JP2023121739A - Multilayer laminate film - Google Patents

Abstract

To provide a multilayer laminate film that is not hazy, and achieves both high visibility of scenes and a display property of projection information from an oblique direction.SOLUTION: A multilayer laminate film has a plurality of different thermoplastic resin layers alternatively laminated more than 51 layers. When a temperature (T, °C) at which an absolute value of an amount of absorbed heat in a differential scanning calorimeter is maximum is set to be Tm, and a temperature (T, °C) calculated by a method described below is set to be T*, the multilayer laminate film satisfies Tm-T*>27. In a measurement method of T*: (1) when a minimum value of A(T) in 150<T<Tm out of a graph of a temperature differential curve A(T)=dDSC/dT(mW/°C) of a DSC1 st curve measured with 1°C intervals is set to be Amin, and T at this time is set to be Tmin, T that is an intersection of a curve A(T) and a linear line A(T)=0.2Amin in a range of T<Tmin is acquired; and (2) as to each T satisfying (1), a minimum T out of T always satisfying A(T)<0.2Amin in a range of T to T+5°C is T*.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a multilayer laminated film, an image display member, an image display device, and a head-up display that can be suitably used for image display members.

A head-up display (HUD, Head Up Display) system is a display system that displays information in the field of view of a passenger of transportation equipment such as a vehicle. It improves driving safety and comfort by displaying building information. As for the mechanism, the simplest method is to project an image from an image projector obliquely onto the projection part of the windshield of the transportation equipment, reflect the image, and bring the reflected image into the field of view of the passenger.

In such a display device, from the viewpoint of visibility of projection information and external information, for example, a HUD using a film having a polarization reflection characteristic that reflects only polarized light emitted from a liquid crystal projector has been disclosed (Patent Reference 1). However, since the light from the outside such as scenery is often unpolarized, there is a problem that the visibility in the front direction is lowered when a film having polarized light reflection properties is used. In addition, as a method for solving the above problems, for example, Japanese Patent Laid-Open No. 2002-200003 discloses a film that achieves both transparency in the frontal direction and displayability of information projected from an oblique direction, and a HUD using the same.

Japanese translation of PCT publication No. 2006-512622 Japanese Patent Publication No. 2000-508081

However, when the films disclosed in Patent Documents 1 and 2 are used for in-vehicle applications, there is a problem that the haze of the film increases when the laminated glass is processed, and the visibility of the outside scenery deteriorates when the windshield is mounted. there were. An object of the present invention is to solve the problem and provide a multi-layer laminate film which has a low haze even after processing laminated glass and which can clearly display an image projected from an oblique direction.

The present invention aims to solve the above problems, and has the following configuration. That is, a multilayer laminated film in which 51 or more different thermoplastic resin layers are alternately laminated, and in differential scanning calorimetry (DSC), the temperature (T, ° C.) at which the absolute value of the amount of heat absorbed is maximum is Tm , a multilayer laminated film satisfying Tm−T ^* >27, where T ^* is a temperature (T,° C.) calculated by the following method.

Measurement method of T ^* It is measured by the following (1) and (2).
(1) A temperature differential curve of the DSC1st curve measured at intervals of 1 ° C., A (T) = dDSC / dT (mW / ° C.) graph, the minimum value of A (T) at 150 < T < Tm is Amin, Assuming that T at that time is Tmin, obtain T at the intersection of the curve A(T) and the straight line A(T)=0.2Amin in the range of T<Tmin.
(2) For each T that satisfies (1), let T ^* be the smallest T among T that always satisfies A(T)<0.2Amin in the range from T to T+5°C.

The multi-layer laminated film of the present invention can also be in the following aspects, and can also be used as an image display member or a head-up display in the following aspects.
[1] A multilayer laminated film in which 51 or more different thermoplastic resin layers are alternately laminated, and in differential scanning calorimetry (DSC), the temperature (T, ° C.) at which the absolute value of the amount of heat absorbed is maximized. A multilayer laminated film satisfying Tm−T ^* >27, where Tm and temperature (T, °C) calculated by the following method are defined as T ^* .

Measurement method of T ^* It is measured by the following (1) and (2).
(1) A temperature differential curve of the DSC1st curve measured at intervals of 1 ° C., A (T) = dDSC / dT (mW / ° C.) graph, the minimum value of A (T) at 150 < T < Tm is Amin, Assuming that T at that time is Tmin, obtain T at the intersection of the curve A(T) and the straight line A(T)=0.2Amin in the range of T<Tmin.
(2) For each T that satisfies (1), let T ^* be the smallest T among T that always satisfies A(T)<0.2Amin in the range from T to T+5°C.
[2] The multilayer laminate film of [1], wherein A(T) has a maximum value of 0.040 or less at 150<T<Tm.
[3] The multilayer laminated film according to [1] or [2], which has a transmittance of 50% or more and 100% or less for visible light incident perpendicularly to the surface of the multilayer laminated film.
[4] Rp20 and Rp60 are the reflectances (%) when p-polarized light rays are incident on the surface of the multilayer laminated film at 20° and 60°, respectively, satisfying the relationship Rp20<Rp60. The multilayer laminated film according to any one of [1] to [3].
[5] The multilayer laminate film according to any one of [1] to [4], wherein the Rp60 is 10% or more and 50% or less.
[6] The azimuth angle variation of reflectance is 10% or less when p-polarized light is incident on the surface of the multilayer laminated film at an angle of 60° with the normal. The multilayer laminated film according to any one of [1] to [5].
[7] The multilayer laminate film has a structure in which a layer (layer A) made of a first thermoplastic resin and a layer (layer B) made of a second thermoplastic resin are alternately laminated, and the first Any one of [1] to [6], wherein the thermoplastic resin is mainly composed of a crystalline polyester, and the second thermoplastic resin is mainly composed of a polyester containing a structure derived from naphthalenedicarboxylic acid or terephthalic acid. The multilayer laminated film according to 1.
[8] A projection image display member in which the multilayer laminated film according to any one of [1] to [7] is laminated on at least one surface of a transparent member.
[9] A projection image display member in which the multilayer laminated film according to any one of [1] to [7] is laminated between at least two transparent members.
[10] An image projector that projects an image, and the multilayer laminated film according to any one of [1] to [7], or the image projector according to [8] or [9]. A head-up display system comprising a projected image display member of
[11] In the light beams forming the image from the image projector, the intensity of the p-polarized component with respect to the plane of incidence when the multi-layer laminated film or the projection image display member is used as the reflecting surface is the intensity of all the light components. 51% or more of the head-up display system according to [10].

The multilayer laminated film of the present invention suppresses an increase in haze during laminated glass processing, and can achieve both visibility of the outside scenery when mounted on a windshield and display of information projected from an oblique direction. .

An example of a DSC1st curve of a multilayer laminated film satisfying Tm−T ^* >27 and Tm−T ^* ≦27. An example of a graph of A(T)=dDSC/dT (mW/° C.), which is a temperature differential curve of the DSC1st curve in FIG. Schematic diagram for explaining a method for measuring T ^* . Examples of DSC1st curves for multilayer laminate films with maximum values of A(T) at 150<T<Tm of 0.040 or less and greater than 0.040. An example of a graph of A(T)=dDSC/dT (mW/°C), a temperature differential curve of the DSC1st curve in FIG. Schematic diagram for explaining the azimuth angle of the multilayer laminate film of the present invention.

Embodiments of the present invention will be described below, but the present invention should not be construed as being limited to the embodiments including the following examples. Naturally, various changes are possible within the scope of the invention. Also, for the purpose of simplifying the explanation, part of the explanation will be given by taking as an example a multilayer laminated film having a configuration in which two different thermoplastic resin layers are alternately laminated, which is one of the preferred embodiments of the present invention. However, the same should be understood even when three or more thermoplastic resins are used.

The multilayer laminate film of the present invention must have a structure in which 51 or more different thermoplastic resin layers are alternately laminated. In the present invention, a plurality of types of thermoplastic resin layers with different compositions are present in the multilayer laminated film, and the refractive indices of these thermoplastic resin layers are arbitrarily selected within the plane of the film. If the difference is 0.01 or more in any of the directions perpendicular to , it can be considered that "a plurality of types of thermoplastic resin layers are present." In addition, the term “alternately laminated” means that layers made of different thermoplastic resins are laminated in a regular arrangement in the thickness direction.

As a specific example of such an aspect, if the multilayer laminated film consists of a layer (layer A) made of a first thermoplastic resin and a layer (layer B) made of a second thermoplastic resin, A ( BA)n, B(AB)n (n is a natural number, the same shall apply hereinafter), which are sequentially laminated. Further, the multilayer laminated film consists of a layer (layer A) made of a first thermoplastic resin, a layer (layer B) made of a second thermoplastic resin, and a layer (layer C) made of a third thermoplastic resin. In that case, the arrangement is not particularly limited, but for example, those stacked in order with a certain regularity such as C(BA)nC, C(ABC)n, C(ACBC)n, etc. is mentioned. By alternately laminating a plurality of thermoplastic resin layers with different optical properties such as refractive index in this way, light in a desired wavelength band is selectively reflected from the relationship between the difference in refractive index of each layer and the layer thickness. It is possible to express the interference reflection that makes it possible.

Further, when the number of layers of the multilayer laminate film is 50 or less, high reflectance cannot be obtained in the desired wavelength band. As the number of layers increases, the above-mentioned interference reflection can achieve a higher reflectance for light in a wider wavelength band, and a multilayer laminated film that reflects light in a desired wavelength band can be obtained. From the above viewpoint, the number of layers of the multilayer laminated film is preferably 401 or more, more preferably 801 or more. In addition, although there is no upper limit to the number of layers, as the number of layers increases, the manufacturing cost increases due to the increase in size of the manufacturing apparatus, and the handling property deteriorates due to the thicker film thickness. The layer level is the practical range.

In the multilayer laminated film of the present invention, in differential scanning calorimetry (DSC), Tm is the temperature (T, ° C.) at which the absolute value of the amount of heat absorbed is maximum, and T ^* is the temperature (T, ° C.) calculated by the following method. , it is important to satisfy Tm−T ^* >27.

T ^* is measured by the following (1) and (2).
(1) A temperature differential curve of the DSC1st curve measured at intervals of 1 ° C., A (T) = dDSC / dT (mW / ° C.) graph, the minimum value of A (T) at 150 < T < Tm is Amin, Assuming that T at that time is Tmin, obtain T at the point of intersection of curve A(T) and straight line A(T)=0.2Amin in the range of 150<T<Tmin.
(2) For each T that satisfies (1), let T ^* be the smallest T among T that always satisfies A(T)<0.2Amin in the range from T to T+5°C.

When Tm−T ^* >27 is satisfied, the multilayer laminate film has an internal haze of 0.8 or less after heat treatment at 150° C. for 2 hours. Here, the heating conditions of 150° C. for 2 hours correspond to processing conditions for producing a windshield by laminating a film with two sheets of glass. When the internal haze after heating under these conditions is 0.8 or less, even when mounted on the windshield of an automobile, the outside scenery can be visually recognized without fogging. As the value of Tm-T ^* increases, the internal haze after heating under these conditions is suppressed, and when Tm-T ^* >30, the internal haze becomes 0.5 or less, and a film with less haze can be obtained. There is no upper limit to Tm-T ^* , but since the internal haze does not fall below 0.1 when Tm-T ^* is a certain value or more, Tm-T ^* is 50 or less, preferably 40 or less. On the other hand, when Tm−T ^* ≦27, the internal haze after heating under these conditions exceeds 0.8, and the visibility of the outside scenery becomes poor when mounted on the windshield of an automobile or the like.

Tm−T ^* indicates the crystalline state of the layer B composed of the second thermoplastic resin in the multilayer laminated film, and the larger this value, the more crystalline. Therefore, as described above, in order to suppress the internal haze after heating at 150° C. for 2 hours, it is preferable that the layer B composed of the second thermoplastic resin is maintained in a crystalline state. As a method for obtaining such a multilayer laminated film, the details will be described later. A thermoplastic resin is selected so that the melting point of the thermoplastic resin is higher than the melting point of the second thermoplastic resin, and heat treatment is performed at an appropriate temperature below the melting point of the second thermoplastic resin after biaxial stretching. Furthermore, the difference between the melting point of the second thermoplastic resin and the heat treatment temperature is preferably larger than 5°C, more preferably larger than 10°C. Moreover, when the second thermoplastic resin does not have a melting point, there is a method in which the temperature of the heat treatment after the biaxial stretching is 30° C. lower than the melting point of the first thermoplastic resin. As a result, the second thermoplastic resin maintains a crystalline state, Tm−T ^* >27, and the internal haze after heating at 150° C. for 2 hours becomes 0.8 or less. T ^* >30, and the internal haze is 0.5 or less. On the other hand, when the heat treatment temperature is higher than the melting point of the second thermoplastic resin, or higher than the melting point of the first thermoplastic resin by 30°C or higher, the second thermoplastic resin in the multilayer laminate film is in a molten state. be. If this state is heated at 150° C. for 2 hours, the second thermoplastic resin is recrystallized and grows as coarse crystals, which undesirably increases the internal haze.

In addition to the selection of the second thermoplastic resin and the selection of the temperature at which the heat treatment is performed, ^the optimization of the stretching ^conditions (stretch ratio , stretching temperature, and stretching speed). The specific stretching method and the preferred range of each will be described later, but the higher the stretching ratio, the more effective the orientation of the molecular chains of the first and second thermoplastic resins, and the better the crystallinity. Internal haze can be suppressed. In addition, by setting the stretching temperature to a temperature slightly higher than the glass transition temperatures of the two thermoplastic resins, a suitable mobility is created in the molecular chains and the orientation of the molecular chains during stretching becomes effective. On the other hand, when the stretching temperature is too high, the mobility of the molecular chains becomes high and fluid, so that the molecular orientation does not occur and the crystallinity reaches a ceiling. From the above point of view, the stretching temperature is more preferably 3° C. to 15° C. higher than the glass transition temperature. Also, when the stretching speed is the same and the stretching temperature is the same, the higher the stretching speed, the more effective the orientation of the molecular chains.

Further, as a method of making Tm−T ^* >27 (preferably Tm−T ^* >30), there is a method of lowering the intrinsic viscosity (IV) of the second thermoplastic resin. The intrinsic viscosity of the resin depends on the average molecular weight, molecular weight distribution, and molecular chain form (linear or branched). The lower the intrinsic viscosity, the lower the average molecular weight or the linear molecular chain. The lower the intrinsic viscosity, the less the entanglement of the molecular chains during stretching, which is advantageous for orientation, so that the crystallinity can be improved. On the other hand, if the intrinsic viscosity is too low, the mechanical properties of the stretched film are significantly reduced. and a more preferable intrinsic viscosity is 0.50 or more and 0.60 or less.

Next, methods for achieving Tm, T ^* , Tm−T ^* , and Tm−T ^* >27 will be described with reference to FIGS. FIG. 1 shows DSC1st curves of multilayer laminated films satisfying Tm−T ^* >27 and Tm−T ^* ≦27, respectively; FIG. 2 shows temperature differential curves of the DSC1st curves; °C). The temperature differential curve of the DSC1st curve, A(T)=dDSC/dT (mW/°C), indicates the slope of the tangent line of the DSC1st curve at each temperature, and when A(T)=0, the DSC1st curve is minimal. or show a local maximum. In particular, when A(T) changes from negative to positive with A(T)=0 as the boundary, it corresponds to the existence of a peak indicating the melting enthalpy (ΔHm) at that temperature.

In FIG. 1, there is a peak at 200° C. to 280° C. where the amount of heat absorbed is maximum, and the temperature at which the absolute value of the amount of heat absorbed is maximum or minimum is defined as Tm. The peak of the amount of absorbed heat corresponds to the melting point of any one of a plurality of different thermoplastic resins. The thermoplastic resin preferably exhibits crystallinity, and more preferably contains a crystalline polyester as a main component, as will be described later.

T ^* obtained by the above-described measurement method indicates the minimum temperature at which A(T) is below a certain value, that is, the slope of the tangent line of the DSC1st curve is below a certain value. In FIG. 1, the DSC1st curve (solid line) of the multilayer laminated film with Tm−T ^* >27 shows less heat absorption from around 200° C. than the DSC1st curve (dotted line) of the multilayer laminated film with Tm−T ^* ≦27. , and the degree of decrease is increasing as a trend in the graph. That is, FIG. 2 shows that the value of A(T) is smaller in the multi-layer laminate film satisfying Tm-T ^* >27 at around 200.degree. This is because the layer B composed of the second thermoplastic resin other than the first thermoplastic resin is in a crystalline state and melts to absorb heat. . On the other hand, in the multilayer laminated film satisfying Tm-T ^* ≤ 27, the layer B composed of the second thermoplastic resin is not in a crystalline state, and the refractive index in the direction parallel to the film surface and the refractive index perpendicular to the film surface are There is an isotropic amorphous state with a difference of less than about 0.01. Therefore, there is no heat absorption near 200° C., and only the melting peak derived from the first thermoplastic resin is measured in the DSC1st curve.

Next, a method for measuring T ^* will be described with reference to FIG. As described above, T ^* is the minimum temperature of the tangents of the DSC1st curve at which the slope is less than a certain value. As described in T ^* measurement method (1), where Amin is the minimum value of A(T) at 150<T<Tm, and Tmin is T at that time, straight line A(T) in the range of T<Tmin = 0.2 Amin, respectively. Here, 0.2Amin is 1/5 of the minimum value Amin at 150<T<Tm of A(T), and when A(T) is 1/5 or less of the minimum value Amin, This corresponds to measuring the heat absorption resulting from the melting of the first or second thermoplastic resin in the DSC1st curve. On the other hand, when A(T) is higher than 1/5 of the minimum value Amin, it corresponds to that the heat absorption due to melting of the thermoplastic resin constituting the multilayer laminated film is not measured. Thus, the intersection T of the curve A(T) and the straight line A(T)=0.2Amin is obtained.

Subsequently, with respect to the measurement method (2) of T ^* , among the T obtained by the measurement method (1), the smallest T among the Ts that always satisfy A (T) < 0.2 Amin in the range of T to T + 5 ° C. be T ^* . As described above, A(T)=0.2Amin is a threshold value indicating the presence or absence of heat absorption due to melting of the first or second thermoplastic resin. and the melting behavior of the thermally crystallized portion of the first thermoplastic resin due to the heat treatment step. For example, in FIG. 3, there are five T points T1 to T5 that correspond to the T ^* measurement method (1). It is T3 and T5 that always satisfy A(T)<0.2Amin in the range of T to T+5° C. at each T, and since T3 is the smallest among these, T3 is T ^* . T3 indicates the melting peak derived from the second thermoplastic resin, and T5 indicates the melting peak of the first thermoplastic resin. On the other hand, T such as T1, where A(T)≧0.2Amin in the range from T to T+5° C., indicates the melting peak of the thermally crystalline portion of the first thermoplastic resin due to the heat treatment.

In the multilayer laminated film of the present invention, the maximum value of A(T) at 150<T<Tm is preferably 0.040 or less. Regarding A(T), when the maximum value at 150<T<Tm is 0.040 or less, the reflectance (%) when p-polarized light is incident on the surface of the multilayer laminated film at 60°. is 10% or more, and the luminance can be maintained to the extent that a clear projected image is obtained.

Here, the maximum value of A(T) for 150<T<Tm will be described. 4 and 5 are graphs of DSC 1st curves and A(T) of multilayer laminate films with maximum values of A(T) at 150<T<Tm of 0.040 or less and more than 0.040, respectively. At 150<T<Tm, A(T)>0 is established in the temperature region where the melting peak of the second thermoplastic resin has passed and the temperature tends to rise as shown in FIG. The larger the maximum value of A (T), the larger the melting peak (melting enthalpy is 3 J / g or more) of the melting enthalpy (ΔHm) of the second thermoplastic resin. Layer B is in the crystalline state. On the other hand, if the maximum value of A(T) is less than or equal to 0.040, which means there is no peak or peaks below 3 J/g, layer B is in a crystallographically relaxed state. The maximum value of A(T) is 0.040 or less because the melting enthalpy of the melting peak derived from thermal crystallization by heat treatment of the first thermoplastic resin is less than 3 J/g.

Regarding A (T), in order for the maximum value at 150 < T < Tm to satisfy 0.040 or less, if the second thermoplastic resin has a melting point, the melting point of the first thermoplastic resin must be the second A thermoplastic resin is selected so as to have a melting point higher than the melting point of the second thermoplastic resin, and heat treatment is performed at a temperature 20° C. lower than the melting point of the second thermoplastic resin after biaxial stretching. In addition, a method of performing heat treatment at a temperature lower than the melting point of the second thermoplastic resin by 15°C or higher is preferable, and a method of performing heat treatment at a temperature lower than the melting point of the second thermoplastic resin by 10°C or higher is more preferable. When the second thermoplastic resin does not have a melting point, a method of carrying out the heat treatment after the biaxial stretching at a temperature not less than 60° C. lower than the melting point of the first thermoplastic resin can be used. In this way, the crystals of the layer B in the multilayer laminated film are relaxed, the refractive index in the direction perpendicular to the film surface increases, and the refractive index difference in the direction perpendicular to the film surface between the two thermoplastic resin layers is developed. As a result, the reflectance becomes 10% or more when a p-polarized light beam is incident on the film surface at an angle of 60°. In addition, it is preferable to set this refractive index difference to 0.050 or more. Regarding the upper limit of the heat treatment temperature, as described above, the crystal state of the layer B is relaxed and the refractive index in the direction perpendicular to the film surface increases, while the internal haze increases after heating at 150 ° C. for 2 hours. If there is a melting point of the second thermoplastic resin, it is about the melting point. On the other hand, with respect to A(T), when the maximum value at 150<T<Tm is greater than 0.040, the layer B is in a crystalline state, so the direction perpendicular to the film plane of the crystalline resin layer A The refractive index difference is less than 0.050 and no difference is produced. Therefore, the reflectance (%) is less than 10% when p-polarized light is incident at 60°, and a projected image that is obliquely incident cannot be clearly viewed.

The multilayer laminated film of the present invention has a transmittance of 50% or more and 100% or less for visible light incident perpendicularly to the surface of the multilayer laminated film (meaning an angle of 0° with respect to the normal to the surface of the multilayer laminated film). Preferably. Here, "the transmittance of visible light that is perpendicularly incident on the surface of the multilayer laminated film is 50% or more and 100% or less" specifically means light with a wavelength of 400 to 700 nm that is perpendicularly incident on the surface of the multilayer laminated film. The average transmittance of is 50% or more and 100% or less. Due to the high transmittance of light in the visible light region with a wavelength of 400 to 700 nm, it has transparency like transparent glass or transparent multilayer film, and the background can be seen through the multilayer film from a direction perpendicular to the surface of the multilayer film. A good visibility of the background can be obtained when observing the . From the above viewpoint, the transmittance is preferably 70% or higher, more preferably 80% or higher, and even more preferably 85% or higher. If the transmittance is 85% or more, the user can visually recognize the background without feeling the presence of the multi-layer laminated film. Note that the upper limit of the transmittance is preferably 99% from the viewpoint of easiness of realization. The transmittance of light incident perpendicularly to the surface of the multi-layer laminate film is obtained by measuring the transmittance of light with a wavelength of 400 to 700 nm at an incident angle of θ = 0° with a spectrophotometer in increments of 1 nm, and calculating the average value. can be measured (detailed measurement conditions will be described later).

Such a multilayer laminate film can be obtained by reducing the difference in refractive index between two thermoplastic resin layers in the direction parallel to the film surface. If the refractive index difference in the direction parallel to the film surface is 0.06 or less, the transmittance is 50% or more, and if 0.04 or less, the transmittance is 70% or more, and the refractive index difference is 0.015. If it is below, it becomes easy to make the said transmittance|permeability 85% or more. In addition, the "refractive index difference in the direction parallel to the film surface" means the difference in in-plane refractive index between two types of thermoplastic resin layers (when the two types of layers are layer A and layer B, layer A and The absolute value of the in-plane refractive index difference of the layer B).

In the multilayer laminated film of the present invention, when the reflectance (%) is Rp20 and Rp60 when p-polarized light is incident on the surface of the multilayer laminated film at 20° and 60°, respectively, Rp20<Rp60. Satisfying relationships are preferred. The reflectance referred to here is the average reflectance of light at a wavelength of 400 nm to 700 nm. It is suitable for evaluating the visibility of information that the plane of incidence coincides with the plane of incidence of light rays forming the image from the image projector on the resin film surface.

Here, a general transparent substrate such as glass, a refractive index difference between two thermoplastic resin layers of a multilayer laminated film in a direction perpendicular to the film surface is less than 0.050, or two thermoplastic resins When the refractive index difference between the layers in the direction parallel to the film surface is greater than 0.020, as the incident angle is gradually increased from 20° with respect to the normal to the transparent substrate or film surface, the polarized light becomes The reflectance of p-polarized light, which is one of the light beams, decreases, and the reflectance exhibits a minimum behavior near 60°, so that the relationship Rp20<Rp60 is no longer satisfied. Therefore, when an image is projected onto the film at an incident angle of about 60° where the reflectance is minimal, the visibility of the displayed image is very poor due to the low reflectance. On the other hand, when the relationship of Rp20<Rp60 is satisfied, the displayed image can be clearly viewed when projected from an oblique direction near the incident angle of 60°, and can be suitably used for HUD.

In order to satisfy this relational expression, a method of adjusting the refractive index difference in the direction perpendicular to the film surface between two thermoplastic resin layers in the multilayer laminated film can be used. 050 or more is preferable. Also, the difference in refractive index between the two thermoplastic resin layers in the direction parallel to the film surface is preferably small, more preferably 0.020 or less. As a result, the refractive index difference in the direction perpendicular to the film plane between the two thermoplastic resin layers at an incident angle of 20° is higher than the refractive index difference in the direction perpendicular to the film plane between the two thermoplastic resin layers at an incident angle of 60°. increases, satisfying the relationship Rp20<Rp60.

The multilayer laminate film of the present invention preferably has an Rp60 of 10% or more and 50% or less. When Rp60 is 10% or more, the projected image can have sufficient brightness for visual recognition even when the projection angle is 60° when a p-polarized image is projected onto the multilayer laminated film. The above is more preferable. On the other hand, when the Rp60 is 50% or less, the transmittance of the light reflecting the background does not become excessively low, so that the difficulty of visually recognizing the background through the multilayer laminated film is reduced. From the above viewpoint, Rp60 is more preferably 10% or more and 40% or less.

In order for Rp60 to be 10% or more and 50% or less, a method of adjusting the difference in refractive index in the direction perpendicular to the film surface between two thermoplastic resin layers in the multilayer laminated film can be used. It is preferable to set the index difference to 0.050 or more and 0.12 or less. Also, the difference in refractive index between the two thermoplastic resin layers in the direction parallel to the film surface is preferably small, more preferably 0.020 or less. Rp60 can also be increased by increasing the number of layers, and the preferred number of layers is as described above.

In the multilayer laminated film of the present invention, the azimuth angle variation of the reflectance when p-polarized light is incident on the surface of the multilayer laminated film at an angle of 60° with respect to the normal is 10% or less. preferable. Here, the azimuth angle means each azimuth angle (0°, 45°, 90°, 135°, 180°), and the direction of the main orientation axis means the direction in which the degree of orientation is the largest in the plane of the film. The degree of orientation can be measured by a known molecular orientation meter. As the molecular orientation meter, for example, a molecular orientation meter MOA-7015 manufactured by current Oji Scientific Instruments Co., Ltd. can be used. Azimuth angle variation is Rp60 (0°), Rp60 (45°), Rp60 (90°), Rp60 (135°) measured at the above azimuth angles (0°, 45°, 90°, 135°, 180°) , Rp60 (180°).

Rp60 (0°), Rp60 (45°), Rp60 (90°), Rp60 (135°), and Rp60 (180°) are p-polarized light with a wavelength of 400 to 700 nm at an incident angle of θ = 60° with a spectrophotometer. It can be measured by measuring the reflectance in increments of 1 nm and calculating the average value. Here, the azimuth angle, which is the direction of inclination, is defined as 0°, 45°, 90°, 135°, and 180° in the clockwise direction, with the azimuth angle in the direction of the main orientation axis of the multilayer laminate film being 0°. adopt. Since the azimuth angle variation of Rp60 is 10% or less, displayability such as brightness of the information can be maintained at the same level regardless of the azimuth of the image projected. This effect is one of the features of the multilayer laminate film of the present invention, and is an effect that cannot be achieved with a polarizing reflective film.

In order to reduce the azimuthal angle variation of Rp60, for example, the in-plane refractive index unevenness of the multilayer laminated film of the present invention can be reduced. The biaxial stretching of the film may be carried out so as to reduce the difference in the orientation state between the longitudinal direction and the width direction of the film. The stretching conditions for reducing the difference in the orientation state between the longitudinal direction and the width direction vary depending on the thermoplastic resin used and the combination thereof. This can be achieved under conditions where the magnification is slightly increased. Reducing the difference in drawing speed between the longitudinal direction and the width direction is also effective in reducing the difference in orientation. More preferably, the azimuth angle variation of Rp60 is 5% or less, and more preferably 2%. The lower limit of the azimuth variation of Rp60 is 0.1% from the viewpoint of feasibility. Both can be achieved by stretching the film in the longitudinal direction and the width direction at the optimum ratio.

The multilayer laminated film of the present invention has a structure in which a layer (layer A) made of a first thermoplastic resin and a layer (layer B) made of a second thermoplastic resin are alternately laminated, It is preferable that the plastic resin contains a crystalline polyester as a main component, and the second thermoplastic resin contains a polyester containing a structure derived from terephthalic acid or naphthalenedicarboxylic acid as a main component. Here, the "first thermoplastic resin" refers to the entire resin component that constitutes the layer A, and the "second thermoplastic resin" refers to the entire resin component that constitutes the layer B. "The layer A contains crystalline polyester as a main component" means that the first thermoplastic resin contains 60% by mass or more and 100% by mass or less of crystalline polyester. In addition, "the layer B is mainly composed of a polyester containing a structure derived from terephthalic acid or naphthalene dicarboxylic acid" means that 60% by mass or more and 100% by mass or less of the dicarboxylic acid component in the second thermoplastic resin of terephthalic acid and/or naphthalenedicarboxylic acid.

The multilayer laminate film of the present invention may contain dicarboxylic acid and diol components other than the resin components described above. For example, aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid and the like can be mentioned. Aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid and their ester derivatives. Among them, terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferred. These acid components may be used alone, or two or more of them may be used in combination.

Examples of diol components include ethylene glycol, paraxylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1, 5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2- Bis(4-hydroxyethoxyphenyl)propane, isosorbate, spiroglycol, bisphenoxyethanolfluorene (BPEF) and the like can be mentioned. Among them, ethylene glycol and polyalkylene glycol are particularly preferred. These diol components may be used alone or in combination of two or more.

The multilayer laminate film of the present invention can be produced by laminating the above resins, for example, by the method described below. First, two kinds of thermoplastic resins are prepared in the form of pellets or the like. If necessary, the pellets are dried in hot air or under vacuum and then supplied to separate extruders. In an extruder, a thermoplastic resin is heated and melted at a temperature above its melting point, extruded with a gear pump or the like to make the extrusion rate uniform, and foreign matter and denatured resin are removed through a filter or the like. Next, two kinds of thermoplastic resins are fed into a multi-layer lamination device through separate channels and laminated alternately. A multi-manifold die, a feed block, a static mixer, or the like can be used as the multi-layer lamination device, and it is particularly preferable to use a feed block having 50 or more fine slits. When such a feed block is used, the apparatus does not become extremely large, so there is little foreign matter due to thermal deterioration, and high-precision stacking is possible even when the number of layers to be stacked is extremely large. In addition, lamination accuracy in the width direction is remarkably improved as compared with the conventional technology. Moreover, in such an apparatus, since the thickness of each layer can be adjusted by the shape (length and width) of the slit, it is easy to achieve an arbitrary layer thickness.

Next, the laminated molten resin is formed into a sheet by using a spinneret, extruded onto a cooling body such as a casting drum, and solidified by cooling to obtain a casting film. At this time, it is preferable to use a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode to bring the molten resin sheet into close contact with a cooling body such as a casting drum by electrostatic force, thereby rapidly cooling and solidifying it.

The cast film thus obtained is preferably biaxially stretched. Here, biaxial stretching refers to stretching in the longitudinal direction and the width direction, the longitudinal direction refers to the running direction of the film, and the width direction refers to the direction orthogonal to the longitudinal direction in the film plane. The stretching may be carried out in two directions successively (sequential biaxial stretching) or in two directions at the same time (simultaneous biaxial stretching). Further, re-stretching may be performed in the longitudinal direction and/or the width direction.

In the case of simultaneous biaxial stretching, the stretching speed is preferably 5 to 80%/second, more preferably 10 to 50%/second. Simultaneous biaxial stretching is usually carried out using a tenter while gripping both ends of the film with clips, and the stretching ratio is preferably 2 to 5 times in both the longitudinal direction and the width direction. The stretching temperature is preferably a temperature higher than the glass transition temperature of the resin having a high glass transition temperature to a temperature 100° C. higher than the glass transition temperature of the resin having a high glass transition temperature among the polyester resins that are the main components of each layer constituting the cast film to be stretched. More preferably, the temperature is 3° C. higher than the glass transition temperature of the resin having a high glass transition temperature to 15° C. higher than the glass transition temperature of the resin having a high glass transition temperature.

The film thus biaxially stretched is preferably heat-treated in a tenter at a temperature 100° C. to 150° C. higher than the stretching temperature. If the second thermoplastic resin has a melting point, it should be at least 20°C lower than the melting point, and more preferably at least 15°C lower than the melting point and 5°C lower than the melting point. If the second thermoplastic resin does not have a melting point, the preferred heat treatment temperature is 60° C. higher than the melting point of the first thermoplastic resin or higher and 30° C. lower than the melting point of the first thermoplastic resin. The definitions of the first and second thermoplastic resins are as described above. During the heat treatment, it is preferable to perform the relaxation treatment in the longitudinal direction and the width direction at a relaxation rate of 0.01 to 2%/sec. The relaxation ratio is preferably 0.90 to 0.99 times the width of the film immediately before relaxation. The multilayer laminated film thus obtained is then uniformly and gradually cooled to room temperature, and then the edge portions at both ends held by the clips of the tenter are cut and wound up.

In the case of sequential biaxial stretching, the stretching rate in the longitudinal direction is preferably 50-300%/sec, more preferably 70-150%/sec. Stretching in the longitudinal direction is usually carried out by a difference in peripheral speed of the rolls, and the stretching ratio is preferably 1.5 to 5 times, more preferably 3 to 5 times, even more preferably 3.8 to 5 times. The stretching temperature is the same as in the simultaneous biaxial stretching. Subsequently, the uniaxially stretched film obtained by stretching in the longitudinal direction is stretched in the width direction at a stretching rate of 5 to 40%/second, more preferably 8 to 30%/second, and still more preferably 15 to 20%/second. preferably. Usually, the stretching in the width direction is carried out by using a tenter and conveying while holding both ends of the film with clips, and the stretching ratio is preferably 1.5 to 6.5 times, more preferably 3 to 5 times, and 4 to Five times is more preferred. Further, the stretching temperature in the width direction is more preferably 10° C. to 20° C. higher than the stretching temperature in the longitudinal direction.

The film thus biaxially stretched is also preferably heat-treated in the same manner as in the simultaneous biaxial stretching. At that time, it is preferable to perform additional stretching in the width direction at a stretching rate of 5 to 20%/sec in the first half of the heat treatment, and to perform relaxation treatment in the width direction at a relaxation rate of 0.01 to 1%/sec in the second half of the heat treatment. . The ratio of additional stretching in the width direction is preferably 1.05 to 1.20 times, and the relaxation ratio is preferably 0.90 to 0.99 times the width of the film immediately before relaxation. The multilayer laminated film thus obtained is then uniformly and gradually cooled to room temperature, and then the edge portions at both ends held by the clips of the tenter are cut and wound up. Thus, the multilayer laminate film of the present invention can be obtained.

The projection image display member of the present invention will be described below. The projection image display member of the present invention is obtained by laminating the multilayer laminated film of the present invention on at least one surface of a transparent member, or by laminating the multilayer laminated film of the present invention between at least two transparent members. The projection image display member plays a role of projecting an image so as to be visually recognized by the user by reflecting the projection image emitted from the image projection device positioned in an oblique direction. In the projection image display member of the present invention, the multilayer laminate film of the present invention has a high transparency to visible light from the front and has a property that the reflectance of visible light from an oblique direction varies little depending on the irradiation angle. While ensuring the visibility of the background, it is possible to reduce the luminance difference of the image due to the difference in the projection angle.

Examples of transparent members include glass and transparent resin substrates, and the thickness thereof is preferably 1 mm or more in order to provide support. The upper limit of the thickness of the transparent member is not particularly limited. Specific examples of the transparent resin substrate in the projection image display member include polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, cycloolefin, polymethylpentene and copolymers thereof, and acrylonitrile-butadiene-styrene copolymer. etc. are preferable.

Examples of the method for laminating the transparent member and the multilayer laminate film of the present invention include lamination by forming an adhesive layer using a pressure-sensitive adhesive or adhesive. Examples of the pressure-sensitive adhesive or adhesive include vinyl acetate. Resin, vinyl chloride/vinyl acetate copolymer, ethylene/vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubber, styrene/butadiene rubber, natural rubber, chloroprene rubber, Polyamide-based, epoxy resin-based, polyurethane-based, acrylic resin-based, cellulose-based, polyvinyl chloride, polyacrylic acid ester, polyisobutylene, and the like can be mentioned. In addition, adhesiveness modifiers, plasticizers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, colorants, cross-linking agents, etc. may be added to these adhesives and adhesives. . Examples of the form of these adhesives before processing include liquid, gel, block, powder, and film. Solvent volatilization, moisture curing, heat curing, curing agent mixing, anaerobic curing, ultraviolet curing, heat melting cooling, pressure sensing, and the like can be used as methods for solidifying the adhesive layer. Examples of the lamination method include lamination molding and injection molding, and the projection image display member is produced by using heating, pressurization, and the above-described method for solidifying the adhesive layer. Furthermore, a hard coat layer, an abrasion-resistant layer, an anti-scratch layer, an anti-reflection layer (hereinafter sometimes referred to as an "AR layer"), a color correction layer, an ultraviolet absorption layer, and a light stabilization layer are applied to the surface of the projection image display member. It may have functional layers such as a layer (HALS), a heat absorbing layer, a printing layer, a gas barrier layer, an adhesive layer, and a transparent electrode layer.

When the projection image display member of the present invention is formed by laminating the multilayer laminated film of the present invention on at least one surface of a transparent member, the image projector is arranged on the side of the multilayer laminated film that is not in contact with the adhesive layer. is preferred. Further, it is preferable to have an AR layer on the surface of the multi-layer laminated film on which glass is not laminated, in order to suppress multiple images. Here, the AR layer refers to a layer having a refractive index lower than that of the surface of the multi-layer laminated film, and reduces the reflectance by the interference effect of light. Methods for forming the AR layer include wet methods such as roll coating, gravure coating, spin coating, and spraying, and dry methods such as vacuum evaporation, sputtering, and CVD, and any of these methods may be used. , the wet method is more preferable from the viewpoint of productivity.

When the projection image display member of the present invention is formed by laminating the multilayer laminated film of the present invention on at least one surface of a transparent member, or by laminating between at least two transparent members, the glass used in such a structure is The thickness is preferably in the range of 0.5 mm to 6.0 mm from the viewpoint of achieving both light weight and high strength of the windshield. From the above viewpoint, the thickness of the glass is more preferably 1.0 mm to 5.0 mm.

When the projection image display member of the present invention is formed by laminating the multilayer laminated film of the present invention on at least one surface of a transparent member, the thickness of the adhesive layer should be 2 μm to 500 μm from the viewpoint of enhancing the durability of the windshield. is preferred. Further, when the projection image display member of the present invention is formed by laminating the multilayer laminated film of the present invention between at least two transparent members, in order to increase the durability of the windshield and obtain good workability, The thickness of the adhesive layer is preferably 30 μm to 800 μm.

When the projection image display member of the present invention is formed by laminating the multilayer laminated film of the present invention on at least one surface of a transparent member or by laminating between at least two transparent members, these structures are produced. In this case, it is preferable to subject the surface of the multilayer laminated film or glass to surface treatment such as corona treatment, plasma treatment, or primer treatment in order to increase the adhesion strength at the lamination interface. The HUD system of the present invention may have a hard coat layer on the surface of the outermost layer of the laminate containing the multilayer laminated film for the purpose of surface protection. The hard coat layer may also have the function of the AR layer.

Next, a HUD system using the multilayer laminate film of the present invention will be described. The HUD system of the present invention is a HUD system comprising the multilayer laminated film of the present invention or the projection image display member of the present invention, and an image projector for projecting an image onto the display surface thereof.

The HUD system of the present invention is used by being mounted on transportation equipment, buildings, electronic signboards, and the like. Transportation equipment refers to means of transportation driven by passengers, such as aircraft, ships, automobiles, and railroads. The information required by the user is displayed on the information display unit and used. At that time, the positional relationship between the projection light source and the windshield is adjusted so that the image projected from the projection light source is reflected by the information display section and reaches the passenger's field of vision. The incident angle of projection is preferably in the range of 40 to 75°, more preferably 50 to 70°, from the viewpoint of reducing the size of the HUD system and improving visibility.

In the HUD system of the present invention, the intensity of the p-polarized light component is 51% of the intensity of the total light component with respect to the plane of incidence when the multi-layer laminated film is used as the reflecting surface in the light rays forming the image from the image projector. It is important that Here, p-polarized light is an electromagnetic wave whose electric field component is parallel to the plane of incidence (linearly polarized light that oscillates parallel to the plane of incidence), and s-polarized light is an electromagnetic wave whose electric field component is perpendicular to the plane of incidence (linear light that oscillates perpendicular to the plane of incidence). polarization). The fact that the light rays forming the image projected from the image projector contain many p-polarized components reflects the light on the front and back surfaces of the windshield projection part (information display part) of the transportation equipment, This is important in that it suppresses multiple images in which the displayed images appear to be multiple, which is caused by deviations in the course of the light rays.

When s-polarized light is included in the light beams forming the image projected from the image projector, reflection occurs on the front and back surfaces of the members forming the information display unit, so that a multiple image is visually recognized. is incident at an incident angle near Brewster's angle, almost no reflection occurs on the front and back surfaces of the information display section. Further, by including a large amount of p-polarized light in the light beams forming the image projected from the image projector, it is possible to suppress the decrease in brightness of the display image even when wearing polarized sunglasses. Polarized sunglasses block the s-polarized component in order to suppress glare from the ground and glare on the windshield, which is the majority of the s-polarized component when the ground or water surface is used as a reflective surface, and to ensure clear vision. is designed to Therefore, the brightness of the displayed image can be maintained even when wearing polarized sunglasses by including many p-polarized light beams with different polarization directions by 90 degrees in the light beams forming the image projected from the image projector. From these points of view, the ratio of the p-polarized light component in the light projected from the image projector is preferably as high as possible, more preferably 90% or more, and still more preferably 99% or more. For the reason described above, the upper limit of the proportion of the p-polarized light component in the light emitted from the projection light source is not particularly limited, and is substantially 100%.

EXAMPLES The multilayer laminate film of the present invention will be described below using examples. However, the multilayer laminate film of the present invention is not limited to the following aspects.

[Method for measuring physical properties and method for evaluating effect]
Methods for evaluating physical property values and methods for evaluating effects are as follows.

(1) Lamination number and surface layer thickness of multilayer laminated film A sample cut out in cross section using a microtome was observed using a transmission electron microscope (TEM) to determine the number of layers laminated and the thickness of the surface layer of the multilayer laminated film. confirmed. The cross-sectional photograph was taken using a transmission electron microscope Model H-7100FA (manufactured by Hitachi, Ltd.) at an acceleration voltage of 75 kV. In addition, the thickness of the surface layer was measured by the length measurement function of the microscope.

(2) Measurement method of Tm and T ^* Measured by the following (A) to (C).
(A) Weigh 5 mg of a multilayer laminated film with an electronic balance, sandwich it with an aluminum pan, and use a robot DSC-RDC220 differential scanning calorimeter manufactured by Seiko Instruments Inc., according to JIS-K-7122 (2012). The temperature was raised from 25° C. to 300° C. at a rate of 20° C./min, and measurements were taken at intervals of 1° C. to obtain a DSC1st curve. The temperature at which the absolute value of the amount of heat absorbed was maximum was defined as Tm (°C).
(B) In the temperature differential curve of the obtained DSC1st curve, A (T) = dDSC / dT (mW / ° C.), the minimum value of A (T) at 150 < T < Tm is Amin, and T at that time is Tmin, one or more Ts are obtained at which the curve A(T) and the straight line A(T)=0.2Amin intersect in the range of T<Tmin.
(C) For each T that satisfies (B), among Ts that always satisfy the relational expression of A(T)<0.2Amin in the range from T to T+5° C., T ^* was the smallest T.

(3) Visible light transmittance of multilayer laminated film With a standard configuration (solid measurement system) of a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., a wavelength of 400 to 700 nm at an incident angle θ = 0 ° The transmittance was measured in increments of 1 nm, the average transmittance was obtained, and the obtained value was defined as the visible light transmittance of the multilayer laminated film. Measurement conditions: the slit was set to 2 nm (visible)/automatic control (infrared), the gain was set to 2, and the scanning speed was set to 600 nm/min.

(4) Orientation Axis A phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments Co., Ltd. was used. A film sample cut out in a size of 3.5 cm×3.5 cm was placed in the apparatus, and the orientation axis direction in the plane of the film at an incident angle of 0° was measured.

(5) Reflectance of multilayer laminated film (Rp20, Rp60),
A spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. is attached with a variable angle reflection unit and a Glan-Taylor polarizer, and the wavelength range is 400 to 700 nm at an incident angle θ of 20° and 60° with respect to the film surface. The reflectance of p-polarized light was measured in 1 nm steps. From the obtained reflectances, Rp20 and Rp60 were determined as average reflectances of p-polarized light in the wavelength range of 400 nm to 700 nm at incident angles of 20° and 60°. Note that the direction of inclination was the direction along the orientation axis.

(6) Reflectance of multilayer laminated film (Rp60 (0°), Rp60 (45°), Rp60 (90°), Rp60 (135°), Rp60 (180°), azimuth angle variation)
A spectrophotometer manufactured by Hitachi, Ltd. (U-4100 Spectrophotometer) is attached with an attached angle-variable reflection unit and a Glan-Taylor polarizer. Reflection of p-polarized light in the wavelength range of 400 to 700 nm at an incident angle of θ = 60° with respect to the normal to the film surface, with each of the five azimuth angles of 45°, 90°, 135°, and 180° as the plane of incidence. The index was measured in 1 nm steps. From the obtained reflectance, Rp60 (0 °), Rp60 (45 °), Rp60 (90 °), Rp60 as the average reflectance of p-polarized light in the wavelength range of 400 nm to 700 nm at an incident angle of 60 ° in each azimuth direction. (135°) and Rp60 (180°) were obtained. Furthermore, the difference between the maximum and minimum values of Rp60 (0°), Rp60 (45°), Rp60 (90°), Rp60 (135°), and Rp60 (180°) was defined as the azimuth angle variation.

(7) Internal haze of multilayer laminated film after heat treatment at 150 ° C. for 2 hours The multilayer laminated film was placed in an atmosphere of 150 ° C. for 2 hours, then placed in a quartz cell for liquid measurement, filled with liquid paraffin, and subjected to the Suga test. Measurement (JIS K 7136: 2000) was performed using a haze meter (HGM-2DP) manufactured by Ki Co., Ltd. to measure the internal haze excluding the film surface haze. The measurement was repeated 10 times by randomly changing the measurement position, and the average value was taken as the internal haze value.

(8) Melting point of resin Resin pellets were measured in the same manner as in method (2)(A). For data analysis, the melting point (Tm) was measured using Disk Session SSC/5200 manufactured by the same company. The melting point was defined as the peak temperature at which the melting enthalpy (ΔHm) was 3 J/g or more.

(9) Refractive Index of Layer A of Multilayer Laminated Film Using a prism coupler SPA-400 manufactured by Cylon Technology Co., Ltd., the refractive index of the outermost layer of the multilayer laminated film was measured. The wavelength of the laser used for the measurement was 633 nm. For the refractive index, the average value of the values measured from the direction of the main orientation axis and the value measured from the direction perpendicular to the direction of the main orientation axis was obtained by averaging the values obtained from both outermost layers.

(10) Refractive index of layer B of multilayer laminated film Since layer B is a layer inside the multilayer laminated film, it is not a multilayer laminated film, but a film of layer B resin alone prepared under the same stretching conditions and heat treatment conditions as the multilayer laminated film. , a prism coupler SPA-400 manufactured by Cylon Technology Co., Ltd. was used to measure the refractive index. The wavelength of the laser used for the measurement was 633 nm, and the in-plane refractive index was obtained by averaging the values obtained on both surfaces of the film in the direction of the main orientation axis and the direction perpendicular to the direction of the main orientation axis. For the normal refractive index, the average value of the values measured from the direction of the main orientation axis and the value measured from the side perpendicular to the direction of the main orientation axis was obtained from both surfaces of the film.

(11) Visibility of the outside scenery On both sides of the multilayer laminated film, a glass plate with a thickness of 2 mm was pressed and laminated at 150°C for 2 hours via a polyvinyl butyral resin (adhesive layer). A display member was obtained. The visibility of the outside scenery was visually evaluated through a projection image display member inclined at 60° with respect to the vertical direction. Table 2 shows the evaluation results.
Composition: glass (thickness 2 mm)/adhesive layer (thickness 350 μm)/multilayer laminated film (thickness 75 μm)/adhesive layer (thickness 350 μm)/glass (thickness 2 mm).
Evaluation criteria are as follows.
⊚: There is no fogging in the glass, and the outside scenery can be clearly visually recognized.
◯: Slight fogging is observed in the glass, but the outside scenery can be visually recognized without any problem.
x: Clouding is observed in the glass, and the visibility of the outside scenery is poor.

(12) Information display property A HUD system comprising the projection image display member obtained in (11) and a projection light source that generates and radiates p-polarized light is produced, and when an image is projected at an incident angle of 60° Information displayability was visually evaluated. Table 2 shows the evaluation results.
Evaluation criteria are as follows.
A: The display image projected onto the projection image display member was clearly visible.
◯: The display image projected onto the projection image display member was inferior in sharpness, but could be visually recognized.
Δ: The display image projected onto the projection image display member has poor clarity, but is slightly visible.
x: The display image projected onto the projection image display member had poor clarity and could not be visually recognized.

[Resin Used to Obtain Multilayer Laminated Film]
Resins shown in Table 1 were used to obtain multilayer laminated films of each example and each comparative example. "mol%" is the ratio of the dicarboxylic acid unit and the diol unit to the total amount of 100 mol%.

[Multilayer laminated film]
(Example 1)
As thermoplastic resin A, polyethylene terephthalate (resin 1) having an intrinsic viscosity (IV) of 0.65 was used. Further, as the thermoplastic resin B, a copolymer of polyethylene terephthalate (polyethylene terephthalate obtained by copolymerizing 80 mol% of the terephthalic acid component and 20 mol% of the 2,6-naphthalene dicarboxylic acid component relative to the entire acid component , IV=0.64) (Resin 2). The prepared thermoplastic resin A and thermoplastic resin B were put into two single-screw extruders and melted at a temperature of 290°C. Next, the thermoplastic resin A and the thermoplastic resin B are each passed through five FSS type leaf disk filters, and then weighed with a gear pump so that the weight ratio of the thermoplastic resin A and the thermoplastic resin B becomes 1. A molten resin laminate was obtained in which 201 layers were alternately laminated in the thickness direction so that the thermoplastic resin A was positioned as the outermost layer on both sides. Thereafter, the molten resin laminate was discharged from a die, cooled and solidified in a casting drum at a temperature of 25°C to obtain a cast film. The obtained cast film was heated by a group of rolls set at a temperature of 60°C, and then stretched 3.3 times in the longitudinal direction of the film at a stretching rate of 50%/sec with rolls set at a temperature of 85°C. , and then once cooled. The uniaxially stretched film thus obtained was led to a tenter, preheated with hot air at a temperature of 90°C, and stretched 3.4 times in the film width direction at a temperature of 95°C at a stretching rate of 5%/sec. The stretched film was directly heat-treated in a tenter with hot air at 213° C., then subjected to 3% relaxation treatment (Rx) in the width direction under the same temperature conditions, and then cooled to room temperature. Thus, a multilayer laminated film having a thickness of 25 μm was obtained.

(Examples 2 to 16, Comparative Examples 1 to 4)
A multilayer laminated film was obtained in the same manner as the multilayer laminated film of Example 1 except that the number of layers, the resin of each layer, the draw ratio, and the heat treatment temperature were as shown in Tables 2-1 and 2-2. In addition, the film obtained in Comparative Example 1 was formed by supplying the same resin to two single-screw extruders.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a multi-layer laminate film which has a low haze even after processing laminated glass and which can clearly display an image projected from an oblique direction. Since the multi-layer laminate film of the present invention has the above characteristics, it is suitable for head-up display systems used in transportation equipment such as aircraft, ships, automobiles, railways, buildings, and electronic signboards.

1: DSC1st curve of multilayer laminated film satisfying Tm−T ^* >27 2: DSC1st curve of multilayer laminated film satisfying Tm−T ^* ≦27 3: Temperature differential curve of 1, A (T) = dDSC/dT (mW /°C)
4:2 temperature derivative curve, A(T) = dDSC/dT (mW/°C)
5: DSC1st curve of multilayer laminate film having a maximum value of A(T) at 150<T<Tm of 0.040 or less 6: Multilayer having a maximum value of A(T) at 150<T<Tm exceeding 0.040 Temperature differential curve of DSC1st curve 7:5 of laminated film, A (T) = dDSC/dT (mW/°C)
8:6 temperature derivative curve, A(T)=dDSC/dT (mW/°C)
9: Multilayer laminated film C: A curve obtained by differentiating the DSC1st curve of the multilayer laminated film of one embodiment of the present invention with respect to temperature

Claims (11)

A multilayer laminated film in which 51 or more different thermoplastic resin layers are alternately laminated, and in differential scanning calorimetry (DSC), the temperature (T, ° C.) at which the absolute value of the amount of heat absorbed is maximum is Tm, below. A multi-layer laminated film satisfying Tm−T ^* >27, where T ^* is the temperature (T,° C.) calculated by the method of .
Measurement method of T ^* It is measured by the following (1) and (2).
(1) A temperature differential curve of the DSC1st curve measured at intervals of 1 ° C., A (T) = dDSC / dT (mW / ° C.) graph, the minimum value of A (T) at 150 < T < Tm is Amin, Assuming that T at that time is Tmin, obtain T at the intersection of the curve A(T) and the straight line A(T)=0.2Amin in the range of T<Tmin.
(2) For each T that satisfies (1), let T ^* be the smallest T among T that always satisfies A(T)<0.2Amin in the range from T to T+5°C. 2. The multilayer laminate film according to claim 1, wherein the maximum value of A(T) at 150<T<Tm is 0.040 or less. 3. The multilayer laminated film according to claim 1, wherein the transmittance of visible light incident perpendicularly on the surface of the multilayer laminated film is 50% or more and 100% or less. 2. The relationship of Rp20<Rp60 is satisfied, where Rp20 and Rp60 are the reflectance (%) when p-polarized light rays are incident on the surface of the multilayer film at 20° and 60°, respectively. 3. or the multilayer laminated film according to 2. 3. The multilayer laminate film according to claim 1, wherein the Rp60 is 10% or more and 50% or less. 2. The azimuth angle variation of the reflectance is 10% or less when p-polarized light is incident on the surface of the multi-layer laminated film at an angle of 60° with a normal line thereof. 3. or the multilayer laminated film according to 2. The multilayer laminated film has a structure in which a layer (layer A) made of a first thermoplastic resin and a layer (layer B) made of a second thermoplastic resin are alternately laminated, and the first thermoplastic resin 3. The multi-layer laminate film according to claim 1, wherein the resin contains a crystalline polyester as a main component, and the second thermoplastic resin contains a polyester containing a structure derived from naphthalenedicarboxylic acid or terephthalic acid as a main component. 3. A projection image display member obtained by laminating the multilayer laminated film according to claim 1 or 2 on at least one surface of a transparent member. 3. A projection image display member comprising the multilayer laminated film according to claim 1 or 2 laminated between at least two transparent members. A head-up display system, comprising: an image projector for projecting an image; and the multilayer laminate film according to claim 1 or 2, on which the image from the image projector is projected. 11. The intensity of the p-polarized light component with respect to the plane of incidence when the multi-layer laminate film is used as the reflecting surface, in the light rays forming the image from the image projector, is 51% or more of the intensity of all the light light components. The head-up display system described in .