JP7687003B2 - Laminated Film - Google Patents

Description

The present invention relates to a laminate film suitable for use as an image display member, an image display member, an image display device, and a head-up display.

Head-up displays (HUDs) are known as a means of projecting information directly into the human field of vision. For example, while driving a vehicle such as an automobile, these project information such as the speed of instruments directly onto the windshield as a virtual image. This allows the occupant to drive the vehicle without changing their field of vision, which has the advantage of helping to prevent accidents. In a head-up display, when light emitted from a projector such as a small liquid crystal projector reaches a display unit made of a transparent substrate containing a half-mirror material, part of the light passes through the display unit, and the light that does not pass through is reflected by the display unit. The occupant can then obtain the information displayed on the display unit, while also simultaneously obtaining external information such as the scenery outside through the display unit.

A display device that uses similar technology is the head-mounted display (HMD) used for AR (Augmented Reality). A head-mounted display used for AR is a glass-type display device worn on the head, allowing the user to view information from the outside through the glasses, and also transmits information from a projector installed on the side and displays it on the glasses.

In terms of visibility of projected information and external information, such display devices have shown head-up displays that use a film with polarized reflection properties that reflect only polarized light emitted from a liquid crystal projector (Patent Documents 1 and 2). However, because light from the outside, such as scenery, is often unpolarized, there is an issue that visibility in the front direction decreases when a film with polarized reflection properties is used. As a method of solving the above issue, Patent Documents 3 and 4, for example, show a film that combines transparency in the front direction with the ability to display information projected from an oblique direction, and a HUD and HMD that use the same.

Special Publication No. 2006-512622 JP 2017-206012 A International Publication No. WO 1997/36195 International Publication No. 2019/198635

However, when the films disclosed in Patent Documents 1 to 4 are used in vehicle applications, there is a concern that the reflective performance of the film may deteriorate if the film is exposed to a high-temperature environment for a long period of time, making the film unsuitable for vehicle applications. The present invention aims to solve this problem by providing a laminated film that can maintain reflective performance for a long period of time even in a high-temperature environment.

In order to solve the above problems, the present invention has the following configuration. That is, the laminate film of the present invention is a laminate film in which 50 or more layers of different thermoplastic resins are alternately laminated, and the laminate film is characterized in that it contains aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more.

The present invention provides a laminated film that can maintain high reflective performance even when used in an environment exposed to high temperatures for a long period of time, such as in an in-vehicle application.

The following describes the embodiments of the present invention, but the present invention should not be interpreted as being limited to the embodiments including the following examples, and various modifications are possible within the scope of the invention, as long as the object of the invention can be achieved and the gist of the invention is not deviated from. In addition, for the purpose of simplifying the explanation, some of the explanations will be given using as an example a laminate film having a structure in which two different thermoplastic resin layers are alternately laminated, which is one of the preferred embodiments of the present invention, but the same should be understood when three or more thermoplastic resins are used.

The laminated film of the present invention must be made by alternately laminating 50 or more layers of different thermoplastic resins. Here, "different thermoplastic resins" refers to the presence of multiple thermoplastic resins, at least some of whose constituent components are different from each other. By laminating thermoplastic resins with different constituent components, it is possible to create differences in optical properties such as refractive index when the laminated film is made.

The term "alternately laminated" as used here means that different thermoplastic resins are laminated in a regular arrangement in the thickness direction. For example, if there is a layer (layer A) whose main component is thermoplastic resin A and a layer (layer B) whose main component is thermoplastic resin B, they are laminated in the order of A(BA)n (n is a natural number). If there is a layer (layer C) whose main component is thermoplastic resin C in addition to layers A and B, the arrangement is not particularly limited, but examples include layers laminated in a certain order with a certain regularity, such as C(BA)nC, C(ABC)n, and C(ACBC)n. Note that "a layer whose main component is thermoplastic resin A" refers to a layer that contains 70% by mass or more and 100% by mass or less of thermoplastic resin A among all the components that make up the layer, and hereinafter, "a layer whose main component is thermoplastic resin B" and "a layer whose main component is thermoplastic resin C" can be interpreted in the same way.

In this way, resins with different optical properties such as refractive index are layered alternately, making it possible to produce interference reflection that reflects light of a designed wavelength based on the relationship between the difference in refractive index of each layer and the layer thickness.

If the number of layers is 49 or less, a high reflectance cannot be obtained in the desired band. In addition, the above-mentioned interference reflection can achieve a higher reflectance for light in a wider wavelength band as the number of layers increases, so by increasing the number of layers, a laminated film that reflects light in the desired band can be obtained. From the above perspective, the number of layers in the laminated film is preferably 200 or more, more preferably 400 or more, and particularly preferably 800 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 larger manufacturing equipment, and the handling property deteriorates due to the thicker film. Therefore, in reality, the practical range is about 10,000 layers.

The laminated film of the present invention preferably has a transmittance of 50% or more for light incident perpendicularly to the film surface (meaning an angle of 0° with respect to the normal line of the film surface). Specifically, the transmittance of 50% or more for light incident perpendicularly here means that the average transmittance of the film at wavelengths of 450 to 650 nm is 50% or more. Since the transmittance of light in the visible light region of wavelengths of 450 to 650 nm is high in this way, it can be made to exhibit excellent transmittance for external information such as scenery even when incorporated as a display substrate for HUD or HMD. From the above viewpoint, the transmittance is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. If the transmittance is 85% or more, it has the same transparency as transparent materials such as ordinary glass, glasses, and acrylic plates, and can be used without any burden on the user. There is no particular limit to the upper limit of the transmittance, but it is 99% from the viewpoint of feasibility. The transmittance can be calculated by measuring the transmittance at each wavelength with a spectrophotometer and calculating the average value from the obtained values. (Detailed measurement conditions are shown in the examples.).

To obtain such a laminated film, the refractive index difference between the two thermoplastic resin layers alternately laminated as the final product must be small in the direction parallel to the film surface. For example, if the refractive index difference in the direction parallel to the film surface is 0.06 or less, the transmittance can be easily increased to 50% or more, if it is 0.04 or less, the transmittance can be increased to 70% or more, and if it is 0.02 or less, the transmittance can be increased to 80% or more. The "refractive index difference in the direction parallel to the film surface" refers to the difference in the in-plane refractive index of the thermoplastic resin layers constituting the laminated film (if layers A and B are alternately laminated, the difference in the in-plane refractive index of layers A and B). Each refractive index can be measured using an Abbe refractometer at 25°C, using sodium D line (wavelength 589 nm) as a light source and methylene iodide as a mounting liquid.

The laminated film of the present invention preferably satisfies the relationship R20≦R40<R60, where R20, R40, and R60 are the reflectance (%) of P waves when incident at angles of 20°, 40°, and 60° to the normal to the film surface. The reflectance here refers to the average reflectance at wavelengths of 450 to 650 nm. In the case of a typical transparent substrate such as glass or transparent film, the reflectance of P waves, which is one type of polarized light, decreases as the incident angle is gradually increased from 20° to the normal to the film surface, and the reflectance is 0% at an angle called the Brewster angle. Therefore, when information is projected onto a transparent substrate from an incident angle near the Brewster angle, the display of the information (image) is poor due to the low reflectance. Therefore, if the reflectance of P waves incident at angles of 20°, 40°, and 60° to the normal line of the film surface is R20, R40, and R60, respectively, and the relationship R20≦R40<R60 is satisfied, it is possible to display information more clearly even when information is projected from an oblique direction onto the film surface, since there is no angle equivalent to Brewster's angle. Note that R20, R40, and R60 can be calculated by adjusting the angle of incidence, measuring the reflectance at each wavelength with a spectrophotometer, and averaging the obtained values (detailed measurement conditions are shown in the examples).

In addition, it is also preferable that the laminated film of the present invention has an R60 of 30% or more. If the reflectance of P waves at 60° incidence is 30% or more, it is possible to display information more clearly, especially in a display device that projects information from the side, such as a HUD. From this viewpoint, it is more preferable that the reflectance at 60° incidence is 40% or more, and even more preferable that it is 50% or more. As a method for obtaining such a laminated film, for example, a method of increasing the refractive index difference in the direction perpendicular to the film surface between two thermoplastic resins or a method of increasing the number of layers can be adopted (when layers A and B are alternately laminated, this refers to the difference in the surface perpendicular refractive index between layers A and B). For example, if the number of layers reaches 800, if the refractive index difference is 0.08 or more, it is easy to make the reflectance 30% or more, and if the refractive index difference is 0.12 or more, it is easy to make the reflectance 50% or more.

It is preferable that the laminated film of the present invention has a change in average transmittance of 10% or less at wavelengths of 450 to 650 nm when treated at 100°C for 250 hours. Here, "change in average transmittance of 450 to 650 nm when treated at 100°C for 250 hours" refers to the difference between the average transmittance of each wavelength in the wavelength range of 450 nm to 650 nm when P-polarized light is irradiated at an incident angle of 60° to at least one surface of the laminated film, and the average transmittance of each wavelength in the wavelength range of 450 nm to 650 nm when the same laminated film is left in a 100°C atmosphere for 250 hours and P-polarized light is irradiated at an incident angle of 60° to the same place and same surface of the laminated film.

The fact that the change in average transmittance is 10% or less means that the reflective performance of the laminated film is maintained even in a high-temperature environment. In other words, when the laminated film is used in applications where long-term use in a high-temperature environment is expected, such as the transparent substrate of an in-vehicle HUD or HMD, the change in display performance can be reduced. From the above perspective, the smaller the change in average transmittance, the more preferable it is, and the more preferable the change in average transmittance is 5.0% or less, even more preferably 3.0% or less, and particularly preferably 2.0% or less. By having the change in average transmittance be 2.0% or less, it becomes possible to suitably apply the film to all in-vehicle applications. Note that the smaller the change in average transmittance, the more preferable it is, so there is no lower limit, but from the standpoint of feasibility, it is 0.01%.

A method for making the change in average transmittance at wavelengths of 450 to 650 nm when the laminate film is treated at 100°C for 250 hours 10% or less or within the above-mentioned preferred range includes making the laminate film contain aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units with a number average molecular weight of 200 or more. Preferably, at least one of the thermoplastic resins constituting the laminate film is a polyester resin containing aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units with a number average molecular weight of 200 or more, and a more preferred range can be achieved by selecting the components of the aromatic dicarboxylic acid units or aromatic diol units. This increases the stability of the laminate film in high-temperature environments while maintaining the high display performance of the HUD system, thereby reducing the deterioration of display performance even during long-term use.

It is preferable that the laminated film of the present invention has a color change of 6.0 or less when treated at 100°C for 250 hours. Here, "color change when treated at 100°C for 250 hours" refers to the difference between the average color value of the laminated film and the average color value after the laminated film is left in an atmosphere at 100°C for 250 hours. Note that the color of the laminated film is measured at the same place and on the same surface before and after treatment, and a known colorimeter (for example, a colorimeter (SPECTROPHOTOMETER CM-3600d) manufactured by KONICA MINOLTA, etc.) can be used to measure the color.

By making the amount of change in color 6.0 or less, coloring when the laminated film is used in a high-temperature environment is suppressed. Therefore, by using the laminated film as a transparent substrate for a HUD or HMD, it is possible to obtain a display member that can maintain the color recognition of information from the outside, such as scenery, and information displayed from a projection member for a long period of time. From the above perspective, the smaller the amount of change in color, the more preferable it is, and the more preferable the amount of change in color is 5.0 or less, and even more preferable it is 4.0 or less, and particularly preferable it is 3.0 or less, and most preferable it is 2.0 or less. For example, if the amount of change in color is 5.0 or less, it can be suitably used in a mode in which even if the color recognition of external information is slightly reduced, such as projecting information from instruments on a part of the windshield, the effect on the passenger is small. In addition, by making the amount of change in color 2.0 or less, it can be suitably used for many in-vehicle applications including display on the entire windshield. In addition, since the amount of change in color is as small as possible, there is no lower limit, but from the viewpoint of feasibility, it is 0.01.

As a method for making the color change amount of the laminated film 6.0 or less or within the above-mentioned preferred range when treated at 100°C for 250 hours, for example, a method of making the laminated film contain aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more can be mentioned. Preferably, at least one of the thermoplastic resins constituting the laminated film is a polyester resin containing aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more, and more preferably, the diol units constituting the polyester resin contain paraxylene glycol units. This increases the stability of the laminated film in high temperature environments while maintaining the high display performance of the HUD system, and therefore reduces the deterioration of the display performance of the HUD even during long-term use.

The laminated film of the present invention preferably has an internal haze of less than 2.0% after being treated at 150°C for 2 hours. The fact that the internal haze of the laminated film is less than 2.0% after being treated at 150°C for 2 hours means that the decrease in transparency of the laminated film when used in a long-term high-temperature environment is suppressed, and such a laminated film can be suitably used in applications exposed to high-temperature environments, such as transparent substrates for vehicle-mounted HUDs and HMDs. From the above viewpoint, the lower the internal haze, the better the transparency of the laminated film in a high-temperature environment, and the more preferable internal haze is 1.8% or less, more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. There is no particular limit to the lower limit of this internal haze, but it is 0.01% from the viewpoint of feasibility. The internal haze can be measured by a known haze meter under liquid paraffin.

As a method for making the internal haze less than 2.0% or within the above-mentioned preferred range after treatment at 150°C for 2 hours, there can be mentioned a method similar to the method for making the change in average transmittance at wavelengths of 450 to 650 nm less than 10% or within the above-mentioned preferred range when the resin film is treated at 100°C for 250 hours.

The laminated film of the present invention is required to contain aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more from the viewpoints of amorphization, high refractive index, low glass transition temperature, and heat resistance. Here, the aromatic dicarboxylic acid unit is a structural unit that constitutes the molecular chain of a thermoplastic resin, and contains an aromatic group in the monomer structural unit directly bonded to the carbonyl carbon of the carbonyl group of the two ester bonds. The aromatic diol unit and the alkylene glycol unit having a number average molecular weight of 200 or more can be interpreted in the same way, and each of them contains an aromatic group or an alkylene glycol having a number average molecular weight of 200 or more in the monomer structural unit directly bonded to the oxygen of the two ester bonds. When identifying the structural unit of the thermoplastic resin contained in the laminated film, the ester bond that forms the molecular chain of the thermoplastic resin is hydrolyzed with an alkali or the like, and the ester bond is separated by HPLC, GPC, or the like, and then analyzed by NMR or the like. The number average molecular weight can be calculated from the 1H-NMR spectrum measured by dissolving the laminated film, and the detailed method is shown in the examples.

In addition, when the number average molecular weight of the alkylene glycol is less than 200, the alkylene glycol is not sufficiently incorporated into the polymer due to its high volatility when synthesizing the thermoplastic resin, and as a result, the effect of lowering the glass transition temperature may not be sufficiently obtained. Therefore, the lower limit of the number average molecular weight of the alkylene glycol is preferably 250, more preferably 300, and particularly preferably 350. There is no particular limit to the upper limit of the number average molecular weight of the alkylene glycol, but if it is greater than 2000, the reactivity may decrease during the production of the thermoplastic resin and the film may not be suitable for production. Therefore, from the viewpoint of productivity, it is more preferable that it is 1500 or less, even more preferably 1000 or less, and particularly preferably 600 or less. Examples of alkylene glycol include polyethylene glycol, polytrimethylene glycol, and polytetramethylene glycol.

In addition, when the laminate film "contains aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more," this means that the thermoplastic resin constituting the laminate film contains all of these structural units. In other words, it may be either an embodiment in which one thermoplastic resin contains all of these structural units, or an embodiment in which all of these structural units are contained in the laminate film as a whole even if each individual thermoplastic resin does not contain all of these structural units. Note that, as a specific example of the latter embodiment, for example, a laminate film is composed of two types of thermoplastic resins, one of which contains aromatic dicarboxylic acid units and aromatic diol units, and the other thermoplastic resin contains alkylene glycol units having a number average molecular weight of 200 or more.

From the above viewpoint, it is more preferable that at least one of the thermoplastic resins of the laminated film of the present invention contains a polyester resin containing aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more. By containing aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more, it is possible to achieve amorphization, a high refractive index, and a low glass transition temperature, and also to obtain an improved heat resistance effect during long-term high-temperature use, resulting in a laminated film suitable for in-vehicle applications. In this embodiment, the preferred range of the number average molecular weight of the alkylene glycol is as described above. Examples of alkylene glycols include polyethylene glycol, polytrimethylene glycol, and polytetramethylene glycol.

In addition, in the laminated film of the present invention, it is preferable that the aromatic diol unit contains a paraxylene glycol unit. By adopting such an embodiment, the bulkiness derived from paraxylene glycol and the small size of the unit can provide an amorphization promotion effect, and the laminated film has high transparency and display performance while improving its stability in a high-temperature environment. Therefore, even when used for a long period of time as a transparent substrate for HUD or HMD for in-vehicle applications, the deterioration of display performance can be reduced. In addition, from the above viewpoint, the content of the paraxylene glycol unit is preferably 25 mol% or more, and more preferably 30 mol% or more, when the total diol units contained in the laminated film are 100 mol%. In addition, from the viewpoint of lowering the glass transition temperature, the upper limit polymerization amount of the paraxylene glycol unit is 40 mol% when the total diol units contained in the laminated film are 100 mol%. By having the paraxylene glycol unit be 25 mol% or more, it becomes easy to suppress the internal haze after 2 hours of treatment at 150 ° C. to less than 1.0%, and whitening of the laminated film due to heating is suppressed, so that it can be suitably used for in-vehicle applications.

As long as it contains all of the above-mentioned structural units, the laminated film of the present invention may contain a variety of thermoplastic resins without any particular limitations. Examples of the thermoplastic resins used in the present invention include linear polyolefins such as polyethylene, polypropylene, poly(4-methylpentene-1), and polyacetal, alicyclic polyolefins which are ring-opening metathesis polymers of norbornenes, addition polymers, and addition copolymers with other olefins, biodegradable polymers such as polylactic acid and polybutyl succinate, polyamides such as nylon 6, nylon 11, nylon 12, and nylon 66, aramid, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl acetate copolymer, polyacetal, Polyglycolic acid, polystyrene, styrene copolymerized polymethylmethacrylate, polycarbonate, polyesters such as polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride can be used. Among these, polyesters are particularly preferred from the viewpoints of strength, heat resistance, transparency, and versatility. These may be copolymers or mixtures of two or more resins.

The polyester is preferably a polyester obtained by polymerization of a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. Examples of 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, and 4,4'-diphenylsulfonedicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof. Among these, terephthalic acid and 2,6-naphthalenedicarboxylic acid, which exhibit a high refractive index, are preferred. These acid components may be used alone or in combination of two or more, and may also be partially copolymerized with oxyacids such as hydroxybenzoic acid.

Examples of diol components include ethylene 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, and paraxylene glycol. Among these, ethylene glycol is preferably used from the viewpoints of availability, cost, and film-forming properties. These diol components may be used alone or in combination of two or more.

Of the above polyesters, it is preferable to use, for the thermoplastic resin of the present invention, polyethylene terephthalate and its copolymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, polyhexamethylene terephthalate and its copolymers, polyhexamethylene naphthalate and its copolymers, etc.

In particular, in the laminated film of the present invention, it is preferable that the resin constituting one layer (layer A) of the alternately laminated layers contains a crystalline thermoplastic resin, and the resin constituting the other layer (layer B) contains an amorphous thermoplastic resin. The amorphous resin referred to here is a thermoplastic resin having a crystal fusion heat ΔHm of 5 J/g or less calculated from the peak area of the melting peak in a differential scanning calorimetry chart obtained by heating 5 g of resin from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1st RUN) in accordance with JIS K7122 (1987), holding the resin in that state for 5 minutes, rapidly cooling the resin to a temperature of 25 ° C. or less, and then heating the resin from room temperature to a temperature of 300 ° C. at a heating rate of 20 ° C./min again in the 2nd RUN, and more preferably a thermoplastic resin that does not show a peak corresponding to crystal fusion. The rapid cooling can be performed by spraying liquid nitrogen on the resin while it is still in the furnace. On the other hand, a crystalline resin is a thermoplastic resin that does not meet the above requirements in the differential scanning calorimetry chart. For example, if one type of crystalline thermoplastic resin is used in layer A of the thermoplastic resin and one type of amorphous thermoplastic resin is used in layer B, even when it is made into a laminated film, it will only show one melting point.

The laminated film of the present invention preferably contains a polycyclic aromatic compound as a copolymerization component as an amorphous thermoplastic resin. By containing a polycyclic aromatic compound such as naphthalene or anthracene, it becomes easier to increase the refractive index. More preferably, the copolymer contains three or more types of dicarboxylic acid units and diol units in total. In the case of a thermoplastic resin consisting of one type of dicarboxylic acid unit and one type of diol unit, orientation and crystallization are promoted during stretching due to its high symmetry, and the amorphous state may not be maintained. However, by containing a copolymer containing three or more types of dicarboxylic acid units and diol units, orientation and crystallization are suppressed during stretching, making it easier to maintain the amorphous state.

In addition, the laminate film of the present invention preferably contains an alkylene glycol unit having a number average molecular weight of 200 or more in any of the layers constituting the laminate film. As described above, in order to increase the refractive index, it is necessary to contain a large amount of aromatic-derived cyclic structures, but by further containing a structure derived from alkylene glycol, it becomes easy to efficiently lower the glass transition temperature while maintaining the refractive index. As a result, a laminate film in which the in-plane refractive index of each layer constituting the laminate film is 1.61 or more and the glass transition temperature is 90 ° C. or less can be easily obtained. Particularly preferably, the thermoplastic resin constituting layer B is amorphous and contains a structure derived from alkylene glycol having a number average molecular weight of 200 or more, and more preferably, layer B consisting of an amorphous thermoplastic resin is composed only of an amorphous thermoplastic resin containing a structure derived from alkylene glycol having a number average molecular weight of 200 or more. By mixing a small amount of a thermoplastic resin containing a structure derived from alkylene glycol having a number average molecular weight of 200 or more with another amorphous resin, it is possible to efficiently lower the glass transition temperature while maintaining the refractive index of the amorphous resin. Furthermore, by making the thermoplastic resin itself a copolymer containing a structure derived from alkylene glycol with a number average molecular weight of 200 or more, it is possible to suppress the precipitation of the thermoplastic resin containing a structure derived from alkylene glycol on the surface of the laminated film even when processing is performed under high temperature conditions.

The laminated film of the present invention preferably contains paraxylene glycol in the aromatic diol units of the amorphous polyester resin. The bulkiness and small size of the units derived from paraxylene glycol provide an amorphous promoting effect, which provides high transparency and display performance for the transparent substrate for HUDs and HMDs used in vehicles, while increasing the stability of the laminated film in high temperature environments, thereby reducing deterioration in display performance even during long-term use.

The laminated film of the present invention preferably contains 10 mol% or more of paraxylene glycol units in the total diol units of the amorphous polyester resin. This improves the stability of the laminated film in a high-temperature environment. Furthermore, when the film contains 25 mol% or more of paraxylene glycol units, the resin film is stable in a high-temperature environment while maintaining the high transparency and display performance of the transparent substrate when used in an in-vehicle HUD or HMD, so that the deterioration of display performance can be reduced even during long-term use. In order to satisfy higher transparency and display performance with an increase in the content of paraxylene glycol units, the more preferable content of paraxylene glycol units is 30 mol% or more. On the other hand, from the viewpoint of lowering the glass transition temperature, the upper limit polymerization amount of paraxylene glycol units is 40 mol%. By containing 25 mol% or more of paraxylene glycol units, it becomes easy to suppress the internal haze after 2 hours of treatment at 150 ° C. to less than 1.0%, and whitening of the laminated film due to heating is suppressed, so that the film can be suitably used for in-vehicle applications. Furthermore, when the paraxylene glycol unit is 30 mol % or more, the laminated film does not whiten even under severe high-temperature conditions of 150°C, making it suitable for applications with stricter standards such as windshields.

In addition, various additives, such as antioxidants, heat stabilizers, weather stabilizers, UV absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and nucleating agents, can be added to the thermoplastic resin either alone or in combination to the extent that the properties of the resin are not adversely affected.

Next, the image display member of the present invention will be described. The image display member of the present invention comprises the laminate film of the present invention. Specific examples include an image display member in which the laminate film of the present invention is laminated on at least one surface of a transparent member, and an image display member in which the laminate film of the present invention is laminated between two transparent members. Examples of the transparent member include glass and resin, and examples of the resin include polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, polymethylpentene and copolymers thereof, and acrylonitrile-butadiene-styrene copolymers.

When laminating the transparent member and the laminated film of the present invention, it is also preferable to provide an adhesive layer between them. Examples of adhesives constituting the adhesive layer include vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, chloroprene rubbers, polyamides, epoxy resins, polyurethanes, acrylic resins, cellulose, polyvinyl chloride, polyacrylic esters, polyisobutylene, and the like. In addition, these adhesives may contain adhesion regulators, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, and the like. The form of these adhesive layers before processing may be liquid, gel, block, powder, film, and the like. Methods for solidifying the adhesive layer include solvent evaporation, moisture curing, heat curing, hardener mixing, anaerobic curing, UV curing, heat melting and cooling, and pressure sensitivity. The lamination method can be a known method such as lamination molding or injection molding, and the image display member is produced by applying heat, pressure, and using the above-mentioned adhesive layer solidification method.

Furthermore, the surface of the image display member may have various functional layers such as a hard coat layer, an abrasion-resistant layer, an anti-scratch layer, an anti-reflection layer, a color correction layer, an ultraviolet absorbing layer, a light stabilizing layer (HALS), a heat absorbing layer, a print layer, a gas barrier layer, an adhesive layer, a transparent electrode layer, etc. An example of an image display member in which the laminated film of the present invention is laminated between two transparent members is the windshield of a vehicle such as an automobile. As the configuration, for example, a configuration of glass/polyvinyl butyral/laminate film of the present invention/polyvinyl butyral/glass or a configuration of glass/polyvinyl butyral/laminate film of the present invention/glass can be adopted, and the thickness of the glass is preferably in the range of 2 mm to 3 mm, and the thickness of the polyvinyl butyral is preferably 100 μm to 1000 μm.

The image display member of the present invention preferably has a reflectance (Rs60) of 30% or less for S-waves incident at an incident angle of 60°. When the image display member of the present invention is used as a HUD, it is required that the displayability of information is high and that the visibility of external information such as the outside scenery seen through the display unit is also high. Therefore, by making Rs60 30% or less, the visibility of external information such as the outside scenery can be improved. Methods for making Rs60 30% or less include forming AR (anti-reflection), AG (anti-glare), or a moth-eye structure having multiple conical convex portions smaller than the wavelength of visible light on the surface of the image display member. In addition, since the inclination angle of the windshield of an automobile is often around 60°, it is particularly preferable that Rs60 is 30% or less when the image display member of the present invention is used for the windshield of an automobile.

Next, the image display device of the present invention will be described. The image display device of the present invention comprises an image display member of the present invention and a light source that irradiates light at an angle of 20° or more with respect to the normal line of the display surface of the image display member of the present invention. The incident angle of light with respect to the normal line is preferably 40° or more and 75° or less. Such an image display device is capable of displaying information on the image display member clearly and with high reproducibility while maintaining transparency in the front direction. The light source is not particularly limited as long as it does not impair the effects of the present invention, and examples of the light source include a liquid crystal projector, an RGB laser, DLP (Digital Light Processing), and LCOS (Liquid crystal on silicon). The light (information) emitted from the light source may be directly projected onto the image display member, or may be projected onto the image display member after reflection by a mirror, collection through a lens, diffusion, or passing through a polarizing reflection member. As this mirror, a cold mirror that reflects only visible light is preferable. With a normal mirror that reflects everything from visible light to infrared light, when sunlight that has entered the image display device is reflected by the mirror and irradiated onto the light source, the infrared rays cause a temperature rise, but a cold mirror does not reflect infrared light, so it can suppress the temperature rise of the light source. The polarized reflective member reflects light in one direction on its surface (reflection axis orientation) and transmits light in a direction perpendicular to that direction (transmission axis orientation), so it can roughly halve the amount of light that enters from the outside, such as sunlight, and causes a temperature rise inside the projection image display device. On the other hand, by adjusting the polarization of the light from the light source to match the transmission axis orientation of the polarized reflective member, it is also possible to suppress the attenuation of the brightness of the light projected from the light source.

The image display device of the present invention can be used as a head-up display (HUD) or head-mounted display (HMD) for use in automobiles, aircraft, electronic signage, game machines, etc. When used in automobiles, information is projected from a small projection device toward a prompter made of a transparent substrate provided on the windshield or near the windshield of the automobile. By using the laminated film of the present application for the windshield or prompter, it is possible to display information clearly and with high reproducibility while maintaining transparency in the front direction. In this case, the laminated film may be attached to the windshield via an adhesive, or may be inserted inside the laminated glass used for the windshield. The prompter may also be attached to a transparent substrate.

In the image display device of the present invention, the azimuth angle of the main orientation axis of the laminated film is preferably within ±30° with respect to the floor surface. Here, the azimuth angle in the horizontal direction with respect to the floor surface is 0°. Generally, light in the natural world is polarized by reflection from buildings, the ground, etc., and is mainly S-polarized light. When external information such as an outside scene passes through the image display device of the present invention, the azimuth angle of the S-polarized light is horizontal with respect to the floor surface. The laminated film of the present invention is produced by stretching in at least two directions, so it has optical properties such as biaxiality and main orientation axis. When polarized light passes through the laminated film at an azimuth angle with respect to the main orientation axis of this laminated film that is greater than 0, the polarization state of the transmitted light changes. In other words, if the transmitted polarized light is information such as an outside scene, the change in polarization state may cause rainbow-patterned unevenness that is not present in the original scene to be visible. This rainbow-patterned unevenness reaches its maximum intensity when the azimuth angle of the polarized light that passes through the laminated film is 45° with respect to the main orientation axis of the laminated film. Therefore, the rainbow-patterned unevenness can be reduced by reducing this azimuth angle. Preferably, the azimuth angle of the main orientation axis of the laminate film is within ±15° with respect to the floor surface, and more preferably within ±10°. In this way, the projection image display device of the present invention can improve the visibility of external information such as the outside scenery by setting the azimuth angle of the main orientation axis of the laminate film within ±30° with respect to the floor surface. In particular, suppression of this rainbow pattern unevenness is important when the image display device of the present invention is applied to the windshield of an automobile.

Next, the head-up display and head-mounted display of the present invention will be described. The head-up display and head-mounted display of the present invention are equipped with the image display device of the present invention. The image display device of the present invention has excellent visibility of information from the outside, such as scenery, displayability of information from the projection member, color reproducibility, and distortion reduction, due to the laminate film of the present invention.

Specific examples of the laminated film of the present invention are described below, but the laminated film of the present invention is not limited to these examples. When the laminated film of the present invention has the above-mentioned laminated film configuration, a laminated structure of 50 or more layers can be produced by the following method. Thermoplastic resin is supplied from two extruders, extruder A corresponding to layer A and extruder B corresponding to layer B, and polymers from each flow path are laminated into 50 or more layers by using a multi-manifold type feed block and a square mixer, which are known lamination devices, or by using only a comb type feed block, and then the molten laminate is melt-extruded into a sheet shape using a T-shaped die or the like, and then cooled and solidified on a casting drum to obtain an unstretched laminated film. As a method for improving the lamination accuracy of layers A and B, the methods described in JP-A-2007-307893, JP-A-4691910, and JP-A-4816419 are preferred. If necessary, it is also preferable to dry the thermoplastic resin used in layer A and the thermoplastic resin used in layer B.

Then, the unstretched laminated film is stretched and heat-treated. As the stretching method, the known sequential biaxial stretching method or the simultaneous biaxial stretching method is preferable. The stretching temperature is preferably in the range of the glass transition temperature of the unstretched laminated film or higher to the glass transition temperature + 80°C or lower. The stretching ratio is preferably in the range of 2 to 8 times in the longitudinal direction and the width direction, and more preferably in the range of 3 to 6 times, and it is preferable to reduce the difference in the stretching ratio between the longitudinal direction and the width direction. The longitudinal stretching is preferably performed by utilizing the speed change between the rolls of the longitudinal stretching machine. In addition, the known tenter method is used for the width direction stretching. That is, the film is conveyed while both ends are held by clips, and the film is stretched in the width direction by widening the clip distance at both ends.

It is also preferable to perform simultaneous biaxial stretching in the tenter. The case of performing simultaneous biaxial stretching will be described. An unstretched laminated film cast on a cooling roll is introduced into a simultaneous biaxial tenter, and the film is conveyed while both ends are held by clips, and stretched simultaneously and/or stepwise in the longitudinal and width directions. Stretching in the longitudinal direction is achieved by widening the distance between the clips of the tenter, and stretching in the width direction is achieved by widening the gap between the rails on which the clips run. The tenter clips that perform the stretching and heat treatment in the present invention are preferably driven by a linear motor system. Other methods include a pantograph system and a screw system, but the linear motor system is superior in that the stretching ratio can be freely changed due to the high degree of freedom of each clip.

It is also preferable to perform heat treatment after stretching. The heat treatment temperature is preferably in the range of from the stretching temperature to the melting point of the thermoplastic resin of layer A minus 10°C, and it is also preferable to perform a cooling process after the heat treatment at a temperature in the range of the heat treatment temperature minus 30°C. In order to reduce the thermal shrinkage rate of the film, it is also preferable to shrink (relax) the film in the width direction and/or length direction during the heat treatment process or cooling process. The relaxation rate is preferably in the range of 1% to 10%, and more preferably in the range of 1 to 5%. Finally, the film is wound up on a winder to produce the laminated film of the present invention.

The laminated film of the present invention thus obtained can maintain its reflective performance for a long period of time even in a high-temperature environment, and can be suitably used as an image display member.

The laminated film of the present invention will be described below using examples.

(Methods for measuring physical properties and evaluating effects)
The methods for evaluating the physical properties and the effects are as follows.

(1) Number of layers The layer structure of the laminate film was confirmed by observing a cross-section of a sample cut out by a cryo-ultrathin sectioning method using a microtome with a transmission electron microscope (TEM) to confirm the number of layers in the multi-layer laminate film. More specifically, a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.) was used to take a cross-sectional photograph of the film under conditions of an acceleration voltage of 75 kV and an observation magnification of 20,000 times, and the number of layers was confirmed.

(2) Average transmittance A Hitachi spectrophotometer (U-4100 Spectrophotometer) was fitted with an angle variable unit and a Grant Taylor polarizer, and the transmittance was measured in 1 nm increments in the wavelength range of 400 to 1600 nm when P-polarized or S-polarized light was incident at an incident angle of 0° on the laminated film surface as the measurement specimen, and the average transmittance was determined for wavelengths of 450 nm to 650 nm. The measurement conditions were a slit of 2 nm (visible), automatic control (infrared), a gain of 2, and a scanning speed of 600 nm/min.

(3) Average reflectance A Hitachi spectrophotometer (U-4100 Spectrophotometer) was fitted with an angle variable unit and a Grant Taylor polarizer, and the transmittance was measured in 1 nm increments in the wavelength range of 400 to 1600 nm when P-polarized or S-polarized light was incident on the laminate film surface as the measurement specimen at angles of incidence of 0°, 20°, 40°, and 60°, and the average reflectance was determined for wavelengths of 450 nm to 650 nm. The measurement conditions were a slit of 2 nm (visible), automatic control (infrared), a gain of 2, and a scanning speed of 600 nm/min.

(4) Amount of change in average transmittance at wavelengths of 450 to 650 nm The laminated film was left in an atmosphere at 25° C. for 250 hours, and the average transmittance at wavelengths of 450 to 650 nm was determined in the same manner as in evaluation method (2), except that P-polarized light was made incident at an incident angle of 70° on the same film surface and the same measurement location as in the measurement after leaving the laminated film in an atmosphere at 100° C. for 250 hours, and the average transmittance at wavelengths of 450 to 650 nm was determined in the same manner as in evaluation method (2). The difference between these values was calculated, and this was taken as the amount of change in the average transmittance at wavelengths of 450 to 650 nm.

(5) Amount of change in color The color of the laminated film that had been left in an atmosphere at 25° C. for 250 hours was measured using a colorimeter (SPECTROPHOTOMETER CM-3600d) manufactured by KONICA MINOLTA. Next, the laminated film was left in an atmosphere at 100° C. for 250 hours, and the color was similarly measured at the same film surface and the same measurement location as in the measurement after the film had been left in an atmosphere at 25° C. for 250 hours. The difference between these values was calculated and used as the amount of change in color.

(6) Internal haze after treatment at 150° C. for 2 hours The laminated film was left in an atmosphere of 150° C. for 2 hours, then placed in a quartz cell for liquid measurement, filled with liquid paraffin, and measured using a haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd. The internal haze excluding the film surface haze was measured. The same measurement was repeated three times at randomly different measurement positions, and the average of the obtained values was taken as the internal haze value of the laminated film.

(7) Number average molecular weight of alkylene glycol The film was dissolved in HFIP-d2 (hexafluoro-2-propanol dideuterated) and 1H-NMR was measured. For the spectrum obtained, the area of a signal having a peak at a chemical shift of 3.8 ppm was defined as S1, and the area of a signal having a peak at a chemical shift of 3.9 ppm was defined as S2. S1/S2×44 (44: formula weight of the repeating unit of ethylene glycol) was calculated, and the obtained value was regarded as the number average molecular weight of alkylene glycol.

(8) Refractive Index Using sodium D line (wavelength 589 nm) as a light source and methylene iodide as a mounting liquid, the refractive indexes in the longitudinal, width and thickness directions of the film were determined using an Abbe refractometer at 25° C. Here, the average value of the refractive indexes in the longitudinal and width directions of the film was taken as the refractive index in the direction parallel to the film surface (in-plane refractive index), and the refractive index in the film thickness direction was taken as the refractive index in the direction perpendicular to the film surface (perpendicular refractive index).

(Resin used in the film)
The following resins were used in the production of the films of each of the Examples and Comparative Examples, where Resin 1 is a crystalline resin and Resins 2 to 8 are amorphous resins.

Resin 1: Polyethylene terephthalate with an IV of 0.65. The in-plane refractive index of the film described in Comparative Example 2 is 1.65, and the perpendicular refractive index is 1.49.

Resin 2: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.62, and perpendicular refractive index = 1.62 (polyethylene naphthalate copolymerized with 80 mol% of 2,6-naphthalenedicarboxylic acid component relative to the total acid components, 20 mol% of isophthalic acid component relative to the total acid components, 96 mol% of ethylene glycol relative to the total diol components, and 4 mol% of polyethylene glycol with a number average molecular weight of 400 relative to the total diol components).

Resin 3: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.64, and perpendicular refractive index = 1.64 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the total acid component, 66 mol% ethylene glycol relative to the total diol component, 30 mol% paraxylene glycol relative to the total diol component, and 4 mol% polyethylene glycol with a number average molecular weight of 400 relative to the total diol component).

Resin 4: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.63, and perpendicular refractive index = 1.63 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the entire acid component, 71 mol% ethylene glycol relative to the entire diol component, 25 mol% paraxylene glycol relative to the entire diol component, and 4 mol% polyethylene glycol with a number average molecular weight of 400 relative to the entire diol component).

Resin 5: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.63, and perpendicular refractive index = 1.63 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the entire acid component, 76 mol% ethylene glycol relative to the entire diol component, 20 mol% paraxylene glycol relative to the entire diol component, and 4 mol% polyethylene glycol with a number average molecular weight of 400 relative to the entire diol component).

Resin 6: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.63, and perpendicular refractive index = 1.63 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the total acid component, 86 mol% ethylene glycol relative to the total diol component, 10 mol% paraxylene glycol relative to the total diol component, and 4 mol% polyethylene glycol with a number average molecular weight of 400 relative to the total diol component).

Resin 7: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.63, and perpendicular refractive index = 1.63 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the total acid component, 83 mol% ethylene glycol relative to the total diol component, 10 mol% BPEF relative to the total diol component, and 7 mol% polyethylene glycol with a number average molecular weight of 400 relative to the total diol component).

Resin 8: Polyethylene naphthalate copolymer with IV = 0.65, in-plane refractive index = 1.63, and perpendicular refractive index = 1.63 (polyethylene naphthalate copolymerized with 100 mol% 2,6-naphthalenedicarboxylic acid component relative to the total acid component, 89 mol% ethylene glycol relative to the total diol component, 5 mol% BPEF relative to the total diol component, and 6 mol% polyethylene glycol with a number average molecular weight of 400 relative to the total diol component).

Example 1
Resin 1 was used as the thermoplastic resin constituting layer A, and resin 3 was used as the thermoplastic resin constituting layer B. Resin 1 and resin 3 were each melted at 280°C in an extruder and passed through five FSS-type leaf disk filters, and then the resins were alternately merged in an 801-layer feed block (layer A was 401 layers, layer B was 400 layers) designed so that the reflected wavelength of P waves at an incident angle of 70° is in the range of 400 nm to 1000 nm, while being metered with a gear pump so that the discharge ratio (lamination ratio) is resin 1/resin 3 = 1.5. Next, the laminate of the molten thermoplastic resin molded into a sheet shape was extruded from a T-die, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25°C while applying an electrostatic voltage of 8 kV with a wire, to obtain an unstretched laminate film. The unstretched laminated film was longitudinally stretched at a temperature of 93°C and a stretch ratio of 3.2 times to obtain a uniaxially oriented laminated film, and both sides of the film were subjected to corona discharge treatment in air, and then a laminated film coating liquid consisting of (polyester resin with a glass transition temperature of 18°C)/(polyester resin with a glass transition temperature of 82°C)/silica particles with an average particle size of 100 nm was applied to both sides of the film. Then, the uniaxially oriented laminated film was held at both ends in the width direction with clips and introduced into a tenter, and was transversely stretched 3.9 times at 90°C, and then heat-treated at 216°C and relaxed in the width direction by 1.1%. Finally, the film was cooled at 100°C to obtain a laminated film with a thickness of 80 μm (thickness of both surface layers: 5 μm). The evaluation results are shown in Table 1.

(Examples 2 to 6, Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1, except that the thermoplastic resins constituting each layer were those shown in Table 1. The evaluation results are shown in Table 1.

(Example 7)
A laminated film was obtained in the same manner as in Example 1, except that resin 1 was used as the thermoplastic resin constituting layer A, resin 3 was used as the thermoplastic resin constituting layer B, and a 401-layer feedblock (201 layers of layer A and 200 layers of layer B) designed so that the reflected wavelength of P waves at an incident angle of 70° was in the range of 400 nm to 800 nm was used. The evaluation results are shown in Table 1.

(Example 8)
A laminated film was obtained in the same manner as in Example 1, except that resin 1 was used as the thermoplastic resin constituting layer A, resin 3 was used as the thermoplastic resin constituting layer B, and a 201-layer feedblock (101 layers of layer A and 100 layers of layer B) designed so that the reflected wavelength of P waves at an incident angle of 70° was in the range of 400 nm to 800 nm was used. The evaluation results are shown in Table 1.

(Comparative Example 2)
A film was obtained in the same manner as in Example 1, except that a lamination device was not used and a single-layer film made of Resin 1 was used. The evaluation results are shown in Table 1. While the film had high transparency and excellent visibility in the front direction, it did not show reflectivity in oblique directions because it was a single layer, and the projected information could not be confirmed.

(Comparative Example 3)
The resin was fed to a T-die and molded into a sheet to obtain a non-oriented film in the same manner as in Comparative Example 2, except that Resin 3 was used. The evaluation results are shown in Table 1.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 1, except that a three-layer feed block (thermoplastic resin A/thermoplastic resin B/thermoplastic resin A) was used. The evaluation results are shown in Table 1.

The present invention relates to a laminate film for a projection image display member, which has excellent transparency in the front direction, thereby enabling high visibility of information from the outside, such as scenery, and excellent reflectivity in oblique directions, thereby enabling high displayability and color reproducibility of information from a projection member, and which suppresses distortion. A projection image display device using the laminate film of the present invention can be suitably used for head-up displays (HUDs) and head-mounted displays (HMDs) used in vehicles such as automobiles, aircraft, electronic signboards, game machines, etc.

Claims (9)

A laminated film comprising 50 or more layers of two different thermoplastic resin layers (Layer A and Layer B) alternately laminated together, the laminated film containing aromatic dicarboxylic acid units, aromatic diol units, and alkylene glycol units having a number average molecular weight of 200 or more, the aromatic diol units containing paraxylene glycol units or BPEF,
the thermoplastic resin constituting the layer A is polyethylene terephthalate containing an aromatic dicarboxylic acid unit,
1. A laminate film, wherein the thermoplastic resin constituting the layer B is a polyester resin containing aromatic dicarboxylic acid units and alkylene glycol units having a number average molecular weight of 200 or more, and containing paraxylene glycol or BPEF as aromatic diol units . 2. The laminated film according to claim 1 , which has a change in average transmittance at wavelengths of 450 to 650 nm of 10% or less when treated at 100° C. for 250 hours. 3. The laminated film according to claim 1 , which has a change in color of 6.0 or less when treated at 100° C. for 250 hours. 4. The laminated film according to claim 1 , which has an internal haze of less than 2.0% after treatment at 150° C. for 2 hours . 5. The laminated film according to claim 1 , wherein the polyester resin contains paraxylene glycol units in an amount of 25 mol % or more in all diol units constituting the polyester resin. The laminated film according to any one of claims 1 to 5, wherein the transmittance of light perpendicularly incident on the film surface is 50% or more, and when R20, R40, and R60 are the reflectances (%) of P waves incident at angles of 20°, 40°, and 60° to the normal line of the film surface, respectively, the relationship R20≦R40< R60 is satisfied, and R60 is 30% or more. An image display member comprising the laminate film according to any one of claims 1 to 6 . 8. An image display device comprising: the image display member according to claim 7 ; and a light source that irradiates light at an angle of 20 degrees or more with respect to a normal to a display surface of the image display member. A head-up display comprising the image display device according to claim 8 .