Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/087—Binders for toner particles
  • G03G9/08742—Binders for toner particles comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/08755—Polyesters
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/087—Binders for toner particles
  • G03G9/08775—Natural macromolecular compounds or derivatives thereof
  • G03G9/08782—Waxes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/097—Plasticisers; Charge controlling agents
  • G03G9/09708—Inorganic compounds

Definitions

• This invention relates to dry non-magnetic toner particles comprising a white pigment, especially to dry non-magnetic toner particles comprising rutile type TiO 2 . It further relates to a method for printing images on a transparent wherein the images contain a white background.
• White toner particles and their use is known in the art, especially for printing on a black background or for printing techniques wherein black and white toners are used for printing different grey levels.
• an electrophotographic copying method comprising the use of a copying apparatus having a positive-image copying system, wherein toner images with a coloured toner are formed and transferred to a coloured insulating paper of a colour different to that of said toner while selecting the colours of the paper and the toner so as to form reverse images.
• a white toner with 100 parts by weight of a styrene-acrylic resin and 20 parts by weight of rutile type TiO 2 is disclosed.
• a white toner comprising a fixing resin and dispersed therein, a titanium dioxide pigment of high purity containing at least 99 % by weight of TiO 2 , not more than 0.1 % by weight of Al 2 O 3 and not more than 0.05 % by weight of SiO 2 as a white pigment, said titanium dioxide having an average particle diameter of not less than 0.05 ⁇ m.
• maximum 50 parts by weight, preferably maximum 30 parts by weight, of the TiO 2 can be used for 100 parts by weight of toner resin because toner with higher amounts of TiO 2 can not be fixed.
• JP-A-01 048067 a white toner is disclosed wherein between 5 and 20 % by weight of TiO 2 is present, preferably there is between 8 and 10 % by weight of TiO 2 .
• a white toner comprising binder resin and titanium dioxide with 0.20-0.35 ⁇ m in mean particle size at the content of 15-60 parts by weight on the basis of 100 parts by weight of the binder resin.
• a process for toning an image comprises developing an electrostatic latent image with a grey toner, wherein a mixture of a white toner and a black toner is used as the grey toner.
• the white toner comprises preferably TiO 2 in the rutile crystal structure and for at most 50 parts by weight for 100 parts by weight of toner resin.
• the object of the invention is realised by providing non-magnetic toner particles comprising 100 parts by weight of toner resin, wherein at least 50 parts by weight of said toner resin is a polyester resin and between 65 and 180 parts by weight of rutile type TiO 2 for 100 parts by weight of said toner resin .
• the further object of the invention is realised by providing an electrostatographic printing method for white toner images with an opacity, OP, of at least 60 % comprising the steps of :
• non-magnetic toner particles with from 65 to 180 parts by weight of rutile type TiO 2 for 100 parts by weight of toner resin, when said toner resin comprised at least 50 parts by weight of a polyester resin, although the prior art teachings indicate that not more than 60 parts by weight of rutile type TiO 2 for 100 parts by weight of toner resin could be incorporated in toner particles. No problems were with respect to stability of the toner charge, to the fixing properties were observed, even not when the rutile type TiO 2 was only between 95 and 98 % pure. Both in fixing system where the fixing proceeded by hot-roller fixing as in a system where the fixing proceeds by non-contact means, especially by infra-red radiation, the fixing quality of the toner image was good despite the high pigment to resin ratio.
• the toner resin could be any resin know in the art as long as for 100 parts (wt/wt) of toner resin at least 50 parts (wt/wt) of a polyester was present.
• the toner resin in non-magnetic toner particles according to this invention contains a least 50 parts (wt/wt) of a polyester with acid or hydroxyl value between 10 and 30 mg KOH/g. More preferably the toner resin in non-magnetic toner particles according to this invention is a polyester or a mixture of different polyesters.
• polyester with acid or hydroxyl value between 10 and 30 mg KOH/g it is preferred to use a polyester with acid or hydroxyl value between 10 and 30 mg KOH/g or when a mixture of different polyesters is used to include in that mixture at least 50 % (wt/wt) of a polyester with acid or hydroxyl value between 10 and 30 mg KOH/g.
• Very useful polyester resins for use in non-magnetic toner particles according to this invention are tabulated in table 1.
• Chemical structure AV HV Tg °C Mn Mw 1.
• Polyester resin of terephthalic acid, ethyleneglycol and DIANOL 22 3 31.1 62 3.6 10 Polyester resin of fumaric acid and DIANOL 33 17 5.2 55 4.4 12 3.
• TiO 2 in rutile crystal configuration was the most efficient.
• the titanium dioxide useful in this invention does not need to be for at least 99 % pure, although rutile type TiO 2 with a purity of 99 % and up can be used in this invention, it is also possible to use TiO 2 with a purity between 94 % and 98 %, this means that TiO 2 wherein Al 2 O 3 and/or SiO 2 are present in a relative high amount is also useful in non-magnetic toner particles according to this invention. This has the advantage that for producing non-magnetic toner particles of this invention also less pure and thus less expensive TiO 2 can be used.
• the non-magnetic toner particles according to this invention comprising TiO 2 in rutile crystal configuration can further comprise SiO 2 or Al 2 O 3 that is deliberately added to the TiO 2 .
• These compounds can be added to the mixture of toner resin and TiO 2 , during the melt kneading step in the production of the non-magnetic toner particles, or can first be mixed to fix the SiO 2 or Al 2 O 3 on the surface of the TiO 2 .
• Such treatments of the TiO 2 have been described in US-A-4 943 506.
• the surface of the TiO 2 for use in toner particles according to this invention can also, before adding it to the bulk of the toner particles, be treated by an organic compounds selected from the group of silicone oils, silane coupling agent, titanium coupling agents aluminium coupling agents and zirco-aluminium coupling agents.
• Typical useful silane coupling agents are, e.g., vinyl triacetoxy silane, methyl trimethoxy silane, vinyl tris(methoxyethoxysilane), methyl triethoxysilane, etc..
• Useful titane coupling agents are, e.g., isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate, etc..
• a typical useful aluminium coupling agent is, e.g., acetoalkoxy aluminium di-isopropylate.
• rutile type TiO 2 commercially available and useful in non-magnetic toner particles of this invention are, e.g., BAYERTITAN RKB2 and BAYERTITAN RDFI (trade names of Bayer AG, Leverkusen, Germany) or RHODITAN RL60 and RHODITAN RL67 (trade names of Rhone-Poulenc, France). From these commercial available rutile type TiO 2 it is preferred to use BAYERTITAN RDFI.
• Toner particles according to this invention can also comprise fluorescent brightening agents, that fluoresce under UV-light. By adding such fluorescent brightening agents, the whiteness of an image printed with white non-magnetic toner particles of this invention is enhanced.
• fluorescent brightening agents are, e.g., sold by Ciba-Geigy, Switserland under trade name UVITEX OKF, sold by Ciba-Geigy, Switserland under trade name UVITEX OB, or derivatives of stilbene.
• a image made with white toner of this invention with a fluorescent brightening agent does not show a bluish hue and can thus be used in relative high concentration, i.e. up to 10 parts (wt/wt) for 100 parts (wt/wt) of toner resin. Preferably an amount between 1 and 5 parts (wt/wt) for 100 parts (wt/wt) of toner resin is used.
• White toner particles comprising a fluorescent brightening agent are very useful in security printing. With such toners an image can be printed on white paper, white polymeric image receiving sheets without fluorescent brightening agent. Such an image is almost invisible under normal ambient lightening conditions, but becomes clearly visible under UV-light. It is also possible to print a first white image on a coloured background with toner particles of this invention that do not contain a fluorescent brightening agent and another image (near to said first image or on top of it) with non-magnetic toner particles of this invention that do contain a fluorescent brightening agent. In this case the first image is visible under normal ambient lightening conditions and the second becomes visible under UV-illumination. Thus it is possible to add in the print a kind of "ghost image” that is only visible under UV (ultraviolet) illumination. Such a feature adds to the security of, e.g., identity documents.
• Toner particles according to this invention can, even without the presence of a fluorescent brightening agent, be used for including security features in printed matter. It is possible to print on a transparent support (mostly a polymeric support) an even white background with toner particles according to this invention wherein a white image with different opacity (from slightly, i.e. less than 1 % different up to 25 % different) is present.
• the image of different density can be printed by applying a higher or lower amount of toner particles than the amount of toner particles used to print the background density. In this case the same toner particles can be used.
• the image of different density can be printed by applying toner particles containing a lower amount of TiO 2 than the amount of TiO 2 present in the toner particles used to print the background density.
• Toner particles according to this invention can further comprise waxes, especially useful waxes are monohydroxy compounds with formula CH 3 (CH 2 ) n OH wherein n is an integer between 21 and 360 or monocarboxy compounds with formula CH 3 (CH 2 ) n COOH wherein n is an integer between 21 and 360.
• Such compounds are available under trade name UNICID for the monocarboxy compounds and UNILIN for the monohydroxy compounds from PETROLITE, 6910 East 14th street, TULSA, Oklahoma 74112, USA.
• onium compounds having an alkylgroup of at least 12 C-atoms and at most 25 C-atoms can be added to the non-magnetic toner particles of this invention.
• Such an onium compound is beneficial as charge control agent and, as disclosed in US-A-5 622 803 and US-A-5 532 097 for giving the toner particles a narrow charge distribution.
• a typical member of the class of useful onium compounds for incorporation in toner particles of this invention is (CH 3 ) 3 N + C 16 H 33 Br - It was moreover found that, although the TiO 2 could be well dispersed in a toner resin as long as for 100 parts (wt/wt) of toner resin at least 50 parts (wt/wt) of a polyester was present, the dispersion of the TiO 2 was still better when either a monohydroxy compound with formula CH 3 (CH 2 ) n OH wherein n is an integer between 21 and 360, a monocarboxy compound with formula CH 3 (CH 2 ) n COOH wherein n is an integer between 21 and 360 or an onium compound having an alkylgroup of at least 12 C-atoms and at most 25 C-atoms was present.
• Toner particles according to this invention are preferably used in a non-magnetic mono-component developer or in a two component developer wherein the non-magnetic toner particles are used together with magnetic carrier particles.
• the use of the non-magnetic toner particles of this invention in a two-component developer is most preferred and the non-magnetic toner particles comprise at least one resistivity lowering substance compound having a volume resistivity lower than the volume resistivity of said resin, wherein said substance is capable of lowering the volume resistivity of said resin by a factor of at least 3.3 when present in said resin in a concentration of 5 % by weight relative to the weight of said resin.
• the non-magnetic toner particles have preferably an absolute median
• the white toner particles of this invention can be used with any kind of magnetic carrier particles known in the art, e.g. iron beads, composite carriers, etc, with an average particles diameter from 10 to 200 ⁇ m, it is preferred to use the white non-magnetic toner particles of this invention in a developer comprising magnetic carrier particles said carrier particles having :
• the present invention also encompasses a method for producing white toner images with an opacity, OP, of at least 60 % comprising the steps of :
• the present invention also encompasses a method for including security features to a toner image comprising the steps of
• the invention also comprises a method for including security features to a toner image comprising the steps of
• the invention further encompasses a method for including security features to a toner image comprising the steps of
• the invention further encompasses a method for including security features to a toner image comprising the steps of
• the solidified mass was pulverised and milled using an ALPINE Fliessbettallestrahlmühle type 100AFG (trade name) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (trade name).
• the average particle size of the separated toner was measured by COULTER COUNTER MODEL MULTISIZER (trade name) was found to be 8.0 ⁇ m by volume.
• the toner particles were mixed with 0.5 % of hydrophobic colloidal silica particles (BET-value 130 m 2 /g) to give a toner composition.
• T1 to T12 Twelve different types of toner particles (T1 to T12) were prepared, the amount, the nature and the manufacturer of TiO 2 added to the toner particles are tabulated in table 2.
• a Cu-Zn ferrite based coated carrier was prepared by coating a Cu-Zn ferrite core with 1 % of dimethylsilicone using a solution spraying technique in a fluidized bed and post curing the coating.
• the carrier showed a saturation magnetisation (M sat ) of 0.41 T.
• the amount of particles ⁇ 25 ⁇ m was 4.9 % wt/wt.
• a developer was prepared by adding 7,5 % of the toner compositions to the carrier particles.
• the standard hot roller fuser was removed, and the toner of the unfixed copy was non-contact fused by radiation using an infra-red black body radiant element placed at a distance of 10 mm from the transparent support carrying the toner image.
• the support passed by the radiant element at a speed of 5 cm per second.
• the average power provided to the radiant heating element was 375 W making the element operate at a temperature of 600 °C using reflectors to concentrate the radiant heat onto the support.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Developing Agents For Electrophotography (AREA)

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Cited By (8)

Citations (5)

• 1999
  • 1999-06-23 EP EP19990202009 patent/EP0977091B1/fr not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (2)

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