KR20160029565A - Encapsulant sheet for solar cells and solar cell module comprising same - Google Patents

Abstract

The present invention relates to an encapsulant sheet for a solar cell. The encapsulant sheet of the present invention has great adhesive strength and heat resistance by comprising a polyolefin resin having a reactive functional group, a silane coupling agent, a cross-linker, and a cross-linking accelerator. Therefore, the encapsulant sheet does not cause heat curing during a process of manufacturing a sheet without inducing creep when the sheet is in contact with other parts, and thus is useful as an encapsulant sheet for a solar cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solar cell encapsulating material sheet,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell encapsulating material sheet and a solar cell module including the same. More particularly, the present invention relates to a polyolefin encapsulating material sheet having improved durability and electrical insulation properties compared with conventional solar cell encapsulating materials.

Ethylene-vinyl acetate copolymer (EVA) has been widely used as an encapsulant for solar cells for a long time. EVA is regarded as a more suitable material than other materials in terms of economy. However, problems such as the occurrence of yellowing or peeling due to long-term operation in the outdoor solar cell module have been continuously found, and recently, due to the improvement of the performance of the solar inverter, The PID (Potential Induced Degradation) phenomenon occurs, resulting in problems in terms of insulation. These phenomena are known to occur due to the generation of acetic acid from EVA for a long time. In addition, as the solar cell module with the recent frame disappearing, moisture permeability of EVA becomes a problem.

As a result, there has been a growing interest in solar cell encapsulants using polyolefin resins, such as polyethylene or polypropylene resins, which are not EVA resins, as an encapsulating material for solar cells, thereby suppressing the generation of acetic acid, thereby improving the insulation and water resistance. Particularly, when a silane coupling agent is added to a polyolefin resin, since it is excellent in adhesion to other parts such as glass even if it is not subjected to a curing process like EVA, a thermosetting step is unnecessary and productivity can be improved and manufacturing cost can be lowered.

As an example of such a polyolefin-based sealing material, a sealing material sheet produced by using a modified polyethylene resin copolymerized with an alkoxysilane, or by adding a silane compound to an? -Olefin copolymer has been developed. However, the conventional polyolefin-based encapsulant does not undergo a thermal curing process and thus has a problem that a creep phenomenon occurs when it is adhered to other parts.

In order to solve this problem, there has been proposed a technique for improving the heat resistance by adding a crosslinking agent to a polyethylene-based resin to prepare a sheet in a heat-crosslinked form. However, in order to produce a sheet in a heat-crosslinked form, the sheet forming temperature must be lowered to a level of 100 DEG C similar to that of a conventional EVA sealing material. To achieve this, the melt flow rate (MFR) The restriction is required to be 15 g / 10 min or more in the standard. In addition, a thermosetting process is required in the solar cell module manufacturing process. In order to obtain the gelation degree of the conventional EVA encapsulant, a thermosetting process for a considerably long time is required, and the advantage of the non-thermosetting sheet is lost.

As another method, there is a method in which a sheet having already been formed is crosslinked at a certain level by irradiating it with ionizing radiation instead of thermosetting, followed by modularization. However, even in such a method, a large amount of crosslinking agent must be added for radiation crosslinking, and a separate ionizing radiation process is required after forming the sheet, which raises the manufacturing cost.

Japanese Laid-Open Patent Publication No. 2012-025946 (Feb. Japanese Laid-Open Patent Publication No. 2013-224354 (Oct. 31, 2013). Japanese Laid-Open Patent Publication No. 2014-063815 (April 4, 2014)

In the present invention, a sealing material sheet for a solar cell is provided with a high heat resistant non-crosslinked polyolefin-based encapsulant sheet which does not cause a creep phenomenon at high temperatures without thermosetting during molding, and a solar cell module containing the same.

According to one aspect of the present invention, there is provided a polyolefin resin composition comprising 100 parts by weight of a polyolefin resin having a reactive functional group; 0.5 to 5.0 parts by weight of a silane coupling agent; 0.01 to 0.1 parts by weight of a crosslinking agent; And 0.01 to 1.0 part by weight of a crosslinking aid, wherein the polyolefin resin has a melt flow rate (MFR) of 0.1 to 10 g / 10 min under conditions of 190 DEG C and 2.16 kg do.

According to another aspect of the present invention, a transparent protective substrate; A first bag material sheet; At least one solar cell connected to an electrode; A second encapsulating material sheet; And 100 parts by weight of a polyolefin resin in which at least one of the first encapsulating material sheet and the second encapsulating material sheet has a reactive functional group; 0.5 to 5.0 parts by weight of a silane coupling agent; 0.01 to 0.1 parts by weight of a crosslinking agent; And 0.01 to 1.0 part by weight of a crosslinking aid, wherein the polyolefin resin has a melt flow index of 0.1 to 10 g / 10 min under the conditions of 190 占 폚 and 2.16 kg.

The sealing material sheet has excellent appearance due to no thermal curing during the sheet forming process and has excellent adhesiveness even without a heat curing process and does not cause creep phenomenon after adhesion with other components and is useful as an encapsulating material sheet for a solar cell module Do.

Figs. 1 and 2 schematically show configurations (respectively an exploded view and a coupled view) of a solar cell module according to an embodiment including a solar cell and an encapsulating material sheet.
Fig. 3 shows an example of a creep test for evaluating the thermal stability of the sealing material sheet for a solar cell of the present invention.

The solar cell encapsulant sheet includes a polyolefin resin, a silane coupling agent, a crosslinking agent, and a crosslinking aid, and may further include other additives as required.

Hereinafter, each component will be described in detail.

The sealing material sheet comprises a polyolefin resin as a main component.

The polyolefin resin may be, for example, a polyethylene-based resin, a polypropylene-based resin, or the like.

Particularly, as the polyolefin resin, those having a reactive functional group are used. The polyolefin resin may be a polyethylene resin having a reactive functional group. As an example, the reactive functional group may be a hydrolyzable functional group. Specific examples of the reactive functional group include a halogen atom, a hydroxy group, an alkoxy group, an aryloxy group, an acyloxy group, and an alkylthio group.

Preferably, the polyolefin resin has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at 190 ° C and 2.16 kg. More preferably, the melt flow index is 1 to 5 g / 10 min. If the melt flow index of the polyolefin resin is less than 0.1 g / 10 min, molding into a sheet may not be easy, and if it exceeds 10 g / 10 min, the effect of suppressing the creep phenomenon may not be sufficient.

The polyolefin resin may be used singly or in a mixture of two or more.

A silane coupling agent is added to the sealing material sheet to improve adhesion to glass.

The silane coupling agent may react between the resin and the glass to improve the adhesion. Accordingly, the sealing material sheet can exhibit excellent adhesiveness without being subjected to a heat curing step.

The silane coupling agent may be any silane coupling agent used in conventional EVA sealing materials.

The silane coupling agent may be, for example, a vinyl silane coupling agent. Specific examples of the silane coupling agent include vinyl trichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, and mixtures thereof.

The silane coupling agent may be added in an amount of 0.5 to 5.0 parts by weight, preferably 0.5 to 2.0 parts by weight based on 100 parts by weight of the polyolefin resin.

When the addition amount of the silane coupling agent is within the above-described preferable range, a strong adhesion force can be exerted between the polyolefin sheet and the glass.

A crosslinking agent is added to the sealing material sheet for the reaction of the silane coupling agent.

Preferably, as the crosslinking agent, a radical generating agent at 100 占 폚 or higher can be used.

Particularly, it is preferable that the crosslinking agent has a half life of at least 10 hours at 100 DEG C or higher. When the half-life of the cross-linking agent is within the above-described preferable range, the curing reaction can be prevented from occurring during the sheet forming step, and the stability during mixing can be improved.

The decomposition temperature of the crosslinking agent is preferably 70 ° C or higher.

As the crosslinking agent, an organic peroxide may be used, preferably a crosslinking agent having an organic peroxide capable of generating radicals at 100 ° C or higher, and having a half-life period of 10 hours or more and a decomposition temperature of 70 ° C or higher.

Specific examples of the crosslinking agent include 2,5-dimethylhexane, 2,5-dihydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) Butyl peroxide,? -? - bis (t-butylperoxyisopropyl) benzene, n-butyl- (T-butylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, 1,1-bis Tone, benzoyl peroxide, and the like. Of these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is most preferred.

The crosslinking agent may be used singly or in a mixture of two or more.

The crosslinking agent may be added in an amount of 0.01 to 0.1 parts by weight, more preferably 0.01 to 0.05 parts by weight, based on 100 parts by weight of the polyolefin resin.

If the addition amount of the crosslinking agent is less than 0.01 part by weight, the silane agent and the crosslinking assistant may not react sufficiently with each other, resulting in poor adhesive strength or creep. When the amount exceeds 0.1 part by weight, .

A crosslinking aid is further added to the encapsulating material sheet to improve the heat resistance of the non-crosslinking polyolefin-based encapsulating material.

The crosslinking aid may have from 1 to 3 functional groups. Examples of the functional group include an allyl group, a vinyl group, and an ester group, and combinations thereof are also possible.

As the crosslinking aid, for example, a crosslinking aid used in a conventional EVA sealing material can be used.

Specific examples of the crosslinking aid include crosslinking aids having three functional groups such as triallyl isocyanurate; And a crosslinking aid having at least one functional group such as an ester.

The crosslinking aid may be used singly or in combination of two or more.

The crosslinking aid is used in an amount of more than 0 part by weight to 1.0 part by weight, for example, 0.01 to 1.0 part by weight, preferably 0.01 to 0.5 part by weight, more preferably 0.01 to 0.1 part by weight, based on 100 parts by weight of the polyolefin resin Can be added.

If the addition amount of the crosslinking improver is less than 0.01 part by weight, heat resistance is not sufficiently imparted and a creep phenomenon may occur. If the addition amount exceeds 1.0 part by weight, a curing reaction may occur during the sheet forming step, .

Further, a stabilizer may be added to the sealing material sheet in order to improve the stability of the polyolefin resin. Examples of the stabilizer include hydroquinone, hydroquinone methyl ethyl, p-benzoquinone, methylhydroquinone and the like. The stabilizer may be added to the sealing material sheet in an amount of 5 parts by weight or less, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the polyolefin resin.

In addition, a suitable amount of a coloring agent, an ultraviolet absorber, an anti-aging agent, a discoloration inhibitor or the like may be added to the encapsulating material sheet as necessary.

Examples of the colorant include inorganic pigments such as metal oxides and metal powders; And organic pigments such as azo pigments, phthalocyanine pigments, acidic or basic dye lake pigments.

Examples of the ultraviolet absorber include benzophenones such as 2-hydroxy-4-octoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone; Benzotriazoles such as 2- (2'-hydroxy-5-methylphenyl) benzotriazole; And salylates such as phenyl salylate and p-t-butylphenyl salylate.

Examples of the above-mentioned antioxidant include amines, phenols, and bisphenyls such as t-butyl-p-cresol, bis- (2,2,6,6-tetramethyl-4-piperazyl) sebacate .

The method for producing the encapsulation material sheet of the present invention is not particularly limited and can be produced by a conventional method.

For example, an encapsulating material sheet can be produced by molding the composition of the above-described components in a thickness ranging from 200 μm to 1000 μm by a T-die extrusion or calendering process.

The temperature at the time of forming the sheet may be 130 ° C to 180 ° C, more preferably 140 ° C to 160 ° C. Preferably, the sealing material sheet of the present invention does not cause a curing reaction at the sheet forming temperature.

According to another aspect of the present invention, there is provided a solar cell module including the encapsulation material sheet. Figs. 1 and 2 show the configuration (respectively an exploded view and a coupled view) of a solar cell module according to an embodiment.

1 and 2, the solar cell module 10 includes a solar cell 11 made of amorphous or polycrystalline silicon; At least one sealing material sheet (12, 12 ') laminated on at least one side of the solar cell (11); And a back sheet 13 laminated on one surface of the encapsulation material sheet 12 or 12 ', wherein the encapsulation material sheet as described above is used as at least one of the encapsulation material sheets 12 and 12' .

As a specific example, the solar cell module 10 includes a transparent protective substrate 14, a first encapsulating material sheet 12, at least one solar cell 11 connected to the electrodes, a second encapsulating material sheet 12 ' And the back sheet 13 are stacked in this order, and the above-described sealing material sheet is used as at least one of the first sealing material sheet 12 and the second sealing material sheet 12 '.

Such a solar cell module 10 may be one produced by laminating the constituent layers including the solar cell 11 and the sealing material sheets 12 and 12 'in order and then processing (heating and pressing) As the first encapsulation material sheet 12 and the second encapsulation material sheet 12 ', the encapsulation material sheet as described above can be used.

The solar cell 11, the back sheet 13, and the transparent protective substrate 14 constituting the solar cell module 10 can be suitably selected and used as commonly used ones.

Hereinafter, the present invention will be described in more detail by way of examples. The following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

The materials used in the following examples are as follows.

(a-1) a polyolefin resin having a reactive functional group: polyethylene resin having a MFR of 5 g / 10 min and a density of 0.88 g / cm 3 at 190 ° C under 2.16 kg and having a hydrolyzable functional group

(b-1) Silane coupling agent: vinyltrimethoxysilane

(c-1) Crosslinking agent: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane

(d-1) Crosslinking aid: triallyl isocyanurate

Example 1: Production of an encapsulating material sheet

Step 1) Preparation of the composition

1.5 parts by weight of the silane coupling agent (b-1), 0.01 part by weight of the crosslinking agent (c-1) and 0.01 part by weight of the crosslinking aid (d-1) were added to 100 parts by weight of the polyolefin resin (a- To prepare a composition.

Step 2) Sheet molding

The compounded composition was extrusion-molded at a temperature of 160 DEG C to prepare an encapsulating material sheet having a thickness of 450 mu m.

Examples 2 to 12 and Comparative Examples 4 to 8: Production of encapsulating material sheet

The crosslinking agent (d-1) was added to the polyolefin resin (a-1) in the same manner as in Example 1 except that the MFR of the polyolefin resin (a- To prepare a sheet.

Comparative Examples 1 to 3: Production of encapsulating material sheet

The same procedure as in Example 1 was carried out except that the amount of the crosslinking agent (c-1) to be added was changed as shown in Table 1 below and the sealing material sheet was prepared without adding the crosslinking aid (d-1).

The compositions of the encapsulating material sheets of the above Examples and Comparative Examples are summarized in Table 1 below. The content (parts by weight) of each component in Table 1 is based on 100 parts by weight of the polyolefin resin.

division MFR of polyolefin resin
(g / 10 min) Seal material Contents in sheet (parts by weight)
(Based on 100 parts by weight of polyolefin resin) Silane coupling agent Cross-linking agent Crosslinking aid Example 1 5 1.5 0.01 0.01 Example 2 5 1.5 0.01 0.05 Example 3 5 1.5 0.01 0.10 Example 4 5 1.5 0.01 0.15 Example 5 5 1.5 0.05 0.01 Example 6 5 1.5 0.05 0.05 Example 7 5 1.5 0.05 0.10 Example 8 5 1.5 0.05 0.15 Example 9 5 1.5 0.10 0.01 Example 10 5 1.5 0.10 0.05 Example 11 5 1.5 0.10 0.10 Example 12 5 1.5 0.10 0.15 Comparative Example 1 5 1.5 0.01 0 Comparative Example 2 5 1.5 0.05 0 Comparative Example 3 5 1.5 0.10 0 Comparative Example 4 5 1.5 0.001 0.05 Comparative Example 5 0.05 1.5 0.01 0.05 Comparative Example 6 11 1.5 0.01 0.05 Comparative Example 7 5 1.5 0.3 0.05 Comparative Example 8 5 1.5 0.05 1.2

The following tests were conducted on the encapsulation sheets of the above-prepared Examples and Comparative Examples.

Test Example 1: Creep Test

In order to evaluate whether or not the polyolefin resin had thermal stability at a temperature higher than the melting point of the polyolefin resin, a test was carried out with a load applied in the direction of gravity by the test method shown in Fig.

Specifically, the two glass plates 20 and 30 were adhered to each other with the sealing material sheet 12, and the glass plate 30 was moved in the oven for 12 hours at each temperature. The glass plates 20 and 30 used in the creep test were made of a smooth glass having a thickness of 3.2 t without any treatment on the surface, and the bonding area was 5 cm x 10 cm.

Test Example 2: Curing torque test

In order to determine whether or not the curing reaction occurred at the sheet forming temperature, the occurrence of the curing reaction was measured using a moving disk rheometer, and the result was evaluated according to the following criteria:

- O: no rise of torque at 60 minutes on sheet forming temperature.

- X: There is a torque increase at 60 minutes on sheet forming temperature.

The measurement results of the test examples are summarized in Table 2 below.

division Creep test by temperature condition
(Glass plate moving distance, mm) Hardening occurred
Whether 80 100 120 Example 1 0 0 4 X Example 2 0 0 4 X Example 3 0 0 3 X Example 4 0 0 2 X Example 5 0 0 4 X Example 6 0 0 3 X Example 7 0 0 2 X Example 8 0 0 2 X Example 9 0 0 2 X Example 10 0 0 2 X Example 11 0 0 2 X Example 12 0 0 One X Comparative Example 1 One 5 43 X Comparative Example 2 One 3 40 X Comparative Example 3 0 2 42 X Comparative Example 4 0 3 35 X Comparative Example 5 Sheet molding not possible Comparative Example 6 3 10 45 X Comparative Example 7 0 0 One O Comparative Example 8 0 0 3 O

As shown in Table 2, the sealing material sheets of Examples 1 to 12, to which the crosslinking agent and the crosslinking aid were added in the preferred range according to the present invention, were evaluated in creep test at the melting point (70 ° C) It is not moved at all, indicating excellent thermal stability. Further, even in the creep test under the condition of 100 占 폚 to 120 占 폚, the movement distance of the glass plate was within 5 mm and was good.

On the other hand, the encapsulation sheets of Comparative Examples 1 to 3, in which no crosslinking aid was added at all, were found to have poor thermal stability because the glass plate moved during the creep test at 100 ° C. Also, even when the crosslinking aid was added, the sealing material sheet of Comparative Example 4 in which the crosslinking agent was added to less than the preferred range of the present invention was found to have poor thermal stability as a result of a creep test.

On the other hand, in Comparative Example 5 using a polyolefin resin having an MFR of less than 0.1 g / 10 min, sheet formation was impossible.

In addition, the sealing material sheets of Examples 1 to 12, to which the crosslinking agent and the crosslinking aid were added, did not cause curing at the sheet forming temperature, but even when the crosslinking agent or the crosslinking aid was added, And 8 sealant sheets were excellent in creep performance but hardened during sheet formation, resulting in a very poor appearance of the sheet, resulting in loss of function as a product.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

10: solar cell module, 11: solar cell,
12: a first encapsulating material sheet, 12 ': a second encapsulating material sheet,
13: back sheet, 14: transparent protective substrate,
20, 30: glass plate, 100: gravity direction.

Claims (6)

100 parts by weight of a polyolefin resin having a reactive functional group;
0.5 to 5.0 parts by weight of a silane coupling agent;
0.01 to 0.1 parts by weight of a crosslinking agent; And
0.01 to 1.0 part by weight of a crosslinking aid,
Wherein the polyolefin resin has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at 190 캜 and 2.16 kg.
The method according to claim 1,
Wherein the polyolefin resin is a polyethylene-based resin having a reactive functional group.
The method according to claim 1,
Wherein the crosslinking agent has an organic peroxide capable of generating radicals at 100 占 폚 or higher and has a half life of at least 10 hours and a decomposition temperature of 70 占 폚 or higher.
The method according to claim 1,
Wherein the crosslinking aid has one to three functional groups.
5. The method according to any one of claims 1 to 4,
Wherein the sealing material sheet for a solar cell does not cause a curing reaction at a sheet forming temperature.
Transparent protective substrate;
A first bag material sheet;
At least one solar cell connected to an electrode;
A second encapsulating material sheet; And
And a back sheet laminated in this order,
100 parts by weight of a polyolefin resin in which at least one of the first encapsulating material sheet and the second encapsulating material sheet has a reactive functional group; 0.5 to 5.0 parts by weight of a silane coupling agent; 0.01 to 0.1 parts by weight of a crosslinking agent; And 0.01 to 1.0 part by weight of a crosslinking aid, wherein the polyolefin resin has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at 190 캜 and 2.16 kg.

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