KR102329450B1 - Temperature sensitive adhesive - Google Patents

Abstract

(Project) To provide a temperature-sensitive adhesive capable of temporarily fixing a workpiece in a stable state and capable of easily peeling the workpiece.
(Solution Means) It contains a branched-chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature above the melting point, and has a storage modulus (G') of 1×10 ⁶ Pa at 23°C or more and less than 45°C or higher, and also the pressure-sensitive adhesive of gamonseong storage modulus (G ') is ^{1 × 10 4 ~5 × 10 4} Pa in more than 60 ℃. The branched crystalline polymer is at least a copolymer of (meth)acrylate having a linear alkyl group having 22 or more carbon atoms and (meth)acrylate having an alkyl group having 2 to 8 carbon atoms, and the linear alkyl group having 22 or more carbon atoms is a copolymer. It is preferable that the (meth)acrylate having the monomer component is contained in a proportion of 50% by weight or more.

Description

Temperature-sensitive adhesive {TEMPERATURE SENSITIVE ADHESIVE}

The present invention relates to a temperature-sensitive adhesive that can be used as a temporary fixing material.

Temporarily fixed materials are used in the manufacturing process of multilayer ceramic capacitors, etc., but conventional temporarily fixed materials are prone to brittleness due to heat generation during dicing, and the cutting precision is poor because misalignment or depression of the workpiece occurs during cutting. In order to solve this problem, the temporarily fixed material is required to be able to temporarily fix the workpiece in a stable state.

Moreover, it is also calculated|required that a to-be-processed object can be easily peeled from a temporarily fixed material. As a specific example, wax is known as a temporarily fixing material (for example, refer patent document 1).

However, since the fixing power of wax is difficult to decrease, if the workpiece is temporarily fixed with wax, it is difficult to peel the workpiece, and furthermore, since wax remains on the peeled workpiece, a cleaning step is also required.

Japanese Patent Laid-Open No. 6-69324

An object of the present invention is to provide a temperature-sensitive adhesive capable of temporarily fixing a workpiece in a stable state and capable of easily peeling the workpiece.

The thermosensitive adhesive of the present invention contains a side chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature above the melting point, and has a storage elastic modulus (G') of 1×10 at 23°C or higher and lower than 45°C. ⁶ and Pa or more, and also 1 × 10 storage modulus (G ') in more than ^{60 ℃ 4 ~5 × 10 4 Pa} .

ADVANTAGE OF THE INVENTION According to this invention, a to-be-processed object can be temporarily fixed in a stable state, and there exists an effect that a to-be-processed object can be peeled easily.

BRIEF DESCRIPTION OF THE DRAWINGS It is a graph which shows the measurement result of the storage elastic modulus (G') in an Example.

<Temperature Sensitive Adhesive>

Hereinafter, a temperature-sensitive adhesive according to an embodiment of the present invention will be described in detail.

The thermosensitive adhesive of this embodiment contains a side chain crystalline polymer. The branched crystalline polymer is a polymer having a melting point. The melting point is the temperature at which a specific part of the polymer, which was initially adjusted to an ordered arrangement by a certain equilibrium process, becomes disordered, and a value obtained by measuring it with a differential thermal scanning calorimeter (DSC) at 10°C/min. to mean

The branched-chain crystalline polymer crystallizes at a temperature below the melting point described above, and exhibits fluidity by undergoing a phase change at a temperature above the melting point. That is, the branched-chain crystalline polymer has temperature sensitivity that reversibly causes a crystalline state and a fluid state in response to a temperature change. As a result, when the temperature of the thermosensitive adhesive is set to a temperature equal to or higher than the melting point and the side chain crystalline polymer is flowed, the thermosensitive adhesive follows the fine uneven shape existing on the surface of the adherend. Then, when the temperature-sensitive adhesive in this state is cooled to a temperature below the melting point, the side chain crystalline polymer crystallizes to exhibit a so-called anchor effect, and as a result, the adherend can be temporarily fixed with high fixing force. In addition, when the temperature-sensitive adhesive is heated to a temperature equal to or higher than the melting point, the cohesive force of the temperature-sensitive adhesive decreases due to the side chain crystalline polymer exhibiting fluidity. . Therefore, the temperature-sensitive adhesive of the present embodiment can temporarily fix a workpiece by using the same method as wax.

The temperature-sensitive adhesive of the present embodiment has a side chain at a ratio that can temporarily fix a workpiece when the temperature is set to a temperature above the melting point and then to a temperature below the melting point, in other words, when the side chain crystalline polymer is changed from a fluid state to a crystalline state. It contains a crystalline polymer. That is, the thermosensitive adhesive of this embodiment contains a side chain crystalline polymer as a main component.

The temperature-sensitive adhesive of this embodiment has a storage elastic modulus (G') of 1×10 ⁶ Pa or more at 23° C. or more and less than 45° C., preferably 1×10 ^{6 to} 1×10 ⁸ Pa, and 60° C. or more; Preferably, the storage elastic modulus (G') in 60-100 degreeC is 1x10 ⁴ - 5x10 ⁴ Pa. According to such a structure, a to-be-processed object can be temporarily fixed in a stable state, and a to-be-processed object can be peeled easily. Specifically, when, for example, the temperature-sensitive adhesive of the present embodiment is used as a temporarily fixed material in the manufacturing process of a multilayer ceramic capacitor, the temperature-sensitive adhesive becomes about 40°C due to heat generation during dicing. Since the temperature-sensitive adhesive of this embodiment has a storage elastic modulus (G') of 1×10 ⁶ Pa or more at 23°C or more and less than 45°C, it can maintain a high elastic modulus with respect to heat generation during processing, and It can suppress that a temperature-sensitive adhesive becomes brittle. As a result, it is possible to suppress the occurrence of misalignment or depression of the workpiece during cutting, and the cutting precision can be improved. In addition, since the temperature-sensitive adhesive of the present embodiment has a storage elastic modulus (G') of 1×10 ^{4 to} 5×10 ⁴ Pa at 60° C. or higher, when the heat-sensitive adhesive is heated at 60° C. or higher, the cohesive force of the heat-sensitive adhesive decreases Since it falls sufficiently, a to-be-processed object can be peeled easily. Moreover, generation|occurrence|production of the so-called adhesive residue in which the temperature-sensitive adhesive remains on the peeled to-be-processed object can also be suppressed.

Storage elastic modulus (G') is a value obtained by measuring by the measuring method described in the Example mentioned later. The storage modulus (G') can be adjusted, for example, by changing the composition of the side chain crystalline polymer or the like.

The branched crystalline polymer is preferably a copolymer of at least (meth)acrylate having a linear alkyl group having 22 or more carbon atoms and (meth)acrylate having an alkyl group having 2 to 8 carbon atoms. (meth)acrylate shall mean an acrylate or a methacrylate.

As for the (meth)acrylate which has a C22 or more linear alkyl group, the C22 or more linear alkyl group functions as a side chain crystalline site|part in a side chain crystalline polymer. That is, the side chain crystalline polymer is a comb-shaped polymer having a linear alkyl group having 22 or more carbon atoms in the side chain, and crystallizes by matching the side chains in an orderly arrangement by intermolecular force or the like.

As (meth)acrylate which has a C22 or more linear alkyl group, behenyl (meth)acrylate etc. are mentioned, for example. Only 1 type may be used for the (meth)acrylate which has a C22 or more linear alkyl group, and may use 2 or more types together. Although the upper limit of carbon number is preferably 50, it is not limited to this. The (meth)acrylate having a linear alkyl group having 22 or more carbon atoms is preferably contained in the monomer component in a proportion of 50% by weight or more, more preferably 50 to 75% by weight. It is preferable that the (meth)acrylate having a linear alkyl group having 22 or more carbon atoms is contained in the monomer component in a larger proportion than the (meth)acrylate having an alkyl group having 2 to 8 carbon atoms.

The (meth)acrylate which has a C2-C8 alkyl group functions as an aggregation component in a side chain crystalline polymer. When the (meth)acrylate which has a comparatively long alkyl group of C2-C8 is included as a monomer component, there exists a tendency for the peelability at high temperature to improve.

As (meth)acrylate which has a C2-C8 alkyl group, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate etc. are mentioned, for example. The illustrated (meth)acrylate may use only 1 type and may use 2 or more types together. The (meth)acrylate having an alkyl group having 2 to 8 carbon atoms is contained in the monomer component in a proportion of preferably 50 wt% or less, more preferably 20 to 45 wt%.

The monomer component may contain the above-mentioned (meth)acrylate and the other monomer copolymerizable. As another monomer, a polar monomer etc. are mentioned, for example.

Examples of the polar monomer include ethylenically unsaturated monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; and ethylenically unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate and 2-hydroxyhexyl (meth)acrylate. As for the illustrated polar monomers, only 1 type may be used and may use 2 or more types together. The polar monomer is preferably contained in the monomer component in a proportion of 10 wt% or less, more preferably 1 to 10 wt%.

A preferable composition of the branched crystalline polymer is 50 to 75 wt% of behenyl acrylate, 20 to 45 wt% of butyl acrylate, and 5 wt% of 2-hydroxyethyl acrylate.

Examples of the polymerization method of the monomer component include a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method. In the case of employing the solution polymerization method, the monomer component and the solvent are mixed, a polymerization initiator, a chain transfer agent, etc. are added as necessary, and what is necessary is just to react for about 2 to 10 hours at about 40-90 degreeC while stirring.

The weight average molecular weight of the side chain crystalline polymer is preferably 100000 or more, more preferably 300000 to 90000, still more preferably 400000 to 700000. The weight average molecular weight is a value obtained in terms of polystyrene measured by gel permeation chromatography (GPC).

The melting point of the branched crystalline polymer is preferably 45°C or more and less than 60°C. Melting|fusing point can be adjusted by changing the composition etc. of a monomer component.

The thermosensitive adhesive of this embodiment may contain the crosslinking agent further. As a crosslinking agent, a metal chelate compound, an aziridine compound, an isocyanate compound, an epoxy compound, etc. are mentioned, for example.

The crosslinking agent is preferably contained in an amount of 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the side chain crystalline polymer.

A crosslinking reaction can be performed by adding a crosslinking agent to a temperature-sensitive adhesive, and then heating. As heating conditions, the temperature is about 90-110 degreeC, and the time is about 1 to 20 minutes.

The thermosensitive adhesive of this embodiment mentioned above can be used as a temporarily fixing material for ceramic component manufacture, for example. Examples of the ceramic component include a multilayer ceramic capacitor, a ceramic inductor, and a ceramic varistor.

The use form of the thermosensitive adhesive is not specifically limited, For example, you may use as it is, and as demonstrated below, you may use it in forms, such as an adhesive sheet and an adhesive tape.

<Temperature-sensitive adhesive sheet>

The temperature-sensitive adhesive sheet of this embodiment contains the above-mentioned temperature-sensitive adhesive, and is in the form of a base material-less sheet. The thickness of the temperature-sensitive adhesive sheet is preferably 10 to 400 µm.

A release film may be laminated on the surface of the temperature-sensitive adhesive sheet. As a release film, what apply|coated release agents, such as silicone, to the surface of the film which consists of polyethylene terephthalate etc. are mentioned, for example. The thickness of the release film is preferably 5 to 500 µm, more preferably 25 to 250 µm. The release film is peeled off at the time of use of the temperature-sensitive adhesive sheet.

<Temperature Sensitive Adhesive Tape>

The thermosensitive adhesive tape of this embodiment is equipped with the film-form base material, and the adhesive layer laminated|stacked on at least single side|surface of the base material. A film form is not limited to a film form, As long as the effect of this embodiment is not impaired, it is a concept also including a film form or a sheet form.

As a constituent material of the base material, for example, polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, poly Synthetic resins, such as vinyl chloride, are mentioned.

The structure of the base material may be either a single-layer structure or a multi-layer structure. The thickness of the substrate is preferably 5 to 500 µm, more preferably 25 to 250 µm. Since the base material improves the adhesiveness to an adhesive layer, the surface treatment may be given. Examples of the surface treatment include corona discharge treatment, plasma treatment, blast treatment, chemical etching treatment, primer treatment and the like.

The pressure-sensitive adhesive layer laminated on at least one side of the substrate contains the above-described temperature-sensitive pressure-sensitive adhesive. In order to laminate the pressure-sensitive adhesive layer on at least one side of the substrate, for example, a solvent is added to the temperature-sensitive adhesive to prepare a coating solution, and the obtained coating solution is applied to one or both sides of the substrate with a coater or the like and dried. Examples of the coater include a knife coater, a roll coater, a calendar coater, a comma coater, a gravure coater, and a rod coater.

The thickness of the pressure-sensitive adhesive layer is preferably 5 to 60 µm, more preferably 10 to 60 µm, still more preferably 10 to 50 µm.

In the case of laminating the pressure-sensitive adhesive layer on both surfaces of the substrate, the pressure-sensitive adhesive layer on one side and the pressure-sensitive adhesive layer on the other side may have the same or different thickness, composition, and the like. In addition, as long as the adhesive layer on one side consists of the above-mentioned temperature-sensitive adhesive, the adhesive layer on the other side is not specifically limited. The pressure-sensitive adhesive layer on the other surface may be formed of, for example, a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include a natural rubber adhesive, a synthetic rubber adhesive, a styrene-butadiene latex base adhesive, and an acrylic adhesive.

You may laminate|stack a release film on the surface of a temperature-sensitive adhesive tape. Examples of the release film include those exemplified in the above-mentioned temperature-sensitive adhesive sheet. The release film is peeled off upon use of the temperature-sensitive adhesive tape.

<Method for manufacturing ceramic parts/Method for manufacturing multilayer ceramic capacitor>

Next, a method for manufacturing a ceramic component and a method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention will be described. The manufacturing method of the ceramic component of this embodiment is equipped with the process of the following (a)-(iv) while using the above-mentioned temperature-sensitive adhesive tape. In addition, the manufacturing method of the multilayer ceramic capacitor of this embodiment is further equipped with the following process (v).

(i) A temperature-sensitive adhesive tape is interposed between the ceramic green sheet laminate and the pedestal in a state where the pressure-sensitive adhesive layer is directed to the ceramic green sheet laminate.

(ii) After the temperature of the thermosensitive adhesive tape is set to a temperature higher than or equal to the melting point, the temperature is lower than the melting point, and the ceramic green sheet laminate is temporarily fixed to the pedestal through the thermosensitive adhesive tape.

(iii) The ceramic green sheet laminate is cut to form a plurality of green chips.

(iv) The temperature of the temperature-sensitive adhesive tape is set to a temperature equal to or higher than the melting point, and a plurality of raw chips are peeled from the temperature-sensitive adhesive tape.

(v) The obtained raw chip is fired to obtain a ceramic chip, and an external electrode is formed on the end face of the ceramic chip to obtain a multilayer ceramic capacitor.

Among the steps (a) to (v) described above, the step (iii) is so-called dicing. According to this embodiment, from the point of using the above-mentioned temperature-sensitive adhesive tape, sufficient fixing force can be maintained from room temperature (23 degreeC) to the temperature (about 40 degreeC) of the dicing in the process of (iii). In addition, in the step (iii), even if the temperature-sensitive adhesive reaches about 40°C due to heat generated during dicing, it is possible to suppress the pressure-sensitive adhesive layer from becoming brittle, and the ceramic green sheet laminate can be cut with excellent cutting precision. can In the step (iv), if the temperature of the thermosensitive adhesive tape is set to a temperature higher than the melting point, the fixing force of the thermosensitive adhesive tape is sufficiently reduced, so that a plurality of raw chips can be smoothly peeled from the thermosensitive adhesive tape, and as a result, a ceramic with good yield. Components and multilayer ceramic capacitors can be obtained. It is preferable to perform the process of (iv) at 60-80 degreeC.

In the ceramic green sheet laminate in the step (i), a ceramic green sheet is formed by thinly extending a slurry of ceramic powder with a doctor blade, and after printing a plurality of electrodes on the surface of the ceramic green sheet, a plurality of obtained by stacking and integrating ceramic green sheets of

As a method of fixing the temperature-sensitive adhesive tape to the pedestal in the step (ii), for example, a method of fixing the temperature-sensitive adhesive tape by interposing a predetermined adhesive or adhesive between the base material and the pedestal, an adsorption mechanism, etc. A method of employing a pedestal provided with fixing means and the like are enumerated. In addition, when the configuration of the temperature-sensitive adhesive tape is a double-sided tape in which adhesive layers are laminated on both sides of the substrate, it can be fixed to the pedestal through the adhesive layer on the other side opposite to the adhesive layer on one side to which the ceramic green sheet laminate is fixed. have.

The cutting in the step (iii) is not particularly limited as long as the ceramic green sheet laminate can be cut into a plurality of raw chips, and may be crushed by a cutting blade or may be cut by a rotary blade.

The manufacturing method of the ceramic component of this embodiment can be applied also to other ceramic components, such as a ceramic inductor and a ceramic varistor, in addition to the multilayer ceramic capacitor mentioned above.

Hereinafter, the present invention will be described in detail with reference to Synthesis Examples and Examples, but the present invention is not limited only to the following Synthesis Examples and Examples.

(Synthesis Examples 1 to 4 and Comparative Synthesis Examples: Side-chain crystalline polymer)

First, the monomer shown in Table 1 was added to the reaction vessel in the ratio shown in Table 1, and the monomer mixture was obtained. The monomers shown in Table 1 are as follows.

C22A: behenyl acrylate

C4A: butyl acrylate

HEA: 2-hydroxyethyl acrylate

Next, 0.5 parts by weight of "Perbutyl ND" manufactured by NOF Corporation as a polymerization initiator based on 100 parts by weight of the monomer mixture, and ethyl acetate in a ratio of 230 parts by weight based on 100 parts by weight of the monomer mixture were added to the reaction vessel, respectively, and the mixture was prepared got it

Then, each monomer was copolymerized by stirring the obtained mixture at 55°C for 4 hours to obtain a side chain crystalline polymer. Table 1 shows the weight average molecular weight and melting point of the obtained side chain crystalline polymer. In addition, a weight average molecular weight is the value which carried out polystyrene conversion of the measured value obtained by measuring by GPC. Melting|fusing point is the value measured using DSC under the measurement conditions of 10 degreeC/min.

Monomer component ^{1 )}
(weight%)
weight average molecular weight
Melting point (℃)
C22A C4A HEA Synthesis Example 1 50 45 5 650000 46 Synthesis Example 2 55 40 5 650000 49 Synthesis Example 3 60 35 5 600000 52 Synthesis Example 4 70 25 5 500000 55 Comparative Synthesis Example 45 50 5 600000 43

1) C22A: behenyl acrylate, C4A: butyl acrylate, HEA: 2-hydroxyethyl acrylate

[Examples 1-4 and Comparative Examples]

<Production of temperature-sensitive adhesive tape>

Each of the side chain crystalline polymers obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples was used to prepare temperature-sensitive adhesive tapes according to Examples 1 to 4 and Comparative Examples, respectively. The relationship between the side chain crystalline polymers obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples and Examples 1 to 4 and Comparative Examples is as follows.

Example 1: Synthesis Example 1 (C22A: 50% by weight)

Example 2: Synthesis Example 2 (C22A: 55% by weight)

Example 3: Synthesis Example 3 (C22A: 60% by weight)

Example 4: Synthesis Example 4 (C22A: 70% by weight)

Comparative Example: Comparative Synthesis Example (C22A: 45 wt%)

Preparation of the temperature-sensitive adhesive tape was performed as follows. First, a crosslinking agent was mixed in a ratio of 2.5 parts by weight with respect to 100 parts by weight of each side chain crystalline polymer obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples to obtain a temperature-sensitive adhesive. In addition, the crosslinking agent is Nippon Polyurethane Industry Co., Ltd. The produced isocyanate compound "Coronate L-45E" was used.

Next, the obtained thermosensitive adhesive was adjusted with ethyl acetate so that solid content concentration might be set to 30 weight%, and the coating liquid was obtained. The obtained coating liquid was apply|coated to the single side|surface of the film-form base material which consists of polyethylene terephthalate with a thickness of 100 micrometers. And the crosslinking reaction was performed on the conditions of 100 degreeC x 10 minutes, and the temperature-sensitive adhesive tape in which the adhesive layer with a thickness of 40 micrometers was laminated|stacked on the single side|surface of the base material was obtained.

<Evaluation>

About each temperature-sensitive adhesive tape obtained in Examples 1-4 and the comparative example, the storage elastic modulus (G') was measured. While the measuring method is shown below, the result is shown in FIG.

(Storage modulus (G'))

Using the dynamic viscoelasticity measuring apparatus "HAAKE MARS III" manufactured by Thermo Scientific, it was measured at 1 Hz, 5°C/min, and in a temperature increase process of 0 to 200°C.

As is clear from Fig. 1, in Examples 1 to 4, the storage modulus (G') at 23°C or higher and lower than 45°C is 1×10 ⁶ Pa or higher, and the storage modulus (G) at 60°C or higher. ') was 1×10 ^{4 to} 5×10 ⁴ Pa. When the temperature-sensitive adhesive tapes according to Examples 1 to 4 are used as temporary fixing materials, it can be expected that the workpiece can be temporarily fixed in a stable state and that the workpiece can be easily peeled off.

Claims (10)

It contains a branched crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature above the melting point, and has a storage elastic modulus (G') of 1×10 ⁶ Pa or more at 23° C. or higher and lower than 45° C., and The storage modulus (G') at 60°C or higher is 1×10 ^{4 to} 5×10 ⁴ Pa,
The branched crystalline polymer is a copolymer of (meth)acrylate having a linear alkyl group having at least 22 carbon atoms and (meth)acrylate having an alkyl group having 2 to 8 carbon atoms,
The temperature-sensitive adhesive in which the (meth)acrylate having a linear alkyl group having 22 or more carbon atoms is contained in a monomer component in a larger proportion than the (meth)acrylate having an alkyl group having 2 to 8 carbon atoms. The method of claim 1,
The temperature-sensitive adhesive comprising the (meth)acrylate having a linear alkyl group having 22 or more carbon atoms in a proportion of 50% by weight or more in the monomer component. delete The method of claim 1,
The temperature-sensitive adhesive having a melting point of 45°C or higher and less than 60°C. The method of claim 1,
A temperature-sensitive adhesive for the manufacture of ceramic parts. 6. The method of claim 5,
The temperature-sensitive adhesive wherein the ceramic component is a multilayer ceramic capacitor. A thermosensitive adhesive sheet comprising the thermosensitive adhesive according to claim 1 . a substrate on the film;
A temperature-sensitive adhesive tape having a pressure-sensitive adhesive layer laminated on at least one side of the substrate and comprising the pressure-sensitive adhesive according to claim 1. A step of interposing the temperature-sensitive adhesive tape according to claim 8 between the ceramic green sheet laminate and the pedestal while facing the pressure-sensitive adhesive layer on the ceramic green sheet laminate;
a step of setting the temperature of the temperature-sensitive adhesive tape to a temperature above the melting point and then lowering the temperature below the melting point, and temporarily fixing the ceramic green sheet laminate to the pedestal through the temperature-sensitive adhesive tape;
cutting the ceramic green sheet laminate to form a plurality of raw chips;
and a step of setting the temperature of the temperature-sensitive adhesive tape to a temperature equal to or higher than the melting point, and peeling the plurality of raw chips from the temperature-sensitive adhesive tape. A method for producing a multilayer ceramic capacitor, wherein a raw chip obtained by the method for producing a ceramic component according to claim 9 is fired to obtain a ceramic chip, and an external electrode is formed on an end surface of the ceramic chip to obtain a multilayer ceramic capacitor.

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