JP2019012211A - Half-mirror for projected image display, windshield glass and head-up display system - Google Patents

Abstract

To provide a half-mirror for a projected image display which gives a projected image of high luminance without reducing the visible light transmission of windshield glass; the windshield glass whose visible light transmission is high and has a projected image display site for giving the projected image of high luminance; and a head-up display system capable of performing the projected image display of high luminance.SOLUTION: Disclosed is a half-mirror for the projected image display which includes a selective reflection layer for reflecting light in a wavelength selective manner and in which the selective reflection center wavelength of a selective reflection layer is 650 to 780 nm, having the selective reflection center wavelength in the shortest wavelength in a visible light wavelength region in the half-mirror. A windshield glass including the half-mirror for the projected image display and a head-up display system including the windshield glass are provided.SELECTED DRAWING: None

Description

  The present invention relates to a half mirror for displaying projected images. More specifically, the present invention relates to a half mirror for displaying projected images that can be used as a combiner in a head-up display system. The present invention also relates to a windshield glass including the projected image display half mirror and a head-up display system using the projected image display half mirror.

  The windshield glass can be used as a projection image display member of a head-up display system by forming a projection image display portion using a half mirror film. Patent Document 1 discloses that a half mirror film including a retardation layer and a plurality of cholesteric liquid crystal layers is used as a projection image display member. Patent Document 1 describes that a half mirror film is provided in an intermediate layer in a windshield glass having a laminated glass structure.

WO2016 / 052367

  In general, a glass that absorbs a large amount of infrared light is used for the windshield glass in order to provide a heat shielding effect. Many of the laminated glasses using such glass have a low visible light transmittance of 73%, 76% and the like. Therefore, as described in Patent Document 1, in a portion where the half mirror film is provided, the visible light transmittance required for the windshield glass of the vehicle may not satisfy the standard of 70% or more.

  It is an object of the present invention to provide a projection image display half mirror that provides a high-intensity projection image without reducing the visible light transmittance of the windshield glass when a windshield glass is produced in combination with glass. Another object of the present invention is to provide a windshield glass having a projected image display portion that has a high visible light transmittance and gives a projected image with high brightness. It is another object of the present invention to provide a head-up display system capable of displaying a projected image with high brightness.

  In the process of intensive studies to solve the above problems, the inventor has selected a wavelength range that has little influence on the visible light transmittance as the wavelength range of light reflected at the projected image display site. It was found that a projected image with brightness could be obtained. The present inventors have further studied based on this finding and completed the present invention.

That is, the present invention provides the following [1] to [13].
[1] A half mirror for displaying a projected image,
A selective reflection layer that reflects light in a wavelength-selective manner;
The half mirror for displaying projected images, wherein the selective reflection layer of the selective reflection layer having the selective reflection center wavelength at the shortest wavelength in the visible light wavelength range is 650 to 780 nm.
[2] The half mirror for displaying projected images according to [1], wherein the selective reflection layer is a cholesteric liquid crystal layer.
[3] including two or more cholesteric liquid crystal layers,
The half mirror for projecting image display according to [2], wherein the two or more cholesteric liquid crystal layers have the same spiral twisting direction.
[4] including a retardation layer,
The projected image display half mirror according to [2] or [3], wherein the retardation layer has a front phase difference of 250 nm to 450 nm, or 50 nm to 180 nm.
[5] The projected image display half mirror according to [1], wherein the selective reflection layer is a linearly polarized light reflection layer.
[6] A windshield glass including the half mirror for displaying projected images according to any one of [1] to [5].
[7] A windshield glass including the half mirror for displaying projected images according to [4],
From the viewing side, including the projected image display part in which the retardation layer and the circularly polarized reflection layer are arranged in this order,
The front retardation of the retardation layer is 250 nm to 450 nm,
The windshield glass in which the slow axis direction of the retardation layer is in the range of + 30 ° to + 85 ° or −30 ° to −85 ° when the vertical direction of the windshield glass is 0 °.

[8] A windshield glass including the half mirror for displaying projected images according to [4],
From the viewing side, including the projected image display part in which the retardation layer and the circularly polarized reflection layer are arranged in this order,
The front phase difference of the retardation layer is 50 nm to 180 nm,
The windshield glass in which the slow axis direction of the retardation layer is in the range of + 120 ° to + 175 ° or −120 ° to −175 ° when the vertical direction of the windshield glass is 0 °.
[9] including a first glass plate, a second glass plate, and an intermediate layer between the first glass plate and the second glass plate, and at least a part of the intermediate layer includes the projected image display half The windshield glass according to any one of [6] to [8], including a mirror.
[10] A head-up display system including the windshield glass according to any one of [6] to [9],
Incident light for projected image display is incident on the half mirror for projected image display,
A head-up display system in which the incident light is p-polarized light that vibrates in a direction parallel to the incident surface.
[11] A head-up display system comprising the windshield glass according to [7] or [8],
Incident light for projected image display is incident on the half mirror for projected image display,
The retardation layer is disposed on the incident side of the incident light with respect to the selective reflection layer,
A head-up display system in which the incident light is p-polarized light that vibrates in a direction parallel to the incident surface.
[12] The head-up display system according to [10] or [11], in which the incident light is incident at an angle of 45 ° to 70 ° with respect to a normal line of the projection image display half mirror.
[13] The head-up display system according to any one of [10] to [12], wherein the incident light is incident from below when the windshield glass is used.

  According to the present invention, there is provided a projected image display half mirror that gives a projected image with high brightness without reducing the visible light transmittance of the glass used in combination. Windshield glass having a projected image display portion that provides a projected image with high visible light transmittance and high brightness by using the half mirror for projected image display of the present invention, and a head capable of displaying a projected image with high brightness An up-display system can be provided.

It is a figure which shows typically the rubbing direction of the temporary support body used in the Example.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used in the sense of including the numerical values described before and after it as lower and upper limits.
In this specification, an angle (for example, an angle such as “90 °”) and a relationship (for example, “parallel”, “horizontal”, “vertical”, etc.) are allowed in the technical field to which the present invention belongs. Including the range of errors. For example, it means that the angle is within the range of strict angle ± 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.

In this specification, “selective” for circularly polarized light means that the amount of light of either the right circularly polarized component or the left circularly polarized component of light is greater than that of the other circularly polarized component. Specifically, when referred to as “selective”, the degree of circular polarization of light is preferably 0.3 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. More preferably, it is substantially 1.0. Table In _{/ (I R + I L)} | Here, the degree of circular polarization, the intensity of the right circularly polarized light component of the light I _R, when the strength of the left-handed circularly polarized light component and I _L, | I _R -I _L Is the value to be

  In this specification, “sense” for circularly polarized light means right circularly polarized light or left circularly polarized light. The sense of circularly polarized light is right-handed circularly polarized light when the electric field vector tip turns clockwise as time increases when viewed as the light travels toward you, and left when it turns counterclockwise. Defined as being circularly polarized.

  In this specification, the term “sense” may be used for the twist direction of the spiral of the cholesteric liquid crystal. When the twist direction (sense) of the spiral of the cholesteric liquid crystal is right, it reflects right circularly polarized light and transmits left circularly polarized light. When the sense is left, it reflects left circularly polarized light and transmits right circularly polarized light.

In this specification, “light” means visible light and natural light (unpolarized light) unless otherwise specified. Visible light is light having a wavelength that can be seen by human eyes among electromagnetic waves, and usually indicates light having a wavelength range of 380 nm to 780 nm.
In the present specification, the term “reflected light” or “transmitted light” is used to mean scattered light and diffracted light.

In addition, the polarization state of each wavelength of light can be measured using a spectral radiance meter or a spectrometer equipped with a circularly polarizing plate. In this case, the intensity of light measured through the right circularly polarizing plate corresponds to I _R , and the intensity of light measured through the left circularly polarizing plate corresponds to I _L. Moreover, even if a circularly polarizing plate is attached to an illuminometer or an optical spectrum meter, it can be measured. The ratio can be measured by attaching a right circular polarized light transmission plate, measuring the right circular polarized light amount, attaching a left circular polarized light transmission plate, and measuring the left circular polarized light amount.

  In this specification, p-polarized light means polarized light that vibrates in a direction parallel to the light incident surface. The incident surface means a surface that is perpendicular to a reflecting surface (such as a windshield glass surface) and includes incident light rays and reflected light rays. In p-polarized light, the vibration plane of the electric field vector is parallel to the incident plane.

  In this specification, the front phase difference is a value measured using an AxoScan manufactured by Axometrics. The measurement wavelength is 550 nm unless otherwise specified. The front phase difference may be a value measured by making light having a wavelength in the visible light wavelength region incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). When selecting the measurement wavelength, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.

In this specification, “projection image” means an image based on the projection of light from a projector to be used, not a surrounding landscape such as the front. The projected image is observed as a virtual image that appears above the projected image display portion of the windshield glass as viewed from the observer.
In this specification, “screen image” means an image displayed on a drawing device of a projector or an image drawn on an intermediate image screen or the like by the drawing device. In contrast to a virtual image, an image is a real image.
Both the image and the projected image may be a single color image, a multicolor image of two or more colors, or a full color image.

  In the present specification, the “visible light transmittance” is the A light source visible light transmittance defined in JIS R 3212: 2015 (automobile safety glass test method). That is, the transmittance of each wavelength in the range of 380 nm to 780 nm is measured with a spectrophotometer using the A light source, and the weight obtained from the wavelength distribution and wavelength interval of the CIE (International Lighting Commission) light adaptation standard relative luminous sensitivity. It is a transmittance obtained by multiplying the transmittance coefficient at each wavelength by a weighted average.

<< Half mirror for projected image display >>
In the present specification, the projected image display half mirror means a half mirror capable of displaying a projected image with reflected light.
The projected image display half mirror of the present invention is visible light transmissive. Specifically, the visible light transmittance of the half mirror for displaying projected images of the present invention is preferably 85% or more, more preferably 86% or more, and further preferably 87% or more. By having such a high visible light transmittance, even when a laminated glass is combined with a glass having a low visible light transmittance, it is possible to realize a visible light transmittance that satisfies the standard of a vehicle windshield glass. it can.

  It is preferable that the half mirror for displaying projected images of the present invention does not exhibit substantial reflection in a wavelength range having high visibility. Specifically, when comparing a normal laminated glass and a laminated glass incorporating the half mirror of the present invention with respect to light from the normal direction, it shows a substantially equivalent reflection in the vicinity of a wavelength of 550 nm. Is preferred. More preferably, in the visible light wavelength region of 490 nm to 620 nm, it is preferable to show substantially equivalent reflection. “Substantially equivalent reflection” means, for example, reflection of natural light (non-polarized light) at a target wavelength measured from a normal direction with a spectrophotometer such as a spectrophotometer “V-670” manufactured by JASCO Corporation. It means that the difference in rate is 10% or less. In the above wavelength range, the difference in reflectance is preferably 5% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less. . Visible light transmission that meets the specifications of vehicle windshield glass even when laminated glass is combined with glass with low visible light transmittance by showing substantially equivalent reflection in the wavelength range with high visibility Rate can be realized.

The projected image display half mirror may be a thin film or sheet.
The projection image display half mirror may be in the form of a roll as a thin film before being used in the windshield glass.

  The projected image display half mirror only needs to have a function as a half mirror for at least a part of the projected light. For example, the projected mirror is a half mirror for light in the entire visible light range. It doesn't need to be functional. In addition, the projected image display half mirror may have the function as the above half mirror with respect to light having all incident angles, but the above function with respect to at least part of incident light. It only has to have.

  The projected image display half mirror includes a selective reflection layer. The projected image display half mirror may include layers such as a retardation layer, a support, an alignment layer, and an adhesive layer in addition to the selective reflection layer.

<Selective reflection layer>
The selective reflection layer is a layer that reflects light in a wavelength selective manner, and the selective reflection layer preferably exhibits selective reflection in a part of the visible light wavelength region. The selective reflection layer only needs to reflect light for displaying a projected image.
In the projected image display half mirror of the present invention, the selective reflection center wavelength of the selective reflection layer having the selective reflection central wavelength at the shortest wavelength is 650 to 780 nm. In this specification, the center wavelength λ of selective reflection of the selective reflection layer means a wavelength at the position of the center of gravity of the reflection peak of the reflection spectrum measured from the normal direction of the selective reflection layer. Such a configuration includes, for example, a selective reflection having a selective reflection layer having a selective reflection center wavelength of 650 to 780 nm and a selective reflection having a central wavelength of selective reflection in a visible light wavelength region of less than 650 nm. It can be realized with a configuration that does not include layers.

  In the half mirror for displaying projected images according to the present invention, the selective reflection center wavelength of the selective reflection layer having the selective reflection center wavelength at the shortest wavelength is preferably 750 nm or less, more preferably 720 nm or less, and 700 nm. More preferably, it is as follows.

  The projected image display half mirror of the present invention may include two or more selective reflection layers. The central wavelengths of selective reflection of two or more selective reflection layers may be the same or different, but are preferably different. A double image can be reduced by including two or more selective reflection layers having different central wavelengths of selective reflection. For example, when two selective reflection layers are included, the central wavelength of selective reflection of the two layers is preferably different by 60 nm or more, more preferably different by 80 nm or more, and further preferably different by 100 nm or more. The center wavelength of selective reflection of the two or more selective reflection layers may be 650 to 780 nm, at least one may be 650 to 780 nm, and the others may be wavelengths exceeding 780 nm. It is preferable to be at ˜780 nm.

The selective reflection layer is preferably a polarization reflection layer. The polarization reflection layer is a layer that reflects linearly polarized light, circularly polarized light, or elliptically polarized light. The polarization reflection layer is preferably a circular polarization reflection layer or a linear polarization reflection layer. The circularly polarized light reflecting layer is a layer that reflects the circularly polarized light of one of the senses and transmits the other at the center wavelength of selective reflection. The linearly polarized light reflection layer is a layer that reflects linearly polarized light in one polarization direction and transmits linearly polarized light in the polarization direction orthogonal to the polarization direction at the central wavelength of selective reflection. The polarization reflection layer can transmit polarized light that does not reflect, and can transmit part of light even in a wavelength range where the selective reflection layer shows reflection. Therefore, it is preferable because the color of the light transmitted through the projected image display half mirror is hardly deteriorated and the visible light transmittance is hardly lowered.
As the selective reflection layer which is a circularly polarized light reflection layer, a cholesteric liquid crystal layer is preferable.

[Cholesteric liquid crystal layer]
In this specification, a cholesteric liquid crystal layer means a layer in which a cholesteric liquid crystal phase is fixed.
The cholesteric liquid crystal layer may be a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, the polymerizable liquid crystal compound is placed in the orientation state of the cholesteric liquid crystal phase and then irradiated with ultraviolet rays. Any layer may be used as long as it is polymerized and cured by heating or the like to form a layer having no fluidity, and at the same time, the layer is changed to a state in which the orientation is not changed by an external field or an external force. In the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystal compound in the layer may no longer exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.

It is known that the cholesteric liquid crystal phase exhibits circularly polarized light selective reflection that selectively reflects the circularly polarized light of either the right circularly polarized light or the left circularly polarized light and transmits the circularly polarized light of the other sense.
Many films formed from a composition containing a polymerizable liquid crystal compound have been known as a film containing a layer in which a cholesteric liquid crystal phase exhibiting circularly polarized light selectively is fixed. You can refer to the technology.

  The central wavelength λ of selective reflection of the cholesteric liquid crystal layer depends on the pitch P (= helical period) of the helical structure in the cholesteric phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. As can be seen from this equation, the center wavelength of selective reflection can be adjusted to 650 to 780 nm by adjusting the n value and the P value.

The selective reflection center wavelength and the half-value width of the cholesteric liquid crystal layer can be obtained as follows.
When the transmission spectrum of the cholesteric liquid crystal layer (measured from the normal direction of the cholesteric liquid crystal layer) is measured using a spectrophotometer UV3150 (Shimadzu Corporation), a reduction peak in transmittance is observed in the selective reflection band. Of the two wavelengths that have an intermediate (average) transmittance between the minimum transmittance of this peak and the transmittance before the decrease, the wavelength value on the short wavelength side is λ _l (nm), and the wavelength value on the long wavelength side Is λ _h (nm), the center wavelength λ and the half-value width Δλ of selective reflection can be expressed by the following equations.
λ = (λ _l + λ _h ) / 2
Δλ = (λ _h −λ _l )
The center wavelength of selective reflection obtained as described above substantially matches the wavelength at the center of gravity of the reflection peak of the circularly polarized reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer.

As will be described later, in the head-up display system, the reflectance on the glass plate surface on the projection light incident side can be lowered by using the windshield glass so that light is incident obliquely. At this time, light is also incident obliquely on the cholesteric liquid crystal layer. For example, light incident at an angle of 45 ° to 70 ° with respect to the normal line of the projected image display part in air having a refractive index of 1 has an angle of about 26 ° to 36 ° for a cholesteric liquid crystal layer having a refractive index of about 1.61. It penetrates with. In this case, the reflected wavelength is shifted to the short wavelength side. The central wavelength of selective reflection when a light ray passes through an angle of θ ₂ with respect to the normal direction of the cholesteric liquid crystal layer (the direction of the helical axis of the cholesteric liquid crystal layer) in the cholesteric liquid crystal layer having a selective reflection center wavelength of λ. When λ _{d is} assumed, λ _d is expressed by the following equation.
λ _d = λ × cos θ ₂

Therefore, when θ ₂ is 26 ° to 36 °, the cholesteric liquid crystal layer having the central wavelength of selective reflection in the range of 650 to 780 nm can reflect the projection light in the range of 520 to 695 nm.
Since such a wavelength range is a wavelength region with high visibility, contribution to the brightness of the projected image is high, and as a result, a projected image with high brightness can be realized.

  Since the pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound or the concentration of the chiral agent, the desired pitch can be obtained by adjusting these. For the method of measuring spiral sense and pitch, use the methods described in “Introduction to Liquid Crystal Chemistry Experiments”, edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, page 46, and “Liquid Crystal Handbook”, Liquid Crystal Handbook Editing Committee, page 196. be able to.

  In the projected image display half mirror, the cholesteric liquid crystal layer is preferably arranged in order from the shortest central wavelength of selective reflection as viewed from the viewing side (inside the vehicle).

  As each cholesteric liquid crystal layer, a cholesteric liquid crystal layer whose spiral sense is either right or left is used. The sense of reflected circularly polarized light in the cholesteric liquid crystal layer coincides with the sense of a spiral. The spiral senses of the cholesteric liquid crystal layers having different selective reflection center wavelengths may all be the same or may include different ones, but are preferably the same.

  Further, the projected image display half mirror preferably does not include a cholesteric liquid crystal layer having a different spiral sense as a cholesteric liquid crystal layer exhibiting selective reflection in the same or overlapping wavelength region. This is to prevent the transmittance in a specific wavelength region from decreasing to, for example, less than 50%.

The full width at half maximum Δλ (nm) of the selective reflection band showing selective reflection depends on the relationship of Δλ = Δn × P, where Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the type and mixing ratio of the polymerizable liquid crystal compound or by controlling the temperature at the time of alignment fixation.
In order to form one type of cholesteric liquid crystal layer having the same selective reflection center wavelength, a plurality of cholesteric liquid crystal layers having the same pitch P and the same spiral sense may be stacked. By laminating cholesteric liquid crystal layers having the same pitch P and the same spiral sense, the circularly polarized light selectivity can be increased at a specific wavelength.

  When laminating a plurality of cholesteric liquid crystal layers, a separately prepared cholesteric liquid crystal layer may be laminated using an adhesive or the like, and the polymerizable liquid crystal is directly applied to the surface of the previous cholesteric liquid crystal layer formed by the method described later. A liquid crystal composition containing a compound or the like may be applied and the alignment and fixing steps may be repeated, but the latter is preferred. By forming the next cholesteric liquid crystal layer directly on the surface of the previously formed cholesteric liquid crystal layer, the orientation direction of the liquid crystal molecules on the air interface side of the previously formed cholesteric liquid crystal layer and the cholesteric liquid crystal layer formed thereon This is because the orientation directions of the lower liquid crystal molecules coincide with each other, and the polarization property of the laminate of cholesteric liquid crystal layers is improved. Moreover, interference unevenness that may be caused by unevenness in the thickness of the adhesive layer is not observed.

The thickness of the cholesteric liquid crystal layer is preferably 0.5 μm to 10 μm, more preferably 1.0 μm to 8.0 μm, and still more preferably 1.5 μm to 6.0 μm. The total thickness of the cholesteric liquid crystal layer in the projected image display half mirror is preferably 2.0 μm to 30 μm, more preferably 2.5 μm to 25 μm, and 3.0 μm to 20 μm. Further preferred.
In the half mirror for displaying projected images of the present invention, the visible light transmittance can be maintained high without reducing the thickness of the cholesteric liquid crystal layer.

(Method for producing cholesteric liquid crystal layer)
Hereinafter, a manufacturing material and a manufacturing method of the cholesteric liquid crystal layer will be described.
Examples of the material used for forming the cholesteric liquid crystal layer include a liquid crystal composition containing a polymerizable liquid crystal compound and a chiral agent (optically active compound). If necessary, apply the above liquid crystal composition mixed with a surfactant or a polymerization initiator and dissolved in a solvent to the support, alignment layer, cholesteric liquid crystal layer as a lower layer, etc. A cholesteric liquid crystal layer can be formed by being fixed by curing the liquid crystal composition.

(Polymerizable liquid crystal compound)
The polymerizable liquid crystal compound may be a rod-like liquid crystal compound or a disk-like liquid crystal compound, but is preferably a rod-like liquid crystal compound.
Examples of the rod-like polymerizable liquid crystal compound forming the cholesteric liquid crystal layer include a rod-like nematic liquid crystal compound. Examples of rod-like nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystal compounds but also high-molecular liquid crystal compounds can be used.

  The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1-6, more preferably 1-3, per molecule. Examples of polymerizable liquid crystal compounds are described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648 and 5,770,107, International Publication WO95 / 22586, International Published WO 95/24455, WO 97/00600, WO 98/23580, WO 98/52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and JP-A-2001 -3282893 etc. are included. Two or more kinds of polymerizable liquid crystal compounds may be used in combination. When two or more kinds of polymerizable liquid crystal compounds are used in combination, the alignment temperature can be lowered.

  Moreover, it is preferable that the addition amount of the polymeric liquid crystal compound in a liquid-crystal composition is 80-99.9 mass% with respect to solid content mass (mass except a solvent) of a liquid-crystal composition, and 85-99. More preferably, it is 5 mass%, and it is especially preferable that it is 90-99 mass%.

(Chiral agent: optically active compound)
The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral compound may be selected according to the purpose because the helical sense or helical pitch induced by the compound is different.
There is no restriction | limiting in particular as a chiral agent, A well-known compound can be used. Examples of chiral agents include liquid crystal device handbook (Chapter 3-4, TN, chiral agent for STN, 199 pages, edited by Japan Society for the Promotion of Science, 142nd Committee, 1989), JP-A 2003-287623, Examples thereof include compounds described in JP-A No. 2002-302487, JP-A No. 2002-80478, JP-A No. 2002-80851, JP-A No. 2010-181852 or JP-A No. 2014-034581.

A chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, they are derived from the repeating unit derived from the polymerizable liquid crystal compound and the chiral agent by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. A polymer having repeating units can be formed. In this aspect, the polymerizable group possessed by the polymerizable chiral agent is preferably the same group as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Particularly preferred.
The chiral agent may be a liquid crystal compound.

As the chiral agent, an isosorbide derivative, an isomannide derivative, or a binaphthyl derivative can be preferably used. As the isosorbide derivative, commercially available products such as LC-756 manufactured by BASF may be used.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, more preferably 1 mol% to 30 mol% of the amount of the polymerizable liquid crystal compound.

(Polymerization initiator)
The liquid crystal composition preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850), acylphosphine oxide compounds (JP-B 63-40799, JP-B-5) No. 29234, Japanese Patent Laid-Open No. 10-95788 JP, 10-29997, JP 2001-233842, JP 2000-80068, JP 2006-342166, JP 2013-114249, JP 2014-137466, Japanese Patent No. 4223071, Japanese Patent Application Laid-Open No. 2010-262028, Japanese Patent Publication No. 2014-500852), an oxime compound (Japanese Patent Application Laid-Open No. 2000-66385, Japanese Patent No. 4454067), and an oxadiazole compound ( U.S. Pat. No. 4,221,970). For example, description of paragraph 0500-0547 of Unexamined-Japanese-Patent No. 2012-208494 can also be considered.

As the polymerization initiator, it is also preferable to use an acyl phosphine oxide compound or an oxime compound.
As the acylphosphine oxide compound, for example, IRGACURE 810 (compound name: bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide) manufactured by BASF Japan Ltd. can be used. As oxime compounds, IRGACURE OXE01 (manufactured by BASF), IRGACURE OXE02 (manufactured by BASF), TR-PBG-304 (manufactured by Changzhou Power Electronics New Materials Co., Ltd.), Adeka Arcles NCI-831, Adeka Arcles NCI-930 Commercial products such as (ADEKA) and Adeka Arcles NCI-831 (ADEKA) can be used.
Only one type of polymerization initiator may be used, or two or more types may be used in combination.
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1% by mass to 20% by mass, and preferably 0.5% by mass to 5% by mass with respect to the content of the polymerizable liquid crystal compound. More preferably.

(Crosslinking agent)
The liquid crystal composition may optionally contain a crosslinking agent in order to improve the film strength after curing and improve the durability. As the cross-linking agent, those that can be cured by ultraviolet rays, heat, moisture and the like can be suitably used.
There is no restriction | limiting in particular as a crosslinking agent, According to the objective, it can select suitably, For example, polyfunctional acrylate compounds, such as a trimethylol propane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; Glycidyl (meth) acrylate , Epoxy compounds such as ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylto Alkoxysilane compounds such as methoxy silane. Moreover, a well-known catalyst can be used according to the reactivity of a crosslinking agent, and productivity can be improved in addition to membrane strength and durability improvement. These may be used individually by 1 type and may use 2 or more types together.
3 mass%-20 mass% are preferable, and, as for content of a crosslinking agent, 5 mass%-15 mass% are more preferable. By making the content of the crosslinking agent 3% by mass or more, the effect of improving the crosslinking density can be obtained, and by making the content of the crosslinking agent 20% by mass or less, the stability of the cholesteric liquid crystal layer is lowered. Can be prevented.

(Orientation control agent)
In the liquid crystal composition, an alignment control agent that contributes to stably or rapidly forming a cholesteric liquid crystal layer having a planar alignment may be added. Examples of the orientation control agent include fluorine (meth) acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and paragraphs [0031] to [0034] of JP-A-2012-203237. And the compounds represented by formulas (I) to (IV), and the compounds described in JP2013-113913A.
In addition, as an orientation control agent, 1 type may be used independently and 2 or more types may be used together.

  The addition amount of the alignment control agent in the liquid crystal composition is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass with respect to the total mass of the polymerizable liquid crystal compound. 0.02% by mass to 1% by mass is particularly preferable.

(Other additives)
In addition, the liquid crystal composition may contain at least one selected from a surfactant for adjusting the surface tension of the coating film to make the thickness uniform, and various additives such as a polymerizable monomer. In addition, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, etc. are added to the liquid crystal composition as necessary, as long as optical performance is not deteriorated. can do.

  A cholesteric liquid crystal layer is prepared by preparing a liquid crystal composition in which a polymerizable liquid crystal compound and a polymerization initiator, a chiral agent added as necessary, a surfactant, and the like are dissolved in a solvent, a support, an alignment layer, or first. A cholesteric liquid crystal layer in which the cholesteric regularity is fixed by coating the cholesteric liquid crystal layer on the coated cholesteric liquid crystal layer and drying it to obtain a coating film, and irradiating the coating film with an actinic ray to polymerize the cholesteric liquid crystalline composition Can be formed. In addition, the laminated film which consists of a some cholesteric liquid crystal layer can be formed by repeating the said manufacturing process of a cholesteric liquid crystal layer.

(solvent)
There is no restriction | limiting in particular as a solvent used for preparation of a liquid-crystal composition, Although it can select suitably according to the objective, An organic solvent is used preferably.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, ketones are particularly preferable in consideration of environmental load.

(Coating, orientation, polymerization)
The method for applying the liquid crystal composition to the support, the alignment layer, the underlying cholesteric liquid crystal layer, etc. is not particularly limited and can be appropriately selected according to the purpose. For example, a wire bar coating method, a curtain coating method, Examples include extrusion coating, direct gravure coating, reverse gravure coating, die coating, spin coating, dip coating, spray coating, and slide coating. It can also be carried out by transferring a liquid crystal composition separately coated on a support. The liquid crystal molecules are aligned by heating the applied liquid crystal composition. The heating temperature is preferably 200 ° C. or lower, and more preferably 130 ° C. or lower. By this alignment treatment, an optical thin film in which the polymerizable liquid crystal compound is twisted and aligned so as to have a helical axis in a direction substantially perpendicular to the film surface is obtained.

The liquid crystal composition can be cured by further polymerizing the aligned liquid crystal compound. The polymerization may be either thermal polymerization or photopolymerization utilizing light irradiation, but photopolymerization is preferred. It is preferable to use ultraviolet rays for light irradiation. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , 100mJ / cm 2 ~1,500mJ / cm 2 is more preferable. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 350 nm to 430 nm. The polymerization reaction rate is preferably as high as possible from the viewpoint of stability, preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can be determined by measuring the consumption ratio of the polymerizable functional group using an IR absorption spectrum.

[Linear polarization reflection layer]
As the selective reflection layer, a linearly polarized light reflection layer may be used. Examples of the linearly polarized light reflecting layer include a polarizer in which thin films having different refractive index anisotropies are stacked. Similar to the cholesteric liquid crystal layer, such a polarizer can have a high visible light transmittance and a central wavelength of selective reflection in a specific wavelength range of 650 nm to 780 nm. In addition, it is possible to reflect projection light incident obliquely at the time of use in a head-up display system at a wavelength having high visibility.

  As a polarizer in which thin films having different refractive index anisotropies are laminated, for example, those described in JP-T-9-506837 can be used. Specifically, when processed under conditions selected to obtain a refractive index relationship, a polarizer can be formed using a wide variety of materials. In general, one of the first materials needs to have a different refractive index than the second material in the chosen direction. This difference in refractive index can be achieved in a variety of ways, including stretching, extrusion, or coating during or after film formation. Furthermore, it is preferred to have similar rheological properties (eg, melt viscosity) so that the two materials can be coextruded.

A commercial item can be used as a polarizer which laminated | stacked the thin film from which refractive index anisotropy differs. As a commercial item, you may use what is a laminated body of a reflective polarizing plate and a temporary support body. Examples of commercially available products include DBEF (registered trademark) (manufactured by 3M), and commercially available optical films sold as APF (Advanced Polarizing Film (manufactured by 3M)).
The thickness of the reflective polarizing plate is preferably in the range of 2.0 μm to 50 μm, more preferably in the range of 8.0 to 30 μm.

<Phase difference layer>
The projected image display half mirror of the present invention may include a retardation layer. The projected image display half mirror including the cholesteric liquid crystal layer preferably includes a retardation layer. By using the retardation layer in combination with the cholesteric liquid crystal layer, a clear projected image can be displayed. By adjusting the front phase difference and the slow axis direction, it is possible to provide a half mirror for projecting image display that can provide high brightness in the head-up display system and can prevent double images.
In the projected image display half mirror, the phase difference layer is provided so as to be on the viewing side with respect to all the selective reflection layers (cholesteric liquid crystal layers) in use.

  The retardation layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, stretched polycarbonate film, stretched norbornene polymer film, inorganic particles having birefringence such as strontium carbonate And a transparent film oriented and contained, a thin film obtained by obliquely depositing an inorganic dielectric on a support, and a film in which a liquid crystal compound is oriented and fixed uniaxially.

  As the retardation layer, a film in which a polymerizable liquid crystal compound is uniaxially aligned and fixed is preferable. For example, the retardation layer is applied to a temporary support or a liquid crystal composition containing a polymerizable liquid crystal compound on the surface of the alignment layer, and then the polymerizable liquid crystal compound in the liquid crystal composition is formed into a nematic alignment in a liquid crystal state and then cured. Can be formed by immobilization. In this case, the retardation layer can be formed in the same manner as the formation of the cholesteric liquid crystal layer except that no chiral agent is added to the liquid crystal composition. However, at the time of nematic alignment after application of the liquid crystal composition, the heating temperature is preferably 50 ° C to 120 ° C, more preferably 60 ° C to 100 ° C.

  A retardation layer is a layer obtained by applying a composition containing a polymer liquid crystal compound to the surface of a temporary support or an alignment layer to form a nematic alignment in a liquid crystal state, and then fixing the alignment by cooling. It may be.

  The thickness of the retardation layer is preferably 0.2 μm to 300 μm, more preferably 0.5 μm to 150 μm, and even more preferably 1.0 μm to 80 μm. The thickness of the retardation layer formed from the liquid crystal composition is not particularly limited, but is preferably 0.2 μm to 10 μm, more preferably 0.5 μm to 5.0 μm, and even more preferably 1.0 μm to 2.0 μm.

The slow axis direction of the retardation layer is preferably determined according to the incident direction of incident light for displaying a projected image and the spiral sense of the cholesteric liquid crystal layer when used as a head-up display system. For example, in a projected video display half mirror, when the direction of use in a head-up display system is determined, the incident light is in the lower (vertical down) direction of the projected video display half mirror and on the cholesteric liquid crystal layer. On the other hand, in the case of incidence from the phase difference layer side, the slow axis direction can be determined in the following range according to the front phase difference:
When a retardation layer having a front retardation of 250 to 450 nm is used, the slow axis of the retardation layer is + 30 ° to + 85 ° or −30 ° to −85 ° with respect to the vertical upward direction of the half mirror for projecting image display. Range; and
When a retardation layer having a front phase difference of 50 to 180 nm is used, the slow axis of the retardation layer is + 120 ° to + 175 ° or −120 ° to −175 ° with respect to the vertical upward direction of the half mirror for projecting image display. range.

Furthermore, the following configuration is preferred:
When a retardation layer having a front retardation of 250 to 450 nm is used, the slow axis of the retardation layer is + 35 ° to + 70 ° or −35 ° to −70 ° with respect to the vertical upward direction of the half mirror for projecting image display. Range; and
When a retardation layer having a front phase difference of 50 to 180 nm is used, the slow axis of the retardation layer is + 125 ° to + 160 ° or −125 ° to −160 ° with respect to the vertical upward direction of the projection image display half mirror. range.

  As for the slow axis, + and − are defined above, which means a clockwise direction and a counterclockwise direction when the viewing position is fixed. The preferred direction depends on the spiral sense of the cholesteric liquid crystal layer of the projection image display half mirror. For example, when the spiral senses of all cholesteric liquid crystal layers included in the projected image display half mirror are on the right, the slow axis direction is 30 ° clockwise when viewed from the phase difference layer side with respect to the cholesteric liquid crystal layer. It may be ˜85 ° or 120 ° to 175 °. When the spiral senses of all the cholesteric liquid crystal layers included in the projected image display half mirror are on the left, the slow axis direction is 30 ° counterclockwise with respect to the cholesteric liquid crystal layer as viewed from the phase difference layer side. It may be 85 ° or 120 ° to 175 °.

[Second retardation layer]
The projected image display half mirror may include a second retardation layer in addition to the retardation layer. The second retardation layer is provided so that the above-described retardation layer (hereinafter sometimes referred to as “first retardation layer”), all the cholesteric liquid crystal layers, and the second retardation layer are in this order. Just do it. In particular, the first retardation layer, the selective reflection layer, and the second retardation layer may be provided in this order from the viewing side. By including the second retardation layer at the above position in addition to the first retardation layer, double images can be further prevented. In particular, it is possible to further prevent double images when a projected image is formed by entering p-polarized light.
The reason why the double image can be further prevented by using the second retardation layer is that light having a wavelength that is not in the selective reflection band of the cholesteric liquid crystal layer is polarized by the cholesteric liquid crystal layer and reflected by the back surface of the windshield glass. It is presumed that the double image based on being performed can be prevented.

The retardation of the second retardation layer may be appropriately adjusted in the range of 160 nm to 460 nm, preferably in the range of 240 nm to 420 nm at the wavelength of 550 nm.
The material, thickness, and the like of the second retardation layer can be selected in the same range as the first retardation layer.

  The slow axis direction of the second retardation layer is preferably determined according to the incident direction of incident light for projecting image display and the spiral sense of the cholesteric liquid crystal layer. For example, the second phase difference layer having a front phase difference in the range of 160 nm to 400 nm is + 10 ° to + 35 ° or −10 ° to −35 ° with respect to the vertical direction of the projection mirror display half mirror. It is preferable to be in the range. The second retardation layer having a front phase difference in the range of 200 nm to 400 nm is in the range of + 100 ° to + 140 °, or −100 ° to −140 °, with respect to the vertical direction of the projection image display half mirror. It is preferable that

[Other layers]
The projected image display half mirror may include a layer other than the selective reflection layer, the first retardation layer, and the second retardation layer. All other layers are preferably transparent in the visible light region.
Moreover, it is preferable that all other layers have low birefringence. In the present specification, the low birefringence means that the front phase difference is 10 nm or less in the wavelength region where the projection image display half mirror of the windshield glass of the present invention reflects, and the front position The phase difference is preferably 5 nm or less. Further, it is preferable that the other layers have a small difference in refractive index from the average refractive index (in-plane average refractive index) of the cholesteric liquid crystal layer. Examples of other layers include a support, an alignment layer, and an adhesive layer.

(Support)
The support can be a substrate during the formation of the cholesteric liquid crystal layer or the retardation layer.
The support is not particularly limited. The support used for forming the cholesteric liquid crystal layer or retardation layer is a temporary support that is peeled off after the formation of the cholesteric liquid crystal layer, and is not included in the completed half mirror for projection video display or windshield glass. It does not have to be. Examples of the support include plastic films such as polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, and silicone. In addition to the plastic film, glass may be used as the temporary support.
The thickness of the support may be about 5.0 μm to 1000 μm, preferably 10 μm to 250 μm, and more preferably 15 μm to 90 μm.

(Orientation layer)
The projected image display half mirror may include an alignment layer as a lower layer to which the liquid crystal composition is applied when the cholesteric liquid crystal layer or the retardation layer is formed.
The alignment layer has a rubbing treatment of organic compounds such as polymers (resins such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, modified polyamide), oblique deposition of inorganic compounds, and microgrooves. It can be provided by means such as formation of a layer or accumulation of an organic compound (for example, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate) using the Langmuir-Blodgett method (LB film). Further, an alignment layer that generates an alignment function by application of an electric field, application of a magnetic field, or light irradiation may be used.
In particular, the alignment layer made of a polymer is preferably subjected to a rubbing treatment and then a liquid crystal composition is applied to the rubbing treatment surface. The rubbing treatment can be performed by rubbing the surface of the polymer layer with paper or cloth in a certain direction.
You may apply | coat a liquid-crystal composition to the surface of a support body which does not provide an alignment layer, or the surface which carried out the rubbing process of the support body.
When the liquid crystal layer is formed using the temporary support, the alignment layer does not have to be peeled off together with the temporary support to form a layer constituting the projected image display half mirror.
The thickness of the alignment layer is preferably 0.01 to 5.0 μm, and more preferably 0.05 to 2.0 μm.

(Adhesive layer)
The adhesive layer may be provided, for example, between the cholesteric liquid crystal layer, between the cholesteric liquid crystal layer and the retardation layer, between the cholesteric liquid crystal layer and the second retardation layer, and between the cholesteric liquid crystal layer and the support. . Further, it may be provided between the cholesteric liquid crystal layer and the interlayer sheet, between the retardation layer (first or second) and the interlayer sheet, and the like.

The adhesive layer may be formed from an adhesive.
Adhesives include hot melt type, thermosetting type, photocuring type, reactive curing type, and pressure-sensitive adhesive type that does not require curing, from the viewpoint of curing method, and the materials are acrylate, urethane, urethane acrylate, epoxy , Epoxy acrylate, polyolefin, modified olefin, polypropylene, ethylene vinyl alcohol, vinyl chloride, chloroprene rubber, cyanoacrylate, polyamide, polyimide, polystyrene, polyvinyl butyral, etc. can do. From the viewpoint of workability and productivity, the photocuring type is preferable as the curing method, and from the viewpoint of optical transparency and heat resistance, it is preferable to use an acrylate, urethane acrylate, epoxy acrylate, or the like material.

The adhesive layer may be formed using a highly transparent adhesive transfer tape (OCA tape). As the highly transparent adhesive transfer tape, a commercially available product for an image display device, particularly a commercially available product for the image display unit surface of the image display device may be used. As an example of a commercial item, the adhesive sheet (PD-S1 etc.) by Panac Co., Ltd., the MHM series adhesive sheet of Nichiei Kako Co., Ltd., etc. are mentioned.
The thickness of the adhesive layer is preferably 0.5 to 10 μm, and more preferably 1.0 to 5.0 μm. Moreover, 10 micrometers-50 micrometers may be sufficient as the thickness of the contact bonding layer formed using the OCA tape, and 15 micrometers-30 micrometers are preferable. In order to reduce color unevenness and the like of the projected image display half mirror, it is preferably provided with a uniform thickness.

<Windshield glass>
The windshield glass which has a projection image display function using the half mirror for a projection image display of this invention can be provided.
In this specification, the windshield glass means a window glass for vehicles such as cars, trains, airplanes, ships, play equipment and the like. The windshield glass is preferably a windshield in the direction of travel of the vehicle. The windshield glass is preferably a vehicle windshield.

  The visible light transmittance of the windshield glass is preferably 70% or more, more preferably more than 70%, further preferably 75% or more, and particularly preferably 80% or more. The visible light transmittance is preferably satisfied at any position of the windshield glass, and it is particularly preferable that the projected image display portion satisfies the visible light transmittance. As described above, the projected image display half mirror of the present invention has a high visible light transmittance in a wavelength range having high visibility, so that any of the glasses generally used for windshield glass can be used. The visible light transmittance can be satisfied.

  The windshield glass may be planar. Further, the windshield glass may be formed for incorporation into an applied vehicle, and may have, for example, a curved surface. In a windshield glass formed for a vehicle to be applied, a direction that is upward (vertically upward) and a surface that is on the viewing side (observer side, driver side, vehicle interior side) during normal use can be specified. In the present specification, when the windshield glass or the projection image display half mirror is referred to as being vertically above, it means the direction that is vertically above when it can be specified as described above.

  The windshield glass may have a uniform thickness or a non-uniform thickness at the projected image display portion. For example, it may have a wedge-shaped cross-sectional shape like the glass for vehicles described in JP-T-2011-505330 and the projection image display part may have a nonuniform thickness. It is preferable that it is uniform.

[Projected image display area]
The half mirror for projected image display of the present invention may be provided at the projected image display portion of the windshield glass.
The projected image display portion can be formed by providing the projected image display half mirror on the outer surface of the glass plate of the windshield glass, or by providing it on the intermediate layer of the windshield glass having a laminated glass structure as described later. When the windshield glass is provided on the outer surface of the glass plate, the projected image display half mirror may be provided on the viewing side as viewed from the glass plate or on the opposite side, but provided on the viewing side. It is preferable that More preferably, the projected image display half mirror is provided in the intermediate layer. This is because the projected image display half mirror is protected with lower scratch resistance than the glass plate.

In this specification, the projected image display part is a part capable of displaying a projected image with reflected light, and may be any part capable of displaying the projected image projected from a projector or the like so as to be visible.
The projected image display part functions as a combiner of the head-up display system. In the head-up display system, the combiner can display the image projected from the projector so as to be visible, and information on the opposite side when the combiner is observed from the same side where the image is displayed. Or the optical member which can observe scenery simultaneously. That is, the combiner has a function as an optical path combiner that displays the ambient light and the image light in a superimposed manner.

The projected image display part may be on the entire surface of the windshield glass, or may be part of the entire area of the windshield glass, but is preferably a part. In some cases, the projected image display part may be provided at any position on the windshield glass, but when used as a head-up display system, a virtual image is formed at a position that is easily visible from an observer (for example, a driver). It is preferably provided as shown. For example, the position where the projected image display part is provided may be determined from the relationship between the position of the driver's seat of the applied vehicle and the position where the projector is installed.
The projected image display part may be a flat surface having no curved surface, but may have a curved surface, and has a concave or convex shape as a whole, and enlarges or reduces the projected image. It may be displayed.

[Laminated glass]
The windshield glass may have a laminated glass configuration. That is, it is preferable to have a structure in which two glass plates are bonded via an intermediate layer. In the present specification, in the windshield glass, a glass plate located farther from the viewing side may be referred to as a first glass plate, and a glass plate located closer may be referred to as a second glass plate.
As a glass plate, the glass plate generally used for windshield glass can be used. For example, a glass plate having a visible light transmittance of 80% or less, such as 73% or 76%, such as green glass having high heat shielding properties may be used. Even when a glass plate having a low visible light transmittance is used in this way, a visible light transmittance of 70% or more can be obtained even in a projected image display portion by using the projected image display half mirror of the present invention. The windshield glass which has can be produced.

Although there is no restriction | limiting in particular about the thickness of a glass plate, What is necessary is just about 0.5 mm-5.0 mm, 1.0 mm-3.0 mm are preferable, and 2.0-2.3 mm are more preferable.
The materials or thicknesses of the first glass plate and the second glass plate may be the same or different.

  The windshield glass having a laminated glass configuration can be manufactured using a known laminated glass manufacturing method. Generally, after sandwiching an interlayer film sheet for laminated glass between two glass plates, heat treatment and pressure treatment (treatment using a rubber roller, etc.) are repeated several times, and finally an autoclave is used. Thus, it can be produced by a method of performing a heat treatment under a pressurized condition.

  The windshield glass having a laminated glass configuration including the projected image display half mirror in the intermediate layer is formed through a normal laminated glass manufacturing process after the projected image display half mirror is formed on the glass plate surface. Alternatively, the laminated glass interlayer film for laminated glass including the projected image display half mirror may be used as the interlayer film sheet, and the above heat treatment and pressure treatment may be performed. When forming the projected image display half mirror on the glass plate surface, the glass plate forming the projected image display half mirror may be the first glass plate or the second glass plate. At this time, the projected image display half mirror may be bonded to a glass plate with an adhesive, for example.

(Interlayer sheet)
As an intermediate film in the case of using an intermediate film that does not include the projected image display half mirror, any known intermediate film may be used. For example, a resin film containing a resin selected from the group of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, and chlorine-containing resin can be used. The resin is preferably a main component of the interlayer sheet. The main component means a component that occupies a ratio of 50% by mass or more of the interlayer film.

Of the above resins, polyvinyl butyral or ethylene-vinyl acetate copolymer is preferable, and polyvinyl butyral is more preferable. The resin is preferably a synthetic resin.
Polyvinyl butyral can be obtained by acetalizing polyvinyl alcohol with butyraldehyde. The preferable lower limit of the degree of acetalization of the polyvinyl butyral is 40%, the preferable upper limit is 85%, the more preferable lower limit is 60%, and the more preferable upper limit is 75%.

Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 80 to 99.8 mol% is generally used.
Moreover, the preferable minimum of the polymerization degree of the said polyvinyl alcohol is 200, and a preferable upper limit is 3000. When the polymerization degree of polyvinyl alcohol is 200 or more, the penetration resistance of the obtained laminated glass is difficult to decrease, and when it is 3000 or less, the moldability of the resin film is good, and the rigidity of the resin film does not increase too much. Good workability. A more preferred lower limit is 500, and a more preferred upper limit is 2000.

(Interlayer film including half mirror for projected image display)
The laminated interlayer sheet for laminated glass including the projected image display half mirror can be formed by pasting the projected image display half mirror on the surface of the interlayer sheet. Alternatively, it is also possible to form a projected image display half mirror between the two intermediate film sheets. The two interlayer sheets may be the same or different, but are preferably the same.
A known bonding method can be used for bonding the projected image display half mirror and the interlayer sheet, but it is preferable to use a laminating process. In order to prevent the laminate and the interlayer film from being peeled off after processing, it is preferable that the lamination process is performed under a certain degree of heating and pressurization.
In order to perform lamination stably, the film surface temperature on the side to which the interlayer film sheet adheres is preferably 50 to 130 ° C, and more preferably 70 to 100 ° C.
It is preferable to apply pressure during lamination. The pressure condition is preferably less than 2.0 kg / cm ² (less than 196 kPa), more preferably in the range of 0.5 to 1.8 kg / cm ² (49 to 176 kPa), 0.5 to More preferably, it is in the range of 1.5 kg / cm ² (49 to 147 kPa).

Further, in the projected image display half mirror including the support, the support may be peeled off simultaneously with the lamination, immediately after, or immediately before. That is, the laminated intermediate sheet obtained after lamination may not have a support.
An example of a method for producing a laminated interlayer sheet for laminated glass is as follows:
(1) a first step of obtaining a first laminate by laminating a projected image display half mirror on the surface of the first interlayer sheet; and
(2) The second intermediate film sheet is bonded to the surface opposite to the surface of the first laminated body of the projected image display half mirror on which the first intermediate film sheet is bonded. Process.
In the first step, the projected image display half mirror and the first intermediate film are bonded, and the support is peeled off. In the second step, the second intermediate film is peeled off the support. A laminated interlayer sheet for laminated glass that does not include a support can be produced by the method for producing a laminated interlayer sheet for laminated glass that is bonded to the finished surface. Use this laminated interlayer sheet for laminated glass. Thus, a laminated glass not including a support can be easily produced. In order to peel the support stably without breakage or the like, the temperature of the substrate when peeling the support from the projected image display half mirror is preferably 40 ° C. or higher, and preferably 40 to 60 ° C. Is more preferable.

[Layer on the viewing side with respect to the selective reflection layer]
In general, in a projection image display member, based on an image based on reflected light from a layer that reflects projection light, and reflection light from a front surface or a back side as viewed from the light incident side of the projection image display member. Double images (or multiple images) are caused by overlapping images. In the windshield glass, the light transmitted through the selective reflection layer is circularly polarized with a sense opposite to that of the circularly polarized light reflected by the selective reflective layer, or polarized in a direction orthogonal to the reflected light. In the case where the layer on the back side of the selective reflection layer has low birefringence, the polarized light reflected by the selective reflection layer is usually large, and it is difficult to produce a remarkable double image. In particular, by using polarized light as the projection light, most of the projection light can be reflected by the selective reflection layer. On the other hand, the reflected light from the front surface can cause a noticeable double image. In particular, if the distance from the center of gravity of the selective reflection layer to the front surface when viewed from the light incident side of the windshield glass is a certain value or more, a double image can be prominent. Specifically, in the structure of the windshield glass of the present invention, the total thickness of the layers on the first retardation layer side of the selective reflection layer (not including the thickness of the selective reflection layer), that is, the selective reflection layer When the distance from the viewing side surface to the viewing side surface of the windshield glass is 0.5 mm or more, a double image can be prominent, can be more prominent at 1 mm or more, and can be more prominent at 1.5 mm or more. It can be particularly noticeable at 2.0 mm or more. Examples of the layer on the viewer side from the selective reflection layer include a support, an interlayer sheet, and a second glass plate in addition to the first retardation layer.
However, the windshield glass of the present invention has a remarkable double image even when the total thickness of the layers closer to the viewing side than the selective reflection layer is as described above in the projected image display using p-polarized light as described later. The projected image can be viewed without any.

<Head-up display system>
The windshield glass of the present invention can be used as a component of a head-up display system. The head-up display system preferably includes a projector.

[projector]
In this specification, the “projector” is “an apparatus that projects light or an image”, and includes an “apparatus that projects a drawn image”. In the head-up display system of the present invention, the projector only needs to be arranged so as to be incident on the projected image display half mirror in the windshield glass at the oblique incident angle as described above.
In the head-up display system, the projector preferably includes a drawing device and reflects and displays an image (real image) drawn on a small intermediate image screen as a virtual image by a combiner.

(Drawing device)
The drawing device itself may be a device that displays an image, or may be a device that emits light capable of drawing an image. In the drawing device, the light from the light source may be adjusted by a drawing method such as an optical modulator, laser luminance modulation means, or light deflection means for drawing. In this specification, the drawing device means a device that includes a light source and further includes a light modulator, a laser luminance modulation unit, a light deflection unit for drawing, or the like according to a drawing method.

(light source)
The light source is not particularly limited, and LEDs (including light emitting diodes and organic light emitting diodes (OLED)), discharge tubes, laser light sources, and the like can be used. Of these, LEDs and discharge tubes are preferred. This is because it is suitable for a light source of a drawing device that emits linearly polarized light. Of these, LEDs are particularly preferred. This is because LEDs are suitable for combination with a combiner using a cholesteric liquid crystal layer exhibiting selective reflection in a specific wavelength region, as will be described later, because the emission wavelength is not continuous in the visible light region.

(Drawing method)
The drawing method can be selected according to the light source to be used and the application, and is not particularly limited.
Examples of the drawing method include a fluorescent display tube, a liquid crystal display (LCD) method using liquid crystal and a liquid crystal on silicon (LCOS) method, a DLP (digital light processing) method, and a scanning method using a laser. Etc. The drawing method may be a method using a fluorescent display tube integrated with a light source. The drawing method is preferably an LCD.

In the LCD method and the LCOS method, light of each color is modulated and combined by an optical modulator, and light is emitted from a projection lens.
The DLP system is a display system using DMD (Digital Micromirror Device), and is drawn by arranging micromirrors for the number of pixels, and light is emitted from a projection lens.

The scanning method is a method in which a light beam is scanned on a screen and an image is contrasted using an afterimage of an eye. For example, the descriptions in JP-A-7-270711 and JP-A-2013-228664 can be referred to. In the scanning method using laser, laser light of each color (for example, red light, green light, and blue light) whose luminance is modulated is bundled into one light beam by a multiplexing optical system or a condenser lens, and the light beam is light. It only needs to be scanned by the deflecting means and drawn on an intermediate image screen described later.
In the scanning method, the luminance modulation of laser light of each color (for example, red light, green light, and blue light) may be performed directly as a change in intensity of the light source, or may be performed by an external modulator. Examples of the light deflection means include a galvanometer mirror, a combination of a galvanometer mirror and a polygon mirror, or MEMS (microelectromechanical system). Among these, MEMS is preferable. Examples of the scanning method include a random scan method and a raster scan method, but it is preferable to use a raster scan method. In the raster scan method, the laser beam can be driven by a resonance frequency in the horizontal direction and a sawtooth wave in the vertical direction, for example. Since the scanning system does not require a projection lens, the apparatus can be easily downsized.

  The outgoing light from the drawing device may be linearly polarized light or natural light (non-polarized light). The light emitted from the drawing device included in the head-up display system of the present invention is preferably linearly polarized light. In a drawing device whose drawing method is LCD or LCOS and a drawing device using a laser light source, the emitted light is essentially linearly polarized light. When the output light is a linearly polarized light drawing device and the output light contains light of a plurality of wavelengths (colors), the polarization directions (transmission axis directions) of the plurality of light polarizations are the same or orthogonal to each other It is preferable. It is known that there are commercially available drawing devices whose polarization directions are not uniform in the wavelength range of the emitted red, green, and blue light (see Japanese Patent Application Laid-Open No. 2000-212449). Specifically, an example in which the polarization direction of green light is orthogonal to the polarization direction of red light and the polarization direction of blue light is known.

(Intermediate image screen)
As described above, the drawing device may use an intermediate image screen. In this specification, an “intermediate image screen” is a screen on which an image is drawn. That is, when the light emitted from the drawing device is not yet visible as an image, the drawing device forms a visible image on the intermediate image screen by this light. The image drawn on the intermediate image screen may be projected onto the combiner by light transmitted through the intermediate image screen, or may be projected onto the combiner after reflecting off the intermediate image screen.

Examples of the intermediate image screen include a scattering film, a microlens array, and a screen for rear projection. When a plastic material is used as the intermediate image screen, if the intermediate image screen has birefringence, the polarization plane and light intensity of polarized light incident on the intermediate image screen are disturbed, and color unevenness is likely to occur in the combiner. However, the use of a retardation film having a predetermined phase difference can reduce the problem of color unevenness.
The intermediate image screen preferably has a function of spreading and transmitting incident light. This is because the projected image can be enlarged and displayed. As such an intermediate image screen, for example, a screen composed of a microlens array can be cited. The microarray lens used in the head-up display is described in, for example, Japanese Patent Application Laid-Open No. 2012-226303, Japanese Patent Application Laid-Open No. 2010-145745, and Japanese Patent Application Publication No. 2007-523369.
The projector may include a reflecting mirror that adjusts the optical path of the projection light formed by the drawing device.

  With regard to a head-up display system using a windshield glass as a projection image display member, JP-A-2-141720, JP-A-10-96874, JP-A-2003-98470, US Pat. No. 5,013,134 are disclosed. Reference can be made to JP-T-2006-512622.

  The windshield glass of the present invention is particularly useful for a head-up display system that uses a laser, LED, OLED or the like whose emission wavelength is not continuous in the visible light region in combination with a projector that uses a light source. This is because the central wavelength of selective reflection of the cholesteric liquid crystal layer can be adjusted according to each emission wavelength. Moreover, it can also be used for the projection of a display in which display light such as an LCD (Liquid Crystal Display) is polarized.

[Projection light (incident light)]
The incident light is preferably incident at an oblique incident angle of 45 ° to 70 ° with respect to the normal line of the projection image display half mirror. The Brewster angle at the interface between glass having a refractive index of about 1.51 and air having a refractive index of about 1 is about 56 °, and p-polarized light is incident within the above-mentioned angle range, so that incident light for displaying a projected image is displayed. With this selective reflection layer, there is little reflected light from the surface of the windshield glass on the viewing side, and it is possible to display an image with less influence of the double image. The angle is preferably 50 ° to 65 °. At this time, the projection image is observed on the incident light incident side at an angle of 45 ° to 70 °, preferably 50 ° to 65 ° on the opposite side of the incident light with respect to the normal line of the selective reflection layer. Any configuration can be used.

Incident light may be incident from any direction such as up, down, left, and right of the windshield glass, and may be determined in correspondence with the viewing direction. For example, the structure which injects with the above oblique incident angles from the downward direction at the time of use is preferable.
Further, the slow axis of the retardation layer in the windshield glass is 30 ° to 85 ° or 120 depending on the front phase difference of the retardation layer with respect to the vibration direction of the incident p-polarized light (incident light incident surface). More preferably, the angle is in the range of ° to 175 °.

  As described above, it is preferable that the projection light at the time of projection image display on the head-up display is p-polarized light that vibrates in a direction parallel to the incident surface. If the output light of the projector is not linearly polarized light, it may be p-polarized by using a linearly polarizing film arranged on the output light side of the projector, and it is made p-polarized in the optical path from the projector to the windshield glass. Also good. As described above, for projectors whose polarization directions in the red, green, and blue light wavelength ranges are not uniform, the polarization direction is adjusted in a wavelength-selective manner, and p-polarized light is used in all color wavelength ranges. It is preferable to make it enter.

  The head-up display system may be a projection system in which the virtual image formation position is variable. Such a projection system is described in, for example, Japanese Patent Application Laid-Open No. 2009-150947. By making the virtual image imaging position variable, the driver can view the virtual image more comfortably and with high convenience. The virtual image forming position is a position where a virtual image can be visually recognized by the driver of the vehicle, and is, for example, a position that is 1000 mm or more away from the tip of the windshield glass when viewed from the normal driver. Here, if the glass is non-uniform (wedge shape) in the projected image display part as described in the above-mentioned special table 2011-505330, the angle of the wedge shape is also changed when the virtual image forming position is changed. Need to do. Therefore, for example, as described in Japanese Patent Application Laid-Open No. 2017-15902, it is necessary to change the projection position by partially changing the wedge-shaped angle to cope with the virtual image imaging position change. In the head-up display system constructed using the windshield glass of the present invention and utilizing p-polarized light as described above, the use of wedge-shaped glass is unnecessary, and the thickness of the glass is made uniform in the projected image display portion. Therefore, it is possible to suitably employ a projection system in which the virtual image imaging position is variable.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

<Preparation of coating solution>
(Coating liquid for forming cholesteric liquid crystal layer)
The following components were mixed to prepare a coating solution for forming a cholesteric liquid crystal layer having the following composition.
-Mixture 1 100 parts by mass-Orientation control agent 1 0.05 parts by mass-Orientation control agent 2 0.02 parts by mass-Right-turning chiral agent LC756 (manufactured by BASF)
Adjustment / polymerization initiator IRGACURE OXE01 (BASF) according to the target reflection wavelength
1.0 part by mass / solvent (methyl ethyl ketone) Amount at which the solute concentration is 25% by mass

  Coating liquids 1 and 2 were prepared by adjusting the formulation amount of the chiral agent LC-756 having the above coating liquid composition. Using each coating solution, a single layer of cholesteric liquid crystal layer was prepared on a temporary support in the same manner as in the following half mirror production, and the reflection characteristics were confirmed. The reflection layer was the center reflection wavelength as shown in Table 1 below.

(Phase difference layer forming coating solution)
The following components were mixed to prepare a coating solution for forming a retardation layer having the following composition.
-Mixture 1 100 parts by mass-Fluorine-based horizontal alignment agent 1 0.05 parts by mass-Fluorine-based horizontal alignment agent 2 0.01 parts by mass-Polymerization initiator IRGACURE OXE01 (manufactured by BASF)
1.0 part by mass / solvent (methyl ethyl ketone) Amount at which the solute concentration is 25% by mass

<Production of half mirror with temporary support>
(1) A PET film (Cosmo Shine A4100, thickness: 100 μm) manufactured by Toyobo Co., Ltd. was used as a temporary support (length 250 mm × width 280 mm), and the length of the temporary support as shown in FIG. A rubbing process (rayon cloth, pressure: 0.1 kgf (0.98 N), rotation speed: 1000 rpm, conveyance speed: 10 m / min, frequency: 1 reciprocation) is performed in the direction rotated 30 ° clockwise with respect to the side direction. gave.

(2) A coating solution for forming a retardation layer is applied to a rubbed surface of a PET film using a wire bar, dried and placed on a hot plate at 50 ° C., and an electrodeless lamp “D bulb manufactured by Fusion UV Systems Co., Ltd. (60 mW / cm ² ) for 6 seconds to fix the liquid crystal phase to obtain a retardation layer having a thickness of 1.8 μm. At this time, the retardation of the retardation layer was measured by AxoScan (manufactured by Axometrics), and it was 350 nm. The coating liquid 1 is applied to the surface of the obtained retardation layer using a wire bar, dried and placed on a 75 ° C. hot plate, and an electrodeless lamp “D bulb” (60 mW / cm ² ) manufactured by Heraeus Co., Ltd. Was irradiated with UV for 6 seconds to fix the cholesteric liquid crystal phase to obtain a cholesteric liquid crystal layer having a thickness of 2.9 μm. The same process was repeated using the coating liquid 2 on the surface of the obtained cholesteric liquid crystal layer, and a layer of 2.9 μm of the coating liquid 2 was laminated. Thus, a half mirror with a temporary support having a retardation layer and two cholesteric liquid crystal layers was obtained. When the transmission spectrum of the obtained half mirror with a temporary support was measured with a spectrophotometer (manufactured by JASCO Corporation, V-670), transmission spectra having selective reflection center wavelengths at 680 nm and 780 nm were obtained.

  Other procedures were carried out in the same manner as above except that the formulation amount of the chiral agent LC-756 having the above coating liquid composition was adjusted to adjust the center wavelength of selective reflection and the coating amount to show the film thickness as shown in Table 2. The half mirror with a temporary support body of an example and the half mirror with a temporary support body of a comparative example were produced.

<Production of laminated glass>
A 0.38 mm thick PVB film manufactured by Sekisui Chemical Co., Ltd. cut to the same size on a glass plate (300 mm long × 300 mm wide, 2 mm thick, Central Glass, FL2, visible light transmittance 90%) was installed. Each of the half mirrors from which the temporary support has been peeled is placed with the retardation layer side (peeling surface) on the bottom, and a glass plate (300 mm long × 300 mm wide, 2 mm thick, FL2 manufactured by Central Glass Co., Ltd.) , Visible light transmittance 90%). After maintaining this at 90 ° C. and 10 kPa (0.1 atm) for 1 hour, the autoclave (manufactured by Kurihara Seisakusho) is heated at 115 ° C. and 1.3 MPa (13 atm) for 20 minutes to remove bubbles, and Glass was obtained.

[Visible light transmittance evaluation]
As visible light transmittance, A light source visible light transmittance according to JIS R 3212 was determined.
[Brightness evaluation]
The 62 ° p-polarized reflectance spectrum was measured with a spectrophotometer (manufactured by JASCO Corporation, V-670). In the measurement, p-polarized light is incident from 62 ° with respect to the normal direction of the laminated glass, and reflected light (in the incident plane, the direction opposite to the incident direction with respect to the normal direction and the direction of 62 ° with respect to the normal direction) Was observed. At this time, the short mirror direction of the half mirror (direction corresponding to the vertical direction of the long side direction 200 shown in the figure) and the transmission axis of the p-polarized light of the spectrophotometer were matched. According to the observed JIS R3106, the projected image reflectance is calculated by multiplying the p-polarized reflectance by a coefficient corresponding to the visibility and the emission spectrum of a general liquid crystal display device at wavelengths of 380 nm to 780 nm every 10 nm, The brightness was evaluated.
The results are shown in Table 2.

100 rubbing direction 200 long side direction

Claims (13)

A half mirror for displaying projected images,
A selective reflection layer that reflects light in a wavelength-selective manner;
The half mirror for displaying projected images, wherein a selective reflection center wavelength of a selective reflection layer having a selective reflection central wavelength at the shortest wavelength in the visible light wavelength region is 650 to 780 nm. The half mirror for projecting image display according to claim 1, wherein the selective reflection layer is a cholesteric liquid crystal layer. Including two or more cholesteric liquid crystal layers,
The half mirror for projecting image display according to claim 2, wherein the twist direction of the spiral of the two or more cholesteric liquid crystal layers is the same. Including a retardation layer,
The projected image display half mirror according to claim 2 or 3, wherein a front phase difference of the retardation layer is 250 nm to 450 nm, or 50 nm to 180 nm. The half mirror for projecting image display according to claim 1, wherein the selective reflection layer is a linearly polarized light reflection layer. A windshield glass including the half mirror for projecting image display according to any one of claims 1 to 5. A windshield glass comprising the half mirror for projecting image display according to claim 4,
From the viewing side, including the projected image display portion in which the retardation layer and the circularly polarized reflection layer are arranged in this order,
The front phase difference of the retardation layer is 250 nm to 450 nm,
The windshield glass in which the slow axis direction of the retardation layer is in the range of + 30 ° to + 85 °, or −30 ° to −85 °, when the vertical direction of the windshield glass is 0 °. A windshield glass comprising the half mirror for projecting image display according to claim 4,
From the viewing side, including the projected image display portion in which the retardation layer and the circularly polarized reflection layer are arranged in this order,
The front phase difference of the retardation layer is 50 nm to 180 nm,
The windshield glass in which the slow axis direction of the retardation layer is in the range of + 120 ° to + 175 °, or −120 ° to −175 ° when the vertical direction of the windshield glass is 0 °. Including a first glass plate, a second glass plate, and an intermediate layer between the first glass plate and the second glass plate, and at least a part of the intermediate layer includes the half mirror for displaying a projected image The windshield glass according to any one of claims 6 to 8. A head-up display system comprising the windshield glass according to any one of claims 6 to 9,
Incident light for projected image display is incident on the projected image display half mirror,
A head-up display system in which the incident light is p-polarized light that vibrates in a direction parallel to the incident surface. A head-up display system comprising the windshield glass according to claim 7 or 8,
Incident light for projected image display is incident on the projected image display half mirror,
The retardation layer is disposed on the incident side of the incident light with respect to the selective reflection layer,
A head-up display system in which the incident light is p-polarized light that vibrates in a direction parallel to the incident surface. The head-up display system according to claim 10 or 11, wherein the incident light is incident at an angle of 45 ° to 70 ° with respect to a normal line of the projection image display half mirror. The head-up display system according to any one of claims 10 to 12, wherein the incident light is incident from below when the windshield glass is used.