JPH0152428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to filled adhesive sheets and methods of manufacturing the same. More particularly, the present invention relates to a filled adhesive sheet exhibiting improved adhesion that is effectively used in solar cell modules and a method for producing the same.

In recent years, it has been pointed out that existing energy sources, mainly oil, have been depleted, and there has been a need to develop alternative energy sources.In this context, solar power generation has been recognized as a clean energy source and as a source of inexhaustible solar radiation energy. There is a desire for its immediate practical application and widespread use. Photovoltaic power generation uses solar cells to directly convert the sun's radiant energy into electrical energy, and this function is obtained by utilizing the quantum effect of semiconductors, generally silicon semiconductors, selenium semiconductors, etc.

By the way, the functionality of silicon semiconductors deteriorates when directly exposed to the outside air, so for the purpose of protection from the outside air, we use transparent upper protective materials made of glass, acrylic resin, carbonate resin, etc., and glass, stainless steel, and aluminum. , and is protected by a lower substrate protection material made of plastic or the like. At this time, the high-performance silicon semiconductors used for solar power generation are usually wafers (small thin film pieces), so these wafers are arranged in series or parallel using interconnectors, electrically connected and fixed. Because of this need, filler adhesives are commonly used.

The physical properties required of this filling adhesive include the following.

(1) In order to prevent wafers such as silicon semiconductors from being destroyed by internal strain caused by thermal expansion and contraction, they must have elastomeric properties.

(2) Power generation is possible only after sunlight passes through the external protective material, filling adhesive, and silicon semiconductor in order, so the filling adhesive used during this time must have high sunlight transmittance. Must be.

(3) Must have good adhesion to external protective materials.

(4) Wafers made of silicon semiconductors have a small electromotive force, and therefore a useful voltage can be obtained by connecting wafers in series or parallel, so the connecting material must not corrode and have a high dielectric strength.

(5) There is no change in each of the above properties after being left outdoors for a long period of time.

Conventionally, heat-crosslinking liquid silicone resins have been used as having these properties.
This had drawbacks such as being expensive, requiring long coating and bonding steps, and being unsuitable for automation. For this reason, sheets of polyvinyl butyral resin, which has a proven track record in laminated glass, have recently begun to be used, but this is not necessarily satisfactory as a filler adhesive for solar cells. That is, a polyvinyl butyral sheet has starch or sodium bicarbonate attached to its surface to prevent blocking, and must be washed with water, dried, and conditioned before use. Furthermore, since the resin has poor fluidity, it is necessary to use an autoclave for bonding, which takes a long time and is not suitable for automation. Furthermore, in terms of quality, due to its high water absorption rate, it has poor humidity characteristics, and if left in high humidity for a long time, it will cause devitrification, which not only reduces light transmittance but also significantly reduces adhesive strength. However, a peeling phenomenon occurs at the interface between the upper transparent protective material, the lower substrate protective material, and the solar cell element. Furthermore, low-temperature properties (flexibility) are not necessarily good.

In place of polyvinyl butyral sheets, which have these problems, ethylene-vinyl acetate copolymer sheets have recently begun to be considered from the perspective of reducing the cost of solar cell modules. however,
The commonly used ethylene-vinyl acetate copolymer cannot satisfy the characteristics required as a filling adhesive for solar cells. That is,
As the vinyl acetate content increases in this copolymer, transparency and flexibility improve, but sheet formability and
Anti-blocking properties are deteriorated, it is difficult to satisfy both properties at the same time, and heat resistance and light resistance are also insufficient. Furthermore, the durable adhesiveness with the upper transparent protective material and the lower substrate protective material, which determines the reliability of the solar cell module, is also insufficient.

Furthermore, in terms of the shape of the filling adhesive sheet,
Sheets with an embossed pattern on only one side or both sides have disadvantages such as reduced workability due to insufficient anti-blocking properties and unavoidable troubles due to charging properties. In addition, these sheets are not sufficiently degassed during vacuum heating and bonding to create a solar cell module, making it impossible to avoid the problem of bubble formation. In order to avoid the formation of bubbles, it is necessary to insert a spacer such as glass fiber between the base material and the sheet, which not only complicates the bonding process but also causes uneven optical properties. There were some drawbacks, such as being able to only perform matching.

For these reasons, it was thought that a sheet with embossed patterns on both sides would be suitable; however, according to studies by the present inventors, the following problems were found in its production.

The sheets used for solar cell modules generally have a thickness of about 0.2 to 1 mm, and such sheets are usually formed using a T-die sheet forming machine or an inflation method sheet forming machine. The latter method was unsuitable due to internal blocking.

A T-die sheet forming machine usually uses a two- or three-roll take-off line, and in either case, the molten web extruded from the T-die is passed between two rolls, pressed, and cooled and solidified. It will be done. If the rolls used at this time are all metal rolls with embossed patterns, the minimum thickness of the sheet that can be practically formed is about 0.8 to 1 mm, and if the thickness is less than this, the clearance between the metal rolls will be limited. This causes problems such as being small and difficult to adjust, and there being a great risk of damage to the rolls due to contact between the two metal rolls.

For this reason, when embossing sheets with a thickness of 1 mm or less, a rubber roll is usually used as one of the lines, but sheets manufactured on this line are not embossed sufficiently on the transfer surface of the rubber roll. However, the formation of the bubbles described above was unavoidable. In addition, the transfer surface of the rubber roll is highly charged, making it easy for foreign matter to adhere to it, and furthermore, when unwinding sheets stacked in rolls or sheets or taking them out one by one, work efficiency is reduced due to blocking. was unavoidable.

Another method is to emboss both sides of the sheet using an embossing machine after forming it into a sheet, but it is also possible to use two metal rolls or one of them as a rubber roll. , the same drawbacks as above cannot be avoided.

The present inventors have conducted various studies to solve the above-mentioned defects in terms of the molding material observed in ethylene-based copolymer sheets and the above-mentioned disadvantages in the molding process observed when embossing the sheets. It has been found that a filled adhesive sheet molded from a molding material containing a polymer and an organic peroxide and which is embossed on both sides effectively achieves the desired object.

That is, such a filled adhesive sheet does not require washing, drying, and humidity control equipment like polyvinyl butyral sheets, nor does it require expensive equipment such as an autoclave, and can be bonded using inexpensive vacuum heating equipment. is possible, does not require materials for degassing such as glass cloth spacers, and is cheaper than liquid silicone resin or polypynyl butyral resin, and is a suitable bonding process for creating solar cell modules. In addition to achieving automation, shortening, and cost reduction, the embossability of the sheet performed by the forming method described below is also good. It also has the effect of preventing the contamination of foreign substances and eliminating blocking troubles.

The filled adhesive sheet has an embossed pattern preferably with a depth of 0.03 mm or more on both sides,
It is manufactured by the following method.

(1) A dry blended molding material containing an ethylene copolymer and an organic peroxide is subjected to T-treatment at a temperature at which the organic peroxide does not substantially decompose.
It is extruded as a molten web from a die extruder, and is pressed together with an embossed release paper between a cooling roll with an embossed pattern and a compression rubber roll, and is cooled and solidified to form a sheet with embossed patterns on both sides. Method (2) A dry blended molding material containing an ethylene copolymer and an organic peroxide is subjected to T-treatment at a temperature at which the organic peroxide does not substantially decompose.
It is extruded as a molten web from a die extruder, passed between a cooling roll with an embossed pattern carved on it, and a pressure bonding rubber roll, and then cooled and solidified to form a single-sided embossed sheet, and then peeled off to the non-embossed side of the single-sided embossed sheet. The papers are stacked, the surface of the web not in contact with the release paper is heated again to a temperature at which the organic peroxide does not substantially decompose, and the release paper laminated web is passed between the roll and the pressure rubber roll and pressed. , a method of forming a sheet with embossed patterns on both sides by cooling and solidifying it.

The ethylene copolymer used in the present invention has a light transmittance of about 80% or more, preferably about 90%.
As mentioned above, a suitable copolymer having an elastic modulus of about 1 to 30 MPa, preferably about 3 to 12 MPa is used. Specifically, for example, copolymers of ethylene and vinyl esters such as vinyl acetate and vinyl propionate, copolymers of ethylene and unsaturated fatty acid esters such as ethyl acrylate, butyl acrylate, and methyl methacrylate, and ethylene. and copolymers with α-olefins such as propylene, butene-1, and 4-methylpentene-1, as well as ethylene-vinyl ester-unsaturated fatty acid ternary copolymers, ethylene-unsaturated fatty acid ester-unsaturated fatty acid , terpolymer copolymers, or metal salts thereof (ionomer resins) are used.

Among these ethylene-based copolymers, the most preferred from an economic point of view is an ethylene-vinyl acetate copolymer, in which case the vinyl acetate content in the copolymer is about 20 to 40% by weight, preferably is about 25~
40% by weight is suitable. If the vinyl acetate content is less than this, the light transmittance will be low and the power generation efficiency of the module will be low, and the elasticity of the module will also be high, increasing the risk of damage to the power generation element due to thermal expansion and contraction. However, in the case where a filling adhesive sheet is pasted under the solar cell element formed on the lower surface of the upper transparent protective material, the light transmittance of that part is irrelevant, so the vinyl acetate content is approximately 20% by weight. The following ethylene-vinyl acetate copolymers can also be used. On the other hand, if the vinyl acetate content increases beyond this range, the extrusion moldability of the sheet will deteriorate, and the resulting sheet will become more sticky and prone to blocking.

The organic peroxide contained in the ethylene-based copolymer and the molding temperature at which the mixture is mixed with a light stabilizer added as necessary and formed into a sheet using an extruder, and the temperature maintained at this temperature. A material is used that does not substantially decompose over time, but rapidly decomposes at a temperature below the decomposition temperature of the ethylene copolymer during the modeling process. Generally, those having a decomposition temperature (temperature at which the half-life is 1 hour) of about 90 to 190°C, preferably about 120 to 160°C are used.

Examples of such organic peroxides include tertiary butylperoxyisopropyl carbonate, tertiary butylperoxyisopropyl carbonate,
Butyl peroxyacetate, tertiary butyl peroxybenzoate, dicumyl peroxide,
2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane-3,1 , 1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,
5-bisperoxybenzoate, tert-butyl hydroperoxide, p-menthane hydroperoxide, benzoyl peroxide, p-
Examples include chlorbenzoyl peroxide, tert-butyl peroxyisobutyrate, hydroxyheptyl peroxide, and chlorhexanone peroxide.

These organic peroxides are added in the amount necessary to crosslink the ethylene copolymer during the heating process during the bonding process of solar cell modules, improve heat resistance, and contribute to improved adhesion. added. Generally, about 100 parts by weight of ethylene copolymer
0.1 to 5 parts by weight, preferably about 0.5 to 3 parts by weight, of organic peroxide are added. If the addition ratio is less than this, transparency, heat resistance and adhesion will not be sufficient.

When stricter light resistance is required for the filled adhesive, it is preferable to add a light resistance stabilizer, such as 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy- 4-
Methoxybenzophenone, 2-hydroxy-4-
Methoxy-2'-carboxybenzophenone, 2-
Benzophenone series such as hydroxy-4-n-octoxybenzophenone, 2-(2'-hydroxy-
Benzotriazole such as 3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-5-methylphenyl)benzotriazole, 2-(2'-hydroxy-5-tert-octylphenyl)benzotriazole As light stabilizers, salicylic acid esters such as phenyl salicylate and p-octylphenyl salicylate, nickel complex salts, and hindered amines are used as light stabilizers. When these light stabilizers are used in combination with antioxidants such as hindered phenols and phosphites, a synergistic effect may be expected.

A sheet that is molded from a molding material containing an ethylene copolymer and an organic peroxide as described above and has an embossed pattern on both sides by a specific method described below is then processed as needed. Primer treatment is performed on the surface. Priming is generally accomplished by passing the embossed sheet through a bath of coupling agent to form a layer of coupling agent on the surface of the sheet.

As a coupling agent, the general formula RSiX ₃ (where R is a reactive organic group such as a vinyl group, an aminoalkyl group, a methacryloxyalkyl group, an acryloxyalkyl group, a mercaptoalkyl group, or an epoxy group, and X is a halogen atoms, alkoxy groups,
an organic silane compound represented by the general formula R′ _4-o Si
(OOR″) _o (where R′ is a vinyl group or an alkyl group, R″ is a hydrocarbon group, and n is 1 to
4 integer) or with the general formula ROTi(OYRZ) ₃ (where R
is an alkyl group, Y is a carboxyl group, a phosphate group, a pyrophosphate group, a phosphite group, or a sulfonyl group, and Z is a hydrogen atom, an amino group, a hydroxyl group, a mercapto group, an acrylic group or a methacryl group) Typical examples include organic titanate compounds.

For these coupling agents, in addition to the naturally required good adhesive function, consideration must be given to factors such as kneading and compatibility with the ethylene copolymer, odor, light resistance, non-corrosion to interconnectors, etc., and cost. you need to pay. From this point of view, preferred coupling agents include vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ
-glycidoxypropylmethoxysilane, γ-glycidoxypropyltriethoxysilane, β-
It is an organic silane compound having an unsaturated group or an epoxy group such as (3,4-epoxycyclohexyl)ethyltrimethoxysilane.

When an organosilane peroxide is used as a coupling agent, its decomposition temperature (temperature at which the half-life is 1 hour) is approximately 90 to 190°C, preferably approximately 120 to 190°C.
A temperature of 160℃ is suitable. Such organosilane peroxides include CH ₃ Si(OO-t-Bu) ₃ ,
Examples include CH ₂ =CHSi(OOR'') (where R'' is a tertiary butyl group, a cumyl group, or a p-menthyl group).

Primers containing these coupling agents are
It is used as a solution of aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, alcohols, ketones, organic solvents such as esters, water, or a mixed solvent of water and a water-soluble organic solvent. The concentration of the coupling agent in the primer is suitably about 0.1 to 10%, preferably about 0.5 to 5%, from the viewpoint of adhesive performance and economical efficiency.

It is also possible to use a filled adhesive sheet without priming, and in this case it is desirable to apply a priming treatment to the mating material to which the filled adhesive sheet is to be bonded.

Instead of priming with such a coupling agent, the same coupling agent itself can be included in the molding material together with the ethylene copolymer and the organic peroxide, and a filled adhesive sheet can be molded from the molding material. In this case, the coupling agent should be 100 parts by weight of the ethylene copolymer.
Generally about 0.1 to 10 from the point of view of economy and adhesion.
Parts by weight are used, preferably about 0.5 to 5 parts by weight. The combination of this and an organic peroxide provides stronger adhesion that is useful in practice. That is, compared to the case where only a coupling agent or an organic peroxide is used, the adhesiveness is clearly improved when these are used in combination.

The cause of this is not fully understood, but for example, when a silane coupling agent with an unsaturated group is used, the organic peroxide decomposes during heating and bonding, generating radicals in the ethylene copolymer. The majority of these polymer radicals appear to be involved in the crosslinking reaction of the ethylene copolymer resin, but the remaining part reacts with the unsaturated groups of the silane coupling agent, meaning that the coupling agent is grafted onto the ethylene copolymer resin. It is believed that this grafted coupling agent is involved in the formation of stronger adhesion.

From this point of view, instead of using an ethylene copolymer and a coupling agent, especially a silane coupling agent, a molding material that uses a silane-modified ethylene copolymer together with an organic peroxide has been considered, and in fact, it is possible to use a molding material that uses a silane-modified ethylene copolymer together with an organic peroxide. The treated sheets show even better adhesion. In this case, if a silanol catalyst such as various organometallic compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, etc. are used together with the organic peroxide, water resistance etc. can be further improved.

Silane modification of ethylene-based copolymers involves heating a silane compound, such as that described above as a coupling agent, to a temperature generally above about 140°C, preferably in the presence of a free radical-generating compound such as an organic peroxide. It is carried out by reacting.

During this reaction, some of the silane modifier may remain unreacted, but this unreacted compound is
When a silane-modified ethylene copolymer is molded into a sheet, it becomes a source of odor, but does not pose any quality problem. If necessary, this unreacted compound can be removed in advance by a well-known technique using a vented extruder or the like. Although the content of silane groups in the modified resin is not particularly limited,
Generally about 0.1 to 10% by weight, preferably about 0.3 to 10% by weight from the viewpoint of crosslinking reactivity, adhesiveness, economic efficiency, etc.
It is in the range of 3% by weight. The modified resin can also be used as a blend of a silane-modified ethylene copolymer and an unmodified ethylene copolymer,
In this case, this range of silane group content relative to the total weight of both is generally used.

The unmodified ethylene copolymer used preferably has a chemical structure that is the same as or close to the chemical structure of the silane-modified ethylene copolymer blended with it before silane modification,
Generally, an ethylene-vinyl acetate copolymer having a vinyl acetate content of about 20 to 40% by weight is used. Also, these ethylene copolymers (referring to silane-modified and unmodified ethylene copolymers)
It is preferable to use those having similar melt fluidity. This is because these similarities in chemical structure and melt flowability affect melt-kneading properties during sheet molding, as well as optical properties and adhesive properties after lamination. Generally, the unmodified ethylene copolymer is blended in a proportion of about 500 parts by weight or less per 100 parts by weight of the silane-modified ethylene copolymer.

Embossed sheet molding from molding materials using ethylene copolymers, ethylene copolymers and coupling agents, or silane-modified ethylene copolymers (hereinafter collectively referred to as ethylene copolymer resins) in combination with organic peroxides , according to the methods (1) and (2) described above, specifically as follows.

First, an ethylene copolymer resin, an organic peroxide, and if necessary a light stabilizer are dry-blended in advance using a well-known mixing device, such as a ribbon blender or a tumbler mixer, and then supplied from the hopper of an extruder. The extruder may be any type having a function of melt-kneading the dry blend at a temperature at which the organic peroxide is not substantially decomposed, and may be a commonly used single-screw extruder for polyethylene molding. The resin melt-kneaded in the extruder is introduced into a T-die heated to a temperature at which the organic peroxide does not substantially decompose, and extruded as a molten web. The T-die used here may be one that has the function of extruding the molten resin into a sheet in a molten state, and a straight manifold type T-die or the like for ordinary polyethylene molding can be used.

The molten web extruded from the T-die is formed into an embossed sheet by the method shown in Figures 1 and 2 of the drawings.

In the forming method shown in FIG. 1, a molten web 2 extruded from a T-die 1 is rolled together with an embossed release paper 4 unwound from a take-up roll 3 and a cooling roll having an embossed pattern engraved thereon. 5 and a pressure bonding rubber roll 6, the material is crimped, then passed through a secondary cooling roll 7 to be cooled and solidified, passed through a guide 8 and peeling rolls 9, 9',
A series of operations are performed in which the double-sided embossed sheet is wound onto a take-up roll 10 and the release paper is wound onto a take-up roll 11.

In the forming method shown in FIG. 2, a molten web 2 extruded from a T-die 1 is passed between a cooling roll 5 with an embossed pattern and a pressure rubber roll 6 to be crimped, and then a secondary cooling roll 7
After cooling and solidifying to form a single-sided embossed sheet 12, the embossed release paper 4 unwound from the take-up roll 3 is guided to the non-embossed side of the single-sided embossed sheet 13, 13'.
The surface of the web not in contact with the release paper is heated again using the infrared heater 15 to a temperature at which the organic peroxide does not substantially decompose, and the release paper laminated web is rolled and embossed if necessary. is passed between the roll 5' and the pressure rubber roll 6', which are engraved with A series of in-line operations are performed in which the sheet is wound onto a take-up roll 10 and the release paper is wound onto a take-up roll 11.

Note that the release paper can be peeled off from the double-sided embossed sheet immediately before use, but
If the release paper is wound onto a take-up roll as in the embodiment shown in Figure 2, it can be reused, which is advantageous in terms of cost.

The embossed pattern on both sides of the sheet is
Fine patterns such as stripes, cloth grain, satin, leather patterns, diamond lattice, and synthetic leather-like wrinkle patterns are suitable, while large patterns such as floral patterns and geometric patterns are suitable for purposes such as degassing during vacuum heating bonding. Undesirable. Regarding the size of the pattern, it is preferable that the shortest distance from the center of gravity of the part with a large area to the part with a small area in the convex or recessed part of the embossed pattern is short, and this distance is usually 10 mm.
It is preferably 2 mm or less. In addition, the depth of the groove of the embossed pattern or the clearance between the convex part and the concave part is usually 0.03 mm or less, preferably 0.1 mm or less, with respect to the sheet thickness, which is generally set to 0.1 to 1 mm from the viewpoint of cost. It is. Note that the properties of the embossed patterns on both sides of the sheet may be the same or different.

The formation of such an embossed pattern is carried out by pressing one side of the sheet with an embossed roll or a cooling roll on which an embossed pattern is engraved, as described above,
The other side is bonded to a release paper with an embossed pattern. As the embossed release paper, so-called processing paper used for synthetic leathers such as polyurethane and polyvinyl chloride is preferably used because of its good release properties. Release paper used for adhesive labels and the like is not very desirable because when it is laminated with a sheet, the peel resistance is too low and troubles tend to occur in the collection line.

Process paper that is preferably used as a release paper can be roughly divided into silicon-coated types and non-coated types, and the former is preferred in the present invention. That is, the silicon coating type generally has a structure of paper/polyethylene/silicon resin and has suitable peel resistance. The non-coated type is
The peeling surface is made of polypropylene, poly(4-methylpendene-1), etc., which is not very preferable because the peeling resistance is too high.

For embossing of process paper, use process paper that is easy to emboss (for example, Soken Processing product EV130TA-7R).
-4, EV130TA-7R-10, etc.) using an embossing machine, but the embossed pattern is not added to the already laminated process paper, but the embossed pattern is created at the so-called paper-making stage. It is also possible to use a so-called crepe paper which has been given a coating and laminate it with polyethylene and silicone resin.

The method of manufacturing the sheet of the present invention, which is carried out through the steps described above using these embossed rolls or cooling rolls with embossed patterns and embossed release paper, uses inexpensive equipment and inexpensive auxiliary materials. Therefore, it is not only possible to apply an embossed pattern with a depth of 0.03 mm or more on both sides of a thin sheet with a thickness of 0.1 to 1 mm, but also without the risk of damaging the embossing roll. Since the embossed pattern is applied, it is possible to avoid the contamination of foreign matter due to electrostatic charge and the deterioration of efficiency during lamination work due to sheet blocking. It has a number of excellent effects, such as the ability to obtain optically excellent bonded products without requiring any secondary materials.

Modularization of solar cells using the filled adhesive sheet according to the present invention can be carried out as follows.

When solar cell elements are made of silicon semiconductor or selenium semiconductor wafers, these solar cell elements are sandwiched between at least two filled adhesive sheets, and if necessary, a surfactant solution or organic solvent is applied on both sides. This is done by laminating protective materials that have been cleaned by cleaning or surface treated by corona discharge, chemicals, etc., that is, an upper transparent protective material and a lower substrate protective material, by heating and bonding them under vacuum. At this time, it is industrially preferable to bond the module by sequentially overlapping or arranging the lower substrate protective material, the filling adhesive sheet, the solar cell element, the filling adhesive sheet, and the upper transparent protective material. The battery element may be laminated in advance with at least two filled adhesive sheets made of an ethylene copolymer containing an organic peroxide, and then bonded to the upper transparent protective material and the lower substrate protective material. It is desirable that the heating be carried out until the organic peroxide added to the filled adhesive sheet is completely decomposed. Through this heat treatment, the filling adhesive and each external protective material are firmly adhered, and the solar cell element is laminated with the two filling adhesive sheets, which are also attached to the upper transparent protective material and the lower substrate protective material. A solar cell module is formed there, which is firmly bonded to the material.

In addition, solar cell elements are made of glass, plastic,
When formed on a protective material such as ceramic or stainless steel, a filled adhesive sheet is used as an intermediate layer, and a solar cell element is formed on the inward facing surface (contact surface of the filled adhesive sheet) of one of the protective materials. With the upper transparent protective material and the lower substrate protective material layered on top and bottom of the intermediate layer filling adhesive sheet, specifically, the filling adhesive sheet is placed on top of the solar cell element formed on the upper surface of the lower substrate protective material. Then, with the filling adhesive sheet and the lower substrate protective material sequentially stacked under the upper transparent protective material or the solar cell element formed on the lower surface of the upper transparent protective material, this is placed under vacuum in the same manner as in the above case. When heat bonding is performed, a solar cell module is formed in which one protective material on which a solar cell element is formed, a filling adhesive sheet, and the other protective material are firmly bonded together.

In this way, the solar cell formed by bonding by the method using the filling adhesive sheet according to the present invention has a high peel strength between the protective material and the filling adhesive, and has good peeling resistance under humid conditions. It fully satisfies all the properties required for solar cell modules, such as excellent initial adhesion and durable adhesion, little change in response to UV irradiation, and good light transmittance. It also has the effect of making it possible to automate and shorten the bonding process, but in particular, since the filling adhesive sheet is embossed, it prevents sheet blocking and prevents degassing during the solar cell modularization process. , is particularly effective.

The presence of air bubbles not only deteriorates the appearance but also reduces adhesiveness and heat resistance. That is, in the case of this filled adhesive sheet, the decomposition of organic peroxide by heating has a strong correlation with adhesiveness and heat resistance, but if air bubbles are present, the heat conduction in that part will be significantly reduced. The presence of bubbles must be avoided at all costs, as this will ultimately inhibit the decomposition of the organic peroxide.

However, the filled adhesive sheet according to the present invention,
As mentioned above, it is difficult to generate bubbles, and therefore various bonded products of good quality can be easily and continuously obtained using the vacuum heating method, compared to bonding using conventional polyvinyl butyral sheets. However, not only is the filled adhesive sheet itself inexpensive, but it also does not require equipment for cleaning, drying, or humidity conditioning the sheet, or an autoclave, so the cost is low from an equipment standpoint as well. .

Next, the present invention will be explained with reference to examples.

Example 1 Ethylene-vinyl acetate copolymer (Mitsui Polychemical product Evaflex #250, vinyl acetate content
28% by weight, melt index 15g/10 minutes) 100
(weight, same hereinafter), 1.4 parts of tert-butyl peroxybenzoate, 0.25 parts of 2-hydroxy-4-n-octylbenzophenone, and tetrakis[methylene-3-(3',5'-di-tert-butyl- 4′-Hydroxyphenyl)propionate]methane 0.1
portions were dry blended in a tumbler mixer. This dry blend was processed using a T-die extrusion molding machine (manufactured by Modern Machinery Co., Ltd., single shaft, diameter 65 mm,
Full flight meter ring type screw for polyethylene, straight manifold type T
- die) to extrude a sheet-like molten web. The resin temperature at the die exit was 95°C, and the extruder and T-die temperatures were set at 110°C or lower.
Further, the rotational speed of the screw was 30 rpm.

The molten web extruded from the T-die was embossed according to the steps shown in FIG. 1 of the above description. As the embossed release paper, embossed engineering paper (Souken Processing Products EV130TA
-7R-4, silicone coated type) was used,
This process paper is embossed with a fine wave pattern. In addition, the pattern engraved on the cooling roll is a diamond lattice, and the lattice spacing is 0.5 mm.
The depth is 0.2mm. The rubber coated on the pressure-bonding rubber roll is made of silicone rubber with Shore hardness A of 65, and its surface is polished. The sheet and release paper, which were separated from each other in the take-up line, were wound up separately using a center-drive biaxial winding machine.

A sheet with such embossed patterns on both sides had a basis weight of 670 g/m ² , and the electrostatic voltage was measured to be 0.2 KV or less. Therefore, this sheet exhibits good properties such as no charging, low unwinding resistance, and little blocking even when the sheets are stacked.

Modularization of solar cells using the filled adhesive sheet formed in this manner was carried out as follows. That is, γ-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical KBM-503) was added to an aqueous solution whose pH was adjusted to 2 to 3 with acetic acid.
A primer containing 3% by weight of the primer was coated on the surfaces to be bonded of reinforced white glass (thickness: 3 mm) and polyfluorinated vinyl sheet (Tedlar 400BS30WH, manufactured by DuPont), and the solvent was dried.

A sheet with the embossed pattern is placed on top of the tempered white glass, a plurality of silicon semiconductor wafers for solar cells are arranged in series using an interconnector, and the embossed pattern is applied again on top of the sheet. Place the prepared sheet, and then add a polyvinyl vinyl sheet and polyester film (0.5mm thick).
and aluminum plates (thickness 0.5mm) are stacked one after another,
A laminate was formed.

This laminate was placed in the lower chamber of a vacuum laminator whose degassing chamber was separated into two chambers by silicone rubber.First, the pressure in both chambers was reduced to 1 mmHg, and the vacuum laminator was placed in an oven at 30℃. When the temperature reached 120°C, the upper chamber of the vacuum laminator was returned to atmospheric pressure over 10 minutes, and during this time the temperature was further increased to 150°C and pressurized. After continuing heating and pressurizing in this state for another 1 hour, the vacuum laminator was taken out from the laminate by cooling and returning the lower chamber to atmospheric pressure, and the aluminum plate and polyester film were sequentially removed to obtain a module. .

No air bubbles were observed in this module, and there was no abnormality in the power generating element. Furthermore, regarding this module, high temperature 90℃, 4 hours - low temperature
A heat cycle test was conducted at 40°C with one cycle of 4 hours, and after 20 cycles, no abnormalities were observed in the module's appearance, including the arrangement of the power generation elements.

Example 2 Ethylene-vinyl acetate copolymer (Mitsui Polychemical product Evaflex #150, vinyl acetate content
33% by weight, melt index 30g/10 minutes) 100
parts, 2,5-dimethyl-2,5-bis, (tert-butylperoxy)hexane 1.4 parts, 2-, hydroxy-4-n-octylbenzophenone 0.25 parts,
0.1 part of bis(2,2,6,6,-tetramethyl-4-piperidine) sebacate and 0.2 part of tris(mixed mono-dinonylphenyl) phosphite were dry blended in the same manner as in Example 1.

The molten web extruded from the T-die was embossed in the same manner as in Example 1. However, as process paper, diamond lattice pattern (grid spacing 1mm, depth 0.4mm)
An embossed one was used, and a satin roll (matte depth 0.15 mm) was used as a cooling roll.

The sheet with such embossed patterns on both sides had a basis weight of 770 g/m ² , and no air bubbles were observed in the module made using this sheet in the same manner as in Example 1. There was also no abnormality in the power generation element. Furthermore, this module was subjected to a 20-cycle heat cycle test, and no abnormalities were observed in the module's appearance, including the arrangement of the power generation elements, after the test.

Example 3 In Example 2, 1.0 part of γ-methacryloxypropyltrimethoxysilane was further added and dry blended to form an embossed sheet.

The resulting sheet with embossed patterns on both sides had a basis weight of 800 g/m ² , and no air bubbles were observed in the module created using this sheet in the same manner as in Example 1. There was also no abnormality in the power generation element. Furthermore, this module was subjected to a 20-cycle heat cycle test, and no abnormalities were observed in the module's appearance, including the arrangement of the power generation elements, after the test.

Example 4 Primer of Example 1, treated tempered white glass 2
A sheet with the embossed pattern used in Example 1 on both sides as an intermediate layer was placed between the sheets, and this was placed in a vacuum laminator, and the pressure was reduced to 1 mmHg at room temperature. The mixture was placed in an open chamber at 110°C, heated to 150°C over 20 minutes, and then further heated at 150°C for 1 hour under reduced pressure. It was taken out of the oven, cooled, and then returned to atmospheric pressure.

The resulting laminated glass had a thickness of 6.4±0.1mm;
No bubbles were observed, and the light transmittance at 450nm was
It was good at 86%.

Example 5 To 100 parts of the ethylene-vinyl acetate copolymer used in Example 2, 2.0 parts of vinyltrimethoxysilane and 0.2 parts of di-tert-butyl peroxide were added,
A silane-modified ethylene-vinyl acetate copolymer (melt index: 9 g/10 minutes, 190°C) was produced by extrusion from a screw type extruder at 200°C.

When undecomposed tertiary butyl peroxide in this silane-modified copolymer was extracted with methanol and analyzed by gas chromatography, its content was found to be 0.1% by weight or less. Furthermore, when the silane groups in the copolymer were measured by ashing analysis, the content was 1.5% by weight.

A sheet using such a silane-modified ethylene-vinyl acetate copolymer instead of an unmodified ethylene-vinyl acetate copolymer and having molded embossed patterns on both sides in the same manner as in Example 1 was as follows:
The basis weight was 830 g/m ² , and no air bubbles were observed in the module made using this sheet in the same manner as in Example 1, and there was no abnormality in the power generating element. Furthermore, regarding this module,
A 20-cycle heat cycle test was conducted, but
No abnormalities were observed in the module after implementation, including the arrangement of the power generating elements.

Example 6 In Example 1, a single-sided embossed sheet was obtained as shown in FIG. 2 of the above description without using process paper. Using this single-sided embossed sheet and the process paper used in Example 1, a sheet with embossed patterns on both sides was formed by following the steps shown in FIG. 2.

The basis weight of this sheet was 650 g/m ² , and the module produced using this sheet in the same manner as in Example 1 had no air bubbles, and no abnormalities were found in the power generating element. Furthermore, a 20-cycle heat cycle test was conducted on this module, and no abnormality was observed in the module of the example in terms of its appearance, including the arrangement of the power generation elements.

Comparative Example 1 In Example 1, another ethylene-vinyl acetate copolymer (Mitsui Polychemical product Evaflex #550, vinyl acetate content 14% by weight, melt index 15g/10 minutes) was used and melted at a resin temperature of 110°C. The web was extruded to form a sheet with embossed patterns on both sides.

When a laminated glass was prepared using this sheet in the same manner as in Example 4, its light transmittance was 68%.

Comparative Example 2 In Example 1, a sheet with embossed patterns on both sides was molded without adding tertiary butyl peroxybenzoate, and this sheet was then used to form a module.

Although no air bubbles were observed in the obtained module, some ruptures were observed in the power generation element. Additionally, in the heat cycle test, the arrangement of the power generation elements was partially disordered after 20 cycles. Furthermore, it was found that the laminated glass produced in the same manner as in Example 4 had a thickness of 1.1 to 1.6 mm, and that the embossed sheet used as the interlayer film had significant fluidity.

Comparative Example 3 In Example 1, a sheet with an embossed pattern on only one side without using any embossed release paper (the depth of irregularities on the embossed surface was 0.15 to 0.2
mm, and that of the non-embossed surface is 0.03 mm or less).

When the charged voltage on the non-embossed surface of the sheet was measured, it was 0.3 to 1.8 KV, indicating that it was quite charged.
Further, when an attempt was made to unwind a portion of the sheet from the roll of the sheet, blocking occurred and unwinding was not easy. Furthermore, when a module was made using this sheet, the presence of air bubbles was observed in some of the modules.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are both schematic diagrams showing one embodiment of a method for forming a filled adhesive sheet according to the present invention. In these drawings, reference numeral 1 indicates T-die, 2
4 indicates the molten web, 4 indicates the embossed release paper, 5 indicates the roll with the embossed pattern, 6 indicates the compression rubber roll, 7 indicates the secondary cooling roll, 10 and 11 indicate the take-up roll, and 15 indicates the infrared heater, respectively. .

Claims (1)

[Claims] 1. A filled adhesive sheet for a solar cell module, which is molded from a molding material containing an ethylene copolymer and an organic peroxide, and has an embossed pattern on both sides thereof. 2. The filled adhesive sheet according to claim 1, which is provided with an embossed pattern with a depth of 0.03 mm or more. 3. The filled adhesive sheet according to claim 1, which is molded from a molding material further containing a coupling agent. 4. The filled adhesive sheet according to claim 1, which is formed by using the ethylene copolymer as a silane-modified ethylene copolymer as a molding material. 5. The filled adhesive sheet according to claim 4, which is molded from a molding material containing a silanol condensation catalyst together with an organic peroxide. 6. A filling adhesive sheet according to claim 1, which is used for a solar cell module in which a lower substrate protective material, a filling adhesive sheet, a solar cell element, a filling adhesive sheet, and an upper transparent protective material are laminated. 7. An upper transparent protective material and a lower substrate protective material in which a filled adhesive sheet was used as an intermediate layer and a solar cell element was formed on the inward surface of one of the protective materials were stacked above and below the intermediate layer filled adhesive sheet. A filled adhesive sheet according to claim 1, which is used for a solar cell module. 8 A dry blended molding material containing an ethylene copolymer and an organic peroxide is extruded as a molten web from a T-die extruder at a temperature at which the organic peroxide does not substantially decompose, and the embossed A method for producing a filled adhesive sheet for a solar cell module having an embossed pattern on both sides, the sheet being pressed together with a release paper between a cooling roll on which an embossed pattern is engraved and a pressure bonding rubber roll, and then cooled and solidified. . 9 A dry blended molding material containing an ethylene copolymer and an organic peroxide is extruded as a molten web from a T-die extruder at a temperature at which the organic peroxide does not substantially decompose, and an embossed pattern is formed. After passing between the engraved cooling roll and the pressure bonding rubber roll and press-bonding and once cooling and solidifying to form a single-sided embossed sheet, a release paper is placed on the non-embossed side of the single-sided embossed sheet, and the release paper and Embossing on both sides, characterized in that the surfaces of the web that are not in contact with each other are reheated to a temperature at which the organic peroxide does not substantially decompose, the release paper laminated web is passed between the roll and the pressure rubber roll, and is then cooled and solidified. A method for manufacturing a patterned filling adhesive sheet for solar cell modules.