JP2008230177A - Letterpress printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a letterpress printer which does not generate printing quality troubles such as a step unevenness resulting from the generation of a slippage between the plate surface and the board surface by a total pitch gap and a speed gap in the printing direction caused by a difference in the relative speed between the circumferential speed of the letterpress surface and the moving speed of the surface plate on which a non-printing board is mounted as the circumferential speed modulates in response to the waviness on the letterpress surface when printing is performed by a fixed rotation speed by the swelling of the letterpress with a printing ink and unevenness in the thickness of the letterpress itself. <P>SOLUTION: The waviness on the letterpress surface prior to printing transfer is measured, so that a feed-back control in order to keep the circumferential speed of the letterpress surface at the time of transfer constant is performed. Thus, a precise printing machine which reduces printing troubles such as a total pitch slippage resulting from the waviness of the letterpress surface or step unevenness is constituted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a relief printing apparatus for forming a fine pattern on a printing medium uniformly and with high positional accuracy and more continuously and stably using a relief printing method and a resin relief printing. Suitable for forming high-definition patterns such as patterns in color filters for (LCD), light-emitting layers and charge transport layers of organic electroluminescence (EL) elements, electrode patterns on organic thin-film transistor (TFT) substrates, and shield patterns in electromagnetic wave shields The present invention relates to an improvement of a relief printing apparatus.

  At present, a photolithography method is mainly used as a method for forming a fine pattern on a substrate to be printed with uniform in-plane and high positional accuracy and more continuously and stably. This photolithography method has a problem that the process is complicated and manufacturing equipment necessary for pattern formation is expensive, resulting in an increase in manufacturing cost.

  There is also offset printing that uses silicone rubber as a printing blanket instead of photolithography, and transfers printing ink from a printing blanket to a substrate such as glass as a substrate. However, since the ink in the non-image area where the pattern is not formed is removed by the printing plate and discarded, a relief printing system excellent in ink mileage is attracting attention.

  A conventional relief printing apparatus will be described with reference to FIG.

As shown in FIG. 3, the letterpress printing machine is equipped with an anilox roll (or anilox plate) 1 for supplying ink to the plate surface of the letterpress 4, and a pattern forming letterpress 4 mounted via a block cushion 3. The printing plate cylinder 5, the substrate surface plate 6 on which the substrate 7 to be printed is placed, and the doctor blade 2 that scrapes off excess ink from the anilox roll 1. Here, the surface thickness of the relief plate 4 is determined in advance by measuring a representative point in advance to determine the rotational speed of the plate cylinder.
Further, the rotation speed of the plate cylinder is constant at the time of print transfer, and the platen on which the substrate to be printed is placed moves at the same speed as the rotation speed (circumferential speed) to perform ink transfer.

  In letterpress printing, this printing plate is made of a material that is deformed by pressure, such as resin or rubber, and does not require a very high printing pressure. Further, since the printing plate is not a hard material such as metal or glass, printing can be performed even on a material (for example, a glass substrate) on which a substrate to be printed is easily damaged.

  At the time of printing, ink is supplied from an ink supply mechanism to a roll called an anilox roll, which is uniformly grooved throughout. Next, the printing plate (letter plate) held on the plate cylinder is brought into contact with the anilox roll to transfer a certain amount of ink to the printing plate (letter plate). Finally, printing is performed by transferring ink from the printing plate to the substrate to be printed.

  Even with such relief printing, a method using a resin as a printing plate can efficiently form a precise pattern on a substrate to be printed such as glass.

  In printing, the difference in transfer speed between the printing plate and the substrate to be printed is important. For example, in offset printing, a large speed difference causes a phenomenon called slur that causes a print flow in the printing direction.

  If a speed difference is generated between the plate surface speed and the substrate surface speed when transferring the ink coated on the plate surface to the substrate in relief printing, the relief surface is transferred while sliding on the substrate surface.

  For this reason, the total pitch in the printing direction changes, and depending on the degree of slipping during transfer, there is an influence on printing quality such as unevenness of steps.

  In printing for the purpose of forming a fine pattern, slight print quality troubles such as total pitch deviation and unevenness that do not pose a problem in commercial offset printing and letterpress printing can be a major product trouble in the final product.

  At present, as a method of reducing the unevenness in level, there is a case where an ink having a low viscosity is used so that the transferred ink can be easily leveled (flattened).

  In addition, regarding total pitch deviation, marks that can be measured with a length measuring machine that can measure the distance between multiple points are pre-installed on the printing plate, and the distance between marks printed after printing is measured and corrected to the next printing. Is reflected. Here, as a method, when the transfer speed of the platen is fixed and the transfer movement speed of the surface plate on which the substrate to be printed is placed is adjusted, the transfer movement speed of the substrate surface plate is constant and the plate cylinder is fixed. When the rotational speed at the time of transfer is adjusted, the transfer speed of the plate cylinder and the substrate surface plate may be adjusted.

  However, when the low viscosity ink as described above is used, the required film thickness may not be obtained, and the cell volume (groove volume) of the anilox roll on which ink is applied to the printing plate must be changed.

  In order to change the volume, it is necessary to prepare an anilox that has been engraved in advance, and there is a problem that the burden is large in terms of cost and replacement work.

  An object of the present invention is to measure the thickness of a relief plate immediately before transfer during printing in a conventional relief printing apparatus for precision pattern formation, and the peripheral speed of the plate surface and the relative speed of the substrate surface plate are the same speed. Thus, it is an object of the present invention to provide a relief printing apparatus having a mechanism capable of modulating the transfer speed of a plate cylinder or a substrate surface plate and printing with stable printing quality.

In order to achieve the above object, the relief printing apparatus according to the present invention provides:
It is characterized by having a feedback control function that converts the waviness amount into the peripheral speed of the relief plate surface and modulates the rotational speed of the plate cylinder in real time while measuring the relief of the relief surface during printing.

  Here, regarding the amount of swell of the plate surface and the peripheral speed of the plate surface, even if the angular velocity of the plate cylinder is constant, if the plate thickness is uneven, the peripheral speed on the plate surface slightly changes. The change is expressed by the following equation. The rate of speed change when the radius to the plate surface is r and the waviness with respect to the radius r is Δr is expressed by (r + Δr) / r.

Specifically, the invention according to claim 1 is a relief printing apparatus using a relief plate as a printing plate, a rotary plate cylinder around which the relief plate is wound, and a substrate surface plate on which a substrate to be printed is placed. And an ink supply device for supplying ink to the relief printing plate, and measuring means for measuring the thickness variation of the relief printing plate due to variations in thickness of the relief printing plate or swelling of the relief printing plate that has received an ink solvent, and obtained by the measurement means. Provided is a relief printing apparatus characterized in that feedback control is performed so that the rotational speed of the relief plate surface is constant from the thickness variation amount of the relief relief.

  Further, in the invention according to claim 2, the measuring means is capable of continuously measuring in a printing direction within a specified range on a plate cylinder reference height provided on the plate cylinder circumference and on the relief plate surface. The relief printing apparatus according to claim 1, wherein a contact-type thickness sensor is used.

  According to the present invention, the amount of waviness on the surface of the relief printing plate can be controlled by feedback or the like, and the amount of fluctuation in the circumferential speed on the surface of the relief printing plate can be automatically controlled so as to always adjust to a constant circumferential velocity. As a result, it is not necessary to adjust the variation of the total pitch by trial printing, and it is possible to prevent the occurrence of printing quality troubles such as unevenness of steps.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As an embodiment of the present invention, as shown in FIG. 1, a plate cylinder reference height position 8 provided on the circumference of the plate cylinder and a thickness sensor capable of continuously measuring the thickness between the reference height position and the relief plate surface. 9 is constituted by a printing machine in which 9 is installed.

  First, as shown in FIG. 1, the plate cylinder rotates to the sensing position of the non-contact type thickness sensor and stops. Then, the measured value is reset to 0, and then the circumferential speed of the plate cylinder is sensated before printing transfer with the non-contact type thickness sensor as shown in FIG. Print by reflecting in. As a result, printing is performed at the same peripheral speed on the surface of the relief printing plate and the moving speed of the surface plate on which the printing substrate is placed.

As shown in FIG. 2, in a printing apparatus provided with a plate cylinder reference height position 8 provided on the circumference of the plate cylinder and a thickness sensor 9 capable of continuously measuring the thickness between the reference height and the relief plate surface, When the sensing point on the cylinder reference height 8 is point A, the sensing point on the letterpress surface is point B, and the point on the letterpress surface being transferred is point C, the point from the center point O of the plate cylinder to point A Let radius be r, radius to point _B is R _B , radius to point _C is R _C.

The plate cylinder reference height 8 (= r) portion whose distance from the plate cylinder center is known in advance is measured by the thickness sensor 9, and then the surface of the relief printing plate is measured by the sensor 9 as a displacement amount based on the value. To do. The apparent radius of the relief plate surface when the plate thickness is P [mm] is r + P [mm]. When the plate cylinder rotates at an angular velocity ω [rad / sec], the peripheral velocity V _P of the relief plate surface is expressed by V _P = ω · r [mm / sec].

  Here, the speed control when the sensing point measured at the point C reaches the print transfer position B is shown below.

The moving speed of the surface plate is V [mm / sec], and the period T _B (time required for one rotation of the plate cylinder) at the point _B is T _B = 2πR _B / V [sec].

Here, the angular velocity ω B at point _B is ω _B = 2π / T _B = V / R _B [rad / sec].

When the point C reaches the point B position, the angular velocity ω _C at which the peripheral speed is the same as the point B point is ω _C = ω _B × R _B / R _C [rad / sec] = V / R _C [ mm / sec], which is obtained from this relationship and used for feedback control.

  It should be noted that the present invention is not limited to the above-described embodiments, and improvements, modifications, etc. within the scope of achieving the present invention, such as reverse offset printing using a blanket instead of a relief printing, depart from the gist of the present invention. Not what you want.

  In addition to blanket winding or a surface plate for placing a substrate to be printed on the relief plate related to the present invention, a lithographic plate for removing printing ink applied to a non-image area on the blanket is placed. In reverse offset printing with a surface plate, the blanket thickness can be measured and applied to the peripheral speed control of the blanket surface.

It is the schematic side view explaining the measurement of the reference height position installed on the printing drum circumference. It is the schematic side view explaining the measurement of the thickness of the letterpress surface wound on the plate cylinder. It is a schematic side view of the conventional relief printing apparatus.

Explanation of symbols

1 Anilox roll 2 Doctor blade 3 Cushion under printing 4 Printing plate (Letter)
5 Plate Cylinder 6 Substrate Surface Plate 7 Printed Substrate 8 Plate Cylinder Reference Height Position 9 Thickness Sensor 10 Moving Surface Plate

Claims (2)

A letterpress printing apparatus using a letterpress as a printing plate,
A rotary plate cylinder for winding the relief plate, a substrate surface plate on which a substrate to be printed is placed, and an ink supply device for supplying ink to the relief plate,
2. A letterpress printing apparatus characterized in that a measurement means for measuring a thickness variation of a relief plate and feedback control is performed so that the rotational speed of the relief plate surface is constant from the thickness fluctuation amount of the relief plate obtained by the measurement means.   The measuring means uses a plate cylinder reference height provided on the circumference of the plate cylinder and a non-contact type thickness sensor that can continuously measure in the printing direction within a specified range on the surface of the relief printing plate. The relief printing apparatus according to claim 1.

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