JP5608426B2 - Method for manufacturing anisotropic conductive film - Google Patents

Description

The present invention relates to a method for producing an anisotropic conductive film in which conductive particles are arranged in approximately one row, and in particular, a novel anisotropic conductive film that does not cause disorder in the arrangement of conductive particles during thermocompression bonding. film forming method for the production of.

  For example, as a technique for mounting an electronic component on a substrate, a flip chip mounting method in which the electronic component is mounted on the substrate in a so-called face-down state is widely performed. This flip-chip mounting method is a method in which electrodes called bumps are formed as terminal electrodes of an electronic component, and the bumps are disposed so as to face the electrode portions of the substrate, and are electrically connected together.

  In the flip-chip mounting method, electrical and mechanical connection using an anisotropic conductive film is attempted for the purpose of improving connection reliability. An anisotropic conductive film is obtained by dispersing conductive particles in an insulating resin that functions as an adhesive. By sandwiching an anisotropic conductive film between the bump and the electrode portion, and heating and pressurizing, the conductive particles are crushed and electrical connection is achieved. In the portion where there is no bump, the conductive particles are kept dispersed in the insulating resin, and are kept electrically insulated. For this reason, electrical continuity is achieved only at the portion where the bump is present.

  According to the flip chip mounting method using an anisotropic conductive film, it is possible to electrically connect a large number of electrodes in a lump as described above, and the electrodes are connected one by one as in wire bonding. It is not necessary to connect with bonding wires, and it is relatively easy to cope with the miniaturization of terminal electrodes and the narrow pitch associated with high-density mounting.

  The flip chip mounting method is also used for connection between substrates, and electrical connection using an anisotropic conductive film using the flip chip mounting method is, for example, between a glass substrate and a flexible printed wiring board (FPC). And connection between a glass epoxy wiring board (ordinary printed wiring board) and a flexible printed wiring board.

  Improvements have been made in anisotropic conductive films, for example, one in which conductive particles contained in an anisotropic conductive film are arranged in a single layer has been proposed (for example, Patent Documents 1 and 2). See).

  In Patent Document 1, a resin composition obtained by dispersing and mixing conductive particles in a binder resin is formed into a film shape, and then rolled to arrange the conductive particles in a single layer in the plane direction. A method for producing an anisotropically conductive resin film molded article that imparts conductivity only to a thin film is disclosed.

  Further, Patent Document 2 discloses that conductive particles ejected by one spraying unit and applied with an electrostatic potential by electrostatic potential applying unit and resin particles ejected by another spraying unit on the surface to be treated. It is disclosed that an anisotropic conductive film in which one layer of conductive particles is arranged in a resin film formed of resin particles is obtained by spraying simultaneously.

  In the anisotropic conductive film, a part of the conductive particles to be disposed between the opposing electrodes is excluded together with the binder agent by pressure bonding at the time of connection. Therefore, in an ordinary anisotropic conductive film, the conductive particles are included in an amount larger than the necessary amount in anticipation of the amount of conductive particles to be excluded. However, the conductive particles are expensive because they are required to have a uniform size and the like, and adding more conductive particles than the necessary amount causes an increase in manufacturing cost. In addition, the conductive particles may be aggregated.

  Therefore, as described in Patent Documents 1 and 2, it is considered that these problems can be solved if the conductive particles contained in the anisotropic conductive film are arranged in a single layer.

JP-A-3-108210 JP 2009-134914 A

  However, when the thickness of the anisotropic conductive film is reduced to the particle size level of the conductive particles by rolling as in the technique described in Patent Document 1, for example, the adhesive component (binder) is also a small amount. As a result, the connection strength may be insufficient, and a problem remains in connection reliability. In order to solve this problem, an anisotropic conductive film having a two-layer structure by providing a layer not containing conductive particles as an upper layer is also conceivable. However, if the two-layer structure is merely used, the arrangement of the conductive particles in the lower layer may be disturbed at the time of pressure bonding, which may reduce the trapping rate of the conductive particles between the electrodes, resulting in insufficient electrical conduction. is there.

  On the other hand, as in the technique described in Patent Document 2, in the method of spraying conductive particles and resin particles using a spraying means to shift the conductive particles to one layer arrangement, an anisotropic conductive film is produced. However, the problem remains in terms of productivity. Moreover, the problem of the disorder of the arrangement of the conductive particles at the time of pressure bonding cannot be solved.

The present invention has been proposed in view of such a conventional situation, and can be easily manufactured even when the conductive particles are arranged in a single layer, and the arrangement of the conductive particles is not disturbed during press bonding. It aims at providing the manufacturing method of an anisotropic conductive film.

Moreover, the manufacturing method of the anisotropic electrically conductive film of this invention has the process of forming the 2nd layer containing an adhesive component and electroconductive particle on a base film, and the thickness of the said 2nd layer is Rolling the second layer so as to be approximately equal to the particle size of the conductive particles, curing the adhesive component contained in the rolled second layer to be in a semi-cured state, A step of laminating a first layer containing an adhesive component and not containing conductive particles on the second layer in a semi-cured state .

  In the present invention, since the conductive particles are arranged in a single layer in the second layer constituting the anisotropic conductive film, the necessary amount of conductive particles can be suppressed. In addition, since the first layer is formed by lamination, adhesion strength is also ensured. Furthermore, in the second layer, the adhesive component is in a semi-cured state and the conductive particles are fixed to some extent, so that the arrangement of the conductive particles is not disturbed at the time of pressure bonding.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the anisotropic electrically conductive film which can obtain a reliable connection state and conduction | electrical_connection state, reducing manufacturing cost. In addition, according to the present invention, an anisotropic conductive film in which conductive particles are localized in a lower layer and arranged in a single layer can be easily manufactured using a general-purpose process. It is possible to provide a method.

It is a schematic sectional drawing which shows the structural example of the connection structure connected by the anisotropic conductive film to which this invention is applied. It is a schematic sectional drawing which shows an example of the anisotropic electrically conductive film to which this invention is applied. It is a figure for demonstrating an example of the manufacturing method of the anisotropic electrically conductive film to which this invention is applied.

  Hereinafter, an anisotropic conductive film to which the present invention is applied and an embodiment of a manufacturing method thereof (hereinafter referred to as “this embodiment”) will be described with reference to the drawings.

  For example, as shown in the schematic cross-sectional view of FIG. 1, the connection structure using the anisotropic conductive film has an anisotropy between a chip component 1 such as an IC chip and a substrate 3 such as a flexible wiring board and a liquid crystal panel. It is configured by being electrically and mechanically connected and fixed through the conductive film 5.

  Here, bumps (projection electrodes) 2 are formed as connection terminals on one surface of the chip component 1. An electrode 4 is formed on one surface of the substrate 3 at a position facing the bump 2. An anisotropic conductive film 5 is interposed between the surface of the chip component 1 where the bumps 2 are formed and the surface of the substrate 3 where the electrodes 4 are formed, so that the bumps 2 and the electrodes 4 face each other. In the portion, the conductive particles contained in the anisotropic conductive film 5 are crushed to achieve electrical conduction. At the same time, mechanical bonding between the chip component 1 and the substrate 3 is also achieved by the adhesive component constituting the anisotropic conductive film 5.

  The bumps 2 formed on the chip component 1 are formed of a conductive metal such as Au, Cu, or solder, for example, and the height thereof is, for example, about several μm to several tens of μm. The bump 2 can be formed by plating or the like. For example, only the surface of the bump 2 can be conductive metal plating such as gold plating.

  On the other hand, since the electrode 4 formed on the substrate 3 is formed at the component mounting position of the wiring formed according to a predetermined circuit, it is not covered with a solder resist or the like and is formed in an exposed state. ing. In addition, it is also possible to give gold plating etc. to the surface of the electrode 4, for example.

  In the connection structure shown in FIG. 1, while reducing the necessary amount of conductive particles contained in the anisotropic conductive film 5 used for connection, the conductive particles are arranged in a single layer, thereby improving conduction reliability. It is necessary to secure. Further, in the connection using the anisotropic conductive film 5, it is necessary to ensure sufficient adhesion.

  Therefore, in this embodiment, in the connection structure shown in FIG. 1, the anisotropic conductive film 5 used for the connection between the chip component 1 and the substrate 3 has a two-layer structure, and satisfies this requirement. The conductive film 5 is realized.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the anisotropic conductive film 5. The anisotropic conductive film 5 includes, for example, a first layer 51 connected to the bumps 2 of the chip component 1 and a second layer 52 connected to the electrodes 4 of the substrate 3.

  Here, the first layer 51 is a layer that contains an adhesive component 51A as a binder and does not contain conductive particles. On the other hand, the second layer 52 is a layer containing an adhesive component 52A as a binder and conductive particles 52B. The second layer 52 is rolled to a thickness approximately equal to the average particle diameter of the conductive particles by a rolling process described later. As a result, the second layer 52 has a shape in which the conductive particles 52B are arranged in one row, as shown in FIG.

  As the conductive particles 52B contained in the second layer 52, any conductive particles may be used as long as they are known conductive particles used in this type of general anisotropic conductive film. For example, various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, metal alloy particles, metal oxide, carbon, graphite, glass, ceramic, plastic, etc. The surface of the particles may be coated with a metal, or the surface of these particles may be further coated with an insulating thin film. When using a resin particle surface coated with metal, examples of the resin particles include epoxy resin, phenol resin, acrylic resin, acrylonitrile / styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, styrene resin, etc. Can be mentioned. The average particle diameter of the conductive particles 52B is arbitrary, but is usually about several μm (for example, about 1 μm to 4 μm).

  Next, as an adhesive component of the first layer 51 and the second layer 52, a thermosetting resin, an ultraviolet curable resin, or the like conventionally used for the anisotropic conductive film 5 can be used. However, the adhesive component 52A of the second layer 52 is preferably made of a thermosetting resin and an ultraviolet curable resin. By using the thermosetting resin and the ultraviolet curable resin in combination as the adhesive component 52A, only the ultraviolet curable resin is cured, so that the degree of curing of the second layer 52 can be easily adjusted and moderate. It can be in a semi-cured state. Further, in addition to at least one of a thermosetting resin and an ultraviolet curable resin, a phenoxy resin conventionally used for adjusting fluidity when using the anisotropic conductive film 5 and adhesive properties after curing. A thermoplastic resin such as rubber, a rubber polymer, or the like may be further added.

  The thermosetting resin is contained in order to obtain the mechanical bond strength of the connection structure using the anisotropic conductive film 5. As specific examples of the thermosetting resin, acrylate resins such as various epoxy resins, epoxy group-containing (meth) acrylates, and urethane-modified (meth) acrylates can be used. Here, examples of the epoxy resin include bisphenol A (BPA) type epoxy resin, bisphenol F (BPF) epoxy resin, and novolac type epoxy resin. Among these thermosetting resins, bisphenol A (BPA) type epoxy resins and bisphenol F (BPF) epoxy resins are suitable.

  In order to cure the thermosetting resin, it is necessary to add a curing agent. The curing agent may be selected according to the type of thermosetting resin to be used. For example, when the thermosetting resin is an epoxy resin, an imidazole-based latent curing agent or the like can be used. Product names NovaCure HX3741 (Asahi Kasei Co., Ltd.), product name Novacure HX3921HP (Asahi Kasei Co., Ltd.), product name Amicure PN-23 (Ajinomoto Co., Inc.), product name ACR Hardener H-3615 (ACR) For example).

  In addition, when the thermosetting resin is an acrylate resin, a peroxide curing agent can be used. Examples of the peroxide curing agent include diacyl peroxides, peroxydicarbonates, peroxyesters, peroxyketals, dialkyl peroxides, hydroperoxides, silyl peroxides, and the like. Can do. Since the second layer 52 is semi-cured when the anisotropic conductive film 5 is completed, the amount added is less than that of the first layer 51.

  The ultraviolet curable resin is used alone or together with the thermosetting resin as the adhesive component 52A of the second layer 52 in order to easily bring the second layer 52 of the anisotropic conductive film into an appropriate semi-cured state. Is. When the ultraviolet curable resin and the thermosetting resin are used in combination, since the first layer 51 is thermally mixed when the connection structure is manufactured, the mechanical strength of the entire connection structure can be further increased. Specific examples of the ultraviolet curable resin include methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, epoxy acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylol propane triacrylate, dimethylol tricyclodecane diacrylate, tetra Methylene glycol tetraacrylate, 2-hydroxy-1,3-diacryloxypropane, 2,2-bis [4- (acryloxymethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] Various acrylate resins such as propane, dicyclopentenyl acrylate, tricyclodecanyl acrylate, tris (acryloxyethyl) isocyanurate, and the aforementioned thermosetting Also available epoxy group-containing the resin (meth) acrylate, acrylate resins such as urethane-modified (meth) acrylate. Moreover, these may be used individually by 1 type and may use 2 or more types together. Further, methacrylate may be used instead of such acrylate.

  When an ultraviolet curable resin is used, it is necessary to add a photopolymerization initiator. Examples include benzoin ethers such as benzoin ethyl ether and isopropyl benzoin ether; benzyl ketals such as benzylhydroxycyclohexyl phenyl ketone; ketones such as benzophenone and acetophenone and derivatives thereof; thioxanthones; bisimidazoles and the like. These may be used alone or in combination of two or more. Moreover, you may add sensitizers, such as amines, a sulfur compound, a phosphorus compound, to these photoinitiators in arbitrary ratios as needed.

  Next, in the second layer 52 of the anisotropic conductive film 5, the adhesive component 52 </ b> A may contain the conductive particles 52 </ b> B to form a layer. It is necessary to devise such that arrangement disorder does not occur at the time of pressure bonding during lamination with the layer 51. Therefore, in the present embodiment, the adhesive component contained in the second layer 52 is preliminarily set in a semi-cured state and the conductive particles are fixed to prevent alignment disorder, and then the first layer 51 are stacked.

  For example, when the adhesive component contained in the second layer 52 is only an ultraviolet curable resin, a semi-cured state is obtained by controlling the ultraviolet irradiation amount. However, when an ultraviolet curable resin and a thermosetting resin are used in combination as an adhesive component contained in the second layer 52, only the ultraviolet curable resin is cured by ordinary ultraviolet irradiation, so that it is semi-cured. It becomes possible to be in a state.

  In any case, by making the adhesive component contained in the second layer 52 in a semi-cured state, the disorder of the arrangement of the conductive particles is suppressed, and it becomes possible to reliably avoid poor conduction and the like. In addition, since the adhesive component contained in the second layer 52 is in a semi-cured state, if it is finally cured in a subsequent press-bonding step, the function as an adhesive can be sufficiently exhibited.

  In the anisotropic conductive film 5 of the present embodiment, the first layer 51 is stacked on the second layer 52, but the adhesive component is in an uncured state in the first layer 51.

  Although the configuration of the anisotropic conductive film in the present embodiment has been described above, this anisotropic conductive film can be manufactured by the following manufacturing method, for example.

  When the above-described anisotropic conductive film 5 having a two-layer structure is produced, first, the second layer 52 is formed. For example, as shown in FIG. 3, the second layer 52 is formed by applying an anisotropic conductive material containing an adhesive component 52A and conductive particles 52B on a base film 11 such as a polyethylene terephthalate film. The coating layer 12 is formed.

  As described above, in the coating layer 12, the second layer is one in which conductive particles 52B are arranged in the adhesive component 52A. Even if an ordinary coater is used to form a thin film in which one layer of conductive particles is arranged, it is difficult to form a coating because the conductive particles aggregate in the gap. Therefore, an anisotropic conductive material composed of the conductive particles 52B and the adhesive component 52A is previously coated on the base film 11 so as to have a thickness of about 2 to 3 times the particle size of the conductive particles 52B.

  Next, the two base film 13 is laminated on the coating layer 12. Then, the laminated body in which the coating layer 12 is sandwiched between the base films 11 and 13 is rolled with a laminator roll 14. The rolling operation by the roller 14 results in a film in which the conductive particles 52B are arranged in a single layer.

  After the rolling operation, when the adhesive component 52A preliminarily blended in the coating layer 12 is subjected to a curing reaction, the first layer 51 and the second layer 52 are mixed together when the first layer 51 is laminated, The flow of the second layer 52 can be suppressed, and the disorder of the arrangement of the conductive particles 52B can be suppressed. The curing reaction is performed by irradiating with ultraviolet rays when the adhesive component 52A is made of only the ultraviolet curable resin and also when the adhesive component 52A is made of the ultraviolet curable resin and the thermosetting resin. However, this curing reaction is performed so that the adhesive component 52A is in a semi-cured state. For example, in the case where the adhesive component 52A is made of only an ultraviolet curable resin, it is only necessary to irradiate the ultraviolet ray in an amount of about half or less of the ultraviolet ray amount required for curing. When it is made of a curable resin, only the ultraviolet curable resin may be cured by irradiation with ultraviolet rays.

  If the adhesive component 52A of the coating layer 12 is completely cured at this stage, it is difficult to ensure the adhesiveness at the time of pressure bonding.

  Next, on the 2nd layer 52 manufactured by rolling operation, the 1st layer 51 which does not contain electroconductive particle but contains only adhesion component 51A is laminated. As a result, an anisotropic conductive film having a two-layer structure in which the layer (second layer 52) in which one conductive particle is arranged is the lowest layer is formed.

  In the produced anisotropic conductive film 5, the second layer 52 is in a semi-cured state, the fluidity is suppressed and the conductive particles 52B are fixed, so that the amount of the conductive particles 52B used is greatly increased. It is possible to achieve a sufficient conductive connection while reducing.

  As mentioned above, although this Embodiment was described, it cannot be overemphasized that this invention is not limited to the above-mentioned embodiment, A various change is possible in the range which does not deviate from the summary of this invention. For example, the anisotropic conductive film 5 has a two-layer structure in the above-described embodiment, but may have a three-layer structure or more. Also in this case, each layer may be laminated so that one conductive particle is arranged in the lowermost layer.

  Next, specific examples of the present invention will be described. The scope of the present invention is not limited to the following examples.

<Example 1>
(1) Formation of 2nd layer The material shown below was mix | blended by the compounding quantity (mass part) shown below, respectively, and the solution used for formation of the 2nd layer containing an adhesive component and electroconductive particle was adjusted.
Acrylate resin (bifunctional acrylic monomer, CN112C60, manufactured by Sartoma) 70 parts by mass Phenoxy resin (PKHH, manufactured by Union Carbide) 30 parts by mass photopolymerization initiator (Irgacure 369, manufactured by Ciba Specialty Chemicals) 1 part by mass thermosetting Initiator (organic peroxide, Perhexa 3M, manufactured by NOF Corporation) 4 parts by mass of conductive particles (4 μmφ, Bright GNR-EHLCD, manufactured by Nippon Chemical Industry Co., Ltd.) 15 parts by mass Toluene 100 parts by mass

  The resulting solution was formed on a polyester film (thickness 10 μm) peel-treated using a bar coater, and then the solvent, toluene, was evaporated in a drying furnace to form an anisotropic conductive film (coating layer) having a thickness of 12 μm. ) Was formed. Subsequently, another polyester film (thickness 10 μm) was laminated on the coating layer. Thereafter, a laminator roll in a commercially available laminator was passed through this laminate. As a result, a second layer having a thickness of 4 μm sandwiched between the polyester films was obtained.

Next, from one side of the polyester film, an ultraviolet ray irradiator (Curemax, manufactured by Omiya Kasei Co., Ltd.) is used to irradiate ultraviolet rays at a dose of 6 mW / cm ² for 1 minute to make the second layer semi-cured. It was.

(2) Formation of the first layer The materials shown below are blended in the following blending amounts (parts by mass), and the solution is used for forming the first layer containing only the adhesive component and no conductive particles. Adjusted.
Epoxy resin (EP828, manufactured by Yuka Shell Epoxy Co., Ltd.) 40 parts by mass Phenoxy resin (PKHH, manufactured by Union Carbide) 30 parts by mass Latent curing agent (HX3941, manufactured by Asahi Kasei Co., Ltd.) 30 parts by mass Toluene 100 parts by mass

  The prepared solution was applied to a peeled polyester film (thickness 10 μm) by a bar coater. Thereafter, toluene as a solvent was volatilized in a drying furnace to form a first layer having a thickness of 16 μm.

(3) Lamination of second layer and first layer The polyester film on one side of the second layer is peeled to expose the coating layer of the second layer, and the adhesive component of the first layer is exposed. The surface and the coating layer of the second layer were made to face each other, and the second layer was laminated on the first layer to produce a laminate. Next, the laminator roll in the above-mentioned commercially available laminator was passed through this laminate. Thereby, an anisotropic conductive film composed of a first layer (thickness 16 μm) and a second layer (thickness 4 μm) sandwiched between polyester films was obtained.

<Comparative example 1 (conventional anisotropic conductive film)>
The materials shown below were blended in the following blending amounts (parts by mass) to prepare a solution used for forming an anisotropic conductive film having a one-layer structure composed of an adhesive component and conductive particles.
Epoxy resin (EP828, manufactured by Yuka Shell Epoxy) 40 parts by mass Phenoxy resin (PKHH, manufactured by Union Carbide) 30 parts by mass Latent curing agent (HX3941, manufactured by Asahi Kasei) 30 parts by mass conductive particles (4 μmφ, Bright GNR) -EHLCD, manufactured by Nippon Chemical Industry Co., Ltd.) 10 parts by mass Toluene 100 parts by mass

  The prepared solution was applied to a peeled polyester film (thickness 10 μm) by a bar coater. Thereafter, toluene as a solvent was volatilized in a drying furnace to form an anisotropic conductive film having a thickness of 20 μm.

<Evaluation>
Using the anisotropic conductive films produced in Example 1 and Comparative Example 1, respectively, the following connection structure of an ITO glass substrate and an IC chip was produced.
-ITO glass substrate: an ITO (indium tin oxide) electrode formed on one side of a 0.7 mm thick glass substrate-IC chip: size 2 mm x 20 mm x 0.55 (thickness), bump area 2500 µm ² With bumps

  Specifically, the polyester film formed on the anisotropic conductive film produced in each of Example 1 and Comparative Example 1 is peeled off, the second layer is disposed on the ITO glass substrate side, and the first layer is IC. The IC chip and ITO glass are brought into contact with each other through the anisotropic conductive films prepared in Example 1 and Comparative Example 1 in a state of being arranged on the chip side, and thermocompression bonding is performed under conditions of 190 ° C., 60 MPa, and 10 seconds. A connection structure was obtained. Table 1 shows the results of the initial conduction resistance and the conduction resistance after the reliability test (temperature 85 ° C., humidity 85% and after 250 hours) in the obtained connection structure.

  Here, Example 1 containing 15 parts by mass of conductive particles in the second layer having a thickness of 4 μm (15 parts by mass of conductive particles / total 120 parts by mass × 100 = 12.5%) and thickness Between Comparative Example 1 containing 10 parts by mass of conductive particles in a 20 μm anisotropic conductive film (10 parts by mass of conductive particles / 110 parts by mass as a whole × 100 = 9.1%) When the total amount used is compared, 12.5 × 4: 9.1 × 20 = 50: 182.

  As described above, in the anisotropic conductive film of Example 1, the thickness of the second layer containing the conductive particles can be reduced. As a result, the total amount of the conductive particles used is 1 / of that of Comparative Example 1. Despite being 3 or less, the performance (resistance value) equivalent to the anisotropic conductive film of Comparative Example 1 (conventional anisotropic conductive film) was obtained as shown in [Table 1]. Thereby, it turns out that the arrangement | sequence of the electroconductive particle which the anisotropic electrically conductive film of Example 1 contains is not disordered.

DESCRIPTION OF SYMBOLS 1 Chip component, 2 Bump, 3 Substrate, 4 Electrode, 5 Anisotropic conductive film, 51 1st layer, 52 2nd layer, 11, 13 Base film, 12 Coating layer, 14 Laminating roll

Claims (2)

Forming a second layer containing an adhesive component and conductive particles on a base film;
Rolling the second layer such that the thickness of the second layer is approximately equal to the particle size of the conductive particles;
Curing the adhesive component contained in the rolled second layer to a semi-cured state;
And a step of laminating and forming a first layer containing an adhesive component and not containing conductive particles on the second layer in a semi-cured state. Method. The adhesive component contained in the second layer is a thermosetting resin and an ultraviolet curable resin, and only the ultraviolet curable resin is cured by ultraviolet irradiation in the curing step. A method for producing the anisotropic conductive film according to 1 .

Images