Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
1998-05-07
2001-01-16
Loney, Donald (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S141000, C428S206000, C428S211100, C428S213000, C427S288000, C427S428010, C118S244000, C118S256000, C118S262000
Reexamination Certificate
active
06174586
ABSTRACT:
TECHNICAL FIELD
The invention relates to security paper formed from base paper provided with a surface treatment layer on one side or both sides thereof. Any base paper whatsoever can be used. The term surface treatment includes both surface sizing and coating, implying that the layer can be formed with a sizing agent and/or with a coating slip. The paper may also comprise two superimposed coating layers, optionally applied on top of a surface sizing layer. By security paper is meant paper that can be readily distinguished from other paper, i.e. the paper is easily recognizable.
The invention also relates to a method of producing surface treated security paper.
The invention furthermore relates to a device for producing surface treated security paper.
BACKGROUND ART
Many uncoated papers present a so called watermark, for instance in the form of the manufacturer's name or in the form of some distinctive symbol. The watermark is normally incorporated by commensurate patterning of a wire in the paper machine, for instance the wire located on the dandy roll. The watermark in the paper can be clearly seen when the paper is directed towards a light source, for instance towards a window of a room. This type of paper is one form of security paper.
The need for surface treated paper, primarily coated paper, increases from year to year. When a base paper which incorporates a watermark is coated, the watermark will be covered and hidden by the coating layer, so that the paper can no longer be easily recognized.
Many ways of marking finished paper so that something resembling watermarks appears in the paper are known to the art.
According to the international (PCT) application WO 94/07694 a chemical is applied to the paper such as to render the paper transparent over those areas in which the chemical has been applied. The chemical is applied by transferring a solution of the chemical in question via a number of rolls to a stamp means mounted on a roll that is located in the immediate proximity of another roll, and by passing the paper through the nip defined between said two rolls and therewith transfer the chemical solution from the stamp means to the paper. This chemical paper watermarking process is carried out conveniently in a printing press, either immediately before or immediately after the actual printing process.
According to the German patent specification 37 18 452 a plurality of marks are embossed mechanically in the paper and it is stated that the paper becomes transparent at the embossed locations. This process is achieved with a roll that includes a plurality of patterned elevated surfaces. A corresponding number of anvil surfaces are provided on a shaft which is spaced slightly from said elevations, said anvil surfaces having a breadth which covers the elevations on the embossment roll. The paper is introduced into the gap between the elevations and the anvil surfaces and because the gap is slightly smaller than the thickness of the paper, the pattern defined by the elevated embossments is embodied in the paper.
DISCLOSURE OF THE INVENTION
Technical problem
There is a need to be able to distinguish easily also between different refined papers. By refined paper is meant paper that is surface treated, such as paper provided with surface sizing agent layer and/or coating slip layer.
The solution
The present invention provides a solution which satisfies this need and relates to a security paper formed from base paper provided with a surface treatment layer on at least one side of the paper, characterized in that the thickness of the layer locally deviates markedly from the layer thickness of the remaining, dominant surface of the paper and in that this local deviation forms a distinctive mark of the paper.
The base paper may be any base paper whatsoever. The major part of the paper is comprised of pulp fibres, including such which are produced in a mechanical, chemi-mechanical and chemical way. The pulp may be produced from any known lignocellulosic material, including softwood and hardwood. Different pulp fibres in mixture form a usual pulp furnish. The pulps may be unbleached, semi-bleached and fully bleached, the last mentioned pulp being the dominant pulp. The paper may be based completely or partially on secondary fibres. An admixture with synthetic fibres is also feasible. The base paper contains one or more known paper chemicals in addition to pulp fibres. Certain base papers include one or more fillers.
The surface treatment layer (one or more) may be based on any appropriate slip whatsoever, including all substances from surface sizing agent to coating slip. A slip of this kind will normally contain a large number of chemicals, of which binder and pigment are the dominating chemicals. It is of advantage when the slip includes fluorescent whitening agent. The reason for this will be made evident further on in the text.
According to one embodiment of the invention, the local layer thickness is greater than the thickness of the layer on the dominant surface of the paper. For instance, the local layer thickness may be 70-130% greater than the thickness of the layer on the remainder of the paper.
According to a second embodiment of the invention, the local layer thickness is smaller than the layer thickness of the dominant paper surface. For instance, the local layer thickness may be 30-70% smaller than the layer thickness of the remainder of the paper.
According to a third embodiment of the invention, the local layer thickness may be both greater and smaller than the layer thickness of the dominant paper surface in separate positions.
It is preferred that the local deviation, i.e. the distinctive mark, will have the form of a company name and/or a company's logotype and/or a trademark. Naturally, any other form of distinctive mark which allows the paper to be easily recognized may be used. This distinctive mark need not be one and the same mark along the paper web, but it is quite feasible to use two or more different and alternating distinctive marks instead.
Naturally, the security paper may present surface treatment layers on both sides thereof, in which case local deviations in the form of distinctive marks may be incorporated in one of the surface treatment layers or in both surface treatment layers.
Light and illumination of the paper play a role in the distinctiveness of the security paper. The distinctive mark incorporated in the paper is best seen when the paper is placed over or directed towards a light source, such as a light bulb or lamp for instance.
When the local layer thickness is greater than the layer thickness of the dominant paper surface, the distinctive mark will appear as a darker colour than the remainder of the paper. The difference between the distinctive mark and the paper in general will be particularly pronounced when the layer contains fluorescent whitening agent and the light source is a lamp, which emits ultraviolet light.
It is not necessary to use a lamp in order to highlight the distinctive mark, since it suffices to direct the paper towards a window in daylight. The distinctive mark can also be highlighted by placing the paper at a given angle to ceiling lighting, i.e. not directly in line with the light source. The phenomenon may be described as a mirror effect.
When the local layer thickness is smaller than the layer thickness of the dominant paper surface, the distinctive mark will be seen as lighter in colour than the remainder of the paper.
The invention also relates to a method of surface treating a travelling paper web, wherein the paper web is caused to pass a device which includes at least one roll for applying surface treatment slip in a uniform amount along the main surface of the web, characterized in that the surface treatment slip is applied to the paper web locally and at uniform intervals in an amount which is less than and/or greater than the amount of slip applied to the main surface of the paper web leading to that said paper web presents distinctive marks.
The surface treatment slip is applied to the paper
Holmen AB
Loney Donald
Sughrue Mion Zinn Macpeak & Seas, PLLC
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