Method for managing ink quality of an inkjet printer versus temperature

Abstract

A method for managing the quality of an ink of an inkjet printer versus temperature resorting to the management of the viscosity of the ink versus temperature, the ink comprising a solvent or a mixture of solvents and the solvent or mixture of solvents representing at least 50% by mass of the total mass of the ink, wherein the viscosity of the ink at a temperature T is calculated from the following parameters: the viscosity of the ink at a single reference temperature T.sub.ref; the parameters K or Ln(K), and E/R of equation (1) giving the viscosity of the solvent or of the mixture of solvents: Ln (viscosity of the solvent)=Ln(K)E/RT (1) wherein E is the Arrhenius activation energy given in J/mol and R is the ideal gas constant.

Claims

1. A method for managing quality of an ink of an inkjet printer versus temperature resorting to management of a viscosity of the ink versus temperature, said ink comprising a solvent or a mixture of solvents, and said solvent or mixture of solvents representing at least 50% by mass of the total mass of the ink, the method comprising: during operation of the printer, measuring the viscosity and temperature T of the ink of the inkjet printer; calculating a desired viscosity of the ink at the measured temperature T; comparing the measured viscosity of the ink at the measured temperature T with the calculated desired viscosity of the ink at the measured temperature T; and when the measured viscosity of the ink is greater than the calculated desired viscosity of the ink, adding solvent or a mixture of solvents into the ink so that the measured viscosity of the ink is equal to the calculated desired viscosity of the ink, and when the measured viscosity of the ink is less than the calculated desired viscosity of the ink, waiting until the solvent or the mixture of solvents evaporates so that the measured viscosity of the ink is equal to the calculated desired viscosity of the ink, wherein the desired viscosity of the ink at the measured temperature T is calculated from the following parameters: the viscosity of the ink at a single reference temperature Tref; the parameters K or Ln(K), and E/R of the following equation giving the viscosity of the solvent or of the mixture of solvents: Ln(viscosity of the solvent) =Ln(K)E/RT, and wherein E is the Arrhenius activation energy given in J/mol, and R is the ideal gas constant.

2. The method according to claim 1, wherein the calculated desired viscosity of the ink is further calculated by using a correction factor k.

3. The method according to claim 1, wherein the ink further comprises at least one coloring material.

4. The method according to claim 1, wherein the ink comprises from 50% to 95% by mass of the solvent or of the mixture of solvents based on the total mass of the ink.

5. The method according to claim 1, wherein the viscosity of the ink at the reference temperature Tref is obtained by a measurement carried out in a laboratory.

6. The method according to claim 1, wherein the reference temperature Tref is 20 C.

7. The method according to claim 1, wherein the equation giving the viscosity of the solvent or of the mixture of solvents: Ln (viscosity of the solvent)=Ln(K)E/RT is determined by measuring the viscosity of the solvent or of the mixture of solvents at several temperatures located in the range of operating temperatures of the printer.

8. The method according to claim 1, wherein the viscosity of the ink at the temperature T is calculated by multiplying the viscosity of the ink at the reference temperature Tref by the ratio of the viscosity of the solvent or of the mixture of solvents at temperature T to the viscosity of the solvent or of the mixture of solvents at the reference temperature Tref.

9. The method according to claim 1, wherein the viscosity of each of the inks used in the printer at the reference temperature Tref, and the parameters K or Ln(K), and E/R of the equation giving the viscosity of the solvent or of the mixture of solvents of each of said inks are stored in the machine memory of the printer, and the method further comprises establishing a curve of variation of the viscosity of the ink in the range of operating temperatures of the printer.

10. The method according to claim 2, wherein the correction factor k has a value between 5.10.sup.3 and 10.sup.2.

11. The method according to claim 2, wherein the correction factor k is determined by: measuring the viscosity of each ink of a set of inks used in a printer at at least two temperatures, including the reference temperature T.sub.ref, selected in the range of operating temperatures of the printer; calculating the viscosity of each of the inks of the set of inks at said at least two temperatures, selected in the range of operating temperatures of the printer; for each of the inks of the set of inks, determining a correction factor ki, the correction factor ki having a value such that multiplying the calculated viscosity of the ink by (1ki) renders the measured viscosity; averaging all the determined factors ki for all the temperatures and all the inks of the set of inks, the factor k being the average.

12. The method according to claim 2, wherein the correction factor k is stored in the machine memory of the printer.

13. The method according to claim 2, wherein the viscosity of the ink at temperature T is calculated by multiplying the viscosity of the ink at the reference temperature Tref by the ratio of the viscosity of the solvent or of the mixture of solvents at temperature T to the viscosity of the solvent or of the mixture of solvents at the reference temperature Tref and further by (1k(TTref)), wherein k is the correction factor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph which gives the viscosity (in cPs) versus temperature ( C.) of 10 solvents or mixtures of solvents presently used in inks for inkjet printers, i.e. water, ethanol (EtOH), methyl ethyl ketone (MEK), MEK/EtOH/PMA (methoxypropanol acetate)/methanol (MeOH) mixture (proportions: 68/26.6/1/4.4), methyl isopropyl ketone (MIPK), MEK/EtOH mixture (28/72), MEK/1,2-propanediol/water mixture, EtOH/water mixture (1/1), MEK/PMA (methoxypropanol acetate) mixture (89/11), EtOH/1,2-propanediol mixture (88/11).

(2) The given proportions are proportions by mass.

(3) FIG. 2 is a graph which gives the viscosity at temperature T/viscosity at 20 C. ratio versus temperature T (in C.) of the 10 same solvents or mixtures of solvents as those of FIG. 1.

(4) FIG. 3 is a graph which gives the Ln (viscosity) versus 1/T (in K) of the 10 same solvents or mixtures of solvents like those of FIG. 1.

(5) FIG. 4 is a graph which gives the Ln (viscosity at T/viscosity at 20 C.) versus 1/T (in K) of the 10 same solvents or mixtures of solvents like those of FIG. 1.

(6) FIG. 5 is a graph which gives the reduced viscosity (V.sub.reduced) or relative viscosity which is equal, at a given temperature, to the ratio of the viscosity of the ink to the viscosity of the solvent or of the mixture of solvents of this ink (V.sub.reduced=V.sub.ink/V.sub.solvent) versus temperature ( C.), for 29 inks presently used in inkjet printers designated as 5312, 5506, FT265, 5311, 2550, 5153, 5151, 7540, FT128, 5135, 2323, 2702, 5532, 5137, 7703, FT184, 5144M, 2328, 5139, 9155, FT210, 2151, 2160, 5117, FT207, FT248, 2157, 2538 and 2588 inks.

(7) FIG. 6 is a graph which gives the ratio of the relative viscosity of the ink over the relative viscosity at 20 C. versus temperature (in C.) for 4 inks presently used in inkjet printers, so-called gentle slope (or low slope or soft slope) inks.

(8) These inks are the inks designated as 5137, 5139, 5117, and 2160 inks.

(9) FIG. 7 is a graph which gives the ratio of the relative viscosity of the ink over the relative viscosity at 20 C. versus temperature (in C.) for 3 inks presently used in inkjet printers so-called steep slope inks.

(10) These inks are the inks designated as 5153, 2538, and 2588 inks.

(11) FIG. 8 is a graph which gives the ratio of the relative viscosity of the ink over the relative viscosity at 20 C. versus temperature (in C.) for 10 inks presently used in inkjet printers, so-called medium slope inks.

(12) These inks are the inks designated as 5506, 7540, 7703, 9155, FT265, FT248, 5144 M, 2157, 2550, and 5532 inks.

(13) FIG. 9 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid.) and the calculated viscosity according to the invention (points .box-tangle-solidup.) versus temperature (in C.) for an ink, designated as 5137 ink, with a gentle slope, the essential solvent of which is MEK.

(14) FIG. 10 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid.) and the calculated viscosity according to the invention (points .box-tangle-solidup.) versus temperature (in C.) for an ink, designated as 2538 ink, with a steep slope, the solvent of which is MEK.

(15) FIG. 11 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature (in C.) for an ink, designated as 7703 ink, the solvent of which is water.

(16) FIG. 12 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature (in C.) for an ink, designated as 7540 ink, the solvent of which is ethanol.

(17) FIG. 13 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature (in C.) for an ink, designated as FT248 ink, the solvent of which is ethanol.

(18) FIG. 14 is a graph which gives the viscosity (in cPs) versus temperature (in C.) of 29 different inks presently used in inkjet printers, designated as 5312, 5506, FT265, 5311, 2550, 5153, 5151, 7540, FT128, 5135, 2323, 2702, 5532, 5137, 7703, FT184, 5144M, 2328, 5139, 9155, FT210, 2151, 2160, 5117, FT207, FT248, 2157, 2538 and 2588 inks.

(19) FIG. 15 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for an ink, designated as 5139 ink, the solvent of which is the MEK/methoxypropanol acetate mixture mentioned above.

(20) FIG. 16 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for an ink, designated as 5311 ink, the solvent of which is the ethanol/1,2-propanediol mixture mentioned above.

(21) FIG. 17 is a graph which gives the measured experimental viscosity (in cPs), (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for an ink, designated as FT128 ink, the solvent of which is the ethanol/water mixture mentioned above.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENT

(22) When the curves which give the viscosity versus temperature of the base solvents of the inks for inkjet printers such as water, alcohol (ethanol), and methyl ethyl ketone (MEK), which may be found in the literature, are examined, it is seen that the variations of the viscosity of the solvents versus temperature, are of the same order as those of the corresponding inks in relative values.

(23) All the curves which give the viscosity versus temperature of the inks which are required for proper operation of the present inkjet printers were therefore collected.

(24) More exactly, these are the raw data relating to viscosity versus temperature of 29 different inks designated as 5312, 5506, FT265, 5311, 2550, 5153, 5151, 7540, FT128, 5135, 2323, 2702, 5532, 5137, 7703, FT184, 5144M, 2328, 5139, 9155, FT210, 2151, 2160, 5117, FT207, FT248, 2157, 2538 and 2588 inks, which have been gathered on a same graph, FIG. 14.

(25) On this graph it may be seen that the viscosities of the inks vary between 0 and 50 C. by a factor of about 2 to 4, and from 2 to more than 6 for certain inks.

(26) As these inks do not have all the same viscosity at the reference temperature of 20 C., they may be compared more easily by dividing the viscosity at a temperature T by the viscosity at 20 C. for each ink.

(27) The thereby obtained values were gathered on a same graph, which is not either reproduced here because of its complexity.

(28) The curves which give the viscosity, versus temperature, of the 10 solvents, or mixtures of solvents of these inks are given in FIG. 1.

(29) These curves were extracted from the literature or else, notably for the mixtures of solvents, established from viscosity measurements conducted in the laboratory.

(30) These solvents are water, ethanol (EtOH), methyl ethyl ketone (MEK), MEK/EtOH/methoxypropanol acetate or PMA/Methanol (MeOH) mixture (68/26.6/1/4.4), the MEK/1,2-propanediol/water mixture, the EtOH/water mixture (1/1), the MEK/methoxypropanol acetate mixture (89/11), the methyl isopropyl ketone (MiPK), the EtOH/1,2 propanediol mixture (88/11) and the MEK/EtOH mixture (28/72).

(31) A particular way for comparing these curves is to divide them by their viscosity at 20 C. In other words, the curves which give the viscosity at temperature T/viscosity at 20 C. ratio versus temperature T (in C.) of the aforementioned 10 solvents or mixtures of solvents are plotted (FIG. 2).

(32) In order to be able to calculate the viscosity of the solvents at all the intermediate temperatures, it is possible to smooth these data by an equation of the Arrhenius type which is perfectly suitable over a reduced range of temperatures, such as the relevant range from 0 C. to 50 C.

(33) The viscosity curve of each solvent which gives the viscosity versus temperature may therefore be described by an equation of the type =K.Math.e.sup.E/RT (1)

(34) Either as a logarithm: Ln ()=Ln(K)E/RT (2), wherein q is the dynamic viscosity (in cPs) and T is the temperature (in K).

(35) It is therefore noted that only two parameters i.e. Ln(K) and E/R are involved in this equation.

(36) For each of these curves, the ordinate at the origin gives Ln(K) and the slope gives E/R.

(37) FIG. 3 is a graph which gives the Ln(viscosity ) versus 1/T (in K) for the aforementioned 10 solvents or mixture of solvents used presently in inks for inkjet printers.

(38) In the same way, the ratio of the viscosity of the solvent to the reference viscosity (for example at 20 C.) gives as logarithms: Ln (viscosity at T/viscosity at 20 C.)=Ln (viscosity)Ln (viscosity at 20 C.)=Ln(K)E/RTLn (viscosity at 20 C.).

(39) FIG. 4 is a graph which gives the Ln (viscosity at T/viscosity at 20 C.) versus 1/T (in K) of the 10 solvents or mixtures of solvents mentioned above presently used in inks for inkjet printers.

(40) If the reduced viscosity (V.sub.reduced), or relative viscosity (which is equal, at a given temperature, to the ratio of the viscosity of the ink to the viscosity of the solvent or of the mixture of solvents of this ink i.e. V.sub.reduced=V.sub.ink/V.sub.solvent) is calculated at each of the temperatures, for the inks mentioned above presently used in inkjet printers, the relative viscosity curves of these inks are then obtained which are plotted in FIG. 5.

(41) It may be seen that these relative, reduced viscosity curves of the inks are much more linear when they are compared with the viscosity curves for which the curvatures are very large (FIG. 14).

(42) It may also be ascertained that the slopes of the curves of FIG. 5 are very similar.

(43) If these relative, reduced viscosities are reduced to a common value at 20 C. by dividing them by the viscosity at 20 C., a graph is then obtained, which gives for each ink mentioned above the relative viscosity/relative viscosity at 20 C. ratio versus temperature (in C.).

(44) This graph is not reproduced here because of its complexity.

(45) It is seen on this graph that the essential portion of the variation of the viscosity of the ink stems from that of the solvent.

(46) It then becomes clear that by calculating the relative viscosity, the contribution of the solvent to the effect of temperature is suppressed.

(47) In other words, if the relative viscosity of an ink is measured versus temperature, the obtained curve is quasi flat, which shows that the variation of the viscosity with temperature is essentially due to the solvent and much less to the other ingredients of the ink such as the coloring agents and the pigments.

(48) Indeed, the curves of this graph are close to straight lines with slopes generally comprised between 0.003 and 0.006 C..sup.1.

(49) For all these inks, the variation of the relative viscosity is not more than 20% between 0 and 50 C., to be compared with the ratios mentioned earlier which were from 2 to more than 6.

(50) If the bundle of curves, which gives for each ink the relative viscosity/relative viscosity at 20 C. ratio versus temperature (in C.), is now examined with more attention, it may be seen that there are: a few inks which show relatively gentle (low, soft) slopes of the ratio of viscosities, of less than 0.004 C..sup.1 (FIG. 6). a few other inks with the steepest slopes, greater than 0.006 C..sup.1 (FIG. 7). The greater number of inks with intermediate, medium, slopes, between 0.0045 and 0.006 C..sup.1 (FIG. 8).

(51) From these observations, it is possible to estimate relatively well the viscosity versus temperature curves by only knowing the viscosity at a single temperature and that of the solvent or of the mixture of solvents (it may even be sufficient to only know the viscosity of the majority solvent of the mixture of solvents) at all the desired temperatures, i.e. generally in the range of operating temperatures of the inkjet printer, for example from 0 C. to 50 C.

(52) In other words, according to the invention, the viscosity curve of an ink, for example from 0 to 50 C. may be determined by only 3 parameters and optionally 4 parameters, instead of a complete curve, i.e.: the viscosity of the ink at 20 C.; the viscosity parameters of the solvent: Ln(K) and E/R.

(53) If greater accuracy is desired, then a fourth parameter is used: the slope correction factor k.

(54) In a simplified embodiment wherein the viscosity of the ink may be approximated to within 20%, only 3 factors, parameters, are required and sufficient. For greater accuracy, i.e. 10% or better 5%, a 4.sup.th factor, i.e. the correction factor k, is required.

(55) The calculation of the viscosity of an ink at a temperature T may be expressed in generic terms as follows: Let .sub.eT be the viscosity of the ink at temperature T; .sub.eTref be the viscosity of the ink at the reference temperature T.sub.ref (for example 20 C.); .sub.sT be the viscosity of the solvent at temperature T; .sub.sTref be the viscosity of the solvent at the reference temperature T.sub.ref (for example 20 C.); r.sub.eT be the relative viscosity of the ink at temperature T;
r.sub.eT=.sub.eT/.sub.sT
and in the same way r.sub.eTref is the relative restricted viscosity of the ink at the reference temperature T.sub.ref (for example 20 C.). The ratio .sub.eT/.sub.eTref is a function of the temperature f(T) It was shown that:
r.sub.eT/r.sub.eTref=1k(TTref)
The ratio
r.sub.eT/r.sub.eTref=.sub.eT/.sub.sT.sub.sTref/.sub.eTref=f(T).sub.sTref/.sub.sT
Whence: In a first approximation with r.sub.eT/r.sub.eTref=1
.sub.eT=.sub.eTref.sub.sT/.sub.sTref
and by adding the correction on
r.sub.eT/r.sub.eTref=1k(TTref)
.sub.eT=.sub.eTref.sub.sT/.sub.sTref(1k(TTref))
with
.sub.sT=K.Math.e.sup.E/RT
.sub.sTref=K.Math.e.sup.E/RTref

(56) It is therefore possible to calculate the viscosity curve of an ink at a temperature T only from: 1. the viscosity of the ink at a single temperature (T.sub.ref). 2. the ratio of the viscosity of the solvent at the same temperature T, to the viscosity of the solvent at the reference temperature T.sub.ref. This calculation is carried out with an approximation of about 20%. For a better approximation, it is possible to add the correction factor k.

EXAMPLES

(57) In the following examples, the method according to the invention is applied to the calculation of the viscosity of various inks for inkjet printers.

(58) In order to calculate the viscosity of an ink at a given temperature T, the method is simple: 1. Multiply the viscosity of the ink at the reference temperature (20 C. for example), by the ratio of the viscosity of the solvent at the same temperature T to the viscosity of the solvent at the reference temperature (20 C.). 2. Optionally correct the result by multiplying it by (1k(TT.sub.ref)), wherein k is a correction factor such as 0.0047, rounded to 0.005.

(59) The value of the correction factor k, for example k=0.0047 (rounded to 0.005) is obtained as discussed above, by averaging the values of the correction factors ki to be applied to the viscosity calculated at a given temperature in order to obtain the real viscosity actually measured at this temperature, on a given ink set representative of the inks.

(60) In the following examples, the calculation method according to the invention as discussed above is applied to various inks by assuming a correction factor k (average correction factor) of 0.0047. 0.0047 is an average value of the correction factor for all the tested inks and may be rounded to 0.005.

Example 1

(61) In this example, the calculation method according to the invention, as discussed above, is applied to an ink with a gentle slope designated as 5137, the solvent of which is MEK.

(62) FIG. 9 gives the measured experimental viscosity (in cPs) (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature ( C.) for this ink.

Example 2

(63) In this example, the calculation method according to the invention, as discussed above, is applied to an ink with a steep slope designated as 2538, for which the solvent is MEK.

(64) FIG. 10 gives the measured experimental viscosity (in cPs) (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature ( C.) for this ink.

Example 3

(65) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as 7703, for which the solvent is water.

(66) FIG. 11 gives the measured experimental viscosity (in cPs) (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature ( C.) for this ink.

Example 4

(67) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as 7540, for which the solvent is alcohol.

(68) FIG. 12 gives the measured experimental viscosity (in cPs) (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature ( C.) for this ink.

Example 5

(69) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as FT248, for which the solvent is alcohol.

(70) FIG. 13 gives the measured experimental viscosity (in cPs) (points .diamond-solid.) and the viscosity calculated according to the invention (points .box-tangle-solidup.) versus temperature ( C.) for this ink.

Example 6

(71) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as 5139, for which the solvent is the MEK/methoxypropanol acetate mixture mentioned above.

(72) FIG. 15 gives the measured experimental viscosity (in cPs) (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for this ink.

Example 7

(73) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as 5311, for which the solvent is the alcohol/1,2-propanediol mixture mentioned above.

(74) FIG. 16 gives the measured experimental viscosity (in cPs) (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for this ink.

Example 8

(75) In this example, the calculation method according to the invention, as discussed above, is applied to an ink designated as FT128, for which the solvent is the alcohol/water mixture mentioned above.

(76) FIG. 17 gives the measured experimental viscosity (in cPs) (points .diamond-solid., curve in thin solid line), the viscosity calculated according to the invention (curve in thick solid line), and the viscosity calculated according to the invention and further corrected by applying a correction factor (curve in dotted lines) versus temperature (in C.) for this ink.

(77) Examples 1 to 8 provided above show that the method according to the invention gives excellent results since it is ascertained that the measured experimental viscosity curves and the curves giving the viscosity calculated according to the invention, and a fortiori the curves giving the viscosity calculated and further corrected according to the invention quasi coincide or are very close to each other.

(78) These examples further show that excellent results are obtained with the method according to the invention regardless of the solvent of the ink whether this is water, MEK or alcohol or mixtures of solvents, and regardless of the ink and of the ingredients thereof other than the solvent.