JP6910133B2 - Polyimide film laminate - Google Patents

Description

The present invention relates to a polyimide film laminate having both bending resistance and surface hardness.

In recent years, flexible displays have been developed that can bend the visible part of smartphones and televisions, and the glass that has been used conventionally cannot be used because it breaks when bent. Therefore, it is necessary to develop a polymer film that is transparent, scratch resistant, and does not break even when bent, and has high bending resistance.
For example, in Cited Document 1, the touch panel laminate is arranged on the visual side of the display device, and when arranged on the display device, the transparent protective substrate is located on the display device side, and the transparent protective substrate is described. A touch panel laminate, which is a barrier laminate having at least one organic layer and at least one inorganic layer, is described.

Polyimide resin is an insoluble and infusible super heat resistant resin, and has excellent properties such as heat oxidation resistance, heat resistance, radiation resistance, low temperature resistance, and chemical resistance, and is an insulating coating agent and insulating material. It is used in a wide range of fields including electronic materials such as films, semiconductors, and electrode protective films for TFT-LCDs, and has recently been used for display materials such as optical fibers and liquid crystal alignment films.

Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), which are generally used as transparent films, have crystallinity, and cracks occur in the bent portion when repeated bending is continued. On the other hand, amorphous polyimide has high bending resistance, and cracks do not occur even if repeated bending is continued.
However, the surface hardness of the polyimide film is low, and even if the hard coat treatment is applied, the surface hardness is lower than that when the PET or PEN is hard coated. Further, in order to improve the surface hardness of the polyimide film, the present inventors added an inorganic layer, but in that case, due to the difference in shrinkage rate (linear expansion rate), the film is peeled off or warped at the layer interface. There was a problem.
As described above, it has been difficult to achieve both bending resistance and surface hardness with the conventional film laminate.

International Publication No. 2015/045965

The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a polyimide film laminate having both excellent bending resistance and surface hardness and further suppressing warpage. There is.

｛一般式（１）中、Ａは２価の有機基、Ｂは４価の有機基であり、そしてｎは２以上、である。｝

［７］
［１］〜［６］のいずれかに記載のポリイミドフィルム積層体を用いた表示デバイス。
［８］
前記表示デバイスが、ポリイミドフィルム積層体を最表面部材として用いていることを特徴とする［７］に記載の表示デバイス。
［９］
前記表示デバイスが屈曲部位を有する、［７］又は［８］に記載の表示デバイス。
［１０］
前記表示デバイスが曲面を有する、［７］又は［８］に記載の表示デバイス。

As a result of diligent studies to achieve the above object, the present inventors have made the inorganic layer arranged on the polyimide film a sea-island structure (creating a part with and without an inorganic layer) on the inorganic layer. We have come up with the idea that the adhesion between each layer can be improved by providing a portion where the arranged hard coat layer and the polyimide film come into contact with each other, and have completed the present invention.
That is, the present invention is as follows.
[1]
The following requirements:
(A) A polyimide film laminate in which an inorganic layer made of silicon oxide (SiO) and a hard coat layer are arranged in this order on at least one surface of the polyimide film.
(B) When the laminated body is viewed in a plan view from the hard coat layer side, the following formula:
Defined by the surface coverage of the inorganic compound contained in the surface coverage × inorganic layer of the actual surface coverage = inorganic layer, the actual surface coverage is 10% to 90% der Rukoto of the inorganic layer,
(C) In the laminated body, there is at least one portion where the polyimide film and the hard coat layer are in contact with each other, and
(D) When the entire laminated body viewed from the hard coat layer side in a plan view is partitioned by a square having a side of 1 cm, 90 of all the partitions include a portion in which the polyimide film and the hard coat layer are in direct contact with each other. Being% or more,
Meet the,
A polyimide film laminate having a transmittance of 80% or more and an attenuation coefficient of 1.0 or less.
[ 2 ]
The polyimide film laminate according to [1 ], wherein the refractive index of each layer constituting the laminate at 632.8 nm is higher in the order of the polyimide film> the inorganic layer> the hard coat layer.
[ 3 ]
The polyimide film laminate according to [1] or [2] , wherein the inorganic layer has a sea-island structure on the polyimide film.
[ 4 ]
The polyimide film laminate according to [3 ], wherein the shape of the sea island portion of the sea island structure is a linear shape, a circular shape having a curved portion, a polygonal shape having a straight portion, or a random shape composed of a combination thereof.
[5]
A transparent film laminate in which an inorganic layer and a hard coat layer are arranged in this order on at least one surface of the polyimide film, the thickness of the inorganic layer is 10 nm or more, and the thickness of the transparent film. The polyimide film laminate according to any one of [1] to [4], which is characterized by satisfying that it is 1/1000 or less of the amount.
[6]
The polyimide film contains a polyimide represented by the following general formula (1), and as A in the general formula (1), at least a structure represented by the following general formula (A-1) and the following general formula (A-). The polyimide film according to any one of [1] to [5 ], which comprises the structure represented by 2) and at least includes the following general formula (B) as B in the general formula (1). Laminated body.

{In the general formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is 2 or more. }

[ 7 ]
A display device using the polyimide film laminate according to any one of [1] to [ 6].
[ 8 ]
The display device according to [7 ], wherein the display device uses a polyimide film laminate as the outermost surface member.
[ 9 ]
The display device according to [7 ] or [ 8 ], wherein the display device has a flexion site.
[ 10 ]
The display device according to [7 ] or [ 8 ], wherein the display device has a curved surface.

According to the present invention, the actual surface coverage of the inorganic layer is set to 10 to 90%, and the hard coat layer and the hard coat layer are provided at one or more locations in the laminate in which the polyimide film and the hard coat layer are in contact with each other. Provided is a polyimide film laminate that can enhance the adhesion between the layer, the hard coat layer and the polyimide film, improve the bending resistance, have a higher surface hardness than the hard coat layer, and have both the bending resistance and the surface hardness. can do.
Further, since the linear expansion coefficient of the polyimide film and the inorganic layer are significantly different, the laminated body warps when heat-treated, but the structure of the present invention hardly warps, which is very advantageous in a process involving a temperature change. Become.

It is sectional drawing which shows typically one structural example of the polyimide film laminated body of this invention. It is a figure which shows an example of the conventional inorganic layer pattern. It is a figure which shows an example of the conventional inorganic layer pattern. It is a figure which shows an example of the inorganic layer pattern of this embodiment. It is a figure which shows an example of the inorganic layer pattern of this embodiment. It is a figure which shows an example of the inorganic layer pattern of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a configuration example of the polyimide film laminate of the present invention.
The polyimide film laminate 1 of the present invention
The following requirements:
(A) A polyimide film laminate in which an inorganic layer 3 and a hard coat layer 4 are arranged in this order on at least one surface of the polyimide film 2.
(B) When the laminated body is viewed in a plan view from the hard coat layer 4 side, the following equation:
The actual surface coverage of the inorganic layer 3 is 10 to 90%, which is defined by the actual surface coverage = the surface occupancy of the inorganic layer × the surface coverage of the inorganic compound contained in the inorganic layer, and (C. ) In the laminated body, there is at least one portion 5 where the polyimide film 2 and the hard coat layer 4 are in contact with each other.
It is characterized by satisfying.

According to the present invention, the actual surface coverage of the inorganic layer 3 is set to 10 to 90%, and each layer is provided with one or more portions 5 where the polyimide film and the hard coat layer 4 are in contact with each other in the laminate. It is possible to provide a polyimide film laminate 1 which can enhance the adhesion of the film, improve the bending resistance, have a higher surface hardness due to the hard coat layer 4, and have both the bending resistance and the surface hardness.
Hereinafter, each requirement will be specifically described.

(A) The inorganic layer 3 and the hard coat layer 4 are arranged in this order on at least one surface of the polyimide film 2.
The polyimide film 2 is a film made of a polyimide resin. In general, a polyimide resin is obtained by solution-polymerizing an aromatic acid dianhydride and an aromatic diamine to produce a polyimide precursor, which is then ring-closed and dehydrated at a high temperature to be thermally imidized, or chemically imidized using a catalyst. Is manufactured. In particular, since the solvent-soluble polyimide resin does not undergo a dehydration reaction in the drying step during film molding, it is possible to obtain a film having less stress strain and excellent dimensional stability in the plane direction.

The polyimide resin can be obtained, for example, by condensation of an acid dianhydride and a diamine. Preferred acid dianhydrides include aromatic acid dianhydrides and alicyclic acid dianhydrides. Among them, from the viewpoint of the solvent solubility of the polyimide resin and the optical properties of the polyimide film, examples of the acid dianhydride include 4,4'-oxydiphthalic dianhydride and 4,4'-(hexafluoroisopropyridene) diphthalic acid. Dianhydride, 9,9-diphenylfluorenic dianhydride, hydroxypyromellitic dianhydride, bicyclo [2,2,2] octo-7-ene-2,3,5,6-tetracarboxylic dianhydride The substance, 1,3,3a,4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione is preferable.
Similarly, preferred diamines include aromatic diamines, alicyclic diamines, and aliphatic diamines. Among them, for example, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 2,2'-bis (trifluoromethyl) benzidine, α, α'-bis (4-aminophenyl) -1, 4-diisopropylbenzene, 4,4'-bis (4-aminophenoxybiphenyl), cyclohexyldiamine, 1,4-bis (aminomethyl) cyclohexane, and bis (aminomethyl) norbornan are preferred. These acid dianhydrides and diamines may be used alone or in combination of two or more.
Of these, a polyimide resin containing at least 4,4'-oxydiphthalic dianhydride as an acid dianhydride and produced from 3,3'-diaminodiphenyl sulfone and 4,4'-diaminodiphenyl sulfone as a diamine. be.

｛一般式（１）中、Ａは２価の有機基、Ｂは４価の有機基であり、そしてｎは２以上、である。｝

The polyimide film contains a polyimide represented by the following general formula (1), and as A in the general formula (1), at least a structure represented by the following general formula (A-1) and the following general formula (A-). It is preferable that the structure represented by 2) is included and at least the following general formula (B) is included as B in the general formula (1).
The polyimide in which the polyimide film is represented by the general formula (1) is a soluble polyimide, which has low stress strain and is preferable from the viewpoint of transparency.

{In the general formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is 2 or more. }

The thickness of the polyimide film 2 is not particularly limited, but is preferably, for example, 10 μm to 100 μm. As a result, a polyimide film having excellent film strength and bending resistance as well as optical characteristics as a transparent film can be obtained.

As described above, the polyimide film 2 is amorphous, has high bending resistance as compared with the crystalline PET film, and cracks do not occur even if repeated bending is continued. However, on the other hand, because it is soft, the surface is easily scratched.
Therefore, the surface hardness is increased by arranging the inorganic layer 3 and the hard coat layer 4 on the polyimide film 2. Since the hard coat layer 4 alone cannot sufficiently develop the surface hardness, sufficient surface hardness can be ensured by arranging the inorganic layer 3. Further, by arranging the inorganic layer 3, in addition to the optical characteristics as a transparent film, the elastic modulus and scratch resistance are improved, and the bending resistance is improved.

The inorganic layer 3 is made of an inorganic substance or an inorganic compound, and is preferably a metal or a metal compound. For example, the inorganic layer 3 contains at least one selected from the group consisting of aluminum, silicon, titanium, aluminum compounds, silicon compounds and titanium compounds. Specific examples of the aluminum compound include alumina, kaolin, and hydrated alumina. Examples of the silicon compound include silica, quartz, glass, mica, talc, clay, wollastonite, silicon nitride, silicon oxide, silicon carbide and the like. Examples of the titanium compound include potassium titanate and titanium oxide. Further, among such aluminum compounds, silicon compounds and titanium compounds, silicon compounds have higher reactivity with alkoxysilane contained in the hard coat layer and can impart a high degree of adhesion to the hard coat layer. Is preferable. Among them, silicon oxide (SiO) is particularly preferable from the viewpoint of optical characteristics. Further, the inorganic layer 3 may be a single layer or a plurality of laminated layers, or a plurality of inorganic substances may be mixed.

The method for forming the inorganic layer 3 is not particularly limited, and examples thereof include a sputtering method, a vacuum deposition method, a CVD method, and an ion plating method, but the sputtering method is preferable. The higher the formation temperature of the inorganic layer 3, the better the crystallinity of the inorganic layer. Therefore, by using the heat-resistant polyimide film 2, the formation temperature can be raised, which is advantageous.
In particular, since the linear expansion coefficient of the polyimide film 2 and the inorganic layer 3 are significantly different from each other, warpage occurs in the laminated body 1 when heat-treated, but the structure of the present invention hardly causes warpage, which is extremely different in a process involving temperature change. It becomes advantageous to.
The thickness of the inorganic layer 3 is not particularly limited, but for example, the thickness of the inorganic layer is 10 nm or more and 1/1000 or less of the thickness of the polyimide film. Is preferable. As a result, the warp of the polyimide laminate can be suppressed more reliably.
Further, specifically, it is preferably 10 nm to 50 nm. As a result, the elastic modulus and scratch resistance are improved while maintaining the optical characteristics of the transparent film, and the bending resistance is improved. At that time, even when polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polycarbonate, or the like is used as the transparent film instead of the polyimide film, the thickness of the inorganic layer is 10 nm or more and the transparent film. The same effect is obtained when the thickness is 1/1000 or less with respect to the thickness of. As the transparent film, an amorphous polyimide film is preferable from the viewpoint of high bending resistance.

The inorganic layer 3 preferably has a refractive index of 1.6 or less at 632.8 nm. By setting the refractive index of the inorganic layer 3 to 1.6 or less, light scattering can be suppressed, and in particular, the haze value can be reduced. As a result, the light transmittance is increased and the light resistance is also improved.

The material of the hard coat layer 4 is not particularly limited, but for example, an inorganic hard coat material, an organic resin hard coat material, an organic-inorganic hybrid hard coat material, and the like can be used. Examples of the inorganic hard coat material include polysiloxane, polysilazane, and the like. Examples of the organic resin-based hard coat material include melamine resin, urethane resin, epoxy resin, alkyd resin, acrylic resin, and methacrylic resin. Examples of the organic-inorganic hybrid hard coat material include inorganic particle-dispersed organic resin, organic polymer-dispersed silica, acrylic silicon, and the like. From the viewpoint of improving scratch resistance, for example, a self-healing material having a rotaxane skeleton is preferable. From the viewpoint of improving the surface hardness, for example, polyfunctional acrylic resins such as polyol acrylate, polyester acrylate, urethane acrylate, epoxy acrylate and phosphazene acrylate are preferable.
The method for forming the hard coat layer 4 is not particularly limited, and examples thereof include a coating method, a transfer method, a vacuum vapor deposition method, and a sputtering method.
The thickness of the hard coat layer 4 is not particularly limited, but is preferably 1 to 20 μm, more preferably 2 to 10 μm, and even more preferably 3 to 8 μm. If it is thicker than 20 μm, cracks may occur in the hard coat layer 4 due to the stress generated during curing, and if it is less than 1 μm, the desired surface hardness may not be exhibited.

(B) When the laminated body 1 is viewed in a plan view from the hard coat layer 4 side, the actual surface coverage of the inorganic layer 3 defined by the following formula is 10 to 90%.
Actual surface coverage = surface occupancy of the inorganic layer 3 × surface coverage of the inorganic compound contained in the inorganic layer 3 When the coverage is 90% or more, the adhesion between the hard coat layer 4 and the polyimide film 2 is improved. The laminated body 1 warps due to the difference in shrinkage ratio of each layer, which can be sufficiently secured. On the other hand, if the coverage is less than 10%, the effect of improving the surface hardness of the polyimide film laminate cannot be obtained. By setting the coverage to 10 to 90%, stress caused by the difference in shrinkage of each layer is relaxed, warping is suppressed, and sufficient strength is obtained. From the viewpoint of improving the surface hardness of the polyimide film laminate, the coverage is more preferably 30% to 90%.

In the above-mentioned Cited Document 1 (WO / 2015/045965), a touch panel laminate, which is a barrier laminate having at least one organic layer and at least one inorganic layer, is described. In this laminate, the inorganic layer serves as a gas barrier layer. There is no description that a mask was used when the inorganic layer was formed by CCP-CVD in the examples, and it does not function as a gas barrier layer unless the inorganic layer is formed on the entire surface of the substrate. In Document 1, it is presumed that the inorganic layer is formed on the substrate with a coverage of 100%, and is not included in the scope of the present invention.

It is preferable that the inorganic layer 3 is composed of an inorganic substance or an inorganic compound as described above, and substantially does not contain other components such as a dispersion medium, a binder, and a filler.
For example, Japanese Patent Application Laid-Open No. 2014-208469 describes a transparent conductive pattern-forming substrate in which a transparent resin layer is formed on the surface of the substrate and a transparent conductive pattern containing metal nanowires is formed on the transparent resin layer. .. The transparent conductive pattern is formed by applying a conductive ink containing metal nanowires and a dispersion medium onto a substrate.
However, there are very few substantial metal nanowire portions in the conductive pattern. For example, as shown in FIG. 2, the surface occupancy of the conductive pattern 11 (inorganic layer) on the substrate 10 is 50%, and the surface coverage of the metal nanowires 11a (inorganic substance) contained in the conductive pattern 11 is 10%. As a result, the actual surface coverage is 50% × 10% = 5%, and there is no effect of improving the surface hardness, which is the object of the present invention.

(C) In the laminated body 1, there is one or more portions 5 where the polyimide film 2 and the hard coat layer 4 are in contact with each other.
When the hard coat layer 4 is formed on the portion of the polyimide film 2 where the inorganic layer 3 is not formed and is exposed from the inorganic layer 3, the polyimide film 2 and the hard coat layer 4 come into contact with each other. It becomes part 5.
When viewed in a plan view, the adhesion between the polyimide film 2 and the hard coat layer 4 is enhanced by having one or more portions 5 where the polyimide film 2 and the hard coat layer 4 are in contact with each other, and the difference in shrinkage ratio between the layers is increased. The resulting stress can be relieved. As a result, it is possible to suppress a decrease in bending resistance and warpage of the film laminate 1.

However, in order to obtain the effect of the present invention, the said portion 5 must be small to some extent and provided in a plurality of dispersed portions in the plane.
For example, as shown in FIG. 3, an inorganic layer 12 is formed on the entire inner surface of the substrate 10 leaving the outer peripheral portion of the substrate 10 (not shown, but a hard coat layer is formed on the substrate and the inorganic layer). In such a structure, "(B) the actual surface coverage of the inorganic layer is 10 to 90%, and (C) there is one or more sites 5 where the polyimide film and the hard coat layer are in contact with each other. Although it is a "existing" structure, such a structure is not assumed in the present invention.

That is, in the polyimide film laminate 1 of the present invention, the polyimide film 2 and the hard coat layer 4 are directly connected to each other when the entire laminate viewed in plan from the (D) hard coat layer 4 side is divided into squares having a side of 1 cm. The section including the contacting portion 5 accounts for 90% or more of the total section.
In the case shown in FIG. 3, for example, in the portion enclosed by the frame _{A 6,} part 5 has more than one location _{(A 1 ~A 5, A 10} , A 11, A 15, A 16, A 20, A 21 ~ A ₂₅ is the same). On the other hand, for example, in a portion surrounded by a frame A _7, the inorganic layer 12 between the polyimide film 2 and the hard coat layer 4 are entirely covered, the portion 5 and the polyimide film 2 and the hard coat layer 4 is in direct contact Not included (same for A ₈ , A ₉ , A _{12 to} A ₁₄ , and A _{17 to} A ₁₉ ). The ratio of the compartments including the portion 5 in FIG. 3 is 64% because the number of compartments including the portion 5 is 16 per the total number of compartments 25.
Even when the actual surface coverage of the inorganic layer 12 is as high as 70% or more, the portion 5 in contact between the polyimide film 2 and the hard coat layer 4 has a relatively small size of ^{, for example, less than 1 cm 2.} By being dispersed throughout the in-plane targetly or randomly, the adhesion between the polyimide film 2 and the hard coat layer 4 is enhanced over the entire surface of the laminated body while maintaining a high actual surface coverage, and also. The stress caused by the difference in shrinkage of each layer can be relaxed. As a result, the polyimide film laminate 1 has sufficient bending resistance and sufficient strength, particularly high surface hardness due to the hard coat layer 4, and warpage is further suppressed.

Specifically, it is preferable that the inorganic layer 3 has a sea-island structure on the polyimide film. By forming the inorganic layer 3 into a sea-island structure, a plurality of portions 5 in which the polyimide film 2 and the hard coat layer 4 are in contact with each other can be provided in a small size to some extent and dispersed in the plane.
The shape of the sea island of the sea island structure is not particularly limited, but for example, a linear shape (see FIG. 4), a curved circular shape (see FIGS. 5A and 5B), and a polygon having a straight line portion. A random shape consisting of a shape (see FIG. 6) or a combination thereof can be mentioned.
The island portion of the sea-island structure may be an inorganic layer or a polyimide film surface.

Such a polyimide film laminate 1 preferably has a transmittance of 80% or more and an attenuation coefficient (optical absorption coefficient) of 1.0 or less.
The transmittance is the ratio of light incident on the film transmitted through the film, and the light here is visible light having a thickness of 300 nm to 800 nm.
When the transmittance is 80% or more, the transparency is good, and when the attenuation coefficient is 1.0 or less, the yellowness is low and the clarity is excellent. For example, when used as the outermost layer of a display device. , Does not interfere with visibility.

It is preferable that the refractive index of each layer constituting the polyimide film laminate 1 is higher in the order of polyimide film 2> inorganic layer 3> hard coat layer 4.
When the polyimide film laminate 1 of the present embodiment is used as, for example, the outermost layer of a display device, the polyimide film 2 is attached as the inside (device side) and the hard coat layer 4 is attached as the outside (user side). In this case, by setting the refractive index of each layer as described above, reflection can be suppressed and the light transmittance can be increased.

In the polyimide film laminate of the present invention as described above, the actual surface coverage of the inorganic layer is 10 to 90%, more preferably 30 to 90%, and the polyimide film and the hard coat layer are contained in the laminate. Since there is one or more parts in contact with the hard coat layer, the adhesion between the hard coat layer and the inorganic layer, and the hard coat layer and the polyimide film is improved, the bending resistance is improved, and the hard coat layer has a higher surface hardness. However, both bending resistance and surface hardness are achieved.
In the above description, the case where the inorganic layer and the hard coat layer are laminated and formed on only one surface of the polyimide film has been described as an example, but the present invention is not limited to this, and both sides of the polyimide film are not limited to this. An inorganic layer and a hard coat layer may be laminated and formed on each of the two.

Further, one layer or two or more layers made of any resin or inorganic compound may be laminated on the polyimide film laminate of the present embodiment as the outermost layer. Such an outermost layer can have a role of a protective film, an antireflection film, a filter, or the like, or a function of adjusting the viewing angle of the display, preventing fogging, and the like.

Since the polyimide film laminate 1 of the present embodiment as described above has a high surface hardness, it is preferably used as the outermost surface member of the display device.
The specification described in Patent No. 4757709 states that the polymer substrate for resin glass and at least one fine particle selected from the group consisting of aluminum, silicon, titanium, aluminum compound, silicon compound and titanium compound on the polymer substrate for resin glass. A resin glass laminate having an inorganic layer to which the compound is adhered and an alkoxysilane-containing hard coat layer laminated on a polymer substrate for resin glass via the inorganic layer is described. However, this laminate is intended to be used for automobile glass, and is not intended to be used for display devices like the polyimide film laminate of the present invention.

[Display device]
The display device according to the present embodiment is not particularly limited as long as it is a display device including the above-mentioned polyimide film laminate 1. The display device is, for example, a television, a notebook, or the like, which includes a display unit such as a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), an electroluminescence display (EL), an organic EL display, or a laser display. It is used in a large number of electronic devices such as personal computers, computer monitors, mobile phone displays, PDA, smartphones, consoles, digital signage, etc., but is not limited to this. These display devices may have a touch panel function.

The polyimide film laminate 1 of the present embodiment has excellent bending resistance, and is particularly suitable when applied to a display device having a curved surface or a bent portion.
In particular, in an organic EL display, a curved display or a flexible display can be manufactured by using a flexible plastic or the like as the substrate.
Examples of the display device having a curved surface include a curved surface display. In this case, the bending direction of the curved surface of the device is not particularly limited, and the laminated film may be bent so as to be convex, may be a convex curved surface, or may be bent so that the laminated film is concave. It may be a concave curved surface.
Further, as a display device having a bent portion, a flexible display can be mentioned. Examples include foldable smartphones and flexible organic EL displays. In this case, the bending direction of the device is not particularly limited, and the laminated film may be bent so as to be convex, may be bent outward, or may be bent so that the laminated film is concave, or may be bent inward. There may be.

[Organic EL display]
In the organic EL display, a light emitting element is configured for each pixel. The light emitting element is composed of, for example, a negative electrode such as metal / electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer / positive electrode such as ITO, and a glass substrate or a transparent optical film. ..
The sandwich structure as described above is called a heterostructure, and an efficient reaction can be caused by confining electrons and holes in separate layers. Organic substances such as diamines, anthracenes, and metal complexes are used as materials for each layer.
The thickness of each layer between the electrodes is several nm to several hundred nm, and generally, the total thickness is 1 μm or less. A flexible display can also be manufactured by using a flexible plastic or the like for the substrate.
Organic EL displays are roughly classified into active matrix type (AM-OLED, Amored) and passive matrix type (PM-OLED) according to the drive method. There are three colorization methods: three-color method, color conversion method, and color filter method. Classified as a species. The polyimide film laminate 1 of the present embodiment can be used as the outermost surface member when incorporated into an organic EL display.

[Touch panel]
The polyimide film laminate 1 of the present embodiment can also be incorporated into a touch panel. A touch panel is an electronic component that combines a display device such as an LCD or an organic EL display with a position input device such as a touch pad, and is an input device that operates a device by pressing a display on the screen.
The polyimide film laminate 1 of the present embodiment incorporated in the touch panel is a financial institution ATM such as a bank, a vending machine, a mobile phone, a personal digital assistant (PDA), a digital audio player, a portable game machine, a copier, a fax, a car navigation system. , Smartphones, etc., can be incorporated and used in digital information devices. The polyimide film laminate 1 of the present embodiment can be used as the outermost layer when incorporated into a touch panel.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

Hereinafter, Examples, Reference Examples, and Comparative Examples performed for confirming the effects of the present invention will be described.
(Polyimide film production)
(Production Example 1)
8.6 g of 4,4'-diaminodiphenyl sulfone (hereinafter, also referred to as 4,4'-DDS) while introducing nitrogen gas into a 500 mL separable flask with a stirring rod equipped with a Dean-Stark tube and a reflux tube at the top. (34.7 mmol), 8.6 g (34.7 mmol) of 3,3'-diaminodiphenyl sulfone (hereinafter, also referred to as 3,3'-DDS), and 50.0 g of γ-butyrolactone (hereinafter, also referred to as GBL) are added. rice field. Subsequently, 21.7 g (70.0 mmol) of 4,4'-oxydiphthalic dianhydride (hereinafter, also referred to as ODPA), 22.3 g of GBL, and 26.0 g of toluene were added at room temperature, and then the temperature was raised to 160 ° C. Then, the mixture was heated under reflux at 160 ° C. for 1 hour to imidize. After the imidization was completed, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature to obtain a polyimide GBL solution (hereinafter, also referred to as polyimide varnish).
The obtained polyimide varnish is coated on a PET film (Cosmo Shine 100A4100, manufactured by Toyo Boseki) of a support with a coating thickness of 20 μm, and the temperature is 50 ° C. for 10 minutes and 100 ° C. for 10 minutes. After drying, the resin composition layer was peeled off from the PET film of the support and dried at 270 ° C. for 30 minutes in an air atmosphere to obtain a polyimide film (hereinafter, also referred to as PI-A).

(Production Example 2)
21.7 g (70.0 mmol) of 4'4-oxydiphthalic acid dianhydride (ODPA) of Preparation Example 1 was added to 4,4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (hereinafter, also referred to as 6FDA) 31. Polyimide was added to 1 g (70.0 mmol) in the same manner except that GBL was changed to N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP) and the drying condition of the polyimide film was changed from an air atmosphere to a nitrogen atmosphere. A film (hereinafter, also referred to as PI-B) was obtained.

(Production Example 3)
To a 500 mL separable flask, 50.0 g of GBL was added to 17.2 g (69.3 mmol) of 4,4'-DDS while introducing nitrogen gas. Subsequently, 21.7 g (70.0 mmol) of 4,4'-oxydiphthalic acid dianhydride (ODPA) and 22.3 g of GBL were added at room temperature, the temperature was raised to an internal temperature of 50 ° C., and the reaction was carried out at 50 ° C. for 12 hours. , The oil bath was removed and the temperature was returned to room temperature to obtain a polyamic acid GBL solution (hereinafter, also referred to as polyamic acid varnish).
The obtained polyamic acid varnish was coated on a PET film (Cosmo Shine 100A4100, manufactured by Toyobo Co., Ltd.) of a support with a coating thickness of a polyimide film having a thickness of 20 μm, and applied at 50 ° C. for 10 minutes and at 100 ° C. for 10 minutes. After the minute drying, the resin composition layer was peeled off from the PET film of the support and dried at 270 ° C. for 30 minutes in an air atmosphere to obtain a polyimide film (hereinafter, also referred to as PI-C).

(Production Example 4)
21.7 g (70.0 mmol) of 4'4-oxydiphthalic acid dianhydride (ODPA) of Preparation Example 3 and 31.1 g (70) of 4,4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA). In the same way as for the polyimide film (0.0 mmol), GBL was changed to N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP), and the drying condition of the polyimide film was changed from an air atmosphere to a nitrogen atmosphere. Hereinafter, it is also referred to as PI-D).

(Production Example 5)
4.4'-DDS 8.60 g (34.7 mmol) and 3,3'-DDS 8.60 g (34.7 mmol) of Production Example 1 are also referred to as 2,2'-bis (trifluoromethyl) benzidine (hereinafter, also referred to as TFMB). A polyimide film (hereinafter, also referred to as PI-E) was obtained in the same manner except that the amount was changed to 22.2 g (69.3 mmol).

(Production Example 6)
21.7 g (70.0 mmol) of 4,4′-oxydiphthalic acid dianhydride (ODPA) of Preparation Example 5 and 31.1 g (6FDA) of 4,4′- (hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA). 70.0 mmol), GBL to N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP), and the drying condition of the polyimide film was changed from an air atmosphere to a nitrogen atmosphere, but the polyimide film was formed in the same manner. (Hereinafter, also referred to as PI-F) was obtained.

(Examples, reference examples and comparative examples)
Using the polyimide films PI-A to PI-F produced as described above, a polyimide film laminate was produced with the configurations shown in Table 1.

(Preparation of inorganic layer)
The produced polyimide film was cut into a size of 100 mm × 100 mm, and the silicon oxide layer was sputtered using a mask so that the island portion of the sea-island structure had a square shape to prepare an inorganic layer-deposited film. Table 1 shows the thickness and coverage of the inorganic layer.

(Preparation of hard coat layer)
Hard coating agent A (Riodurus 2514, manufactured by Toyo Ink Co., Ltd.) is applied onto the obtained inorganic layer-deposited film with a bar coater under the condition that the film thickness after curing is 5 μm or 10 μm, and dried at 80 ° C. for 10 minutes under air. Then, using HC-98 (high pressure mercury lamp: HL400DL-1) manufactured by Sen Engineering Co., Ltd., UV irradiation was performed under the condition that the integrated i-line (365 nm) light amount was 1600 mJ to obtain a polyimide film laminate. The thickness of the hard coat layer is as shown in Table 1.

The obtained polyimide film laminates of Examples, Reference Examples and Comparative Examples were tested by the methods shown below, and the pencil hardness, warpage and bending resistance of the film were evaluated. The results are shown in Table 2.

(Measurement of pencil hardness)
Using an automatic pencil scratch tester (manufactured by Imoto Seisakusho Co., Ltd.) by the method of JIS K-5600-5-4, reciprocate 5 times with a load of 750 g, and reciprocate 5 times 3 times or more. Was the pencil hardness.

(Measurement of film warpage)
A piece of film having a width of 15 mm and a length of 100 mm is cut from an arbitrary place of a film having a size of 100 mm × 100 mm or more, and the static electricity is −0.01 V or less in an environment of a temperature of 23 ° C ± 1 ° C and a humidity of 50% ± 5%. The film was allowed to stand on the static eliminator mat kept in place for one day. After standing, the height at which the end of the film piece floated from the static elimination mat was measured. Those having a floating height of 1 mm or less were evaluated as ⊚, those having a floating height of 1 mm or more to 5 mm were evaluated as 0, and those having a floating height of 5 mm or more were evaluated as x.

(Bending resistance evaluation method)
Using a MIT type repetitive bending tester (MIT-DA, manufactured by Toyo Seiki Seisakusho Co., Ltd.), a test piece with a width of 15 mm and a length of 100 mm is loaded with 250 g, and has a bending radius of R2 mm, a bending angle of 135 °, and a speed. Repeated bending tests were performed 10,000 times and 30,000 times under the condition of 90 times / minute. After the test, the sample was removed from the device, and those that were not visually scratched were marked with 〇, and those with scratches and white turbidity were marked with x.

As is clear from Table 2, the polyimide film laminate of the example has both excellent bending resistance and surface hardness as compared with the polyimide film laminate of the comparative example, and warpage is also suppressed. Understand.
As is clear from Table 2, the polyimide film laminate of the reference example has both excellent bending resistance and surface hardness as compared with the polyimide film laminate of the comparative example, and warpage is also suppressed. Understand.

By using the polyimide film laminate according to the present invention, both bending resistance and surface hardness can be achieved and warpage can be suppressed, so that it can be widely used as the outermost surface member of a display device.

1: Polyimide film laminate 2: Polyimide film 3: Inorganic layer 4: Hard coat layer 5: Site

Claims (10)

The following requirements:
(A) A polyimide film laminate in which an inorganic layer made of silicon oxide (SiO) and a hard coat layer are arranged in this order on at least one surface of the polyimide film.
(B) When the laminated body is viewed in a plan view from the hard coat layer side, the following formula:
Defined by the surface coverage of the inorganic compound contained in the surface coverage × inorganic layer of the actual surface coverage = inorganic layer, the actual surface coverage is 10% to 90% der Rukoto of the inorganic layer,
(C) In the laminated body, there is at least one portion where the polyimide film and the hard coat layer are in contact with each other, and
(D) When the entire laminated body viewed from the hard coat layer side in a plan view is partitioned by a square having a side of 1 cm, 90 of all the partitions include a portion in which the polyimide film and the hard coat layer are in direct contact with each other. Being% or more,
Meet the,
A polyimide film laminate having a transmittance of 80% or more and an attenuation coefficient of 1.0 or less. The refractive index at 632.8nm of each layer constituting the laminate is higher in the order of the polyimide film> The inorganic layer> the hard coat layer, a polyimide film laminate of claim 1. The polyimide film laminate according to claim 1 or 2 , wherein the inorganic layer has a sea-island structure on the polyimide film. The polyimide film laminate according to claim 3 , wherein the shape of the sea island portion of the sea island structure is a linear shape, a circular shape having a curved portion, a polygonal shape having a straight portion, or a random shape composed of a combination thereof. A transparent film laminate in which an inorganic layer and a hard coat layer are arranged in this order on at least one surface of the polyimide film, the thickness of the inorganic layer is 10 nm or more, and the thickness of the transparent film. The polyimide film laminate according to any one of claims 1 to 4, wherein the polyimide film laminate is 1/1000 or less of the amount. The polyimide film contains a polyimide represented by the following general formula (1), and as A in the general formula (1), at least a structure represented by the following general formula (A-1) and the following general formula (A-). The polyimide film according to any one of claims 1 to 5, which comprises the structure represented by 2) and at least includes the following general formula (B) as B in the general formula (1). Laminated body.

{In the general formula (1), A is a divalent organic group, B is a tetravalent organic group, and n is 2 or more. }

A display device using the polyimide film laminate according to any one of claims 1 to 6. The display device according to claim 7 , wherein the display device uses a polyimide film laminate as the outermost surface member. The display device according to claim 7 or 8 , wherein the display device has a bending portion. The display device according to claim 7 or 8 , wherein the display device has a curved surface.

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