JP2014149316A - Method for manufacturing retardation plate and retardation plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a retardation plate preventing fractures or cracks from being generated in a cut portion when obtaining the retardation plate divided into chips by dicing or scribing a glass substrate.SOLUTION: The method for manufacturing a retardation plate having a birefringence area in a glass substrate and/or on a glass substrate comprises: (a) preparing a glass substrate having first and second surfaces; (b) scanning laser beams having modulated output in a first direction parallel to the first or second surface in the glass substrate and/or on the glass substrate to form a birefringence area having a tensile stress portion and a compressive stress portion in the first direction in the glass substrate and/or on the glass substrate; and (c) cutting the glass substrate so as to pass the compressive stress portion of the birefringence area.

Description

  The present invention relates to a retardation plate manufacturing method and a retardation plate.

  A retardation plate (for example, a half-wave plate or a quarter-wave plate) capable of controlling the phase and polarization of light is used in various optical devices including a Blu-ray optical pickup device. .

  Until now, for such a retardation plate, an organic polymer film having refractive index anisotropy, that is, birefringence, a uniaxial crystal, or the like has been used.

  However, the conventional organic polymer film has a defect that it is inferior in moisture resistance and high temperature stability. In addition, quartz has the disadvantages that the material itself is expensive and that the processing costs such as cutting into an accurate thickness and polishing are high. Therefore, a method for producing a retardation plate using a glass substrate excellent in moisture resistance, high temperature stability, and low cost has been proposed. For example, Patent Document 1 discloses a method of forming a band-shaped birefringence region in a glass substrate using laser light.

International Publication No. WO2008 / 126828

  In the method of Patent Document 1 described above, a belt-like birefringence region can be formed in a glass substrate by irradiating the glass substrate with laser light and scanning it.

  However, in order to actually provide a glass substrate having such a birefringent region as a retardation plate product, the glass substrate is cut (diced or scribed) so as to cross the band-shaped birefringent region. It is necessary to chip the glass substrate.

  Here, in the case of the glass substrate obtained by the method of Patent Document 1 described above, the band-shaped birefringence region is generated due to the tensile stress due to the thermal effect of laser light irradiation. When the glass substrate is cut so as to cross the birefringent region, there may be a problem that a crack occurs in the cut portion or the glass substrate breaks.

  The present invention has been made in view of such a background, and in the present invention, when a retardation plate obtained by dicing or scribing a glass substrate to obtain a chip is obtained, cracks or cracks are generated in the cut portion. An object of the present invention is to provide a manufacturing method of a difficult retardation plate. It is another object of the present invention to provide a phase difference plate with improved strength at the cut portion.

In the present invention,
A method for producing a retardation plate having a birefringent region in and / or on a glass substrate,
(A) preparing a glass substrate having first and second surfaces;
(B) scanning the output-modulated laser beam in the glass substrate and / or on the glass substrate in a first direction parallel to the first or second surface; Forming a birefringent region having a tensile stress portion and a compressive stress portion along the direction of 1;
(C) A method for producing a retardation plate is provided, wherein the glass substrate is cut so as to pass through a compressive stress portion of the birefringent region.

Here, in the manufacturing method according to the present invention,
In (b), in the birefringent region, there are a first compressive stress portion and a second compressive stress portion along the first direction, and a tensile stress portion between both compressive stress portions. Formed,
In (c), the glass substrate is cut at a first cutting position and a second cutting position, the first compressive stress portion is selected as the first cutting position, and a second cutting position The second compressive stress portion may be selected.

In the production method according to the present invention,
The output-modulated laser light has a portion where the laser output increases stepwise and / or a portion where the laser output decreases stepwise with respect to time,
The first compressive stress portion is generated by irradiating a laser beam whose laser output increases stepwise, and / or the second compressive stress portion is a laser whose laser output decreases stepwise. You may generate | occur | produce by irradiating light.

In the production method according to the present invention,
The output-modulated laser beam may have a repetitive waveform with a period τ.

In the production method according to the present invention,
The output modulated laser light includes a minimum value and a maximum value of a laser output,
One period τ of the output-modulated laser light may have a flat portion with respect to the minimum time and / or a flat portion with respect to the maximum time.

  In the manufacturing method according to the present invention, the minimum value may be a value other than zero.

  In the manufacturing method according to the present invention, the laser beam may be composed of two or more laser beams in which the focal points are arranged in a line.

Furthermore, in the present invention,
A phase difference plate having a birefringent region in and / or on a glass substrate,
The birefringent region extends along a first direction from a first end surface of the glass substrate to a second end surface;
The retardation plate in the birefringent region has a retardation distribution in a region of 500 μm along the first direction within ± 5%.

  Here, in the retardation plate according to the present invention, the birefringence region may have a retardation distribution within ± 5% in a region of 500 μm along a second direction perpendicular to the first direction.

  In the present invention, when a retardation plate obtained by dicing or scribing a glass substrate to obtain a chip is obtained, it is possible to provide a method for producing a retardation plate in which cracks and cracks are unlikely to occur at a cut portion. In addition, it is possible to provide a retardation plate in which the strength of the cut portion is improved.

It is the figure which showed roughly the method of manufacturing a birefringent area | region on the conventional glass substrate. An example of the stress distribution pattern in the complex refraction region obtained when scanning the output-modulated laser beam on the glass substrate is schematically shown corresponding to the output waveform of the laser beam and the laser beam scanning position of the glass substrate. It is a figure. Another example of the stress distribution form of the complex refraction region obtained when the output-modulated laser beam is scanned on the glass substrate is schematically shown in correspondence with the output waveform of the laser beam and the laser beam scanning position of the glass substrate. It is the figure shown in. It is the graph which showed roughly another example of the output waveform of a laser beam. It is the graph which showed roughly another example of the output waveform of a laser beam. It is the graph which showed roughly another example of the output waveform of a laser beam. It is the flowchart which showed roughly an example of the method of manufacturing the phase difference plate by this invention. It is the figure which showed schematically an example of the apparatus used when manufacturing the phase difference plate by this invention. FIG. 2 is a schematic top view (a) of a retardation plate according to the present invention and a schematic stress distribution diagram (b) in a birefringence region of the retardation plate. It is the figure which showed schematically an example of the structure of the optical pick-up apparatus. It is the graph which showed retardation distribution of the birefringence area | region pattern in the scanning direction of the laser beam of the glass substrate (before cutting) of Example 1. FIG. It is the graph which showed the retardation distribution of the birefringent area | region pattern in the direction perpendicular | vertical to the scanning direction of the laser beam of the glass substrate (before cutting) of Example 1. FIG. 3 is a graph showing a retardation distribution of a birefringent region in a scanning direction of laser light of the retardation plate of Example 1. FIG. 3 is a graph showing a retardation distribution of a birefringent region in a direction perpendicular to the laser beam scanning direction of the retardation plate of Example 1. FIG. It is an enlarged view of the part of the flat part Q2 in FIG. It is an enlarged view of the part of the flat part Q5 in FIG. 6 is a graph showing a retardation distribution of a birefringent region in a scanning direction of a laser beam of a retardation plate of Example 2. 6 is a graph showing a retardation distribution of a birefringent region in a direction perpendicular to the scanning direction of laser light of the retardation plate of Example 2. 6 is a graph showing retardation distribution of a birefringent region in the scanning direction of laser light of the retardation plate of Example 3. 6 is a graph showing retardation distribution of a birefringent region in a direction perpendicular to the scanning direction of laser light of the retardation plate of Example 3. 6 is a graph showing retardation distribution of a birefringent region in a scanning direction of laser light of a retardation plate of Example 4. 6 is a graph showing a retardation distribution of a birefringent region in a direction perpendicular to the laser beam scanning direction of the retardation plate of Example 4.

  The present invention will be described below.

  First, in order to better understand the characteristics of the present invention, the problems of the conventional method of manufacturing a retardation plate described in Patent Document 1 will be briefly described.

  In FIG. 1, the conceptual diagram of the manufacturing method of the phase difference plate described in patent document 1 is shown.

  As shown in FIG. 1, in this method, a laser beam 2 is irradiated onto a glass substrate 1 through a lens 3. By scanning the laser beam 2 along the Y direction in FIG. 1, the band-shaped birefringent region 4 can be formed in the glass substrate 1.

  However, in order to actually provide the glass substrate 1 having such a birefringent region 4 as a retardation plate product, the glass substrate 1 crosses the band-like birefringent region 4 (for example, along the X direction in FIG. 1). It is necessary to cut the glass substrate 1 (dicing or scribing) to make the glass substrate 1 into chips.

  However, in the glass substrate 1, the band-shaped birefringent region 4 is generated by a tensile stress due to the thermal effect of the irradiation of the laser beam 2, so that the glass substrate 1 crosses the band-shaped birefringent region of the glass substrate 1. When 1 is cut | disconnected, the problem that a crack generate | occur | produces in a cut part or the glass substrate 1 will break may arise.

  In order to avoid such a problem, it is conceivable that the output of the laser light applied to the glass substrate is modulated on / off in advance. In this case, the birefringence region is intermittently formed along the laser beam scanning direction (Y direction). A non-birefringence region is formed between the birefringence regions. Therefore, when cutting out the product of the retardation film, it is considered that the problem of cracks and cracks as described above can be reduced by dicing or scribing the glass substrate through the non-birefringent region. .

  However, in such a method, it is necessary to form a relatively long laser light non-irradiated region between the birefringent regions by sufficiently lengthening the time during which the laser light output is turned off. This is because the temperature of the glass substrate continues to rise until a certain period even after the output of the laser light is switched from on to off. On the other hand, when the time for which the output of the laser beam is turned off is insufficient, a heat-affected portion is generated even in the laser beam non-irradiated region, and a non-heat-affected portion cannot be sufficiently secured.

  However, it is necessary to manufacture a retardation plate as a product by cutting between non-thermally affected portions (that is, non-birefringent regions) in a region not irradiated with laser light. Therefore, in such a method, there is a problem that the size of the product becomes large and it is difficult to reduce the size of the product.

  In order to cope with the above problems, the inventors of the present application have made various studies on the relationship between the output waveform of the laser beam and the form of the birefringent region caused thereby. As a result, when a laser beam whose output is modulated is used, the birefringent region to be formed is found to have a tensile stress portion and a compressive stress portion along the scanning direction of the laser beam. It came to.

That is, in the present invention,
A method for producing a retardation plate having a birefringent region in and / or on a glass substrate,
(A) preparing a glass substrate having first and second surfaces;
(B) scanning the output-modulated laser beam in the glass substrate and / or on the glass substrate in a first direction parallel to the first or second surface; Forming a birefringent region having a tensile stress portion and a compressive stress portion along the direction of 1;
(C) A method for producing a retardation plate is provided, wherein the glass substrate is cut so as to pass through a compressive stress portion of the birefringent region.

  FIG. 2 shows an example of the stress distribution form in the complex refraction region obtained when the output-modulated laser beam is scanned on the glass substrate, corresponding to the output waveform of the laser beam and the laser beam scanning position of the glass substrate. Schematically.

In the example of FIG. 2, as shown at the top of the figure, the laser light output waveform 125A is composed of a repetitive waveform of period τ, and the vertical axis laser output is stepped with respect to the time on the horizontal axis. Repeat increasing and decreasing. The one period tau, composed of the period _{t 1} the output is the minimum value _{P min,} and the period _{t 2} which output is maximized _{P max.} Note that the minimum value P _min is a value larger than 0 (zero), and is a value at which the temperature of the irradiated portion is equal to or higher than the strain point of the glass. Further, the laser output on the vertical axis is normalized so that the maximum value P _max is 100%.

Here, in the output waveform 125A of FIG. 2, the relationship between the maximum value P _max and the minimum value P _min is not particularly limited. For example, the minimum value P _min may be in the range of 50% to 75% of the maximum value P _max .

In the example of FIG. 2, the minimum value _{P min} period _{t 1} and time _{t 2} of the maximum value _{P max} of is are equal, the minimum value _{P min} and duration of the maximum value may be different.

  When a laser beam having such an output waveform 125A is used, a birefringent region pattern 150 is formed on the glass substrate 110 along the scanning direction (Y direction) as shown in the middle of FIG. The

Here, in this example, the laser beam is always scanned with an output equal to or higher than the minimum value P _min , and this value is a value other than zero and the temperature of the irradiated portion is equal to or higher than the strain point of the glass. A non-birefringent region is not formed, and a linear pattern 150 including only a birefringent region is formed at the scanning position.

  Further, the absolute value of stress at each position along the broken line L1 of the pattern 150 shows a stress distribution as shown in the lowermost part of FIG. That is, the stress distribution is a stress distribution in which a flat portion B1 of the first tensile stress, a peak portion P1 of the first compressive stress, a flat portion B2 of the second tensile stress, and a peak portion P2 of the second compressive stress are repeated. Arise.

  Such a stress distribution can be obtained from the retardation distribution obtained from the birefringence measurement with a polarizing microscope, the fast axis direction distribution, the photoelastic constant of the glass, and the thickness of the birefringence region.

Here, the first compressive stress peak P1 is generated corresponding to the portion 126A where the output rapidly increases from P _min to P _max in the output waveform 125A of the laser beam, and the second compressive stress peak P2 is the laser beam. In the output waveform 125A, the output is generated corresponding to the portion 126B where the output drops rapidly from _Pmax to _Pmin . On the other hand, the flat portion B1 of the first tensile stress is generated in the region of the glass substrate 110 corresponding to the time when the output is P _min . Further, the flat portion B2 of the second tensile stress is generated in the region of the glass substrate 110 corresponding to the time between the peaks P1 and P2 and when the output becomes _Pmax . In a normal case, the flat portion B2 of the second tensile stress has a larger stress value than the flat portion B1 of the first tensile stress.

  In FIG. 2, it should be noted that the positional relationship among the laser light output waveform 125 </ b> A, the birefringent region pattern 150, and the stress distribution is shown approximately for the sake of clarity.

  For example, since there is actually a delay in the heat input of the laser beam, the first compressive stress peak P1 of the pattern 150 in the birefringent region is strictly more time than the rapidly increasing portion 126A of the output waveform 125A of the laser beam. The second compression stress peak P2 in the stress distribution is strictly delayed from the sudden drop portion 126B of the laser light output waveform 125A. (In the right side of FIG. 2). The same applies to the flat portions B1 and B2 of tensile stress.

  It has been found by the present inventors that the pattern 150 of the birefringent region obtained when the output-modulated laser beam is used shows a stress distribution as shown in FIG. 2 in most cases.

  Accordingly, when the retardation plate is manufactured by dicing or scribing the glass substrate 110, the glass substrate 110 is cut at a portion where the compressive stress in the pattern 150 of the birefringence region remains, and at the time of cutting. It is possible to significantly suppress the occurrence of cracks and cracks at the cut portion.

  For example, in the example of FIG. 2, the vicinity of the first compressive stress peak P1 (any position in the region R1) is selected as the first cutting part C1, and the second cutting part C2 is the second cutting part C2. What is necessary is just to select the vicinity (any position in area | region R2) of the compressive-stress peak P2. Thereby, it can suppress significantly that a crack and a crack arise in a cut part. In particular, as the first cutting part C1, a position within the region R1 and earlier in time than the top position of the compressive stress peak P1 (left side in FIG. 2) is selected, and as the second cutting part C2, the position within R2 In addition, it is particularly preferable to select a position (right side in FIG. 2) that is delayed in time from the apex position of the compressive stress peak P2 in terms of cracking at the time of cutting and crack suppression.

  Here, the region R1 includes a flat portion B1 of the tensile stress formed “first” in time in the pattern 150 of the birefringent region, and a tensile force formed “after” in time closest to the flat portion B1. The region R2 is defined as a region between the stress flat portions B2, and the region R2 is a time period closest to the tensile stress flat portion B2 formed in the birefringent region pattern 150 in “time” in advance. In particular, it is defined as a region between the flat portions B1 of the tensile stress formed “after”.

  Furthermore, since compressive stress remains on the cut surface of the product, the manufacturing method according to the present invention can provide a retardation plate having a significantly high strength on the cut surface.

  Further, in the case of the manufacturing method of the present invention, unlike the method of cutting the glass substrate at the portion of the non-birefringent region that is not affected by the heat of the laser beam, it is avoided that the product size of the retardation plate is increased. Therefore, it is possible to reduce the size of the retardation plate.

  Here, the reason why the stress distribution of the pattern 150 of the birefringent region exhibits such an aspect is not necessarily clear. However, the stress distribution is closely related to the amount of heat input by the laser beam, and tensile stress occurs in the region where the amount of heat input per unit time of the laser beam is almost constant, and the amount of heat input per unit time of the laser beam. Since there is a tendency for compressive stress to occur in a region where the temperature changes rapidly, it is presumed that a stress distribution as shown in FIG. 2 is obtained as a result of such a tendency.

  The concept of the method of manufacturing a retardation plate according to the present invention has been described above with reference to FIG. However, the output waveform 125A of the laser beam shown in FIG. 2 is merely an example, and in the present invention, a modulated laser beam having another output waveform may be used.

  FIG. 3 shows the stress distribution form of the birefringence region obtained when using a laser beam having an output waveform 125B different from the output waveform 125A shown in FIG. 2, and shows the output waveform of the laser beam and the laser beam of the glass substrate. This is schematically shown in correspondence with the scanning position.

In the example of FIG. 3, as shown at the top of the figure, the laser beam has an output waveform 125B that repeats on / off, and the laser output on the vertical axis increases or decreases stepwise with respect to the time on the horizontal axis. . Is one period τ of the output waveform 125B, composed of the period _{t 1} the output becomes 0, and the period _{t 2} the output is 100%. Note that the laser output on the vertical axis is standardized so that the maximum output value is 100%.

Here, the output waveform 125B of FIG. 3, the time period t ₁ the output becomes 0, the output is the period t ₂ to be 100%, but are equal, both period may be different.

  When a laser beam having such a repetitive waveform 125B is used, a birefringence region 145 and non-birefringence are formed on the glass substrate 110 along the scanning direction (Y direction) as shown in the middle stage of FIG. A repeated pattern 150 of the region 147 is formed.

  Further, the absolute value of stress at each position along the broken line L1 of the repetitive pattern 150 shows a stress distribution as shown at the bottom of FIG. That is, in one birefringent region 145, the first and second compressive stress peaks P1 and P2 and a flat portion B2 of tensile stress appear.

  Here, the first compressive stress peak P1 is generated corresponding to the portion 126A where the output sharply increases in the output waveform 125B of the laser beam, and the second compressive stress peak P2 is generated in the output waveform 125B of the laser beam. It occurs corresponding to the portion 126B where the output drops rapidly. In other words, the compressive stress peak P1 occurs in the vicinity of the front end portion 148 of the birefringent region 145 when viewed along the scanning direction of the laser beam, and the compressive stress peak P2 is generated after the birefringent region 145. It occurs in the vicinity of the end 149. Further, a flat portion B2 of tensile stress is generated between the peaks P1 and P2. In other words, the flat portion B <b> 2 of tensile stress is generated at a substantially central portion of the birefringent region 145.

  In FIG. 3, as in FIG. 2, the positional relationship among the laser light output waveform 125B, the birefringent region pattern 150, and the stress distribution is shown approximately for the sake of clarity. It is necessary to note that.

  For example, since there is actually a delay in the heat input of the laser beam, the first compressive stress peak P1 of the pattern 150 in the birefringent region is strictly more time than the rapidly rising portion 126A of the output waveform 125B of the laser beam. Strictly, the second compression stress peak P2 in the stress distribution is also delayed in time from the steeply descending portion 126B of the output waveform 125B of the laser beam. (In the right side of FIG. 3). The same applies to the flat portion B2 of tensile stress.

  Similarly, since there is actually a delay in the heat input of the laser beam, the front end 148 of the birefringent region 145 of the birefringent region pattern 150 is strictly more than the sharply rising portion 126A of the output waveform 125B of the laser beam. The rear end 149 of the birefringent region 145 of the pattern 150 of the birefringent region 150 exists at a position delayed in time (to the right of FIG. 3), and is temporally longer than the steeply descending portion 126B of the output waveform 125B of the laser light. It exists at a delayed position (on the right side of FIG. 3).

  Also in the example of FIG. 3, when manufacturing the retardation plate by dicing or scribing the glass substrate 110, the glass substrate 110 is cut at a portion where the compressive stress in the pattern 150 of the birefringence region remains. . That is, the vicinity of the first compressive stress peak P1 (any position in the region R3) is selected as the first cut portion C1, and the vicinity of the second compressive stress peak P2 is selected as the second cut portion C2. (Any position in the region R4) is selected. Thereby, it can suppress significantly that a crack and a crack arise in a cut part in the case of cutting.

  Here, the region R3 is a region of the birefringent region pattern 150 in which the residual stress that exists “first” in time is zero and the tensile stress that is closest to this and formed “after” in time. The region R4 is defined as a region between the flat portions B2, and the region R4 is formed in the pattern 150 of the birefringent region, with the flat portion B2 of the tensile stress formed “temporarily” in time, and the temporally closest to this. It is defined as the region between the regions where the residual stress existing “after” is zero.

Incidentally, in the laser light output waveform 125B shown in FIG. 3, the output period t ₁ is shorter becomes 0, the pattern 150 of birefringent regions, non-birefringent region 147 (i.e., the residual stress becomes zero area ) May not be formed. In such a case, the regions R3 and R4 may be determined based on the determination method of the regions R1 and R2 shown in FIG.

  4 to 6 show still another example of an output waveform of laser light that can be used in the present invention.

In Figure 4, the output waveform 125C of the laser beam, one cycle τ is a constant minimum value _{P min} in the time period _{(t 1)} up to the time 0 to T _1, the period up to the time _T 1 ~T _{2 (t 2)} laser output in is composed of a waveform decreases monotonically from a maximum value P _max to P _a. (After that, at time _{T 2,} the output _returns to _{P min.)}
Here, the minimum value P _min is assumed to be 50% of the output of the maximum value P _max .

In the example of FIG. 4, _{P A is} has a 75% of _{P max, P A may} be any value between _{P max} of _{P min.} When P _A = P _max , the repetitive waveform 125C is equal to the repetitive waveform 125A of FIG. P _min = 0. In FIG. 4, the periods t ₁ and t ₂ are equal, but the periods t ₁ and t ₂ may be different.

FIG. 5 shows still another example of an output waveform of laser light that can be used in the present invention. In this output waveform 125D, 1 cycle τ is a constant maximum value _{P max} and a constant minimum value _{P min,} in the period _{(t 2)} up to the time _T 1 through T ₂ in the period _{(t 1)} up to the time 0 to T ₁ When, and a monotonically decreasing waveform laser output from the maximum value _{P max} in the time period _{(t 3)} up to the time _T 2 through T ₃ to _{P a.}

Here, the minimum value P _min is assumed to be 50% of the output of the maximum value P _max .

In the example of FIG. 5, _{P A is} has a 75% of _{P max, P A may} be any value between _{P max} of _{P min.} When P _A = P _max , the output waveform 125D is equal to the output waveform 125A of FIG. P _min = 0. In FIG. 5, the periods t ₁ , t ₂ , and t ₃ are equal, but the periods t ₁ , t ₂ , and t ₃ are not limited to this. For example, the periods t ₁ , t ₂ , and t ₃ may be different.

FIG. 6 shows still another example of an output waveform that can be used in the present invention. In this output waveform 125E, 1 cycle τ is time constant minimum value _{P min} at the time to 0~T _{1 (t 1),} the time _T 1 through T period until ₂ laser output _P at _{(t 2) A} a portion monotonously increases to _{P max} from the portion where the laser output is constant maximum value _{P max} in the time period _{(t 3)} up to the time _T 2 through T _3, the period until time _T 3 ~T _{4 (t 4)} Is constituted by a waveform that monotonously decreases from the maximum value P _max to P _B.

Here, the minimum value P _min is assumed to be 50% of the output of the maximum value P _max .

In the example of FIG. 6, _{P A is} has a 80% _{P max, P A may} be any value between _{P max} of _{P min.} Further, P _B is 60% of P _max , but P _B may be any value between P _max and P _min . When P _A = P _max and P _B = P _max , the output waveform 125E is equal to the output waveform 125A of FIG. Further, when P _A = P _max , the output waveform 125E is equal to the output waveform 125D of FIG. P _min = 0. In FIG. 6, the periods t ₁ , t ₂ , t ₃ and t ₄ are all equal, but the periods t ₁ , t ₂ , t ₃ and t ₄ are not limited to this. For example, the periods t ₁ , t ₂ , t ₃ and t ₄ may be different.

  In addition, various output waveforms can be considered. For example, another repetitive waveform may be formed by combining at least two or more of the output waveforms 125A to 125E shown in FIGS.

Incidentally, in the output waveform of the laser beam, as shown in FIGS. 4 to 6, immediately after the period in which the output is the maximum value _{P max} (or instantaneous), the output is between the minimum value _{P min} and a maximum value _{P max} period (e.g., period t ₂ in FIG. _4, a period t ₃ in FIG. _5, and the period t ₄ in FIG. ₆₎ when the provided improves the uniformity of retardation distribution birefringent region. Furthermore, as shown in FIG. 6, just before the period in which the output is the maximum value _{P max} (or instantaneous), the period during which output is between the minimum value _{P min} and a maximum value _{P max} (the period of 6 _{t 2)} When provided, the uniformity of the retardation distribution in the birefringent region is further improved. This is because a local temperature increase of the glass substrate is suppressed to some extent during the scanning of the laser light, and a region where the temperature is constant is likely to occur.

  For example, when laser light having output waveforms 125C, 125D, and 125E as shown in FIGS. 4 to 6 is used, the retardation distribution along the scanning direction in the birefringence region can be within ± 5%. . Similarly, the retardation distribution in the direction perpendicular to the scanning direction in the birefringent region can be within ± 5%.

  A retardation plate having a birefringent region having such a uniform retardation distribution can be used as an element for a high-performance optical pickup device.

(Method for producing retardation plate according to the present invention)
Hereinafter, with reference to FIG. 7 and FIG. 8, the manufacturing method of the phase difference plate by this invention is demonstrated in detail.

  FIG. 7 shows a schematic flow chart of an example of a method for producing a retardation plate according to the present invention. FIG. 8 shows an example of an apparatus used in the method of manufacturing a retardation plate according to the present invention.

As shown in FIG. 7, the method of manufacturing a retardation plate according to the present invention includes
(A) preparing a glass substrate having first and second surfaces (step S110);
(B) scanning the output-modulated laser beam in the glass substrate and / or on the glass substrate in a first direction parallel to the first or second surface; Forming a birefringent region having a tensile stress portion and a compressive stress portion along the direction of 1 (step S120);
(C) cutting the glass substrate so as to pass through the compressive stress portion of the birefringent region (step S130);
Have

  FIG. 8 shows an example of an apparatus used in the method of manufacturing a retardation plate according to the present invention.

  As shown in FIG. 8, an apparatus 200 used in the method of manufacturing a retardation film according to the present invention includes a laser beam 220 emitted from a laser light source (not shown) and a plurality of branched laser beams. A diffractive optical element 250 that branches into light 260A, 260B, and 260C and a lens 230 that converges each branched laser beam 260A, 260B, and 260C to a desired position on the glass substrate 210 are provided.

  The laser light source is not particularly limited, but an excimer laser light source (XeCl: wavelength 308 nm, KrF: wavelength 248 nm, ArF: wavelength 193 nm), YAG laser light source (wavelength 1064 nm), YVO4 laser light source (wavelength 1064 nm), titanium sapphire laser light source (Wavelength 800 nm) or a carbon dioxide laser light source (wavelength 10.6 μm) may be used. The YAG laser light source and the YVO4 laser light source may be, for example, a second harmonic wave source or a third harmonic wave laser source in addition to the fundamental wave described above. For example, a second harmonic YAG laser has a wavelength of 532 nm, and a third harmonic YAG laser has a wavelength of 355 nm.

  The power of the laser light source is not particularly limited, but the larger the power of the laser light source, the more branched laser light can be obtained at one time, which is advantageous in expanding the birefringence region width.

  The diffractive optical element 250 may be any element as long as it can divide one laser beam 220 into a plurality of branched laser beams 260A, 260B, and 260C. For example, the diffractive optical element 250 may be a beam instead of a diffractive optical element. A splitter or the like may be used.

  Hereinafter, each step of the manufacturing method according to the present invention will be described in detail in association with the operation of the apparatus 200 of FIG.

(Step S110)
First, a glass substrate 210 for constituting a phase difference plate is prepared.

  Glass substrate 210 has first and second surfaces. The composition of the glass substrate 210 is not particularly limited. The glass substrate 210 may be, for example, soda lime glass, borosilicate glass, and silica glass. In the present invention, glass doped with a transition metal or the like may be used as the glass substrate 210 in order to increase the absorption coefficient at the wavelength of the laser light 220 to be used.

  The thickness of the glass substrate is not particularly limited. The thickness of the glass substrate may be, for example, in the range of 0.1 mm to 3 mm.

(Step S120)
Next, laser light 220 is emitted from the laser light source toward the glass substrate 210. In the diffractive optical element 250, the laser light 220 is branched into, for example, three or more branched beams 260 (260A, 260B, 260C).

  Each branched beam 260A, 260B, 260C is converged by the lens 230 to form focal points 270A, 270B, 270C in or on the glass substrate 210, respectively. The focal points 270A, 270B, 270C are arranged in a straight line.

  The spot diameters of the focal points 270A, 270B, and 270C vary depending on the performance of the lens 230 and the like, but may be, for example, about 0.1 μm to 100 μm.

  The distance between the focal points 270A, 270B, and 270C is not particularly limited, but due to restrictions on the apparatus configuration, the realistic distance is in the range of 20 μm to 400 μm, and preferably in the range of 50 μm to 250 μm.

  Next, the series of branched beams 260A, 260B, and 260C are scanned in a first direction (Y direction in the example of FIG. 2).

  The scanning speed of each of the branched beams 260A, 260B, and 260C varies depending on the distance between the focal points 270A, 270B, and 270C, but is, for example, in the range of 0.1 mm / second to 50 mm / second.

  As a result, tensile stress parallel to the scanning direction is generated in the regions scanned with the branch beams 260A, 260B, and 260C, thereby forming rod-shaped birefringence region patterns 290A, 290B, and 290C. Here, when the distance between the focal points 270A, 270B and 270C and the intensity and scanning speed of the branched beams 260A, 260B and 260C are adjusted, the branched beams are also heated by heat conduction, and on the glass substrate 210 or in the scanning direction. A uniaxial birefringent region pattern 290 that is continuous in a direction perpendicular to the surface and has a relatively large area can be formed.

  Here, as described above, in the present invention, each of the branched beams 260A, 260B, and 260C is output-modulated.

  Therefore, when the branched beams 260A, 260B, and 260C are scanned on the glass substrate 210, the birefringent regions having a stress distribution as shown in FIG. 2 or FIG. Patterns 290A, 290B, and 290C are formed.

  In the example of FIG. 8, the diffractive optical element 250 divides one laser beam 220 into three branched beams 260A, 260B, and 260C. However, one laser beam 220 may be divided into two or four or more branched beams by the diffractive optical element 250. Alternatively, the apparatus 200 may not have the diffractive optical element 250. In this case, one laser beam 220 is used as it is as a scanning laser beam without being branched.

  That is, in the present invention, the number of branches used may be any number. The number of branches is appropriately selected in consideration of, for example, the necessary width of the birefringent region pattern 290 in the direction perpendicular to the scanning direction of the laser beam (X direction in FIG. 8) or the manufacturing time.

  For example, when the finally obtained retardation plate is applied to, for example, a quarter-wave plate or a half-wave plate for an optical pickup device, a region having a diameter of at least 500 μmφ is required as a birefringent region. In this case, for example, a laser beam branched into six and having a focal interval of 100 μm may be used. Alternatively, step S120 may be repeated as many times as necessary.

  For example, when the three branched beams 260A, 260B, and 260C are scanned, the width of the birefringent region pattern 290 formed at a time (the length in the direction perpendicular to the scanning direction (X direction)) is 200 μm. In this case, a birefringent region having a width of 500 μm or more is formed by repeating the above scanning three times or more by shifting the scanning start point of the branched beams 260A, 260B, and 260C by 200 μm in the X direction each time scanning is performed. Can do. As a result, a retardation plate having a birefringence region pattern at least in a region having a diameter of 500 μmφ can be finally manufactured.

  In addition, when one laser beam capable of forming a birefringent region having a width of 100 μm by one scan is used, the above scan is repeated five times so that a birefringent region pattern is formed in a region having a diameter of 500 μmφ. A phase difference plate can be manufactured.

  As described above, when the output waveforms 125C, 125D, and 125E as shown in FIGS. 4 to 6 are used as the output waveform of the laser light, the retardation distribution along the scanning direction in the birefringence region is expressed as follows: It can be within ± 5%. In addition, in the birefringent region, the retardation distribution in the direction perpendicular to the scanning direction can be suppressed relatively easily by controlling the distance between the focal points of the branched beams. Therefore, in the present invention, a retardation plate having a uniform retardation distribution can be produced along the stretching direction and the vertical direction of the birefringent region.

(Step S130)
Next, the glass substrate 210 is cut (diced) to manufacture a retardation plate. As described above, at this time, the glass substrate 210 is cut so as to pass through the portion where the compressive stress remains in the birefringence region pattern, and thus, at the time of cutting, a crack or a crack occurs in the cut portion. This can be significantly suppressed.

  Through the above-described steps, a chip-shaped small retardation plate having no cuts or cracks on the cut surface can be manufactured.

  FIG. 9A shows a schematic top view of a retardation film 900 manufactured by the method according to the present invention. FIG. 9B shows a schematic stress distribution in the region along the broken line L2 of the retardation film 900. FIG.

  As shown in FIG. 9A, the retardation film 900 is a birefringent region that continuously extends from one end surface 925A to the other end surface 925B of the glass substrate 910 along one direction (Y direction). 930.

  Here, as described above, in the present invention, output-modulated laser light is used as the laser light for forming the birefringent region 930. The birefringent region pattern is cut so as to cross the compressive stress portion.

  For this reason, as shown in FIG. 9B, residual compressive stress exists in the portions 931A and 931B corresponding to the birefringent region 930 of the end surface 925A and the end surface 925B of the obtained retardation plate 900. A retardation film 900 having a relatively high strength can be obtained.

  Further, in the obtained retardation plate 900, the birefringent region 930 can have a relatively uniform retardation distribution.

  For example, in the retardation film 900 manufactured by the method of the present invention, a region of ± 250 μm (that is, a total of 500 μm) along the stretching direction (Y direction) of the birefringent region 930 with the center 901C of the retardation plate 900 as the center. In the region), the retardation distribution can be suppressed to within ± 5%. In addition, the retardation distribution can be suppressed to within ± 5% even in a ± 250 μm region (that is, a total region of 500 μm) along the direction (X direction) perpendicular to the extending direction of the birefringent region 930.

  Such a retardation plate 900 can be used as a quarter-wave plate or a half-wave plate of an optical pickup device.

(Application example of retardation plate according to the present invention)
The retardation plate manufactured by the above-described method can be used as a quarter-wave plate and / or a half-wave plate for an optical pickup device.

  FIG. 10 shows a schematic diagram of such an optical pickup device.

  In FIG. 10, an optical pickup device 1000 includes a laser light source 1010 such as a blue LD (wavelength 405 nm), a half-wave plate 1020, a polarization beam splitter 1030, a quarter-wave plate 1050, and a Blu-ray disc. Such an optical recording medium 1070 and a photodiode 1090 are provided.

  The optical recording medium 1070 may be an optical recording medium such as a CD or a DVD. In this case, the laser light source 1010 may be a light source having a wavelength of 780 nm (in the case of CD) or a wavelength of 650 nm (in the case of DVD).

  The half-wave plate 1020 is a member for giving an optical path difference of λ / 2 (that is, a phase difference of π) between two orthogonal polarization components having a specific wavelength (for example, 405 nm in the case of blue laser light). is there. The quarter-wave plate 1050 provides an optical path difference of λ / 4 (that is, a phase difference of π / 2) between two orthogonal polarization components having a specific wavelength (for example, 405 nm in the case of blue laser light). It is a member.

  In the optical pickup device 1000, linearly polarized light (parallel to the paper surface) 1012 emitted from the laser light source 1010 passes through the half-wave plate 1020, where the linearly polarized light plane is rotated. The light 1012 further passes through the polarizing beam splitter 1030 and the collimating lens 1040 and is guided toward the quarter-wave plate 1050.

  The light 1012 that has passed through the quarter-wave plate 1050 is polarized from linearly polarized light to circularly polarized light, and then irradiated onto the optical recording medium 1070 by the objective lens 1060.

  Next, the light 1013 reflected from the optical recording medium 1070 passes through the same optical path and is guided toward the quarter-wave plate 1050. Here, the light 1013 is polarized into linearly polarized light (perpendicular to the paper surface), and then irradiated to the polarization beam splitter 1030 and guided to the photodiode 1090 through the lens 1080. Information on the optical recording medium 1070 is read by the photodiode 1090.

  Here, the half-wave plate 1020 and / or the quarter-wave plate 1050 is composed of a retardation plate manufactured by the method according to the present invention. That is, in the half-wave plate 1020 and / or the quarter-wave plate 1050, the retardation distribution in the birefringence region is significantly suppressed. Therefore, in this optical pickup device 1000, the light emitted from the half-wave plate 1020 and / or the quarter-wave plate 1050 can be adjusted to a desired polarization state, and wavefront aberration can be suppressed.

  Next, examples according to the present invention will be described.

Example 1
Using the apparatus as shown in FIG. 8, a retardation plate was manufactured in the following procedure.

  First, a glass substrate (borosilicate glass) having a plate thickness of 1 mm was prepared.

  Next, a series of laser beams were irradiated from above the glass substrate through a lens (NA = 0.6), and then scanned in the first direction to form a birefringent region in the glass substrate. The scanning speed was 2 mm / second.

  As a laser light source, AVIA-X manufactured by Coherent having a wavelength of 355 nm was used. The laser beam was split into five laser beams by a diffractive optical element. Each laser beam was condensed in a glass substrate by a lens (theoretical spot diameter: 0.5 μm). The focal points of the laser beams were linearly arranged in the glass substrate, and the distance between the focal points in the glass substrate was 150 μm.

The output waveform of each laser beam was in the form shown in FIG. Here, the minimum output value P _min of the laser beam was zero, and the period t ₁ was 1 sec. Further, the maximum output value P _max of the laser beam was 14 W, and the period t ₂ was 1 sec. Further, the output value _{P A} is set to 10.5 W, the period _{t 3} was set to 1 sec.

  The laser beam was scanned only once.

  Thereby, the pattern of the birefringence area | region was formed in the glass substrate.

  FIG. 11 shows a part of the measurement result of the retardation distribution of the birefringence region pattern (for one period) in the scanning direction of the laser beam. For reference, FIG. 12 shows an example of the measurement result of the retardation distribution of the birefringent region pattern in a direction perpendicular to the laser beam scanning direction (hereinafter referred to as “(laser beam) width direction”). .

  For the measurement of this retardation, a birefringence imaging system Abrio manufactured by Cri was used. In this method, a configuration is used in which a light source and a circular polarization filter are arranged in front of a sample, and an ellipsometer and a CCD camera are arranged behind the sample. In this configuration, the state of the liquid crystal optical element in the ellipsometer is changed, a plurality of images that have passed through the ellipsometer are acquired by a CCD camera, and these images are compared and calculated. Can be quantified.

  As is clear from FIG. 11, the birefringent region pattern includes a first retardation peak Q1 (position of about 800 μm), a flat portion Q2 of retardation (position of about 2000 μm to about 4500 μm), and a second retardation peak. Q3 (about 5000 μm position) is observed. These correspond to the first compressive stress peak P1, the second tensile stress flat portion B2, and the second compressive stress peak P2, respectively.

  As is apparent from FIG. 12, even in the width direction of the laser beam, the birefringence region pattern has a first retardation peak Q4 (position of about 1700 μm) and a flat portion Q5 of retardation (about 2100 μm to about 2900 μm). ) And the second retardation peak Q6 (position of about 3200 μm) is observed.

  Next, the glass substrate was cut along the scanning direction and the width direction of the laser beam. The cutting position of the glass substrate in the scanning direction was set at the positions indicated by arrows S1 and S2 in FIG. Moreover, the cut | disconnection location of the glass substrate in the width direction was made into the position shown by arrow S3 and S4 in FIG.

  As a result, a retardation plate having dimensions of about 5 mm in the vertical direction (scanning direction) and about 5 mm in the horizontal direction (width direction) was obtained. The cut surface of the retardation film was in a healthy state with no cracks or cracks observed.

  FIG. 13 shows the measurement result of the retardation distribution in the birefringence region in the scanning direction of the obtained retardation plate. FIG. 14 shows the measurement results of the retardation distribution in the birefringence region in the width direction of the obtained retardation plate. In FIG. 13 and FIG. 14, the position of the arrow indicates the end face of the retardation film.

  From FIG. 13, the birefringent region is cut at the position of the first retardation peak Q1 and the second retardation peak Q3 in the scanning direction, and compressive stress is generated on the end face of the retardation plate. I understand that. Similarly, FIG. 14 shows that the birefringent region is cut at the compressive stress portion also in the width direction, and compressive stress is generated on the end face of the retardation plate.

  FIG. 15 shows an enlarged view of the flat portion Q2 in FIG. FIG. 16 shows an enlarged view of the flat portion Q5 in FIG.

  From FIG. 15, it can be seen that the retardation distribution of the retardation plate is suppressed within ± 5% over a wide region of 500 μm in the scanning direction. Similarly, it can be seen from FIG. 16 that the retardation distribution of the retardation plate is suppressed within ± 5% over a wide region of 500 μm in the width direction.

  Thus, it was found that the retardation plate obtained by the method according to the present invention can provide a relatively uniform retardation distribution in the birefringent region over a wide range of 500 μm in length and width.

(Example 2)
A retardation plate was produced in the same manner as in Example 1.

However, in Example 2, in the laser output waveform of each laser beam, the minimum output value P _min of the laser beam was set to 7W.

  Other conditions are the same as those in the first embodiment.

  The cut surface of the retardation film was in a healthy state with no cracks or cracks observed.

  In FIG. 17, the measurement result of the retardation distribution of the birefringent area | region in the scanning direction of a laser beam after cut | disconnecting a glass substrate is shown. Moreover, in FIG. 18, the measurement result of the retardation distribution of the birefringent area | region in the width direction of a laser beam after cut | disconnecting a glass substrate is shown. 17 and 18, the position of the arrow indicates the end face of the retardation plate.

  From these results, it can be seen that also in the retardation plate of Example 2, compressive stress is generated on each end face of the birefringent region.

(Example 3)
A retardation plate was produced in the same manner as in Example 1.

However, in Example 3, the laser output waveform of each laser beam was in the form shown in FIG. The maximum output value P _max of the laser beam was 14 W, and the times t ₁ and t ₂ were both 2 sec.

  Other conditions are the same as those in the first embodiment.

  The cut surface of the retardation film was in a healthy state with no cracks or cracks observed.

  In FIG. 19, the measurement result of the retardation distribution of the birefringent area | region in the scanning direction of a laser beam after cut | disconnecting a glass substrate is shown. FIG. 20 shows the measurement result of the retardation distribution of the birefringent region in the width direction of the laser light after cutting the glass substrate. In FIG. 19 and FIG. 20, the position of the arrow indicates the end face of the phase difference plate.

  From these results, it can be seen that also in the retardation plate of Example 3, compressive stress is generated on each end face of the birefringent region.

(Example 4)
A retardation plate was produced in the same manner as in Example 1.

However, in Example 4, the laser output waveform of each laser beam was in the form shown in FIG. The maximum output value P _max of the laser beam was 14 W, the minimum output value P _min of the laser beam was 7 W, and the times t ₁ and t ₂ were both 2 sec.

  Other conditions are the same as those in the first embodiment.

  The cut surface of the retardation film was in a healthy state with no cracks or cracks observed.

  In FIG. 21, the measurement result of the retardation distribution of the birefringent area | region in the scanning direction of a laser beam after cut | disconnecting a glass substrate is shown. FIG. 22 shows the measurement result of the retardation distribution of the birefringent region in the width direction of the laser light after cutting the glass substrate. 21 and 22, the position of the arrow indicates the end face of the retardation plate.

  From these results, it can be seen that also in the retardation plate of Example 4, compressive stress is generated on each end face of the birefringent region.

  As described above, in the method for producing a retardation plate according to the present invention, it was confirmed that when the glass substrate was cut, it was difficult for cracks or cracks to occur in the cut portion. In addition, it was confirmed that the retardation plate manufactured by the method according to the present invention has a compressive stress remaining in the birefringent region, has high strength, and has a relatively uniform retardation distribution.

  The present invention can be applied to optical components such as a retardation plate, a half-wave plate, a quarter-wave plate, an optical pickup element, and an isolator.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Laser beam 3 Lens 4 Birefringent area | region 110 Glass substrate 125A, 125B, 125C, 125D, 125E Output waveform of a laser beam 145 Birefringent area | region 147 Non-birefringent area | region 148 Front end part 149 Rear end part 150 Birefringent area | region Pattern 200 Device 210 Glass substrate 220 Laser beam 230 Lens 250 Diffractive optical element 260A, 260B, 260C Branched laser beam 270A, 270B, 270C Focal point 290, 290A, 290B, 290C Birefringence region pattern 900 Phase difference plate 901C Center 925A, 925B End face 930 Birefringence region 931A, 931B part 1000 Optical pickup device 1010 Laser light source 1012, 1013 Light 1020 1/2 wavelength plate 1030 Polarizing beam splitter 1050 1/4 wavelength plate 10 0 peak of the optical recording medium 1090 photodiode B1 first tensile stress of the flat part B2 second tensile stress of the flat portion P1 first compression stress peak P2 second compressive stress

Claims (9)

A method for producing a retardation plate having a birefringent region in and / or on a glass substrate,
(A) preparing a glass substrate having first and second surfaces;
(B) scanning the output-modulated laser beam in the glass substrate and / or on the glass substrate in a first direction parallel to the first or second surface; Forming a birefringent region having a tensile stress portion and a compressive stress portion along the direction of 1;
(C) A method for producing a retardation plate, wherein the glass substrate is cut so as to pass through a compressive stress portion of the birefringent region. In (b), in the birefringent region, there are a first compressive stress portion and a second compressive stress portion along the first direction, and a tensile stress portion between both compressive stress portions. Formed,
In (c), the glass substrate is cut at a first cutting position and a second cutting position, the first compressive stress portion is selected as the first cutting position, and a second cutting position The method for manufacturing a retardation plate according to claim 1, wherein the second compressive stress portion is selected. The output-modulated laser light has a portion where the laser output increases stepwise and / or a portion where the laser output decreases stepwise with respect to time,
The first compressive stress portion is generated by irradiating a laser beam whose laser output increases stepwise, and / or the second compressive stress portion is a laser whose laser output decreases stepwise. The method for producing a retardation plate according to claim 2, which is generated by irradiating light.   4. The method of manufacturing a retardation plate according to claim 1, wherein the output-modulated laser light has a repetitive waveform having a period τ. 5. The output modulated laser light includes a minimum value and a maximum value of a laser output,
5. The method of manufacturing a phase difference plate according to claim 4, wherein one period τ of the output-modulated laser beam has a flat portion with respect to the minimum time and / or a flat portion with respect to the maximum time.   The method for manufacturing a retardation film according to claim 5, wherein the minimum value is a value other than zero.   The method of manufacturing a phase difference plate according to claim 1, wherein the laser beam is composed of two or more laser beams each having a focal point arranged in a line. A phase difference plate having a birefringent region in and / or on a glass substrate,
The birefringent region extends along a first direction from a first end surface of the glass substrate to a second end surface;
The retardation plate in the birefringent region has a retardation distribution within ± 5% in a region of 500 μm along the first direction.   The retardation plate according to claim 8, wherein the birefringence region has a retardation distribution within ± 5% in a region of 500 μm along a second direction perpendicular to the first direction.

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