JP2009536425A - Printing method on optical disk - Google Patents

Abstract

A method of printing on an optical disk that avoids softening and penetration of an ink jet composition into a coating layer by the use of a base coating material having specific physical and chemical properties.
A composition comprising a prepolymer, at least one monomer, a photoinitiator and a smoothing agent, wherein the composition does not contain any surface modifiers that interfere with printability, and the cured composition Is water insoluble, not absorbed by water, applied to one side of the optical disc, and then radiation cured. The resulting coating surface is receptive to printing with radiation curable inkjet inks.
[Selection figure] None

Description

  The present invention relates to a printing method on an optical disc.

  Optical discs include various types of compact discs (CDs) and digital versatile discs (DVDs), including formats such as Blu-ray discs and HD-DVDs. They are designed to carry data (including auditory or video information) that can be read by a laser or other optical element. Pre-recorded or duplicated discs usually show the informational nature of the disc on the other side of the surface read by a laser or other optical element, or any printed top layer for simple decorative purposes Have For example, in the case of compact discs, the decorated areas are both the disc material (typically polycarbonate) and the spin-coated layer used to protect the recording medium. This printing is desired to be durable, water and grease resistant and inexpensive.

  For printing operations that are longer than approximately 1000 discs, the replication industry typically uses screen printing and / or offset printing. These techniques can produce very strong images and relatively durable print quality at a relatively low cost per disc.

  However, the cost per disc of such a technique is very high for a short printing operation of roughly 500 copies or less. For the operation of roughly 50 discs, the cost per disc of good quality screen printing can easily approach 1 British pound (GBP) per disc.

  Therefore, recently, such a short printing operation is usually processed by ink jet printing. These operations are also typically duplicated (ie, not replicated) unless reordered.

  Conventional inkjet inks do not adhere well to the surface of optical discs (typically polycarbonate or UV cured spin coating in the case of CD), and many schemes consist of a base layer that bonds well to optical discs and inkjet inks. The Such a base layer can be applied, for example, by screen printing or spin coating techniques. Examples include Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4 and Patent Literature 5, all of which are absorbent as a base for continuous printing using a standard inkjet printer, Preferably the use of a hydrophilic subbing layer is disclosed. The resulting product is attractive and the cost per disc is relatively low.

  Although these prior art techniques have shown success in attempts to utilize such techniques, they use aqueous inkjet inks. When used in this way, these ink-jet inks do not address the fundamental problem of such inks that they are not durable enough. They will come off the optical disc in water or even under normal handling. Furthermore, they generally have poor wear resistance. These problems can be overcome by covering the print with a transparent film or by spraying or printing over a varnish or lacquer coating. However, any of these measures add an extra processing step and can always be expensive and inconvenient. They require additional material and thereby increase costs.

  All of the above schemes use standard inkjet inks. These are usually aqueous or solvent borne. Such “drying” of ink by a combination of evaporation and absorption into the substrate on which the ink is printed results in the various disadvantages described above. To the best of our knowledge, none of the conventional methods address this problem and use any other type of inkjet ink.

  Radiation curable (eg UV energy curable) inkjet inks are known. They are usually free of water or organic solvents and “dry” by curing as a result of polymerization induced by exposure to UV (ultraviolet) or other radiation (eg, electron beam). Unlike their aqueous equivalents, once cured, they can provide hardness, durable surfaces that are resistant to water, oil, body fluids and most domestically available fluids, and wear. it can. However, in experiments, the inventors have used high resolution print heads (eg, XAAR Omnijet 318) that do not print well on conventional optical discs that may or may not have a base coating of the type described above. UV inkjet ink suitable for use in For example, coatings can often be peeled off even by being scratched by a fingernail, and the printed image is generally poor in quality due to poor printed dot shape and is 'colored' Or the appearance fades. It should also be noted that jet-printed images have optimal visual effects when backed up with a solid color, especially white.

If the base coating is used in the wet state, i.e. before it is dried or cured, the inventors have found that good print quality can be obtained when jet printed. However, once the coating is dried or cured, the print quality is unsuccessful due to poor acceptability. This is inconvenient for the replication industry involved in short-time operation of optical discs and is not accustomed to requiring two separate printing processes (coating the base layer and then printing the ink jet on the top layer). . Apart from the cost of acquiring two separate coating machines (one for each process), they increase the labor costs of manually transferring disks from one machine to another, or even install this machine In order to have one of investing additional equipment. In any case, this is not only expensive, but also risks damaging the transferred disc. The industry prefers to use blank recordable optical disks that are already coated with a base coating so that only the information or decoration to be printed on the optical disk is involved.
European Patent No. 0,574,860 European Patent No. 0,628,956 European Patent No. 1,294,570 US Pat. No. 5,573,831 US Pat. No. 6,437,017

  Recently, the present inventors have found that these problems can be overcome by the use of basic coating materials having specific physical and chemical properties.

  Accordingly, the present invention comprises an optical disc having an optically readable surface and a printing surface, the printing surface being formed by radiation curing a composition comprising a prepolymer, at least one monomer, and a smoothing agent. The composition has a radiation curable receptive coating and does not contain any surface modifiers that interfere with printability, and the cured composition is water insoluble and not absorbed by water. Furthermore, the cured coating has a high degree of solvent resistance to promote wettability of the inkjet ink on the surface and avoid softening and penetration of the inkjet composition into the coating layer.

  Among the surface modifiers that interfere with printability are silicone surface modifiers, and thus the present invention, in one embodiment, provides an optical disc having an optically readable surface and a printing surface. The printed surface has a radiation curable receptive coating formed by radiation curing a composition comprising a prepolymer, at least one monomer, and a smoothing agent, the composition comprising an optional silicone surface modification Without the agent, the cured composition is water insoluble and not absorbed by water.

  In the present invention, unlike the prior art, the receptive coating does not absorb the ink applied to it. Instead, the ink is positioned over the coating and cured by radiation (eg UV or electron beam). When the composition is cured by UV energy, it contains a photoinitiator in addition to the above composition. If it is cured by electron beam (EB), a photoinitiator is not necessary.

  If the composition forming the receptive layer does not contain silicone or similar surface modifiers, the radiation curable inkjet ink will adhere well to the surface of the composition to be cured. In order to achieve good compatibility between the cured receptive coating and the cured ink, the cured receptive coating is also water insoluble and not absorbed by water.

  Accordingly, the present invention further provides a process wherein, as described above, radiation curable jet ink is jet printed on one side of an optical disc onto a curable receptive coating and then the ink is cured by exposure to curing radiation. .

If the constraints defined above are observed, the composition of the receptive coating can vary over a wide range. It contains at least the following components:
1. 1. Radiation curable prepolymer 2. radiation curable monomer; 3. a photoinitiator, if the composition is cured with UV energy, and Non-silicone-based surface modifiers

Further, the composition optionally and preferably includes any one or both of the following:
5. 5. Pigments and / or fillers and / or extenders, and Structurant

  The composition advantageously used to make the receptive coating comprises at least one prepolymer or combination of prepolymers. Suitable prepolymers (also called oligomers) include epoxy acrylates, acrylated oils, urethane acrylates, polyester acrylates, polyether acrylates, acrylated amines, acrylic saturated resins, acrylic acrylates, cycloaliphatic epoxides (cations), phenol epoxies Examples include novolak and acrylated epoxy soybean oil. Preferably the prepolymer has a number average molecular weight greater than 500, more preferably greater than 800. The receptive coating preferably comprises 10% or more, preferably 20% or more by weight of one or more such prepolymers, based on the total weight of the composition. Preferably, the receptive coating comprises no more than 50 wt% prepolymer, more preferably no more than 40 wt%, based on the total weight of the composition. For example, the prepolymer may be present in an amount of 1% to 60% by weight, preferably 20% to 40% by weight, based on the total molecular weight of the composition. In a preferred embodiment, the prepolymer has a number average molecular weight greater than 500 and is present at a level of 20% to 40% by weight based on the total weight of the composition. Preferred prepolymers exhibit a low level of shrinkage when cured. Further details and examples can be found in “Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints,” edited by G Webster, Volume II: Prepolymers & Reactive in this book. Incorporated by reference. Of these, epoxy acrylates are preferred, and bisphenol A epoxy acrylates and modified bisphenol A epoxy acrylates (eg, modified by incorporating amino, hydroxy, polyester, and ethoxy groups during manufacture) are more preferable. Particularly preferred are Ebecryl 3701, Ebecryl 3700, Ebecryl 3500, Ebecryl 3708 and Ebecryl 605 from UCB, Crayor CN104A80 from Cray Valley, and Crayne epoxies from Cray Valley. It is.

  The radiation curable monomer is preferably an ethylenically unsaturated compound, such as an acrylate, methacrylate or vinyl compound, or a compound polymerizable by a ring opening mechanism.

  Examples of suitable acrylate monomers include butanediol diacrylate; trimethylolpropane triacrylate; di-trimethylolpropane tetraacrylate; pentaerythritol triacrylate; di-pentaerythritol pentaacrylate; polyether acrylate (eg, ethoxylated) Trimethylolpropane triacrylate, glycerol propoxylate triacrylate, ethoxylated pentaerythritol tetraacrylate, epoxy acrylate (eg dianol diacrylate (= 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane di-) Acrylate, Ebecry 150 from UCB))); glycol diacrylate (e.g. , Tripropylene glycol diacrylate, polyethylene glycol diacrylate (eg tetraethylene glycol diacrylate), neopentyl glycol diacrylate and dipropylene glycol diacrylate); ethoxylated or propoxylated glycol and acrylate esters of polyols (eg , Propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate and alkyl acrylate (eg hexanediol diacrylate, isobornyl acrylate, 2- (2-ethoxyethoxy) ethyl acrylate, octadecyl acrylate, lauryl acrylate, stearyl acrylate) , Isodecyl acrylate, octi Acrylate, decyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, oxyethylated phenol acrylate, tetrahydrofuryl acrylate, 2- (2-ethoxyethoxy) ethyl acrylate and 4-t-butylcyclohexyl acrylate)).

  Methacrylate monomers include methacrylate equivalents of the above acrylates and in particular hexanediol dimethacrylate, trimethylolpropane triacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, and 1,4-butanediol dimethacrylate. It is done.

  Non-acrylated reactive diluents that can be incorporated include vinyl compounds such as N-vinyl pyrrolidone, N-vinyl caprolactam, N-vinyl formamide, vinyl ethers and styrene. N-Vinylcaprolactam (VCAP) is a particularly suitable vinyl monomer for inclusion in the compositions used to make the receptive coatings of the present invention due to its sufficient adherence to the optical disk substrate. It has been found that Vinyl ether compounds include α, β-unsaturated ether monomers such as triethylene glycol divinyl ether, diethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether and ethylene glycol monovinyl ether, and ethyl 1-propenyl ether, Triethylene glycol methyl propenyl ether, triethylene glycol methyl vinyl ether and 2-cyclopenten-1-yl ether can also be used. Other monomers include acryloyl morpholine.

  Suitable oxygen-containing ring-opening monomers include those containing an oxetane ring or an oxirane ring. Oxirane species include alicyclic oxiranes (also known as epoxides), such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and polyol glycidyl ethers. Oxiranes derived by epoxidation of unsaturated materials may also be suitable, for example, epoxidized soybean oil, epoxidized polybutadiene or epoxidized alkenes. Oxetane species include monofunctional and polyfunctional oxetanes (eg, 3-ethyl-3-hydroxymethyl-oxetane, bis [(1-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3-[( 2-ethylhexyloxy) methyl] oxetane, [1,4-bis (3-ethyl-3-oxetanylmethoxy) methyl] benzene and trimethylolpropane oxetane, many additional suitable materials known to those skilled in the art Yes.

It is preferred that the prepolymer and monomer are selected to have a high surface tension so that the composition has a higher surface tension than the ink jet ink printed thereon. For example, the prepolymer preferably has a surface tension of at least 35 mN / m (dynes / cm ² ), more preferably at least 38 mN / m (dynes / cm ² ), while the monomer is preferably at least 32 mN. / M (dynes / cm ² ), more preferably at least 35 mN / m (dynes / cm ² ).

  The receptive coating may be free radical curable, cationic curable, or cured by a combination of the two mechanisms. It may also be cured by an electron beam. If the coating is cured by UV energy, a photoinitiator may be necessary. The nature of the photoinitiator used depends on the desired curing mechanism, but is otherwise not critical to the present invention. Photoinitiators can be of the split or hydrogen abstraction type, preferably the following initiator classes: benzophenone, thioxanthone and related compounds, hydroxyalkylphenones, aminoalkylphenones, anthraquinones, standard and modified acylphosphine oxides (E.g. Lucirin TPO and TPO-L), bis-acrylophosphine oxide (e.g. Irgacure 819), benzyl ketal, benzoin ether, acetophenone, beta ketosulfone, oxime ester and phenylglyoxylate. Specific examples of such cationic photoinitiators include sulfonium salts (eg, a mixture of compounds available under the trade name UVI6992 from Dow Chemical), thianthrenium salts (eg, Lamberti). Available Esacure 1187), iodonium salt (eg, IGM440 from IGM), phenacylsulfonium salt, and thioxanthonium salt sold under the trade names IGM550 and IGM650 by IGM. (For example, those described in WO03 / 072567A1, WO03 / 072568A1 and WO2004 / 055000A1 are disclosed in this document. Incorporated herein by reference).

  Further examples of photoinitiators, synergists and sensitizers are described, for example, in G.I. Edited by Bradley and published in 1998 by John Wiley and Sons in collaboration with SITA Technology Limited. V. Crivello and K.M. According to the Dietliker "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", Vol. 3, "Photoinitiators for Free Radical Cationic and Anionic Polymerisation", the second edition, as well as "Exploring the Science, Technology and Applications of UV and EB Curing ", R.C. S. Davidson, SITA Technology Ltd. , London, 1999, can be found in standard texts, the disclosures of which are incorporated herein by reference.

  The initiator used is preferably one that does not require the further use of an amine synergist, in particular a composition that does not contain a non-acrylated free amine synergist.

  The receptive coating is preferably white, but generally the photoinitiator is preferably resistant to yellowing. However, for other colors this is not necessary.

  Generally, when the receptive coating is applied by screen printing, the receptive coating sufficiently wets the optical disc substrate to form a film on the substrate. The receptive coating adheres well to the disk material or spin coat and allows the receptive coating to adhere well to the disk without swelling or otherwise deforming the disk material, thereby ensuring good quality. Promotes adhesion.

  The composition of the present invention also includes a surfactant to improve, for example, smoothness, wetting and antifoam properties. These surface active materials are difficult to move on the coating surface, thereby adversely affecting its acceptability. Suitable materials do not include silicone and can be natural polymers. Examples of such compounds include acrylate polymers, mineral oil mixtures, low temperature wax dispersions and paraffin wax dispersions (eg, Modaflow ™ (Cytec), BYK A501 (BYK), Bevaloid 6681 (Rhone Poulenc), BYK 1790. , BYK A500, BYK A560, Tego Airex 910 and Tego Airex 920 (Goldschmidt)), which may help in the de-arrangement of uncured compositions. If desired, a fluorosurfactant can be added to the composition to improve surface wetting during application. Commercial examples of such fluorosurfactants include Zonyl FSN100, Zonyl FSO100 from Dupont, and Fluorad 4430 from 3M.

  The composition used to make the receptive coating of the present invention may optionally include a pigment or other colorant, preferably a pigment. In the context of the present invention, the term “colorant” encompasses substances of a color that are actually visible, preferably white. White pigments are typically included in amounts of about 40% to 50% by weight of the total composition. However, the actual amount of colorant used will vary widely depending on the nature of the colorant, for example within the range of 1% to 60% by weight, more preferably 7% to 50% by weight. May be. If it is desired that the coating be transparent, no colorant need be included.

  Broadly speaking, colorants can be considered to be classified into two classes, namely dyes, which are sufficiently soluble in the ink composition and pigment, which are suitable dispersions if necessary. Is dispersed in the ink composition in the form of fine particles. Pigments are available in a wide range of classes, for example, Pigment Red 146, Pigment Red 170, Pigment Red 48: 2, Pigment Red 122, Pigment Blue 15: 3, Pigment Violet 23, Pigment Green 7, Pigment Yellow 83, Pigment Yellow 13, Pigment It can be selected from yellow 17 and pigment black 7. Other examples of suitable pigments are described in “Printing Ink Manual”, 4th edition, Leach R.M. H. (Eds.), Van Nostrand Reinhold, Wokingham, (1988), the disclosure of which is incorporated herein by reference. However, when used, the pigment is preferably a white pigment, such as Pigment White 6 titanium dioxide (eg, Kamera RDI-S, Kronos 1070, Kronos 1071, Tipure R706) or zinc oxide, zinc sulfate or barium sulfate. Of these, titanium dioxide is preferred. If desired, a combination of any two or more of these colorants can be used to achieve a particular effect.

  These formulations may also include extenders and fillers to further improve the properties and appearance of the ink both during and after the printing process. Representative examples of preferred fillers and extenders are the synthetic and natural grades of chalk, talc, kaolin and other aluminum hydroxides and silicates. They are known under many commercial trade names, such as Calcigloss, Microtalc, Speswhite, Spacerite and Zeolex.

  These formulations may also be modified with small amounts of structuring agents (eg fumed silica or activated bentonite) to produce favorable rheological properties in the screen printing process. Examples of such materials are Aerosil from Degussa, Bentone SD1, Bentone SD2, Bentone 34 from Elementis and Tixogel DS, Tixogel VPA, Tixogel MP100 from Sud Chemie.

  The various components of the composition of the present invention may be present in a wide range of amounts, depending on the desired physical and chemical properties of the final cured coating. In general, however, we have 1% to 60% by weight of the radiation curable prepolymer, more preferably 20% to 40% by weight; 5% to 60% by weight of the radiation curable monomer, more preferably Is 20% to 40% by weight, 0% to 15% by weight of the photoinitiator, more preferably 0% to 8% by weight, 0% to 5% by weight of the smoothing agent, preferably 0% to 3%. % By weight, (if used) 1% to 60% by weight of pigments and / or fillers and / or extenders, preferably 7% to 50% by weight, (if used) 0.1% of structuring agent It is preferred to use from 8% to 8% by weight, preferably from 0.2% to 5% by weight.

  The compositions of the present invention can be made by simple mixing and dispersion techniques well known to those skilled in the art and applied to optical disks by any well known printing technique (eg screen printing, spin coating, pad printing or flexographic printing, preferably screen printing). Can be applied. The entire surface of the optical disc may be coated or only a portion may be coated. The coating can then be cured using any well-known radiation curing technique.

  The invention further illustrates the following non-limiting examples.

(Example 1)
The following screen ink composition was prepared by first premixing the materials, and then the resulting mixture was ground to a powder of less than 12 microns (μm) on a three roll mill.

The obtained screen ink composition was printed through a 150-31 mesh on a light medium substrate (CDR, DVD-R) and cured using a medium pressure mercury lamp (80 Wcm ⁻¹ ). Four color high resolution test images were inkjet printed onto a coating cured with a XAAR Omnijet 318 piezoelectric DOD printhead and a commercial UV inkjet ink by UV curing. The resulting prints were evaluated for image quality and durability. The results are shown in Table 1 below.

(Example 2)
The following screen ink composition was prepared by first premixing the materials, and then the resulting mixture was ground to a powder of less than 12 microns (μm) on a three roll mill.

The obtained screen ink composition was printed through a 150-31 mesh on a light medium substrate (CDR, DVD-R) and cured using a medium pressure mercury lamp (80 Wcm ⁻¹ ). Four color high resolution test images were inkjet printed onto a coating cured with a XAAR Omnijet 318 piezoelectric DOD printhead and a commercial UV inkjet ink by UV curing. The resulting prints were evaluated for image quality and durability. The results are shown in Table 1 below.

(Example 3)
The following screen ink composition was prepared by first premixing the materials, and then the resulting mixture was ground to a powder of less than 12 microns (μm) on a three roll mill.

The obtained screen ink composition was printed through a 150-31 mesh on a light medium substrate (CDR, DVD-R) and cured using a medium pressure mercury lamp (80 Wcm ⁻¹ ). Four color high resolution test images were inkjet printed onto a coating cured with a XAAR Omnijet 318 piezoelectric DOD printhead and a commercial UV inkjet ink by UV curing. The resulting prints were evaluated for image quality and durability. The results are shown in Table 1 below.

(Example 4 comparison)
In this example, a silicone defoamer is used in place of the silicone-free smoothing agent of the present invention.

  The following screen ink composition was prepared by first premixing the materials, and then the resulting mixture was ground to a powder of less than 12 microns (μm) on a three roll mill.

The obtained screen ink composition was printed through a 150-31 mesh on a light medium substrate (CDR, DVD-R) and cured using a medium pressure mercury lamp (80 Wcm ⁻¹ ). Four color high resolution test images were inkjet printed onto a coating cured with a XAAR Omnijet 318 piezoelectric DOD printhead and a commercial UV inkjet ink by UV curing. The resulting prints were evaluated for image quality and durability. The results are shown in Table 1 below.

(Example 5)
The following screen ink composition was prepared by first premixing the materials, and then the resulting mixture was ground to a powder of less than 12 microns (μm) on a three roll mill.

The obtained screen ink composition was printed through a 150-31 mesh on a light medium substrate (CDR, DVD-R) and cured using a medium pressure mercury lamp (80 Wcm ⁻¹ ). Four color high resolution test images were inkjet printed onto a coating cured with a XAAR Omnijet 318 piezoelectric DOD printhead and a commercial UV inkjet ink by UV curing. The resulting prints were evaluated for image quality and durability. The results are shown in Table 1 below.

Claims (14)

  An optical disk having an optically readable surface and a printing surface, wherein the printing surface is formed by radiation curing a composition comprising a prepolymer, at least one monomer and a smoothing agent. An optical disc, wherein the composition does not contain any surface modifiers that interfere with printability, and the cured composition is insoluble in water and is not absorbed by water.   The optical disk according to claim 1, wherein the smoothing agent is a polymer acrylate, a mineral oil mixture, a low-temperature wax dispersion, or a paraffin wax dispersion, and does not contain silicone.   The prepolymer is epoxy acrylate, acrylated oil, urethane acrylate, polyester acrylate, polyether acrylate, acrylated amine, acrylic saturated resin, acrylate acrylate, cycloaliphatic epoxide, phenol epoxy novolac or acrylated epoxidized soybean oil. The composition according to claim 1 or 2.   The composition of claim 3, wherein the prepolymer is an epoxy acrylate. The composition according to claim 1, wherein the prepolymer has a surface tension of at least 35 mN / m (dynes / cm ² ). The composition of claim 5, wherein the prepolymer has a surface tension of at least 38 mN / m (dynes / cm ² ).   The composition according to any one of claims 1 to 6, wherein the monomer is an acrylate, a methacrylate, a vinyl compound or a compound polymerizable by a ring-opening mechanism. The composition according to claim 1, wherein the monomer has a surface tension of at least 32 mN / m (dynes / cm ² ). The composition of claim 8, wherein the monomer has a surface tension of at least 35 mN / m (dynes / cm ² ).   Furthermore, the composition of any one of Claims 1-9 containing a photoinitiator.   A method for making an optical disc having an optically readable surface and a printing surface, wherein the composition comprises a prepolymer, at least one monomer and a smoothing agent, wherein the ultraviolet energy, photoinitiation Cured by an agent, the composition does not contain any surface modifiers that interfere with printability, the cured composition is water insoluble, not absorbed by water, applied to the printed surface, and radiation cured The way it is.   The method according to claim 11, wherein the composition is any one of claims 2 to 10.   13. A method according to claim 11 or claim 12, wherein the coating composition is applied to the optical disc by screen printing, spin coating, pad printing or flexographic printing.   A process in which a radiation curable jet ink is jet printed onto a printing surface of an optical disc according to any one of claims 1 to 10 and then radiation cured.