Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-12-19
2004-10-19
Goodrow, John L (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S124300, C427S002140, C427S458000, C118S620000
Reexamination Certificate
active
06806017
ABSTRACT:
The present invention relates to a method and apparatus for the electrostatic application of powder material onto the surfaces of solid dosage forms, and more particularly, but not exclusively, pharmaceutical solid dosage forms.
A “solid dosage form” can be formed from any solid material that can be apportioned into individual units; it may be, but is not necessarily, an oral dosage form. Examples of pharmaceutical solid dosage forms include pharmaceutical tablets, pharmaceutical pessaries, pharmaceutical bougies and pharmaceutical suppositories. The term “pharmaceutical tablet” should be interpreted as covering all pharmaceutical products which are to be taken orally, including pressed tablets, pellets, capsules and spherules. Examples of non-pharmaceutical solid dosage forms include items of confectionery and washing detergent tablets.
The electrostatic application of powder material to solid dosage forms is known. In the known techniques, the powder is generally applied directly onto the solid dosage forms, either by spraying electrostatically charged powder material onto the solid dosage forms, or by holding the powder material at a potential difference to the solid dosage forms sufficient to cause the powder material to be attracted to the solid dosage forms. For example, WO92/14451 describes a process in which the cores of pharmaceutical tablets are conveyed on an earthed conveyor belt and electrostatically charged powder material is sprayed onto the tablet cores to form a powder coating on the exposed surface of the tablet cores. WO96/35516 describes a process in which the cores of pharmaceutical tablets are held substantially isolated from their surroundings adjacent to a source of powder at a potential difference to the tablet cores sufficient to cause the exposed surface of the tablet cores to become coated with the powder.
The present invention provides a method of electrostatically applying a powder material to a solid dosage form, the method comprising the steps of electrostatically applying a powder material to a first intermediate means, and transferring the powder material that has been applied to the first intermediate means from the first intermediate means to the solid dosage form.
Applying the powder material to a first intermediate means before it is applied to the solid dosage form has certain advantages. It becomes possible to provide an arrangement in which the location of the deposition of the powder material can be closely controlled and, for example, enables powder material to be deposited on a solid dosage form in a precise pattern. It may also facilitate the deposition of powder material on a three dimensional surface.
Any suitable method may be used to apply the powder material electrostatically to the first intermediate means. For example, the first intermediate means may be earthed and the powder material held at a potential sufficient to cause the powder material to adhere to the first intermediate means.
In a preferred embodiment of the invention the powder material is applied to the first intermediate means by applying an electrostatic charge to the first intermediate means, and holding the powder material at a potential sufficiently different from the potential of the first intermediate means to cause the powder material to adhere to the first intermediate means.
A first especially advantageous feature of a preferred embodiment of the invention is that the electrostatic charge may be applied to the first intermediate means in a pattern, making it possible to apply powder material onto a solid dosage form in the form of a pattern. Any desired pattern may be produced simply by applying a suitable electrostatic charge pattern to the first intermediate means. Thus, it is, for example, possible to print onto a solid dosage form the name or the dosage of the solid dosage form, or to apply to the solid dosage form a logo or some other design. By using different coloured powder materials, it is also possible to produce a pattern but at the same time have an uninterrupted coating on the solid dosage form. For example, different coloured powder materials could be used to produce a solid dosage form having a striped coating over all of the surface of a region of the solid dosage form or over the whole of the solid dosage form.
Where a coating is applied to parts only of a region being coated, the coating is referred to herein as discontinuous, even though in the case of, for example, joined up writing each part of the coating may be continuous with the other parts.
The electrostatic charge does not have to be applied to the first intermediate means in a pattern. It may be applied to the first intermediate means over the whole of a surface portion thereof. Accordingly, a conventional unpatterned and uninterrupted coating may be formed, if desired. Such a coating is referred to herein as a continuous coating but it will be understood that it may or may not, for example, cover all of a surface of a solid dosage form.
In the case where an electrostatic charge is applied to the first intermediate means, that means may be any means which is capable of maintaining an electrostatic charge on its surface. For example, the first intermediate means may be in the form of a drum or a belt and may comprise a photo-conductive semi-conductor at its surface. A photo-conductive semi-conductor is a material which conducts electricity on exposure to light, but behaves as an insulator in the absence of light. An electrostatic charge pattern may be applied to such a first intermediate means by electrostatically charging the semi-conductor in the dark, and then projecting an image onto the semi-conductor. The electrostatic charge will be dissipated in the illuminated areas, but will be retained in the unilluminated areas. Thus, an electrostatic charge pattern in the shape of the image will be formed on the semi-conductor. Such first intermediate means are used in conventional photocopiers as photo-conductive drums or belts. For example, a photoconductive drum used in the present invention may be a conductive drum coated with selenium, selenium/arsenic or selenium/tellurium, or a conductive drum coated with a thin layer of photoconductive pigment in a binder resin, and a charge transport layer coated over the photoconductive pigment layer. A photoconductive belt used for the invention may be a flexible conductive substrate coated with photogenerator layer comprising a photoconductive pigment in a binder polymer overcoated with a charge transport layer.
The powder material should possess a defined electrostatic charge which is either (a) of the same sign of charge as the residual charged area pattern on the photoconductive drum or belt after light exposure, or (b) of opposite sign of charge to the residual charged pattern on the photoconductive drum or belt after light exposure. In the case (a) the powder will be developed onto the areas of the photoconductive drum, or belt, which have been discharged, i.e. the light illuminated areas, and will be repelled by the areas of the photoconductive drum, or belt, which remain charged. Conversely in case (b) the powder will be developed onto the areas of the photoconductive drum, or belt, which remain charged, and will not be developed onto areas of the photoconductive drum, or belt, which have been discharged, i.e. the light illuminated areas. The powder material may have a permanent or temporary net charge. Any suitable method may be used to charge the powder material. Advantageously, the electrostatic charge on the powder material is imparted by a triboelectric charging process (as is common in conventional photocopying) or by corona charging.
Any suitable method may be used to apply the charged powder onto the first intermediate means. Methods have already been developed in the fields of electrophotography and electrography and examples of suitable methods are described, for example, in Electrophotography and Development Physics, Revised Second Edition, by L. B. Schein, published by Laplacian Press, Morgan Hill Calif.
A second es
Feather David Hoover
Nelson Douglas Howard
Reeves Linda Ann
Whiteman Marshall
Burns Doane Swecker & Mathis L.L.P.
Goodrow John L
Phoqus Limited
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