The surface resistivity of polycarbonate resin is reduced and thus the antistatic properties improved by the inclusion of esters of branched fatty acids and polyhydroxylic compounds having at least one and desirably at least two free hydroxyl groups e.g. glycerol mono-iso-stearate. The reduction in surface resistivity can be acheived without a significant increase in haze or yellowness.

This invention relates to the use of surfactant compounds and compositions, particularly those based on esters of fatty acids, especially esters of polyhydroxylic compounds and branched fatty acids, as antistatic agents additives in polymeric, particularly polycarbonate, resins.
Polycarbonate resins are a widely used class of engineering polymer and are usually based on repeat units of a carbonate ester of a dihydroxyl aromatic compound most usually including a 1,4-phenylene (para-phenylene) group, and commonly of a bisphenolic compound such as Bisphenol A, 2,2-bis(4-dihydroxyphenyl)propane. As well as being strong and tough, polycarbonates can be fabricated as optically clear components e.g. in spectaclesxe2x80x94polycarbonate resins are frequently used in protective spectacles and goggles even where there is no optical support for poor sightxe2x80x94and as windows. Polycarbonate resins are typically good insulatorsxe2x80x94they are used as dielectric materials in capacitorsxe2x80x94and static charge on such resin surfaces may not disperse readily. Where polycarbonate resin is exploited solely for its strength and toughness, it is possible to render it anti-static by using ionic materials to increase its effective conductivity, but generally these additives give rise to opacity e.g. as haze, or discolouration e.g. as yellowing, in the compounded resins and are thus not suitable for applications where optical clarity is important. Hydrophilic antistatic agents have not generally proved to be effective in polycarbonate resin systems and in any case frequently give rise to haze, yellowing or other opacity and would thus be of limited value even if effective.
The present invention is based on the discovery that good antistatic properties can be obtained in polycarbonate resins by using esters of branched fatty acids and polyhydroxylic compounds as antistatic agents. In contrast, we have found that esters of non-branched fatty acids and polyhydroxylic compounds are much less effective as antistatic additives in polycarbonate resins.
Accordingly, the present invention provides a polycarbonate resin containing one or more esters of at least one branched fatty acid and at least one polyhydroxylic compound in an amount to provide effective antistatic activity. The invention includes the use of such esters as antistatic agents in polycarbonate resins and in particular polycarbonate resins fabricated as optically clear components such as sheets or lenses.
The term xe2x80x9cpolyhydroxylic compoundxe2x80x9d is used to refer to compounds which have two or more hydroxyl groups and which when made into esters for use in this invention retain at least one free hydroxyl group.
The antistatic agents used in this invention are esters of branched fatty acids. The fatty, usually alkyl, residue of the fatty acid is a relatively hydrophobic group which provides satisfactory compatibility with the polymer resin. Typically the branched fatty acids contain at least about 8 carbon atoms. Lower molecular weight acids generally have esters that are either not sufficiently compatible with or are too readily removed from the polymer resin to be satisfactory as antistatic agents. Desirably, the branched fatty acid contains at least 12, and more usually at least 14, carbon atoms. The branched fatty acid may contain up to 30 carbon atoms, but usually not more than 22, and more usually not more than 20, carbon atoms because such acids are not readily available and their use does not appear to give any particular advantage.
Accordingly, particularly desirable esters of branched fatty acids for use in the present invention include those of the formula (I):
R1xe2x80x94CO2xe2x80x94R2xe2x80x83xe2x80x83(I)
where
R1 is a branched C11 to C21, particularly C13 to C19, aliphatic hydrocarbyl group, desirably an alkyl group;
R2 is the residue of a polyhydroxyl compound including at least one free hydroxyl group.
Within formula (I) the group R1 is desirably a branched alkyl group and within the C11 to C21 range given in formula (I), R1 is desirably a branched C13 to C19 alkyl, especially a branched C15 to C19 alkyl, group.
The invention accordingly specifically includes polycarbonate resin containing one or more esters of the formula(I) in an amount to provide effective antistatic activity; and the use of esters of the formula(I) as antistatic agents in polycarbonate resins and in particular polycarbonate resins fabricated as optically clear components such as sheets or lenses.
Typically, the fatty acids, containing such aliphatic hydrocarbyl groups, which are used in the esters used in the invention are derived from natural sources or distillation cuts and typical commercially available materials are mixtures of compounds with a spread of chain lengths. The carbon chain lengths referred to herein are average chain lengths.
The fatty acids used in the invention are branched chain acids, more usually fatty acids having a branched alkyl chain. The branching can be at various positions along the chain for example near the carboxyl function, e.g. at the 2- or 3-position, particularly at the 2-position, or more remote from the carboxyl function e.g. about half way along the chainxe2x80x94corresponding to about position 9, for example from position 6 to position 12, for a C18 alkyl group.
Generally, the fatty acids have a main chain and a branch off the main chain which is relatively short compared with the main chain. Commonly the branching can be a lower alkyl group, particularly a C1 to C4 alkyl group and especially a methyl or ethyl group. A particularly useful type of branched fatty acids are methyl and/or ethyl branched fatty acids. The use of such lower alkyl, especially methyl, branched fatty acids, forms a specific aspect of this invention.
Particularly suitable esters include those commercially available as esters of so-called iso-stearic acid. The commercial product iso-stearic acid is a mixture of acids having from 14 to 22, with about 2/3 having 18, carbon atoms, including short, mainly methyl but also including some ethyl, side chains, branching from the main chain mainly in the middle of the chain, typically about the 9-position e.g. from about the 6-position to about the 12-position, in an 18 carbon molecule. The assay molecular weight (e.g. by acid number) is close to that of stearic acid. xe2x80x9cIso-stearic acidxe2x80x9d is a co-product (after separation and hydrogenation) from the manufacture of so-called xe2x80x9cdimer acidsxe2x80x9d from C18 unsaturated (mainly oleic and linoleic) fatty acids by catalytic thermal polymerisation.
Branched fatty acids for ester antistatic additives used in the invention include those of the formula (IIa):
[CH3.(CH2)n1][CH3.(CH2)m1].CH.(CH2)p1.COOHxe2x80x83xe2x80x83(IIa)
where
n1 is from 4 to 10, particularly from 6 to 8;
m1 is from 0 to 5, particularly 0 to 3 and especially 0;
p1 is from 4 to 10; particularly from 6 to 8; and
desirably n1+m1+p1 is from 10 to 18, particularly 12 to 16.
Branched acids within this group include those derived from natural sources e.g. animal or vegetable fats and waxes, particularly by reactions on unsaturated fatty acids e.g. oleic acid (octadec-9-enoic acid), to introduce branching at or near the site of unsaturation in the starting acid. Commercially available iso-stearic acid is an example of a fatty acid of the formula (IIa), in practice a mixture of fatty acids of this formula.
Further branched fatty acids for ester antistatic additives used in the invention include those of the formula (IIb):
[CH3.(CH2)n2][CH3.(CH2)m2].CH.(CH2)p2.COOHxe2x80x83xe2x80x83(IIb)
where
n2 is from 6 to 18, particularly from 10 to 16, especially about 14;
m2 is from 0 to 5, particularly 0 to 3;
p2 is from 0 to 3, particularly 0 to 2; and
desirably n2+m2+p2 is from 10 to 18, particularly 14 to 16.
Such branched acids can be derived from synthetic sources e.g. by oxidation of alcohols made by the OXO reaction on internal linear olefins (where p2 is 0); on branched (typically 1-) olefins (where p2 depends on the position of branching in the alkyl group); on vinylidene (2,2 di-alkyl) olefins (where p2 is 1); or Guerbet alcohols (where p2 is 0); such acids are available from Condea under the trade name Isocarb e.g. Isocarb 16 (C16), Isocarb 18 (C18) and Isocarb 20 (C20). Particularly where the alcohols are made by the OXO reaction, and especially by OXO reaction on linear internal olefins, the products will generally be mixtures of isomers as will the acids and thus the esters made from them.
The branched chain acids will usually be mixtures of more than one compound in the position and/or length of the side chain and/or in the total number of carbon atoms.
Practically available branched fatty acids will usually be mixtures including non-branched acid residues as well as branched acid residues. The corresponding esters which can be used in this invention will thus also include mixtures of branched and straight chain fatty acid residues. Desirably the proportion of ester having branched acid residues is at least 40%, more usually at least 50%, desirably at least 75% and may be higher e.g. more than 80% such as about 90%, by weight of the total ester additive. Thus commercially available esters of iso-stearic acid when used in this invention will typically include some corresponding esters of stearic acid (the straight chain isomer).
As is mentioned above, the source of fatty acids is commonly natural, materials especially animal and vegetable fats and waxes, which in their natural state will often contain significant levels of unsaturated fatty acids. The presence of unsaturation in antistatic agents used in polycarbonate resins may be a source of yellowing or other discoloration during incorporation of the ester additives into the polycarbonate, processing of the resin, or in subsequent use, especially in sunlight. Desirably, the level of unsaturation of fatty acid residues in esters used in the invention is low, typically less than 10%, and more usually less than 5%, and desirably not more than about 2%, of the fatty acid residues is unsaturated. Unsaturation is typically assayed by measuring the Iodine value [in g.I2(100 g product under test)xe2x88x921] and for C18 fatty acids and their near analogues these figures correspond approximately to iodine values of less than 9, more usually less than 4.5, and desirably not more than about 1.8. For fatty acids with different molecular weights the respective Iodine values will vary (inversely) with molecular weight. Iodine values may be measured on precursor fats or oils, usually fatty acid triglyceride esters, and similarly allowance for the higher molecular weight and the presence of more than one fatty residue per molecule will need to be made in converting between Iodine values and percent unsaturation. The level of unsaturation can be reduced by refining and/or hydrogenation of the source oils or fats or of the fatty acids themselves. Commercially, cosmetic grades of the fatty acids or their esters are available having low levels of unsaturation and such materials are convenient sources of material for use in this invention.
The alcohol part of the esters used in this invention is a residue of a polyhydric alcohol including at least one, and desirably from 2 to 7, particularly 2 to 5, free hydroxyl group(s), and particularly residues of polyhydroxyl compound containing from 3 to 10, especially 3 to 6, carbon atoms and having 2 to 5 free hydroxyl groups. Examples include glycols such as ethylene and propylene glycol, glycerol and polymerised derivatives of glycerol, especially diglycerol and triglycerol. In the compounds of the formula (I), the group R2 is the residue of a polyhydroxyl compound including at least one free hydroxyl group and is desirably the residue of such a compound containing from 3 to 10 carbon atoms and having 2 to 5 free hydroxyl groups. Practical ester materials may include a mixture of residues of more than one polyhydroxyl compound, particularly where the polyhydroxyl compound is a polymeric (or oligomeric) material such as polymerised derivatives of glycerol. Just as unsaturation is desirably minimised in the fatty acid, the alcohol component of the ester is desirably not unsaturated and will desirably be selected to avoid introducing thermal instability. Accordingly reducing sugars are not generally useful for the alcohol part of the ester because of their poor thermal stability although non-reducing sugars or their derivatives can be used e.g. sorbitan esters of branched fatty acids, although they are not especially preferred.
The esters used in the invention have at least one free (non-esterified) hydroxyl group. Especially where the alcohol residue is of a polyhydroxyl compound only having 2 hydroxyl groups, the ester will be or include a major proportion of a mono-ester. Desirably, even where there are more hydroxyl groups in the alcohol precursor of the ester, the ester is a mono-ester or includes a high proportion of mono-ester. The proportion of mono-ester is desirably at least 50%, more usually at least 70% and particularly at least 85%. We have obtained good results using commercially available glycerol esters of iso-stearic acid, particularly those having a mono-ester content of at least 50% and up to about 90% and especially the low (less than 2%) unsaturation cosmetic grades of these esters. Where the alcohol residue is of a polyhydroxyl compound having more than 2 hydroxyl groups, esters including more than one fatty acid residue may be used, but it is still desirable that the ester(s) used have 2 or more hydroxyl groups. Generally it is desirable that the ester(s) include not more than 2 fatty acid residues even where there are 2 or more free hydroxyl groups. Examples of such materials include di-esters of polyglycerols. Thus, it is generally desirable that the number of free hydroxyl groups is at least as great as, and particularly is greater than, the number of fatty acid residues in the molecule of the antistatic agent.
In practice, the esters used in the invention are likely to be mixtures of compounds. The use of such mixtures is likely to contribute to the esters being liquid (at ambient temperature).
Especially desirable compounds of the formula (I) include those of the formula (Ia):
R1axe2x80x94CO2xe2x80x94R2axe2x80x83xe2x80x83(Ia)
where
R1a is a C13 to C19, especially a C17, branched alkyl group, particularly where the branch chains are methyl or ethyl groups;
R2a is the residue of a polyhydroxyl compound containing from 3 to 10 carbon atoms and having 2 to 5 free hydroxyl groups, especially a glyceryl residue.
The esters can be made by direct esterification of the fatty acid(s) with the polyhydroxyl compound(s) or, particularly where the polyhydroxyl compound is glycerol, by partial hydrolysis of higher esters, especially triglycerides.
The polycarbonate resins used in the invention are polyester polymers having repeat units of a carbonate ester of a dihydroxyl aromatic compound. Typically, the dihydroxyl aromatic compound is or includes a 1,4-phenylene (para-phenylene) group, and commonly it is a bisphenolic compound in which two 1,4-phenylene groups are connected through a linking group. The most common such compound used today in polycarbonate resins is Bisphenol A, 2,2-bis(4-hydroxyphenyl)propane. Combinations of two or more dihydroxyl aromatic compounds can be used in copolymeric polycarbonates and Bisphenol A is often used in combination with hydroquinone (or methyl substituted hydroquinone e.g. 1,4-dihydroxy-3-methylbenzene) as the dihydroxyl aromatic compound. As used in this invention, the polycarbonate resins are desirably polymers including the repeat unit: xe2x80x94Oxe2x80x94C(O)xe2x80x94Oxe2x80x94Arxe2x80x94 where: Ar is the residue of a dihydroxyl aromatic compound. Particularly desirably, the group Ar is a group of the formula: xe2x80x94Ph1xe2x80x94R1xe2x80x94Ph1xe2x80x94 where:
each group Ph1 is independently a 1,4-phenylene group, which may be unsubstituted or substituted with one or more lower, particularly C1 to C3, alkyl groups and/or one or more halogen, particularly bromine, atoms; and R1 is a linking group.
In such compounds, the linking group R1 is particularly a group xe2x80x94Oxe2x80x94; xe2x80x94Sxe2x80x94; xe2x80x94SO2xe2x80x94 e.g. as in the residue of Bisphenol S; xe2x80x94C(O)xe2x80x94 e.g. as in the residue of 4,4xe2x80x2-dihydroxybenzophenone; or xe2x80x94C(R2)(R3)xe2x80x94, where R2 and R3 are each independently a hydrogen atom; an lower, particularly a C1 to C3, alkyl group, which may be substituted with one or more halogen atoms, in particular both are methyl groups e.g. as in the residue of Bisphenol A; a cycloalkyl, particularly a cyclohexyl, group; or an aryl, particularly a phenyl, group; or R2 and R3 together form a divalent cyclic group e.g. a cyclohexylene or cyclopentylene group, which may be optionally alkyl substituted e.g. as in a 3,3,5-trimethylcyclohexylene group.
Particularly, for resins having low birefringence, as are especially useful in optical applications as in compact disk products, the group Ar may include spiro-linked 1,4-phenylene groups e.g. of the formula:
Polycarbonate resins used in this invention typically have molecular weights in the range 10000 to 100000, more usually 20000 to 60000. In practice, Melt Flow Index (MFI) is often used as a measure of molecular weight (because melt viscosity is related to molecular weight for similar polymers) and the polycarbonate resins used in this invention typically have MFI values up to 70 and usually at least 2 g. 10 minxe2x88x921, more usually from 5 to 40 g. 10 minxe2x88x921. We have obtained good results from polycarbonate resins having MFI""s in the range 5 to 35 g.10 minxe2x88x921.
The surface resistivity of unfilled, untreated polycarbonate resin is typically of the order of 15 log(ohm.squarexe2x88x921). To acheive satisfactory antistatic properties it is desirable to reduce the surface resistivity to not more than about 12, and desirably not more than about 11.5, log(ohm.squarexe2x88x921).
As is mentioned above, polycarbonate resin containing an antistatic agent according to the invention can be fabricated as optically clear components, such as sheets or lenses. In such products, the polycarbonate resin products typically have low haze and low colour (as measured by Yellowness Index). Typically, optically clear polycarbonate resin components have Haze values [typically measured as percentage Haze on standard 2.5 mm thick injection moulded test plaques] of less than 10, more usually less than 5 and typically from 2 to 3. Inclusion of antistatic agents as used in this invention even at levels well above those needed to obtain satisfactory antistatic performance gives Haze values which are not substantially different from those of untreated polycarbonate resin and are usually within the ranges given above. For example test plaques of a polycarbonate resin containing no antistatic agent had a Haze value of 2.6 and a similar test plaques containing 4% by weight (based on the polycarbonate) of cosmetic grade glycerol mono-iso-stearate (itself about 90% iso-stearate ester)xe2x80x94about twice the amount needed to have a generally suitable antistatic effectxe2x80x94had a Haze value of 2.7. The colour [for example as measured by the Yellowness Index (YI) on standard 2.5 mm thick injection moulded test plaques] of optically clear polycarbonate resin components is also important in practice. Tests on samples as described above, including antistatic agent according to this invention, even at levels well above those necessary to achieve satisfactory antistatic properties, typically give values of about 2xe2x80x94substantially the same as untreated polycarbonate resin.
The invention accordingly includes polycarbonate resin having:
1 a surface resitivity of not more than 12, preferably not more than 11.5, log(ohm.squarexe2x88x921);
2 a Haze units value of not more than 5, more usually from 1.5 to 3.5 and preferably 2 to 3; and optionally but desirably
3 a Yellowness Index of not more than 5, more usually from 1.5 to 3.5 and preferably 1.8 to 3.
In particular the invention includes polycarbonate resin having such surface resitivity; Haze units value; and Yellowness Index values in which the polycarbonate is rendered antistatic by the inclusion of at least one esters of at least one branched fatty acid and at least one polyhydroxylic compounds; especially where the ester is at least one compound of the formula (I) or (a) as defined above.
Suitable commercial materials are available under the trade designations Lexan from General Electric, Makrolon from Bayer, Calibre from Dow and Panlite from Idemitsu.
The amount of the antistatic agent used in the polycarbonate resin formulations according to this invention will be sufficient to provide an antistatic effect. Typically the minimum amount to be effective is about 0.2% by weight of the formulation, although the amount used will usually be at least 0.25%. The maximum amounts will typically be about 5.0% by weight of the formulation, and amounts above about 3% offer little further benefit and will not in general be used. We have obtained good results using amounts in the range 0.5 to 2.5% by weight of the formulation. Thus typical proportions of antistatic agent used based on the polycarbonate resin are:
Desirably the amount of compound(s) of the formula (I) above is within these ranges.
Usually it will be convenient to incorporate the antistatic agent uniformly in the polycarbonate resin. However, it may be desirable to have a higher concentration of the antistatic agent (than in the remainder of the polycarbonate resin) in one or more layers [high concentration layer(s)] at or near the surface of the polycarbonate resin product. The concentration of antistatic agent in such high concentration layer(s) may be similar to the concentrations indicated above for uniform incorporation, thus using less antistatic agent overall.
Alternatively, the concentration in high concentration layer(s) may be higher than would generally be used for uniform incorporation e.g. from 2.5 to 10%, particularly 3 to 7% by weight of the polycarbonate resin in the high concentration layer(s). The use of such high concentration layer(s) can give a longer lasting antistatic effect without overall using uneconomically large amounts of antistatic additive. Where the concentration in the high concentration layer(s) is substantially above that used in uniformly treated polycarbonate resin, it will often be in a layer just below the exposed surface of the polycarbonate resin product and may have overlying it a thin layer that has a more normal concentration of antistatic additive. Such overlying thin layers are often only from 1 to 5 xcexcm e.g. 1.5 to 3 xcexcm, thick and the underlying high concentration layer will typically be from 5 to 100 xcexcm, particularly 10 to 50 xcexcm thick.
Multilayer structures of these types can be fabricated e.g. by coextrusion to give multilayer film products, or by coating particularly by extrusion or coextrusion coating onto suitable substrates.
The polymer resin compositions can and typically will usually include other components typically as minor constituents usually totalling less than about 10% of the formulation, such as antioxidants especially UV stabilisers, and mould release agents.
Suitable antioxidants are particularly UV stabilisers such as those sold under the trade names Tinuvin 234, Tinuvin 360, Tinuvin 1577 and Irganox 1076 by Ciba and are used typically in amounts as recommended by the respective manufacturers and generally in the range 0.05 to 1%, particularly 0.1 to 0.5%, by weight of the overall composition. Combinations of antioxidants/UV stabilisers can be used as is common is the art using total amounts of such additives typically from about 0.5 to 1% by weight of the overall composition.
Mould release agents are typically fatty acid monoglycerides such as glycerol mono-stearate. The levels used are typically from 0.1 to 0.5% by weight of the resin formulation. The branched fatty acid esters used in this invention are generally used at much higher levels that is usually appropriate for mould release agents and it appears that the antistatic additives provide mould release properties. In any event we have not found it necessary to use separate mould release agents although they can be used if desired.
Of course, where the intended end use of the polycarbonate resin formulation is in or as an optically clear component, product or material, any additives will be selected so that they do not interfere with the desired optical properties of the component, product or material.
We have found that the antistatic agents used in this invention can readily be incorporated into the polycarbonate resin which it is desired to render antistatic. The antistatic can be incorporated into the resin by generally conventional methods, typically by including the antistatic as a component in formulating the resin before moulding or casting and in particular by melt blending techniques, for example using Banbury mixers or extruders. For example, the antistatic agent additive can be melt blended into the polymer resin in an extruder, with the additive being fed into the extruder premixed with the polycarbonate resin e.g. by dry blending polycarbonate resin granules with powdered additive or by mixing granules of polycarbonate resin and of additive masterbatch in a similar polymer, or by being fed as a side stream into the extruder as the molten polycarbonate resin proceeds through it. The blended material can be granulated e.g. by extrusion and cutting e.g. for subsequent manufacture into desired forms such as sheet e.g. windows, and moulded products, including optical components such as lenses. Masterbatches of the antistatic agent in polycarbonate resin can be made as granules by such methods and the polycarbonate polymer resin base of the masterbatch need not be the same as the main polycarbonate polymer resin of the product formulation (but in practice will be miscible with it).
The polymer products of this invention incorporating the antistatic additive can be used to make a variety of products as typically made from the polymer resin materials. In particular we expect that the compositions of this invention will find application in self-supporting films for packaging, as film coatings on, particularly sheet or tile, substrates, and in polymer resin formulations for casting and moulding.
When the polycarbonate resins formulated including an antistatic agent according to the invention are used in making moulded products e.g. sheet products (including lenses and similar optical components), the antistatic agent will typically be used to inhibit or prevent surface dust pick up and this can be a very useful feature of such products. Even where antistatic performance is not particularly important in, particularly moulded, end products, intermediate processing may be simplified if the polycarbonate resin is treated according to the invention. The lower surface resistivity may well reduce the extent of static build up and thus the risk of getting electric shocks from material being formed.


In an example, a method for controlling termination of a print procedure subsequent to a node reset within print apparatus including a plurality of nodes includes identifying the node at which the reset occurred, and controlling operation within the print apparatus by way of a selected node. The selected node is different from the identified node and selected responsive to the identification of the identified node for operation of a component of the print apparatus as part of a termination procedure.

A printing process within a printing apparatus or press can terminate for a wide variety of reasons. Unexpected print terminations can lead to damage of component parts such as subsystems and consumables/supplies within the printing engine of the printing apparatus. This can shorten the operational life of such components, requiring replacement and also impacting on the operational efficiency of such components and thus the printing apparatus.
Within a printing apparatus of the disclosure, and which can comprise any form of printing apparatus including inkjet printers, dry toner printers and 3D printing apparatus, a printing operation is controlled to produce printed media and this can involve a variety of different subsystems controlled by way of a plurality of nodes, that are to function in a synchronised manner and to satisfy many control conditions.
Components of the printing apparatus of the disclosure, and which can comprise components of any form of printing apparatus including inkjet printers, dry toner printers and 3D printing apparatus, need to be intact to assure proper outputted printed media. When print defects occur on the printed media those components causing the print defects need to be replaced to allow resuming the generation of proper outputted printed media. In most cases the components requiring replacement are consumables/supplies such as printing blanket, photoconductor (PIP), binary ink developer and charge roller. These consumables/supplies are designed to be replaceable by press operators. In certain cases, more complicated failures occur which may require replacing sub-assemblies and even entire subsystems. Examples of sub-assemblies are sensors, belts, bearings, gears, brackets, tubes, fittings. Subsystems refer to a combination of sub-assemblies which perform specific functions within the printing apparatus.
In many instances, print termination can occur in a normal, wholly predictable, manner. Operation of the various subsystems of the apparatus can be modified in a controlled synchronised sequence in response to completion of a print job, for example when it is determined that no further jobs are queued and all print requests have been completed.
The controlled shutdown of the printing apparatus involves specific control actions, some of which can occur in parallel, while others can occur in series. Subsystems can be modified through activation, deactivation and/or by way of a change in operational parameters. Specific control actions can involve many of the components of the printing apparatus. Such control can serve to retain optimal print quality and avoid damage to components of the printing apparatus, such as the subsystems and consumables/supplies, and maintain their readiness for subsequent print sessions.
Sequences of control actions taken as part of print termination are referred to as a post print sequence. A hierarchical series of post-print sequences with various actions being taken in each sequence can be employed. For example, in a first phase, preparation for termination can involve clearing the paper path, interrupting liquid supply, sponge drying, Binary Ink Developer (BID) drying, heating-lamp deactivation and the switching-off of some voltages. During a second phase, the main motor is parking, all remaining voltages are switched-off and most components are switched to a non-printing state. In a third and final phase, all remaining subsystems are switched to a non-printing state and operation of the main motor is stopped.
In addition to such normal predictable print terminations, triggers for print termination can also arise in an unpredictable and thus abnormal manner. These abnormal print terminations can arise for relatively trivial reasons, such as a paper jam within the paper-supply path, or when one of the many parameters that is controlled in the press reaches an invalid value, that is outside a predefined operational window defined by a minimum and a maximum value. The characteristics of abnormal print terminations are the opposite of normal terminations due in particular to the unpredictable nature of abnormal terminations.
Abnormal print termination sequences can vary broadly. In some cases, all three post-print phases are performed; in other cases a transition from the second to the third phase is performed; and in cases such as electronic board resets, or emergency stops, just the third phase is executed to induce an immediate stop. Thus, abnormal terminations are termination sequences in which certain parts of normal termination sequences are not performed with the intent of shortening the duration to completion. Such short-cuts can bypass specific sequences, or parts of sequences, so that the expected procedure is not followed. The characteristics of abnormal termination sequences may depend on the trigger initiating the abnormal termination.
The triggers for abnormal termination include parameters of urgency and severity and each of which is indicated at one of three levels of 'low', 'medium and 'high'. The combinations of urgency and severity associated with the source of an abnormal termination trigger determine the termination sequence to be used to meet the abnormal termination request. As examples, print-media jams inside a feeding/stacking unit are categorized with medium urgency and severity; print-media jams inside a printing engine have medium severity but high urgency. Triggers arising from nodes, that as examples can comprise electronic boards or stored machine readable instructions such as, for example, a software routine, and controlling print apparatus subsystems, have a high severity and high urgency and arise when node resets occur. The print apparatus comprises a wide variety of nodes and resets arising at one node can cause all nodes to reset thereby causing the print apparatus to shut down as quickly as possible and without delay to allow for modification or completion of operation of component parts of the printing apparatus. Such immediate shut down can lead to damage of the component parts of the printing apparatus such as subsystems and consumables/supplies.
Damage to parts of the printing apparatus, such as subsystems and consumables/supplies, can interrupt their use, and shorten their lifespan. These damaged parts of the print apparatus can in turn lead to interruption of use of the apparatus, and increased inconvenience and expense for the user particularly if of the damaged consumable is to be replaced.
As a particular example of the damage that can arise, a common issue with a direct transition to the third post-print phase noted above that can occur during an abnormal termination is that ink remains on the consumables/supplies. Node resets can take in the region of 3-7 minutes to resolve and within that time, the ink can fuse onto the surfaces of the consumables/supplies. The fused ink can permanently damage the consumables/supplies, requiring replacement, or attempted repair, all of which can impact on print quality and increase the likelihood of print defects. In addition, damaged consumables/supplies can require replacement leading to added expense and inefficiencies and reducing productivity. The replacement of consumables/supplies leads to further requirements such as re-calibrations which further increase operational delays.
In an example, the printing engine of a digital print press may include three main transfer components which can comprise drums or belts, such as the photoconductor drum (PIP), the ITM drum with mounted blanket, and the impression drum for engaging with the media to be printed on. A printing sequence can involve writing a latent image on the PIP; engaging the Binary Ink Developer (BID) to transfer charged ink to the latent image on the PIP drum; transferring the ink to the blanket on the ITM drum; heating the ink on the blanket prior to final transfer to the media by interaction with the impression drum. Many supporting subsystems and consumables are employed in the printing press operation. Examples of such subsystems can comprise electromechanical devices include heating lamps, imaging oil system (ink liquid carrier), charging components, fitters, blowers, pumps. These press subsystems are controlled using various nodes such as machine readable instructions and electronic boards. During printing, ink can be transferred to and from consumables under the control of such subsystems, such as transfer between the PIP and the ITM blanket and so a sudden unexpected termination can leave ink on the surfaces of those consumables or part transferred there-between.
Termination instructions of different urgency can be initiated. For example, in some devices "Break Immediately" terminations can halt printing as fast as possible, irrespective of other considerations. "Break on Spread" terminations can allow printing of the current spread pages before termination and "Break on Separation" terminations can allow for completion of printing the current separation for a coloured image before termination.
"Break Immediately" terminations are examples of abnormal terminations that are likely to cause damage to the consumables and can be invoked by a node reset. For example, in some devices, node resets most commonly originate at the Paper Control Node (PCN) and the BID Control Unit (BDU) node. However, node resets can also be initiated by a Main Control Unit (MCU) node, a Power Distribution Board (PDB) node, a Main Ink Control (MIC) node, a Charge Roller Unit (CRU) node, and by a Drum Control Interface (DCI) node, and also within machine readable instructions, although it should of course be appreciated that this list is not complete and many other examples exist.
Once a trigger for a "Break Immediately" abnormal termination sequence has been initiated, an example of the disclosure can include identifying the node at which the reset occurred the reset and controlling operation of a selected component of the print apparatus responsive to the identified node for ongoing operation of the component as part of the termination procedure. Also, once the specific node is identified, some of the other nodes (that did not trigger a termination) can normally, or near-normally, terminate their operational sequences since the nodes are effectively independent. Thus, the non-triggered, independent nodes can continue normal or near-normal termination procedure. That is, in an example of the disclosure, a node reset comprises a local event in the network of nodes, rather a global event possibly affecting all nodes.
Examples of the disclosure can involve responding to an abnormal termination trigger in a more controlled/organised manner to reduce damage to consumables thereby maintaining print quality and reducing the likelihood of print defects. Reducing damage to the consumables can also increase their lifespan and so reduce inconvenience and expense for the user. The nodes, within the printing apparatus from which abnormal print termination triggers originate can be identified, and a termination sequence invoked allowing continued operation of selected subsystems for removal of ink from an associated consumable to reduce potential for damage prior to termination.
A method of the disclosure can comprise a "break immediately" protocol to respond to abnormal print termination scenarios. Examples of nodes that may trigger a reset are a paper control node, a main control unit, a power distribution board, a BID control unit, main ink control, charge roller unit and a drum control Interface, or machine readable instructions stored in the printing apparatus.
Examples of printing apparatus consumables that can benefit from termination procedure of the disclosure can include a PIP, ITM blanket and ink and oil handling/control elements for example within the cleaning station. Further, a node reset triggered from a control node of a BID unit can allow for ink already passed on by the BID to the PIP to continue to be transferred onto the blanket and media prior to termination. In this example the node reset at the BID may have damaged the BID, but the PIP and blanket can undergo normal termination sequences and the use of consumables can be properly deactivated, for example involving cleaning so as to have ink removed, and thereby be ready for next use. Printing can then efficiently resume without delay once the reset that initiated the abnormal termination has been resolved, since there is no damage to the components that needs to be addressed.
As a further example, and with a reset having been triggered at a Paper Control Node (PCN), ink can be transferred from the BID unit to the PIP, and the unit then initiate a dry BID sequence. The ink can be subsequently transferred from the PIP onto the blanket of the ITM so that use of consumables is properly deactivated, and for example cleaning of the BID unit and the PIP can occur. The reset arising at the PCN, and the inactivity at that node, prevents onward transfer of ink from the blanket of the Intermediate Transfer Member. Ink then remains on the blanket of the ITM prior to termination and so potential damage to the blanket can occur.
Examples of the disclosure can employ the autonomous operation of nodes within the printing apparatus such that a reset triggered at one node, does not affect ongoing operation by way of other 'non-reset' nodes. Examples of the disclosure can also seek to limit the damage that can occur to the components during abnormal termination. For example, this can serve to enhance the degree to which the use of consumables is properly deactivated, for example involving cleaning by removal of ink from consumables, prior to a print operation terminating. The node or nodes that continue to operate as part of a termination procedure subsequent to a node reset occurring at another node can be determined responsive to the identity of the node at which the reset occurred. For every node that can fail, there can be a predetermined selection of nodes that can continue to operate, either wholly or in part, as part of the termination procedure of the disclosure. The relationship between a failed node and those that can continue to operate as part of the termination procedure of the disclosure can be defined by any appropriate mapping technique.
Turning now to FIG. 1, an example of a print termination method 10 of the present disclosure is illustrated by way of a flow diagram in which a desired print procedure 12 is executing. During such operation, and upon a node reset being triggered at block 14 at one of the nodes of the printing apparatus and, the node that initiated the reset is identified at block 16.
The ongoing operation of subsystems affecting consumables/supplies of the printing apparatus is then controlled at block 18 in response to the identification of the node that triggered the reset. The ongoing controlled operation of the subsystems allows for the cleaning at block 20 of consumables of the printing apparatus prior to an example of abnormal termination of the disclosure, and so as to reduce print defects and maintain print quality.
In the illustrated example, the degree to which the use of consumables is properly deactivated, for example involving cleaning, or the consumable and/or subsystem brought to a non-printing state that is not damaging for future use is improved. As an example of the disclosure, the proper deactivation can prevent fusing of ink on the consumables and the related reduction in print quality, but also enhance efficiency in operation by rendering the consumables ready to use once the reset has been resolved. Of course, damage to consumables/supplies can arise otherwise than from ink remaining on consumables. Damage can also arise for other reasons such as from prolonged engagement and/or voltages while the consumables are not wet by imaging oil.
A further particular example of a print termination method 30 is illustrated by way of the flow diagram of FIG. 2 in which, during a print procedure at block 32 a BDU reset is triggered at block 34 at a BID control node. At block 36, it is determined that a BDU node is responsible for triggering the reset and, on the basis of that determination, subsystems and consumables/supplies downstream from the BID, can continue their normal operation. For example controlled use of the PIP, blanket and media supply continues by way of the selected related subsystems at block 38 so as to effect cleaning of the PIP, ITM and its blanket at block 40. Prior to abnormal termination, the PIP and blanket are cleaned through ink removal.
A yet further example of a print termination method 50 is illustrated with reference to the flow diagram of FIG. 3 in which ongoing printing process at block 52 experiences a node reset triggered from a PCN at block 54. At block 56, the source of the triggered node reset is Identified as the PCN and the ongoing operation of the selected subsystems associated with the BID, PIP and ITM is controlled at block 58 so as to permit transfer of ink from the BID unit to the PIP and onto the blanket of the ITM at block 60.
However, in the example illustrated in FIG. 3, no further transfer from the blanket is possible due to the nature of the node reset arising from the PCN. The BID unit and PIP can then have ink removed, so as to prevent damage thereto and assist with preparation for the subsequent operation. In this particular example, ink is not removed from the blanket of the ITM.
Turning now to FIG. 4, there is a schematic side view of a printing engine 70 of a digital printing press of the present disclosure and to operate according to an example of a print termination method of the present disclosure. The printing engine 70 comprises an array of BID units 72 which can include a yellow ink unit 72A, a magenta ink unit 72B, and a cyan unit 72C. Within the press there is a variety of subsystems and consumables/supplies that are involved in the supply, application, metering and removal of ink by the printing process. Subsystems and consumables/supplies are controlled and activated so that the consumables can perform their ink handling operations.
The engine further includes a photoconductor drum PIP 74, and a charging unit 76 and a cleaning unit 78 that are associated with the PIP 74. Also provided is an ITM drum 80 and outer blanket 82 for receipt of an ink image from the PIP drum 74. Associated with the ITM drum 80 is a heating unit 84 that assists with transfer of the image onto print media passing between the blanket 82 of the ITM drum 80 and an impression drum 86. In operation, the PIP 74, ITM drum 80 and the impression drum are to rotate in the direction of the arrows shown. As an example of the present disclosure, the printing engine 70 can also include a print termination controller 88 to receive a print termination signal at an input 90, and deliver a control signal at an output 92 for controlled ongoing operation of subsystems and their associated print engine consumables prior to termination.
The state of operation of the printing engine 70 in FIG. 4 is such that yellow ink has already been transferred from BID unit 72A to the blanket 82 of the ITM drum 80, magenta ink is in the process of being transferred from the BID unit 72B to the PIP drum 74 and onward onto the blanket 82 of the ITM drum 80, while cyan ink remains wholly within the BID unit 72C without any transfer to the PIP drum 74 having yet occurred.
During normal operation, and in particular with reference to BID unit 72B, magenta ink is transferred to the PIP drum 74 through the application of BID control voltages, a BID engagement mechanism and the charging of the printing imaging plate drum 74. Transfer of the magenta ink from the surface of the PIP drum 74 to the blanket 82 of the ITM drum 80 occurs under the control of a blanket voltage and mechanical engagement, whereas transfer of the yellow ink from the blanket 82 of the ITM drum 80 to the print media (not shown) occurs under the control of the heating unit 84 and the application of pressure by way of the impression drum 86.
A node reset leading to a "break immediately" termination procedure without any ongoing control of subsystems would lead to termination of the printing process with the ink in situ as noted above and so with yellow and magenta ink remaining on the blanket 82 of the ITM drum 80, and magenta ink remaining on the PIP drum 74. Cyan would remain on the Developer Roller of the BID unit 72C. During the reset procedure, which can take between 3-7 minutes, the ink remaining on the PIP drum 74 and the blanket 82 of the ITM drum 80 fuses which can permanently damage both the PIP and the blanket, leading to print defects a decrease in print quality and also the need for replacement of the consumables and re-calibration of the printing process.
Examples of the present disclosure allow for the ongoing control and use of unaffected nodes so as to provide for an abnormal termination sequence that results in less damage to components of the print apparatus such as subsystems and consumables/supplies. Non-affected nodes are thereby permitted to continue to participate in the termination sequence, so as to avoid sudden deactivation and resultant damage. As examples, the ongoing operation at the non-effected nodes can be to allow for activation/deactivation of subsystems to allow for the transfer ink, to clean consumables/supplies of residual ink such as background ink, and to render the print apparatus and consumables ready to enable rapid restarting of subsequent print sessions. With reference to the example illustrated by the flow diagram of FIG. 2, a reset that is identified to have been initiated by the BID Control Unit could allow operation of the PIP drum 74, ITM drum 80 and impression drum 84 to continue and to thereby allow ongoing transfer of ink from the PIP drum 74 to the blanket 82 of the ITM drum 80, and onward from the blanket 82 to the media. This allows for removal of ink from the PIP drum 74 and the blanket 82 of the ITM drum 80, there is then no ink left on those consumables to fuse and cause damage. The blanket 82 can require handling after the abnormal termination sequence has ended, and in some cases, actions can successfully recover blanket functionality. In other scenarios this cannot be achieved successfully and this can determine whether the blanket is to be replaced or not. There is therefore less impact on print quality and the consumables are then ready for use once the reset has been resolved allowing for less frequent replacement. The BID may however then be due for replacement.
With reference to the example of the disclosure illustrated by FIG. 3, the identification of a PCN reset could initiate a control sequence allowing for drying of the BID unit 72C for the cleaning of cyan ink therefrom, and the ongoing transfer of magenta ink from the PIP drum 74 to the blanket 82 of the ITM 80, to thereby effectively allow for cleaning of the PIP drum 74. While, in this example, ink remains on the blanket 82 of the ITM drum 80, resulting in damage during the reset procedure and possible replacement of the blanket 82, controlled cleaning of the BID unit 72C, and the PIP drum 74 can be achieved prior to termination thereby preventing damage to those consumables. The blanket 82 can require handling after the abnormal termination sequence has ended, and in some cases, actions can successfully recover blanket functionality. In other scenarios this cannot be achieved successfully and this can determine whether the blanket is to be replaced or not.
FIG. 5 is a schematic illustration of an example of the print termination controller 88 of FIG. 4. The print termination controller 88 can achieve the controlled operation of print apparatus, through identification of the node from which a node reset originates, for ongoing operation of non-affected nodes so as to prevent damage during termination to component parts controlled by way of such nodes. The print controller 88 can have an input 90 for receiving a termination signal indicating that a printing operation has to terminate. A processor 94 receives and processes the termination signal to identify the nature of the termination instruction received at 90, and can include a node identifier 96 to identify a node from which the termination signal may have originated. A termination control module 98 is connected to the node identifier and produces a print termination control signal at the output 92 to control a selected subsystem responsive to the identified node to prevent damage such as, for example allowing for removal of ink from a consumable.
The print termination controller 88 can control a selected plurality of subsystems, with the selection determined by reference to the node identified as the source of the node reset.
In addition to the potential for damage to components of the printing apparatus, the reduction in print quality with greater likelihood of print defects, and reduced productivity and increased inconvenience and cost for the user, abnormal print terminations can also result in an unreliable count of completed sheets within a print job.
Terminations, and in particular abnormal terminations, can also have an effect of the manner and accuracy in which the passage of print media through the printing apparatus is monitored.
The sheet counting that occurs during a print job relies on a signal handshake between a sheet supply such as a sheet feeding unit, and an end collection point for the printed sheets, such as a stacking unit. When a sheet exits the feeder unit, a 'sent' signal is triggered and when the sheet is delivered to the stacking unit a 'receive' signal is created. The receive message is paired with the sent message so as to determine delivery of the sheet. This in turn allows for a sheet counter to be incremented, and a display in the user interface changes to reflect this. This signal-pairing and sheet counting is under the control of a sheet manager function which is part of the PCN of the print apparatus.
Sheets are considered printed once the 'receive' signal indicates delivery to the stacking unit and the counter incremented. During normal print termination, there will be no mismatch between the sheet counter and the number of sheets delivered to the stacking unit. However, during an abnormal stopping sequence, the PCN can function to clear the paper path before termination is complete. In some scenarios, although a printed sheet is safely delivered by inertia, such a sheet will not be counted if the PCN is either in an erroneous or transient state.
In an example of the disclosure, sheet counting is performed with reference to signals from sheet handling sensors monitoring the passage of a sheet through the apparatus. Examples of such sensors are employed to trigger jam events through the non-arrival of a sheet at the sensor within an expected timing window. The sheet handling sensors can each function independently of the PCN and its sheet manager and serve directly to trigger the Main Control Node.
An example of the disclosure can therefore include monitoring the progress of sheets through the printing apparatus so as to count the sheets passing through monitoring points within the apparatus prior to print termination. The progress can be monitored at the sheet path sensors within the apparatus to confirm, and count, when each sheet has passed each sensor point. In particular, if the PCN is in an erroneous or transient state with its sheet manager inactive, the number of sheets within a particular point of the apparatus, or having passed a particular point, can be assessed by reference to the sheet handling sensors which are independent of the PCN.
Examples of the disclosure can allow for reliable counting of printed and delivered sheets even in situations of abnormal termination. The asynchronous monitoring of sheet-path sensors provides an accurate count of the sheets of a print job actually printed, even during abnormal termination scenarios. Examples of the disclosure can allow for the accurate monitoring of the number of successfully printed sheets and finds particular use in applications such as Variable Data Printing (VDP), and security applications where printer continuity, and avoidance of duplication, is a particular feature.
The disclosure can also provide for a computer-implemented method of print termination in print apparatus including a plurality of nodes and as initiated by a node reset, the method including identifying the node at which the reset occurred, and controlling operation within the print apparatus by way of a selected node, the selected node being different from the identified node and selected responsive to the identification of the identified node, for operation of a component of the print apparatus as part of a termination procedure.
The disclosure can further provide for a non-transitory machine-readable storage medium encoded with instructions executable by a processor, the machine-readable storage medium comprising instructions to identify a node within print apparatus that has triggered a print termination, instructions to control operation within the print apparatus by way of a selected node, the selection being responsive to the identification of the identified node, for operation of a component of the print apparatus as part of a termination procedure.
Although implementations of print termination methods and apparatus have been described in language specific to structural features, components, computer related media and/or methods, it should be understood that the disclosure is not limited to the specific features or methods described. Rather, specific features and methods are disclosed as examples of implementations of the printing methods and apparatus of the disclosure. The computer usable program code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus or device to produce a machine, such that the computer usable program code, when executed via, for example, such data processing apparatus, can implement the functions or acts as specified in the present disclosure. The storage medium of the disclosure can comprise any appropriate medium for temporary, permanent storage, whether removable or non-and including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), Compact Discs (CDs), Digital Versatile Discs (DVDs), etc.
While various examples have been illustrated in the accompanying drawings and description, it should be understood that the disclosure is not limited to the examples disclosed, but is capable of numerous modifications without departing from the scope of the disclosure as set out in the following claims.