Patent Description:
In a vehicle head-up display as one of display devices, for example, a liquid crystal panel having display information is disposed inside an instrument board in a car, and light from a backlight and transmitted from the liquid crystal panel is emitted towards a front windshield by a mirror. The emitted light is incident to eyes of a driver after reflected by the front windshield, and the driver can visually confirm display information from the liquid crystal panel with a virtual image. Furthermore, in a vehicle, it is important to reduce the influence of thermal energy caused by infrared rays (infrared light) in an external light (sunlight) on the liquid crystal panel. Therefore, in Patent Document <NUM>, a vehicle head-up display is disclosed, in which an optical filter is disposed between a liquid crystal panel and a front windshield to block infrared light incident to the liquid crystal panel. Moreover, in Patent Document <NUM>, a vehicle head-up display that uses two types of polymer films as infrared light cut-off portions is disclosed.

<CIT> discloses a head up display device having a display light source and a liquid crystal panel emitting visible linearly polarized light waves, an infrared light cutting section having an infrared light cutting film having an infrared cutting layer transmitting visible light and reducing infrared light incident on the display source. A reflecting portion reflects the light from the display source. A layer birefringence is compensated by providing a further layer having crossed birefringence.

<CIT> and <CIT> disclose further head up display devices.

In the display device described in the abovementioned Patent Document <NUM>, when an optical filter comprises, for example, a stretched polymer film, the optical filter generates anisotropy in refractive index and exhibits birefringence. Therefore, when a visible light of a linearly polarized wave having display information emitted from a display portion is transmitted through the optical filter, the linearly polarized wave may sometimes be changed into an elliptically polarized wave. When the visible light of the elliptically polarized wave is reflected by a front windshield, a reflectance of the visible light changes according to components of the polarized wave. As a result, display information recognized by a driver is different from the display information when emitted from the display portion, and it is sometimes difficult to be confirmed visually. On the other hand, in the display device described in the abovementioned Patent Document <NUM>, a second polymer film is disposed on a first polymer film, and the second polymer film is used to compensate for birefringence generated in the first polymer film. However, further improvements are required to reduce the amount of infrared light incident to the liquid crystal panel while maintaining visual confirmation of the driver.

A display device according to the present invention comprises: a display portion emitting a visible light of a linearly polarized wave having display information; an infrared light cut-off portion transmitting the visible light from the display portion and reducing an incident amount of an infrared light to the display portion; and a reflecting portion reflecting the visible light transmitted through the infrared light cut-off portion, wherein the infrared light cut-off portion comprises an infrared light cut-off layer, the infrared light cut-off layer has a slow axis, and the slow axis is generally parallel to a vibration direction of the linearly polarized wave.

The infrared light cut-off portion of the display device transmits the visible light from the display portion, and meanwhile reduces the incident amount of the infrared light to the display portion. As a result, the brightness of the display information comprised by the visible light is maintained and meanwhile, for example, the influence of thermal energy caused by the infrared light in sunlight on the display portion is reduced. Moreover, the infrared light cut-off layer comprised in the infrared light cut-off portion has the slow axis, and the slow axis is generally parallel to the vibration direction of the linearly polarized wave. Therefore, compared with a scheme not according to the invention, in which the slow axis is not generally parallel to the vibration direction of the linearly polarized wave, a ratio of changing the visible light of the linearly polarized wave into the elliptical polarized wave after being transmitted from the infrared light cut-off portion is reduced. As a result, a visual confirmer such as a driver of a vehicle can easily recognize the display information comprised by the visible light emitted from the display portion as described above, and the visual confirmation of the display information will be maintained.

In a display device according to another scheme, the term "generally parallel" may mean that an angle formed by the slow axis and the vibration direction of the linearly polarized wave is greater than <NUM> degree and less than <NUM> degrees.

According to the display device, after the visible light from the display portion is transmitted from the infrared light cut-off portion, the ratio of changing the linearly polarized wave of the visible light into the elliptically polarized wave is further reduced. The ratio occupied by the elliptically polarized wave in the visible light passing through the infrared light cut-off portion is further reduced, and therefore, a visual confirmer who recognizes the visible light reflected by the reflecting portion can recognize similar display information by the display information of the visible light emitted from the display portion.

In a display device according to another scheme, an incidence angle of the linearly polarized wave with respect to the infrared light cut-off portion may be greater than <NUM> degree and less than <NUM> degrees.

According to the display device, it is easy to adjust an orientation of the infrared light cut-off portion with respect to a light path of the visible light from the display portion, so that a part of the external light, such as the sunlight, after reflected by the infrared light cut-off portion, does not proceed towards eyes of the visual confirmer such as the driver.

In a display device according to another scheme, the infrared light cut-off portion may further comprise an ultra-violet light cut-off layer reducing a transmittance of an ultra-violet light, and the infrared light cut-off layer and the ultra-violet light cut-off layer may both have transmissivity in a visible light region.

According to the display device, the infrared light cut-off portion further comprises the ultra-violet light cut-off layer, and therefore, the ultra-violet light comprised in the sunlight or the like is prevented from being irradiated to the display portion. Moreover, the infrared light cut-off layer and the ultra-violet light cut-off layer both have transmissivity in the visible light region, and therefore, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion will be maintained.

In a display device according to another scheme, the transmissivity may have a transmittance greater than <NUM>% in the visible light region.

According to the display device, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion will be further maintained.

In a display device according to another scheme, the infrared light cut-off portion may comprise a hard coating.

According to the display device, the infrared light cut-off portion may comprise the hard coating, and therefore, a mechanical strength of the infrared light cut-off portion is increased. Moreover, a resistance to scratches and the like is increased.

In a display device according to another scheme, the ultra-violet light cut-off layer may be an adhesive layer.

The ultra-violet light cut-off layer of the display device may be the adhesive layer, and therefore can be stacked to, for example, the infrared light cut-off layer by its adhesiveness.

In a display device according to another scheme, the display device may further comprise a window portion assembled on an opening provided in an instrument board of a vehicle and disposed between the display portion and the reflecting portion on a light path of the visible light, and the infrared light cut-off portion is provided between the window portion and the reflecting portion.

According to the display device, the infrared light cut-off portion is provided on the window portion and can protect the window portion. The window portion can be consisted of a material such as a resin having a small mechanical strength.

In a display device according to another scheme, the display device may further comprise a window portion assembled on an opening provided in an instrument board of a vehicle and disposed between the display portion and the reflecting portion on a light path of the visible light, and the infrared light cut-off portion is provided between the display portion and the window portion.

According to the display device, the infrared light cut-off portion and the display portion are disposed in the instrument board and, for example, can be protected by a window material such as glass.

According to one aspect of the present disclosure, it is easy to reduce the incident amount of the infrared light to the display portion on the basis of maintaining the visual confirmation of the display information.

A display device according to an implementation of the present disclosure comprises: a display portion emitting a visible light of a linearly polarized wave having display information; an infrared light cut-off portion transmitting the visible light from the display portion and reducing an incident amount of an infrared light to the display portion; and a reflecting portion reflecting the visible light transmitted through the infrared light cut-off portion, wherein the infrared light cut-off portion comprises an infrared light cut-off layer, the infrared light cut-off layer has a slow axis, and the slow axis is generally parallel to a vibration direction of the linearly polarized wave.

The infrared light cut-off portion of the display device transmits the visible light from the display portion, and meanwhile reduces the incident amount of the infrared light to the display portion. As a result, the brightness of the display information comprised by the visible light is maintained and meanwhile, for example, the influence of thermal energy caused by the infrared light in sunlight on the display portion is reduced. Moreover, the infrared light cut-off layer comprised in the infrared light cut-off portion has the slow axis, and the slow axis is generally parallel to the vibration direction of the linearly polarized wave. Therefore, compared with a scheme in which the slow axis is not generally parallel to the vibration direction of the linearly polarized wave, a ratio of changing the visible light of the linearly polarized wave into the elliptical polarized wave after being transmitted from the infrared light cut-off portion is reduced. As a result, a visual confirmer such as a driver of a vehicle can easily recognize the display information comprised by the visible light emitted from the display portion as described above, and the visual confirmation of the display information will be maintained.

It should be noted that, the term "display information" in the present specification widely comprises information that can be used to understand or recognize a specific meaning through visual confirmation. For example, in the case of a vehicle-mounted display device, maps, traffic signs, and other navigation information are widely comprised. The above "reduce the incident amount of the infrared light to the display portion" means reducing the incident amount of the infrared light to the display portion by absorbing or reflecting the infrared light. Furthermore, the above "anisotropy in refractive index" means that in a two-dimensional medium such as a polymer film, the refractive index varies according to each direction of a two-dimensional plane, that is, the refractive index has an in-plane anisotropy. Moreover, an "MD direction (Machine Direction)" indicates a direction (longitudinal direction) in which the polymer film is wound, and a "CD direction (Cross Machine Direction)" indicates a direction (lateral direction) perpendicular to the longitudinal direction.

Hereinafter, implementations of the display device are described in detail with reference to the accompanying drawings. In the present specification, the same reference numerals are used for the same elements, and repeated descriptions are omitted. In this implementation, an X-axis, a Y-axis, and a Z-axis are set for the accompanying drawings, but each of these axes are set for convenience of description. The Z-axis is set in a direction of a stack of the infrared light cut-off portion.

<FIG> is a view showing an example of a display device according to an implementation of the present disclosure. <FIG> shows an example in which a display device <NUM> according to the present implementation is applied as a vehicle head-up display. The display device <NUM> comprises a display portion <NUM>, an infrared light cut-off portion <NUM>, and a reflecting portion <NUM> in a vehicle <NUM>. The display device <NUM> may further comprise a light source <NUM>. The light source <NUM> comprises, for example, a hidden lamp, a halogen lamp, a light emitting diode, or a cold cathode tube. The light source <NUM> generates a visible light L1.

The display portion <NUM> comprises, for example, a liquid crystal panel, an organic EL panel, a digital mirror device, an MEMS display, and a laser display, and has display information. The display portion <NUM> receives the visible light L1 from the light source <NUM>, and emits a visible light L2 of a linearly polarized wave having the display information towards the infrared light cut-off portion <NUM>. In the case where the display portion <NUM> comprises an organic EL panel, the display portion <NUM> and the light source <NUM> may be integrated, and the display portion <NUM> integrated with the light source <NUM> can emit the visible light L2 towards the infrared light cut-off portion <NUM>. <FIG> shows an example in which the display portion <NUM> and the light source <NUM> are integrated.

In the present implementation, a first light path changing portion <NUM> and a second light path changing portion <NUM> may be further comprised between the display portion <NUM> and the infrared light cut-off portion <NUM>. After sequentially changed in its light path by the first light path changing portion <NUM> and the second light path changing portion <NUM>, the visible light L2 passing through the display portion <NUM> is incident on the infrared light cut-off portion <NUM>. That is, the visible light L2 is changed in its light path by the first light path changing portion <NUM> towards the second light path changing portion <NUM>, and then changed in its light path by the second light path changing portion <NUM> towards the infrared light cut-off portion <NUM>. The first light path changing portion <NUM> and the second light path changing portion <NUM> both comprise, for example, a mirror such as a flat mirror or a concave mirror.

The infrared light cut-off portion <NUM> reduces the incident amount of the infrared light to the display portion <NUM>. The infrared light is light comprised in sunlight and the like. Moreover, the infrared light cut-off portion <NUM> transmits the visible light L2 from the display portion <NUM> and emits a transmitted visible light L3 towards the reflecting portion <NUM>. The reflecting portion <NUM> comprises, for example, a front windshield of the vehicle <NUM>, and reflects the visible light L3 transmitted from the infrared light cut-off portion <NUM> towards a visual confirmer D1 such as a driver. Upon receiving the reflected visible light L4, the visual confirmer D1 can visually confirm the display information at a position SR separated by the front windshield in addition to the outside field of view in front of the vehicle <NUM>.

As described above, the infrared light cut-off portion <NUM> transmits the visible light L2 from the display portion <NUM> and meanwhile reduces the incident amount of the infrared light to the display portion <NUM>. As a result, the brightness of the display information comprised by the visible light L2 is maintained and meanwhile, for example, the influence of the thermal energy caused by the infrared light in the sunlight on the display portion <NUM> is reduced.

The vehicle <NUM> comprises an instrument board <NUM>, and an opening <NUM> may be disposed on the instrument board <NUM>. The opening <NUM> is provided in, for example, an upper portion 42a of the instrument board <NUM>. The display device <NUM> may further comprise a window portion <NUM>. The window portion <NUM> is assembled to the opening <NUM> and is disposed between the display portion <NUM> and the reflecting portion <NUM> on a light path of the visible light L2.

<FIG> are enlarged views of a region R1 shown in <FIG>. <FIG> shows a first example, and <FIG> shows a second example.

As shown in <FIG>, in the first example, the infrared light cut-off portion <NUM> may be provided between the window portion <NUM> and the reflecting portion <NUM>. Specifically, the infrared light cut-off portion <NUM> is provided, for example, on the window portion <NUM>. The infrared light cut-off portion <NUM> has a lower surface 20a and an upper surface 20b on the opposite side of the lower surface 20a, and the lower surface 20a is located, for example, on the window portion <NUM>.

In the first example, the visible light L2 from the display portion <NUM> is transmitted in the order of the window portion <NUM> and the infrared light cut-off portion <NUM>, and visible light L3 is emitted from the infrared light cut-off portion <NUM>. Moreover, an external light SL1 such as sunlight is incident to the infrared light cut-off portion <NUM>, and a part of the incident light SL1 is reflected by the upper surface 20b of the infrared light cut-off portion <NUM> and becomes a reflected light SL2.

The infrared light cut-off portion <NUM> of the display device <NUM> in the first example is provided on the window portion <NUM>, and thus can protect the window portion <NUM>. As a result, the window portion <NUM> can be formed by using a material such as a resin with a mechanical strength lower than that of glass or the like. For example, these materials may include polyester, polycarbonate, polysulfone, polyethersulfone, alicyclic olefin polymer, chain-like olefin polymer such as polyethylene or polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, modified acrylic polymer, epoxy resin, polystyrene, synthetic resin such as acrylic resin, and the like.

As shown in <FIG>, in the second example, the infrared light cut-off portion <NUM> may also be provided between the display portion <NUM> and the window portion <NUM>. In other words, the infrared light cut-off portion <NUM> may be disposed at a position below the window portion <NUM>, specifically, in the instrument board <NUM>. As a result, the infrared light cut-off portion <NUM> can be protected by the window portion <NUM>. In this case, it is ideal to form the window portion <NUM> by a window material strong enough to protect the infrared light cut-off portion <NUM>, and for example, the window material may include glass, reinforced plastic, or the like.

In the second example, the visible light L2 from the display portion <NUM> is transmitted in the order of the infrared light cut-off portion <NUM> and the window portion <NUM>, and the visible light L3 is emitted from the window portion <NUM>. Moreover, the external light SL1 such as the sunlight is incident to the window portion <NUM>, and a part of the incident light SL1 is reflected by the upper surface 46b of the window portion <NUM> and becomes a reflected light SL2.

According to the display device <NUM> of the second example, the infrared light cut-off portion <NUM> and the display portion <NUM> are disposed in the instrument board <NUM> and can be protected by the window material.

The infrared light cut-off portion <NUM> transmits the visible light L2 from one surface such as the lower surface 20a thereof, and reduces an amount of the incident infrared light SL1 from another surface such as the upper surface 20b. The infrared light cut-off portion <NUM> comprises an infrared light cut-off layer <NUM> (referring to <FIG>). The infrared light cut-off layer <NUM> may have transmissivity in a visible light region.

According to the display device <NUM>, the infrared light cut-off layer <NUM> has transmissivity in the visible light region, and therefore, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion <NUM> will be maintained. In the display device <NUM>, the transmissivity may have a transmittance greater than <NUM>% in the visible light region. According to the display device <NUM>, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion <NUM> will be further maintained.

The infrared light cut-off layer <NUM> comprises, for example, an infrared light cut-off film cut out from a stretched polymer film wound in a roller shape. The infrared light cut-off film may be composed of a polymer film, specifically a film such as a polyester film, that reduces the transmission amount of infrared light.

<FIG> is an external view schematically showing a stretched polymer film wound in a roller shape. <FIG> is a top view schematically showing the stretched polymer film of <FIG>. The stretched polymer film <NUM> is wound in the MD direction and, moreover, has a central region E1 and peripheral regions E2 arranged in the CD direction. The central region E1 is a region located between the peripheral regions E2 in the CD direction.

<FIG> is a top view of an infrared light cut-off film formed by cutting out a stretched polymer film in a central region. <FIG> is a top view of an infrared light cut-off film formed by cutting out a stretched polymer film in a peripheral region.

The stretched polymer film <NUM> has a feature that a refractive index in a direction of a main chain of a molecular chain constituting the polymer and a refractive index in a direction orthogonal to the main chain are different from each other. Moreover, the stretched polymer film <NUM> is stretched in its manufacturing process and has anisotropy in refractive index.

In the stretched polymer film <NUM>, the refractive index in the MD direction and the refractive index in the CD direction are different from each other. For example, when a polymer film having a positive inherent birefringence is stretched in the CD direction, the refractive index in the CD direction becomes greater than the refractive index in the MD direction. Moreover, as shown in <FIG>, in the stretched polymer film <NUM>, a slow axis SA1 indicating the direction having the largest refractive index is curved instead of linear in the CD direction.

As shown in <FIG>, the infrared light cut-off film can be formed by cutting out the stretched polymer film <NUM> from the central region E1 and the peripheral regions E2. In the present implementation, the infrared light cut-off film <NUM> having, for example, a generally rectangular two-dimensional shape may be cut out from the central region E1 of the stretched polymer film <NUM>. The infrared light cut-off film <NUM> has long sides <NUM> and short sides <NUM> generally perpendicular to the long sides <NUM>. The infrared light cut-off film <NUM> may be cut in a manner in which its long side <NUM> is generally parallel to the CD direction of the stretched polymer film <NUM>. In the infrared light cut film <NUM>, for example, in a case where a tangent direction of a central portion of the slow axis SA1 is set as a first axis Ax1, the first axis Ax1 is generally parallel to the CD direction of the infrared light cut film <NUM>, and on the other hand, a tangent line of each portion of the slow axis SA <NUM> except the central portion has an angle (orientation angle) AL1 that intersects with the first axis Ax1.

In the present implementation, an infrared light cut-off film <NUM> having, for example, a generally rectangular two-dimensional shape may be cut out from the peripheral region E2 of the stretched polymer film <NUM>. The infrared light cut-off film <NUM> has long sides <NUM> and short sides <NUM> generally perpendicular to the long sides <NUM>. The infrared light cut-off film <NUM> may be cut out in a manner in which its long side <NUM> is generally parallel to the slow axis SA1. In the infrared light cut-off film <NUM>, for example, in a case where a direction that intersects with a central portion of the slow axis SA1 and is generally parallel to the first axis Ax1 is set as a second axis Ax2, a tangent line of an intersection of the slow axis SA1 and the second axis Ax2 has an angle (orientation angle) AL2 that intersects with the second axis Ax2.

In the present implementation, the orientation angle AL2 is greater than the orientation angle AL1, and the orientation angle becomes greater as it goes from a central portion towards an end portion in the CD direction.

Then, the slow axis SA1 of the infrared light cut-off film <NUM> is described with reference to <FIG>. The infrared light cut-off film <NUM> is formed by cutting out the stretched polymer film <NUM> from the central region E <NUM>. A direction of the long sides <NUM> of the infrared light cut-off film <NUM> is generally parallel to a direction along the first axis Ax1, i.e., the slow axis SA1 of the infrared light cut-off film <NUM>.

The orientation angle AL1 of the slow axis SA <NUM> of the infrared light cut-off film <NUM> indicates a magnitude of deviation of the slow axis SA1 with respect to the first axis Ax1 in a plane of the infrared light cut-off film <NUM>. In the plane of the infrared light cut-off film <NUM>, if the orientation angle AL1 is small, it can be considered that the slow axis SA1 is generally parallel to the first axis Ax1. In order to be considered as being generally parallel, for example, the orientation angle AL1 preferably ranges from <NUM> degree to <NUM> degrees. Here, the orientation angle AL1 of <NUM> degree means that the slow axis SA1 is parallel to the first axis Ax1, and "generally parallel" also comprises "parallel.

For example, the orientation angle AL1 more preferably ranges from <NUM> degree to <NUM> degrees. By setting the orientation angle AL1 in the range, the slow axis SA1 of the infrared light cut-off film <NUM> can be more parallel to the first axis Ax1.

In addition to being rectangular, the two-dimensional shape of the infrared light cut-off film <NUM> may be, for example, quadrangle shaped such as square shaped or rhombus shaped, or circular, or elliptic.

Then, the slow axis SA1 of the infrared light cut-off film <NUM> is described with reference to <FIG>. The infrared light cut-off film <NUM> is formed by cutting out the stretched polymer film <NUM> from the peripheral region E2. It is shown that in a case where the tangent direction of the central portion of the slow axis SA <NUM> is set to a third axis Ax3, in the infrared light cut-off film <NUM>, a direction of its long side <NUM> is generally parallel to a direction along the third axis Ax3, i.e., the slow axis SA1 of the infrared light cut-off film <NUM>.

In the infrared light cut-off film <NUM>, a tangent line of each portion of the slow axis SA1 except the central portion has an angle (orientation angle) AL3 that intersects with the third axis Ax3, and the orientation angle AL3 indicates a magnitude of deviation of the slow axis SA1 with respect to the third axis Ax3 in the plane of the infrared light cut-off film <NUM>. In the plane of the infrared light cut-off film <NUM>, if the orientation angle AL3 is small, it can be considered that the slow axis SA1 is generally parallel to the third axis Ax3. In order to be considered as being generally parallel, for example, the orientation angle AL3 preferably ranges from <NUM> degree to <NUM> degrees.

For example, the orientation angle AL3 more preferably ranges from <NUM> degree to <NUM> degrees. By setting the orientation angle AL3 in the range, the slow axis SA1 of the infrared light cut-off film <NUM> can be more parallel to the third axis Ax3.

The two-dimensional shape of the infrared light cut-off film <NUM> is the same as that of the infrared light cut-off film <NUM>. In addition to being rectangular, for example, it may also be quadrangle shaped such as square shaped or rhombus shaped, or circular, or elliptic.

Then, the structure and material of the infrared light cut-off portion <NUM> are further described in detail with reference to <FIG> is a cross-sectional view of an infrared light cut-off portion according to an implementation of the present disclosure. The infrared light cut-off portion <NUM> comprises a substrate <NUM> and an infrared light cut-off layer <NUM>. The substrate <NUM> has an upper surface 21a and a lower surface 21b, and the infrared light cut-off layer <NUM> is, for example, provided on or above the upper surface 21a of the substrate <NUM>. The infrared light cut-off layer <NUM> comprises an infrared light cut-off film <NUM>.

The substrate <NUM> comprises, for example, polycarbonate, polyester, polysulfone, polyethersulfone, alicyclic olefin polymer, chain-like olefin polymer such as polyethylene or polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, modified acrylic polymer, epoxy resin, polystyrene, and synthetic resin such as acrylic resin. The thickness of the substrate <NUM> is, for example, <NUM> to <NUM>.

As the infrared light cut-off film <NUM> comprised in the infrared light cut-off layer <NUM>, a single-layer polymer film or a multi-layer polymer film containing an infrared-absorbing material can be used. The single-layer polymer film may comprise, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic-based resin, polycarbonate resin, olefin-based resin, and polyimide resin. The thickness of the single-layer polymer film is, for example, <NUM> to <NUM>.

The multi-layer polymer film may be a multi-layer optical film (MOF) stacked with a plurality of polymer films, and a multi-layer structure with an adjusted thickness of each layer is used to reflect infrared light. The thickness of each layer is, for example, <NUM> to <NUM>.

The polymer film of the infrared light cut-off film <NUM> comprises, for example, a polymer and a copolymer of crystalline, semi-crystalline, or liquid crystal.

The material comprised in the polymer film as the infrared light cut-off film <NUM> may comprise, for example, polyester, polyethylene naphthalate (PEN) (specifically naphthalene dicarboxylic polyester) and isomers thereof (e.g., <NUM>,<NUM>-, <NUM>,<NUM>-, <NUM>,<NUM>-, <NUM>,<NUM>-, and <NUM>,<NUM>-PEN), polybutylene naphthalate, polyalkylene terephthalate (e.g., polyethylene terephthalate, polybutylene terephthalate, and poly-<NUM>,<NUM>-cyclohexanedimethylene terephthalate), polyimide (e.g., polyacrylic imide), polyetherimide, atactic polystyrene, polycarbonate, polymethacrylate (e.g., polyisobutyl methacrylate, polypropylmethacrylate, polyethylmethacrylate, and polymethylmethacrylate), polyacrylate (e.g., polybutylacrylate and polymethylacrylate), syndiotactic polystyrene (sPS), syndiotactic poly-alpha-methyl styrene, syndiotactic polydichlorostyrene, copolymers and mixtures formed of any of these polystyrenes, cellulose derivatives (e.g., ethyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, and nitrocellulose), polyalkylidene polymers (e.g., polyethylene, polypropylene, polybutene, polyisobutylene, and poly(<NUM>-methyl)pentene), fluorinated polymers (e.g., perfluoroalkoxy resin, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, polyvinylidene fluoride, and polychlorotrifluoroethylene), chlorinated polymers (e.g., polyvinylidene chloride, and polyvinylchloride), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, silicone resin, epoxy resin, polyvinylacetate, polyether-amide, ionomeric resin, elastomers (e.g., polybutadiene, polyisoprene, and neoprene), and polyurethane.

Other materials comprised by the polymer film as the infrared light cut-off film <NUM> may comprise, for example, coPEN, that is, copolymers of PEN (for example, copolymers of <NUM>,<NUM>-, <NUM>,<NUM>-, <NUM>,<NUM>-, <NUM>,<NUM>- and/or <NUM>,<NUM>-naphthalene dicarboxylic acid or esters thereof, with (a) terephthalic acid or esters thereof, (b) isophthalic acid or esters thereof, (c) phthalic acid or esters thereof, (d) alkanediol, (e) cycloalkane glycol (e.g., cyclohexane dimethanol diol), (f) alkanedicarboxylic acid, and/or (g) cycloalkane dicarboxylic acid (e.g., cyclohexane dicarboxylic acid), copolymers of polyalkylene terephthalate (e.g., copolymers of terephthalic acid, or esters thereof, with (a) naphthalene dicarboxylic acid or esters thereof, (b) isophthalic acid or esters thereof, (c) phthalic acid or esters thereof, (d) alkanediol, (e) cycloalkane glycol (e.g., cyclohexane dimethanol diol), (f) alkanedicarboxylic acid, and/or (g) cycloalkane dicarboxylic acid (e.g., cyclohexane dicarboxylic acid), styrene copolymers (e.g., styrene-butadiene copolymers and styrene-acrylonitrile copolymers), and copolymers of <NUM>,<NUM>'-dibenzoic acid and ethylene glycol.

The polymer films of the infrared light cut-off film <NUM> may each contain a mixture of two or more of the above polymers or copolymers, for example, a mixture of sPS and atactic polystyrene. Moreover, the coPEN may be a mixture of particles, in which at least one component is a polymer using naphthalene dicarboxylic acid as a base material, and other components may be other polyesters or polycarbonates such as PET, PEN, or coPEN.

The PEN is preferable as a material comprised by the polymer film of the infrared light cut-off film <NUM>, and is thermally stable from about <NUM> to about <NUM>. In addition to the PEN, preferred materials may include, for example, polybutylene naphthalate and other crystalline naphthalene dicarboxylic polyesters.

In the polymer film of the infrared light cut-off film <NUM>, a small amount of comonomer can be substituted into the naphthalene dicarboxylic polyester within a range in which the refractive index thereof is not substantially changed. Preferred monomers may include substances based on isophthalic acid, azelaic acid, adipic acid, sebacic acid, dibenzoic acid, terephthalic acid, <NUM>,<NUM>-naphthalene dicarboxylic acid, and <NUM>,<NUM>-naphthalene dicarboxylic acid, or cyclohexane dicarboxylic acid. It should be noted that, when a small amount of comonomer is substituted into the naphthalene dicarboxylic polyester, the refractive index may be reduced. However, even if the refractive index is reduced, it can be compensated by any of adhering to a polymer layer, reducing the extrusion temperature during film manufacturing, optimizing matching of melt viscosity, and optimizing matching of the glass transition temperature for film stretching during film manufacturing.

In concern with reasons of the thickness, flexibility, and economical efficiency of the multi-layer polymer film, the number of layers comprised in the multi-layer polymer film is selected such that the desired optical property is implemented with the minimum number of layers. The number of layers is preferably less than about <NUM>, more preferably less than about <NUM>, and even more preferably less than about <NUM>.

For the infrared light cut-off film <NUM>, in the manufacturing process thereof, it can be formed by simultaneously extruding the polymer material comprised in respective film of single-layer and multi-layer polymer films. In the manufacturing process of the film, the film is then subjected to an orientation process by stretching at a specified temperature to form a film having a desired thickness. As desired, a heat-curing process may sometimes be performed at a specified temperature. The extrusion process and the orientation process can be performed simultaneously.

Moreover, as a method of stacking polymer films, each of the films can be fixedly stacked using an adhesive. Specifically, for example, a pressure-sensitive adhesive, a hot-melt adhesive, an active energy ray-curable adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic adhesive, and the like can be used. The type thereof can be appropriately determined according to the material and the like of each polymer film. For example, acrylic-based, vinyl alcohol-based, silicone-based, polyester-based, polyurethane-based, polyether-based adhesives can be used, and adhesives with high transparency can be used. These adhesives may be directly coated to a surface of each polymer film, or a layer of an adhesive tape, a sheet or the like made of an adhesive may also be adhered to a whole or a part of a surface of the polymer film. Moreover, as a method of stacking polymer films, a frame that can at least partially surround an end of each polymer film may be prepared, and a plurality of polymer films may be overlapped and fixedly arranged by using the frame.

As shown in <FIG>, the infrared light cut-off portion <NUM> further comprises an infrared light reduction layer <NUM> as desired. The infrared light reduction layer <NUM> reduces the transmission amount of the infrared light by at least one of reflection and absorption. The infrared light cut-off layer <NUM> has an upper surface 22a and a lower surface 22b, and the infrared light reduction layer <NUM> is provided, for example, on the upper surface 22a of the infrared light cut-off layer <NUM>. The infrared light cut-off layer <NUM> may be located between the infrared light reduction layer <NUM> and the substrate <NUM>. In the infrared light cut-off portion <NUM>, the infrared light reduction layer <NUM> may be provided, for example, on the lower surface 22b of the infrared light cut-off layer <NUM> as desired. The infrared light reduction layer <NUM> may also be provided, for example, on both the upper surface 22a and the lower surface 22b of the infrared light cut-off layer <NUM> as desired. Regardless of the configuration, the infrared light reduction layer <NUM> can reduce the transmission amount of the infrared light.

The infrared light reduction layer <NUM> comprises, for example, a metal, a metal alloy, or an oxide semiconductor, and mainly reflects light in a near-infrared region with a wavelength of <NUM> or more and an infrared region. For example, the metal may include silver, gold, copper, or aluminum. Silver is a particularly preferred metal because it can be easily formed into a thin film shape and can easily reflect light in the near-infrared region and the infrared region. The metal alloy comprises a silver alloy, a stainless steel, or inconel. Among the metal alloys, a silver alloy containing at least <NUM>% silver by weight is a particularly preferred material because it is easy to produce a thin film and it is easy to reflect light in the near-infrared region and the infrared region. A silver alloy containing silver, less than <NUM>% gold by mass, and/or less than <NUM>% copper by mass is also excellent in terms of durability, and is therefore a preferred material. For example, the oxide semiconductor preferably comprises tin dioxide (SnO<NUM>), zinc oxide (ZnO), indium tin oxide (ITO), or antimony tin oxide (ATO). The metal, the metal alloy, or the oxide semiconductor may be formed into a single layer, or may be formed into a plurality of layers.

The infrared light reduction layer <NUM> is formed by, for example, thermal decomposition, powder coating, evaporation, cathode sputtering, ion plating, or the like, and the metal, the oxide semiconductor, or the metal alloy is formed on a polymer film. From the viewpoint of obtaining a uniform film structure and thickness, cathode sputtering and ion plating are preferred manufacturing methods. The infrared light reduction layer <NUM> may be another metallized polymer or a glass sheet laminated to a multi-layer polymer film using an adhesive. The adhesive comprises, for example, a hot-melt adhesive or a pressure-sensitive adhesive. The hot-melt adhesive is, for example, a VITEL <NUM> adhesive manufactured by Shell Chemicals Company (Ohio, USA), and the pressure-sensitive adhesive is, for example, an acrylic-based adhesive of <NUM>/<NUM> IOA/AA and <NUM>/<NUM> IOA/acrylamide manufactured by <NUM> Company (Minnesota, USA).

The metal and the metal alloy may be coated to a thickness of about <NUM> to about <NUM>, and preferably coated to a thickness of about <NUM> to about <NUM>. The oxide semiconductor layer may be coated to a thickness of about <NUM> to about <NUM>, and preferably coated to a thickness of about <NUM> to about <NUM>. When the infrared light reduction layer <NUM> is a metallized polymer or glass sheet laminated on a multi-layer polymer film, the coating thickness of the metal or metal alloy on the sheet is, for example, about <NUM> to about <NUM>, and the coating thickness of the oxide semiconductor on the sheet is, for example, about <NUM> to about200 nm.

The infrared light cut-off portion <NUM> of the present implementation may include the infrared light reduction layer <NUM>, and therefore, the incident amount of the infrared light to the display portion <NUM> can be further reduced. On the other hand, the infrared light cut-off portion <NUM> transmits the visible light having the display information, and thus maintains the brightness of the display information.

As shown in <FIG>, the infrared light cut-off portion <NUM> further comprises an ultra-violet light cut-off layer <NUM> as desired. The ultra-violet light cut-off layer <NUM> reduces the transmission amount of ultra-violet light. The ultra-violet light cut-off layer <NUM> is provided, for example, below the lower surface 22b of the infrared light cut-off layer <NUM>, and may be located between the infrared light reduction layer <NUM> and the substrate <NUM>. In the infrared light cut-off portion <NUM>, the ultra-violet light cut-off layer <NUM> may be provided, for example, on the upper surface 21a of the infrared light cut-off layer <NUM>. The ultra-violet light cut-off layer <NUM> may be provided, for example, on both the upper surface 22a and the lower surface 22b of the infrared light cut-off layer <NUM> as desired. Regardless of the configuration, the ultra-violet light cut-off layer <NUM> can reduce the transmission amount of the ultra-violet light.

The ultra-violet light cut-off layer <NUM> may have transmissivity in a visible light region. According to the display device <NUM>, the infrared light cut-off portion <NUM> further comprises the ultra-violet light cut-off layer <NUM>, and therefore, the ultra-violet light comprised in sunlight or the like is prevented from being irradiated to the display portion <NUM>. Moreover, the ultra-violet light cut-off layer has transmissivity in the visible light region, and therefore, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion <NUM> will be maintained. In the display device <NUM>, the transmissivity may have a transmittance greater than <NUM>% in the visible light region. According to the display device <NUM>, the brightness of the display information comprised by the visible light passing through the infrared light cut-off portion <NUM> will be further maintained.

In the display device <NUM>, the ultra-violet light cut-off layer <NUM> may be an adhesive layer. According to the display device <NUM>, the ultra-violet light cut-off layer may be an adhesive layer, and therefore, the ultra-violet light can be effectively cut off, and the ultra-violet light cut-off layer <NUM> can be stacked to, for example, the infrared light cut-off layer <NUM> through its adhesiveness.

The adhesive layer comprises, for example, a benzophenone-based ultraviolet absorber, a salicylic acid-based ultraviolet absorber, a cyanoacrylate-based ultraviolet absorber, or a benzotriazole-based ultraviolet absorber. For example, the benzophenone-based ultraviolet absorber may comprise <NUM>,<NUM>-dihydroxybenzophenone, <NUM>-hydroxy-<NUM>-methoxybenzophenone, <NUM>-hydroxy-<NUM>-dodecyloxy benzophenone, <NUM>-hydroxy-<NUM>-methoxybenzophenone, <NUM>,<NUM>'-dihydroxy-<NUM>-methoxybenzophenone, <NUM>,<NUM>'-dihydroxy-<NUM>,<NUM>'-methoxybenzophenone, <NUM>-hydroxy-<NUM>-methoxy-<NUM>-sulfone benzophenone, or bis(<NUM>-methoxy-<NUM>-hydroxy-<NUM>-benzoyl phenylmethane). For example, the salicylic acid-based ultraviolet absorber may comprise phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate. For example, the cyanoacrylate-based ultraviolet absorber may comprise <NUM>-ethylhexyl-<NUM>-cyano-<NUM>,<NUM>'-diphenylacrylate and ethyl-<NUM>-cyano-<NUM>,<NUM>'-diphenylacrylate. For example, the benzotriazole-based ultraviolet absorber may comprise <NUM>-(<NUM>'-hydroxy-<NUM>'-methylphenyl) benzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>'-tert-butylphenyl) benzotriazole, <NUM>-(<NUM>'-hydroxy <NUM>',<NUM>'-di-tert-butylphenyl) benzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>'-tert-butyl-<NUM>'-methylphenyl)-<NUM>-chlorobenzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>',<NUM>'di-tert-butylphenyl)-<NUM>-chlorobenzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>',<NUM>'-di-tert-aminophenyl) benzotriazole, <NUM>-{<NUM>'-hydroxy-<NUM>'-(<NUM>",<NUM>",<NUM>",<NUM>"-tetrahydrophthalimidemethyl)-<NUM>'-methylphenyl} benzotriazole, or <NUM>,<NUM>-methylenebis{<NUM>-(<NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl)-<NUM>-(<NUM>-benzotriazol-<NUM>-yl)phenol. Among these ultraviolet absorbers, the benzotriazole-based ultraviolet absorber is used preferably.

These ultraviolet absorbers are contained, for example, in a quantity ranging from <NUM> parts by mass to <NUM> parts by mass with respect to <NUM> parts by mass of the acrylic-based adhesive. The content of the ultraviolet absorber is <NUM> parts by mass or more, whereby the effect of suppressing transmission of ultraviolet rays can be improved. The content of the ultraviolet absorber is <NUM> parts by mass or less, whereby it can be uniformly dispersed in the acrylic-based adhesive, and the transparency in the visible light region can be further improved. These ultraviolet absorbers are more preferably contained, for example, in a quantity ranging from <NUM> part by mass to <NUM> parts by mass with respect to <NUM> parts by mass of the acrylic-based adhesive.

The thickness of the adhesive layer ranges, for example, from <NUM> to <NUM>, and preferably from <NUM> to <NUM>. By having a thickness in the range, the adhesive layer can obtain the required adhesive force more reliably, and can suppress an increase in cost.

As shown in <FIG>, the infrared light cut-off portion <NUM> further comprises a hard coating <NUM> as desired. The infrared light reduction layer <NUM> may comprise a hard coat function. The hard coating <NUM> is provided, for example, below the lower surface 21b of the substrate <NUM>. The hard coating <NUM> may be provided, for example, on an upper surface 23a of the infrared light reduction layer <NUM> as desired. The hard coating <NUM> may be provided, for example, both above the upper surface 23a of the infrared light reduction layer <NUM> and under the lower surface 21b of the substrate <NUM> as desired. The hard coating <NUM> can constitute at least one layer of the uppermost layer and the lowermost layer of the infrared light cut-off portion <NUM>. Regardless of the configuration, the hard coating <NUM> can protect the infrared light cut-off portion <NUM>. Moreover, the hard coating <NUM> can increase the mechanical strength of the infrared light cut-off portion <NUM>.

The hard coating <NUM> comprises, for example, a binder and nanoparticles dispersed in the binder. The binder is, for example, a methacrylic oligomer and/or monomer, and the content of the binder is, for example, <NUM>% to <NUM>% by mass. The content of the nanoparticles in the binder is, for example, <NUM>% to <NUM>% by mass. Among the nanoparticles in the binder, <NUM>% to <NUM>% by mass of the nanoparticles (first nanoparticles) have, for example, particle diameters of <NUM> to <NUM>. Moreover, <NUM>% to <NUM>% by mass of the nanoparticles (second nanoparticles) have, for example, particle diameters of <NUM> to <NUM>. The ratio of the particle diameters of the nanoparticles to the particle diameters of the first nanoparticles is <NUM> to <NUM>.

The hard coating <NUM> can be formed by a measuring coating method such as a wire bar method, a notch bar method, and a screen printing method.

According to the display device <NUM>, the infrared light cut-off portion <NUM> may comprise the hard coating <NUM>, and therefore, the mechanical strength of the infrared light cut-off portion <NUM> is increased, and the resistance to scratches and the like is increased.

Then, the relationship between the infrared light cut-off portion <NUM> and the visible light L2 of the linearly polarized wave incident to the infrared light cut-off portion <NUM> of the display device <NUM> of the present implementation is described with reference to <FIG> is an illustrative view showing an orientation of the vibration direction PL1 of the visible light L2 incident to the infrared light cut-off portion <NUM>. Moreover, <FIG> is an enlarged view showing the relationship between the vibration direction PL1 of the visible light L2 and the slow axis SA1 of the infrared light cut-off portion <NUM>.

The infrared light cut-off portion <NUM> comprises the infrared light cut-off layer <NUM> consisting of the infrared light cut-off film <NUM>, and the infrared light cut-off layer <NUM> has the slow axis SA1. The visible light L2 is a linearly polarized wave having the display information from the display portion <NUM>, and the linearly polarized wave of the visible light L2 has the vibration direction PL1. The vibration direction PL1 of the visible light L2 incident to the infrared light cut-off portion <NUM> forms a certain angle, i.e., an angle TH1, with the slow axis SA1.

In a case where the vibration direction PL1 of the visible light L2 cannot be said to be generally parallel to the slow axis SA1, in an example not according to the claimed invention, for example, in a case where the angle TH1 is about <NUM> degrees, the vibration direction PL1 of the linearly polarized wave of the visible light L2 is allowed to change. This is because, in the infrared light cut-off film <NUM>, due to the one-dimensional molecular structure of the polymers contained therein, the refractive index in the direction along the slow axis SA1 is significantly different from the refractive index in the direction perpendicular to the slow axis SA1. The visible light L2 of the linearly polarized wave experiences both the refractive index in the direction of the slow axis SA1 and the refractive index in the direction perpendicular to the slow axis SA1. Due to these two different refractive indices, birefringence occurs in the infrared light cut-off portion <NUM> including the infrared light cut-off film <NUM>. As a result, when the visible light L2 of the linearly polarized wave is transmitted from the infrared light cut-off portion <NUM>, the linearly polarized wave of the visible light L2 may sometimes be changed into an elliptically polarized wave.

In contrast, in a case where the vibration direction PL1 of the visible light L2 is generally parallel to the slow axis SA1, in an example according to the claimed invention, that is, in a case where the angle TH1 is <NUM> degree or close to <NUM> degree, the vibration direction PL1 of the linearly polarized wave of the visible light L2 is not allowed to change, and the linearly polarized wave can be maintained. This is because the visible light L2 of the linearly polarized wave only experiences the refractive index in the direction generally along the slow axis SA1. It should be noted that when the angle TH1 is generally <NUM> degrees or close to <NUM> degrees, that is, when approximately perpendicular, the vibration direction PL <NUM> of the linearly polarized wave of the visible light L2 is not allowed to change either. This is because the visible light L2 of the linearly polarized wave can only experience the refractive index in a direction generally perpendicular to the slow axis SA1.

Here, for example, it is assumed that a rotation center line RT1 coaxial with the vibration direction PL1 is taken as a central axis to rotate the infrared light cut-off portion <NUM>, so that the incidence angle of the visible light L2 with respect to the infrared light cut-off portion <NUM> is changed. In the case, if the slow axis SA1 of the infrared light cut-off portion <NUM> is generally parallel to the vibration direction of the linearly polarized wave of the visible light L2, the linearly polarized wave of the visible light L2 can be maintained. This is because, even if the incidence angle is changed, the linearly polarized wave of the visible light L2 can continuously experience generally the same refractive index in the one-dimensional axial direction of the polymers in the infrared light cut-off portion <NUM>, that is, along the slow axis SA1.

If further supplemented, when the vibration direction PL <NUM> of the linearly polarized wave of the visible light L2 is generally perpendicular to the slow axis SA <NUM> of the infrared light cut-off portion <NUM>, in an example not according to the claimed invention, if the incidence angle of the visible light L2 with respect to the infrared light cut-off portion <NUM> is changed, the linearly polarized wave of the visible light L2 cannot be maintained. This is because, in a case where the incidence angle is changed, the one-dimensional axial direction of the polymers in the infrared light cut-off portion <NUM> is changed to be different from the vibration direction PL1 of the visible light L2. Therefore, the linearly polarized wave of the visible light L2 causes optical rotation due to one-dimensional molecular structures of the polymers.

Then, with reference to <FIG>, an incidence angle when the visible light L2 is incident to the infrared light cut-off portion <NUM> and influence thereof are described. <FIG> is an illustrative view showing a scheme in which the infrared light cut-off portion <NUM> is configured so that the incidence angle NA <NUM> of the visible light L2 is <NUM> degree, that is, the light is incident vertically. Moreover, <FIG> is an illustrative view showing a scheme in which the infrared light cut-off portion <NUM> is configured such that the incidence angle NA <NUM> of the visible light L2 is greater than <NUM> degree and less than <NUM> degrees, that is, a scheme in which the infrared light cut-off portion <NUM> is configured obliquely with respect to the visible light L2. Then, a reference method is assumed in <FIG>, and the present implementation is assumed in <FIG>.

The visible light L2 from the display portion <NUM> is incident to the infrared light cut-off portion <NUM>, and a part of the incident visible light L2 is transmitted from the infrared light cut-off portion <NUM> to become the visible light L3. Moreover, an external light SL1 such as the sunlight is incident to the infrared light cut-off portion <NUM>, and a part of the incident light SL1 is reflected by the infrared light cut-off portion <NUM> and becomes a reflected light SL2. It should be noted that, in <FIG>, it is assumed that the external light SL1 and the visible light L2 are at the same light path timing.

As shown in <FIG>, in a case where the visible light L2 is incident vertically to the infrared light cut-off portion <NUM>, the reflected light SL2 of the sunlight and the like, that is, the reflected light SL2 generated by the external light SL1 reflected by the infrared light cut-off portion <NUM> has generally the same light path as that of the visible light L3 transmitted from the infrared light cut-off portion <NUM>. As a result, the reflected light SL2 of the external light SL <NUM> together with the visible light L3 proceeds towards eyes of the visual confirmer D <NUM> such as the driver.

On the other hand, as shown in <FIG>, the infrared light cut-off portion <NUM> according to the present implementation is configured obliquely with respect to the visible light L2, and the reflected light SL3 of the sunlight and the like has a light path different from that of the visible light L3 transmitted from the infrared light cut-off portion <NUM>. That is, according to the display device <NUM> of the present implementation, it is easy to adjust an orientation of the infrared light cut-off portion <NUM> with respect to the light path of the visible light L2 so that a part of the external light SL <NUM>, after reflected by the infrared light cut-off portion <NUM>, does not proceed towards the eyes of the visual confirmer D <NUM> such as the driver.

As described above, according to the display device <NUM> of the present implementation of the claimed invention, the infrared light cut-off layer <NUM> comprised in the infrared light cut-off portion <NUM> has the slow axis SA1, and the slow axis SA1 is generally parallel to the vibration direction PL1 of the linearly polarized wave. Therefore, compared with a scheme not according to the claimed invention in which the slow axis SA1 is not generally parallel to the vibration direction PL <NUM> of the linearly polarized wave, a ratio of changing the visible light L2 of the linearly polarized wave into the elliptical polarized wave after being transmitted from the infrared light cut-off portion <NUM> is reduced. As a result, a visual confirmer D <NUM> such as a driver of a vehicle can easily recognize the display information comprised by the visible light L2 emitted from the display portion <NUM> as described above, and the visual confirmation of the display information will be maintained.

In the present implementation of the claimed invention, the slow axis SA1 being generally parallel to the vibration direction PL <NUM> of the linearly polarized wave of the visible light L2 may be defined as that: the angle TH1 formed by the slow axis SA1 and the vibration direction PL1 of the linearly polarized wave ranges from <NUM> degree to <NUM> degrees. As a supplement, the concept of "generally parallel" also comprises that the angle TH1 is <NUM> degree, that is, being parallel, and also comprises, for example, being substantially parallel with the angle TH1 ranges from <NUM> degree to <NUM> degrees.

According to the display device <NUM>, after visible light from the display portion <NUM> is transmitted from the infrared light cut-off portion <NUM> including the infrared light cut-off layer <NUM>, the ratio of changing the linearly polarized wave of the visible light L2 into the elliptically polarized wave is further reduced. As a result, a visual confirmer who recognizes the visible light L2 reflected by the reflecting portion <NUM> can recognize similar display information by the display information of the visible light emitted from the display portion.

In the present implementation, when the angle TH1 formed by the slow axis SA1 and the vibration direction PL1 of the linearly polarized wave ranges from <NUM> degree to <NUM> degrees, for example, for an infrared light cut-off film <NUM> having a generally rectangular two-dimensional shape, the maximum length as one side of the rectangle may be allowed to be up to <NUM>.

Hereinafter, the display device <NUM> is further described through embodiments of the present disclosure and comparative examples. The present disclosure is not limited to the following examples.

A multi-layer stretched polymer film including a polyester film is prepared, and a direction of a slow axis for the multi-layer stretched polymer film (<NUM>™ scotchtint™ window film multi-layer NANO80S, manufactured by <NUM> Japan Corporation) is measured. A phase difference measuring device KOBRA (manufactured by Oji Scientific Instruments Co. ) is used in the measurement of the direction of the slow axis. Based on the measurement result of the direction of the slow axis, the multi-layer infrared light cut-off film is cut out from a central region of the multi-layer stretched polymer film. The two-dimensional shape of the multi-layer infrared light cut-off film has long sides and short sides generally perpendicular to the long sides. The long side of the multi-layer infrared light cut-off film is generally parallel to the CD direction of the multi-layer stretched polymer film, that is, the direction of a first axis. In the present implementation, the length of the long side is set to <NUM>, and the length of the short side is set to <NUM>. Moreover, an angle formed by the direction of the slow axis and the direction of the long side of the cut film is <NUM> degrees or less.

In the present implementation, an infrared light cut-off portion comprising sequentially an ultra-violet light cut-off layer having an adhesive function, an infrared light cut-off layer, and an infrared light reduction layer having a hard coat function is manufactured. For the hard coating, a three-dimensionally crosslinked acrylic resin is used and adhered to a window portion via the ultra-violet light cut-off layer. For the window portion, polycarbonate having isotropy in an optical plane is used. The thickness of the window portion is set to <NUM>. For the ultra-violet light cut-off layer, an acrylic pressure-sensitive adhesive tape (PSA) is used. For the infrared light cut-off layer, a multi-layer infrared light cut-off film is used. The thickness of the multi-layer infrared light cut-off film is set to <NUM>. The infrared light reduction layer is made of antimony tin oxide (ATO) powder. The thickness of the infrared light reduction layer is set to <NUM>.

<FIG> are schematic views showing measurement systems that determine a polarization state of a visible light of a linearly polarized wave passing through the infrared light cut-off portion. In the measurement system, in <FIG>, a white liquid crystal display that emits the linearly polarized wave is used as the display portion 10p, and float plate glass FG is used as the reflecting portion 30p. Visible light L2p from the display portion 10p comprises display information. The float plate glass FG is generally transparent in the visible light region, and its thickness is about <NUM>. An incidence angle AGp of the visible light L2p to the reflecting portion 30p is about <NUM> degrees. In the configurations shown in <FIG>, in a position equivalent to the driver, a measurer D1p can observe the reflecting portion 30p by visual inspection on the front side thereof.

In the present embodiment, the visible light L2p of the linearly polarized wave is emitted from the display portion 10p towards the infrared light cut-off portion 20p. The polarization direction of the emitted visible light L2p is generally along the long side of the infrared light cut-off portion 20p, and a slow axis of the infrared light cut-off portion 20p is set to be generally parallel to the vibration direction of the linearly polarized wave of the visible light L2p. Specifically, an angle THlp formed by the slow axis of the infrared light cut-off portion 20p and the vibration direction of the linearly polarized wave of the visible light L2p is <NUM> degree on the average of the entire infrared light cut-off portion 20p.

<FIG> is a view showing a measurement system in which the visible light is incident vertically to the infrared light cut-off portion 20p, and <FIG> is a view showing a measurement system in which the visible light is incident to the infrared light cut-off portion 20p at an incidence angle NA1p. In the present embodiment, the polarization state is measured using both the measurement systems of <FIG>. In the measurement system of <FIG>, the incidence angle NA1p is set to <NUM> degrees. The measurement system of <FIG> corresponds to the measurement system of <FIG> when the incidence angle NA1p of the visible light L2p in the measurement system is <NUM> degree.

In the present embodiment, the measurement systems shown in <FIG> are used to observe the polarization state of the visible light L4p of the linearly polarized wave passing through the infrared light cut-off portion 20p. When it is observed by the measurer D1p that the visible light L4p reflected by the float plate glass FG comprises display information of which the degree of coloration cannot be confirmed, it is evaluated as "A (good). " When it is observed by the measurer D1p that the visible light L4 comprises colored display information such as an iridescent rainbow pattern, it is evaluated as "B (poor).

<FIG> is an enlarged view showing a relationship between the slow axis SAlp of the infrared light cut-off film 60p and the vibration direction PL1p of the visible light L2 in the present embodiment. The infrared light cut-off film 60p according to the present embodiment is cut out from the central region of the stretched polymer film, and its long side 62p is generally parallel to the CD direction of the stretched polymer film <NUM>. In the present embodiment, an average value of the angle TH1p formed by the direction of the slow axis SA1p and the vibration direction PLlp of the incident visible light L2 is <NUM> degree.

In the present comparative example, a multi-layer stretched polymer film is prepared in the same manner as in Embodiment <NUM>, and a multi-layer infrared light cut-off film is cut out from a central region of the multi-layer stretched polymer film. The two-dimensional shape of the multi-layer infrared light cut-off film of this comparative example has long sides and short sides generally perpendicular to the long sides. The long side of the multi-layer infrared light cut-off film is set to be generally parallel to the MD direction of the multi-layer stretched polymer film.

In this comparative example not according to the claimed invention, the polarization state of the visible light L4p of the linearly polarized wave passing through the infrared light cut-off portion 20p is observed in the same manner as in Embodiment <NUM>. In this comparative example, the visible light L2p of the linearly polarized wave is emitted from the display portion 10p towards the infrared light cut-off portion 20p. The polarization direction of the emitted visible light L2p is generally parallel to the long side of the infrared light cut-off portion 20p, and the slow axis of the infrared light cut-off portion 20p is set to be generally perpendicular to the vibration direction of the linearly polarized wave of the visible light L2p. Specifically, an angle formed by the slow axis of the infrared light cut-off portion 20p and the vibration direction of the linearly polarized wave of the visible light L2p is <NUM> degrees on the average of the entire infrared light cut-off portion 20p.

<FIG> is an enlarged view showing a relationship between the slow axis SAlq of the infrared light cut-off film 60q and the vibration direction PLlq of the visible light L2 in this comparative example. In this comparative example, an average value of the angle TH1q formed by the direction of the slow axis SAlq and the vibration direction PLlq of the incident visible light L2 is <NUM> degrees.

A multi-layer stretched polymer film comprising a polyester film is prepared. In this comparative example, an infrared light cut-off film is cut out from a peripheral region of the multi-layer stretched polymer film, and the two-dimensional shape of the infrared light cut-off film is set to be a generally rectangle having long sides and short sides generally perpendicular to the long sides. In this comparative example, the length of the long side is set to <NUM>, and the length of the short side is set to <NUM>.

In this comparative example not according to the claimed invention, the infrared light cut-off film is cut in a manner that the long side is in the MD direction. The short side of the infrared light cut-off film of this comparative example is generally parallel to the CD direction, i.e., the direction of a first axis. An angle formed by the direction of the slow axis and the direction of the long side of the cut film is <NUM> degrees.

In addition to the usage of the multi-layer infrared light cut-off film manufactured in this comparative example, an infrared light cut-off portion is manufactured in the same manner as in Embodiment <NUM>. The thickness of the multi-layer infrared light cut-off film is set to <NUM>.

In this comparative example, the polarization state of the visible light L4p of the linearly polarized wave passing through the infrared light cut-off portion 20p is observed in the same manner as in Embodiment <NUM>.

In this comparative example, the visible light L2p of the linearly polarized wave is emitted from the display portion 10p towards the infrared light cut-off portion 20p. The polarization direction of the emitted visible light L2p is generally parallel to the long side of the infrared light cut-off portion 20p. The angle formed by the slow axis of the infrared light cut-off portion 20p and the vibration direction of the linearly polarized wave of the visible light L2p is <NUM> degrees on the average of the entire infrared light cut-off portion 20p.

<FIG> is an enlarged view showing a relationship between the slow axis SA1r of the infrared light cut-off film 70r and the vibration direction PL1r of the visible light L2 in this comparative example. In this comparative example, an average value of the angle TH1r formed by the direction of the slow axis SAlr and the vibration direction PLlr of the incident visible light L2 is <NUM> degrees.

Table <NUM> is a table which summarizes measurement results of the infrared light cut-off layer, the direction of the slow axis, and the polarization state of Embodiment <NUM>, Comparative Example <NUM>, and Comparative Example <NUM>. In Embodiment <NUM> and Comparative Example <NUM> in Table <NUM>, the "stretched film" indicates that their infrared light cut-off portion comprises an infrared light cut-off layer made of a stretched polymer film. In Comparative Example <NUM> in Table <NUM>, the "stretched film/non-stretched film" indicates that the infrared light cut-off portion of Comparative Example <NUM> comprises an infrared light cut-off layer formed by overlapping an infrared light cut-off portion preparation body of Comparative Example <NUM> on a lamination body over the infrared light cut-off portion of Embodiment <NUM>. In Table <NUM>, the "formed angle (average)" indicates an average of the angle formed by the slow axis of the infrared light cut-off portion and the vibration direction of the linearly polarized wave of the visible light. In Table <NUM>, the "incident vertically" indicates a measurement result of the polarization state using the measurement system of <FIG>, and the "incident obliquely" indicates a measurement result of the polarization state using the measurement system of <FIG>.

Claim 1:
A display device (<NUM>), wherein the display device comprises:
a display portion (<NUM>) emitting a visible light (L2) of a linearly polarized wave having display information;
an infrared light cut-off portion (<NUM>) transmitting the visible light from the display portion and reducing an incident amount of an infrared light to the display portion (<NUM>); and
a reflecting portion (<NUM>) reflecting the visible light transmitted through the infrared light cut-off portion (<NUM>),
wherein the infrared light cut-off portion (<NUM>) comprises an infrared light cut-off layer (<NUM>),
the infrared light cut-off layer (<NUM>) has a slow axis (SA1), and
the slow axis (SA1) is generally parallel to a vibration direction (PL1) of the linearly polarized wave.