Multilayer film

Abstract

To provide a laminate film that can maintain reflection performance for the long term even under high-temperature environment.SOLUTION: A laminate film is made of alternative stacks of multiple thermoplastic resins of more than or equal to 50 layers, and the laminate film contains an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit the number average molecular weight of which is more than or equal to 200.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a laminated film, an image display member, an image display device, and a head-up display that can be suitably used for an image display member.

Background Art

[0002] As a means for directly projecting information onto the human visual field, a head-up display (HUD) is known. For example, during the operation of a vehicle such as an automobile, information such as the speed of instruments in the vehicle is directly projected as a virtual image onto the front glass or the like. Therefore, the passenger can drive the vehicle without changing the visual field, which has the feature of contributing to accident prevention. In a head-up display, usually, when light emitted from a projector such as a small liquid crystal projector reaches a display unit made of a transparent substrate including a half mirror material, a part of the light passes through the display unit, and the light that has not passed through is reflected by the display unit. Then, the passenger can acquire the information displayed on the display unit and simultaneously acquire external information such as the scenery outside through the display unit.

[0003] As a display device using a similar technique, there is a head-mounted display (HMD) used for AR (Augmented Reality). The head-mounted display used for AR applications is a glass-type display device that is worn on the head to visually recognize information from the outside through the glass, transmit information from a projector provided on the side, and display it on the glass.

[0004] In such a display device, from the viewpoint of the visibility of projection information and external information, for example, a head-up display using a film having a polarization reflection characteristic that reflects only polarized light irradiated from a liquid crystal projector is shown (Patent Documents 1 and 2). However, since light from the outside such as scenery is often unpolarized, when a film having a polarization reflection characteristic is used, there is a problem that the visibility in the front direction is reduced. Further, as a method for solving the above problem, for example, Patent Documents 3 and 4 disclose a film that achieves both the transparency in the front direction and the displayability of information projected from an oblique direction, and a HUD and an HMD using the same.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when the films disclosed in Patent Documents 1 to 4 are used in in-vehicle applications, there is a concern that the reflection performance of the film deteriorates due to the film being exposed to a high-temperature environment for a long period of time, and there is a problem that it is not suitable for use in in-vehicle applications. An object of the present invention is to solve this problem and provide a laminated film capable of maintaining the reflection performance over a long period even in a high-temperature environment.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention has the following configuration. That is, the laminated film of the present invention is a laminated film in which a plurality of different thermoplastic resins are alternately laminated in 50 or more layers, and the laminated film is characterized by containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a laminated film capable of maintaining high reflection performance even when used in an environment exposed to high temperatures for a long time, such as in in-vehicle applications.

Modes for Carrying Out the Invention

[0009] The embodiments of the present invention will be described below. However, the present invention is not construed as being limited to the embodiments including the following examples, and various changes can naturally occur within the scope that can achieve the object of the invention and does not deviate from the gist of the invention. Also, for the purpose of simplifying the explanation, some explanations will be given by taking as an example a laminated 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. However, the same should be understood even when three or more thermoplastic resins are used.

[0010] The laminated film of the present invention needs to be formed by alternately laminating 50 or more layers of a plurality of different thermoplastic resins. The "plurality of different thermoplastic resins" referred to here means that there are a plurality of thermoplastic resins and at least a part of their constituent components are different from each other. By laminating thermoplastic resins with different constituent components, differences can be caused in optical properties such as refractive index when a laminated film is formed.

[0011] As used herein, the term "alternately laminated" means that different thermoplastic resins are laminated in a regular arrangement in the thickness direction. For example, when there are a layer (layer A) mainly composed of thermoplastic resin A and a layer (layer B) mainly composed of thermoplastic resin B, they are laminated in the order of A(BA)n (n is a natural number). When there is also a layer (layer C) mainly composed of thermoplastic resin C in addition to layer A and layer B, the arrangement is not particularly limited, but an example is one laminated in a certain regularity such as C(BA)nC, C(ABC)n, or C(ACBC)n. Note that the "layer mainly composed of thermoplastic resin A" refers to a layer containing 70% by mass or more and 100% by mass or less of thermoplastic resin A among all the components constituting the layer. Hereinafter, the "layer mainly composed of thermoplastic resin B" and the "layer mainly composed of thermoplastic resin C" can be interpreted in the same way.

[0012] By alternately laminating resins having different optical properties such as refractive index in this way, it becomes possible to exhibit 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.

[0013] When the number of laminated layers is 49 layers or less, a high reflectance cannot be obtained in the desired band. Also, since the above-described interference reflection can achieve a high reflectance for light in a wider wavelength band as the number of layers increases, a laminated film that reflects light in the desired band can be obtained by increasing the number of layers. From the above viewpoints, the number of layers of the laminated film is preferably 200 layers or more, more preferably 400 layers or more, and particularly preferably 800 layers or more. Also, 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 the size of the manufacturing apparatus, and the handleability deteriorates due to the increase in the film thickness. Therefore, in reality, about 10,000 layers is the practical range.

[0014] The laminated film of the present invention preferably has a light transmittance of 50% or more for light incident perpendicularly to the film surface (meaning an angle of 0° with respect to the normal of the film surface). Specifically, the light transmittance of 50% or more for the perpendicularly incident light here indicates that the average transmittance of the film at wavelengths of 450 to 650 nm is 50% or more. By having a high transmittance for light in the visible light region of wavelengths 450 to 650 nm in this way, it can exhibit excellent permeability to external information such as scenery even when incorporated as a display base material for HUD or HMD. From the above viewpoints, 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, since it has the same transparency as ordinary transparent members such as glass, glasses, and acrylic plates, it can be used without imposing any burden on the user. There is no particular limitation on 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 obtaining the average value from the obtained values. (Detailed measurement conditions are shown in the examples.).

[0015] In order to obtain such a laminated film, as a final product, it is achieved by reducing the refractive index difference in the direction parallel to the film surface between the two thermoplastic resin layers laminated alternately. For example, if the refractive index difference in the direction parallel to the film surface is 0.06 or less, the transmittance can be 50% or more; if it is 0.04 or less, the transmittance can be 70% or more; and if the refractive index difference is 0.02 or less, it becomes easy to make the transmittance 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 (when layers A and B are laminated alternately, the difference in the in-plane refractive index between layer A and layer B). Each refractive index can be measured using an Abbe refractometer at 25°C with a sodium D line (wavelength 589 nm) as the light source and methylene iodide as the mounting liquid.

[0016] In the case of the laminated film of the present invention, when the reflectivities (%) of the respective P waves when incident at angles of 20°, 40°, and 60° with respect to the normal of the film surface are R20, R40, and R60, it is preferable to satisfy the relationship of R20 ≤ R40 < R60. The reflectivity referred to here is the average reflectivity with a wavelength of 450 to 650 nm. In the case of a general transparent substrate such as glass or a transparent film, as the incident angle gradually increases from 20° with respect to the normal of the film surface, the reflectivity of the P wave, which is one of the polarized lights, decreases, and the reflectivity becomes 0% at an angle called the Brewster angle. Therefore, when information is projected onto the transparent substrate from an incident angle near the Brewster angle, the displayability of the information (image) deteriorates due to the low reflectivity. Therefore, when the relationship of R20 ≤ R40 < R60 is satisfied when the reflectivities of the respective P waves when incident at angles of 20°, 40°, and 60° with respect to the normal of the film surface are R20, R40, and R60, since it does not have an angle corresponding to the Brewster angle, it is possible to display the information more clearly even when information is projected onto the film surface from an oblique direction. Note that R20, R40, and R60 can be calculated by adjusting the incident angle, measuring the reflectivity at each wavelength with a spectrophotometer, and obtaining the average value from the obtained values (detailed measurement conditions are shown in the examples).

[0017] Further, it is also preferable that R60 of the laminated film of the present invention is 30% or more. If the reflectivity of the P wave at 60° incidence is 30% or more, it is possible to display the information with higher clarity, particularly in a display device using a method of projecting information from the side, such as an HUD. From this viewpoint, more preferably, the reflectivity at 60° incidence is 40% or more, and even more preferably 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, it refers to the difference in the refractive index perpendicular to the surfaces of layers A and B). For example, when the number of layers reaches 800, if the refractive index difference is 0.08 or more, the reflectivity can be made 30% or more, and if the refractive index difference is 0.12 or more, the reflectivity can be made 50% or more easily.

[0018] The laminated film of the present invention preferably has a change amount of the average transmittance in the wavelength range of 450 to 650 nm of 10% or less when treated at 100°C for 250 hours. Here, the "change amount of the average transmittance in the wavelength range of 450 to 650 nm when treated at 100°C for 250 hours" refers to the average value of the transmittances 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° with respect to at least one surface of the laminated film, and the average value of the transmittances of each wavelength in the wavelength range of 450 nm to 650 nm when the same laminated film is left in an atmosphere of 100°C for 250 hours and P-polarized light is incident at an incident angle of 60° on the same location and the same surface of the laminated film.

[0019] The fact that the change amount of this average transmittance is 10% or less means that the reflection performance of the laminated film is maintained even in a high-temperature environment. That is, when the laminated film is applied to applications where long-term use in a high-temperature environment is assumed, such as the transparent base material of in-vehicle HUDs and HMDs, the change in display performance can be reduced. From the above viewpoints, the smaller the change amount of this average transmittance, the more preferable it is. A more preferable change amount of the average transmittance is 5.0% or less, still more preferably 3.0% or less, and particularly preferably 2.0% or less. When the change amount of the average transmittance is 2.0% or less, it becomes possible to be suitably applied to all in-vehicle applications. In addition, since the smaller the change amount of this average transmittance, the more preferable it is, there is no lower limit, but from the viewpoint of feasibility, it is 0.01%.

[0020] As a method for making the change amount of the average transmittance in the wavelength range of 450 to 650 nm when the laminated film is treated at 100 °C for 250 hours be 10% or less or within the above-mentioned preferred range, there is a method in which the laminated film is in a form containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more. Preferably, at least one of the thermoplastic resins constituting the laminated film is a polyester resin containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more. By selecting the constituent components of the aromatic dicarboxylic acid unit or the aromatic diol unit, a more preferred range can be achieved. Thereby, while having the high display performance of the HUD system, the stability of the laminated film in a high-temperature environment is enhanced, so that a decrease in display performance during long-term use can be reduced.

[0021] The laminated film of the present invention preferably has a change amount of color tone of 6.0 or less when treated at 100 °C for 250 hours. Here, the "change amount of color tone when treated at 100 °C for 250 hours" refers to the difference between the average value of the color tone of the laminated film and the average value of the color tone after the laminated film is left in an atmosphere of 100 °C for 250 hours. At this time, the measurement of the color tone of the laminated film is performed at the same location and on the same surface before and after the treatment, and a known colorimeter (for example, a colorimeter (SPECTROPHOTOMETER CM-3600d) manufactured by KONICA MINOLTA) can be used for the measurement of the color tone.

[0022] By setting the amount of change in this color tone to 6.0 or less, discoloration of the laminated film when used in a high-temperature environment can be suppressed. Therefore, by using the laminated film as a transparent substrate for HUD or HMD, it becomes possible to obtain a display member that can maintain the color recognition of information from the outside such as scenery and information displayed from the projection member over a long period of time. From the above viewpoints, the smaller the amount of change in this color tone, the more preferable it is. A more preferable amount of change in color tone is 5.0 or less, even more preferably 4.0 or less, particularly preferably 3.0 or less, and most preferably 2.0 or less. For example, if the amount of change in this color tone is 5.0 or less, it can be suitably used in a mode where the color recognition of external information, such as projecting instrument information on a part of the front glass, has little impact on the passengers even if it slightly decreases. Also, when the amount of change in this color tone is 2.0 or less, it can be suitably used for many in-vehicle applications including display on the entire front glass. Note that since the smaller the amount of change in this color tone, the more preferable it is, there is no lower limit, but from the perspective of feasibility, it is 0.01.

[0023] As a method of setting the amount of change in color tone of the laminated film to 6.0 or less or the above-preferred range when processed at 100 °C for 250 hours, for example, there is a method of making the laminated film in a form containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit with a number average molecular weight of 200 or more. Preferably, at least one of the thermoplastic resins constituting the laminated film is a polyester resin containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit with a number average molecular weight of 200 or more, and more preferably, a mode in which the diol unit constituting the polyester resin contains a paraxylene glycol unit. Thereby, while having high display performance of the HUD system, the stability of the laminated film in a high-temperature environment is enhanced, so that a decrease in the display performance of the HUD can be reduced even during long-term use.

[0024] 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 the transparency of the laminated film when used in a long-term high-temperature environment can be suppressed. Such a laminated film can be preferably used for applications exposed to a high-temperature environment, such as a transparent substrate for in-vehicle HUDs and HMDs. From the above viewpoints, it is preferable that the lower the internal haze, the better the transparency of the laminated film in a high-temperature environment. A more preferable internal haze is 1.8% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. There is no particular limitation on 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 a flowing paraffin focus.

[0025] As a method for making the internal haze after treatment at 150°C for 2 hours less than 2.0% or within the above preferable range, the same method as the method for making the change amount of the average transmittance in the wavelength range of 450 to 650 nm when the resin film is treated at 100°C for 250 hours 10% or less or within the above preferable range can be mentioned.

[0026] From the viewpoints of amorphization, high refractive index, low glass transition temperature, and heat resistance, the laminated film of the present invention needs to contain an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more. Here, the aromatic dicarboxylic acid unit is a structural unit constituting the molecular chain of the thermoplastic resin, and among the monomer constituent units directly bonded to the carbonyl carbon of the carbonyl group of the two ester bonds, it contains an aromatic group. The aromatic diol unit and the alkylene glycol unit having a number average molecular weight of 200 or more can be similarly interpreted, and each contains an aromatic group or an alkylene glycol having a number average molecular weight of 200 or more among the monomer constituent units directly bonded to the oxygen of the two ester bonds. When specifying the structural unit of the thermoplastic resin contained in the laminated film, it can be confirmed by hydrolyzing the ester bond forming the molecular chain of the thermoplastic resin with an alkali or the like, separating it by HPLC, GPC, etc., and then analyzing it by NMR or the like. The number average molecular weight can be calculated from the spectrum of 1H-NMR measured by dissolving the laminated film, and the detailed method is shown in the examples.

[0027] Also, when the number average molecular weight of the alkylene glycol is less than 200, when synthesizing the thermoplastic resin, due to its high volatility, the alkylene glycol may not be sufficiently incorporated into the polymer, 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. The upper limit of the number average molecular weight of the alkylene glycol is not particularly limited, but when it is greater than 2000, the reactivity may decrease during the production of the thermoplastic resin, making it unsuitable for film production. Therefore, from the viewpoint of productivity, it is more preferably 1500 or less, further preferably 1000 or less, and particularly preferably 600 or less. Examples of the alkylene glycol include polyethylene glycol, polytrimethylene glycol, and polytetramethylene glycol.

[0028] In addition, the laminated film "contains an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more" means that all of these structural units are included in the thermoplastic resin constituting the laminated film. That is, it may be either a mode in which one thermoplastic resin contains all of these structural units, or a mode in which, even if each thermoplastic resin does not contain all of these structural units, all of these structural units are included in the entire laminated film. As a specific example of the latter mode, for example, a laminated film is composed of two types of thermoplastic resins, one thermoplastic resin contains an aromatic dicarboxylic acid unit and an aromatic diol unit, and the other thermoplastic resin contains an alkylene glycol unit having a number average molecular weight of 200 or more.

[0029] From the above viewpoints, it is more preferable that at least one of the thermoplastic resins in the laminated film of the present invention contains a polyester resin containing all of an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more. By containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more, it is possible to achieve amorphization, high refractive index, and low glass transition temperature, and in addition, an effect of improving heat resistance in long-term high-temperature use can be obtained, resulting in a laminated film suitable for in-vehicle applications and the like. Also, in this mode, the preferable range of the number average molecular weight of the alkylene glycol is as described above. Examples of the alkylene glycol include polyethylene glycol, polytrimethylene glycol, and polytetramethylene glycol.

[0030] 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, an amorphization promoting effect can be obtained due to the bulkiness derived from paraxylene glycol and the small size of the unit, and while having high transparency and display performance, the stability of the laminated film in a high-temperature environment is enhanced. Therefore, it is possible to reduce a decrease in display performance even when used for a long time as a transparent base material for in-vehicle HUDs and HMDs. Further, from the above viewpoints, the content of the paraxylene glycol unit is preferably 25 mol% or more, more preferably 30 mol% or more, when the total diol units contained in the laminated film are 100 mol%. Note that, 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%. When the paraxylene glycol unit is 25 mol% or more, it becomes easy to suppress the internal haze after treatment at 150°C for 2 hours to less than 1.0%, and whitening of the laminated film due to heating can be suppressed, so that it can be suitably used for in-vehicle applications.

[0031] In the range including all of the above-described structural units, the laminated film of the present invention can contain various thermoplastic resins without particular limitation. Examples of the thermoplastic resin used in the present invention include chain polyolefins such as polyethylene, polypropylene, poly(4-methylpentene-1), and polyacetal; ring-opening metathesis polymers of norbornenes, addition polymers, and alicyclic polyolefins which are 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 copolymer-polymethyl methacrylate; polycarbonate; polypropylene terephthalate; polyethylene terephthalate; polybutylene terephthalate; polyesters such as polyethylene-2,6-naphthalate; polyethersulfone; polyetheretherketone; modified polyphenylene ether; polyphenylene sulfide; polyetherimide; polyimide; polyarylate; tetrafluoroethylene resin; trifluoroethylene resin; chlorotrifluoroethylene resin; tetrafluoroethylene-hexafluoropropylene copolymer; polyvinylidene fluoride and the like. Among these, from the viewpoints of strength, heat resistance, transparency, and versatility, it is more preferable to use polyester in particular. These may be copolymers or mixtures of two or more resins.

[0032] As this polyester, a polyester obtained by polymerization from monomers mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol is preferred. Here, examples of the aromatic dicarboxylic acid 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. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and their ester derivatives. Among them, 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 further, oxyacids such as hydroxybenzoic acid may be partially copolymerized.

[0033] In addition, examples of the diol component 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, isosorbide, spiroglycol, p-xylene glycol, and the like. Among them, ethylene glycol is preferably used from the viewpoints of easy availability, cost, and film-forming property. These diol components may be used alone or in combination of two or more.

[0034] Among the above-mentioned polyesters, it is preferable to use polyethylene terephthalate and its copolymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, and further polyhexamethylene terephthalate and its copolymers, polyhexamethylene naphthalate and its copolymers, etc. in the thermoplastic resin of the present invention.

[0035] Particularly in the laminated film of the present invention, among the alternately laminated layers, it is preferable that the resin constituting one layer (layer A) 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 means that, in accordance with JIS K7122 (1987), 5 g of the resin is heated from 25°C to 300°C at a heating rate of 20°C / min (1st RUN) at a heating rate of 20°C / min, held for 5 minutes in that state, and then rapidly cooled so that the temperature becomes 25°C or lower, and then heated again from room temperature to 300°C at a heating rate of 20°C / min. In the differential scanning calorimetry chart of the 2nd RUN thus obtained, it is a thermoplastic resin in which the heat of crystal fusion ΔHm determined from the peak area of the melting peak is 5 J / g or less, 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 while the sample is in the furnace. On the other hand, the crystalline resin refers to a thermoplastic resin that does not satisfy the above requirements in the above-mentioned differential scanning calorimetry chart. For example, when one type of crystalline thermoplastic resin is used in one layer A of the thermoplastic resin and an amorphous thermoplastic resin is used in the other layer B, even when made into a laminated film, it will show only one melting point.

[0036] The laminated film of the present invention preferably contains a polycyclic aromatic compound as a copolymer component as an amorphous thermoplastic resin. By containing a polycyclic aromatic compound such as naphthalene or anthracene, it becomes easy to increase the refractive index. More preferably, it is a copolymer containing three or more types of dicarboxylic acid units and diol units in total. In the case of a thermoplastic resin composed of one type of dicarboxylic acid unit and one type of diol unit, due to its high symmetry, orientation and crystallization are promoted during stretching, and it may not be possible to maintain the amorphous state. However, by including a copolymer containing three or more types of dicarboxylic acid units and diol units, orientation and crystallization are suppressed when stretched, and it becomes easy to maintain the amorphous state.

[0037] Also, in the laminated film of the present invention, it is preferable that any one of the layers constituting the laminated film contains an alkylene glycol unit having a number average molecular weight of 200 or more. As described above, in order to increase the refractive index, it is necessary to contain many cyclic structures derived from aromatic groups. Furthermore, by including 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 laminated film in which the in-plane refractive index of each layer constituting the laminated 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 an alkylene glycol having a number average molecular weight of 200 or more. More preferably, layer B made of an amorphous thermoplastic resin consists only of an amorphous thermoplastic resin containing a structure derived from an alkylene glycol having a number average molecular weight of 200 or more. By using a thermoplastic resin containing a structure derived from an alkylene glycol having a number average molecular weight of 200 or more by mixing it in a small amount with other amorphous resins, it becomes possible to further 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 an alkylene glycol having a number average molecular weight of 200 or more, it is possible to suppress the precipitation of a thermoplastic resin containing a structure derived from an alkylene glycol on the surface of the laminated film even when processing under high temperature conditions is carried out.

[0038] The laminated film of the present invention preferably contains p-xylene glycol in the aromatic diol units of the amorphous polyester resin. Due to the bulkiness derived from p-xylene glycol and the small size of the unit, an amorphous promoting effect is obtained. As a result, while having high transparency and display performance for transparent substrates for in-vehicle HUDs and HMDs, the stability of the laminated film under high-temperature environments is enhanced, so that a decrease in display performance can be reduced even during long-term use.

[0039] The laminated film of the present invention preferably contains 10 mol% or more of p-xylene glycol units in all the diol units of the amorphous polyester resin. Thereby, the stability of the laminated film under high-temperature environments is improved. Furthermore, when the content of p-xylene glycol units is 25 mol% or more, when used in in-vehicle HUDs and HMDs, while maintaining high transparency and display performance of the transparent substrate, the stability of the resin film under high-temperature environments is also enhanced, so that a decrease in display performance can be reduced even during long-term use. With an increase in the content of p-xylene glycol units, in order to satisfy higher transparency and display properties, a more preferable content of p-xylene 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 p-xylene glycol units is 40 mol%. When the p-xylene glycol units are 25 mol% or more, it becomes easy to suppress the internal haze after treatment at 150°C for 2 hours to less than 1.0%, and whitening of the laminated film due to heating is suppressed, so it can be suitably used for in-vehicle applications. Also, when the p-xylene glycol units are 30 mol% or more, the laminated film does not whiten even under severe high-temperature conditions of 150°C, and it can be applied to uses with more stringent specifications such as front glass.

[0040] In addition, various additives, such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and nucleating agents, can be added to the thermoplastic resin alone or in combination of multiple components to such an extent that their properties are not deteriorated.

[0041] Next, the image display member of the present invention will be described. The image display member of the present invention includes 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.

[0042] When laminating the laminated film of the present invention with a transparent member, 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. Examples of the form of these adhesive layers before processing include liquid, gel, block, powder, and film. Examples of 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 may be a known method such as lamination molding or injection molding, and the image display member is produced by applying heat and pressure and using the above-mentioned method for solidifying the adhesive layer.

[0043] Furthermore, the surface of the image display member may have various functional layers such as a hard coat layer, an abrasion-resistant layer, a scratch-preventing layer, an antireflection layer, a color correction layer, an ultraviolet absorption layer, a light stabilizer layer (HALS), a heat ray absorption layer, a printing layer, a gas barrier layer, an adhesive layer, and a transparent electrode layer. Examples of the image display member in which the laminated film of the present invention is laminated between two transparent members include the front glass of a vehicle such as an automobile. As its configuration, for example, a configuration of glass / polyvinyl butyral / the laminated film of the present invention / polyvinyl butyral / glass, a configuration of glass / polyvinyl butyral / the laminated film of the present invention / glass, etc. can be adopted. The glass thickness is preferably in the range of 2 mm to 3 mm, and the polyvinyl butyral thickness is preferably 100 μm to 1000 μm.

[0044] The image display member of the present invention preferably has an S-wave reflectance (Rs60) of 30% or less when incident at an incident angle of 60°. When the image display member of the present invention is used as an HUD, since high displayability of information and high visibility of external information such as the scenery outside seen through the display part are required, the visibility of external information such as the scenery outside can be enhanced by Rs60 being 30% or less. Examples of the method for making Rs60 30% or less include a method of forming an AR (antireflection), AG (antiglare), a moth-eye structure having a plurality of conical convex portions smaller than the wavelength of visible light, etc. on the surface of the image display member. In addition, since the inclination angle of the front glass of an automobile is often around 60°, when the image display member of the present invention is used for the front glass of an automobile, it is particularly preferable that Rs60 is 30% or less.

[0045] Next, the image display device of the present invention will be described. The image display device of the present invention includes the 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 of the display surface of the image display member of the present invention. The incident angle of the light with respect to the normal is preferably 40° or more and 75° or less. Such an image display device can display information clearly and with high reproducibility on the image display member while maintaining the transparency in the front direction. The light source is not particularly limited as long as the effects of the present invention are not impaired. Examples include liquid crystal projectors, RGB lasers, DLP (Digital Light Processing), LCOS (Liquid crystal on silicon), and the like. 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 through reflection by a mirror, condensing through a lens, passing through a diffusion or polarization reflection member, or the like. As this mirror, a cold mirror that reflects only visible light is preferable. In a mirror that reflects from normal visible light to infrared light, when sunlight or the like that has entered the image display device is reflected by the mirror and irradiated onto the light source, it causes a temperature rise due to infrared light. However, since a cold mirror does not reflect infrared light, it can suppress the temperature rise of the light source. Since the polarization reflection member reflects light in one azimuth direction (reflection axis azimuth) with respect to its surface and transmits light in a direction orthogonal to that direction (transmission axis azimuth), it can reduce by about half the 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 so as to match the transmission axis azimuth of the polarization reflection member, it is also possible to suppress the attenuation of the brightness of the light projected from the light source.

[0046] The image display device of the present invention can be used as a head-up display (HUD) or a head-mounted display (HMD) used in automobiles, airplanes, electronic billboards, game devices, etc. When used in an automobile, information is projected from a small projector onto a prompter made of a transparent base material provided near the front glass or in the vicinity of the front glass of the automobile. Here, by using the laminated film of the present application on the front glass or the 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 bonded to the front glass via an adhesive, or may be inserted inside the laminated glass used for the front glass. Further, the prompter may also be used by bonding it to the transparent base material.

[0047] In the image display device of the present invention, it is preferable that the azimuth angle of the main alignment axis of the laminated film is within ±30° with respect to the floor surface. Here, the azimuth angle in the horizontal direction with respect to the floor surface is set to 0°. Generally, natural light is polarized by reflection from buildings, the ground, etc., and S-polarization is mainly present. When external information such as the scenery outside passes through the image display device of the present invention, the azimuth angle of the S-polarization is in the horizontal direction with respect to the floor surface. Since the laminated film of the present invention is produced by stretching in at least two directions, it has optical properties such as biaxiality and a main alignment axis. When polarized light passes through the laminated film at an angle greater than 0 with respect to the main alignment axis of the laminated film, the polarization state of the transmitted light changes. That is, when the transmitted polarized light is information such as the scenery outside, unevenness of an iris pattern that is not present in the original scenery may be visually recognized due to the change in the polarization state. The unevenness of this iris pattern has a maximum intensity at 45° with respect to the main alignment axis of the laminated film and the azimuth angle of the polarized light that has passed through. Therefore, by reducing this azimuth angle, the unevenness of the iris pattern can be reduced. Preferably, the azimuth angle of the main alignment axis of the laminated film is within ±15° with respect to the floor surface, and more preferably within ±10°. Thus, the projection image display device of the present invention can enhance the visibility of external information such as the scenery outside by setting the azimuth angle of the main alignment axis of the laminated film within ±30° with respect to the floor surface. In particular, the suppression of this unevenness of the iris pattern is important when the image display device of the present invention is applied to the front glass of an automobile.

[0048] 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 include the image display device of the present invention. The image display device of the present invention is excellent in visibility of information from the outside such as scenery, displayability of information from the projection member, color reproduction, and reduction of distortion by the laminated film of the present invention.

[0049] Hereinafter, examples of specific embodiments for manufacturing the laminated film of the present invention will be described below, but the laminated film of the present invention is not construed as being limited by such examples. When the laminated film of the present invention has the above-described laminated film configuration, a laminated structure of 50 layers or more can be produced by the following method. Thermoplastic resin is supplied from two extruders, an extruder A corresponding to layer A and an extruder B corresponding to layer B, and the polymers from the respective flow paths are laminated to 50 layers or more 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. Then, the melt laminate is melt extruded into a sheet shape using a T-die or the like, and thereafter, it is cooled and solidified on a casting drum to obtain an unstretched laminated film. As a method for improving the lamination accuracy of layer A and layer B, the methods described in JP-A-2007-307893, Patent No. 4691910, and Patent No. 4816419 are preferable. Also, if necessary, it is also preferable to dry the thermoplastic resin used for layer A and the thermoplastic resin used for layer B.

[0050] Subsequently, stretching and heat treatment are performed on this unstretched laminated film. As the stretching method, a known sequential biaxial stretching method or 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, 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. For the stretching in the longitudinal direction, it is preferable to perform stretching by utilizing the speed change between the rolls of a longitudinal stretching machine. Also, for the stretching in the width direction, a known tenter method is utilized. That is, while gripping both ends of the film with clips and conveying it, the film is stretched in the width direction by widening the clip interval between both ends of the film.

[0051] Also, it is also preferable to perform simultaneous biaxial stretching in the tenter. The case of performing simultaneous biaxial stretching will be described. The unstretched laminated film cast on the cooling roll is guided to a simultaneous biaxial tenter, and while gripping both ends of the film with clips and conveying it, it is stretched simultaneously and / or stepwise in the longitudinal direction and the width direction. The stretching in the longitudinal direction is achieved by widening the distance between the clips of the tenter, and the stretching in the width direction is achieved by widening the interval between the rails on which the clips travel. The tenter clip for performing stretching and heat treatment in the present invention is preferably driven by a linear motor method. In addition, there are a pantograph method, a screw method, etc., but among them, the linear motor method is excellent in that the degree of freedom of each clip is high and the stretching ratio can be freely changed.

[0052] Furthermore, it is also preferable to perform heat treatment after stretching. The heat treatment temperature is preferably in the range of the stretching temperature or higher to the melting point of the thermoplastic resin of layer A - 10°C or lower, and it is also preferable to go through a cooling process at a temperature of the heat treatment temperature - 30°C or lower after the heat treatment. Also, in order to reduce the heat shrinkage rate of the film, it is also preferable to shrink (relax) the film in the width direction and / or the longitudinal direction during the heat treatment process or the cooling process. The relaxation ratio is preferably in the range of 1% to 10%, more preferably in the range of 1 to 5%. Finally, the laminated film of the present invention is manufactured by winding the film with a winder.

[0053] The laminated film of the present invention thus obtained can maintain its reflection performance over a long period even in a high-temperature environment and can be suitably used for an image display member.

Examples

[0054] Hereinafter, the laminated film of the present invention will be described using examples.

[0055] (Measurement method of physical properties and evaluation method of effects) The evaluation method of physical property values and the evaluation method of effects are as follows.

[0056] (1) Number of laminations Regarding the layer structure of the laminated film, for a sample whose cross-section was cut out by the cryo-ultramicrotomy method using a microtome, the number of laminations of the multilayer laminated film was confirmed by observing with a transmission electron microscope (TEM). More specifically, a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.) was used, and a cross-sectional photograph of the film was taken under the conditions of an acceleration voltage of 75 kV and an observation magnification of 20,000 times, and the number of laminations was confirmed.

[0057] (2) Average transmittance An angle-variable unit attached to a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. and a polarizer manufactured by Glan-Taylor were attached, and the transmittance in the wavelength range of 400 to 1600 nm when P-polarized light or S-polarized light was incident so that the incident angle with respect to the surface of the laminated film as the measurement specimen was 0° was measured at 1-nm intervals, and the average transmittance in the wavelength range of 450 nm to 650 nm was obtained respectively. As the measurement conditions, the slit was 2 nm (visible), automatic control (infrared), the gain was set to 2, and the scanning speed was 600 nm / min.

[0058] (3) Average reflectance An angle-variable unit attached to a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. and a polarizer manufactured by Glan-Taylor were attached, and P-polarized light or S-polarized light was incident on the laminated film surface, which is the measurement specimen, at incident angles of 0°, 20°, 40°, and 60°. The transmittance in the wavelength range of 400 to 1600 nm was measured at 1-nm intervals, and the average reflectance in the wavelength range of 450 nm to 650 nm was obtained respectively. As measurement conditions, the slit was set to 2 nm (visible) and automatic control (infrared), the gain was set to 2, and the scanning speed was set to 600 nm / min.

[0059] (4) Change amount of average transmittance in the wavelength range of 450 to 650 nm The laminated film was left standing in a 25°C atmosphere for 250 hours, and the average transmittance in the wavelength range of 450 to 650 nm was obtained in the same manner as in the evaluation method (2), except that P-polarized light was incident at an incident angle of 70°. Subsequently, the laminated film was left standing in a 100°C atmosphere for 250 hours, and P-polarized light was incident at an incident angle of 70° on the same film surface and the same measurement location as during the measurement after being left standing in a 25°C atmosphere for 250 hours. The average transmittance in the wavelength range of 450 to 650 nm was obtained in the same manner as in the evaluation method (2). The difference between the two was obtained from these values and was taken as the change amount of the average transmittance in the wavelength range of 450 to 650 nm.

[0060] (5) Change amount of color The color of the laminated film left standing in a 25°C atmosphere for 250 hours was measured using a colorimeter (SPECTROPHOTOMETER CM-3600d) manufactured by KONICA MINOLTA. Subsequently, the laminated film was left standing in a 100°C atmosphere for 250 hours, and the color was measured in the same manner at the same film surface and the same measurement location as during the measurement after being left standing in a 25°C atmosphere for 250 hours. The difference between the two was obtained from these values and was taken as the change amount of color.

[0061] (6) Internal haze after treatment at 150°C for 2 hours After leaving the laminated film in an atmosphere of 150°C for 2 hours, it was placed in a quartz cell for liquid measurement and filled with liquid paraffin, and the internal haze excluding the film surface haze was measured by using a haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd. The same measurement was repeated 3 times by randomly changing the measurement position, and the average value of the obtained values was taken as the internal haze value of the laminated film.

[0062] (7) Number average molecular weight of alkylene glycol The film was dissolved in HFIP-d2 (hexafluoro-2-propanol-d2), and 1H-NMR was measured. For the obtained spectrum, when the area of the signal having a peak at a chemical shift of 3.8 ppm was S1 and the area of the signal having a peak at a chemical shift of 3.9 ppm was S2, S1 / S2 × 44 (44: formula weight of the repeating unit of ethylene glycol) was determined, and the obtained value was taken as the number average molecular weight of alkylene glycol.

[0063] (8) Refractive index Using the sodium D line (wavelength 589 nm) as the light source and methylene iodide as the mounting liquid, the refractive indices in the longitudinal direction, width direction, and thickness direction of the film were determined at 25°C using an Abbe refractometer. Here, the average value of the refractive indices in the longitudinal direction and width direction 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 thickness direction of the film was taken as the refractive index in the direction perpendicular to the film surface (out-of-plane refractive index).

[0064] (Resin used for the film) The following resins were used for the production of the films in each example and each comparative example. Note that Resin 1 is a crystalline resin, and Resins 2 to 8 are amorphous resins.

[0065] Resin 1: Polyethylene terephthalate with IV = 0.65. In-plane refractive index = 1.65, out-of-plane refractive index = 1.49 in the film described in Comparative Example 2.

[0066] Resin 2: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.62, and out-of-plane refractive index = 1.62 (80 mol% of 2,6-naphthalenedicarboxylic acid component based on the total acid component, 20 mol% of isophthalic acid component based on the total acid component, 96 mol% of ethylene glycol based on the total diol component, and 4 mol% of polyethylene glycol with a number average molecular weight of 400 based on the total diol component).

[0067] Resin 3: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.64, and out-of-plane refractive index = 1.64 (100 mol% of 2,6-naphthalenedicarboxylic acid component based on the total acid component, 66 mol% of ethylene glycol based on the total diol component, 30 mol% of p-xylene glycol based on the total diol component, and 4 mol% of polyethylene glycol with a number average molecular weight of 400 based on the total diol component).

[0068] Resin 4: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.63, and out-of-plane refractive index = 1.63 (100 mol% of 2,6-naphthalenedicarboxylic acid component based on the total acid component, 71 mol% of ethylene glycol based on the total diol component, 25 mol% of p-xylene glycol based on the total diol component, and 4 mol% of polyethylene glycol with a number average molecular weight of 400 based on the total diol component).

[0069] Resin 5: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.63, and out-of-plane refractive index = 1.63 (100 mol% of 2,6-naphthalenedicarboxylic acid component based on the total acid component, 76 mol% of ethylene glycol based on the total diol component, 20 mol% of p-xylene glycol based on the total diol component, and 4 mol% of polyethylene glycol with a number average molecular weight of 400 based on the total diol component).

[0070] Resin 6: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.63, and normal refractive index = 1.63 (the 2,6-naphthalenedicarboxylic acid component is 100 mol% of the total acid component, ethylene glycol is 86 mol% of the total diol component, p-xylene glycol is 10 mol% of the total diol component, and polyethylene glycol with a number average molecular weight of 400 is 4 mol% of the total diol component copolymerized polyethylene naphthalate).

[0071] Resin 7: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.63, and normal refractive index = 1.63 (the 2,6-naphthalenedicarboxylic acid component is 100 mol% of the total acid component, ethylene glycol is 83 mol% of the total diol component, BPEF is 10 mol% of the total diol component, and polyethylene glycol with a number average molecular weight of 400 is 7 mol% of the total diol component copolymerized polyethylene naphthalate).

[0072] Resin 8: A copolymer of polyethylene naphthalate with IV = 0.65, in-plane refractive index = 1.63, and normal refractive index = 1.63 (the 2,6-naphthalenedicarboxylic acid component is 100 mol% of the total acid component, ethylene glycol is 89 mol% of the total diol component, BPEF is 5 mol% of the total diol component, and polyethylene glycol with a number average molecular weight of 400 is 6 mol% of the total diol component copolymerized polyethylene naphthalate).

[0073] (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, passed through five FSS-type leaf disk filters, and then metered by a gear pump so that the discharge ratio (lamination ratio) was Resin 1 / Resin 3 = 1.5, and designed so that the reflection wavelength of the P wave at an incident angle of 70° was in the range of 400 nm to 1000 nm. They were then alternately merged in an 801-layer feed block (401 layers for Layer A and 400 layers for Layer B). Next, the laminated body of the molten thermoplastic resin formed into a sheet was discharged 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 charging voltage of 8 kV with a wire to obtain an unstretched laminated film. This unstretched laminated film was longitudinally stretched at a temperature of 93 °C and a stretching ratio of 3.2 times to obtain a uniaxially oriented laminated film. After subjecting both surfaces of the film to corona discharge treatment in air, a laminated forming film coating liquid composed of (a polyester resin with a glass transition temperature of 18 °C) / (a polyester resin with a glass transition temperature of 82 °C) / silica particles with an average particle size of 100 nm was applied to both surfaces. Thereafter, both end portions in the width direction of the uniaxially oriented laminated film were gripped with clips and guided to a tenter, and then laterally stretched 3.9 times at 90 °C, followed by heat treatment at 216 °C and a 1.1% width direction relaxation. Finally, it was cooled at 100 °C to obtain a laminated film with a thickness of 80 μm (5 μm for both surface layers). The evaluation results are shown in Table 1.

[0074] (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 shown in Table 1 were used as the thermoplastic resins constituting each layer. The evaluation results are shown in Table 1.

[0075] (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 feed block (201 layers for Layer A and 200 layers for Layer B) designed so that the reflection wavelength of the P wave 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.

[0076] (Example 8) Resin 1 was used as the thermoplastic resin constituting layer A, and resin 3 was used as the thermoplastic resin constituting layer B. A laminated film was obtained in the same manner as in Example 1, except that a 201-layer feed block (101 layers of layer A and 100 layers of layer B) was designed so that the reflection wavelength of the P wave at an incident angle of 70° was in the range of 400 nm to 800 nm. The evaluation results are shown in Table 1.

[0077] (Comparative Example 2) A film was obtained in the same manner as in Example 1, except that a single-layer film made of Resin 1 was used without using a laminating apparatus. The evaluation results are shown in Table 1. Although the transparency in the front direction was high and the visibility was excellent, since it was a single layer, it did not show reflectivity in the oblique direction and the projected information could not be confirmed.

[0078] (Comparative Example 3) In the same manner as in Comparative Example 2, except that Resin 3 was used, it was supplied to a T-die and formed into a sheet shape to obtain an unoriented film. The evaluation results are shown in Table 1.

[0079] (Comparative Example 4) A laminated film was obtained in the same manner as in Example 1, except that a 3-layer feed block (thermoplastic resin A / thermoplastic resin B / thermoplastic resin A) was used. The evaluation results are shown in Table 1.

[0080]

Table 1

Industrial Applicability

[0081] The present invention is a laminated film for a projection image display member that has excellent transparency in the front direction, high visibility of information from the outside such as scenery, excellent displayability of information from a projection member and high reproducibility of color tone due to excellent reflectivity in the oblique direction, and suppresses distortion. The projection image display device using the laminated film of the present invention can be suitably used for head-up displays (HUD) and head-mounted displays (HMD) used in vehicles such as automobiles, airplanes, electronic display boards, game devices, and the like.

Claims

1. A laminated film in which two different types of thermoplastic resin layers (layer A and layer B) are alternately laminated in 50 or more layers, the laminated film containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more, the aromatic diol unit containing paraxylene glycol unit or BPEF, The thermoplastic resin constituting the layer A is polyethylene terephthalate containing an aromatic dicarboxylic acid unit, The thermoplastic resin constituting the layer B is a polyester resin containing an aromatic dicarboxylic acid unit and an alkylene glycol unit having a number average molecular weight of 200 or more, and containing paraxylene glycol or BPEF as the aromatic diol unit. The laminated film is characterized by this.

2. The laminated film according to claim 1, wherein the change amount of the average transmittance at wavelengths of 450 to 650 nm when treated at 100 ° C. for 250 hours is 10% or less.

3. The laminated film according to claim 1 or 2, wherein the change amount of the color tone when treated at 100 ° C. for 250 hours is 6.0 or less.

4. The laminated film according to any one of claims 1 to 3, wherein the internal haze after treatment at 150 ° C. for 2 hours is less than 2.0%.

5. The laminated film according to any one of claims 1 to 4, which contains 25 mol% or more of paraxylene glycol units in all the diol units constituting the polyester resin.

6. The transmittance of light incident perpendicular to the film surface is 50% or more, and when the reflectance (%) of each P wave when incident at angles of 20 °, 40 °, and 60 ° with respect to the normal of the film surface is R20, R40, and R60, respectively, the relationship of R20 ≦ R40 <R60 is satisfied, and R60 is 30% or more. The laminated film according to any one of claims 1 to 5.

7. An image display member including the laminated film according to any one of claims 1 to 6.

8. An image display device including the image display member according to claim 7 and a light source that irradiates light at an angle of 20 ° or more with respect to the normal of the display surface of the image display member.

9. A head-up display including the image display device according to claim 8.

Images