JPH09174273A - Liquid crystal mask laser marker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable clear marking on a metal which is difficult to execute by a conventional crystal mask laser marker. SOLUTION: A liquid crystal mask 104 is irradiated with a laser beam 102a taken out of a solid-state laser generator 101, a light source for a liquid crystal mask laser marker 100. A laser beam containing a pattern for marking with a laser beam 102b that passed through the liquid crystal mask 104 is transmitted through a polarizing beam splitter 106. An image on the liquid crystal mask 104 is formed by a lens 103d on the lens 103e arranged immediately before a laser amplifier 108, is made incident on the laser amplifier 108 and is amplified. The amplified laser beam 102f is reflected by a reflection mirror 111 and emitted to a work 112 made of metal. Then, a lens 103f functions as an image- forming lens, so that the image on the liquid crystal mask 104 reduced and projected on the lens 103e is formed on the work 112.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser marker which is a device for marking with laser light.

[0002]

2. Description of the Related Art Generally, a laser marker for irradiating a liquid crystal mask with a laser beam to transfer a pattern to a work and marking the same is called a liquid crystal mask type laser marker.
Conventionally, an IC package has been mainly used as a work. That is, by irradiating the surface of the IC package with the patterned laser light displayed on the liquid crystal mask, the temperature of the surface rises and the color changes, and the pattern is marked. As a light source in the conventional liquid crystal mask type laser marker, for example, a flash lamp-excited solid-state laser oscillator has been used.

Further, in the liquid crystal mask type laser marker, a marking pattern is formed by an aggregate of pixels in the liquid crystal mask. By applying a voltage to pixels other than the pixels that form the marking pattern (that is, pixels that form the background), the polarization direction of the laser light that has passed through those pixels passes through the pixels that form the marking pattern. It can be shifted by 90 degrees with respect to the laser light, and by separating these by a polarization beam splitter, the work is irradiated with the patterned laser light and marking is performed.

The liquid crystal mask type laser marker is described, for example, in Japanese Patent Laid-Open No. 4-200989.

[0005]

Conventionally, a liquid crystal mask type laser marker using a flash lamp pumped solid-state laser oscillator as a light source is a main object of marking.
Although the C package is made of resin, it is difficult to mark a material having a high melting point or high thermal conductivity such as metal or silicon.

Therefore, when a Q switch (hereinafter referred to as an EOQ switch) using the electro-optic effect is inserted into the resonator of the solid-state laser oscillator and operated, the pulse width of the lasing laser beam is changed. It is several tens of ns, which is 3 to 4 digits shorter than the conventional one. According to this, since the temperature of the material rises above the melting point before the heat of the laser light is conducted and diffused, it is considered possible to mark even metal or the like. However, it has been found that the following two problems occur.

First, the peak power of laser light oscillated from an EOQ-switched solid-state laser oscillator is several MW.
And, it is 2-3 orders of magnitude higher than that of a normal solid-state laser oscillator.
Therefore, the liquid crystal mask is likely to be deteriorated by the irradiation of the laser beam and may not be used for a long period of time.

Secondly, when marking is performed by the conventional pattern display method, the background of the marking pattern may be discolored, and the marking pattern may be difficult to recognize.

An object of the present invention is to provide a liquid crystal mask type laser marker capable of clearly marking a metal or the like, which is difficult with conventional liquid crystal mask type laser marker marking, and in which the liquid crystal mask is less likely to deteriorate.

[0010]

In order to achieve the above object, a laser light generator which is a light source of a liquid crystal mask type laser marker includes an EOQ switch, and the laser light generator includes an oscillator and an amplifier. The liquid crystal mask is arranged between the oscillator and the amplifier.

In order to make clear marking, the liquid crystal mask is driven in a mode in which a voltage is applied to the pixels forming the display pattern.

By configuring the laser light generator, which is the light source of the liquid crystal mask type laser marker, with the oscillator and the amplifier,
Even if a laser beam having a low peak power is oscillated from the oscillator, the peak power can be sufficiently increased so that a metal or the like can be marked by the amplifier. Therefore,
By disposing the liquid crystal mask between the oscillator and the amplifier, the peak power of the laser light with which the liquid crystal mask is irradiated can be sufficiently lowered.

Further, by driving the liquid crystal mask in a mode in which a voltage is applied to the pixels forming the display pattern, it is possible to prevent the laser light passing through the gaps between the pixels from irradiating the work. Note that a pixel in a liquid crystal mask refers to an intersection of two orthogonal transparent electrodes (scanning line and signal line). According to this, for the reasons explained below,
It was found that the background of the pattern did not discolor.

The pulse width of laser light oscillated by applying an EOQ switch to a solid-state laser oscillator is generally several tens of ns, which is 3 to 4 as compared with a normal flash lamp pumped solid-state laser. The order of magnitude is shortened, and as described above, all the energy of the laser light is injected within a sufficiently short time. That is, even if the area of the work irradiated with the laser beam is small, the temperature of the part rapidly increases and the color changes. Therefore, if the liquid crystal mask is driven in the same manner as in the conventional case, the laser light is irradiated onto a small area corresponding to the gap between the pixels on the work, so that the temperature of the part is raised and the color is changed. it was thought. On the other hand, in the present invention, in particular, since the liquid crystal is driven as described above, it is possible to prevent the work from being irradiated with the laser light that has passed through the gaps between the pixels, and the pixels forming the marking pattern on the work. Other parts will not be discolored.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a liquid crystal mask type laser marker 100 which is an embodiment of the present invention, and FIG. 2 is a block diagram of a solid-state laser oscillator 101 used in the liquid crystal mask type laser marker 100.

In the liquid crystal mask type laser marker 100, a solid-state laser oscillator 101 is used for a laser device which is a light source. The laser light 102a extracted from the solid-state laser oscillator 101 has its beam cross section enlarged by the lenses 103a and 103b and irradiates the liquid crystal mask 104.
A marking pattern is formed on the laser beam 102b that has passed through the liquid crystal mask 104. That is,
With the pattern laser light and the other laser light,
This means that the polarization directions are offset from each other by 90 degrees. The laser light 102b passes through the wave plate 105 and enters the polarization beam splitter 106. In the wave plate 105, since the polarization direction of the laser light passing therethrough can be rotated, the patterned laser light passes through the polarization beam splitter 106, and the other laser light is polarized light splitter 106.
The polarization direction of each laser beam is adjusted so that the laser beam is reflected. As a result, the laser light 102d unnecessary for marking
Is reflected by the polarization beam splitter 106 and the stopper 1
You can stop at 07. The laser beam 102e on which the marking pattern is formed has its beam cross section reduced by the lenses 103d and 103e and is incident on the laser amplifier 108 surrounded by a dotted line in the drawing. Lens 103
d functions as an image forming optical system that constitutes the present invention, whereby an image on the liquid crystal mask 104 is formed on a lens 103e arranged immediately before the laser amplifier 108. On the other hand, the laser light incident on the laser amplifier 108 is amplified by passing through the solid-state laser medium 109, so that the image on the liquid crystal mask 104 is amplified as it is. A slab-shaped solid-state laser medium is used as the solid-state laser medium 109, which is excited by flash lamps 110a and 110b for excitation.

Further, as will be described below, the slab-shaped solid-state laser medium does not change the direction in which the laser light traveling inside is emitted from the solid-state laser medium even when heated. That is, as can be seen from the cross-sectional view of the solid-state laser medium 109 shown in FIG. 3, the laser light traveling inside travels in a zigzag manner repeatedly along the optical axis shown by the dotted line. As a result, the influence of the non-uniform temperature distribution generated inside the solid-state laser medium 109 on the laser light is canceled, the thermal lens effect is not received, and the direction in which the laser light propagates does not change. The laser light 102f is reflected by the reflecting mirror 111, passes through the lens 103f, and is irradiated onto the metal work 112. The lens 103f functions as an imaging lens, and the image on the liquid crystal mask 104 that is reduced and projected onto the lens 103e is the work 112.
Is imaged. As a result, the work 112 is irradiated with the patterned laser light displayed by the liquid crystal mask 104, and the pattern is marked. Since the thermal lens effect does not occur in the solid-state laser medium 109, an image on the lens 103e formed on the work 112 by the lens 103f (that is, an image on the liquid crystal mask 104 on which a marking pattern is displayed) is formed. There is no blur.

Next, the structure of the solid-state laser oscillator 101 in the liquid crystal mask type laser marker will be described with reference to FIG. In the solid-state laser oscillator 101, the solid-state laser medium 12
A YAG crystal is used as 2, and a total reflection mirror 123 is used.
And the output mirror 124 constitute a resonator. The solid-state laser medium 122 is a flash lamp 125 which is an excitation light source.
It is excited by a and 125b. EO in the resonator
The switch 127 and the polarization beam splitter 126 are arranged. The flash lamps 125a and 125b emit light,
The EO switch 127 is operated after the solid-state laser medium 122 is excited and energy is sufficiently accumulated. As a result, a high peak power pulsed laser light 102a called a giant pulse is extracted from the output mirror 124 to the outside of the resonator.

In this embodiment, the solid-state laser oscillator 101 is used.
In general, the EOQ switch 127 is used. The EOQ switch 127 is generally made of a transparent crystal, but since it absorbs about 3% of the laser light, if the average output of the laser becomes high, the temperature will increase. It may rise and stop functioning normally. However, since the laser device in the liquid crystal mask type laser marker of the present invention is composed of the laser oscillator and the laser amplifier, even if the laser oscillator is operated at a low output such that the EOQ switch continues to operate normally. The laser amplifier can increase the laser light with a power sufficient for marking.

In the present embodiment, the work 112 is made of metal, but not only is it difficult to mark with the conventional liquid crystal mask type laser marker, but even if the EOQ switch is applied to the solid state laser oscillator of the light source. However, the problem is that the marking pattern is difficult to recognize.
This will be described below.

The difference between the conventional marking method and the marking method using the liquid crystal mask type laser marker of the present invention will be described with reference to FIGS. Here, the case where a cross-shaped pattern is marked using a liquid crystal mask having 5 × 5 pixels is taken as an example. FIG. 4 shows that the conventional liquid crystal mask type laser marker is used to drive the liquid crystal mask in the same manner as the conventional method.
The present invention relates to a case where a resin such as an IC package is marked as a work. FIG. 5 shows an EQ switch-operated solid-state laser oscillator 1 used in the present invention shown in FIG.
No. 01 is used to drive a liquid crystal mask in the same manner as in the conventional method, and a metal is marked as a work. FIG. 6 shows the EO used in the present invention shown in FIG.
The present invention relates to a case where a liquid crystal mask is driven by the method of the present invention by using a solid-state laser oscillator 101 of Q switch operation to mark a metal as a work. FIG.
6 to 6, (a) is a display mode of a liquid crystal mask,
(B) shows the temperature distribution on the line corresponding to X and Y shown in (a) of the laser-irradiated work, and (c) shows the pattern marked on the work. Incidentally, in the display mode of the liquid crystal mask shown in each figure (a), a voltage is applied to the pixel indicated by diagonal lines, and the laser light passing therethrough is different from the laser light passing through other portions, The polarization direction is shifted by 90 degrees.

Conventionally, as shown in FIG. 4A, a liquid crystal mask is used to apply a voltage to pixels in the background (pixels indicated by diagonal lines) other than the cross-shaped pattern, so that the laser light passing through these is applied. It was separated so that the work was not irradiated. According to this, in the work, the pixels that form the cross pattern and the laser light that has passed through the gaps between the pixels are applied to the work. As a result, regarding the temperature distribution of the work, as shown in FIG. 4B, on the line corresponding to X on the liquid crystal mask, the laser light is laterally connected and irradiated, and the color change indicated by the dotted line occurs. Exceeds the threshold temperature.
Therefore, as shown in FIG. 4 (c), the marking is performed in the form of a line connected in the lateral direction. However, on the line corresponding to Y on the liquid crystal mask, even if the laser light that has passed through the gaps between pixels that are not to be marked is irradiated, heat will be conducted and escape to the adjacent region where the laser light is not irradiated. As shown in FIG. 4B, it is difficult to exceed the threshold temperature at which discoloration occurs, and marking is not performed.

However, if the liquid crystal mask is marked with the conventional driving method using the liquid crystal mask type laser marker of the present invention shown in FIG. 1, the temperature of the work on the line corresponding to Y on the liquid crystal mask. Distribution is Figure 5
As shown in (b), the threshold for discoloration is exceeded. That is, even in the portion irradiated with the laser light passing through the gap between the pixels, the energy of the irradiated laser light is injected into the work in a short time with a pulse width of several tens of nanoseconds, so that heat is conducted in the portion. The temperature rises rapidly before it diffuses. That is, the pulse width of the laser light oscillated by the EOQ switch operation is 4 times as long as the pulse width of the laser light oscillated from the normal flash lamp pumped solid-state laser.
This is because the order of magnitude is shortened. Therefore, even in the portion corresponding to the gap between the pixels in the background of the marked pattern, the temperature exceeds the threshold value and discolors.
As shown in (c), lines corresponding to the gaps between pixels are marked even in the background of the pattern, which makes it difficult to recognize the pattern to be marked.

On the other hand, if the liquid crystal mask is driven by the driving method in this embodiment, as shown in FIG.
A voltage is applied to the pixels that make up the pattern to be marked, and only the laser light that has passed through these pixels is applied to the work.Therefore, the work should not be irradiated with the laser light that has passed through the gaps between the pixels in the background of the pattern to be marked. become. Therefore, as shown in FIG.
The pattern is marked as a set of pixels, but the extra line as shown in FIG. 5C is not marked, and the marked pattern is easy to recognize.

[0026]

According to the present invention, even if a laser beam of high peak power is generated by using an EOQ switch, the liquid crystal mask is not damaged and the liquid crystal mask is used for a sufficiently long period of time. be able to.

Further, particularly when the liquid crystal mask is driven by the method of the present invention, the laser light passing through the gaps between the pixels in the liquid crystal mask does not irradiate the work, so that the background of the marking pattern is not discolored and the pattern is not changed. Can be easily recognized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a liquid crystal mask type laser marker of the present invention.

FIG. 2 is an explanatory diagram of a solid-state laser oscillator in the liquid crystal mask type laser marker of the present invention.

FIG. 3 is an explanatory view showing an optical axis of a solid-state laser medium in the liquid crystal mask type laser marker of the present invention.

FIG. 4 is an explanatory diagram of marking with a conventional liquid crystal mask type laser marker.

FIG. 5 is an explanatory diagram of marking with a conventional liquid crystal mask type laser marker.

FIG. 6 is an explanatory diagram of marking with a liquid crystal mask type laser marker of the present invention.

[Explanation of symbols]

100 ... Liquid crystal mask type laser marker, 101 ... Solid-state laser oscillator, 102a, 102b, 102c, 102d,
102e, 102f ... Laser light, 103a, 103b,
103c, 103d, 103e, 103f ... Lens, 1
04 ... Liquid crystal mask, 105 ... Wave plate, 106 ... Polarization beam splitter, 107 ... Stopper, 108 ... Laser amplifier, 109 ... Solid-state laser medium, 110a, 110b ... Flash lamp, 111 ... Reflector, 112 ... Work.

Claims (2)

[Claims] 1. In a liquid crystal mask type laser marker for irradiating a laser beam from a laser beam generator onto a liquid crystal mask and transferring a pattern displayed on the liquid crystal mask onto a work, the laser beam generator uses an electro-optical effect. And a liquid crystal mask type laser marker, wherein the laser light generator is composed of an oscillator and an amplifier, and the liquid crystal mask is arranged between the oscillator and the amplifier. 2. A liquid crystal mask type laser marker for irradiating a liquid crystal mask with a laser beam from a laser beam generator to transfer a pattern displayed on the liquid crystal mask onto a work, wherein the laser beam generator uses an electro-optical effect. The liquid crystal mask type laser marker is characterized in that the liquid crystal mask is driven in a mode in which a voltage is applied to pixels forming a display pattern.