Electrorheological fluid and electric device

Abstract

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

1 . An electric device comprised of an electrorheological fluid which is comprised of a dispersion medium in which particles for electrorheological fluid are contained and which is filled between a pair of electrodes, in which electric device,
 in a region of at least part of at least one surface of the surfaces of the pair of electrodes facing each other, an arithmetic mean roughness (Ra) is 0.5 μm or greater and less than 300 μm and a mean length (RSm) of roughness curve elements is 10 nm or greater and less than 100 μm.   
     
     
         2 . The electric device according to  claim 1 , wherein a gap between the pair of electrodes is 0.1 mm or greater and 0.5 mm or smaller. 
     
     
         3 . The electric device according to  claim 1 , wherein the electrorheological fluid comprises:
 a dispersion medium containing fluorine atoms in an amount of over 0 wt % and 50.0 wt % or smaller in which   particles for electrorheological fluid containing a sulfonic acid group-containing polymer having a content of sulfonic acid groups of 30 wt % or greater and 70 wt % or smaller are contained in an amount of 10 vol % or greater and 50 vol % or smaller with respect to the total volume of the dispersion medium and the particles.   
     
     
         4 . The electric device according to  claim 3 , wherein the dispersion medium contains fluorine atoms in an amount of 38.0 wt % or greater and 41.5 wt % or smaller. 
     
     
         5 . The electric device according to  claim 3 , wherein the sulfonic acid group-containing polymer has a sulfonated aromatic structure. 
     
     
         6 . The electric device according to  claim 3 , wherein the content of the chlorine atoms in the particles for electrorheological fluid is 5,000 ppm or smaller. 
     
     
         7 . The electric device according to  claim 3 , wherein the content of the chlorine atoms in the particles for electrorheological fluid is 1 ppm or greater. 
     
     
         8 . The electric device according to  claim 1 , wherein the electrorheological fluid comprises:
 a dispersion medium containing fluorine atoms in which   particles for electrorheological fluid containing a sulfonic acid group-containing polymer are contained, wherein   the electrorheological fluid exhibits an electrorheological effect X expressed by the following formula (1):
     X=S   1   /S   0    (1)
 
   (in which formula (1) X is 140 or greater, S 1  is the shear stress when applying a 3.0 kV/mm electric field, while S 0  is the shear stress when not applying an electric field).   
     
     
         9 . The electric device according to  claim 1 , wherein the electrorheological fluid comprises:
 a dispersion medium containing fluorine atoms in an amount of 38.0 wt % or greater and 41.0 wt % or smaller in which   particles for electrorheological fluid containing a sulfonic acid group-containing polymer having a content of sulfonic acid groups of 30 wt % or greater and 70 wt % or smaller are contained in an amount of 10 vol % or greater and 50 vol % or smaller with respect to the total volume of the dispersion medium and the particles, wherein   the dispersion medium is a mixed medium of
 a fluorine-based oil selected from a group consisting of a low polymer of ethylene trifluoride, a perfluoro polyether oil, and a fluorine-modified silicone oil; and 
 a silicone oil, 
   the sulfonic acid group-containing polymer has a sulfonated aromatic structure, and   the particles for electrorheological fluid are selected from a group consisting of
 particles consisting of the sulfonic acid group-containing polymer; and 
 particles comprised of cores of porous polymer particles or porous silica particles, and the sulfonic acid group-containing polymer coated on the surfaces of the cores, wherein 
   the electrorheological fluid exhibits an electrorheological effect X expressed by the following formula (1):
     X=S   1   /S   0    (1)
 
   (in which formula (1) X is 140 or greater, S 1  is the shear stress when applying a 3.0 kV/mm electric field, while S 0  is the shear stress when not applying an electric field).   
     
     
         10 . The electric device according to  claim 9 , wherein the fluorine-based oil is a low polymer of ethylene trifluoride. 
     
     
         11 . The electric device according to  claim 9 , wherein the silicone oil is selected from a group consisting of polydimethylsiloxane, partially octyl-substituted polydimethylsiloxane, and partially phenyl substituted polydimethylsiloxane. 
     
     
         12 . The electric device according to  claim 1 , constituting a brake, clutch, or haptic device. 
     
     
         13 . The electric device according to  claim 3 , constituting a brake, clutch, or haptic device. 
     
     
         14 . The electric device according to  claim 8 , constituting a brake, clutch, or haptic device. 
     
     
         15 . The electric device according to  claim 9 , constituting a brake, clutch, or haptic device.