Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-05-19
2003-07-15
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S081000, C522S083000, C522S075000, C522S091000, C522S099000, C522S182000
Reexamination Certificate
active
06593390
ABSTRACT:
This invention relates to ink jet ink compositions and in particular to such compositions which are curable by ultra-violet radiation.
Radiation curable inks e.g. for screen printing and offset printing have been known for some time and more recently, there have been proposals for radiation-curable ink jet inks; see, for example, GB-A-2233928, JP-A-63102936, U.S. Pat. No. 4,303,924, EP-A-0540203, EP-A-0465039 and WO97/31071. There are, however, substantial problems in arriving at a radiation-curable formulation which meets all the criteria required of an ink jet ink; specifically, low viscosity, the required level of surface tension, low volatility, long term stability, rapid drying of the ink dot derived from the droplet ejected from the nozzle of the print head, and the provision of print of satisfactory quality, especially resistance to scratching and adhesion to the substrate.
We have now developed a radiation curable ink jet ink which is essentially free of non-reactive diluent and yet has the desired viscosity, surface tension, volatility, stability and drying rate and produces print of acceptable quality. Inks according to the invention thus can be printed without difficulty from ink jet printers to give good quality print on a variety of substrates including such disparate materials as paper and non-adsorbent materials e.g. metal. They are of particular interest, however, in printing on plastics which are difficult to print on, e.g. polyolefins such as polyethylene and polypropylene.
According to one aspect of the present invention, there is provided a radiation curable ink jet ink having a viscosity not greater than 35 mPa.s at 30° C. as measured using a Brookfield Viscometer fitted with a small sample adaptor having a No. 18 spindle and at a rotational speed of 60 rpm, giving a shear rate of 79.2 sec
−1
, and comprising a colorant component, a diluent consisting essentially of reactive liquid material and, optionally, at least one photopolymerisation catalyst and wherein the reactive liquid material is formed of both monofunctional and polyfunctional material and comprises from 5 to 30% by weight of at least one oligomer.
By consisting essentially of reactive liquid material, we mean that the diluent is free or substantially free of non-reactive components; that is to say, if any non-reactive liquid component is present in the diluent it forms no more than 1% by weight of the ink, preferably not more than 0.5%, by weight.
By reactive material we mean material containing one or more unsaturated carbon-carbon bonds polymerisable by radiation. In accordance with the invention, the reactive material comprises a mixture of monomer and oligomer. Oligomer is sometimes known as prepolymer. Non-limiting examples of monomers are acrylates, methacrylates and alkoxylated and polyalkoxylated derivatives thereof. Non-limiting examples of oligomers (prepolymers) are polyester-, urethane- and epoxy-acrylates.
Preferably, said at least one oligomer has an equivalent weight of at least 180. Print obtained from inks containing oligomer exhibits improved toughness, adhesion and/or scratch resistance as compared with print derived from the same ink composition but excluding oligomer.
Preferably, the oligomer is liquid so as to maintain the desired low viscosity of the ink and preferably it has a functionality greater than 1. If it is not liquid, it should be soluble in the liquid components of the reactive material. In any event, the oligomer is deemed to form part of the reactive liquid material.
In another preferred embodiment, the ink composition includes a silicone derivative containing carbon-carbon unsaturation which is polymerisable by radiation, to adjust the surface tension of the ink. This polymerisable silicone derivative, if present, is also deemed to form part of the reactive liquid material.
While the possibility of formulating the compositions of the invention to be cured using other radiation sources, e.g. electron beam, is not excluded, the compositions are preferably formulated to be curable by visible, or more preferably ultra violet, light, in which case they will usually include at least one photoinitiator.
The components of the compositions of the invention will now be described in greater detail.
The colorant is preferably thermally stable and water-insoluble. While the possibility of using colorants such as dyes, which are soluble in the diluent is not excluded, it is preferred to use those, such as pigments, which are insoluble, especially where light-fastness is important. In this case, it may be desirable to include a dispersant in the composition to stabilise the dispersion of insoluble colorant in the diluent.
Examples of insoluble colorants include, in particular, carbon black and those colorants characterised as pigment dyes in The Colour Index.
Examples of suitable pigments include those within the ranges having the following CI classifications:
Colour
CI Number
Green
PG 7 and 36
Orange
PO 5, 34, 36, 38, 43, 51, 60, 62,
64, 66, 67 and 73
Red
PR 112, 149, 170, 178, 179, 185,
187, 188, 207, 208, 214, 220,
224, 242, 251, 254, 255, 260 and
264
Magenta/Violet
PV 19, 23, 31, and 37 and PR 122,
181 and 202
Yellow
PY 17, 120, 138, 155, 168, 175,
179, 180, 181 and 185
Blue
PB 15
Black
PB 2, 5 and 7.
Examples of specific pigments include IRGALITE BLUE GLVO, MONASTRAL BLUE FGX, IRGALITE BLUE GLSM, HELIOGEN BLUE L7101F, LUTETIA CYANINE ENJ, HELIOGEN BLUE L6700F, MONASTRAL GNXC, MONASTRAL GBX, MONASTRAL GLX, MONASTRAL 6Y, IRGAZIN DPP ORANGE RA, NOVAPERM ORANGE H5G70, NOVPERM ORANGE HL, MONOLITE ORANGE 2R, NOVAPERM RED HFG, HOSTAPERM ORANGE HGL, PALIOGEN ORANGE L2640, SICOFAST ORANGE 2953, IRGAZIN ORANGE 3GL, CHROMOPTHAL ORANGE GP, HOSTAPERM ORANGE GR, PV CARMINE HF4C, NOVAPERM RED F3RK 70, MONOLITE RED BR, IRGAZIN DPP RUBINE TR, IRGAZIN DPP SCARLET EK, RT-390-D SCARLET, RT-280-D RED, NOVAPERM RED HF4B, NOVAPERM RED HF3S, NOVAPERM RD HF2B, VYNAMON RED 3BFW, CHROMOPTHAL RED G, VYNAMON SCARLET 3Y, PALIOGEN RED L3585, NOVAPERM RED BL, PALIOGEN RED 3880 HD, HOSTAPERM P2GL, HOSTAPERM RED P3GL, HOSTAPERM RED E5B 02, SICOFAST RED L3550, SUNFAST MAGENTA 122, SUNFAST RED 122, SUNFAST VIOLET 19 228-0594, SUNFAST VIOLET 19 228-1220, CINQUASIA VIOLET RT-791-D, VIOLET R NRT-201-D, RED B NRT-796-D, VIOLET R RT-101-D, MONOLITE VIOLET 31, SUNFAST MAGENTA 22, MAGENTA RT-243-D, MAGENTA RT 355-D, RED B RT-195-D, CINQUASIA CARBERNET RT-385-D, MONOLITE VIOLET R, MICROSOL VIOLET R, CHROMOPTHAL VIOLET B, ORACET PINK RF, IRGALITE YELLOW 2GP, IRGALITE YELLOW WGP, PV FAST YELLOW HG, PV FAST YELLOW H3R, HOSTAPERM YELLOW H6G, PV FAST YELLOW, PALIOTOL YELLOW D1155 and IRGAZIN YELLOW 3R.
Mixtures of colorants may be employed, if desired, including mixtures of dyes, mixtures of pigments and mixtures of one or more dyes with one or more pigments.
In one preferred embodiment of the invention, the colorants are chosen to give the widest range of colours and tones in a hexachrome system.
The amount of colorant employed in the ink will depend on the choice of colorant and the depth of colour required in the print, and can be established by simple experiment. In general, for pigments it will fall within the range 0.01% to 50% by weight, the amount chosen being such that viscosity of the ink does not exceed 35 mPa.s. For organic pigments the amount will generally be in the range 0.01 to 10% weight, more preferably 0.05 to 6%, most preferably 0.05 to 3%.
Where the colorant comprises a pigment which is to be dispersed in the diluent, it preferably has a particle size of not greater than 1 &mgr;m maximum dimension and more preferably not greater than 0.5 &mgr;m. Even more preferably, the particles have a narrow size range distribution.
Where the ink comprises a dispersion of pigment, a dispersant will normally be required to aid or stabilise the dispersion. The choice of dispersant will depend upon the nature of the pigment and composition of the diluent. Examples of suitable materials may be found amongst dispersants sold under the trade names of Solsperse, EFKA and Byk. Mixtures of dispersants and mix
Johnson Steve
Woods Jill
Berman Susan W.
Marshall Gerstein & Borun
XAAR Technology Limited
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