JP2009291684A - Method of forming functional film pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mitigate the resistance of a functional film pattern to be formed and achieve the formation of the functional film pattern in a single scanning process, in a method of forming the functional film pattern by an inkjet head. <P>SOLUTION: The longitudinal direction of the functional film pattern part 4 made up of straight lines is inclined at a specified angle θ to the scan direction of an inkjet head 110, the angle satisfying the formula: d<2rSINθ (wherein, "d" is a vertical component distance to the scan direction of a distance between the centers of adjacent liquid droplets, "r" is a radius after the impact of a liquid droplet, provided, however, that θ≠0). The inkjet head 110 which discharges a liquid droplet L containing functional microparticles B from a plurality of discharge orifices 111 arranged at specified intervals, is scanned on a substrate 1. Further, a functional film pattern P is formed on the functional film pattern part 4 made up of the straight lines are formed by the liquid droplets L which impact on a substrate 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming a functional film pattern using an ink jet head. Specifically, for example, a wiring pattern to a gate electrode, a source electrode, etc. on a thin film semiconductor is directly applied to a functional fine particle dispersion solution containing functional fine particles using an ink jet head. The present invention relates to a method of drawing and forming on a substrate.

  In recent years, light and thin flexible displays such as electronic paper and OLED (Organic Light Emitting Diode) have attracted attention. In these flexible displays, a large number of thin film transistors (TFTs) made of thin film semiconductors are used. That is, as shown in FIG. 7A, in the electronic paper, a thin film semiconductor is disposed between the film substrate and the display unit, and as shown in FIG. 7B, in the OLED, between the film substrate and the OLED. A thin film semiconductor is arranged.

  As a method of forming a wiring pattern to the gate electrode, source electrode, etc. on this thin film semiconductor, a functional film pattern is formed by drawing a functional fine particle dispersion containing functional fine particles directly on a substrate with an inkjet head. How to do is known.

  In the formation of functional film patterns using this inkjet head, the position and shape of the droplets landed on the substrate are accurately controlled in order to prevent defects such as disconnection and short-circuiting of the functional film pattern to be formed. There is a need to.

Patent Document 1 discloses a first arrangement step in which droplets containing conductive fine particles are arranged on a substrate at a wiring pitch that is not more than twice the diameter of a droplet immediately after being arranged and does not connect the droplets. There has been proposed a wiring forming method having a second arrangement step of arranging droplets on a substrate so as to fill between the droplets arranged in the first arrangement step.
JP2007-49186

  In a method of forming a functional film pattern by discharging droplets containing functional fine particles onto a substrate using an inkjet head, the functional film pattern of the formed wiring may have as low resistance as possible. desirable. The present inventor has found that the functional film pattern in which the longitudinal direction of the formed functional film pattern is parallel to the scanning direction of the inkjet head has a higher resistance than the pattern inclined with respect to the scanning direction. I found the characteristic to do. The present invention has been made based on this finding.

  In the technique disclosed in Patent Document 1, it is necessary to scan the ink jet head twice on the substrate in order to form the functional film pattern. In the second scanning step, it is necessary to land accurately between the droplets arranged in the first time.

  In view of the above circumstances, an object of the present invention is to reduce the resistance of a functional film pattern formed by using an ink jet head and to realize the formation of the functional film pattern in a single scanning process. Is.

In order to solve the above-described problems, the functional film pattern forming method of the present invention scans an ink-jet head that discharges droplets containing functional fine particles from a plurality of discharge ports arranged at regular intervals on a substrate. Then, in the functional film pattern forming method of forming a functional film pattern on the functional film pattern portion made of a straight line by droplets landed on the substrate, the longitudinal direction of the functional film pattern portion made of the straight line is inkjet The head is scanned at a predetermined angle θ satisfying the following formula with respect to the scanning direction of the head. d <2rSINθ (where d is the vertical component distance of the distance between the centers of adjacent droplets with respect to the scanning direction, and r is the radius after the droplets have landed, where θ ≠ 0).
Here, the “constant interval” means that the centers of the adjacent discharge ports are a constant interval. The above “scanning on the substrate” means that the inkjet head is scanned substantially parallel to the substrate surface. The “landed droplet” does not mean a droplet immediately after landing, but a droplet whose shape, size, position, etc. are substantially constant after landing. The above-mentioned “consisting of straight lines” means not including a curved line, and is not limited to a single straight line consisting of one direction, and a single straight line or a plurality of straight lines that are bent at a predetermined angle in the middle are predetermined. Including the state of crossing at an angle. The “functional film pattern portion” means a portion where a functional film is formed on a substrate. The “longitudinal direction of the functional film pattern portion” means a direction in which the functional film pattern formed of a straight line extends.

  According to the method for forming a functional film pattern of the present invention, the longitudinal direction of the functional film pattern portion formed of a straight line is tilted at a predetermined angle θ (provided that θ ≠ 0) with respect to the scanning direction of the inkjet head. In order to scan the inkjet head, the functional film pattern to be formed can have a lower resistance than the functional film pattern in which the longitudinal direction of the functional film pattern portion formed in a straight line is parallel to the scanning direction. In addition, the predetermined angle θ, the vertical component distance d with respect to the scanning direction of the distance between the centers of adjacent droplets, and the radius r after landing of the droplets should be set so as to satisfy d <2rSINθ. As a result, adjacent droplets after landing overlap, so that the functional film pattern can be formed without breaking by scanning the inkjet head once on the substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the substrate used for the functional film pattern forming method of the present invention will be described. FIG. 1 is a schematic configuration diagram of a substrate used in the functional film pattern forming method of the present invention, and FIG. 2 is an enlarged view of a main part of the substrate used in the functional film pattern forming method of the present invention. As shown in FIG. 1, in this embodiment, a glass substrate 1 which is an example of a substrate has a functional film wiring pattern region 2 indicated by an outermost frame indicated by a broken line in the figure, and this functional film wiring. The pattern region 2 is composed of a plurality of substantially lattice-like single cells 3 as an example. As shown in FIG. 2, the single cell 3 is provided with a thin film semiconductor, and a source line in the vertical direction in the drawing, a gate line in the horizontal direction in the drawing, and a drain line to the auxiliary capacitor. Moreover, each said line cross | intersects through the insulating layer which is not shown in figure.

  As described above, according to the present invention, it is possible to form a functional film pattern including a straight line that does not include a curve. In the present embodiment, the functional film pattern portion 4 is used as an example of a source line that is orthogonal to each other. However, the present invention is not limited to this.

  Next, the functional film pattern forming method of the present invention will be described. The functional film pattern forming method of the present invention comprises a drawing process and a baking process. First, the drawing process will be described. FIG. 3 is a schematic configuration diagram of a functional film pattern forming apparatus used in a drawing process of the functional film pattern forming method of the present invention. In FIG. 3, the directions of arrows X, Y, and Z are orthogonal to each other.

  The functional film pattern forming apparatus 100 includes a mounting table 101 on which a glass substrate 1 is mounted, and an inkjet head 110 that scans the mounting table 101 substantially parallel to the surface of the mounting table 101. Yes.

  The mounting table 101 can hold the glass substrate 1 so that the functional film pattern unit 4 forms a desired angle with respect to the scanning direction of the inkjet head 110, and is driven by a driving unit (not shown) in the Y direction in the figure. It has become freely movable.

  The inkjet head 110 includes a cartridge (not shown) filled with a functional fine particle dispersion solution containing the functional fine particles B, and is fixed in a straight line in a line for discharging droplets L made of the functional fine particle dispersion solution. It has a plurality of discharge ports 111 arranged at intervals. In addition, each ejection port 111 of the inkjet head includes a piezoelectric body (not shown), and the functional dispersion solution is ejected from the ejection port 111 at a predetermined frequency by vibrating the piezoelectric body. In addition, the inkjet head 110 is movable in the X direction in the figure by a driving means (not shown), and on the surface of the mounting table 101 in order to adjust the vertical component distance with respect to the scanning direction of the distance between the adjacent ejection ports 111. It is configured to be rotatable in the direction of arrow R around the vertical Z axis. In the present embodiment, the discharge ports 111 are arranged in a single line in a straight line at a constant interval in the inkjet head 110, but the present invention is not limited to this, and a plurality of straight lines are formed at a constant interval. It may be arranged in the inkjet head 110 in a shape.

  Specific examples of the functional fine particles B include Ag, Au, Cu, etc., which have good conductivity. However, since Au is expensive and Cu is easily oxidized, it is desirable to use Ag. Further, by using Ag having a low melting point as the functional fine particles, it can be applied to a resin substrate having a lower heat resistant temperature than that of the glass substrate 1. The particle diameter of the functional fine particles is 1-1000 nm, preferably 1-100 nm, more preferably 1-10 nm.

  Next, the functional film pattern forming method of the present invention will be described in detail. FIG. 4 shows a drawing process of the functional film pattern forming method of the present invention. In FIG. 4, for ease of understanding, only a part of the glass substrate 1 is shown, and the mounting table 101 and the inkjet head 110 are omitted.

  In the drawing process of the droplet L of the functional film pattern forming method of the present invention, as shown in the left diagram of FIG. 4, the functional film pattern portion 4 is in the scanning direction of the inkjet head 110 (the direction of arrow A in the figure). On the other hand, the glass substrate 1 is mounted on the mounting table 101 so as to be inclined by an angle θ. Thereby, the functional film pattern P to be formed does not have the functional pattern portion 4 parallel to the scanning direction (the direction of arrow A in the figure), and the resistance of the functional film pattern P to be formed is The resistance is lower than that of the functional film pattern P formed in parallel to the direction of arrow A in the figure. Here, the angle θ is determined so that no part of the functional film pattern portion 4 formed of a straight line is parallel to the scanning direction. In many cases, the functional film pattern is formed by a linear pattern, and particularly, there are many patterns formed in a lattice pattern as shown in FIGS. 7A and 7B. It is effective.

  Next, droplets L made of a functional fine particle dispersion solution are ejected from the ejection port 111 of the inkjet head 110, and the inkjet head 110 is scanned on the glass substrate 1 (in the direction of arrow A in the figure).

  After scanning on the glass substrate 1 of the inkjet head 110, the droplet L is landed on the functional film pattern portion 4 as shown in the right figure of FIG. The centers of adjacent droplets L are a and b, and the radius of the droplet L after landing on the functional film pattern portion 4 is r.

  Here, in the drawing process of the functional film pattern forming method of the present invention, when the vertical component distance d with respect to the scanning direction of the center distance S between the centers a and b of the adjacent droplets L after landing is d. Satisfies the relational expression d <2rSINθ. Since the center-to-center distance S is d / SINθ, when this relational expression is satisfied, the center-to-center distance S is less than 2r, and adjacent droplets L after landing overlap. Therefore, in the functional film pattern forming method of the present invention, it is not necessary to perform the second scanning for filling between adjacent droplets after landing. The determination of the vertical component distance d with respect to the scanning direction of the center distance S will be described later.

  Here, when a pattern having a predetermined width and thickness is drawn on the functional film pattern portion 4 using the droplet L without disconnection or short circuit, the adjacent liquid is used to make the characteristics after drawing uniform. The center-to-center distance S of the droplet L needs to be substantially uniform in the functional film pattern P that is a straight line. Here, the radius r of the droplet L after landing is determined by the viscosity of the droplet L, the surface tension, the wettability of the functional film pattern portion 4, the droplet discharge speed, and the like.

  The center-to-center distance S between adjacent droplets L is determined by the inclination of the inkjet head, as will be described later. FIG. 5 is a diagram showing a drawing state by the droplet L after landing. As described above, since the inkjet head 110 is configured to be rotatable in the direction of the arrow R about the Z axis perpendicular to the surface of the mounting table 101 (see FIG. 1), after landing on the functional film pattern forming unit 4 As shown in FIG. 5, the drawing with the liquid droplet L can tilt the inkjet head 110 to change the vertical component distance (vertical direction in the figure) with respect to the scanning direction between the ejection ports 111. That is, when the center-to-center distance S between the adjacent droplets L is equal to twice the radius r of the droplet L after landing, wavy line drawing (center of FIG. 5), and when small, straight line drawing (left of FIG. 5) ), If large, the drawing does not form a line (right in FIG. 5). Accordingly, it is necessary that the adjacent droplets L after landing in a single scanning process overlap to satisfy S <2r, which is a straight line drawing (left in FIG. 5).

  Here, referring again to FIG. 4, the vertical component distance d with respect to the scanning direction of the center-to-center distance S of the adjacent droplets L is the angle θ from the shape of the functional film pattern portion 4, and the droplet L By determining the radius r from the characteristics or the like, it is determined so as to satisfy the above-mentioned d <2rSINθ (where θ ≠ 0).

  In the conventional method, in the case of drawing a portion parallel to the scanning direction of the functional film pattern portion 4, the scanning direction is equal to the center-to-center distance S in the non-parallel portion. Only the discharge port 111 that exists directly above the parallel part is discharged by controlling the vibration of the piezoelectric body.

  After the drawing is finished, the glass substrate 1 is subjected to a drying process at room temperature. Moreover, this drying process may be dried at room temperature, a hot plate, an electric furnace, or the like may be used, and is not particularly limited.

  Next, the firing step of the method for forming a functional film pattern of the present invention will be described. In the functional film pattern forming method of the present invention, a firing step is performed in order to land on the functional film pattern forming portion 4 on the drawn glass substrate and convert the droplet L into a functional film. Firing is performed by heating the droplets L that have been landed under the condition that the glass substrate 1 has a temperature lower than the heat resistance temperature of the glass substrate 1. There is no restriction | limiting in this baking method, You may carry out in an electric furnace and may use a heat ray.

  Examples of the heat treatment using heat rays include laser annealing using a laser beam to irradiate the landing droplet L with the laser beam to make it dense, flash lamp annealing using a xenon flash lamp as the heat ray, and the like. It is done.

  The laser light source used for laser annealing is not particularly limited, and examples thereof include a pulsed laser such as an excimer laser and a continuous wave laser (CW laser). A short wavelength pulse laser such as an excimer laser beam is preferable because the energy absorbed by the surface layer of the functional film is large and the energy reaching the substrate can be easily controlled. For the same reason, when a pulse laser is used, the pulse width is preferably as short as 100 ns or less, more preferably several tens ns or less.

  As described above, the functional film pattern P is formed on the functional film pattern forming portion 4 of the glass substrate 1.

  Therefore, according to the functional film pattern forming method of the present invention, the longitudinal direction of the functional film pattern portion 4 on the glass substrate 1 is inclined by a predetermined angle θ with respect to the scanning direction of the inkjet head 110, so Therefore, the vertical component distance d with respect to the scanning direction of the distance between the centers of the adjacent droplets L after landing can be lower than that of the functional film pattern P that is parallel to each other. By satisfying the relationship of d <2rSINθ with the radius r of L, the droplets L after landing overlap each other, so that the functional film pattern can be drawn by one scan.

  In the present embodiment, the substrate is described as the glass substrate 1, but is not limited to this, and includes a flexible substrate and the like.

  Next, the functional film pattern forming method of the present invention was verified by forming a functional film pattern using the functional film pattern forming apparatus 100 and the electric furnace of the present embodiment.

  In this example, the functional fine particles B were Ag nanoparticles having an average particle diameter of about 3 to 7 nm, and this Ag nanoparticle dispersion solution was used at a metal content of 58 wt% and a viscosity of 10 mPa · s. Further, as the glass substrate 1, a quartz glass substrate having orthogonal linear functional film pattern portions 4 was used.

(Example 1)
In the drawing process of the present invention, with respect to the scanning direction of the straight line shape of the functional film pattern section 4 inkjet head 110 perpendicular, the predetermined angle θ is such that the 45 ° ±, upper stage 101 mounting the quartz glass substrate The droplets of the Ag nanoparticle dispersion solution are ejected from the ejection port 111 of the inkjet head 110, the inkjet head 110 is scanned on the quartz glass substrate, and the droplet L is landed on the functional film wiring pattern portion 4. Draw by doing.

  The vertical component distance d with respect to the scanning direction of the distance between the centers of the adjacent droplets L after landing is such that the distance between the centers of the landed droplets L is that of the landed droplets L in the comparative example described later. It was set to 21 μm so as to be about 30 μm, which is equal to the center-to-center distance. Moreover, after drawing, the drying process was performed at room temperature.

  In the firing step, the film was placed in an electric furnace heated to 220 ° C., heat-treated in an air atmosphere for 60 minutes, and returned to the conductive film.

  The resistance result of the functional film pattern P formed in Example 1 will be described. The sheet resistance of the functional film pattern P having a width of 64 μm and a length of 16 mm inclined by 45 degrees with respect to the scanning direction is 0.206 Ω / sq, and is inclined by −45 degrees with respect to the scanning direction and has a width of 70 μm. The sheet resistance of the functional film pattern P having a length of 16 mm was 0.223 Ω / sq.

(Comparative example)
In the drawing process of the conventional method, the quartz glass substrate is placed on the mounting table 1 so that the orthogonal linear functional film pattern portions 4 have a direction perpendicular to and parallel to the scanning direction of the inkjet head 110. Placed on top. The vertical component distance d with respect to the scanning direction of the distance between the centers of the adjacent droplets L after landing is 30 μm. Further, in the drying process, the functional film pattern portion 4 in the direction parallel to the scanning direction is landed in one scan by controlling the frequency of the droplet L ejected from the ejection port 111 as described above. The drawing can be performed in which the adjacent droplets L that are adjacent to each other overlap each other, and the drying process is performed in a state in which the adjacent droplets L after landing do not overlap each other in a single scan in the direction perpendicular to the scanning direction. Since the scanning process was performed twice after the drying process and the drying process was performed again, the procedure was the same as in Example 1 except that a difference occurred in the history of the drying process.

  The resistance result of the functional film pattern P formed in the comparative example will be described. The sheet resistance of the functional film pattern P having a width of 100 μm and a length of 16 mm parallel to the scanning direction is 1.23 Ω / sq, and the functionality of the width of 73 μm and the length of 16 mm is perpendicular to the scanning direction. The sheet resistance of the film pattern P was 0.223Ω / sq.

  The shape observation based on the result of the comparative example will be described. 6A shows a cross section of the functional film pattern by SEM when parallel to the scanning direction of the comparative example, and FIG. 6B shows a cross section of the functional film pattern by SEM when perpendicular to the scanning direction of the comparative example. It is shown. The cross section indicates a cross section perpendicular to the longitudinal direction of each functional film pattern P. 6A and 6B show a cross section of the functional film pattern P after the firing step.

  As shown in FIGS. 6A and 6B, the particles of the functional film pattern P parallel to the scanning direction are larger and sparser than the particles of the functional film pattern P perpendicular to the scanning direction. Network is bad. On the other hand, the particles of the functional film pattern P perpendicular to the scanning direction are smaller and denser than the particles of the functional film pattern P parallel to the scanning direction, and a network of particles is good.

  From the results of Example 1 and Comparative Example, the sheet resistance value of the functional film pattern P in each orthogonal direction can be obtained by tilting the orthogonal functional film pattern forming portion 4 by the functional film pattern forming method of the present invention. It was found that the resistance was lower than the sheet resistance of the functional film pattern P parallel to the scanning direction when the functional film pattern forming portion 4 was not tilted. It was also found that the sheet resistance value of the functional pattern P in each direction orthogonal to each other has little variation and uniform characteristics.

Schematic configuration diagram of a substrate used in the functional film pattern forming method of the present invention The principal part enlarged view of the board | substrate used for the functional film pattern formation method of this invention Schematic configuration diagram of a functional film pattern forming apparatus used in the drawing process of the functional film pattern forming method of the present invention The figure which shows the drawing process of the functional film pattern formation method of this invention The figure which shows the state of drawing with the droplet after landing Section of functional film pattern by SEM when parallel to scanning direction of comparative example Section of functional film pattern by SEM when perpendicular to scanning direction of comparative example Diagram showing the placement of thin film semiconductors in electronic paper The figure which shows arrangement | positioning of the thin film semiconductor in OLED

Explanation of symbols

B Functional fine particle L Droplet P Functional film pattern 1 Glass substrate 4 Functional film pattern part 110 Inkjet head 111 Discharge port

Claims (1)

A functional film comprising a straight line formed by scanning an ink jet head that discharges droplets containing functional fine particles from a plurality of discharge ports arranged at regular intervals on the substrate and landing on the substrate. In the functional film pattern forming method for forming the functional film pattern in the pattern portion,
A method of forming a functional film pattern, wherein the scanning is performed while tilting the longitudinal direction of the functional film pattern portion formed of the straight line at a predetermined angle θ satisfying the following formula with respect to the scanning direction of the inkjet head.
d <2rSINθ
(In the formula, d is a vertical component distance of the distance between the centers of adjacent droplets with respect to the scanning direction, and r is a radius after landing of the droplets, where θ ≠ 0.)