JP2005141016A - Junction-type optical element and optical pickup device - Google Patents

Junction-type optical element and optical pickup device Download PDF

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Publication number
JP2005141016A
JP2005141016A JP2003377772A JP2003377772A JP2005141016A JP 2005141016 A JP2005141016 A JP 2005141016A JP 2003377772 A JP2003377772 A JP 2003377772A JP 2003377772 A JP2003377772 A JP 2003377772A JP 2005141016 A JP2005141016 A JP 2005141016A
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Prior art keywords
prism
optical
light
laser
ultraviolet curable
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JP2003377772A
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Japanese (ja)
Inventor
Takuji Hatano
Yuichiro Otoshi
Yuichi Shin
祐一郎 大利
勇一 新
卓史 波多野
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Konica Minolta Opto Inc
コニカミノルタオプト株式会社
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Priority to JP2003377772A priority Critical patent/JP2005141016A/en
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Abstract

PROBLEM TO BE SOLVED: To provide a low-cost and easy-to-manufacture junction type optical element, a junction prism for optical pickup, and an optical pickup device equipped with the same, having light resistance with no practical problem with respect to a blue-violet laser beam.
A polarizing beam splitter BS includes a cemented prism having first and second prism elements P1 and P2 each having a light branching function and a resin layer V that joins between them. The resin layer V is made of an ultraviolet curable adhesive and has a light absorption rate of 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm.
[Selection] Figure 3

Description

  The present invention relates to a junction optical element and an optical pickup device, such as an optical pickup device that records and reproduces optical information on a high-density optical information recording medium with a blue-violet laser beam, and a junction prism used in the optical pickup device. The present invention relates to a junction type optical element.
As a bonded optical element having a structure in which two light transmissive materials are bonded with an adhesive, a polarization separation prism, a dichroic prism, a bonded lens, and the like are known. As an adhesive used for the joining, an ultraviolet curable adhesive is generally used. The ultraviolet curable adhesive has a cost advantage, and also has a manufacturing advantage that an adhesive strength can be obtained quickly by simply irradiating the bonding surface with ultraviolet rays from the outside of the translucent material. However, since it is arranged in the optical path, deterioration is likely to occur, and various proposals for solving it have been made (for example, see Patent Document 1).
JP 2002-189109 A
  However, the conventionally proposed junction structure does not consider the influence of the wavelength used. Therefore, there is a problem in use in a special wavelength range. For example, an optical pickup device generally uses a cemented prism having a polarization separation film for branching an optical signal. However, in the case of a system using a blue-violet laser beam that has been attracting attention in recent years, Is around 400 nm, and a high-power blue-violet laser beam is used for data rewriting. Therefore, the adhesive used for the cemented prism is required to withstand such a use environment. Moreover, since the ultraviolet curable adhesive absorbs ultraviolet light and starts polymerization, it naturally has an absorption characteristic in the ultraviolet region. For this reason, there is a concern about degradation such as peeling for light having a short wavelength and high output, such as a blue-violet laser beam. That is, when a blue-violet laser beam is used for a cemented prism having a structure bonded with an ultraviolet curable adhesive, a reduction in light resistance becomes a problem as compared with the case where a red / infrared laser beam is used.
  The present invention has been made in view of such a situation, and an object of the present invention is to provide a low-cost and easy-to-manufacture junction-type optical element, light having practically no problem with respect to a blue-violet laser beam. An object of the present invention is to provide a pickup prism and an optical pickup device on which the pickup prism is mounted.
  In order to achieve the above object, a bonded optical element according to a first invention is a bonded optical element formed by bonding two light-transmitting materials with an ultraviolet curable adhesive, and the ultraviolet curing after curing. The mold adhesive has a light absorptivity of 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm.
  According to a second aspect of the present invention, there is provided a cemented prism for an optical pickup compatible with a blue-violet laser beam, wherein a first prism element and a second prism element each having a light branching function, and a junction between the first and second prism elements. A cemented prism having a resin layer to be formed, wherein the resin layer is made of an ultraviolet curable adhesive and has a light absorption rate of 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm.
  An optical pickup device according to a third aspect of the present invention is an optical pickup device including a semiconductor laser light source that emits a laser beam having a wavelength of 395 to 415 nm, and is applied to the second invention as a polarization beam splitter that performs polarization separation of a laser beam. It has the junction prism which concerns.
  According to the first invention, the cured ultraviolet curable adhesive has a light absorptivity of 4% or less per 30 μm thickness in the wavelength range of 395 to 415 nm. Although it is a junction type optical element, light resistance with no practical problem with respect to a blue-violet laser beam can be obtained. According to the second invention, since the resin layer is made of an ultraviolet curable adhesive and has a light absorption rate of 4% or less per 30 μm thickness in the wavelength range of 395 to 415 nm, it is easy to manufacture at low cost. Although it is a simple cemented prism, light resistance with no practical problem can be obtained with respect to a blue-violet laser beam. In addition, the third invention realizes a highly durable optical pickup device compatible with a blue-violet laser because the polarizing beam splitter that performs polarization separation of the laser beam has the cemented prism according to the second invention. can do.
  Hereinafter, a bonded optical element and the like embodying the present invention will be described with reference to the drawings. The bonded optical element according to the present invention is formed by bonding two translucent materials with an ultraviolet curable adhesive. By using an ultraviolet curable adhesive, the bonding time can be shortened, so that it is possible to manufacture the bonded optical element quickly and easily, and the cost of the bonded optical element can be reduced due to the cost advantage. . However, as described above, since the ultraviolet curable adhesive has absorption characteristics in the ultraviolet region, if it is irradiated with light having a short wavelength and a high output such as a blue-violet laser beam for a long time, yellowing, peeling, etc. It will cause deterioration. The bonding optical element described below absorbs light in the blue-violet wavelength region (395 to 415 nm) even if it is a resin made of an ultraviolet curable adhesive having absorption characteristics in the ultraviolet region (for example, 340 to 380 nm). This is based on the knowledge that there is no practical problem if the rate is below a certain value.
  First, the light absorption rate of a resin made of an ultraviolet curable adhesive will be described. As shown in FIG. 1, two prisms M1 and M2 made of a light-transmitting material (both are not coated) are bonded together with an ultraviolet curable adhesive made of a modified methacrylate resin, and the joint is in a state close to actual use. Two types of prisms PR were produced. An ultraviolet curable adhesive A was used for one cemented prism PR, and an ultraviolet curable adhesive B was used for the other cemented prism PR. Further, by inserting a spacer between the prisms M1 and M2, the thickness of the resin layer V made of the adhesives A and B was adjusted to 30 μm. Then, ultraviolet irradiation (wavelength 365 nm) was performed on each cemented prism PR to cure the ultraviolet curable adhesives A and B. Next, as shown in FIG. 1, a blue-violet laser beam was incident on each cemented prism PR in which the adhesives A and B were cured. At this time, the blue-violet laser beam from the blue laser light source BD (wavelength 405 nm, output 30 mW) was condensed by the condenser lens LN, so that a spot diameter of about 30 μm was obtained in the resin layer V.
  The spectral characteristics of the resin layer V made of the adhesives A and B immediately after curing are shown in the graph of FIG. In FIG. 2, the solid line shows the light absorption rate (%) of only the resin layer V made of the ultraviolet curable adhesive A, and the broken line shows the light absorption rate (%) of only the resin layer V made of the ultraviolet curable adhesive B. (All of the surface reflections at the prisms M1 and M2 are subtracted). As can be seen from the graph of FIG. 2, the light absorption rate (%) at 405 nm is 2% for the resin layer V made of the adhesive A and 5.5% for the resin layer V made of the adhesive B. The resin layer V made of the adhesive A has a light absorption rate of less than 9% even at a wavelength of 355 nm, whereas the resin layer V made of the adhesive B has a light absorption rate of 5. It has increased rapidly from 5%.
  Table 1 shows the visual observation results (◯: good, x: bad) of the resin layer V after 5000 hours from the incidence of the blue-violet laser beam. There was no change in the resin layer V made of the ultraviolet curable adhesive A, and the resin layer V made of the ultraviolet curable adhesive B was deteriorated (lightly yellowed). From this, it can be seen that the resin layer V made of the ultraviolet curable adhesive A has light resistance with no problem in practical use, and the resin layer V made of the ultraviolet curable adhesive B has a problem due to long-term use. .
  As can be seen from the results in FIG. 2 and Table 1, the degree of deterioration of the resin layer made of the ultraviolet curable adhesive varies depending on the light absorption rate. In a cemented prism that is actually used in an optical pickup device or the like, since the thickness of the adhesive layer is several μm or less, there is no problem in the transmittance of the laser beam. However, when yellowing due to aging occurs, the transmittance rapidly decreases, which is a problem. In particular, in an optical recording apparatus using a rewritable blue-violet laser beam, such deterioration is not allowed because the laser output is large. Further, if the deterioration further progresses, peeling or the like occurs on the joint surface, and it is necessary to prevent this in advance.
  The relationship between the light absorption rate and the deterioration described above is “in the junction type optical element used in the blue-violet wavelength range, if the light absorption rate after curing of the ultraviolet curable adhesive to be used is small in the blue-violet wavelength range, This means that light resistance that is not problematic in actual use can be obtained. From this viewpoint, in order to obtain light resistance with no practical problem, the cured UV curable adhesive (that is, the resin layer) has a light absorption rate of 4% or less per 30 μm thickness in the wavelength range of 395 to 415 nm. It is preferable. In particular, in a junction type optical element (for example, a polarizing beam splitter, a collimator lens, an objective lens, etc.) used for an optical pickup device compatible with a blue-violet laser, the light absorption rate after curing of the ultraviolet curable adhesive is 395 to 395. It is preferably 4% or less per 30 μm thickness in the wavelength region of 415 nm.
  FIG. 3 shows an optical cross section of a prism configuration of a polarization beam splitter BS that performs polarization separation of a blue-violet laser beam as an example of the junction optical element. The polarization beam splitter BS is a junction prism formed by joining a first prism element P1 having a triangular cross section, a second prism element P2 having a parallelogram cross section, and a third prism element P3 having a trapezoidal cross section. As a whole, it has a rectangular cross section. A polarization separation film PC and a reflection film RC are provided on the two bonding surfaces, respectively. The polarization separation film PC and the reflection film RC are parallel to each other and form an angle of 45 ° with respect to the surfaces S1 and S2 of the polarization beam splitter BS. If a half mirror film that splits the light amount of the laser beam at a predetermined ratio is used instead of the polarization separation film PC, a beam splitter for optical path splitting can be configured.
  Bonding between the prism elements P1 to P3 is performed using an ultraviolet curable adhesive. For example, the second prism element P2 provided with the polarization separation film PC and the first prism element P1 are bonded with an ultraviolet curable adhesive, and the second prism element P2 provided with the reflection film RC and the third prism element P3. Are bonded with an ultraviolet curable adhesive. A resin layer V made of an ultraviolet curable adhesive is formed between the prisms P1 to P3. As described above, the resin layer V has a light absorptivity of 4% or less per 30 μm thickness in the wavelength range of 395 to 415 nm.
  FIG. 4 schematically shows an optical configuration of the optical pickup device PU on which the polarizing beam splitter BS is mounted. This optical pickup device PU is capable of recording / reproducing optical information with respect to a high-density medium (corresponding to the optical disk DK in the figure) compatible with a blue-violet laser, and polarization separation of the laser beam. In addition to the polarizing beam splitter BS that performs the above, a blue laser light source BD that emits a laser beam having a wavelength of 395 to 415 nm, a quarter-wave plate QW, an objective lens OL, and a light receiving element PD that includes a photodiode are mainly used. I have.
  The laser beam emitted from the blue laser light source BD enters the polarization beam splitter BS from the surface S2 side, and most of the light is transmitted as P-polarized light to the polarization separation film PC. At this time, the chief ray incident angle of the laser beam with respect to the polarization separation film PC is 45 °. The laser beam transmitted through the polarization separation film PC is emitted from the surface S1 through the polarization beam splitter BS, converted into circularly polarized light by the quarter wavelength plate QW, and then collected on the information recording surface of the optical disc DK by the objective lens OL. Light is reflected.
  The laser beam reflected by the optical disk DK passes through the objective lens OL, is converted into linearly polarized light by the quarter-wave plate QW, and then enters the polarization beam splitter BS from the surface S1 side. Since the laser beam is incident on the polarization separation film PC as S-polarized light, most of the laser beam is reflected by the polarization separation film PC. The laser beam reflected by the polarization separation film PC is reflected by the reflection film RC and then exits the polarization beam splitter BS from the surface S2.
  The laser beam emitted from the polarization beam splitter BS is condensed on the light receiving element PD. The light receiving element PD is provided side by side on the substrate PT together with the blue laser light source BD, and is disposed so as to be parallel to the surface S2 and to face the reflective film RC. The light receiving element PD is composed of a multi-divided PIN photodiode, and outputs a current output proportional to the intensity of the incident light beam or an IV converted voltage from each element. The output is sent to a detection circuit system (not shown) to generate an information signal, a focus error signal, and a track error signal. Based on the focus error signal and the track error signal, the position of the objective lens OL provided integrally therewith is controlled by a two-dimensional actuator (not shown) composed of a magnetic circuit, a coil and the like, and is always on the information track. The light spots are combined.
  In the embodiment of the optical pickup device described above, a junction type optical element is used as the polarization beam splitter BS. However, even when a junction type optical element is used as the objective lens OL, a collimator lens (not shown), It is preferable that the resin layer made of the ultraviolet curable adhesive to be used has a light absorption rate of 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm. As a result, it is possible to obtain light resistance with no practical problem with respect to the blue-violet laser beam, and it is possible to realize a highly durable optical pickup device compatible with the blue-violet laser. This technology is not limited to an optical pickup device, but can be applied to laser scanning devices and various measuring devices using a blue-violet wavelength range.
The figure for demonstrating deterioration of the ultraviolet curable adhesive used for the joining type | mold optical element. The graph which shows the spectral characteristic of the resin layer which consists of an ultraviolet curable adhesive immediately after hardening with a light absorptivity. Sectional drawing which shows typically embodiment of a junction prism. The optical block diagram which shows typically embodiment of an optical pick-up apparatus.
Explanation of symbols
BD Blue laser light source (semiconductor laser light source)
LN condenser lens M1, M2 prism (translucent material)
V Resin layer made of UV curable adhesive PR Bonded prism (bonded optical element)
P1 to P3 First to third prism elements (translucent material)
PC Polarization separation film BS Polarization beam splitter DK Optical disc (optical information recording medium)
PD photo detector

Claims (3)

  1.   A bonded optical element formed by bonding two light transmissive materials with an ultraviolet curable adhesive, wherein the cured ultraviolet curable adhesive is 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm. A junction type optical element having a light absorption rate.
  2.   Any one of the first prism element and the second prism element having a light branching function, and a cemented prism having a resin layer for bonding between the first and second prism elements, the resin layer being an ultraviolet curable type A cemented prism for an optical pickup compatible with a blue-violet laser beam, comprising an adhesive and having a light absorption rate of 4% or less per 30 μm thickness in a wavelength range of 395 to 415 nm.
  3.   An optical pickup device including a semiconductor laser light source that emits a laser beam having a wavelength of 395 to 415 nm, and having the cemented prism according to claim 2 as a polarization beam splitter that performs polarization separation of the laser beam. Pickup device.
JP2003377772A 2003-11-07 2003-11-07 Junction-type optical element and optical pickup device Pending JP2005141016A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7848185B2 (en) 2007-09-04 2010-12-07 Sharp Kabushiki Kaisha Optical pickup
US8339924B2 (en) 2006-10-10 2012-12-25 Panasonic Corporation Optical pickup device capable of emitting first and second light beams having different wavelengths and including a light blocking member for blocking light of a specific wavelength, and a optical information device, computer, optical disk player, car navigation system, optical disk recorder, and optical disk server performing the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8339924B2 (en) 2006-10-10 2012-12-25 Panasonic Corporation Optical pickup device capable of emitting first and second light beams having different wavelengths and including a light blocking member for blocking light of a specific wavelength, and a optical information device, computer, optical disk player, car navigation system, optical disk recorder, and optical disk server performing the same
US7848185B2 (en) 2007-09-04 2010-12-07 Sharp Kabushiki Kaisha Optical pickup

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