituents of the dispersion after passing through the doctor blade.

Example 3A:

Preparation of an inventive foil

The dispersion is drawn in a continuous caster with a cast shoe on a drawn silicone-coated PET film to a 21 cm wide and 1 m long film. The casting parameters selected were a speed of 50 cm / min and a cutting height of 100 μm, which corresponds to a shear rate below the doctor blade of about 83 s ^-1 . In this case, the viscosity of the dispersion according to the invention reaches a value of 0.71 Pa · s. After drying at room temperature overnight, a homogeneous, crack-free film with a thickness of 10 .mu.m was obtained, which was then readily removable from the support.

Example 3B:

Preparation of an inventive foil

Analogous Example 3A, at a speed of 50 cm / mi and cutting height of 125 μm. The result is a film with a thickness of 15 μm.

Surprisingly the films of Examples 3A and 3B have a transparent character and electrically conductive properties. Surprisingly, therefore, because in this state, a high binder / plasticizer content in the Product exists, what the mentioned properties actually unfavorable influence.

The Self-supporting films have sufficient Strength and flexibility for further processing by cutting and lamination methods.

The Films with thicknesses of 10 microns and 15 microns have maximum transmittances of about 64% and 70% in the range of 500 nm to 580 nm.

The sheet resistivity of the films is in the range of 10 ⁶ ohms / square.

By a subsequent treatment in air at a temperature of 200 ° C over a period of 60 to 120 minutes, the sheet resistance can be set to values of less than 1000 ohms / square be lowered, with a brownish color the film occurs and reduces its flexibility.

2 shows the sheet resistance of the film at a temperature of 200 ° C depending on the holding time.

In a second series of experiments, film pieces were tempered for 20 min at temperatures of 100 ° C to 500 ° C in air and then measured their specific surface resistances. As in 3 As shown, the sheet resistance of the film decreases continuously with increasing temperature so that ultimately values in the range of 500 ohms / square are achieved after annealing at 500 ° C. Both experimental series show that improved layer conductivities and transmissions can be achieved by appropriate temperature treatment in air. Through a combination of temperature and holding time, the flexibility of the films, their electrical conductivity and transmission can be varied.

Example 4A:

To the Building a multilayer system is called a conductive layer the ITO film of Example 3A with a cut-to-size area of 40 mm × 40 mm and as a dielectric substrate material ceramic film "Ceramtape GC" (CeramTec AG, Marktredwitz) by thermocompression and subsequent Sintered together. To a warping of the composite to avoid during the sintering process, both on the top as well as the bottom a Constraining tape "Ceramtape A "(CeramTec AG, Marktredwitz) with an appropriate surface area. The layers thus stacked are placed in a press die a flow of structure during lamination prevented to a temperature in the range of glass transition temperature of the binder / plasticizer system of about 70 ° C heated and with a pressure of 25 MPa for a period of 10 min laminated. This creates a homogeneous, mechanically stable connection of the layers created among each other. Subsequently, will the composite is sintered in a furnace, with the constraining layers residue after sintering by simply stripping off be removed. The result is a mechanically stable composite layer.

Example 4B:

As a conductive layer, the ITO film of Example 3A with a cut-to-size area dimension of 50 mm × 50 mm is placed on a glass plate cleaned with alcohol and acetone. In order to avoid scratching the glass by the metal plates of the laminating press, one layer of PET is placed under the glass plate and on the ITO foil. As lamination parameters, a pressure of about 15 MPa, a temperature of 80 ° C and a duration of about 5 min are set. Under these conditions, a connection of the film takes place on the Glass plate.

Example 4C:

When conductive layer is the ITO film of Example 3A with a cut-to-size measure of 50 mm × 50 placed on a glass plate treated as in Example 4B, both on a hot plate to a temperature of about 90 ° 0 heated. The thus preheated layers are subsequently evacuated in a chamber at about 100 mbar. You get a pore-free connection of the film on the glass plate.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19840527 A [0006]
• - DE 10119911 A [0007]
• WO 2006/125636 [0008]
• - EP 081038337 [0030]

Cited non-patent literature

• - DIN 66131 [0063]
• - DIN EN ISO 787/11 [0063]
• - DIN 66131 [0065]
• - DIN EN ISO 787/11 [0065]

Claims (15)

Dispersion containing indium tin oxide particles and in each case one or more dispersants, organic binders and solvents, characterized in that they contain a) 5 to 60% by weight indium tin oxide particles having a mean particle diameter of less than 200 nm, b) 0, 1 to 5% by weight of alkyloxacarboxylic acid as dispersant, c) 1 to 20% by weight of a thermoplastic binder, d) 30 to 90% by weight of solvent, the sum of constituents a) to d) being at least 98% by weight .-% and wherein all percentages refer to the dispersion. Dispersion according to claim 1, characterized in that the mean particle diameter D _{50 of} the surface-modified indium-tin oxide particles in the dispersion is 50 to 150 nm. Dispersion according to claims 1 or 2, characterized in that the mean primary particle diameter the surface-modified indium-tin oxide particles 10 to 50 nm, preferably 20 to 40 nm, determined by means of high-resolution Transmission Electron Microscopy (HRTEM). Dispersion according to claims 1 to 3, characterized in that one surface-modified Agglomerates of indium tin oxide particles used. Dispersion according to claims 1 to 4, characterized in that as the alkoxycarboxylic acid 3,6,9-trioxadecanoic acid. Dispersion according to claims 1 to 5, characterized in that as a thermoplastic binder a polyvinyl butyral is used. Dispersion according to claims 1 to 6, characterized in that it additionally comprises a plasticizer contains. Dispersion according to claim 7, characterized in that the proportion of plasticizer in the dispersion is from 0.5 to 10% by weight is. Dispersion according to claims 1 to 8, characterized in that it comprises at least one solvent selected from the group consisting of alcohols, monoalkyl ethers of polyols, esters, ethers and ketones or water. Dispersion according to claims 1 to 9, characterized in that they are further electrically conductive or Contains semiconducting particles. Process for making a flexible, transparent and electrically conductive foil having a thickness of 1 up to 50 μm applied as such or on a substrate, in which the dispersion according to the claims 1 to 10 by means of a film casting on a pad to form a film, the film dries and for the case that the film should be obtained as such, this after dissolves the drying of the pad. Method according to claim 11, characterized in that that the film at temperatures of 100 to 800 ° C at post-treated in the air. Method according to claim 12, characterized in that that you have the after-treatment over a period of 5 minutes to 20 hours, preferably 10 minutes to 5 hours. Flexible, transparent and electrically conductive Film with a thickness of 1 to 50 microns as such or on a pad applied, obtainable by the method according to claims 11 to 13. Use of flexible, transparent and electric conductive film according to claim 14 in Lamination process for the production of multi-layer systems, in Optoelectronics, microelectronics, chip packages, highly integrated Circuits, capacitors, piezoactuators and sensors.