JPS62205180A - Adhesive sheet - Google Patents

Abstract

PURPOSE:The titled tape, obtained by applying a compound colorable by irradiation to one surface of a base material, capable of improving the wafer chip detection accuracy by a photosensor and suitable to a dicing process for semiconductor wafers. CONSTITUTION:A sheet 1 obtained by applying a compound 4 colorable by irradiation onto at least one surface of a base material 2 and forming an adhesive layer 3 consisting of an adhesive and a radiation polymerizable compound, preferably urethane acrylate based oligomer. A leuco dye, particularly 4,4',4'- trisdimethylaminotriphenylmethane is preferably used as the radiation polymerizable compound and the above-mentioned compound is preferably added to the base material 2.

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to an adhesive sheet, and more particularly, to an adhesive sheet used for cutting and separating a semiconductor wafer into small pieces. Technical Background and Problems Semiconductor wafers such as silicon and gallium arsenide are manufactured in a large diameter state, and after this wafer is cut and separated into small element pieces (dicing), it is transferred to the next process, the mounting process. ing. At this time, the semiconductor wafer is previously attached to an adhesive sheet and subjected to the following steps: dicing, cleaning, drying, expanding, picking up, and mounting. Adhesive sheets used in the dicing process of semiconductor wafers have traditionally been made of a general-purpose polymer film such as polyvinyl chloride or polypropylene, with an acrylic or other adhesive layer provided on the commercial side. has been used. However, with such adhesive sheets having an acrylic adhesive layer, there is a problem in that when each chip of a diced semiconductor wafer is pick-amplified, the adhesive remains on the chip surface and the chips are contaminated. Ta. In order to solve these problems, conventional methods have been proposed in which the pressure-sensitive adhesive is not applied over the entire surface of the base material, but only partially, thereby reducing the amount of pressure-sensitive adhesive. According to this method, the number of adhesive layers is reduced relative to the total number of chips, and contamination by the adhesive on the chip surface can be reduced to some extent, but the adhesive force between the wafer chips and the adhesive sheet is reduced, so the dicing process cleaning followed by
A new problem arises in that the wafer chip detaches from the adhesive sheet during the drying and expanding steps. Adhesive sheets used in processes ranging from the dicing process to the pick-up process of semiconductor wafers include:
It is desired that the adhesive has sufficient adhesive strength to the wafer chips from the dicing process to the expanding process, and has enough adhesive strength to prevent the adhesive from adhering to the wafer chips during pickup. As such an adhesive sheet, JP-A-60-196.
No. 956 and Japanese Unexamined Patent Publication No. 60-223゜139 disclose a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in its molecule that can be formed into a three-dimensional network by light irradiation on the substrate surface. An adhesive sheet coated with an adhesive consisting of According to the publication, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule include trimethylolpropane acrylate, tetramedyllolmethanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. Examples include acrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and commercially available oligoester acrylate. There is. Adhesive sheets coated with an adhesive layer made of a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as exemplified above may have the following problems. Discovered by the present inventors. A semiconductor wafer is spotted on an adhesive sheet, the wafer is subjected to a dicing process, and the cut and separated wafer chips are then picked up. At this time, the position of the chip is detected by an optical sensor or the like. However, with the adhesive sheet described above, the detection light for the chip position may be reflected by the adhesive sheet, making it impossible to accurately detect the chip position, and malfunctions often occur when picking up the chip. The inventors have discovered that there are problems. In addition, the present inventors have found that when the above-mentioned adhesive sheet is irradiated with ultraviolet rays, the adhesive strength temporarily decreases, but the adhesive strength does not decrease to the optimum value, and the larger the chip, the more difficult it is to pick up the adhesive. discovered by. The inventors of the present invention conducted extensive research to solve the problems associated with the conventional technology, and found that either a compound that becomes shield-colored when irradiated with radiation is applied to the surface of the base material, or a compound that turns into a shield color when irradiated with radiation is applied to the base material. ] The present invention was completed by discovering that it is sufficient to add a compound that colors the product. We have also discovered that if a urethane axolate oligomer is used as a photopolymerizable compound, a pressure-sensitive adhesive sheet with extremely excellent properties can be obtained. Purpose of the Invention The present invention aims to solve all of the above-mentioned problems associated with the prior art.It is an object of the present invention to accurately perform detection using an optical sensor when picking up wafer chips from an adhesive sheet. Therefore, malfunctions do not occur during the wafer depth positioning process, and it has sufficient adhesive strength before radiation irradiation, and after the radiation irradiation, the adhesive strength decreases enough to prevent the back side of the wafer chip. It prevents adhesive from getting on the surface, and in addition, the worker managing the dicing process can easily check whether or not the adhesive sheet has been irradiated with radiation, which can prevent problems in the process. The first aspect of the invention aims to provide an adhesive sheet that is particularly preferably used when subjecting semiconductor wafers to a dicing process. Apply a layer of adhesive consisting of a polymerizable compound.
+i Shitenaru adhesive sheet 1-, 13, lit book 1
It is characterized by coating at least one of its surfaces with a compound that shows six colors depending on the line of sight. Also the present invention

[In the adhesive sheet of the second embodiment, an adhesive layer consisting of a 4-adhesive agent and a radiation-sensitive compound is coated on the surface of the base material. Point Q4 indicates that a coloring compound has been added.
I am Maki. In the adhesive sheet according to the present invention, a compound that is colored by Q1 ray irradiation is coated on at least one surface of the base material, or is added to the base material, so that the adhesive sheet is not irradiated with QJ rays. After this, the sheet is colored =H, so that the detection accuracy is increased when detecting wafer chips by the optical sensor, and malfunctions do not occur when picking up wafer chips. In addition, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. Furthermore, when a urethane acrylate oligomer is used as a radiation-polymerizable compound in the adhesive sheet, an adhesive sheet with extremely excellent performance can be obtained. Invention 4 & 11 As shown in FIG. 1, the adhesive sheet 1 according to the present invention generally consists of a base material 2 and an adhesive layer 3 coated on the surface thereof. In the pressure-sensitive adhesive sheet 1 of the first aspect of the invention, at least one of the front and back surfaces of the base material 2 contains a radiation irradiating compound that is colored by radiation irradiation.
A colored layer 4 is applied. Moreover, in the adhesive sheet 1 of the second aspect of the present invention, a compound that is colored by radiation irradiation is added to the base material 2. The radiation irradiation colored layer 4 containing a compound that is colored by radiation irradiation is made of
It may be formed on the non-containing surface, or it may be formed between the base material 2 and the adhesive layer 3 as shown in FIG. Before use, in order to protect this adhesive layer 3, a releasable sheet (not shown) is placed on the top surface of the adhesive 3.
It is preferable to temporarily attach the adhesive. The shape of the sticky sheet according to the present invention can be any shape such as a tape shape or a label shape. As the base material 2, a material having low electrical conductivity and excellent water resistance and heat resistance is suitable, and a synthetic resin film is particularly suitable. As described below, the adhesive sheet of the present invention is irradiated with radiation such as [B and UV, so in the case of EB@ radiation, the base material 2 does not need to be transparent. However, if it is used with UV illumination, it needs to be a transparent material. Specific examples of such a base material 2 include polyethylene film, polypropylene film, polyvinyl chloride film, polybutylene terephthalate film, polybutylene terephthalate film, polybutene film, polybutadiene film, polyurethane film, and polymethylpentene film. Film, ethylene vinyl acetate film, etc. are used. Also! If a crosslinked polyolefin is used as the IH, 12, it is possible to prevent the adhesive material 2 from elongating or bending in the wafer dicing process described later. Conventionally known adhesives can be widely used, but
Acrylic adhesives are preferred, and specifically, acrylic polymers selected from homopolymers and copolymers containing acrylic acid ester as the main constituent monomer unit and copolymers with other functional monomers. and mixtures of these polymers. For example, as an acrylic ester of Nanatsuma,
Edyl methacrylate, butyl methacrylate, 2-edylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, etc., and those in which the above methacrylic acid is replaced with acrylic acid are also preferred. Can be used. In order to increase the compatibility with the oligomers described below, (
Monomers such as meth)acrylic acid, acrylonitrile, and vinyl acetate may be copolymerized. The molecular weight of the acrylic combination obtained by polymerization from these seven polymers ranges from 2.0 x 10'' to 10.0 x IO, preferably from 4.0 x 10'' to 8,0 x 105. In addition, examples of radiation polymerizable compounds include, for example, JP-A-60
-196.95 June Publication and Japanese Unexamined Patent Publication No. 1986-223, 1
Low molecular weight (a) compounds having at least two or more photopolymerizable carbon-carbon double bonds in the molecule that can be formed into a three-dimensional network by light irradiation as disclosed in the 39th publication are widely used and specifically is trimethylolpropane)7 acrylate, de1heramethylolmethanetetraacrylate-1
・Pentaerythritol triacrylate-1, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hegi-1 acrylate or 1.4-
Butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, and the like are used. Further, as the radiation polymerizable compound, in addition to the above-mentioned acrylate compounds, urethane acrylate oligomers can also be used. The urethane acrylate oligomer is a polyol compound such as a polynisder type or a polyether type, and a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate. , 1° 4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc., to a terminal isocyanate urethane prepolymer obtained by reacting hydroxyl groups with Pi (meth)acrylate such as 2-hydroxyethyl (meth) ) acrylate, 2-
Obtained by reacting hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylate, etc. This urethane acrylate oligomer is a radiation polymerizable compound having at least one carbon-carbon double bond. As such urethane acrylate oligomer,
In particular, the molecular weight is 3,000 to 10,000, preferably 4,000.
It is preferable to use one having a molecular weight of 8,000 to 8,000, because even if the semiconductor wafer surface is rough, the adhesive will not adhere to the chip surface when the wafer chip is picked up. In addition, when a urethane acrylate oligomer is used as a radiation polymerizable compound, it has at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in JP-A No. 60-196.956. Compared to the case where a low-molecular-weight mother compound is used, extremely superior adhesive sheets 1 to 1 can be obtained. That is, the adhesive strength of the adhesive sheet before irradiation with radiation is sufficiently strong, and the adhesive strength decreases sufficiently after irradiation with radiation, so that no adhesive remains on the chip surface when a wafer chip is picked up. The blending ratio of the acrylic adhesive and the urethane acrylate oligomer in the adhesive in the present invention is such that the urethane acrylate oligomer is used in a range of 50 to 900@ffi parts to '+oowm parts of the acrylic adhesive. is preferred. In this case, the adhesive sheet obtained has a high initial adhesive strength, but the adhesive strength decreases significantly after radiation irradiation, and wafer chips can be easily picked up from the adhesive sheet. The compound used in the present invention that is colored by radiation irradiation is a compound that is colorless or light-colored before radiation irradiation, but turns brown upon radiation irradiation, and a preferable specific example of this compound is a leuco dye. It will be done. As the leuco dye, conventional triphenylmethane-based, fluoran-based, fluorothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specifically 3-1y
-(p-tolylamino)1-7-anilite fluorane,
3-[N-(p-tolyl)-N-methylamino 1-fuanilitufluorane, 3-[N-([)-tolyl)-N
-ethylamino]-7-anilitofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, crystal violet rough 1~, 4,4°, 4゛°-
Tris-dimedylaminotriphenylmethanol, 4,4
', 4''4 lisdimethylamino]heliphenylmethane, etc. Color developers preferably used with these leuco dyes include prepolymers of phenol-pormarine resins, aromatic lJx carboxylic acids, etc., which are conventionally used. When electron acceptors such as derivatives and activated clay are removed, and the color tone is to be changed, various known coloring agents can be used in combination. In this way, a compound that is colored by radiation irradiation is once treated with a 1R solvent, etc. Then, apply the obtained solution to either or both of the front and back surfaces of the base material 2.
Radiation point QJ6 containing compounds of 6 colors J from the hk regular line irradiation on at least one of the front and back surfaces of rA2
It depends on the formation of color layer 4. In addition, a compound that covers the radiation point q4 is interposed in an undercoat composition, and this undercoat composition is applied to at least one surface of the front and back surfaces of the base material 2. J% color layer 4 may be formed1゜Such undercoat compositions include those containing a vinyl chloride-vinyl chloride co-consolidated material as a main component, polyurethane resins, polyurethane resins, polyurethane resins, etc. )' Mido resin, epoxy resin, etc. are used. These undercoat compositions are appropriately selected and used depending on the type of the base material 2. On the other hand, a solution obtained by dissolving a compound colored by GtJ rays in a solvent or the like as described above is used when forming and covering the base material 2 in the shape of -H, +; HA2 and irradiates it with radiation. A compound that causes coloration may be added. In some cases, l)! 1. A compound that is colored by the dotted lines may be made into a fine powder and added to the gutter material 2. In this way, the adhesive sheet 1 according to the present invention is exposed to radiation by coating at least one of the front and back surfaces of the base material 2 with a colored compound according to the 94-line rule, or by incorporating it into the base material 2. When irradiated with , the wafer chips are sufficiently colored, and the detection accuracy when detecting the wafer chips by the optical sensor is increased, thereby preventing malfunctions when picking up the wafer chips. Moreover, in the present invention, since the adhesive layer does not contain a compound that is colored by the radiation point q, it is possible to obtain the effect that there is no possibility that the adhesive force of the adhesive layer 3 will be adversely affected by the decrease in the adhesive force due to radiation irradiation. . Further, by mixing Sardine Ana-1 to curing agent into the above-mentioned pressure-sensitive adhesive, the initial adhesive strength can be set to an arbitrary value. As such a curing agent, specifically, a polyvalent isocyanate compound, such as 2,4-tolylene diisocyanate 1-. 2.8-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1.4-xylylene diisocyanate, diphenylmethane-4,4-
Diisocyanate, diphenylmethane-2,4-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicycloxylmethane-4,4-diisocyanate-1, dicyclohexylmethane -2,・1
°-diisocyanate, lysine, isocyanate, etc. are used. Furthermore, among the above adhesives, in the case of UV@Q'J,
By mixing a UV initiator, the polymerization curing time due to UV irradiation and the UV radiation can be reduced.

[It can be done. Specific examples of such UV initiators include benzoin, benzoin methyl ether, benzoin dielether, benzoin isopropyl ether, penzyldiphenyl sulfite, 51...ramethyldiuram tnosulfide, and 7zoin methyl ether. Examples include isobutyronitrile, dibenzyl, diacetyl, and β-chloroanthraquinone. The method of using the adhesive sheet according to the present invention will be explained below. When the adhesive sheet 1 according to the present invention is provided with a peeling ↑1 sea 1- on the upper surface, the sheet is removed, and then the adhesive sheet 1 is placed with the thickener layer 3 facing upward, As shown in FIG. 3, a diced and etched semiconductor wafer A is adhered to the upper surface of the adhesive layer 3. In this pasted state, wafer A is subjected to various processes such as dicing, cleaning, drying, and expanding. At this time, since the wafer chips are sufficiently adhered and held to the adhesive sheet by the adhesive layer 3, the wafer dip does not fall off during the above steps. Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base. At this time, either before or during the pick-up, ultraviolet (UV) or electron beam (E
Ionizing radiation B such as B) is applied to the adhesive layer 3 of the adhesive sheet 1.
The radiation polymerizable compound contained in the adhesive layer 3 is polymerized and cured. When the radiation-polymerizable compound is polymerized and cured by irradiating the adhesive layer 3 with radiation in this manner, the adhesive strength of the adhesive is greatly reduced, and only a small amount of adhesive strength remains. It is preferable that the radiation q' line be applied to the adhesive sheet 1 from the side on which the base material 2σ] adhesive layer is not provided. Therefore, as mentioned above, when using Uv as the radiation Q4 radiation, 12 must be optically transparent; however, when using B as the radiation, the base material 2 must necessarily be optically transparent. In this way, the adhesive layer 3 of the wafer chips A I, A 2, The adhesive sheet is transferred to a pick-up station (not shown), and as shown in FIG.
Push up ...... and this chip A1...
is picked up using air tweezers 6, for example, and mounted on a predetermined base. When wafer chips A1, A2, etc. are picked up in this way, they can be easily picked up without any adhesive attached to the wafer chip surface, resulting in good quality without contamination. of chips. Note that radiation irradiation can also be performed at a pickup station. It is not necessarily necessary to irradiate the entire surface of the wafer A to which the wafer A is attached at once, and some parts may be irradiated several times. For example, wafer chip A1 to be picked up, A2... For each - item, radiation q4 is applied only to the corresponding scene.
After lowering the adhesive force of the adhesive in that area by using a tube, the wafer chips A1 and A2 are removed by a push-up needle 5.
It is also possible to pick up items one by one by pushing them up. FIG. 6 shows a modification of the above-mentioned radiation irradiation method. In this case, the push-up needle 5 is hollow, and a radiation source 7 is provided in the hollow part to perform radiation irradiation and pickup. We are making it possible to do this at the same time.
In this way, the device can be simplified and at the same time the pick-up operation time can be shortened. Note that in the above semiconductor wafer processing, the expanding process may not be performed and the wafer chips A1, A2, . . . may be subjected to a pick-up process immediately after dicing, cleaning, and drying. The adhesive sheet 1 according to the present invention is particularly preferably used when subjecting a semiconductor wafer to a dicing process to a pick-up process as described above, but this adhesive sheet 1 can also be used when mask-dobbing an object to be coated. 1. In the adhesive sheet according to the present invention, in addition to the adhesive and the radiation polymerizable compound, the adhesive layer includes a compound that is colored by radiation irradiation on at least one of the front and back surfaces of the base material. Or, because the adhesive sheet is added to the base material, the sheet is colored after being irradiated with radiation, which increases the detection accuracy when detecting the wafer depth with the optical sensor and prevents malfunctions when picking up wafer chips. It never occurs. Further, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. When urethane acrylate type A oligomer is used as the radiation-polymerizable compound in the adhesive sheet, the adhesive sheet 1 exhibits extremely excellent performance. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 An undercoat composition containing vinyl acetate-vinyl chloride copolymer as a main component. 4.4',4°"-trisdimethylaminotrifluoride was used as a type of leuco dye to color the 100ffi sector at the ultraviolet point QJ. After adding phenylmethane to 5 hand-sewn parts, it was applied to one side of a polyethylene terephthalate film with a thickness of 50 uTrL as a base material to a dry thickness of 1 to 2 μm.
It was coated and dried to form an undercoat layer of 7rL. On the undercoat layer, an acrylic adhesive (1001 parts of a copolymer of 1-butyl acrylate and acrylic acid), 100 parts of a urethane acrylate oligomer with molecules of 3000 to 10000, and a curing agent (di 25 parts of isocyanate type) and 101 parts of UV curing reaction initiator (benzophenone type) were mixed, and viscous 'Ir A1
Dry as a layer and apply it to a dry thickness of 10μ71'L.
TL 2.100'C for 1 minute, but 3 4 (14
The sticky seams 1~ of the present invention, which are used for construction, have been completed. Ultraviolet light (LJ V ) is applied to the adhesive layer of the obtained adhesive sheet.
was illuminated for 2 seconds with an air-cooled high-pressure mercury lamp (80 wy'cm, illuminance, iJ distance 10 cm). The transparent pressure-sensitive adhesive sheet was colored bluish-purple when exposed to UV light. When the color difference △ (L*a*b*) was measured using an 8M color computer (manufactured by Suga Testimonial +a), the color difference was 21.6. Paste the "Siri" know 1 ha on ♀1,
After dicing, ultraviolet irradiation was performed under the conditions described above, and a 4-no-light (SX-23R, Thanks fe1M
), it was possible to easily detect the wafer depth. Furthermore, the wafer depth is exposed to light sensor 9-
When I picked up the device while using it, no malfunctions occurred at all. Comparative Example 1 A pressure-sensitive adhesive sheet was formed in the same manner as in Example 1, except that the undercoat layer that changed to i color by ultraviolet irradiation was not formed in j3 of Example 1 above, and the color difference due to ultraviolet rays was examined. After 1iff of ultraviolet irradiation of the resulting pressure-sensitive adhesive sheet, (1) the color difference ΔF (L"a*b") was 2.0 or less, and no coloring due to the ultraviolet point Q4 was observed. Furthermore, when a silicon wafer was pasted onto this adhesive sheet and, after glazing, ultraviolet rays were irradiated and detection was performed using an optical sensor, there were cases where sufficient detection was not possible. Furthermore, when picking up wafer chips using an optical sensor, malfunctions sometimes occurred.

[Brief Description of the Drawings] Figures 1 and 2 are cross-sectional views of the adhesive sheet according to the present invention, and Figures 3 to 6 show the adhesive sheet used in the process from the dicing process of semiconductor wafers to the stand-up process. It is an explanatory view when used. 1... Adhesive sheet 1-12... Base material, 3... Adhesive layer, 4... Radiation point! , 11th layer, A... wafer, B... q4 line. Agent Patent Attorney Shun Meiki = Part 1 Figure 1 I JE2 Figure 3 M4 Figure 5 Procedure Supplement JF Instruction November 1986 70 1h Correction Office Commissioner Black 1) Ming 7jf Adhesive sheet name FSK Co., Ltd. ] Voluntary amendment 6, amendment λ-1 diagram 7, and the detailed description of the amendment are amended as follows. (1) Page 5, line 3 (before correction) Trimethylolpropane acrylate-1- (after correction) Trimethylolpropane triacrylate (2) Page 9, line 21 (before correction) Low conductivity (after correction) (Deleted) (3) Page 12, line 2 (before amendment) Trimethylolpropane acrylate (after amendment) Trimethylolpropane triacrylate (4) Page 15, line 17 (before amendment) Compound (after amendment) Compound ( 5) Page 18, No. 211 (Before correction) To dicyclooxylmethane-4,4°-diisocyanate-1 (After correction) CyclohenySylmethane-4,4-diisocyanate

Claims (8)

[Claims] (1) A pressure-sensitive adhesive sheet formed by coating a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive and a radiation-polymerizable compound on a base material surface, characterized in that a compound that is colored by radiation irradiation is coated on at least one surface of the base material surface. adhesive sheet. (2) The pressure-sensitive adhesive sheet according to claim 1, wherein the compound that is colored by radiation irradiation is a leuco dye. (3) The adhesive sheet according to claim 2, wherein the leuco dye is 4,4',4''-trisdimethylaminotriphenylmethane. (4) The adhesive sheet according to claim 1, wherein the radiation polymerizable compound is a urethane acrylate oligomer. (5) A pressure-sensitive adhesive sheet comprising a base material surface coated with a pressure-sensitive adhesive layer consisting of a pressure-sensitive adhesive and a radiation-polymerizable compound, the pressure-sensitive adhesive sheet characterized in that a compound that is colored by radiation irradiation is added to the base material. (6) The adhesive sheet according to claim 5, wherein the compound that is colored by radiation irradiation is a leuco dye. (7) The adhesive sheet according to claim 5, wherein the leuco dye is 4,4',4''-trisdimethylaminotriphenylmethane. (8) The adhesive sheet according to claim 5, wherein the radiation polymerizable compound is a urethane acrylate oligomer.