Chemistry: analytical and immunological testing – Optical result
Reexamination Certificate
2000-12-27
2003-09-23
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
C436S171000, C422S068100, C422S082050, C422S082090, C073S866000, C073S053010, C073S054010
Reexamination Certificate
active
06623978
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of measuring a rheological property of a composite filled with particles obtained by mixing and dispersing a particulate material in a liquid material such as resin and equipment therefor. In more particularly, it relates to a method for measuring a rheological property of a composite filled with particles and evaluation equipment employing, and this method comprises a method wherein a rheological property of a composite filled with particles obtained by mixing a raw-material particulate material with a liquid material is measured in situ in a condition maintaining the original material structure without destroying the material by applying external force such as shearing force thereto, by measuring as an anisotropy signal the coagulation structure of the particulate material within the composite filled with particles, and using the amount of this anisotropy as an index of a rheological property, of the properties of the composite filled with particles.
2. Description of the Related Art
Composite materials filled with particles obtained by mixing and dispersing particulate materials in liquid materials such as resins are employed as insulating materials, electrode/conductive materials, electroviscous fluids, chemical/mechanical grinding slurries, and raw materials for ceramic molding processes such as injection molding and/or cast molding, and also, in recent years, have come to be widely used in sealing materials intended for protecting and insulating semiconductor elements. In particular, with progress in VLSI, in order to achieve increased element fineness, low viscosity/high forming ability of composite materials filled with particles in order to achieve the ability to produce any required shape and/or to enable pouring between minute electrodes is indispensable.
However, scientific study of the field of such composite materials filled with particles is still in its infancy and studies relating to the viscosity and moldability of composite materials filled with particles are based merely on experience. For example, in common methods of evaluation of the rheological properties such as viscosity of a composite filled with particles, this is evaluated indirectly by deduction from primary information such as the particle size distribution of the particulate material constituting the raw material for packing/dispersion. Such methods of evaluation are based on the fact that the viscosity of the particle dispersion material becomes smaller as the particle size of the particulate material that is mixed therein becomes large and the relative surface area becomes small, or that the viscosity becomes lower as the width of the particle size distribution becomes greater. However, in current practically used material systems, products are seldom prepared wherein these factors are individually controlled and owing to the complex mutual interaction of various factors, it is difficult to define conditions such that rheological properties are dominant. It has therefore been pointed out that there are limits to the extent to which it is possible to achieve the accuracy required in an evaluation technique of rheological properties of for example semiconductor sealing materials simply using such conventional discoveries (for example, Shinsuke Hagiwara “The present state of development of semiconductor sealing materials”, Plastics, Vol. 49, p. 58, 1998 and Takeshi Kitano “Rheological properties of filler packing polymer melts”, Filler, Vol. 3, p. 96, 1998).
As a way of solving this, attempts have been made to construct theoretical hypotheses of the packing structure and dispersion condition of the particulate material in the composite filled with particles, and to correlate these with rheological properties. For example, in the field of wet molding of ceramics there are studies of slurry viscosity hypothesizing the particle structures formed in the molding process (for example, Laid-open Japanese Patent Publication Number 11-304686 (1999) and Ichiro Tsubaki et al. “New method of evaluation of slurries for optimal design of wet molding processes”, Journal of the Ceramics Association of Japan (Nippon Seramikusu Gakkai Ronbunshi), Vol. 106, p. 504, 1998). Also, in the field of electroviscous fluids, there are attempts to correlate the relationships between density and current values of mixed particulate materials (for example Laid-open Japanese Patent Publication Number 11-343496 (1999)). Although there are instances where methods such as the above succeed in the case of material systems where the concentration of the particulate material is not particularly large, so that the particle size distribution etc. is simple (if possible monodispersed), they cannot adequately cope with dispersed systems of high particulate material concentration having practically employed particle size distribution and/or surface characteristics (for example, Hiroki Usui “Rheological model for coagulated slurry of monodispersed fine silica particles”, Collected Chemical Engineering Papers (Kagaku Kogaku Ronbunshu), Vol, 25, p. 459, 1999)
We have up to the present been unsuccessful in finding any studies in which the secondary structure of particulate materials as described above is actually directly observed in the condition in which the composite filled with particles is employed i.e. in a condition in which the original material structure is maintained. We believe that one reason for this is that no method has been established for observing the internal structure of a dispersion system and correlating this structure with its properties when the liquid material is a dispersion medium. For example, there is the problem that no methodology has been prepared for the application to liquid material systems of methods of measurement using X-ray diffraction equipment, optical microscopes, or scanning electron microscopes (SEM) etc., which are the universal methods in the case of dispersion systems where the dispersion medium of the particulate material is solid (for example ceramic material systems etc.).
Also, in most existing methods of measuring rheological properties, measurement was effected by inserting a stirrer or cantilever of an interatomic force microscope into the composite filled with particles, thereby destroying its structure, and using the shearing force etc. when this was done as an index. Methods existed in which structural analysis was conducted in a non-contacting condition with the composite filled with particles still in the condition in which it is actually used, by employing an electron beam or X-ray diffraction, in the case of the particulate material on its own, or by employing polarization or interference of light waves, in the case of the liquid material on its own. However, no method employing these has been found in the case of a composite filled with particles, which is a material in which these are mixed together. The case when the liquid material is a resin-based material can be regarded as one type of polymer material. In polymeric material systems, typically use is made of polarized light observation for evaluation of the photoelasticity characteristic with applied stress, measurement of the birefringence of a plastic lens, or evaluation of molecular alignment characteristics in liquid crystal materials. However, no attempts have been made to employ this for evaluation of the characteristics of particles, rather than resin, in resin composite materials filled with particles·dispersion materials. The reason for this is believed to be that the particulate materials that are generally employed in this material field are amorphous SiO
2
particles and it was not intuitively anticipated that these methods of observation could be applied to materials having an isotropic crystalline structure (or not having a crystalline structure).
In order to overcome the defects possessed by such conventional measurement techniques for composite materials filled with particles, the present invention was developed taki
Naito Makio
Sando Mutsuo
Takao Yasumasa
Alexander Lyle A.
Japan as represented by Secretary of Agency of Industrial Scienc
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