JP2002160339A - Multi-layer laminated stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer laminated stretched film which reflects a light of arbitrary wavelength band selectively and widely. SOLUTION: A multi-layer laminated stretched film is composed of at least eleven layers. The layers are laminated in turn by two kinds of layers of which thicknesses are 0.05-0.3 μm. One kind of layer (layer A) is made of a polyethylene-2,6-naphthalate, and another kind of layer (layer B) is made of a thermoplastic resin of which refractive index is smaller than that of the polyethylene-2,6-naphthalate constituting the layer A. At least one of the layer A and the layer B is different in thickness each by each, and a value being divided a thickness of a most thick layer by that of a most thin layer is equal to or larger than 1.3. The layer A and the layer B are stretched in at least one direction as being laminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arbitrary wavelength band by alternately and regularly arranging layers having a low refractive index and layers having a high refractive index and controlling the ratio between the maximum value and the minimum value of the thickness of each layer. The present invention relates to a multilayer laminated stretched film that selectively reflects light.

[0002]

2. Description of the Related Art A multilayer laminated film is an optical interference film that selectively reflects or transmits light of a specific wavelength by structural light interference between layers having a low refractive index and a high refractive index alternately. Becomes Such a multilayer laminated film, if the wavelength of light selectively reflected or transmitted is in the visible light region, excellent design by structural coloring,
For example, it can be a film that looks iridescent. In addition, the design obtained here is based on the structural coloring of the multilayer laminated film and is not based on the dye, so there is no problem of fading. Further, since the multilayer laminated film has a high light reflectance without using metal, it can be used as a metallic glossy film or a reflection mirror. Furthermore, the multilayer laminated film can further control the refractive index in the plane direction between layers or within layers by stretching.
For example, if the refractive index in the plane direction in the layer has anisotropy,
It can also be a reflective polarizing plate.

[0003] As a multilayer laminated stretched film obtained by stretching such a multilayer laminate film, Japanese Patent Application Laid-Open No. 9-5068 is disclosed.
Japanese Patent Application Publication No. 37-37139 discloses a multilayered polymer film having a thickness of 0.5 μm in which a crystalline naphthalenedicarboxylic acid polyester and another selected polymer having a refractive index lower than at least one in-plane axis are alternately laminated. Less than,
A film in which the refractive index of at least one in-plane axis of the crystalline naphthalenedicarboxylic acid polyester layer is higher than that of an adjacent layer of the selected polymer is disclosed in JP-A-9-506988. A reflective polarizer using a multilayered polymer film is disclosed.

However, these multilayered polymer films can selectively reflect only an extremely narrow wavelength range due to the regularity of the optical thickness, and in order to widen the reflection wavelength range, It is necessary to use a polymer having a large difference in the refractive index or to extremely increase the number of layers.
Even for polymers with a large difference in refractive index, there is a limit to the refractive index of the polymer that can be laminated, and there is also a technical limit to increasing the number of layers, and at present it reflects such a wider wavelength band. There was no alternative but to take several measures such as stacking several laminated films.

The above two publications do not contain a lubricant in the surface layer in order to improve the optical transmittance, so that handling such as winding is difficult. Handling such as winding is not particularly problematic for a thick film, but when a thin film is formed, winding becomes extremely difficult and handling becomes substantially impossible.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a multilayer laminated stretched film that reflects light of an arbitrary wavelength band selectively and widely.

[0007]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a layer (A layer) made of a polymer having a high refractive index and a layer having a lower refractive index than the A layer. A layer (B layer) composed of a polymer and A layer and B layer
It has been found that the above problem can be solved by laminating at least 11 layers so that the layers are both end layers and controlling the ratio of the maximum and minimum thicknesses of the A layer and the B layer to complete the present invention. Reached.

Thus, according to the present invention, a thickness of 0.05
At least 11 layers of two layers each having a thickness of 0.3 μm are alternately laminated, one of which is a layer composed of polyethylene-2,6-naphthalate (layer A), and the other is a layer of polyethylene A of the layer A. A layer (B layer) made of a thermoplastic resin having a lower refractive index than 2,6-naphthalate,
At least one of the layers has a different thickness between the individual layers and the thickness of the thickest layer divided by the thickness of the thinnest layer is 1.3.
As described above, a multilayer laminated stretched film is provided, wherein the layer A and the layer B are stretched in at least one direction in a laminated state.

According to the present invention, as a preferred embodiment of the multilayer laminated stretched film, at least one of the A layer and the B layer has at least two layers whose distribution curves of the thickness of each layer can be clearly distinguished from each other. Multi-layer laminated stretched film having the above-mentioned thickness peak, or A layer or B layer
Also provided is a multilayer laminated stretched film in which at least one of the layers has the thickness of each layer continuously changing in the thickness direction.

Further, according to the present invention, as a preferred embodiment of the multilayer laminated stretched film, at least one of the layer A and the layer B contains inactive particles having an average particle size of 0.01 to 2 μm in a range of 0.001 to 0 μm. A multilayer laminated stretched film containing 0.5% by weight is provided, especially when the inert particles are silica, alumina, calcium carbonate, calcium phosphate, kaolin,
A multilayer laminated stretched film of at least one selected from the group consisting of talc, silicone, crosslinked polystyrene, and styrene-vinylbenzene copolymer; Also provided is a multi-layer stretched film that is active particles or a multi-layer stretched film having a relative standard deviation of the particle size of the inert particles of less than 0.3.

Further, according to the present invention, as a preferred embodiment of the multilayer laminated stretched film, the thermoplastic resin of the layer B is composed of polyethylene-2,6-naphthalate and polyethylene terephthalate in a weight ratio of 5:95 to 95: 5, a multilayer laminated stretched film which is a mixture of No. 5, a multilayer laminated stretched film which is a syndiotactic polystyrene, and a multilayer laminate stretched film which is a copolyethylene terephthalate having a melting point of 210 to 245 ° C. is also provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the multilayer laminated stretched film of the present invention, a layer made of a polymer having a high refractive index (A layer) and a layer made of a polymer having a lower refractive index than the A layer (B layer) are alternately formed. Are laminated. Hereinafter, the multilayer laminated stretched film of the present invention will be described.

The polyethylene-2,6-naphthalate constituting the layer A in the present invention is polyethylene-2,6-naphthalate.
Naphthalate homopolymers or copolymers in which at least 85 mol%, preferably 98 mol% or more of the total repeating units are occupied by ethylene-2,6-naphthalate. Particularly preferred are polyethylene-2,6-naphthalate homopolymers. The use of these polyethylene-2,6-naphthalates has the advantage that the layer A has a high refractive index by stretching.

As the copolymerization component constituting the copolymer, for example, terephthalic acid, isophthalic acid, 2,7-
Aromatic carboxylic acids other than 2,6-naphthalenedicarboxylic acid such as naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid And the like as an acid component, and aliphatic diols such as butanediol and hexanediol;
An alicyclic diol such as cyclohexanedimethanol is mentioned as the glycol component.

The layer B in the present invention needs to have a lower refractive index than the polyethylene-2,6-naphthalate constituting the layer A, and preferably has a refractive index of polyethylene-
It is a thermoplastic resin that is 0.005 or more lower than 2,6-naphthalate, more preferably 0.02 or more. As such a thermoplastic resin, the following three types (1) to (3) are preferably mentioned. (1) A mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate (2) Syndiotactic polystyrene (3) Copolyethylene terephthalate having a melting point of 210 ° C. to 245 ° C. Among them, the B layer is composed of polyethylene-2,6- It is preferable to use a mixture of naphthalate and polyethylene terephthalate or a mixture of syndiotactic polystyrene. Particularly, since the refractive index of the B layer can be easily changed,
The layer B is preferably composed of the above mixture.

The polymer constituting the layer B in the present invention is as follows: (1) a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate, (2) syndiotactic polystyrene or (3) a melting point of 210
The case of copolyethylene terephthalate at a temperature of from 245C to 245C will be described.

When the polymer constituting the layer B in the present invention is a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate, the mixing ratio of the two is 5:95 to 95: 5 by weight, especially 20: 80-
It is preferably in the range of 80:20. If the mixing ratio is such that the ratio of polyethylene terephthalate is less than 5% by weight or the ratio of polyethylene-2,6-naphthalate exceeds 95% by weight, the difference in the refractive index from the layer A tends to be insufficient. The ratio of polyethylene terephthalate is 9
If the content exceeds 5% by weight or the proportion of polyethylene-2,6-naphthalate is less than 5% by weight, the difference in melt viscosity from layer A becomes excessively large, and it becomes extremely difficult to maintain a multilayered state. .

Since the refractive index of the layer B can be adjusted by changing the mixing ratio of polyethylene terephthalate and polyethylene-2,6-naphthalate, it is necessary to prepare various polymers for adjusting the reflectance. There is no. In other words, there is an advantage that a multilayer laminated stretched film having various reflectances can be easily obtained only by adjusting the mixing ratio in the mixture. Further, when the polymer of the layer B is copolymerized, the polymer becomes low in crystallinity, so that a special extruder or a drier may be required when extruding the polymer in a molten state. However, according to the present invention, since the mixture is a mixture, the decrease in crystallinity is small, and there is an advantage that the above-described special equipment is not required.

The polyethylene terephthalate and polyethylene-2,6-naphthalate in the mixture constituting the layer B will be described in more detail. Polyethylene in the mixture
2,6-Naphthalate is a polyethylene-2,6-naphthalate homopolymer or a copolymer in which at least 80 mol%, preferably 90 mol% or more of all the repeating units are occupied by ethylene-2,6-naphthalate. . Of these, the above homopolymers are preferred. Examples of the copolymer component constituting the copolymer include, for example, other aromatic carboxylic acids such as terephthalic acid, isophthalic acid, and 2,7-naphthalenedicarboxylic acid; adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and the like. An aliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid; an acid component such as an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid; an aliphatic diol such as butanediol and hexanediol; and an alicyclic diol such as cyclohexanedimethanol. Can be.

The polyethylene terephthalate in the mixture is a polyethylene terephthalate homopolymer or a copolymer in which at least 80 mol%, preferably 90 mol% or more of all the repeating units are occupied by ethylene terephthalate. Of these, the above homopolymers are preferred. Examples of the copolymer component constituting the copolymer include other aromatic carboxylic acids such as isophthalic acid and 2,7-naphthalenedicarboxylic acid; and aliphatic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. Dicarboxylic acids; acid components such as alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, butanediol,
Glycol components such as aliphatic diols such as hexanediol; and alicyclic diols such as cyclohexanedimethanol can be mentioned. Among these copolymers, copolymers of isophthalic acid are preferred.

By the way, although the melting point of the mixture constituting the layer B is lower than the melting point of the original polymer, two peaks derived from each polymer are formed. Among the melting point peaks of the mixture constituting the layer B, the higher peak temperature is 220 ° C. to 265 ° C., and 240 to 26 ° C.
Those in the range of 0 ° C. are preferred. Further, the temperature difference between the melting point of the polymer forming the layer A and the higher melting point peak of the mixture forming the layer B is preferably at least 10 ° C and more preferably at least 20 ° C. When the difference in the melting points is at least 10 ° C., the difference in the orientation due to the heat treatment tends to increase,
Easy difference in refractive index.

The stretched film is preferably subjected to a heat treatment (thermal fixing treatment) for thermal stabilization. The polymer constituting the layer B is polyethylene-based.
When a mixture of 2,6-naphthalate and polyethylene terephthalate was used, the melting point (Tm
(TmA-60) ° C to (TmA
Preferably, the heat treatment is performed at a temperature in the range of -10) ° C.

Next, the case where the polymer constituting the layer B in the present invention is syndiotactic polystyrene will be described. Syndiotactic polystyrene is a syndiotactic structure, that is, a steric structure in which phenyl groups and substituted phenyl groups, which are side chains, are alternately located in opposite directions to the main chain formed from carbon-carbon bonds. And its tacticity is quantified by nuclear magnetic resonance with isotope carbon.
Tacticity measured by this method can be represented by the existence ratio of a plurality of continuous structural units, for example, dyad for two, triad for three, and pentad for five. As the syndiotactic polystyrene referred to in the invention, usually, a polystyrene having a syndiotacticity of 75% or more in racemic dyad, preferably 85% or more, or 30% or more in racemic pentad, preferably 50% or more,
Examples thereof include polyalkylstyrene, polyhalogenated styrene, polyalkoxystyrene, polyvinylbenzoic acid, hydrogenated polymers thereof, and copolymers thereof. Among these, preferred syndiotactic polystyrene has a melting point in the range of 220 to 270 ° C. More preferably, 240 to 270
It is in the range of ° C. Further, a copolymer can be used as syndiotactic polystyrene, and p-
Copolymers with methylstyrene are preferred. Here, the melting point of homosyndiotactic polystyrene is 270 ° C.
It is. To make the melting point of the copolymer fall within the above range, p
-The amount of copolymerization of methylstyrene may be adjusted. If the amount of p-methylstyrene is large, the melting point decreases and the crystallinity also decreases.
The copolymerization amount is preferably from 0 to 20 mol%. If the melting point is lower than 220 ° C., the crystallinity of syndiotactic polystyrene will be too low, making film formation difficult, and heat resistance (dimensional change when subjected to heat treatment) will be poor. In the B layer made of this syndiotactic polystyrene, as long as the optical properties are not deteriorated, there is no problem even if inert particles are added, but it is preferable that the inert particles are not substantially contained. . Atactic polystyrene and isotactic polystyrene are not preferred because they have low crystallinity and are difficult to form, and do not have a crystalline structure or have a loose structure, and thus have poor heat resistance.

Polyethylene-2,6-naphthalate is
The stretching increases the refractive index in the stretching direction. However, since syndiotactic polystyrene exhibits negative optical anisotropy, the refractive index in the stretching direction hardly increases, and the difference in refractive index between the two layers can be increased.

The difference in melting point between the layer composed of polyethylene-2,6-naphthalate (layer A) and the layer composed of syndiotactic polystyrene (layer B) is preferably within 30 ° C. If the difference is greater than 30 ° C., it is not preferable because, after melting and laminating, solidification is performed to form an unstretched sheet, delamination between layers occurs, and peeling occurs during subsequent stretching.

Incidentally, the stretched film is preferably subjected to a heat treatment (heat setting treatment) for thermal stabilization. When syndiotactic polystyrene is used as the polymer constituting the layer B, (TmA-60) ° C based on the melting point (TmA) of the polymer in the A layer.
The heat treatment is preferably performed at a temperature in the range of (TmA-10) ° C.

The case where the polymer constituting the layer B in the present invention is copolyethylene terephthalate having a melting point of 210 ° C. to 245 ° C. will be described. When the melting point of copolyethylene terephthalate is less than 210 ° C., the crystallinity of the polymer becomes too low, and it is difficult to form a film. Further, the heat resistance of the B layer is inferior, and it is likely to have a bad influence on the overall heat resistance. On the other hand, when the melting point of copolyethylene terephthalate exceeds 245 ° C., the crystallinity of the polymer increases, and the orientation crystallization at a relatively high stretching temperature proceeds with respect to the glass transition point (Tg) of the polymer. The film-forming property is deteriorated, and the adhesion to the layer A is apt to decrease.

The melting point and Tg of the copolyethylene terephthalate can be adjusted by selecting and adjusting the type and amount of the copolymer component. The copolymerization component may be a dicarboxylic acid component or a glycol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; adipic acid, azelaic acid Aliphatic dicarboxylic acids such as acetic acid, sebacic acid and decane dicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid; and the glycol component includes aliphatic diols such as butanediol hexane diol; An alicyclic diol such as methanol can be exemplified. In particular, it is preferable to use isophthalic acid as the copolymer acid component in order to achieve the present invention. These copolymer components can be used alone or in combination of two or more. The copolymerization amount of isophthalic acid is preferably 4
~ 18 mol%, more preferably 8 ~ 15 mol%.
It is preferable that the B layer be substantially free of inert particles, but there is no problem even if it is added as long as the optical characteristics are not deteriorated.

The intrinsic viscosity (orthochlorophenol, 35 ° C.) of the copolyethylene terephthalate is 0.45 to
0.8, more preferably 0.5 to 0.7.

In the present invention, the difference between the glass transition points (Tg) of the layer A and the layer B of the multilayer laminated stretched polyester film is preferably 40 ° C. or more. Within this range,
When the film is stretched at a temperature corresponding to the Tg of the layer A, the temperature becomes an excessive stretching temperature for the polymer of the layer B, and the orientation due to the stretching is suppressed, and almost becomes a flow (flow stretching). Therefore, the polymer of the layer A is oriented by stretching and the refractive index is increased, but the orientation of the polymer of the layer B is suppressed and the difference in the refractive index between the two is increased. If the Tg difference is less than 40 ° C., the difference between the Tg of the B-layer polymer and the stretching temperature adjusted to the polymer of the A-layer becomes small, and the refractive index difference between the A-layer and the B-layer after stretching tends to be insufficient.

Incidentally, the stretched film is preferably subjected to a heat treatment (thermal fixing treatment) for thermal stabilization, and the polymer constituting the layer B has a melting point of 210 ° C.
In the case where copolyethylene terephthalate at 〜245 ° C. is used, the melting point (TmA) of the polymer in the layer A is higher than the melting point of the polymer in the layer B −30 and lower than the melting point −30 of the polymer in the layer A. The heat treatment is preferably performed at a temperature.

In the present invention, at least one of the polymers constituting the layer A or the layer B has an average particle diameter of preferably 0.01 μm to improve the winding property of the film.
Inert particles in the range of 2 μm, more preferably 0.05-1 μm, most preferably 0.1-0.3 μm, preferably 0.001% to 0.5% by weight, more preferably 0.005% by weight. ０．２0.2% by weight. If the average particle size of the inert particles is less than 0.01 μm or the content is less than 0.001% by weight, the improvement in the winding property of the film tends to be insufficient, while the average particle size of the inert particles is 2 μm.
When the content exceeds 0.5% by weight or when the content exceeds 0.5% by weight, the deterioration of the optical properties due to the particles tends to be remarkable, and the light transmittance of the whole film may decrease. The light transmittance is preferably 70% or more, and if it is lower than this, the performance is insufficient for optical applications.

Examples of such inert particles include inorganic inert particles such as silica, alumina, calcium carbonate, calcium phosphate, kaolin, and talc; silicone;
Organic inert particles such as crosslinked polystyrene and styrene-divinylbenzene copolymer can be mentioned. The inert particles are spherical particles having a ratio of the major axis to the minor axis of 1.2 or less, and further 1.1 or less (hereinafter, may be referred to as true spherical particles). It is preferable in terms of balancing the optical characteristics. The inert particles preferably have a sharp particle size distribution, for example, those having a relative standard deviation of less than 0.3, more preferably less than 0.2. When particles having a large relative standard deviation are used, the frequency of coarse particles increases, which may cause optical defects. Here, the average particle diameter, particle diameter ratio, and relative standard deviation of the inert particles are as follows. First, a metal for imparting electrical conductivity is sputtered very thinly on the particle surface, and 10,000 to 30,000 times with an electron microscope. The major axis, the minor axis, and the area circle equivalent diameter are obtained from the enlarged image, and are then calculated by applying them to the following equation.

## EQU1 ## Average particle diameter = total area circle equivalent diameter of measurement particles / number of measurement particles Particle diameter ratio = average major diameter of particles / average minor diameter of particles The inert particles include titanium oxide and zinc sulfide. Particles that act as pigments or colored particles degrade optical characteristics, so it is preferable to avoid using them as far as possible. It is particularly preferable that the above-mentioned inert particles are contained in the layer A and that the layer B contains substantially no inert particles.

The lamination state of the layer A and the layer B in the present invention is as follows.
A layer and B layer are alternately 11 layers or more in total, preferably 31
It is a laminate of at least two layers. If the number of layers is less than 11 layers,
Selective reflection due to multiple interference is small, and a sufficient reflectance cannot be obtained. Note that the upper limit of the number of layers is preferably at most 301 layers from the viewpoint of productivity and the like.

In the multilayer laminated stretched polyester film of the present invention, when the layer B is in one of the both end layers, A
Since the glass transition point of the polymer forming the layer is usually higher than that of the polymer forming the layer B, it is possible to raise the stretching temperature necessary for stretching the layer A when heating with a roll or the like for stretching. In some cases, the temperature may not be increased in order to prevent the B layer on the surface from being melted at the time of heat setting, and problems such as insufficient thermal stability may occur. On the other hand, when the layer A is located at both ends, the thermally unstable layer B is located at the inner layer, so that it can be produced at a sufficient stretching temperature or heat setting temperature. The film is preferably one in which the layer A is located at both end layers. In addition, the both-end layers referred to in the present invention are outermost layers in a direction perpendicular to the plane direction of the multilayer laminated stretched film.

Further, the A layer and the B layer each have 1
The thickness of the layer is required to be 0.05 to 0.3 μm in order to reflect light selectively due to light interference between layers.

In the multilayer laminated stretched film of the present invention, the ratio obtained by dividing the maximum thickness of each layer by the minimum thickness in either the A layer or the B layer, preferably in both layers, is 1.3 or more. , Preferably 1.5 or more, more preferably 1.8 or more.
As a result, it is possible to perform selective reflection in a wide wavelength band that cannot be obtained with the conventional uniform thickness of each layer. In addition,
The upper limit of the ratio of the maximum thickness of each layer divided by the minimum thickness is preferably at most 3. If the ratio exceeds 3, the reflection wavelength band becomes too wide, and a sufficient reflectance cannot be obtained. Either the thickness of the layer A or the layer B is changed gradually and continuously, or in several steps so that at least two or more thickness peaks that can be clearly distinguished when a distribution curve of the thickness is viewed are developed. It is preferable to change the values in steps. Varying the thickness of the layer A or the layer B randomly tends to reduce the interference in each layer. It is particularly preferable that both the thicknesses of the layer A and the layer B are continuously changed along the thickness direction. The thickness peaks that can be clearly distinguished here are 0 to
When drawing a distribution curve obtained by dividing the thickness range of 1 μm by 100,
It means that there is a valley of less than half the frequency of both peaks between two thickness peaks.

In order to increase the range of the selective reflection wavelength, the reflective film of the present invention uses a plurality of multi-layer laminated stretched films having different selected wavelengths in combination. Different laminated films may be laminated at the time of film formation without interposition of an adhesive or the like, or after forming a plurality of multilayer laminated stretched films,
They may be laminated with an adhesive or the like. From the viewpoint of simplifying the process and preventing a decrease in the optical interference effect due to the presence of the adhesive or the like, it is preferable to laminate the laminated films having different selected wavelengths without forming an adhesive or the like at the time of film formation. In addition, as long as the object of the present invention can be achieved, a near-infrared absorbing agent that absorbs a specific wavelength region can be contained, or a transparent film containing a near-infrared absorbing agent can be laminated and used in combination. .

Incidentally, the reflective film of the present invention is stretched in at least one direction, preferably biaxially. The stretching temperature is preferably in the range from the glass transition point (Tg) of the resin of the layer A to Tg + 50 ° C. The stretching ratio is 2 to 10 times in the case of uniaxial stretching, and the stretching direction is
It may be vertical or horizontal. In the case of biaxial stretching, the area ratio is 5 to 25 times. As the stretching ratio increases, the variation in the plane direction of each of the A layer and the B layer becomes absolutely small due to the thinning by stretching, and the light interference of the multilayer laminated stretched film becomes uniform in the plane direction. preferable. As the stretching method, known stretching methods such as sequential biaxial stretching, simultaneous biaxial stretching, tubular stretching, and inflation stretching are possible, but preferably sequential biaxial stretching is advantageous in terms of productivity and quality. is there. Further, the stretched film is preferably stabilized by a heat treatment for thermal stabilization. The temperature of the heat treatment is preferably higher than (melting point of layer B−30) ° C. and lower than (melting point of layer A−30) ° C. However, when the temperature is too high, the melting of the layer B starts, so that the thickness unevenness is deteriorated and the continuous film forming property is deteriorated.

The multilayer laminated stretched film of the present invention comprises:
For example, polyethylene-2,6-containing inert particles
A polymer forming an A layer mainly composed of naphthalate;
Two layers are alternately laminated so that layer A is formed on both surfaces by a simultaneous multilayer extrusion method using a feed block, and the polymer forming the layer is developed on a die. At this time, the polymer laminated in the feed block maintains the laminated form, and by adjusting the thickness of each layer laminated in the feed block, the polymer is gradually or continuously along the thickness direction. A change in thickness can be imparted to layer A or layer B. The sheet extruded from the die is cooled and solidified by the casting drum, and becomes an unstretched film. The unstretched film is heated to a predetermined temperature, stretched in a vertical and / or horizontal direction, heat-treated at a predetermined temperature, and wound up.

The multilayer laminated stretched film of the present invention has another transparent resin film, an antireflection layer, a metal thin film, a hard coat layer, or another multilayer laminated stretched film having a different reflectance for the purpose of adjusting the thickness and improving the handleability. You may use it in the form of the laminated body laminated | stacked with the film. The other transparent resin films have low light loss due to light scattering and diffusion.
It is defined as a substance having a haze of 10% or less measured according to K-7105, and it is advantageous that the refractive index is large, and polyethylene terephthalate, polyethylene-2,
Suitable examples include polyesters such as 6-naphthalate, polycarbonate, triacetyl cellulose, polymethyl methacrylate, polystyrene, polyvinyl chloride and the like. The thickness of the transparent resin film is 25
It is preferably from 200 to 200 m, more preferably from 50 to 150 m. If the thickness of the transparent resin film is less than 25 μm, the strength is insufficient, and if it exceeds 200 μm, the rigidity of the film is increased and the secondary workability on the display surface of the video equipment is inferior. As a method of lamination, coextrusion at the time of extrusion, lamination with an adhesive, or the like is used. Lamination is performed on one side or both sides of the transparent resin film.

[0042]

Next, the present invention will be described with reference to examples. The physical properties in the examples were measured by the following methods.

(1) Melting point and glass transition point (Tg) of polyester 20 mg of polyester chips were sampled and
20 ° C./min. Using DSC (DSC2920) manufactured by Instruments Co., Ltd. The glass transition degree and the melting point are measured at a heating rate of.

(2) Thickness of Each Layer (Maximum Thickness and Minimum Thickness) A sample was cut into a triangle and fixed to an embedded capsule.
Embed in epoxy resin. Then, the embedded sample is cut into a thin section of 50 nm in thickness in a section parallel to the longitudinal direction by a microtome (ULTRACUT-S), and observed and photographed with a transmission electron microscope at an acceleration voltage of 100 kv and photographed. , The thickness of each layer was measured, and for the A layer and the B layer, the thickness of the thickest layer of each layer was defined as the maximum thickness, and the thickness of the thinnest layer was defined as the minimum thickness.

(3) Reflectance Using a spectrophotometer MPC-3100 manufactured by Shimadzu Corporation, the relative specular reflectance with respect to an aluminum-deposited mirror at each wavelength is measured in the wavelength range of 350 nm to 2100 nm. The largest one of the measured reflectances is defined as the maximum reflectance.

(4) Peak half-width wavelength The same measurement as the maximum reflectance is performed, and the values at the short wavelength side and the long wavelength side of the wavelength at which the half-width of the maximum reflectance are obtained are respectively set at the short wavelength side and the long wavelength side peak half. The value range wavelength was used.

(5) Total light transmittance Similar to the reflectance, the spectrophotometer MPC-310 manufactured by Shimadzu Corporation is used.
Using 0, the light transmittance at each wavelength is measured in the range of 350 nm to 2100 nm. Among them, the average light transmittance in the visible light portion (450 to 700 nm) is defined as the total light transmittance.

(6) Winding property When winding the formed film, it is ranked according to the following criteria. ◎: There is no problem in winding. 巻 き: Winding can be performed by reducing the speed or adjusting the conditions. △: Somehow, wrinkles, etc. occur, but the winding can be performed. X: Even if the conditions were adjusted, many bumps and wrinkles could not be wound.

[Example 1] Polyethylene-2,6 naphthalate (PEN) having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.62 and polyethylene terephthalate (PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.63 ) Was prepared. Then, spherical spherical silica particles (average particle diameter: 0.12 μm, ratio of major axis to minor axis;
02, an average particle size deviation: 0.1) by weight of 0.11 wt.
A mixture of N and PET at a weight ratio of 50:50 was prepared as a resin for the B layer. After drying the resin of the layer A at 160 ° C. for 3 hours and the mixed resin of the layer B at 160 ° C. for 3 hours, it is supplied to an extruder and melted, and the polymer of the layer A becomes 31 layers and the polymer of the layer B becomes 30 layers. After the branching, the slit width of each layer gradually increases, and a multilayer feed block device in which the A layer and the B layer are alternately laminated is led to a die while maintaining the laminated state, and casting is performed. Cast on a drum and gradually change the thickness of each layer.
A total of 61 laminated unstretched sheets in which layers and layers B were alternately laminated were prepared. At this time, the extrusion amount of the A layer and the B layer is 1:
It adjusted so that it might be set to 0.8, and laminated | stacked so that both end layers might be A layers. The laminated unstretched sheet was stretched 3.5 times in the longitudinal direction at a temperature of 150 ° C., further stretched 5.5 times in the transverse direction at a stretching temperature of 155 ° C., and heat-set at 230 ° C. for 3 seconds. . The production conditions are shown in Table 1, and the physical properties of the obtained multilayer laminated stretched film are shown in Table 2.

[Examples 2 to 8 and Comparative Examples 1 to 4] The same operation as in Example 1 was repeated, except that the manufacturing conditions were changed as shown in Table 1. Table 2 shows the obtained physical properties.

[0051]

[Table 1]

[0052]

[Table 2]

The inert particles shown in Table 1 are as follows. Inactive particles A: spherical silica particles (average particle size: 0.12
μm, ratio of major axis to minor axis; 1.02, average deviation of particle diameter;
0.1) Inactive particles B: massive calcium carbonate (average particle size: 0.0
1 μm, ratio of major axis to minor axis; 1.4, average deviation of particle diameter;
0.25) Inactive particles C: spherical silicone (average particle size: 0.15)
μm, ratio of major axis to minor axis; 1.1, average deviation of particle diameter;
30) The resin types of the layer B shown in Table 1 are as follows. Resin type H: 5 PENs and PETs containing no inert particles
Mixed at a weight ratio of 0:50 Resin type I: Syndiotactic polystyrene containing no inert particles Resin type J: PET obtained by copolymerizing 12 mol% isophthalic acid containing no inert particles Resin type K: Inactive particles In addition, the melting points shown in Table 2 indicate the higher temperature when there are two or more melting point peaks.

Consider Tables 1 and 2 below. The multilayer laminated stretched films of Examples 1 to 8 of the present invention can selectively reflect light over a wide wavelength band such as 200 nm or more by changing the thickness of each layer. By controlling the minimum ratio, it was possible to obtain a high reflectance in an arbitrary wavelength range.
On the other hand, Comparative Examples 1 to 4 did not have a reflection function over a wide wavelength band because the thickness of each layer was uniform. Also, as in the examples, by adding inert particles,
As the multilayer laminated stretched film of the present invention, a film excellent in winding property was obtained.

[0055]

According to the present invention, by changing the thickness of each layer of the multilayer laminated stretched film, light can be selectively reflected over a wide wavelength band, and the thickness of each layer and the minimum and maximum of the thickness can be obtained. By controlling the ratio, a multilayer laminated stretched film having high reflectance in an arbitrary wavelength range is provided. According to the present invention, it is possible to obtain a less expensive and higher performance film in applications having a wide reflection wavelength band such as a half mirror, a metallic glossy film, a heat ray reflective film or a deflection film.

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Claims (9)

[Claims] At least 11 layers of two types having a thickness of 0.05 to 0.3 μm are alternately laminated, and one of the layers is composed of polyethylene-2,6-naphthalate (A).
The other layer is a layer (B layer) made of a thermoplastic resin having a lower refractive index than polyethylene-2,6-naphthalate of the A layer, and at least one of the A layer and the B layer is an individual layer. The thickness of the thickest layer divided by the thickness of the thinnest layer is not less than 1.3, and the A layer and the B layer are stretched in at least one direction in a laminated state. A multilayer laminated stretched film characterized by the following. 2. The multilayer laminated stretched film according to claim 1, wherein at least one of the layer A and the layer B has at least two or more thickness peaks whose thickness distribution curves of individual layers can be clearly distinguished from each other. 3. The multilayer laminated stretched film according to claim 1, wherein at least one of the layer A and the layer B has a thickness of each layer continuously changing in a thickness direction. 4. At least one of the A layer and the B layer contains 0.001 to 2 μm of inert particles having an average particle size of 0.01 to 2 μm.
The multilayer laminated stretched film according to claim 1, which contains 0.5% by weight. 5. The inert particles are at least four members selected from the group consisting of silica, alumina, calcium carbonate, calcium phosphate, kaolin, talc, silicone, crosslinked polystyrene and styrene-vinylbenzene copolymer. 2. The multilayer laminated stretched film according to 1. 6. The multilayer laminated stretched film according to claim 4, wherein the inert particles are spherical inert particles having a ratio of the major axis to the minor axis of at most 1.2. 7. The thermoplastic resin of the layer B is polyethylene-
The multilayer laminated stretched film according to claim 1, which is a mixture of 2,6-naphthalate and polyethylene terephthalate in a weight ratio of 5:95 to 95: 5. 8. The multilayer laminated stretched film according to claim 1, wherein the thermoplastic resin of the layer B is syndiotactic polystyrene. 9. The thermoplastic resin of the layer B has a melting point of 210 to 2.
2. A copolyethylene terephthalate at 45 ° C.
The multilayer laminated stretched polyester film according to the above.