Laminate and method for fabricating the same

Abstract

A laminate includes a substrate made of an organic polymer having a functional group containing an oxygen atom or a nitrogen atom, a functional layer bonded to the functional group of the organic polymer contained in the substrate and formed by an atomic layer deposition process, and an overcoat layer provided to cover the functional layer and containing transition metal atoms. Because the adhesion between the substrate and the functional layer is improved and the functional layer is protected by the overcoat layer, it is possible to achieve both improved gas barrier properties and/or improved durability against an environmental stress such as heat, humidity and the like.

Claims

1. A method for fabricating a laminate comprising a substrate, a functional layer and an overcoat layer are stacked in this order, the method consisting of: providing a substrate which contains an organic polymer having a functional group containing an oxygen atom or a nitrogen atom, feeding a precursor material of a functional layer onto a surface of the substrate, purging an inert gas to remove a portion of the precursor material not bonded to the surface of the substrate, forming the functional layer, which is an atomic layer deposition film by repeatedly reacting the precursor material; bonded to the surface of the substrate, with an oxidative gas by plasma excitation, and, forming an overcoat layer consisting of tantalum oxide, on the functional layer by a physical vapor phase growth method or a chemical vapor phase growth method, wherein the fabricated laminate consists of (a) the substrate, (b) the atomic layer deposition film and (c) the overcoat layer consisting of tantalum oxide.

2. The method of claim 1, wherein a thickness of the overcoat layer is from 5 to 1000 nm.

3. The method of claim 1, wherein a thickness of the overcoat layer is from 5 to 20 nm.

4. The method of claim 1, wherein the atomic layer deposition film is an Al.sub.2O.sub.3 atomic layer deposition film.

5. The method of claim 1, wherein the overcoat layer is formed by a physical vapor phase growth method.

6. The method of claim 1, wherein the overcoat layer is formed by sputtering.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic sectional view showing a configuration of a laminate related to an embodiment of the present invention.

(2) FIG. 2 is a flow chart schematically showing the steps of fabricating the laminate shown in FIG. 1.

(3) FIG. 3 is an illustrative view of a film-forming process using a roll-to-roll system.

DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

(4) The preferred embodiments of the invention will be described below in detail with reference to the drawings. Note that, in the drawings, the same or equivalent components are represented by the same reference numerals, and overlapping descriptions will be omitted. Further, although the description has been made with reference to a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of the above embodiments on the basis of the above disclosure is obvious to a person having ordinary skill in the art. That is, the present invention may not be limited to the aforementioned embodiments. Design modifications or the like can also be made to the above embodiments on the basis of a knowledge of a skilled person in the art, and such modifications or the like without departing from the principle of the present invention are encompassed within the scope of the present invention.

SUMMARY OF EMBODIMENTS

(5) The laminate related to the present invention is one which has a functional layer formed by an atomic layer deposition method and an overcoat layer made of an inorganic material stacked on a substrate made of an organic polymer in this order. The overcoat layer is a film formed by a sputtering process, a CVD process or a vacuum deposition process and is formed of a transition metal atom-containing inorganic film, so that the surface of the laminate can be protected with a chemically stable material.

(6) The formation of the overcoat layer on the functional layer enables the resulting laminate to have more improved or even excellent characteristics than with the case of the functional layer alone.

(7) <Approach to the Present Invention>

(8) As to the laminate provided with the atomic layer deposition film (ALD film) prepared by an atomic layer deposition process (ALD process), commercial production has now been performed for use as electronic part substrates, such as a glass substrate, a silicon substrate and the like, in thin film inorganic ELs, displays, semiconductor memories (DRAM) and the like. On the other hand, a substrate of a laminate, to which the present invention is directed, is made of an organic polymer, for which there may be some cases where adsorption sites on which the precursor can be adsorbed may not be present sufficiently unlike a glass substrate or a silicon substrate.

(9) Accordingly, the selection of a substrate on which an ALD film is to be formed is an important factor in view of the development of function. In the practice of the present invention, a laminate is formed in such a way that an overcoat layer made of an inorganic component containing transition metal atoms is formed, according to a sputtering process, on an ALD film serving as a functional layer formed on a substrate, and the relation between a water vapor transmission rate and a water vapor transmission rate after a resistance test has been checked.

(10) Although it is generally considered that an ALD film is two-dimensionally grown on an electronic part substrate, an ALD film on an organic polymer substrate (e.g. PET: polyethylene terephthalate) is not actually grown two-dimensionally. In other words, with the formation of an ALD film on a polymer substrate by an ALD process, two-dimensional growth inherent to the ALD process cannot be realized. It is assumed that the main reasons for this reside in “the type of adsorption site” and “the density of the adsorption sites” and “the diffusion of a precursor toward a free deposition region” on a polymer substrate. For such reasons, it becomes important how to select an organic polymer substrate so as to efficiently form an ALD film.

(11) With respect to the first reason of the density of the adsorption sites of a precursor in the ALD film, we consider as follows. A gaseous precursor (e.g. TMA: Trimethyl Aluminum) or a metal-containing precursor such as TiCl.sub.4 is chemically adsorbed on the surface of a polymer substrate (which may be sometimes referred to merely as substrate hereinafter) to provide a first step of the ALD process. The reactivity between the precursor and a functional group (Functional Group) of the substrate and the density of the functional group greatly influence the chemical adsorption.

(12) For example, with a polymer (polymer), the precursor of the ALD film is reversibly bonded to the polymer substrate in a manner as shown in the following chemical formula (1).

(13) ##STR00001##

(14) In the formula (1), the OH group present in the polymer chain serves as a bonding site.

(15) If the functional group is low in density, the bonding sites of the precursor are distributed in a sparse state. Where the bonding sites are in a sparse state, the ALD film grows three-dimensionally from the adsorption sites serving as nuclei. More particularly, if the density of the bonding sites is low, the ALD film grown from the precursor extends three-dimensionally and the precursor sparsely adsorbs on OH group-present portions, so that the ALD film columnly grows about the isolated nuclei. Thus, the ALD film cannot be formed efficiently, thus leading to difficulty in forming an ideal functional layer. For this, the selection of a substrate becomes important.

Embodiments

(16) [Configuration of Laminate]

(17) FIG. 1 is a sectional view showing a configuration of a laminate according to an embodiment of the present invention.

(18) As shown in FIG. 1, a laminate 1 includes a substrate 2 formed of a polymer material, a filmy or film-shaped functional layer 3 formed on the surface of the substrate 2 by an atomic layer deposition process, and an overcoat layer (OC layer) 4 formed on the functional layer 3 and made of an inorganic component. The functional layer 3 makes use of a precursor material as a starting material, for which an organometal material is ordinarily used. The precursor material is adsorbed on adsorption sites of the polymer substrate and reacts with a reactive gas to cause strong adhesion to the polymer substrate.

(19) In order to adsorb the precursor material on the substrate 2 to efficiently form the functional layer 3, it is necessary to select a polymer material having a functional group, with which the precursor material is likely to be adsorbed. In addition, it is also necessary to select an organic polymer whose density of the functional groups, on which the precursor material is adsorbed, is high. Additionally, the substrate 2 may be subjected to surface treatment such as a plasma treatment, a hydrolysis treatment or the like so that the surface of the organic polymer is modified to form more dense OH groups. When an inorganic compound is added to the organic polymer, it becomes possible not only to increase the adsorption density of the precursor, but also to further improve the adhesion between the substrate 2 and the functional layer 3.

(20) Here, the organic polymer having a functional group, with which the precursor of the functional layer 3 is susceptible to adsorption, is now described.

(21) As to the material of the substrate 2, where polypropylene (PP) indicated by the following chemical formula (2) is used as a material of the substrate 2, there is no functional group capable of bonding with a precursor. Accordingly, even where the precursor is diffused throughout a free volume within the substrate 2, difficulty is involved in holding the precursor on or inside the substrate. Since the precursor cannot be bonded to the methyl group, PP is not a favorable organic polymer material for use as a substrate.

(22) ##STR00002##

(23) Where polyethylene terephthalate (PET) indicated by the following chemical formula (3) is used, the precursor can react with the oxygen atom of the ester bond, so that the precursor can remain on or inside the substrate. Accordingly, PET can be used as a substrate material. When the substrate made of PET is subjected to surface treatment such as plasma treatment or the like to decompose the ester bond thereby generating a hydroxyl group (—OH) and a carboxyl group (—COOH), the precursor can be more susceptible to adsorption.

(24) ##STR00003##

(25) Where the polyimide indicated by the following formula (4) is used as a substrate, a precursor material is able to react and bond with the imide and can efficiently remain on or inside the substrate. The precursor is very susceptible to adsorption with an imide, so that the polyimide is preferred as an organic polymer material used for the substrate.

(26) ##STR00004##

(27) Other instances of the functional group on which the precursor of the ALD film is likely to be adsorbed include nylon-6 having an amide group and represented by the following chemical formula (5), a polyether sulfone (PES) having a sulfonyl group and represented by the following chemical formula (6), and polyvinyl alcohol (PVA) having a hydroxyl group and represented by the following chemical formula (7).

(28) ##STR00005##

(29) More particularly, organic polymers used as a substrate are preferably those having an oxygen-containing functional group or a nitrogen-containing functional group. The functional group having an oxygen atom includes OH group, COOH group, COOR group, COR group, NCO group, SO.sub.3 group or the like. The functional group having a nitrogen atom includes NH.sub.x group (wherein X is an integer). Besides, the functional group of an organic polymer used as a substrate may be one that contains an atom having an unshared electron pair or an unpaired electron and is capable of coordination bonding with a precursor, bonding through intramolecular forces (Van der Waals forces) or interaction through hydrogen bond or the like.

(30) Aside from the organic polymers having structures of the above chemical formulas, there can be used polyvinyl alcohol, polyethylene imines, acrylic ester, urethane acrylic, polyester acrylic, polyether acrylic and phenolic resins, and polyether ketones, aliphatic polyketones, polybutylene terephthalate, polytrimethylene terephthalate and the like. Moreover, epoxy resins and acrylic resins having such functional groups as indicated above may also be used.

(31) The precursor is supplied to the substrate of such an organic polymer as mentioned above, so that there are efficiently performed diffusion to and adsorption on the surface inside of the substrate and adsorption on the substrate surface, thereby leading to the formation of a desired functional layer 3.

(32) [Fabrication Process of Laminate]

(33) FIG. 2 is a flow chart schematically showing the fabrication process of the laminate 1 shown in FIG. 1.

(34) Initially, a substrate 2 made of an organic polymer is placed in a vacuum film-forming apparatus (such as a semiconductor manufacturing apparatus) (Step S1).

(35) Next, a functional layer 3 is formed on the surface of the substrate 2 placed in the vacuum film-forming apparatus according to an atomic layer deposition process. In more detail, a precursor used as a starting material of an ALD film is exposed to the substrate 2 to permit crosslinking bond with a functional group present on the surface of the substrate (Step S2). Subsequently, the precursor material remaining on the surface without bonding with the functional group present on the surface of the substrate and the precursor material present in a film-forming chamber of the vacuum film-forming apparatus are both exhausted (Step S3). The manner of exhausting the precursor material includes a method of exhausting a precursor material in the film-forming chamber by use of a vacuum pump, and a method of feeding an inert gas, such as N.sub.2, to the film-forming chamber while exhausting with a vacuum pump. Next, the step S2 and the step 3 are repeated given times (Step S4) so that the precursor material is bonded to the functional groups, not yet bonded to the precursor material, on the surface of the substrate 2 (Functional Layer Forming Step B). When this step is carried out, an ALD film grows two-dimensionally, with the possibility that a dense functional layer 3 can be formed. It will be noted that if necessary, the substrate 2 may be subjected to plasma treatment or hydrolysis treatment prior to the step S2. When these pre-treatments are carried out, the high density of the functional groups of an organic polymer can be realized.

(36) Further, when the steps S2 to S4 are repeated, there is formed the functional layer 3 by reacting the precursor material bonded to the surface functional groups of the substrate 2 (Step S5). The formation of the functional layer 3 can be carried out by feeding a reactive gas into the film-forming chamber or by generating an excited plasma gas in the film-forming chamber. Next, the functional layer forming step B and the step S5 are repeated until the total thickness of the formed atomic layer deposition film arrives at an intended level (the number of cycles) of the functional layer (Step S6), thereby forming a functional layer having a predetermined thickness (Functional Layer Forming Step A).

(37) Further, an overcoat layer 4 is formed on the surface of the thus formed functional layer 3 by a PVD process, a CVD process, or a vacuum deposition process (Step S7).

(38) According to the steps of from Step S1 to Step S7, the overcoat layer 4 can be formed as a protective layer for the functional layer 3 formed by the atomic layer deposition method, so that the durability of the laminate 1 can be improved. Moreover, the formation of the overcoat layer 4 can lead to drastically improved characteristics in comparison with the case that the functional layer 3 is provided singly. Thus, the durability of the laminate 1 can be maintained at a higher level and thus, a gas barrier film of high reliability can be realized.

(39) [Inorganic Film Used for Functional Layer]

(40) Next, an inorganic film used as the functional layer 3 is illustrated. The functional layer 3 is an ALD film formed by an atomic layer deposition method. An organometal compound is used as a precursor material of the ALD film. Usable precursor materials for the ALD film include, for example, trimethyl aluminum (TMA), titanium tetrachloride (TiCl.sub.4), tris(dimethylamino)silane (3DMAS) and bis(diethylamino)silane (BDEAS). Besides, there may be used precursor materials containing at least one of the elements of Group II, Group III, Group IV and Group V of the periodic table, transition metal elements, and lanthanoid elements. These precursor materials are oxidized with a reactive gas such as H.sub.2O, H.sub.2O.sub.2 or the like. Alternatively, O.sub.2, N.sub.2, CO.sub.2, H.sub.2 or a mixed gas thereof is applied with a voltage to generate a plasma, followed by reaction with a precursor to form a metal film of the metal contained in the precursor material, an oxide film, a nitride film or an oxide nitride film thereby obtaining an ALD film. The thickness of the ALD film is preferably not less than 2 nm, more preferably not less than 5 nm in view of ensuring characteristics thereof. The number of repetitions of the film formation in the ALD process is preferably not less than 10 cycles, more preferably not less than 30 cycles in view of ensuring characteristics. Since the size and ratio of the free volume of the organic polymer, respectively, variously vary depending on the type of organic polymer substrate, the thickness of the ALD film and the number of repetitions of the film formation are not specifically limited regarding their lower limits and can thus be appropriately determined depending on the type of material for the substrate. Where the functional layer formed by use of such a precursor as indicated above is made, for example, of an oxide film, there may be used a film of Al.sub.2O.sub.3, TiO.sub.2, SiO.sub.2 or a mixed oxide, i.e., having a ternary composition such as AlSi.sub.xO.sub.y, TiAl.sub.xO.sub.y or the like.

(41) [Inorganic Film Used as OC Layer]

(42) Next, the method of forming an overcoat layer formed on the functional layer 3 is illustrated. The overcoat layer is made of an inorganic film and can be formed by a variety of means capable of forming an inorganic film, such as a PVD process, a CVD process and the like. With the CVD process, limitation is placed on the type of organometal compound to be used and with the vacuum deposition process, the process and apparatus greatly influence the melting point of a material. In view of these facts, the sputtering process is preferred to form an overcoat layer. The film composition of the overcoat layer includes those of an oxide film, a nitride film or an oxide nitride film, each containing at least one transition metal element selected from elements of Group III, Group IV, Group V and lanthanoid elements. For example, where the overcoat layer is made of an oxide film, there may be used films of Ta.sub.2O.sub.5, V.sub.2O.sub.5, Nb.sub.2O.sub.5, HfO.sub.x, ZrO.sub.x and a mixed oxide thereof.

(43) Next, a method of fabricating a functional film by a roll-to-roll system is illustrated with reference to FIG. 3.

(44) FIG. 3 is an illustrative view of a film-forming process using a roll-to-roll system.

(45) The film-forming apparatus shown in FIG. 3 includes an unwinding chamber 10 for feeding a starting substrate, a first film-forming chamber 20 for forming a functional layer, a second film-forming chamber 30 for forming an overcoat layer, and a winding chamber 40 for winding a finished functional film. The elongated substrate is transferred to the unwinding chamber 10, the first film-forming chamber 20, the second film-forming chamber 30 and the winding chamber 40 in this order thereby continuously forming the functional layer and the overcoat layer on the substrate.

(46) The first film-forming chamber 20 includes, in parallel, precursor regions 21 and 21′, into which a precursor material is introduced, purge regions 22 and 22′ into which an inert gas is introduced, and a reaction region 23 wherein the precursor is reacted. As shown in FIG. 3, the precursor region 21, the purge region 22, the reaction region 23, the purge region 22′ and the precursor region 21′ are arranged in this order. While being folded back within the precursor regions 21 and 21′, the substrate is passed in the order of precursor region.fwdarw.purge region.fwdarw.reaction region.fwdarw.purge region.fwdarw.precursor region.

(47) Initially, a rolled substrate attached to an unwinding unit 11 of the unwinding chamber 10 is unwound and transferred to the first film-forming chamber 20 wherein an ALD film is formed. Next, the substrate is passed to the precursor region 21, into which a precursor used as a starting material for the atomic layer deposition film of the first film-forming chamber 20 is introduced. At this stage, the precursor is fed to the surface of the substrate and is bonded to the functional group present on the surface of the substrate. Next, the substrate having adsorbed the precursor thereon is passed through the purge region 22, into which an inert gas not reacting with the precursor, such as N.sub.2 or Ar, has been introduced. On this occasion, an excess of the precursor, not bonded to the functional group of the precursor fed to the substrate, is purged with the inert gas.

(48) Next, the substrate is passed through the reaction region 23, into which an oxidative gas is introduced and in which oxygen atom active species generated by plasma excitation are present. At this point of time, the precursor material bonded onto the substrate is reacted. Thereafter, the substrate is passed to the purge region 22′, followed by transferring again to the precursor region 21′.

(49) It will be noted that in the present embodiment, the substrate is passed through the precursor regions 21 (21′) and the purge regions 22 (22′), once for each region, prior to the passage through the reaction region 23. Nevertheless, it is preferred that prior to the passage through the reaction region 23, the passages through the precursor regions 21 (21′) and the purge regions 22 (22′) are repeated. The repeated passages through the precursor regions 21 (21′) and the purge regions 22 (22′) enable an adsorption density of the precursor adsorbed on the substrate surface to be increased thereby making it possible to form a dense film.

(50) When the substrate is repeatedly passed through the precursor regions 21 (21′), the purge regions 22 (22′) and the reaction region 23 of the first film-forming chamber 20, the ALD film can be formed in a desired thickness.

(51) The substrate on which the ALD film has been formed is transferred from the first film-forming chamber 20 and sent in the second film-forming chamber 30. Where the pressure between the first film-forming chamber 20 and the second film-forming chamber 30 differ from each other, a differential pumping mechanism may be provided between the first film-forming chamber 20 and the second film-forming chamber 30. Where the film-forming rate of the functional layer (ALD layer) and the film-forming rate of the overcoat layer differ from each other, a substrate storage unit may be provided between the first film-forming chamber 20 and the second film-forming chamber 30.

(52) The substrate fed into the second film-forming chamber 30 is passed through a main roll 31 disposed in the second film-forming chamber 30 wherein a film composition 33 fed from a starting material feed unit 32 for overcoat layer is formed on the substrate as a film. If a sputtering process is used for the film formation in the second film-forming chamber 30, the starting material feed unit 32 becomes a sputtering target, and the film formation by reactive sputtering may be performed by introducing a reactive gas. Where a CVD process is used for the film formation in the second film-forming chamber 30, the starting material feed unit 32 becomes a precursor feed port and a CVD film can be formed by introducing a reactive gas. Moreover, where a vacuum deposition process is used for the film formation in the second film-forming chamber 30, the starting material feed unit 32 becomes a vacuum deposition source and a vacuum deposited film can be formed by heating or by irradiation of an ion beam. The overcoat layer containing an inorganic film can be formed according to any of the above processes.

(53) The substrate, on which the overcoat layer has been formed, is transferred from the second film-forming chamber 30 and fed into a winding chamber 40 and wound around a winding unit 41 mounted in the winding chamber 40. A roll-shaped functional film can be obtained through the above steps.

EXAMPLES

(54) Specific examples of the laminates of the present invention realized based on the foregoing embodiments are illustrated.

(55) An ALD film serving as a functional layer and made of Al.sub.2O.sub.3 and a sputtered film of Ta.sub.2O.sub.5 used as an overcoat layer were stacked on a polymer substrate to form a functional film. The respective layers were formed in the following way.

(56) [Method of Forming an Al.sub.2O.sub.3 Film]

(57) An AL.sub.2O.sub.3 film (ALD film) was formed on at least one surface of a polymer substrate by an ALD process. On this occasion, a precursor gas used was trimethyl aluminum (TMA). Simultaneously with the precursor gas, O.sub.2 and N.sub.2 serving as process gases, O.sub.2 and N.sub.2 serving as purge gases, and O.sub.2 serving as a reactive and plasma discharge gas were, respectively, supplied to the film-forming chamber. The treating pressure at this stage was set at 10 to 50 Pa. Moreover, a 13.56 MHz power supply was used as a power supply for plasma gas excitation. The plasma discharge was performed in ICP (Inductively Coupled Plasma) mode.

(58) Prior to the formation of the ALD film, an O.sub.2 plasma treatment was carried out as a pretreatment in order to increase the density of adsorption sites on the substrate surface. On this occasion, the flow rate of O.sub.2 was set at 100 sccm, and the plasma discharge was generated in ICP mode. It will be noted that the output power of the plasma discharge was set at 300 watt and 60 seconds treatment was carried out.

(59) The feeding times of the respective gases were 60 mseconds for the TMA and the process gas, 10 seconds for the purge gas, and 10 seconds for the reaction and discharge gas. The plasma discharge was generated in ICP mode simultaneously with the feed of the reaction and discharge gas. It will be noted that the output power of the plasma discharge at this time was set at 250 watts. The gas purge after the plasma discharge was such that O.sub.2 and N.sub.2 serving as the purge gases were fed at a flow rate of 100 sccm for 10 seconds, respectively. The film-forming temperature was set at 90° C.

(60) The unit film-forming rate of AlO.sub.x under such cycle conditions as described above was about 1.4 Å/cycle. The film-forming treatment of 73 cycles was performed to form a film having a thickness of about 10 nm, for which the total film-forming time was about 60 minutes.

(61) [Method of Forming an Overcoat Layer]

(62) The lamination intermediate formed with the ALD film was mounted in a stage of a film-forming chamber of a sputtering apparatus. The pressure in the film-forming chamber was set at not large than 5.0×10.sup.−4 Pa, after which Ar and O.sub.2 were, respectively, introduced into the film-forming chamber at flow rates of 30 sccm and 10 sccm. The pressure in the film-forming chamber was maintained at 2.5×10.sup.−1 Pa by adjusting an orifice at an exhaustion side. Next, a direct current voltage was applied between the stage and a target to form an overcoat layer by reactive sputtering. A Ta target was used as a sputtering target and the film formation was performed at a constant electric power of 300 watt. At that time, the voltage was 610V, the electric current was 0.51 A, a rotational speed of the stage was 6 r.p.m., and the distance between the target and the stage was 200 mm.

(63) The film-forming rate of Ta.sub.2O.sub.5 under such conditions as indicated above was 10 nm/minute, so that the film formation was performed by appropriately setting a film-forming time so as to obtain a desired thickness of the overcoat layer.

(64) The function of the resulting laminate film was evaluated using, as an index, a water vapor transmission rate (WVTR) prior to and after a durability test. The method of measuring a water vapor transmission rate and a durability testing method are, respectively, as follows.

(65) [Method of Measuring a Water Vapor Transmission Rate]

(66) Using MOCON Aquatran (registered trade name), manufactured by Modern Controls, Inc., as a water vapor transmission rate measuring device, a water vapor transmission rate of a sample was measured in an atmosphere of 40° C./90% RH. A laminate whose water vapor transmission rate was not larger than 0.02 [g/m.sup.2/day] was subjected to measurement using Aquatran.

(67) [Durability Test]

(68) Using a PCT (Pressure Cooker Test) device (manufactured by ESPEC, Inc.) which is used as an accelerated life testing device, the durability test was conducted in such a way that a sample was introduced into an environment of 105° C./100% RH for 96 hours, followed by allowing to stand at a normal temperature for about 24 hours. The water vapor transmission rate of the sample after having been allowed to stand at a normal temperature was measured according to such a water vapor transmission rate measuring method as mentioned above to determine a water vapor transmission rate after the durability test.

(69) With respect to the functional films related to Examples 1 to 4 and Comparative Examples 1 to 5, their forming conditions and water vapor transmission rates prior to and after the durability test are described below.

Example 1

(70) In Example 1, a substrate made of a polyimide (PI) was used as a polymer substrate. A 10 nm thick ALD film made of Al.sub.2O.sub.3 was formed on the PI substrate as a functional layer. A Ta.sub.2O.sub.5 film was formed on the ALD film for 30 seconds by a sputtering process to form a 5 nm thick overcoat layer thereby obtaining a functional film of Example 1. The water vapor transmission rates (WVTR) of the resulting functional film were measured prior to and after the durability test and were found to be 0.01 [g/m.sup.2/day] prior to the durability test and 1.03 g [g/m.sup.2/day] after the durability test.

Example 2

(71) In Example 2, a functional film was prepared under the same conditions as in Example 1 except that the film-forming time of the Ta.sub.2O.sub.5 film used in the sputtering process was set at 1 minute to form a 10 nm thick overcoat layer. The water vapor transmission rates (WVTR) of the resulting functional film were measured prior to and after the durability test and found to be 0.003 [g/m.sup.2/day] prior to the durability test and 0.5 g [g/m.sup.2/day] after the durability test.

Example 3

(72) In Example 3, a functional film was prepared under the same conditions as in Example 1 except that the film-forming time of the Ta.sub.2O.sub.5 film used in the sputtering process was set at 2 minutes to form a 20 nm thick overcoat layer. The water vapor transmission rates (WVTR) of the resulting functional film were measured prior to and after the durability test and found to be 0.0006 [g/m.sup.2/day] prior to the durability test and 0.1 g [g/m.sup.2/day] after the durability test.

Example 4

(73) In Example 4, a substrate made of polyethylene terephthalate (PET) was used as a polymer substrate. An ALD layer made of Al.sub.2O.sub.3 was formed on the PET substrate as a functional layer. A Ta.sub.2O.sub.5 film was formed by a sputtering process for 2 minutes to form a 20 nm thick overcoat layer thereby obtaining a functional film of Example 4. The water vapor transmission rate (WVTR) of the resulting functional film was measured prior to the durability test and found to be 0.0005 [g/m.sup.2/day].

Comparative Example 1

(74) In Comparative Example 1, a 10 nm thick ALD film made of Al.sub.2O.sub.3 was formed on a PI substrate as a functional layer. No Ta.sub.2O.sub.5 film serving as an overcoat layer was formed. The water vapor transmission rates of the resulting film prior to and after the durability test were measured and found to be 0.04 [g/m.sup.2/day] prior to the durability test and 1.21 [g/m.sup.2/day] after the durability test.

Comparative Example 2

(75) In Comparative Example 2, a 5 nm thick Ta.sub.2O.sub.5 film was formed on a PI substrate without formation of a functional layer. The water vapor transmission rate of the resulting film prior to the durability test was measured and found to be 1.02 [g/m.sup.2/day] which was substantially the same value as a water vapor transmission rate of the PI substrate alone which was 1.09 [g/m.sup.2/day].

Comparative Example 3

(76) In Comparative Example 3, a 10 nm thick Ta.sub.2O.sub.3 film was formed on a PI substrate without formation of a functional layer. The water vapor transmission rates of the resulting film prior to and after the durability test, were measured and found to be 0.59 [g/m.sup.2/day] prior to the durability test and 0.91 [g/m.sup.2/day] after the durability test.

Comparative Example 4

(77) In Comparative Example 4, a 20 nm thick Ta.sub.2O.sub.5 film was formed on a PI substrate without formation of a functional layer. The water vapor transmission rates of the resulting film prior to and after the durability test were measured and found to be 0.49 [g/m.sup.2/day] prior to the durability test and 0.76 [g/m.sup.2/day] after the durability test.

Comparative Example 5

(78) In Comparative Example 5, a substrate made of polypropylene (PP) was used as a polymer substrate. An ALD film made of Al.sub.2O.sub.3 was formed on the PP substrate as a functional layer. A Ta.sub.2O.sub.5 film was formed on the ALD film by a sputtering process for 2 minutes to form a 20 nm thick overcoat layer thereby obtaining a film related to Comparative Example 5. The thus obtained film was subjected to measurement of a water vapor transmission rate (WVTR) prior to the durability test, with a value of 0.30 [g/m.sup.2/day].

(79) In Table 1, the results of evaluation of Examples 1 to 4 and Comparative Examples 1 to 5 are shown.

(80) TABLE-US-00001 Functional After layer dura- (ALD Overcoat bility film) layer Initial test Film (Film WVTR WVTR thickness: thickness: (g/m.sup.2/ (g/m.sup.2/ Substrate 10 nm 10 nm) day) day) Example 1 PI Al.sub.2O.sub.3 Ta.sub.2O.sub.5 (5) 0.01 1.03 Example 2 PI Al.sub.2O.sub.3 Ta.sub.2O.sub.5 (10) 0.003 0.5 Example 3 PI Al.sub.2O.sub.3 Ta.sub.2O.sub.5 (20) 0.0006 0.1 Example 4 PET Al.sub.2O.sub.3 Ta.sub.2O.sub.5 (20) 0.0005 — Comparative PI Al.sub.2O.sub.3 nil 0.04 1.21 Example 1 Comparative PI nil Ta.sub.2O.sub.5 (5) 1.02 — Example 2 Comparative PI nil Ta.sub.2O.sub.5 (10) 0.59 0.91 Example 3 Comparative PI nil Ta.sub.2O.sub.5 (20) 0.49 0.76 Example 4 Comparative PP Al.sub.2O.sub.3 Ta.sub.2O.sub.5 (20) 0.30 — Example 5

(81) As shown by the results of Examples 1 to 4, it has been confirmed that the water vapor transmission rates were remarkably lowered by forming the functional layer on the substrate by the ALD process and also forming the overcoat layer on the functional layer in comparison with the cases where the functional layer alone is formed on the substrate (Comparative Example 1) and where the Ta.sub.2O.sub.5 film alone is formed on the substrate (Comparative Examples 2 to 4). In Example 1 wherein the thickness of the overcoat layer is 5 nm, the gas barrier properties after the durability test, increase up to the same level of water vapor transmission rate as with the substrate. In Examples 2 and 3 wherein the thicknesses of the overcoat layers are, respectively, 10 nm and 20 nm, the water vapor transmission rates after the durability test are suppressed from increasing. Thus, it has been confirmed that when the thickness of the overcoat layer is made larger than 5 nm, the functional film can be suppressed from being deteriorated.

(82) As will be seen from the comparison between Examples 3 and 4 and Comparative Example 5, where the propylene substrate, which cannot adsorb the precursor of the functional layer, was used, the water vapor transmission rate could not be adequately lowered even with the case that the overcoat layer is formed on the functional layer. Accordingly, it has been confirmed that it is important that functional groups (adsorption sites) capable of adsorbing a precursor be present on the substrate surface, on which an ALD film is stacked.

(83) <Summary>

(84) As stated hereinbefore, according to the laminate of the present invention, an atomic layer deposition film is formed on an organic polymer substrate, followed by forming an overcoat layer (OC layer) by a physical vapor phase growth process or a chemical vapor phase growth process. In doing so, the water vapor transmission rate can be remarkably lowered in comparison with the case using a functional layer alone, and the water vapor transmission rate after the durability test can be suppressed from being deteriorated to a level similar to that of a substrate.

(85) The embodiments of the laminate related to the present invention have been set forth using water vapor transmission rates as an index with respect to its superiority and are described in detail with reference to the figures. The specific configuration of the present invention should not be construed as limited to the content of such embodiments as described before and changes in design without departing from the concept of the present invention should be made as included within the scope of the present invention. More particularly, the techniques described in the present invention is directed not only to a gas barrier laminate, but also to an inorganic film formed on an organic polymer substrate, for which emphasis should be placed on applicability to all types of laminates that are required to have durability against an environmental stress, such as high temperature, high humidity, exposure to light or the like, under which the functional layer mainly undergoes chemical changes and is deteriorated.

INDUSTRIAL APPLICABILITY

(86) As will be seen from the above, the laminate of the present invention can be utilized not only for electronic parts such as electroluminescent devices (EL devices), liquid crystal displays, semiconductor wafers and the like, but also effectively as a packaging film of medicinal products, foods and the like and a packaging film of precision parts.

REFERENCE SIGNS LIST

(87) 1 Laminate; 2 Substrate; 3 Functional layer (ALD film); 4 Overcoat layer (OC layer); 10 Unwinding chamber; 11 Unwinding unit; 20 First film-forming chamber; 21, 21′ Precursor regions; 22, 22′ Purge regions; 23 Reaction region; 30 Second film-forming chamber; 31 Main roll; 32 Starting material feed unit; 33 Film composition