JP5607287B2 - Photosensitive resin for photoreproduction of information layer - Google Patents

Description

  The present invention relates generally to optical disks, and more particularly to photosensitive resins that can be used for optical replication of information layers of optical disks and related applications. Accordingly, the present disclosure relates to optical disc applications such as Blu-ray discs (BD-RW, BD-RE) and high density DVD (HD-DVD) discs.

(Description of related technology)
An example of a well-known optical storage device is a compact disc (CD). CDs can store large amounts of digital information (783 MB) on a very small surface that is inexpensive to manufacture. The surface of a CD is basically a mirror covered with billions of micropores arranged in long, tightly wound spirals or grooves. CD players use a precision laser to read the holes and interpret the information as bits of data.

  The hole helix on the CD starts at the center of the disc. The CD track is 1.6 μm away from the next track and is about 0.5 μm wide. The elongated holes are each about 0.5 μm wide, a minimum length of 0.83 μm, and a height of 125 nm.

  Most of the mass of the CD is an injection molded article of transparent polycarbonate plastic with a thickness of about 1.2 millimeters. During manufacture, the plastic is recessed with fine holes that make up a long spiral track. A thin, reflective aluminum layer is then coated on the surface of the disk to cover the holes.

  When the CD plater is played or read, the laser light of the CD player or device passes through the polycarbonate layer of the CD, reflects off the aluminum layer, and hits an optoelectronic device that detects the change in light. The holes reflect light separately from the flat part of the aluminum layer called lands. The optoelectronic sensor detects these changes in reflectivity, and the electronics in the CD player drive interpret the changes as data bits.

  As a removable storage device, a writable CD (CD-R) and a rewritable CD (CD-RW) device are used. CD-R functions by replacing the aluminum layer in normal CD with an organic dye compound. This compound usually reflects, but when the spot is irradiated with a laser and heated to a specific temperature, the dye "burns" and darkens. In order to read the data written on the CD-R, the laser moves back beyond the disk to process each burned spot as a hole. Data can be written to the CD-R only once. After the pigment burns in the spot, it cannot change originally. CD-RW and DVD discs address this problem by using a phase change that relies on a very special mixture of antimony, indium, silver and tellurium.

  To meet the requirements for higher image recording, high density video and TV recording, interactive DVD movies, and gaming applications, it is necessary to provide higher data capacity CD and DVD discs. To increase data capacity, shorter wavelength lasers are used.

  For example, the first CD format uses a 780 nm laser, then the DVD format uses a 650 nm laser, and more recent Blu-ray Disc (BD-RW, BD-RE) or High Density DVD (HD-DVD) formats. Uses a 405 nm laser. Due to the effectiveness of shorter wavelength lasers, smaller holes, narrower, more tightly compressed grooves are formed on the disk, and a larger amount of data is packed into a predetermined area on the disk. In order to further increase the data density of the optical disc, a plurality of data information layers can be constructed on the disc. That is, the data density of a high density optical disc can be increased by the following two methods: 1) By using a shorter wavelength laser and a higher NA lens, more holes and grooves are formed on the surface of the optical disc. 2) Multiple information layers can be built vertically to supply more data layers in the optical disc.

  Specific examples of DVD-type optical discs having single, double-layer and four-layer data layers are shown in FIGS. 1A to 1C, respectively. A partial view of a DVD disk 10A having a single information layer 12 is shown in FIG. Photosensitive resin for duplication of holes and grooves to construct multiple information layers as shown in 12, 14 and 16, 18, 20, 22 for disks 10B and 10C, respectively, shown in FIGS. 1B and 1C. (Also known as “2P resin”) is used. As shown in FIGS. 1B and 1C, the information layers are separated from each other by optically transparent spacer layers, indicated at 24, 26, 28, 30.

  There are several ways to produce multiple data layers on an optical disc. One method for manufacturing such a data layer is called the 2P method because it uses a photosensitive resin to emboss holes and grooves on the data layer of the optical disc. The holes and grooves correspond to pre-recorded digital information in the case of a pre-recorded medium, and correspond to tracking or header information in the case of a writable medium. A typical or conventional 2P method is illustrated in the schematic process diagram of FIG.

  In FIG. 2, an injection molded first information layer having a semi-reflective layer (not shown) is shown at 41. The first information layer 41 is coated with an optically transparent resin that is finally cured to form the first spacer layer 42. The first spacer layer 42 is then coated with a photosensitive resin 43 and then engaged by a stamper 44. In order to emboss the data from the stamper 44 into the cured photosensitive resin layer 43 disposed on the surface of the spacer layer 42, the stamper is preferably optically transparent so that UV energy is obtained. Is allowed to pass through the stamper 44. Next, the stamper 44 is removed.

  In the conventional 2P method, two types of UV resins are required. First, the spacer layer 42 is manufactured from a UV resin having good adhesion to the semi-reflective layer 41 made of metal or ceramic. The resin for the spacer layer 42 should have a low shrinkage so that the radial tilt and tangential tilt of the disc are low for good tracking of the optical disc at high rotational speeds. The second resin is a UV curable resin for layer 43 that has good adhesion to the cured spacer layer 42 and can be easily separated from the transparent plastic stamper 44 after the UV irradiation step.

  In this technique, one plastic stamper 44 is used for each data layer. Various materials can be used for the stamper, including polycarbonate (PC), polymethylmethacrylate (PMMA), and polyolefin (PO). Only polyolefins are successfully used without the aid of an external release layer on the stamper surface. However, as an alternative, which is an additional release layer on the stamper, polyolefins are expensive. Lower cost plastic materials such as PC and PMMA are polar and their adhesion to 2P resin is superior enough for clean separation from the plastic stamper after the UV curing process.

(Summary of the Invention)
To satisfy the need, an improved photosensitive (2P) resin is disclosed that includes a surface chelator, a monomer, and a surface cure initiator. Optionally, the resin also includes a shrinkage inhibiting component in the form of an oligomer or polymer filler.

More particularly, the disclosed resins include metal and / or ceramic surface chelators, rapid surface cure and glass transition temperature control monomers, surface cure initiators, and optionally shrinkage control oligomers and / or polymer fillers. including.
In a refinement, the chelating agent is selected from the group consisting of carboxylic acids, phosphoric acids, metal hybrid acrylates, silane coupling agents, amine-based acrylates, amide-based acrylates, and mixtures thereof.

  In the improvement, the chelating agent is amine acrylate, dimethylaminoethyl methacrylate, caprolactone-modified 2-hydroxyethyl methacrylate phosphate, 2-hydroxyethyl methacrylate phosphate, 2-methacryloyloxyethyl acid phosphate, 2-methacryloyl. Oxyethyl succinic acid, 2-methacryloyloxyethyl hexahydrophthalate, 2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl phosphate, 2-acryloyloxyethyl phosphate diacrylate, 2-acryloyloxy Ethyl hexahydrophthalate, gamma-mercaptopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, (Beta - aminoethyl) gamma - aminopropyl trimethoxysilane - silane, gamma - methacryloxypropyltrimethoxysilane, and is selected from the group consisting of mixtures thereof.

In the improvement, the glass transition temperature (Tg) of the cured 2P resin is at least 45 ° C.
In another refinement, the monomer is at least one tetra, penta or hexafunctional monomer.
In still other improvements, the monomer is at least one of mono-, di-, or tri-acrylate.

  In an improvement, the monomers include neopentyl diacrylate, isobornyl acrylate, hydroxypivalaldehyde modified trimethylolpropane diacrylate, hydroxylpivalic acid neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, cyclohexane Dimethanol dimethacrylate, ethoxylated bisphenol-A diacrylate, tripropylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane tri (meth) acrylate, tris (2-hydroxyethyl) Isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, ethylene oxide modified bisphenol A dimethacrylate, t-butyl methacrylate, polyethylene glycol diacrylate, 3-methyl-1.5-pentanediol diacrylate, 2-butyl-2-ethyl-1.3-propanediol diacrylate, 2-methyl- Selected from the group consisting of 1.8-octanediol-diacrylate 1.9-nonanediol diacrylate, and mixtures thereof.

In an improvement, the initiator is activated at a wavelength in the range of 310-405 nm.
In an improvement, the initiator is selected from the group consisting of benzophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxycyclohexyl-phenol-ketone, benzophenone, and mixtures thereof. The

In a refinement, the polymer filler is selected from the group consisting of methyl methacrylate acrylic polymer, n-butyl methacrylate polymer, methacrylate, n-butyl methacrylate copolymer, polymer or copolymer or polystyrene or polybutadiene and mixtures thereof.
In an improvement, the oligomer is selected from the group consisting of polyurethanes, polyethers, polyesters, acrylates and mixtures thereof.

  In an improvement, a method for manufacturing an optical disk is provided. The method comprises injection molding a first information layer using a semi-reflective material; spin coating a photosensitive resin on the first information layer as described above; And stamping with a transparent stamper; irradiating the stamped photosensitive resin layer with UV energy and embossing data from the stamper.

If this concept is accurate, the deposition of the separation spacer layer and the curing of the separation spacer layer are not performed, thereby reducing the number of manufacturing steps required to form the optical disk.
In general, the composition for the uncured 2P resin comprises about 0.0001 to about 10% by weight chelating agent; about 10 to about 90% by weight high Tg monomer; about 0.5 to about 40% by weight oligomer and And / or a polymeric filler; and from about 0.5 to about 15 weight percent short wavelength surface cure initiator: 0.5 to 15%.

Preferably, the uncured 2P resin comprises about 0.0002 to about 5% by weight chelating agent; about 20 to about 90% by weight high Tg monomer; about 0.5 to about 25% by weight oligomer and / or high. A molecular filler; and about 3 to about 15% by weight of a short wavelength surface curing initiator: 0.5 to 15%.
More preferably, the uncured 2P resin comprises about 0.0006 to about 2% by weight chelating agent; about 35 to about 90% by weight high Tg monomer; about 0.5 to about 15% by weight oligomer and / or A polymeric filler; and from about 3 to about 12% by weight of a short wavelength surface cure initiator.
Other advantages and features will become apparent upon reading the following detailed description in conjunction with the accompanying drawings.

(Detailed description of presently preferred embodiments)
Photosensitive (2P) with good adhesion to the metal / ceramic surface of the semi-reflective layer and good separation (free or release) from all types of plastic stampers currently used for the manufacture of optical discs ) Resins are disclosed, including, but not limited to, PC, PMMA, acrylic, PMMA-PS copolymer, polyolefin or other types of plastics. The disclosed resin provides (1) clean separation from the plastic stamper, (2) good adhesion to the semi-reflective layer, and (3) low shrinkage upon curing.

  Low shrinkage, strong adhesion to metal or semi-reflective surfaces and clean separation from plastic stampers allow the 2P resin of the present disclosure to be used as both a spacer layer and a replica layer or an embossed layer To do. Low shrinkage ensures that the desired disc tilt can be achieved for optical discs such as Blu-ray (BD-RW, BD-RE) bilayer and HD-DVD bilayer. The low disc tilt provided by the disclosed 2P resin results in a high yield production method with high yield, fewer steps and improved throughput.

  The disclosed 2P resin, which can be used to manufacture both the spacer layer and the embossed layer of the optical disc in one step, is low cost and uses a conventional plastic stamper such as a PC or PMMA stamper. The disclosed 2P resin makes it possible to reduce the manufacturing process and eliminate the need for expensive stamper materials. Thus, the disclosed resin provides a cost reduction in the manufacture of optical disks.

FIG. 3 is a schematic flow chart of the disclosed 2P method using the disclosed 2P resin that eliminates at least two steps in conventional manufacturing techniques.
The disclosed 2P resins may include chelating agents such as metal / ceramic surface chelating agents; monomers such as rapid surface cure and Tg control monomers; and initiators such as surface cure initiators.
Optionally, when low shrinkage is required, shrinkage control oligomers or polymeric fillers may be included as needed.

Metal / ceramic surface chelating agent The metal / ceramic surface chelating agent improves the adhesion of the 2P resin to an inorganic surface such as the metal or ceramic surface of the first information layer. Chelating agents also provide different adhesion strengths for metal and plastic surfaces. The use of chelating agents will provide 2P resin with higher adhesion strength to metal or ceramic surfaces compared to plastic stampers. The following types of chelating agents: adhesion promoters based on carboxylic acids, phosphoric acids, metal hybrid acrylates, silane coupling agents, basic chelating agents containing amines, or amides containing acrylates based on amines. It turns out to be effective.

  Specific examples of chelating agents include those marketed by Sartomer Co., Ltd. (www.sartomer.com) under the trade names CN 373, CN 984, CN 384, CN 386, and CN 371, SR 368. Amine acrylate; dimethylaminoethyl methacrylate marketed by Kyoeisha Chemical Co., Ltd. (www.kyoeisha.co.jp); caprolactone modified by Nippon Kayaku Co., Ltd. (www.nipponkayaku.co.jp) 2-hydroxyethyl methacrylate phosphate, 2-hydroxyethyl methacrylate phosphate, 2-methacryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyethyl hexahydro from Kyoeisha Chemical Co., Ltd. Phthalate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethylphos Acid-based chelating agents such as fete, 2-acryloyloxyethyl phosphate diacrylate, 2-acryloyloxyethyl hexahydrophthalate; currently by OSi Specialties, a unit of GE Specialty Materials (http://gespecialtymaterials.com) Commercially available silanes such as gamma-mercaptopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, N (beta-aminoethyl) gamma-aminopropyltrimethoxy-silane, gamma-methacryloxypropyltrimethoxysilane Chelating agents and mixtures thereof are included but are not limited to these.

Rapid Surface Curing and Tg Control Monomer Surface curing of the 2P resin is important for overall performance. When surface hardening is poor, 2P resin behaves like an adhesive and does not act like a protective coating for good plastic stamper separation. If the surface hardening of the resin is poor, the surface energy of the cured 2P resin exceeds 70 dynes / cm. As a result, the surface of the cured resin film is soft and will not be released cleanly from the plastic stamper. Rapid surface curing of 2P resins can be designed by using appropriate monomers that provide a suitable surface for the separation process.

In order to allow good adhesion to the semi-reflective layer of the optical disc while providing good separation from the plastic stamper, the surface energy of the cured 2P resin is 25-70 at a cure dose of 20 mJ / cm ² . Should be in the dyne / cm range.
The final glass transition temperature (Tg) for the cured 2P resin should exceed 45 ° C. The high Tg of the cured 2P resin is necessary for two main reasons. First, the UV curing process generates heat, and as a result, if the Tg of the cured 2P resin is too low, the shape of the holes may be curved during the separation or release process. Second, the high Tg cured 2P resin reduces the moisture permeability of the optical disk during its lifetime. As a result, the high Tg 2P resin provides a highly reliable optical disc.

  It is well known that tetra, penta or hexa functional monomers provide high Tg and rapid surface cure. However, these monomers have a very high shrinkage on curing. Accordingly, it is preferred to use only mono-, di-, or tri-acrylates. Specific examples of high Tg and fast surface-curing mono-, di-, or tri-acrylate monomers include the following: neopentyl diacrylate, isobornyl acrylate, hydroxypivalaldehyde modified trimethylolpropane Diacrylate, hydroxylpivalate neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, cyclohexane dimethanol dimethacrylate, ethoxylated bisphenol-A diacrylate, tripropylene glycol diacrylate, triethylene glycol diacrylate, 1 , 3-butylene glycol dimethacrylate, trimethylolpropane tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, etho Silylated trimethylolpropane triacrylate, ethylene oxide modified bisphenol A dimethacrylate, t-butyl methacrylate, polyethylene glycol diacrylate, 3-methyl-1.5-pentanediol diacrylate, 2-butyl-2-ethyl-1.3 -Propanediol diacrylate, 2-methyl-1.8-octanediol-diacrylate 1.9-nonanediol diacrylate, etc., and / or mixtures thereof are included, but are not limited to these.

Shrinkage controlled oligomers or polymeric fillers For some types of high density optical discs including BD and HD-DVD, the radial tilt specification is less than 1 °. Low shrinkage oligomers and / or polymer fillers can optionally be used in combination with the disclosed 2P resins to ensure reliable and high yield manufacturing processes. In order to compensate for the high shrinkage (> 8%) of UV-curable monomers, oligomers having a shrinkage of less than 7% and polymer fillers having a shrinkage of about 0% are used. A 2P resin having a cure shrinkage of less than 8% results in an optical disk having a radial tilt of less than 1 °. Also, the choice of oligomer or polymer filler is based on the desired 2P viscosity for the process. Specific examples of polymeric fillers include methyl methacrylate acrylic polymer (Elvacite 2008-C from Lucite International (www.lucitesolutions.com)), n-butyl methacrylate polymer, methacrylate (Elvacite 2051 from Lucite) and n-butyl. Methacrylate copolymers (Elvacite 2767 from Lucite), polymers or copolymers or polystyrene or polybutadiene and the like are included. Specific examples of the low shrinkage acrylate oligomer include polyurethane, polyether, polyester acrylate and the like or a mixture thereof.

Surface Curing Initiator The disclosed 2P resin initiator is a short wavelength initiator. Alpha ketone initiators include benzophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocure 1173 from Ciba-Geigy Co. (www.cibasc.com/darocur_1173.htm)), 1- Hydroxy-cyclohexyl-phenol-ketone (Irgacure 184 from Ciba), benzophenone (Aldrich Chemicals) or similar materials. Shorter wavelength initiators activated at wavelengths in the range of 310-405 nm result in highly cross-linked microsurfaces that aid in clean demolding of the cured 2P resin from the plastic stamper. Furthermore, the laser wavelength for high density optical discs is 405 nm. Initiators used for 2P production of BD or HD-DVD format discs should have absorption capability at wavelengths shorter than 405 nm.

In general, formulations for uncured 2P resins include from about 0.0001 to about 10% by weight chelating agent; from about 10 to about 90% by weight high Tg monomer; from about 0.5 to about 40% by weight oligomer and And / or a polymeric filler; and from about 0.5 to about 15 weight percent short wavelength surface cure initiator: 0.5 to 15%.
Preferably, the uncured 2P resin comprises about 0.0002 to about 5% by weight chelating agent; about 20 to about 90% by weight high Tg monomer; about 0.5 to about 25% by weight oligomer and / or high. A molecular filler; and about 3 to about 15% by weight of a short wavelength surface curing initiator: 0.5 to 15%.

  More preferably, the uncured 2P resin comprises about 0.0006 to about 2% by weight chelating agent; about 35 to about 90% by weight high Tg monomer; about 0.5 to about 15% by weight oligomer and / or A polymeric filler; and from about 3 to about 12% by weight of a short wavelength surface cure initiator.

  In the foregoing embodiments, the major component is always a monomer or a combination of monomers. By keeping the monomer content high, the resulting uncured resin will have an uncured resin ideal for spin coating, preferably having a low viscosity of less than 300 cp. Even an uncured resin with a sufficiently high viscosity exceeding 300 cp and 5,000 to 6,000 cp or more can be used for spin coating, but the process is naturally slow. Therefore, large quantities of monomers are used to keep the viscosity low, and these monomers are major components. While only one rapid cure Tg control monomer is required, Tg control is required, and using the combination in the examples described above, a particular monomer component is based on its viscosity, cure time and glass transition temperature. combine.

  One way to increase the viscosity is to add shrinkage control agents, oligomers, or polymeric fillers at the expense of monomer content. This was achieved in Examples 2-6. Any of the shrinkage control oligomers described above can be added to Examples 1-7 to increase viscosity and handle shrinkage control issues.

  As shown in FIG. 3, the use of the photosensitive resin disclosed herein allows at least two steps for dual information layer discs and additional processing steps for optical discs having two or more information layers. Reduce. In particular, the disclosed photosensitive resin does not require vapor deposition and curing of the transparent spacer layer 42. Only the photosensitive resin layer 43 a is directly deposited on the first information layer 41. This layer 43a is then stamped using a stamper 44 and cured to form a second information layer, as shown on the right side of FIG. By reducing the addition of at least two processing steps for discs with only two layers, and additional steps for four-layer optical discs, the disclosed resin improves manufacturing efficiency and increases throughput. And increase the production yield.

  While only certain embodiments have been shown, alternatives and modifications will be apparent to those skilled in the art from the foregoing description. These and other alternatives are considered equivalent and are within the spirit and scope of this disclosure and the appended claims.

For a more complete understanding of the disclosed resins, methods and optical disks, reference should be made to the embodiments illustrated in more detail in the accompanying drawings.
It should be understood that the drawings are not necessarily to scale, and that the disclosed embodiments are often illustrated schematically and in partial views. In certain embodiments, details not necessary for an understanding of the disclosed method and apparatus or other details that are difficult to recognize are omitted. Of course, it is to be understood that this disclosure is not limited to the specific embodiments shown herein.

1A-1C are cross-sectional views of a single information layer DVD, a dual information layer DVD, and a four information layer DVD, respectively. It is a schematic flowchart which shows the manufacturing method of a prior art optical disc using a normal photosensitive resin and a spacer layer. 6 is a schematic flowchart showing a method of forming an optical disk in which at least two separate manufacturing steps are reduced by using the disclosed photosensitive resin.

Claims (9)

Surface chelating agent selected from the group consisting of:
2-methacryloyloxyethyl acid phosphate, a reactive amine acrylate having one amino group and two acryloyl groups , and mixtures thereof;
Monomers selected from the group consisting of:
Neopentyl glycol diacrylate, hydroxypivalaldehyde modified trimethylolpropane diacrylate, ethylene oxide modified bisphenol A dimethacrylate, and mixtures thereof; and the following surface cure initiators:
2-hydroxy-2-methyl-1-phenyl-propan-1-one;
including,
Photosensitive resin that adheres to the semi-reflective layer but can be cleanly separated from the plastic stamper.   The resin according to claim 1, wherein the cured photosensitive resin has a glass transition temperature (Tg) of at least 45 ° C.   The resin according to claim 1, further comprising at least one of a low shrinkage oligomer and a polymer filler.   The resin according to claim 3, wherein the polymer filler is a methyl methacrylate acrylic polymer or a polystyrene polymer.   The resin according to claim 3, wherein the oligomer is selected from the group consisting of polyethers, polyesters, acrylates and mixtures thereof. 0.0001 to 10 wt% metal and ceramic surface chelating agent selected from the group consisting of:
2-methacryloyloxyethyl acid phosphate, a reactive amine acrylate having one amino group and two acryloyl groups , and mixtures thereof;
10 to 90% by weight of a rapidly curable and glass transition temperature (Tg) controllable monomer selected from the group consisting of:
Neopentyl glycol diacrylate, hydroxypivalaldehyde modified trimethylolpropane diacrylate, ethylene oxide modified bisphenol A dimethacrylate, and mixtures thereof;
0.5 to 15% by weight of the following surface curing initiator:
2-hydroxy-2-methyl-1-phenyl-propan-1-one; and 0.5-40% by weight of at least one of low shrinkage oligomers and polymeric fillers;
including,
Photosensitive resin that adheres well to the semi-reflective layer and can be cleanly separated from the plastic stamper.   The resin according to claim 6, wherein the polymer filler is a methyl methacrylate acrylic polymer or a polystyrene polymer. Injection molding the first information layer using a semi-reflective material;
Spin-coating the photosensitive resin of claim 1 on the first information layer;
Stamping the photosensitive resin layer with an optically transparent stamper;
Manufacturing the optical disk, comprising irradiating the stamped photosensitive resin layer and the stamper with UV energy, embossing data from the stamper; and removing the stamper from the stamped photosensitive resin layer Method.   9. The method of claim 8, wherein vapor deposition of the separation spacer layer and curing of the separation spacer layer are not performed.

Images