JP2003182041A - Method for measuring india ink amount for printer and controller for measuring the ink amount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure an India ink amount by eliminating an influence of absorbing a reference light when an India ink thin film containing carbon and on an ink supply roll surface obtained by emulsifying a dampening water is measured in offset printing. <P>SOLUTION: A method for measuring the India ink amount for the printer comprises the steps of emitting an infrared ray to the India ink film 50 obtained by emulsifying the dampening water on an ink supply roller 20 surface, and measuring the India ink amount on the ink supply roll 20 surface of the printer, and obtaining the value P obtained based on reflecting ray amount obtained by irradiating the India ink film of the ink supply roll 20 surface of the printer with the infrared rays L, M and N, wherein L is the infrared ray in an infrared ray range showing an absorbance peak to the ink, N is the infrared ray showing a small absorbance to the water or the ink in a longer wavelength side than the ray L, and M is the infrared ray showing a small absorbance to the water or the ink, as the India ink amount. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the ink supply roll surface of a printing press by measuring the black ink thin film on the ink supply roll surface in which carbon is contained in the ink and the fountain solution is emulsified in offset printing. The present invention relates to a black ink amount measuring method for a printing machine, which measures the black ink amount.

[0002]

2. Description of the Related Art For example, a conventional method for measuring the ink supply amount of an offset printing machine using fountain solution is to irradiate an ink film as an object to be measured with light and absorb the light absorbed by the ink film. And the reflected light amount obtained by irradiating the ink film with a reference light of a wavelength (frequency) that is not absorbed by either the ink body or water in the ink film, and the value is used as the ink amount of the ink film. There is a method of calculation, for example, the method disclosed in Japanese Patent Laid-Open No. 6-120004).

[0003]

In the conventional ink measuring method (method of calculating by the ratio or difference between the reference light and the ink measuring light), in the black ink containing carbon, the reference light has an influence due to absorption. Therefore, there is a problem that black ink alone cannot be measured among the offset printing inks.

The present invention has been made in view of the above problems, and provides a method for measuring the amount of black ink containing carbon and further emulsifying dampening water by utilizing the absorption of infrared light. is there.

[0005]

In order to achieve the above object, the present invention irradiates an ink ink film emulsified in a fountain solution on the surface of an ink supply roll with infrared light and prints based on the amount of reflected light. In a black ink amount measuring method for a printing press, which measures the black ink amount on the surface of a machine ink supply roll, the infrared light in the infrared light wavelength region showing an absorbance peak for ink is L, and the wavelength is shorter than the infrared light L. Infrared light that is on the side and has a low absorbance for water or ink is N, and infrared light that is on a longer wavelength side than the infrared light L and has a low absorbance for water or ink is M. , The reflected light amounts L1, M1, and N1 obtained by irradiating the black ink coating on the surface of the ink supply roll of the printing press with the infrared rays L, M, and N, and the following formula P = (M1-L1) / (M1- N1) and the value P obtained based on A printer black ink amount measurement method, characterized by determining a black ink amount Lumpur surface. Further, the black ink amount measuring means using the black ink amount measuring method according to claim 1 and means for adjusting and controlling the black ink supply amount of the printing machine based on the result. It is a control device. Further, an offset printing machine comprising the black ink amount measurement control device according to claim 2.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The method for measuring the amount of black ink in a printing machine of the present invention will be described in detail below. FIG. 1 is a side view of a dampening water and ink supply device in an offset printing machine,
Reference numeral 1 is a plate cylinder having an offset printing plate 1a, 2 is a blanket cylinder (blanket cylinder for transfer) having a blanket 2a, 3 is an impression cylinder, and the plate cylinder 1 has a dampening water supply roll group 10 and ink. A supply roll group 20 is provided.

The dampening water supply roll group 10 is, for example, a water tank 11 for storing dampening water 12, a fountain roll 13 immersed in the dampening water 12, a dampening water duct (conveying) roll 15, and a roll 13. A dampening water roll 14 that is alternately attached to and detached from a dampening water roll 15 and a dampening water roll that attaches dampening water of a dampening water duct roll 15 to the printing plate surface mounted on the peripheral surface of the plate cylinder 1. By controlling the contact time of the dampening water calling roll 14 with the duct roll 15, the amount of the dampening water 12 supplied to the dampening water depositing roll 16 and the printing plate 1a can be adjusted. There is.
There is also a method of controlling the amount of dampening water by controlling the rotation amount of the roll 13 while the roll 14 is in contact with the rolls 13 and 15.

The ink supply roll group 20 includes, for example, an ink fountain 21 that stores ink 22, and an ink fountain roll 23 that comes into contact with and rotates with the ink 22 to take out the ink.
, An ink key K capable of opening and closing the gap k between the ink fountain 21 and the fountain roll 23, an ink duct roll 25, an ink transfer (swing) roll 24 which is alternately attached to and detached from the rolls 23 and 25, and an ink duct. A duct roll 26 that receives the ink conveyed from the roll 25 via an intermediate roll, and duct rolls 26a and 26b that convey the ink from the duct roll 26 toward the plate cylinder,
26c, 26d and each of the inking rolls 28a, 28b, 28c, 2 for receiving ink from the duct rolls 26a, 26d and adhering the ink to the surface of the printing plate 1a of the plate cylinder 1.
8d and an intermediate roll 27 provided between the inking rolls 28b and 28c, controlling the gap k (opening) by the ink key K and / or contacting the ink transfer roll 24 with the ink duct roll 25. The amount of ink supply can be adjusted by controlling the rotation time. It should be noted that the present invention is not limited to the configuration and arrangement of the rolls.

The printing plate 1 to which the dampening water is supplied (attached, applied) by the dampening water application roll 16 of the dampening water supply roll group 10.
The a-side is formed by the rotation of the plate cylinder 1 in the direction of the arrow, and the inking rolls 28a, 28b, 28c of the ink supply roll group 20,
When the ink reaches 28d, the ink adheres to the lipophilic image area of the printing plate 1a, and subsequently the ink of the image area transfers from the surface of the printing plate 1a to the surface of the blanket cylinder 2,
Then, the ink transferred to the surface of the blanket cylinder 2 is transferred and printed on the printing paper 40 introduced between the blanket cylinder 2 and the impression cylinder 3.

The dampening water supplied from the dampening water supply roll group 10 to the printing plate 1a is supplied to the inking rolls 28a, 28b, 28c, 28d of the ink supply roll group 20 and the ink supply rolls adjacent to each of the forming rolls. When mixed with the ink adhering to the roll group, emulsification of the ink occurs on the roll surface, and the appropriate emulsified state of this emulsification phenomenon is obtained when the ink is adhered to the printing plate 1a surface by the inking roll. It also has the role of preventing ink from adhering to the hydrophilic non-image areas.

In the present invention, the ink supply roll group 2
0, metal ink duct rolls 26, 26a, 26b, 26c, 26d, 27 that are close to the surface of rubber inking rolls 28a, 28b, 28c, 28d having appropriate hardness. Irradiation of infrared light to the black ink film emulsified in the dampening water generated by mixing the black ink film adhering to the surface of the roll, and the amount of light reflected from the black ink film on the roll surface is measured. The amount of transmitted light may be measured by making the roll transparent.

An embodiment of the method for measuring the amount of black ink of a printing machine according to the present invention will be described in detail below with reference to the side view of the fountain solution and the ink supply device of FIG. 1 and the block diagram of FIG. 1, the metal rolls 26, 26a, 26b, 26 shown in FIG.
In order to irradiate infrared rays on the roll surface of one of the metal roll 26d and the rubber inking roll 28d, which is located on the downstream side of the printing plate cylinder 1 in the rotational direction, of c, 26d, and 27, for example. Infrared light source section 31 (light emitting section)
And a photo sensor 32 (light receiving portion) that receives infrared reflected light from the roll surface and detects the amount of light.

As the infrared light emitted from the infrared light source section 31, for example, as shown in FIG. 2, the infrared light W in the infrared light wavelength region showing the absorption peak for water and the absorption peak for the ink. Light L in the infrared light wavelength range
And infrared light N ', which is on a shorter wavelength side than the infrared light W and has a low absorbance for water or ink, and between the infrared light W and L, and to water and ink. Infrared light N, which has a low absorbance, and infrared light M, which has a longer wavelength than the infrared light L and has a low absorbance for water or ink, have five wavelengths. used.

As the infrared light W (known) in the infrared wavelength region showing an absorption peak with respect to water (pure water), infrared light having a wavelength of about 3000 nm is used, and ink (mainly ink) is used. Infrared light having a wavelength of about 3500 nm is used as the infrared light L (known) in the infrared wavelength range that exhibits an absorbance peak for the composition (ink vehicle component having a —CH group).

Further, the infrared light W (around 3000 nm) and the infrared light L (35) exhibiting low absorbance for water and ink.
A wavelength of about 3300 nm is used as the wavelength of the infrared light N between (about 00 nm) and the infrared light L (35
Infrared light M, which is on the longer wavelength side (near 00 nm) and shows less absorbance for water and ink, is, for example, 3
Infrared light with a wavelength of 800 nm is used.

Further, as the infrared light N ', which is on the shorter wavelength side than the infrared light W (near 3000 nm) and has a low absorbance for water and ink, for example, infrared light having a wavelength of about 2500 nm is used. To be done.

Then, as the method of the present invention, as shown in FIG. 2, the infrared light sources 31 emit infrared light N, L, and M, respectively.
Of the metallic ink duct roll 26d (for example, a swing roller that swings in the direction of the rotation axis or a fixed-position rotary roll that does not swing) on the downstream side in the rotation direction of the rotating printing plate cylinder 1 during the printing operation. Surface or rubber inking roll 28
The black ink film 50 attached to the surface of d is irradiated, and the infrared reflected light is received by the photosensor 32, and the reflected light amounts N1, L1 and M1 are measured and detected.

Then, P = (M1−L1) / (M1−N1) the quantity of reflected light of wavelength N: N1 the quantity of reflected light of wavelength L: L1 the quantity of reflected light of wavelength M: M1 (Amount of infrared absorption by black ink film) is supplied (attached) to the ink supply roll surface of the printing machine.
It is the ink amount of the black ink film.

As described above, according to the method of the present invention, the black ink coating 50 containing carbon to be measured and having the fountain solution emulsified is irradiated with infrared light B1 on the roll surface of the ink supply roller group. The reflected light B2 is measured, and one wavelength of the wavelength L, which responds greatly to the increase or decrease in the amount of infrared light absorbed by the ink film, and the wavelength M on the long wavelength side, which has little effect on the increase or decrease of the black ink film and water. Then, the reflected light amount of three wavelengths in total, that is, two wavelengths (N) on the short wavelength side (however, the short wavelength side is a longer wavelength side than the wavelength that greatly responds to the increase or decrease of the water absorption amount) is measured.

Then, as in the above formula, the difference between the other two wavelengths L and N is calculated with reference to the absorption of the infrared light M on the long wavelength side by the black ink film, and the difference is taken as a ratio. Then, the obtained value P is calculated as the amount of ink supplied to the ink supply roll surface.

Then, while measuring the black ink film 50 on the roller surface, the infrared light absorption amount P by the black ink film obtained by the measurement is in a state where the printability and the print reproducibility which are obtained in advance are good. The ink is transferred alternately to the ink fountain roll 23 and the ink duct roll 25 of the ink fountain 21 until the infrared light absorption amount PO (black ink reference amount) is reached, and the roll 24 is contact-rotated to rotate both rolls 2.
The contact time for 3, 25 is controlled to control and adjust the supply amount of black ink.

Next, one embodiment of the method of the present invention is shown in FIG.
The following description is based on the flowchart shown in FIG. S1: First, the printing machine is rotated and the opening degree (gap k) is automatically or manually controlled by opening and closing the ink key of the ink fountain 21 to adjust the ink supply amount to the ink supply roll group 20. S2: While adjusting the ink supply amount, the print image state of the printing paper 40 surface which is introduced and printed between the blanket cylinder 2 and the impression cylinder 3 of the printing machine is checked, and proper reproducibility and tone printing are performed. When the image is obtained, the infrared light source 31
And the amount of light reflected from the black ink film 50 on the surface of the ink supply roll to be measured by the photosensor 32 and N1, L1, M
While 1 is measured, the measured data is input to the computer 33 such as a personal computer, and the calculation formula (algorithm) P = (M1−L1) / (is stored in the memory by the central data processing control unit. M1-N1)
Based on the above, the black ink amount P of the ink supply roll surface is calculated, set as the ink amount target value Po and stored in the memory. S3: Subsequently, the amounts of reflected light N1, L1, and M1 from the black ink film 50 on the surface of the ink supply roll are continuously measured (at predetermined intervals). S4: Then, the reflected light amounts N1 and L1 continuously measured
, M1 are input to the computer 33 and are taken into the calculation unit via the central data processing control unit, and the black ink amount P on the ink supply roll surface is calculated at predetermined intervals based on the above calculation formula and continuously calculated. A central data processing control unit of the computer 33 compares and calculates the black ink amount P and the target ink amount value P0. S5: If the black ink amount P = (or .apprxeq.) Ink amount target value P0 as a result of the comparison calculation, the process proceeds to the next S6. On the other hand, if the black ink amount P ≠ the ink amount target value P0, the process proceeds to the next S7. S6: Black ink amount P = (or ≈) If the ink amount target value Po, the computer 33 supplies the ink supply amount control instruction means 34 (instruction means for opening / closing the ink key by an electric motor and the rotational peripheral speed instruction of the fountain roll 23). Means) to maintain the ink key opening (gap k) and the rotational peripheral speed of the fountain roll 23 without changing, and maintain the ink supply amount at that time. In FIG. 1, 35 is an ink key opening instruction signal transmission system, and 36 is a rotational peripheral velocity instruction transmission system of the fountain roll 23. S7, S8: If the black ink amount P ≠ the ink amount target value Po, the ink supply amount is changed. In that case, the black ink amount P
If the ink amount target value P0, the computer 33 sends an instruction signal to the ink key opening control instruction means 34 (electric motor open / close control instruction means) to decrease the ink key opening (gap k). Change control to reduce the ink supply. If the black ink amount P <ink amount target value P0, an instruction signal is transmitted from the computer 33 to the ink key opening control instruction means 34 (instruction means for opening / closing control by an electric motor), and the ink key opening degree ( The gap k) is changed and controlled to increase, and the ink supply amount is increased. S9: When the control is not repeated after the control of maintaining the ink supply amount or the control of decreasing or increasing the ink supply amount, the ink amount measurement of the printing machine is finished or the operation of the printing machine is finished. S10: If the control is repeated after the ink supply amount maintenance control or the ink supply amount decrease or increase control is performed, the process proceeds to S10, and if the ink amount target value is not changed or not reviewed, the process proceeds to S3 and is changed. When reviewing, the process proceeds to S2.

The change in the ink amount on the surface of the ink supply roll calculated by the embodiment of the method of the present invention is shown in FIG. 3, and the change in the ink on the surface of the ink supply roll calculated by the method of the comparative example is shown in FIGS. 4 and 5. Shown in.

<Method of the Present Invention> (Printing Conditions) First, the black ink supply amount was changed in the following procedure. (However, the amount of dampening water supplied is not changed.) A1: The opening K of the ink key of the ink fountain 21 is 2/100.
Decrease (ink-2) A2: Ink key opening K of ink fountain 21 is 5/100
Increase (ink +5) A3: Ink key opening K of ink fountain 21 is 5/100
Decrease (ink-5) A4: Ink key opening K of ink fountain 21 is 2/100
Increase (ink + 2) Next, the dampening water supply amount was changed in the following procedure. (However, the amount of ink supply is not changed) A5: Decrease the rotation amount of the fountain roll 13 by 2/100 (water-2) A6: Increase the rotation amount of the fountain roll 13 by 5/100 (water +5) A7: Fountain roll 13 Decrease the amount of rotation of 5/100 (water-5) A8: increase the amount of rotation of the fountain roll 13 by 2/100 (water +2) (Measurement conditions) Under the transition of the printing conditions of A1 to A8 specified above, The amount of reflected light N2, L2, M2 under the printing conditions of A1 to A8 is measured by irradiating infrared light N, L, M of the following three kinds of wavelengths, and the calculation formula P = (M2-L2) is obtained. The amount of ink P on the surface of the ink supply roll was calculated by calculating / (M2-N2). Amount of reflected light measured by irradiation of infrared light N near 3300 nm: N2 Amount of reflected light measured by irradiation of infrared light L near 3500 nm: L2 Amount of reflected light measured by irradiation of infrared light M near 3800 nm: M2

FIG. 3 shows the transition of the ink amount on the ink supply roll surface of the printing press by the measuring method according to the method of the present invention, which is calculated by P = (M2-L2) / (M2-N2). The change in the amount of ink is shown. In A1, it can be confirmed that the reaction in which the ink supply amount from the ink fountain 21 is slightly reduced is captured as a decrease in the ink amount on the ink supply roll surface. Further, it can be confirmed that the state in which the ink supply amount is greatly increased in A2 and the state in which the ink supply amount is greatly reduced in A3 are recognized as a change in the ink amount on the ink supply roll surface. Next, when the amount of dampening water was changed without changing the amount of ink supplied from the ink fountain 21, it was confirmed that the changes in the amount of ink on the ink supply roll surface were hardly affected from A5 to A8. Therefore, it can be confirmed that the change in the ink amount on the surface of the ink supply roll is correctly captured without being affected by the change in the dampening water supply amount.

<Method of Comparative Example 1> (Printing Conditions) First, the black ink supply amount was changed in the following procedure. (However, do not change the dampening water supply amount.) B1: The ink key opening K of the ink fountain 21 is 2/100.
Reduce (Ink-2) B2: Ink key opening K of ink fountain 21 is 5/100
Increase (ink +5) B3: Ink key opening K of ink fountain 21 is 5/100
Decrease (ink-5) B4: Opening K of ink key of ink fountain 21 is 2/100
Increase (ink + 2) Next, the dampening water supply amount was changed in the following procedure. (However, the amount of ink supply is not changed.) B5: The rotation amount of the fountain roll 13 is reduced by 2/100 (water-2) B6: The rotation amount of the fountain roll 13 is increased by 5/100 (water +5) B7: Fountain roll 13 Decrease the amount of rotation of 5/100 (water-5) B8: increase the amount of rotation of the fountain roll 13 by 2/100 (water +2) (measurement conditions) Under the transition of the printing conditions of B1 to B8 specified above, The amount of reflected light N′2, L2, and M2 under the printing conditions of B1 to B8 is measured and obtained by irradiating infrared light N ′, L, and M of the following three wavelengths, and the calculation formula, P = (M2− The ink supply amount P was calculated by calculating L2) / (M2-N'2). Measured reflected light amount by irradiation of infrared light N'in the vicinity of 2500 nm on the shorter wavelength side than the absorption wavelength of water: N'2 Measured reflected light amount by irradiation of infrared light L in the vicinity of 3500 nm: L2 of infrared light M in the vicinity of 3800 nm Amount of reflected light measured by irradiation: M2

FIG. 4 shows the method of Comparative Example 1 in which the reference light on the short wavelength side is set to a wavelength shorter than that of the present invention, and infrared light N'in the vicinity of 2500 nm, which is a wavelength shorter than the absorption wavelength of water, is irradiated. The change in the amount of ink by the measurement method including the measurement by In B1, it can be confirmed that the reaction in which the ink supply amount from the ink fountain 21 is slightly reduced is recognized as a decrease in the ink amount on the ink supply roll surface. further,
It can be confirmed that in B2, the state in which the ink supply amount from the ink fountain 21 is greatly increased and in B3 is the state in which the ink supply amount is greatly reduced are recognized as a change in the ink amount on the ink supply roll surface. Next, when the dampening water supply amount was changed without changing the ink supply amount from the ink fountain 21, even though the dampening water supply amount was slightly reduced in B5, the ink supply roll surface It can be confirmed that the amount of ink in is increasing. Furthermore, B
6, B7, B8 and whenever the dampening water supply amount is increased or decreased,
It can be confirmed that the amount of ink on the surface of the ink supply roll has increased or decreased, and due to the change in the amount of dampening water supplied, the ink fountain 21
It can be seen that not only the ink supply amount from the ink supply roll but also the dampening water supply amount change, the change in the ink amount on the ink supply roll surface is not preferable.

<Method of Comparative Example 2> (Printing Conditions) First, the black ink supply amount was changed in the following procedure. (However, do not change the dampening water supply amount.) C1: The ink key opening K of the ink fountain 21 is 2/100.
Decrease (ink-2) C2: Ink key opening K of ink fountain 21 is 5/100
Increase (ink +5) C3: Ink key opening K of ink fountain 21 is 5/100
Reduce (ink-5) C4: Ink key opening K of ink fountain 21 is 2/100
Increase (ink + 2) Next, the dampening water supply amount was changed in the following procedure. (However, the ink supply amount is not changed.) C5: The rotation amount of the fountain roll 13 is reduced by 2/100 (water-2) C6: The rotation amount of the fountain roll 13 is increased by 5/100 (water +5) C7: Fountain roll 13 Decrease the amount of rotation of 5/100 (water-5) C8: increase the amount of rotation of the fountain roll 13 by 2/100 (water +2) (measurement conditions) Under the transition of the printing conditions of C1 to C8 specified above, The amount of reflected light N2, L2, and M2 under the printing conditions of C1 to C8 is measured by irradiating infrared light N, L, and M of the following three types of wavelengths, and the calculation formula P = (N2-L2) / The ink supply amount P was calculated by calculating (N2-M2). Measured by irradiation with infrared light N near 3300 nm, which is shorter than the absorption wavelength of water. Reflected light amount: N2 Measured by irradiation with infrared light L near 3500 nm. Reflected light amount: L2, measured by irradiation with infrared light M near 3800 nm. Reflected light amount: M2

FIG. 5 shows the transition of the amount of ink on the surface of the ink supply roll obtained by the method of Comparative Example 2. Ink fountain 21
When the dampening water supply amount was changed without changing the ink supply amount from C., it was confirmed that there was almost no effect on the fluctuation of the ink amount on the ink supply roll surface from C5 to C8. However, in C1, it can be confirmed that, although the ink supply amount from the ink fountain 21 was slightly reduced, it was recognized as an increase in the ink amount on the ink supply roll surface as a reaction. Further, in C2 and C3, the ink supply amount from the ink fountain 21 was greatly increased or decreased, but the ink amount on the ink supply roll surface changed in the opposite direction, and the roll surface generated by the change of the ink supply amount. It can be confirmed that the change in the ink amount of is not correctly captured.

[0030]

As described above, according to the present invention, a black ink thin film containing carbon and having water emulsified can be measured by a method utilizing absorption of infrared light. Therefore, if you have a sensor with a structure that can measure three types of infrared wavelengths in advance, you can measure both black ink containing carbon and ink not containing carbon by switching the measuring method with the same sensor. It is possible to provide a sensor that is extremely versatile. Further, the black ink amount measurement control device of the present invention can accurately perform the black ink adjustment that has hitherto been unstable depending on human hands. Further, by using the offset printing machine of the present invention, once the adjustment is performed at the beginning of printing, a printed matter having a stable color tone can be obtained until the end of printing.

[Brief description of drawings]

FIG. 1 is a side view of a dampening water and ink supply device of a printing machine for explaining a method of the present invention.

FIG. 2 is a block diagram conceptually explaining the present measurement method.

FIG. 3 is a graph showing changes in the amount of ink on the surface of an ink supply roll, which is measured and calculated by an example of the method of the present invention.

FIG. 4 is a graph showing the transition of the ink on the ink supply roll surface, which is measured and calculated by the method of Comparative Example 1.

FIG. 5 is a graph showing the transition of ink on the surface of an ink supply roll measured and calculated by the method of Comparative Example 2.

FIG. 6 is a flow chart for explaining the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printing plate cylinder 2 ... Blanket cylinder 3 ... Impression cylinder 10 ... Damping water supply roll group 20 ... Ink supply roll group 31 ... Infrared light source part 32 ... Photo sensor 33 ... Computer 34 ... Ink and dampening water supply amount control Instruction means

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Claims (3)

[Claims] 1. A black ink of a printing machine, which irradiates infrared light on a black ink film emulsified in fountain solution on the surface of an ink supply roll and measures the amount of black ink on the surface of the ink supply roll of the printing machine based on the reflected light amount. In the method for measuring the amount of ink, the infrared light in the infrared light wavelength region showing an absorbance peak for the ink is L, and the red light is on the shorter wavelength side than the infrared light L and has a small absorbance for water or ink. The external light is N, and the infrared light that is on the longer wavelength side than the infrared light L and has a low absorbance with respect to water or ink is M. A value P obtained based on the respective reflected light amounts L1, M1, and N1 obtained by irradiating the black ink film on the surface and the following formula P = (M1-L1) / (M1-N1) are supplied to the printing machine ink. Printing characterized by obtaining the amount of black ink on the roll surface Black ink amount measuring method of. 2. A black ink comprising: a black ink amount measuring means using the black ink amount measuring method according to claim 1; and a means for adjusting and controlling the black ink supply amount of a printing machine based on the result. Ink amount measurement control device. 3. An offset printing machine comprising the black ink amount measurement control device according to claim 2.