JP2010082502A - Pattern forming system - Google Patents

Abstract

A pattern forming apparatus for irradiating a droplet in flight with laser light to dry the droplet in flight and improving the drying efficiency of the droplet in flight is provided.
A half mirror 34 is provided to divide a basic laser beam Le emitted from a laser light source 32 into a first laser beam Le1 and a second laser beam Le2, and the first and second laser beams Le1, Le2 are provided. DOEs 42a and 42b for converting the intensity distribution from the Gaussian distribution to the top hat type distribution are arranged on the road. Then, the first laser beam Le1 and the second laser beam Le2 having a top hat type distribution are irradiated to the droplet in flight from both sides so as to face each other.
[Selection] Figure 5

Description

  The present invention relates to a pattern forming apparatus for irradiating a droplet in flight with laser light.

  A multilayer substrate made of low temperature co-fired ceramics (LTCC) has excellent high-frequency characteristics and high heat resistance, and thus is widely used for a substrate of a high-frequency module or an IC package. Such an LTCC multilayer substrate is generally manufactured by laminating green sheets on which circuit patterns are drawn using metal ink and firing them together.

In the step of drawing the circuit pattern, a so-called ink jet method has been proposed in which metal ink is ejected as fine droplets in order to increase the density of the circuit pattern (for example, Patent Document 1). In the ink jet method, a circuit pattern is drawn by discharging a droplet having a capacity of several to several tens of picoliters from a discharge head in which a large number of nozzles are arranged. The ink jet method enables further miniaturization of circuit patterns and narrower pitches by changing the droplet discharge position.
JP 2005-57139 A

  By the way, in order to form a high-definition pattern using the ink jet method, it is preferable to reduce the landing diameter by quickly drying the discharged droplets and suppressing wetting spread on the substrate. As one method, a method of irradiating a droplet in flight ejected from an ejection head with laser light to promote drying of the droplet during flight has been studied. When evaporating a desired amount of evaporation component using such a method, the minimum energy required for the laser beam can be roughly defined according to the desired amount, so that it is possible to improve the utilization efficiency of the laser beam. A mode in which the minimum energy is given to the droplet in flight is preferable.

  On the other hand, as the cross-sectional intensity distribution of the laser light described above, a circular normal distribution (Gaussian distribution) in which the intensity near the center of the laser light is the highest is generally used. When a laser beam having such a cross-sectional intensity distribution is irradiated onto a droplet in flight, the discharged droplet first rises in temperature at the base of the Gaussian distribution and then passes through the peak region of the Gaussian distribution. Therefore, when the heated droplet passes through the peak region, excessive energy that greatly exceeds the heat of vaporization is supplied to the droplet per unit time, and the droplet solvent So-called bumping occurs, in which the phase transition of the liquid droplets or the dispersion medium occurs instantaneously in the entire droplet, and the droplet itself is scattered. On the other hand, in order to prevent such bumping, a method of further suppressing the intensity of the laser beam so as not to exceed the heat of vaporization in the peak region of the Gaussian distribution can be considered. However, in such a case, bumping in the peak region can be prevented, but since the intensity of the entire laser beam itself is reduced, the temperature of the droplet is difficult to rise even at the base of the Gaussian distribution, and as a result Insufficient drying.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a pattern forming apparatus for irradiating a flying droplet with a laser beam to dry the flying droplet. Another object of the present invention is to provide a pattern forming apparatus that improves the drying efficiency of the film.

The pattern forming apparatus of the present invention includes a discharge head that discharges a liquid droplet containing an evaporation component and a pattern forming material from a nozzle toward a drawing target, and irradiates the droplet during the flight with laser light. A laser irradiation unit that evaporates a predetermined amount of the evaporation component, and forms a pattern by landing the droplet on the drawing target, wherein the laser irradiation unit emits a laser beam And a laser shaping part for shaping the intensity distribution of the laser beam so that the intensity distribution of the laser beam is partially flat on the path between the nozzle and the position where the droplet lands. I have.

  In a pattern forming device that dries a droplet by irradiating a laser beam onto the flying droplet and evaporating the evaporation component from the flying droplet, when the temperature of the evaporation component of the droplet is near the boiling point The droplets dry most efficiently. According to the pattern forming apparatus of the present invention, the intensity distribution of the laser light applied to the droplets in flight can be always an intensity distribution having the same intensity from immediately after ejection until landing. According to such a configuration, the amount of heat given during flight is restricted to an amount corresponding to the desired evaporation amount, and the evaporation component contained in the discharged droplet can be raised to near the boiling point in a short time from the time of discharge. it can. Therefore, it is possible to devote much of the flight period from when the droplet is ejected until it lands to the evaporation process of the evaporation component. As a result, the drying efficiency of the droplets in flight can be improved.

  In the pattern forming apparatus, the laser emitting unit emits a pair of laser beams, the laser forming unit shapes at least one intensity distribution of the pair of laser beams, and the laser irradiation unit includes the pair of laser beams. The gist is to irradiate the droplets with laser light in a manner opposite to each other across the path.

  According to this pattern forming apparatus, a pair of laser beams with at least one of the intensity distributions made flat with respect to the droplets are irradiated in a state of facing each other. Therefore, the evaporation component contained in the ejected droplet can be raised to near the boiling point in a short time from the time of ejection by the amount that makes the intensity distribution of at least one of the pair of laser beams flat. The drying efficiency of can be improved.

  The gist of the pattern forming apparatus is that the laser emitting unit emits a pair of laser beams having the same intensity on the path, and the laser shaping unit shapes each intensity distribution of the pair of laser beams. To do.

  When the droplet in flight evaporates the evaporation component, a reaction force against the kinetic force of the evaporation component acts on the droplet. Therefore, the reaction force from the higher evaporation rate to the lower one acts on the droplet, and the reaction force is asymmetric with respect to the droplet discharge direction and is excessive with respect to the droplet. In the case of action, the flying flight of the droplets due to the reaction force against the movement force occurs, and the landing position shifts.

  According to this pattern forming apparatus, a single droplet is irradiated with laser light from opposite directions, so that it is only possible to improve the drying efficiency of the droplet as compared with the case where laser light is irradiated from one side. In addition, by making the intensity distribution of the pair of laser beams equal, it is possible to suppress the flight bending of the droplets.

The gist of this pattern forming apparatus is that the laser emitting section has a branching section that branches the basic laser light from one laser light source into the pair of laser lights.
According to this pattern forming apparatus, since a single laser light source for generating a pair of laser beams is sufficient by providing the branching section, the laser irradiation section can be made simple. Further, for example, after the basic laser light from one laser light source is branched to generate a pair of laser light, the intensity distribution conversion by the laser forming unit can be executed. In other words, the laser forming part for converting the intensity distribution of the laser light can be arranged on the target path side with respect to the branch part.
Thereby, it becomes possible to arrange | position a laser shaping | molding part in the position close | similar to a target path | route, and can suppress the diffraction of the laser beam between a laser shaping | molding part and a target path | route. That is, it is possible to reliably irradiate the droplets with the laser light whose intensity distribution has been converted.

  Hereinafter, an embodiment in which the pattern forming apparatus of the present invention is embodied in a droplet discharge apparatus will be described with reference to FIGS. FIG. 1 is a diagram schematically showing a perspective structure of a droplet discharge device. FIG. 2 is a perspective view showing a perspective structure of the ejection head of this embodiment, and FIG. 3 is a partial cross-sectional view showing an internal sectional structure of the ejection head. FIG. 4 is a plan view showing the arrangement relationship between the green sheet, which is a drawing object, and the ejection head.

  As shown in FIG. 1, a stage 11 that can reciprocate along the longitudinal direction of the base 11 is mounted on a base 11 of a droplet discharge device 10 as a pattern forming apparatus. In the present embodiment, the longitudinal direction of the base 11, the upper right direction in FIG. 1 is the + X direction, and the opposite direction to the + X direction is the −X direction. Further, the horizontal direction orthogonal to the + X direction, the upper left direction in FIG. 2 is referred to as the + Y direction, and the opposite direction to the + Y direction is referred to as the −Y direction. Further, the upper direction in the vertical direction is defined as the + Z direction, and the direction opposite to the + Z direction is referred to as the −Z direction.

  On the upper surface of the stage 12 mounted on the base 11, a green sheet GS as a drawing object is positioned and fixed to the stage 12 with the drawing surface GSa facing upward. The stage 12 scans the positioned green sheet GS in the + Y direction or the −Y direction at a predetermined speed when a stage motor (not shown) provided on the base 11 rotates forward or reverse.

  A guide member 13 formed in a gate shape is installed on the upper side of the base 11 along the + X direction, and an ink tank for supplying the conductive ink Ik as a liquid material is provided on the upper side of the guide member 13. 14 is disposed. The ink tank 14 stores the conductive ink Ik composed of a dispersion system of conductive fine particles, and supplies the stored conductive ink Ik to the discharge head 15 while adjusting a predetermined temperature under a predetermined pressure. The conductive fine particles as the pattern forming material are fine particles having a particle diameter of several nm to several tens of nm. For example, silver, gold, copper, platinum, palladium, rhodium, osmium, ruthenium, iridium, iron, tin, cobalt, A metal such as nickel, chromium, titanium, tantalum, tungsten, indium, or an alloy thereof can be used. The dispersion medium as the evaporation component is not particularly limited as long as the conductive fine particles are uniformly dispersed. For example, water or an aqueous solution mainly containing water or an organic solvent mainly containing an organic solvent such as tetradecane is used. be able to. In the conductive ink Ik of the present embodiment, silver is used as the conductive particles and water is used as the dispersion medium.

  A carriage 16 that can move in the + X direction and the −X direction is mounted on the guide member 13, and an ejection head 15 is mounted on the carriage 16. The carriage 16 scans the ejection head 15 in the + X direction or the −X direction when a carriage motor (not shown) provided on the guide member 13 rotates forward or backward.

  As shown in FIG. 2, the ejection head 15 includes a head substrate 17 that is positioned and fixed to the carriage 16 and extends in the + X direction, and a head body 20 that is supported by the head substrate 17. The head substrate 17 has a connection terminal 17 a at the end in the −X direction, and various control signals from the outside are input to the head main body 20 from the connection terminal 17 a and various detection signals from the head main body 20. Is output from the connection terminal 17a to the outside.

A nozzle plate 21 disposed so as to face the green sheet GS is attached to the bottom of the head body 20. The nozzle plate 21 is configured such that when the head body 20 is disposed immediately above the green sheet GS, the bottom surface (hereinafter simply referred to as the nozzle forming surface 21a) and the drawing surface GSa are substantially parallel. A flight space of the droplet D, which is a space sandwiched between the nozzle forming surface 21a and the drawing surface GSa, is formed. Further, when the head body 20 is disposed immediately above the green sheet GS, the nozzle plate 21 sets a platen gap PG, which is a distance between the nozzle forming surface 21a and the drawing surface GSa, to a predetermined distance (see FIG. 3, this embodiment). It is maintained at 1000 μm in the form. On the nozzle forming surface 21a of the nozzle plate 21, a plurality of nozzles N penetrating the nozzle plate 21 in the Z direction are arranged at equal intervals along the X direction at a nozzle pitch Dx.

  As shown in FIG. 3, the head body 20 includes a cavity 22, a vibration plate 23, and a piezoelectric element PZ as a pressure generating element above each nozzle N. Each cavity 22 is connected to a common ink tank 14 via a supply tube 20T, and thereby accommodates the conductive ink Ik from the ink tank 14 and supplies the conductive ink Ik to each nozzle N. . The vibration plate 23 vibrates the meniscus of the nozzle N along with the expansion and contraction of the volume of the cavity 22 by vibrating the region facing each cavity 22 in the Z direction. Each piezoelectric element PZ is supplied with a drive voltage that is a voltage waveform that defines the contraction amount, contraction speed, extension amount, and extension speed. Each time such drive voltage is input to the piezoelectric element PZ. Further, the piezoelectric element PZ contracts and expands in the Z direction, so that the diaphragm 23 vibrates in the Z direction.

  In the ejection head 15 having such a configuration, when each piezoelectric element PZ contracts and expands in the Z direction, a part of the conductive ink Ik accommodated in each cavity 22 has a size and speed corresponding to the driving voltage. The droplets D are discharged from the nozzle N. The droplet D discharged from the nozzle N flies in the above-described flight space and lands on the drawing surface GSa of the green sheet GS.

  At this time, the droplet D discharged from the nozzle N can surely fly along the Z direction from the nozzle N because the resultant force of the external force applied to the droplet D acts only in the Z direction. It flies over the target path TL which is a virtual line including the nozzle N and extending in the Z direction. On the other hand, when the resultant force of the external force applied to the droplet D acts greatly in the direction intersecting the Z direction, the droplet D discharged from the nozzle N deviates from the target path TL according to the action of the resultant force. Flying over the route, the so-called flight bend is a factor that impairs the accuracy of the landing position.

  As shown by the one-dot chain line in FIG. 4, the drawing surface GSa of the green sheet GS is virtually divided by a dot pattern lattice DL which is a two-dimensional rectangular lattice. The dot pattern lattice DL is a virtual lattice in which the lattice interval in the + X direction and the lattice interval in the + Y direction are set at predetermined intervals. For example, the + X-direction grid spacing of the dot pattern grid DL is defined by the nozzle pitch Dx, and the + Y-direction grid spacing of the dot pattern grid DL is the product of the droplet D ejection period and the scanning speed of the stage 12. Is defined by the discharge pitch Dy calculated from When such a dot pattern grid DL is scanned by the stage 12, the ejection head 15 described above is arranged such that each grid point T of the dot pattern grid DL crosses the target path TL, and the drawing surface GSa is drawn from each nozzle N. The selection as to whether or not to discharge the droplets D is set for each lattice point T. In FIG. 4, for convenience of explaining each lattice point T of the dot pattern lattice DL, the lattice interval of the dot pattern lattice DL and the nozzle pitch Dx of the ejection head 15 are shown sufficiently enlarged.

In order to effectively evaporate a desired amount of the dispersion medium from the droplet D ejected from the nozzle N, first, the temperature of the droplet D at room temperature is set to the highest temperature in the range where the liquid does not boil. target temperature near heat for allowing to warm to, the first heat quantity q ₁ is a heat for allowing heated to the boiling point of the droplets D dispersion medium is for example at room temperature is needed is. Next, a second heat quantity q which is latent heat (heat of vaporization) for smoothly causing phase transition of the dispersion medium of the droplet D into a gas while maintaining the state where the droplet D heated by the first heat quantity q ₁ does not boil. ₂ is required. That is, in order to evaporate a predetermined amount of the dispersion medium from the droplets D at room temperature, only the total heat amount q, which is an added value of the first heat amount q1 and the second heat amount q2, is required. Such an amount of heat can be estimated by calculation using the properties of the conductive ink Ik, the drive voltage applied to the piezoelectric element PZ, and the volume of the droplet D, and is determined by direct measurement based on various experiments. You can also

For example, when the first heat quantity q ₁ and the second heat quantity q ₂ are estimated by the above-described calculation, the molar fraction of the dispersion medium and the conductive fine particles obtained from the properties of the conductive ink Ik, the dispersion medium, and the conductivity This can be performed based on the specific heat capacity of the fine particles, the weight W of the droplet D obtained based on the driving voltage, and the temperature of the droplet D at the time of ejection. Among the evaporation components evaporated from the minute droplets D as described above, those that diffuse to a distance far away from the surface of the droplet D and those that remain on the target path TL and remain on the path. Some increase the partial pressure. For this reason, the evaporation amount of the droplets at each temperature increases as the concentration of the evaporation component remaining in the target path TL decreases, and conversely decreases as the concentration of the evaporation component in the target path TL increases. Therefore, the differential equation related to the mass balance of the droplet using the mass transfer flux of the evaporated component based on the density of the evaporated component on the droplet surface and its diffusion, etc., and the heat balance of the droplet considering the heat of vaporization of the droplet differential equations involved in the news can be estimated the first heat quantity q ₁ and second heat quantity q ₂ by solving the like motion equation of the droplets in consideration of air resistance to drop. Further, when the first heat quantity q ₁ and the second heat quantity q _{2 are} determined by the above-described experiment, light of a different heat quantity is irradiated to the droplet D while the droplet D in flight is imaged with a high-speed camera. The first heat quantity q ₁ and the second heat quantity q ₂ can also be obtained by directly measuring the highest heat quantity that can maintain the state in which the droplet D does not boil.

  Next, an optical system for irradiating the droplet D in flight with laser light to dry the droplet D will be described with reference to FIG. FIG. 5 is a diagram schematically illustrating an optical configuration of the laser irradiation unit 31 mounted on the droplet discharge device 10, and FIG. 6 schematically illustrates an irradiation angle of the laser beam with respect to each droplet D. It is a figure. FIG. 7 is a diagram schematically showing the intensity distribution of the laser light in the target path TL.

  As shown in FIG. 5, the laser irradiation unit 31 includes a laser light source 32 as a laser emission unit, a collimating lens 33, a half mirror 34 as a branching unit, and reflection mirrors 35, 36, 37, 38, and 39, 1 laser shaping part 40a and 2nd laser shaping part 40b are provided. The laser light source 32 is a device that emits basic laser light Le whose cross-sectional intensity distribution is a Gaussian distribution.

The laser light source 32 is a so-called solid-state laser, and includes a YAG (Yttrium Aluminum Garnet) laser oscillator 32a and a harmonic unit 32b. The YAG laser oscillator 32a includes an yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ) crystal to which neodymium ions (Nd ³⁺ ) are added, and emits a fundamental wave (wavelength: 1064 nm) of YAG laser light that is invisible light in the near infrared. Generate. The harmonic unit 32b is provided with a nonlinear optical crystal, and the fundamental wave of the YAG laser light generated by the YAG laser oscillator 32a is passed through the nonlinear optical crystal, so that the YAG laser light, which is visible light, is transmitted. Convert to second harmonic (SHG: Second harmonic generation, wavelength: 532 nm). The laser light source 32 causes the second harmonic of the YAG laser light to enter the collimating lens 33 as the basic laser light Le.

The collimator lens 33 is a plano-convex lens having a predetermined curvature on the exit surface side, and converts the light beam of the basic laser light Le emitted from the laser light source 32 into parallel light parallel to the optical axis, thereby generating a half mirror. 34 is incident. The half mirror 34 is a first laser beam Le which is a pair of laser beams having the same energy as the basic laser beam Le emitted from the collimator lens 33.
1 and the second laser beam Le2. Each of the reflecting mirrors 35 and 36 is a plane mirror having a reflecting surface that reflects the first laser beam Le1 that is the transmitted light of the half mirror 34, and the first laser beam Le1 that is the reflected light is a first laser forming unit. It is made incident on 40a. Each of the reflection mirrors 37 to 39 is a plane mirror having a reflection surface that reflects the second laser beam Le2 that is the reflection light of the half mirror 34, and the second laser beam Le2 that is the reflection light is a second laser forming unit. It is made incident on 40b.

  The first laser shaping unit 40a includes a cylindrical lens 41a and a diffractive optical element (DOE: Differential Optical Element, hereinafter referred to as DOE) 42a on the optical path of the first laser beam Le1. The second laser shaping unit 40b includes a cylindrical lens 41a and a DOE 42a on the optical path of the second laser beam Le2.

  The cylindrical lenses 41a and 42b are lenses each having an exit surface that has a curvature only in the short direction, and the cross sections of the first laser light Le1 and the second laser light Le2 converted into parallel light by the collimating lens 33 are shown. It converts into the rectangular shape extended along the said nozzle formation surface 21a. The first laser light Le1 and the second laser light Le2 incident on the cylindrical lenses 41a and 41b have a predetermined width in the Z direction. Therefore, when the laser light is irradiated to the flight space without being formed by the cylindrical lenses 41a and 41b, the end portion in the Z direction of the laser light is the ejection head 15, the green sheet GS, the stage 12, and the like. And the energy of the first laser beam Le1 and the second laser beam Le2 is partially lost. The cylindrical lenses 41a and 41b convert the Z-direction components of the first laser light Le1 and the second laser light Le2 from the corresponding reflecting mirrors, respectively, and the first laser light Le1 and the second laser light Le2 in the Z direction. The cross-sectional shape is formed so that the length is equal to the platen gap PG (1000 μm in this embodiment). Thereby, the first laser light Le1 and the second laser light Le2 can be guided to the target path TL of the droplet D while suppressing the energy loss of the first laser light Le1 and the second laser light Le2.

  The DOEs 42a and 42b are cross-sectional intensity distributions of the first laser beam Le1 and the second laser beam Le2 formed by the cylindrical lenses 41a and 42a, respectively, and a top-hat type cross-sectional intensity distribution (hereinafter referred to as a flat-hat type cross-sectional intensity distribution) , And then irradiate the flight space. FIG. 7 is a diagram schematically showing an example of the intensity of the laser light whose cross-sectional intensity distribution is converted into a top-hat type distribution. As shown in FIG. 7, the flat intensity distribution which is the above-described top hat type distribution is that the difference between the maximum intensity and the average intensity and the difference between the minimum intensity and the average intensity are ± 5 with respect to the average intensity, respectively. The distribution is within%. Such flatness can be selected as appropriate according to the accuracy of the landing position of the droplet D and the accuracy of the landing diameter, which are the design rules for the drawing pattern.

Further, the optical axes of the DOEs 42a and 42b are arranged so as to be positioned at intermediate positions of the target path TL, respectively, and the first laser beam Le1 and the second laser beam are applied to the droplets D ejected from all the nozzles N. In order to irradiate the light Le2, it is inclined in the horizontal direction by a predetermined inclination angle θ (θ: 0 ° <θ ≦ 90 °) with respect to the arrangement direction of the nozzles N (the one-dot chain line direction shown in FIG. 5). As shown in FIG. 6, the inclination angle θ is selected within a range that satisfies sin θ ≧ 2r / Dx, for example, when the diameter of the droplet D is 2r. If the tilt angle θ satisfies such a condition, even if the first laser beam Le1 and the second laser beam Le2 are irradiated to the droplet D from each nozzle N ejected at the same timing, The droplet D closer to the DOE does not block the first laser light Le1 and the second laser light Le2 with respect to the droplet D relatively far from the DOE. Therefore, the first laser beam Le1 and the second laser beam Le2 can be evenly irradiated to all the droplets D ejected simultaneously from the ejection head 15. Further, even if the laser light satisfies sin θ> 2r / Dx, the laser light is divided so as to correspond to the flight paths of the droplets D ejected from the nozzles N by the DOEs 42a and 42b. Laser light that passes through the space can be minimized, and utilization efficiency of the laser light can be improved.

  According to the irradiation mode of the first laser beam Le1 and the second laser beam Le2, the energy (total energy E) corresponding to the sum of the energy received from the first laser beam Le1 and the energy received from the second laser beam Le2 is a droplet D. Given to. The laser irradiation unit 31 in the present embodiment is configured in such a manner that the integrated value of the total energy E and the total heat quantity q described above are equal by the cooperation of the above-described DOEs 42a and 42b.

  According to such a configuration, the droplet D in flight continues to receive laser light having a laser intensity P, which is a flat intensity, from both sides in a period from immediately after ejection to landing, and can maintain a state where it does not boil. It is possible to quickly raise the temperature to a high temperature and to avoid supplying excessive energy per unit time that greatly exceeds the heat of vaporization at that time.

The cross-sectional intensity distributions of the first laser beam Le1 and the second laser beam Le2 can be set as follows, for example. First, to set the laser intensity P on the target route TL, on the basis of the flight speed v ₀ of the platen gap PG and the droplet D, the flight time to landing since the ejected droplet D t (= PG / v ₀ ) is obtained. Further, by using this platen gap PG and the diameter 2r of the droplet, an irradiation cross-sectional area for the droplet D in flight can be obtained as PG × 2r. The laser intensity P on the target path TL is expressed by the following equation (1) from the flight period t, the platen gap PG, and the diameter 2r of the droplet D so as to receive the total energy E described above at the irradiation cross section. Set based on.

P = E / ((PG × 2r) × t) (1)
Here, when the dispersion medium evaporates from the droplet D in flight, a reaction force against the kinetic force accompanying the evaporation acts on the droplet D. Therefore, if the reaction force acts in the direction from the higher evaporation rate to the lower evaporation rate and the evaporation rate is not symmetrical about the discharge direction of the droplet D, the reaction force against the kinetic force is applied. The flying bending of the droplet D is induced by the force, and the landing position is displaced. Therefore, by dividing the laser intensity P set as described above into the first laser beam Le1 and the second laser beam Le2 that are opposed to each other, that is, by setting each intensity to P / 2, the droplets Since the evaporation rate of D is symmetric with respect to the ejection direction and the reaction force against the kinetic force accompanying the evaporation of the dispersion medium cancels out, the flying curvature of the droplet D is less likely to occur, and the landing position is displaced. It can also be suppressed.

  When the laser intensity P becomes excessively high, the light pressure of the laser light acts excessively on the droplet D, and the phenomenon that the droplet D deviates from the target path TL, a so-called flight curve. May occur. In addition, when the flight period t is excessively short or when the size of the droplet D becomes excessively large, the energy of the laser beam absorbed near the surface of the droplet D is sufficiently diffused to the center of the droplet D. It may not be possible. Therefore, through various experiments and computer simulations that are performed in advance, the data related to the intensity range causing the above-mentioned flight bending and insufficient thermal diffusion is acquired as appropriate intensity data, and the laser intensity P as the above calculation result is the appropriate intensity. It may be an aspect for determining whether or not the data is within the range. When the laser intensity P is out of the above data range, the design rules are reviewed and the flight period t is changed so that the laser intensity P falls within an appropriate range. Also good.

In this way, by always irradiating the flying droplet D with laser light having a constant laser intensity, the temperature can be quickly raised to, for example, the boiling point of the dispersion medium. In the period, the period in which the droplet D is in the vicinity of the same boiling point can be lengthened. When the laser beam is irradiated to the minute droplet D as described above, even if the energy of the laser beam is absorbed near the surface of the droplet D, the surface of the droplet is heated by the absorbed energy, As the heat near the surface diffuses into the center of the droplet D, the temperature of the entire droplet D rises as a result. Then, since the temperature of the droplet D is high enough to maintain its boiling state, for example, the boiling point of the dispersion medium, the energy of the laser light absorbed near the surface becomes energy for vaporizing the dispersion medium. By being sequentially converted, the dispersion medium having an evaporation amount corresponding to the energy supplied by the laser beam evaporates from the surface of the droplet D. As a result, it is possible to maintain a stable evaporation state while suppressing the bumping of the droplet D, and it is possible to improve the drying efficiency of the droplet D as much as the period near the boiling point can be lengthened.

  Naturally, the maximum evaporation amount per unit time in the droplet D increases as the temperature of the droplet D increases. Further, as described above, the lower the concentration of the evaporated component remaining in the target route TL, the higher the concentration, and the lower the concentration of the evaporated component in the target route TL, the lower the concentration. Therefore, when the evaporated component evaporated from the preceding droplet D is not sufficiently diffused and remains in the target path TL, the laser beam having the same energy as that of the preceding droplet D is applied to the subsequent droplet D. In some cases, the evaporation amount decreases, and the energy to be converted into the heat of vaporization corresponding to the decrease is accumulated in the subsequent droplet D, thereby inducing the sudden boiling of the droplet D. is there.

  In the present embodiment, by performing various computer simulations and experiments related to the diffusion of the evaporation component, a period during which the evaporation component evaporated from the droplet D is sufficiently diffused from the target path TL is acquired, and the period (for example, 1 millisecond) is adopted as the discharge interval, that is, the discharge cycle is set to 1 kHz. According to such a configuration, since the concentration of the evaporated component in the target path TL becomes the same every time the droplet D is discharged, the drying efficiency of the subsequent droplet D due to the evaporated component evaporated from the preceding droplet D is reduced. Can also be avoided.

  Next, the operation and effect of the droplet discharge device 10 configured as described above will be described. FIG. 8 is a diagram schematically showing a state in which the first laser beam Le1 and the second laser beam Le2 converted into the top hat type distribution are applied to the droplet D in flight. On the other hand, FIG. 9 is a diagram schematically showing a case where laser light having a Gaussian distribution is irradiated from both sides with the optical axis being shifted from the droplet.

  As shown in FIG. 8, the droplets D ejected from the nozzle N are irradiated with the first laser beam Le1 and the second laser beam Le2 from both sides sandwiching the target path TL. The first laser beam Le1 and the second laser beam Le2 are generated by the first and second laser molding units 40a and 40b so that the total energy in the target path TL becomes the intensity distribution of the top hat distribution with the total energy E. It has been converted. Therefore, compared to the case of using a laser beam having a Gaussian distribution, not only excessive energy is not supplied to the droplet D reaching the target temperature, but also the temperature rise of the droplet D at the base of the Gaussian distribution. The droplet D can be quickly heated to the target temperature. Then, due to the temperature rise of the droplet D, the droplet D can continue to fly near the target temperature in the remaining flight period of the droplet D. In the droplet D flying in such a state, the temperature of the droplet D is high enough to maintain the boiling state, for example, the boiling point of the dispersion medium. Is sequentially converted into energy for vaporizing the evaporation component. As a result, it is possible to maintain a stable evaporation state under high evaporation efficiency while suppressing the bumping of the droplet D, and the droplet D is dried by the amount that the temperature of the droplet D can quickly reach the target temperature. Efficiency can be improved. Since the laser beam corresponding to the total energy E is irradiated to the flying droplet D, the droplet D can be landed in a state where a desired amount of evaporation component is evaporated.

(Example)
Table 1 shows the measured values of the landing diameter when a droplet D having a spherical shape with a diameter of 25 μm was caused to fly at a flight speed of 7 m / s and the droplet D was irradiated with laser beams having different intensity distributions and intensities. Is shown. In the column showing the intensity distribution and intensity in Table 1, the first laser beam Le1 is shown on the top and the second laser beam Le2 is shown on the bottom.

That is, carried out by using a first laser beam Le1 forming a top-hat distribution at an intensity of 1.5 W / cm ^2, and a second laser beam Le2 forming a top-hat distribution at an intensity of 1.5 W / cm ² The landing diameter in the droplet D of Example 1 was obtained. In addition, the landing diameter of the droplet D of Example 2 was obtained by changing the intensity of the first laser beam Le1 to 1.0 W / cm ² and making the other conditions the same as in Example 1.

The 1.0 W / in strength cm ² and the first laser beam Le1 forming the Gaussian distribution, the droplets of Comparative Example 1 by using a second laser beam Le2 forming a Gaussian distribution in intensity of 1.0 W / cm ² The landing diameter in D was obtained. Further, the landing diameter of the droplet D of Comparative Example 2 was obtained by landing the droplet D without irradiating the first laser beam Le1 and the second laser beam Le2. In the laser light used in Example 2 and Comparative Example 1, the output of the Gaussian-distributed laser light is set smaller than the output of the top-hat-type distributed laser light. The highest value is set in a range in which it is possible to suppress the bumping and the displacement of the landing position.

表１に示すように、実施例１の着弾径は２５μｍであり、計測結果のなかで最も小さい値であることが分かる。また実施例１の着弾径は実施例２の着弾径よりも小さい値であり、また実施例２の着弾径は比較例１の着弾径よりも小さい値であることが分かる。こうした実測結果からも、レーザ強度の等しいトップハット型分布の第１レーザ光Ｌｅ１と第２レーザ光Ｌｅ２が液滴Ｄの両側から照射される実施例１において該液滴Ｄの乾燥が最も効率よく行われており、その濡れ広がりが抑制されていることが理解できる。また、一方からガウシアン分布のレーザ光を、他方からトップハット型分布のレーザ光を照射した実施例２においても、一方をトップハット型分布にした分だけ乾燥効率が向上していることが理解できる。

As shown in Table 1, the landing diameter of Example 1 is 25 μm, which is the smallest value among the measurement results. Also, it can be seen that the landing diameter of Example 1 is smaller than the landing diameter of Example 2, and the landing diameter of Example 2 is smaller than the landing diameter of Comparative Example 1. Also from these actual measurement results, in Example 1 where the first laser beam Le1 and the second laser beam Le2 having the same top intensity distribution with the same laser intensity are irradiated from both sides of the droplet D, the drying of the droplet D is most efficient. It can be understood that the wet spreading is suppressed. It can also be understood that in Example 2 where the laser light with Gaussian distribution was irradiated from one side and the laser light with the top hat type distribution was irradiated from the other side, the drying efficiency was improved by the amount of the one having the top hat type distribution. .

When a pair of laser beams having a Gaussian distribution is used as in Comparative Example 1, it is difficult to accurately match the optical axes of the pair of laser beams. For example, when the optical axis is shifted as shown in FIG. 9, first, the evaporation rate on the left side of the droplet D is increased by the laser beam Le10. The component mainly evaporates, and the droplet D is bent to the right by the reaction force against the kinetic force of the evaporated component. Next, since the evaporation rate on the right side of the droplet D is increased by the laser beam Le20, the evaporation component near the irradiated surface on the right side of the droplet mainly evaporates, and the reaction force against the kinetic force of the evaporation component Causes a flight curve on the left side. In addition, in the droplet D whose weight gradually decreases due to evaporation of the evaporation component, the flight curve as described above becomes larger than that immediately after ejection with a large weight. Therefore, as shown in FIG. 9, the droplet D causes a large flight curve from the target path TL to the left side. According to the experiment by the present inventor, for example, it has been found that the actual landing position is deviated by about 100 μm from the lattice point T of the target landing position only when the optical axis of the laser beam is deviated by about 10 μm.

  On the other hand, in the present embodiment, as shown in FIG. 8, the droplet D ejected from the nozzle N is irradiated with the first laser beam Le1 and the second laser beam Le2 having the same top intensity distribution from both sides. The As a result, the evaporation rate of the droplet D during flight tends to be symmetric with respect to the target path TL, and the reaction force against the kinetic force accompanying evaporation of the evaporation component cancels out, so that the flight bending of the droplet D hardly occurs. Therefore, the displacement of the landing position can be suppressed.

  In addition, when a pair of laser beams having a Gaussian distribution is used as described above, the entire flight process of the droplet D is described above in a state where the optical axes of the pair of laser beams are shifted in the ejection direction of the droplet D. The reaction force acting on the droplet D causes a large flight curve to the droplet D. On the other hand, when the intensity distribution in the present embodiment is used, the intensity distribution of the pair of laser beams is flat over the entire irradiation region, so that the optical axes of the pair of laser beams are shifted in the ejection direction of the droplet D. Even so, the reaction force described above is canceled in most of the flight process, and the reaction force described above acts only within a range equivalent to the amount of deviation of the optical axis. Therefore, even when the optical axis is deviated, the displacement of the landing position of the droplet D can be suppressed by the amount of irradiation with the laser beam having the top hat type distribution.

As described above, according to the droplet discharge device 10 of the present embodiment, the following effects can be obtained.
(1) According to the above embodiment, since the top hat type laser beam having a flat intensity in the target path TL is irradiated to the flying droplet D, the droplet D ejected from the nozzle N is The energy corresponding to the laser intensity P is continuously received from the time immediately after the ejection until the landing. Therefore, it is possible to quickly raise the temperature of the droplet D immediately after ejection to the target temperature, and to improve the drying efficiency of the droplet D. Since the laser intensity P is set so that the droplet D at the target temperature does not receive energy exceeding the heat of vaporization, it is possible to effectively prevent the droplet D from bumping.

  (2) In the target path TL of the above embodiment, the total energy of the first laser beam Le1 and the second laser beam Le2 is equivalent to the total amount of heat required to evaporate a desired amount of evaporation components. Since adjusted, the discharged droplet D can be landed in a desired dry state.

  (3) According to the above embodiment, the evaporation rate of the droplet D during flight is symmetric with respect to the ejection direction, so that the reaction force against the kinetic force of the evaporation component is canceled with respect to the droplet D. be able to. That is, it is difficult for the droplets D to be bent due to evaporation of the dispersion medium, and displacement of the landing positions of the droplets D can be suppressed. Moreover, even when the optical axes of the first laser beam Le1 and the second laser beam Le2 are shifted in the ejection direction of the droplet D, the evaporation rate in the flying droplet D is asymmetric with respect to the ejection direction. The flight area can be reduced. That is, it is possible to suppress the displacement of the landing position of the droplet D due to the displacement of the optical axis.

  (4) According to the above embodiment, the optical axes of the first laser beam Le1 and the second laser beam Le2 are inclined with respect to the arrangement direction of the nozzles N by the inclination angle θ. As a result, the first and second laser beams Le1 and Le2 can be irradiated to the droplets D ejected simultaneously from all the nozzles N of the ejection head 15. Therefore, it is possible to improve the drying efficiency for all the droplets D ejected at the same timing. In addition, when the inclination angle θ satisfies sin θ = 2r / Dx, there is no gap between the liquid droplets D ejected from the nozzle N adjacent to the laser light irradiation direction, so that all liquids When the laser beam is irradiated onto the droplet D, the horizontal irradiation range can be reduced, and the utilization efficiency of the laser beam can be improved.

  (5) In the laser irradiation part 31 of the said embodiment, the basic laser beam radiate | emitted from the laser light source 32 was branched to 1st laser beam Le1 and 2nd laser beam Le2 by arrange | positioning the half mirror 34. FIG. Thereby, a pair of laser beams irradiated to the droplet D can be generated by one laser light source 32, and the laser irradiation unit 31 can have a simple configuration.

  (6) Further, by arranging the first laser shaping part 40a and the second laser shaping part 40b between the half mirror 34 and the target path TL, the intensity distribution and the shape are converted and then the droplet D is irradiated. It is possible to suppress the diffraction of the first laser beam Le1 and the second laser beam Le2 until it is performed. That is, the intensity distribution in the target route TL can be realized with high accuracy.

  (7) According to the above embodiment, the first laser shaping unit 40a and the second laser shaping unit 40b align the cross-sectional shape in the Z direction of the first and second laser beams Le1 and Le2 with the flight space of the droplet D. It was. This ensures that the entire energy of each laser beam is input into the flight space. Therefore, the energy loss of each laser beam can be suppressed and guided to the target path TL, and the utilization efficiency of the laser beam can be improved.

In addition, you may change the said embodiment as follows.
In the first laser forming unit 40a and the second laser forming unit 40b of the above embodiment, cylindrical lenses 41a and 41b for aligning the cross-sectional shape of the laser light in the Z direction with the flight space are arranged, respectively, but by the DOE 42a and the DOE 42b The cylindrical lenses 41a and 41b may be omitted as long as the cross-sectional shape can be matched to the flight space.

  In the optical system of the laser irradiation unit 31 in the above embodiment, the first laser forming part 40a and the second laser forming part 40b are arranged on the target path TL side with respect to the half mirror 34. In addition to this, in converting the intensity distribution of the laser light applied to the droplet D from the Gaussian distribution to the above-described intensity distribution, the laser forming unit is arranged on the laser light source 32 side with respect to the half mirror 34. It may be.

  In the optical system of the laser irradiation unit 31 in the above embodiment, the optical axes of the first laser beam Le1 and the second laser beam Le2 are inclined by the inclination angle θ with respect to the arrangement direction of the nozzles N. Not limited to this, the optical axes of the first laser beam Le1 and the second laser beam Le2 may be aligned with the arrangement direction without being inclined with respect to the arrangement direction of the nozzles N. At this time, by sequentially ejecting the droplets D from the nozzles N of the ejection head 15 at different ejection timings, it is possible to irradiate all the droplets D with laser light.

-In the optical system of the laser irradiation part 31 in the said embodiment, the laser beam with equal laser intensity was irradiated with respect to the droplet D in flight from both sides. Not limited to this, for example, in a drawing pattern in which the landing position can be allowed to be displaced even when the flight bend is small or the flight bend occurs, such as when the weight of the droplet D is large and the flight speed is high. The droplet D may be irradiated with laser light converted into a desired intensity distribution only from one side, or laser light with different laser intensity may be irradiated from both sides. Even in such a case, the drying efficiency can be improved and the displacement of the landing position can be suppressed by the amount of the intensity distribution converted into the desired intensity distribution.

  In the optical system of the laser irradiation unit 31 in the above embodiment, the basic laser light Le emitted from one laser light source 32 is divided into the first laser light Le1 and the second laser light Le2 by the half mirror 34. A pair of laser beams irradiated from both sides of the droplet D in flight was generated. However, the present invention is not limited to this, and when irradiating laser light from both sides of the droplet D in flight, a laser light source that emits laser light having the same intensity to each of the pair of laser light may be used. According to this configuration, the half mirror 34 can be omitted.

  In the above-described embodiment, the laser light whose intensity distribution has been converted is applied to the flying droplet D from both sides. However, the intensity distribution of only one of the laser beams irradiated to the droplet D may be converted in order to suppress the displacement of the landing position of the droplet D. According to this, it is possible to improve the drying efficiency and suppress the displacement of the landing position by the amount corresponding to the conversion of the intensity distribution of one of the laser beams.

  In the above embodiment, the ejection head 15 has one nozzle row composed of the nozzles N. Not limited to this, a plurality of nozzle rows may be formed in the ejection head 15. At this time, the tilt angle θ of the optical axis of the laser light may be appropriately changed so that the first laser light Le1 and the second laser light Le2 are irradiated to all the droplets D ejected from the nozzle N.

  In the embodiment described above, the liquid droplet ejecting apparatus 10 that draws the metal wiring by ejecting the conductive ink Ik containing the conductive fine particles on the green sheet GS is embodied. However, the present invention is not limited to this, and may be applied to a pattern forming apparatus for other uses such as a pattern forming apparatus for drawing an insulating pattern, as long as the flying droplets are irradiated with laser light and dried.

  In the embodiment described above, the piezoelectric element driving type droplet discharge device 10 is embodied. However, the present invention is not limited to this, and from the viewpoint of ejecting droplets from the ejection head, the present invention may be embodied in a droplet ejection apparatus equipped with a resistance heating type or electrostatic drive type ejection head.

  -In the optical system of the laser irradiation part 31 of the said embodiment, it was set as the aspect with which a laser beam is irradiated with respect to the whole target path | route TL, but when irradiating a laser beam and evaporating a predetermined amount of evaporation components, The aspect which irradiates a laser beam partially with respect to the target path | route TL may be sufficient.

  In addition, the entire intensity distribution of the laser light applied to the droplet D was made flat. Not limited to this, in the case where a predetermined amount of evaporation component is evaporated by irradiating a droplet in flight with laser light, the intensity distribution in the region with the highest intensity in the target path TL is made flat. Also good. Even in such a configuration, it is possible to improve the drying efficiency while suppressing the bumping of the droplet D.

The perspective view which shows an example of the pattern formation apparatus concerning this invention. The perspective view which shows an ejection head. FIG. 3 is a main part cross-sectional view showing the inside of the ejection head. The schematic diagram which shows the dot pattern lattice of a green sheet. FIG. 3 is a schematic diagram illustrating an optical configuration of a droplet discharge device. The schematic diagram for demonstrating the relationship between a laser beam and a droplet. The graph which shows an example of intensity distribution of top hat type distribution. The schematic diagram when irradiating the laser beam of top hat type distribution from the both sides of a droplet. The schematic diagram when irradiating the laser beam of the Gaussian distribution from which the optical axis shifted | deviated from the both sides of the droplet.

Explanation of symbols

theta ... inclination angle, D ... liquid droplets, N ... nozzle, T ... grid point, theta ₁ ... inclination angle, Da ... outer circumferential edge, Db ... outer circumferential edge, DL ... dot pattern lattice, Dx ... nozzle pitch, Dy ... discharge pitch , PG ... platen gap, GS ... green sheet, Ik ... conductive ink, Le ... basic laser beam, PZ ... piezoelectric element, TL ... target path, GSa ... drawing surface, Le1 ... first laser beam, Le2 ... second laser. Light, Le10 ... Laser light, Le20 ... Laser light, 10 ... Droplet ejection device, 11 ... Base, 12 ... Stage, 13 ... Guide member, 14 ... Ink tank, 15 ... Discharge head, 16 ... Carriage, 17 ... Head Substrate, 17a ... connecting terminal, 20 ... head body, 20T ... supply tube, 21 ... nozzle plate, 21a ... nozzle forming surface, 22 ... cavity, 23 ... diaphragm, 31 ... laser irradiation part, 3 ... Laser light source, 32a ... YAG laser oscillator, 32b ... harmonic unit, 33 ... collimating lens, 34 ... half mirror, 35 ... reflection mirror, 36 ... reflection mirror, 37 ... reflection mirror, 38 ... reflection mirror, 39 ... reflection mirror , 40a ... first laser molding part, 40b ... second laser molding part, 41a ... cylindrical lens, 41b ... cylindrical lens, 42a ... DOE, 42b ... DOE.

Claims (4)

An ejection head for ejecting and flying liquid droplets containing an evaporation component and a pattern forming material from a nozzle toward a drawing object;
A laser irradiation unit that irradiates the droplets in flight with laser light to evaporate a predetermined amount of the evaporation component;
A pattern forming apparatus for forming a pattern by landing the droplet on the drawing object,
The laser irradiation unit is
A laser emitting part;
A laser forming portion for shaping the intensity distribution of the laser beam so that the intensity distribution of the laser beam is partially flat on the path between the nozzle and the position where the droplet lands;
A pattern forming apparatus comprising: The laser emitting unit emits a pair of laser beams,
The laser shaping portion shapes the intensity distribution of at least one of the pair of laser beams,
The pattern forming apparatus according to claim 1, wherein the laser irradiation unit irradiates the droplets with the pair of laser beams in a state of being opposed to each other across the path. The laser emitting unit emits a pair of laser beams having the same intensity on the path,
The pattern forming apparatus according to claim 2, wherein the laser shaping unit shapes the intensity distribution of each of the pair of laser beams. The pattern forming apparatus according to claim 2, wherein the laser emitting unit includes a branching unit that branches basic laser light from one laser light source into the pair of laser beams.

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