JP2012220540A - Transmission screen and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission screen capable of displaying a projected image while maintaining high transmissivity.SOLUTION: In a liquid crystal element 1 of a transmission screen 10, a liquid crystal/polymer complex layer is held between a pair of transparent substrates with electrodes and can be in a state intermediate between an optical transmission state and an optical scattering state according to an applied voltage. The liquid crustal element 1 scatters light of an image projected from an image projector 2 in the intermediate state, and displays the image on a surface opposite to a surface where the image is projected.

Description

  The present invention relates to a transmissive screen in which an image projected from a device can be viewed from the opposite side of the device across the screen, and an image display device using the transmissive screen.

  2. Description of the Related Art A rear type screen that can project an image from a projector from the back of the screen and display an image on the front of the screen is known. When a general screen is used, the image is displayed on the screen by projecting the image from the front of the screen. On the other hand, the transmissive screen has an advantage that the projector itself is not obstructed because the projector is installed on the back of the screen, and the projected image is not obstructed by the movement of a person.

  Patent Document 1 describes a projection system using a projector. The projection system described in Patent Document 1 includes a plurality (first and second) light control glass screens. When projecting an image or the like from the projector onto the first screen, the first screen is made opaque. Further, when an image or the like is not projected on the second screen, the state behind the screen is made visible by making the second screen transparent.

JP 2005-24764 A

  In general, an opaque screen is used as a screen for projecting an image from a projector. Therefore, the state behind the screen cannot be visually recognized during the projection of the video. The same applies to the transmissive screen.

  On the other hand, in the projection system described in Patent Document 1, the portion of the screen that does not project an image or the like can be made transparent, but the portion that projects the image needs to be made opaque. Therefore, it is difficult to make the state behind the screen visible along with the projected image.

  However, there are many needs to display the image projected from the projector along with the state behind the screen. Therefore, a screen having high transparency capable of displaying a projected image is desired.

  Therefore, an object of the present invention is to provide a transmissive screen capable of displaying a projected image while maintaining high transparency, and an image display device using the transmissive screen.

  A transmissive screen according to the present invention is a transmissive screen for displaying an image projected from a video projection device, and a liquid crystal / polymer composite layer is sandwiched between a pair of transparent substrates with electrodes and applied voltage. And a liquid crystal element capable of taking an intermediate state between the light transmission state and the light scattering state, and the liquid crystal element scatters the light of the image projected from the video projection device in the intermediate state. The image is displayed on the surface opposite to the projected surface.

  The transmissive screen includes a drive circuit that drives an electrode sandwiching the liquid crystal / polymer composite layer by a pulse width modulation method, and the drive circuit places the liquid crystal element in an intermediate state between a light transmission state and a light scattering state. The electrode may be configured to be driven with a pulse width.

  The liquid crystal element preferably has a transmittance of 60% to 70% as an intermediate state between the light transmission state and the light scattering state.

  An image display device according to the present invention includes an image projection device that projects an image from the front to the rear in a vehicle, and a transmission screen that displays an image projected from the image projection device. A liquid crystal element including a liquid crystal element in which a polymer composite layer is sandwiched between a pair of transparent substrates with electrodes and can take an intermediate state between a light transmission state and a light scattering state according to an applied voltage. The element scatters light of an image projected from the image projection device in an intermediate state, and displays an image on a surface opposite to the projected surface.

  According to the present invention, it is possible to display a projected image while maintaining high transparency.

The typical external view which shows an example of the transmission type screen of this invention. 1 is a schematic cross-sectional view showing a liquid crystal element according to the present invention. Explanatory drawing which illustrates the curable compound which can be used for the liquid crystal element by this invention. Explanatory drawing which shows the transmittance | permeability with respect to the applied voltage (effective value) of the liquid crystal element by this invention. Explanatory drawing which shows the structural example of a schlieren optical system measuring device. Explanatory drawing which shows the example of the integrating sphere utilized when measuring total transmittance. FIG. 3 is a timing chart showing an example of a method for driving a liquid crystal element according to the present invention. Explanatory drawing which shows the example at the time of installing the transmission type screen of this invention in the vehicle. Explanatory drawing which shows the other example at the time of installing the transmission type screen of this invention in the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic external view showing an example of a transmission screen according to the present invention. A transmissive screen 10 illustrated in FIG. 1 includes a liquid crystal element 1 that can switch between a light transmission state and a light scattering state depending on whether a voltage is applied to a transparent electrode based on an external signal or the like. And a drive circuit 4 to be connected. Further, when at least the liquid crystal element 1 is in a state of scattering incident light, the video projection device 2 (hereinafter referred to as the projector 2) projects an image onto one surface of the liquid crystal element 1, and thus an observer. 3 observes the projected image from the other surface of the liquid crystal element 1.

  In the example illustrated in FIG. 1, the projector 2 is disposed in front of the observer 3 with the liquid crystal element 1 interposed therebetween, but the arrangement of the projector 2 is not limited to the front of the observer 3. . The projector 2 may be disposed at any position as long as an image can be projected onto one surface of the liquid crystal element 1 (the surface opposite to the surface observed by the observer 3).

  In the liquid crystal element 1, a transparent electrode is formed in a region controlled to a light scattering state. The transparent electrode is driven by the drive circuit 4. Specifically, the drive circuit 4 controls the voltage applied to the transparent electrode by using a pulse width modulation (PWM) method. Note that the voltage applied by the drive circuit 4 is adjusted according to the situation by a user or the like, for example.

  FIG. 2 is a schematic cross-sectional view illustrating a configuration example of the liquid crystal element 1. In FIG. 2, transparent electrodes 102 and 107 are provided on opposing surfaces of the pair of substrates 101 and 108. Further, alignment films 103 and 106 are provided on the inner side. A liquid crystal layer 104 containing liquid crystal and having a thickness controlled by a spacer (not shown) is sandwiched between the alignment films 103 and 106. Then, the liquid crystal layer 104 is sealed by the seal layer 105.

  The materials of the substrates 101 and 108 are not particularly limited as long as transparency can be secured. As the substrates 101 and 108, a glass substrate or a plastic substrate can be used. Moreover, the shape of the liquid crystal element 1 does not need to be planar, and may be curved.

  Further, as the transparent electrodes 102 and 107 provided on the substrates 101 and 108, a transparent electrode material such as a metal oxide such as ITO (indium oxide-tin oxide) can be used. Hereinafter, the substrates 101 and 108 provided with the transparent electrodes 102 and 107 are referred to as substrates with electrodes.

  The liquid crystal layer 104 capable of taking a light transmission state and a light scattering state is a composition containing a liquid crystal and a curable compound soluble in the liquid crystal (hereinafter, an uncured composition) between a pair of transparent substrates with electrodes. A liquid crystal layer formed by curing a curable compound using means such as heat, ultraviolet rays, or an electron beam. Hereinafter, a liquid crystal composed of a composite of such a liquid crystal and a curable compound is also referred to as a liquid crystal / polymer composite. By using such an uncured composition, the haze value can be kept low when viewed from the oblique direction as well as the front direction when in the transmissive state.

  The liquid crystal used in the liquid crystal / polymer composite may have either positive or negative dielectric anisotropy, but in order to shorten the response time required for switching between the transmission state and the light scattering state, the viscosity of the liquid crystal is low. It is preferable to use a liquid crystal having a negative dielectric anisotropy. A compound that is not curable is used as the liquid crystal. Moreover, the curable compound may have liquid crystallinity.

  In the case where a liquid crystal having a negative dielectric anisotropy is used, in the substrate with electrodes, a treatment is performed so that the pretilt angle of liquid crystal molecules is 60 degrees or more with respect to the substrate surface on the side in contact with the liquid crystal layer 104. When applied, it is preferable because orientation defects can be reduced and transparency is improved. In this case, the rubbing process may not be performed. The pretilt angle is more preferably 70 degrees or more. The pretilt angle is defined as 90 degrees in the direction perpendicular to the substrate surface.

  The liquid crystal constituting the liquid crystal / polymer composite forming the liquid crystal layer 104 can be appropriately selected from known liquid crystals. By using a substrate with an electrode that can control the pretilt angle of the uncured composition by the alignment films 103 and 106, a liquid crystal having a positive dielectric anisotropy and a liquid crystal having a negative dielectric anisotropy can be used. However, a liquid crystal having negative dielectric anisotropy is preferable in terms of higher transparency and response speed. The alignment film can also be rubbed. In order to reduce the driving voltage, it is preferable that the absolute value of dielectric anisotropy is large.

  Further, the curable compound constituting the liquid crystal / polymer composite preferably has transparency. Furthermore, it is preferable that the liquid crystal and the curable compound are separated so that only the liquid crystal responds when a voltage is applied after curing, because the driving voltage can be lowered.

  In the present invention, among the curable compounds that can be dissolved in the liquid crystal, the curable compound that can control the alignment state of the mixture of the liquid crystal and the curable compound when uncured and can maintain high transparency when cured. Is used.

Examples of the curable compound include a compound of formula (1) and a compound of formula (2).
A ¹ —O— (R ¹ ) _m —O—Z—O— (R ² ) _n O—A ² Formula (1)
A ^3- (OR ³ ) _o —O—Z′—O— (R ⁴ O) _p —A ⁴ ... (2)

Here, each of A ¹ , A ² , A ³ , and A ⁴ is independently an acryloyl group, methacryloyl group, glycidyl group, or allyl group that becomes a curing site, and R ¹ , R ² , R ³ , R Each of ⁴ is independently an alkylene group having 2 to 6 carbon atoms, each of Z and Z ′ is independently a divalent mesogenic structure, and each of m, n, o, and p Is independently an integer from 1 to 10. Here, “independently” means that the combination is arbitrary and any combination is possible.

Molecular motion including R ¹ , R ² , R ³ , R ⁴ between the mesogenic structures Z, Z ′ and the cured sites A ¹ , A ² , A ³ , A ^{4 in the} formulas (1) and (2) By introducing a highly functional oxyalkylene structure, the molecular mobility of the cured site can be improved during the curing process during curing, and it can be sufficiently cured in a short time.

The curing sites A ¹ , A ² , A ³ , and A ⁴ in the formulas (1) and (2) may be any functional group as long as they can be photocured or thermally cured. It is preferable that it is an acryloyl group and a methacryloyl group suitable for photocuring.

The carbon number of R ¹ , R ² , R ³ and R ⁴ in formula (1) and formula (2) is preferably 1 to 6 from the viewpoint of molecular mobility, and an ethylene group having 2 carbon atoms and 3 carbon atoms. The propylene group is more preferable.

  Examples of the mesogen structure parts Z and Z ′ in the formulas (1) and (2) include polyphenylene groups in which 1,4-phenylene groups are linked. A part or all of the 1,4-phenylene group may be substituted with a 1,4-cyclohexylene group. In addition, some or all of the hydrogen atoms of the 1,4-phenylene group or the substituted 1,4-cyclohexylene group are substituted with alkyl groups having 1 to 2 carbon atoms, halogen atoms, carboxyl groups, alkoxycarbonyl groups, or the like. It may be substituted with a group.

  As preferable mesogen structure parts Z and Z ′, a biphenylene group in which two 1,4-phenylene groups are linked (hereinafter, a biphenylene group in which two 1,4-phenylene groups are linked is also referred to as a 4,4-biphenylene group). Examples include three linked terphenylene groups, and 1 to 4 of these hydrogen atoms substituted with an alkyl group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom, or a carboxyl group. Most preferred is a 4,4-biphenylene group having no substituent. All the bonds between 1,4-phenylene groups or 1,4-cyclohexylene groups constituting the mesogenic structure may be single bonds or any of the following bonds.

  M, n, o, and p in Formula (1) and Formula (2) are each independently preferably 1 to 10, and more preferably 1 to 4. This is because if it is too large, the compatibility with the liquid crystal is lowered and the transparency of the electro-optical element after curing is lowered.

  FIG. 3 shows examples of curable compounds that can be used in the present invention. The composition containing a liquid crystal and a curable compound may contain a plurality of curable compounds including the curable compounds represented by the formulas (1) and (2). For example, when the uncured composition contains a plurality of curable compounds having different m, n, o, and p in the formulas (1) and (2), the compatibility with the liquid crystal may be improved. is there.

  The composition containing a liquid crystal and a curable compound may contain a curing catalyst. In the case of photocuring, a photopolymerization initiator generally used for photocurable resins such as benzoin ether, acetophenone, and phosphine oxide can be used. In the case of thermosetting, a curing catalyst such as peroxide, thiol, amine, or acid anhydride can be used depending on the type of curing site, and if necessary, a curing aid such as amines can be added. It can also be used.

  The content of the curing catalyst is preferably 20% by weight or less of the curable compound to be contained, and more preferably 0.1 to 5% by weight when a high molecular weight or high specific resistance of the cured resin is required after curing. .

  The total amount of the curable compound is preferably 0.1 to 20% by mass with respect to the uncured composition. If it is less than 0.1% by mass, the liquid crystal layer cannot be divided into domain structures having an effective shape by the curable compound, and desired transmission-scattering characteristics cannot be obtained. On the other hand, if it exceeds 20% by mass, the haze value in the transmissive state tends to increase as in the case of a general polymer dispersed liquid crystal element. More preferably, the content of the curable compound in the uncured composition is 0.5 to 15% by mass, the scattering intensity in the light scattering state is high, and the voltage value at which transmission-scattering is switched is low. Can do.

  As a processing method for aligning liquid crystal molecules so that the pretilt angle is 60 degrees or more with respect to the substrate surface, there is a method using a vertical alignment agent. As a method using a vertical alignment agent, for example, a method using a surfactant, a method of treating a substrate interface with a silane coupling agent containing an alkyl group or a fluoroalkyl group, or SE1211 or JSR manufactured by Nissan Chemical Industries, Ltd. There is a method using a commercially available vertical alignment agent such as JALS-682-R3 manufactured by the company. In order to create a state in which the liquid crystal molecules are tilted in an arbitrary direction from the vertical alignment state, any known method may be adopted. The vertical alignment agent may be rubbed. Further, a method may be employed in which a slit is provided in the transparent electrodes 101 and 107 or a triangular prism is disposed on the electrodes 101 and 107 so that the voltage is applied obliquely to the substrates 101 and 108. Further, it is not necessary to use means for tilting the liquid crystal molecules in a specific direction.

  The thickness of the liquid crystal layer 104 between the two substrates 101 and 108 can be defined by a spacer or the like. The thickness is preferably 1 to 50 μm, more preferably 3 to 30 μm. If the thickness of the liquid crystal layer 104 is too thin, the contrast is lowered, and if it is too thick, the driving voltage tends to increase, which is not preferable in many cases.

  Any known material can be used as the sealing layer 105 as long as it is a highly transparent resin. If a highly transparent resin is used, the transparency of the liquid crystal element can be enhanced over the entire surface.

  The liquid crystal element 1 manufactured as described above can realize a very high response speed with a response time between the light transmission state and the light scattering state being shorter than 5 ms. In addition, the viewing angle dependency is better than a transmission scattering mode by a general polymer dispersion type liquid crystal element, and a very good transmission state can be obtained even when viewed from an oblique direction. it can. For example, when the above-mentioned liquid crystal / polymer composite is used, it is possible to make almost no haze even when viewed at an angle of 40 degrees from the vertical.

  As the size of the liquid crystal element 1, any size can be used, including one with a diagonal length of about 1 cm to about 3 m.

  In the transmissive screen 10, a plurality of liquid crystal elements 1 may be used. Further, in order to increase the impact resistance against the liquid crystal element 1, the upper and lower substrates 101 and 108 may be fixed.

It is preferable to provide an antireflection film or an ultraviolet blocking film on the front and back surfaces of the liquid crystal element 1. For example, by applying AR coating (low reflection coating) made of a dielectric multilayer film such as SiO ₂ or TiO _{2 on} the front and back of the liquid crystal element 1, the reflection of external light on the substrate surface can be reduced, and the contrast Can be further improved.

  In the liquid crystal element 1 described above, when a potential is set in the transparent electrodes 102 and 107, a voltage corresponding to the potential difference is applied to the liquid crystal between the transparent electrodes. FIG. 4 is an explanatory diagram showing the transmittance with respect to the applied voltage (effective value) of the liquid crystal element 1 manufactured as described above.

  The solid line of the graph illustrated in FIG. 4 shows the result of measuring the voltage dependency of the transmittance of the liquid crystal element 1 used in the present invention with a Schlieren optical system having a condensing angle of 5 °. Moreover, the broken line of the graph illustrated in FIG. 4 shows the result of measuring the total transmittance of the liquid crystal element 1 used in the present invention. Here, a method for measuring each transmittance illustrated in FIG. 4 will be described.

  FIG. 5 is an explanatory diagram illustrating a configuration example of a schlieren optical system measuring instrument. The solid line in the graph illustrated in FIG. 4 is a voltage-dependent change in transmittance in a schlieren optical system with a collection angle of 5 °, measured using the measuring device illustrated in FIG.

  Specifically, by calculating the ratio T / T0 between the light intensity T0 when the liquid crystal element (hereinafter, also referred to as a sample) is in the transmissive state and the light intensity T when the liquid crystal element is not in the transmissive state, Measure the degree of scattering. In this measurement, the light intensity measured without putting a sample is T0.

  In the Schlieren optical system measuring device illustrated in FIG. 5, the light emitted from the light source is collimated by Lens 1 and is scattered when the light passes through the sample. Light diffused at a scattering angle of 5 ° (± 2.5 °) or more is blocked by an aperture and does not reach the detector. That is, in this measurement method, light with a scattering angle of 5 ° or more out of the light scattered by the sample does not enter the detector, so that the transmittance decreases when the degree of scattering is large.

  As a result of measuring the transmittance in the transmissive state of the liquid crystal element in the present invention (that is, no voltage application), the reflection at the interface between the air and the glass on the two surfaces of the two glass substrates, the reflection at the interface between the glass and the liquid crystal material, and the liquid crystal material The transmittance was 83% due to the influence of absorption due to the above. From this state, when the voltage value of the liquid crystal element is increased by a rectangular wave with a driving frequency of 200 Hz, light scattering occurs from the applied voltage 15V, and the scattering characteristics are almost saturated at 40V.

  As described above, the liquid crystal element 1 is in a light scattering state when a predetermined voltage (for example, 60 V) is applied to the liquid crystal layer 104 that can be in a light transmission state and a light scattering state. On the other hand, when no voltage is applied, the light is transmitted. Further, when the applied voltage (effective value) is an intermediate value between 0 V and 60 V (for example, about 18 V to 35 V), the liquid crystal element 1 is in an intermediate state between a light transmission state and a light scattering state ( Intermediate state).

  When the liquid crystal element 1 is placed in a light scattering state and light representing an image is projected from the projector 2 onto one surface of the liquid crystal element 1, the liquid crystal element 1 scatters the light, thereby causing a high contrast (high contrast) image. Is displayed. In this way, the observer 3 can observe the image from the other surface of the liquid crystal element 1.

  In the present embodiment, in order to maintain the transparency of the screen, the intermediate state of the liquid crystal element 1 is set to a state close to the light transmission state (fine scattering state). At this time, if the transmittance is increased too much, the transparency is improved but the contrast is lowered. If the transmittance is lowered too much, the contrast is increased but the transparency is lowered. Therefore, the transmittance is preferably 60% or more and 70% or less. In the example shown in FIG. 4, when the applied voltage (effective value) is about 23 V, the transmittance of the liquid crystal element 1 is about 70%.

  FIG. 6 is an explanatory diagram showing an example of an integrating sphere used when measuring the total transmittance. The broken line in the graph illustrated in FIG. 4 is the total light transmittance of the liquid crystal element according to the present invention, measured using the measuring device illustrated in FIG.

  In the measuring method using the integrating sphere illustrated in FIG. 6, the measuring window of the integrating sphere for visible light is brought into contact with the light exit surface of the liquid crystal element, and all the light transmitted through the liquid crystal element is guided to the detector, so that the total transmission is achieved. Measure the rate. Here, the total transmittance is defined as a ratio T / T0 between the transmittance T0 when measured without a liquid crystal element and the light intensity T when not in the transmissive state.

  As shown in FIG. 4, in the liquid crystal element 1 according to the present invention, a slight decrease in the total light transmittance is observed by voltage application, but most of the light incident on the liquid crystal element is emitted to the front surface of the element. Recognize. From the above, as shown in FIG. 4, the liquid crystal element according to the present invention can control the light scattering property by the applied voltage and can increase the total light transmittance.

  That is, since the liquid crystal element 1 in the present invention has strong forward scattering, the projected image can be clearly seen on the surface opposite to the surface from which the projector 2 projects light. On the other hand, the projected image is hardly visible on the surface where light is projected from the projector 2.

  In the following description, a case where the liquid crystal element 1 that enters a light scattering state when a predetermined voltage is applied and enters a light transmission state when no voltage is applied will be described. However, the liquid crystal element 1 may be an element that enters a light transmission state when a predetermined voltage is applied and enters a light scattering state when no voltage is applied.

  Next, the driving of the transparent electrode 102 in the liquid crystal element 1 by the PWM method will be described. FIG. 7 is a timing chart showing an example of a method for driving the liquid crystal element 1 in the present embodiment. As shown in FIG. 7, when the liquid crystal element 1 is set to the total scattering state, the scattering signal is continuously turned on in one frame.

  Further, when the liquid crystal element 1 is in an intermediate state between a light transmission state and a light scattering state (that is, an intermediate state, which may be referred to as a halftone), one frame corresponds to a desired transmittance. The scatter signal is turned on for a certain period. Note that the scattering signal ON (scattering signal ON) corresponds to a predetermined voltage being applied between the transparent electrodes 102 and 107, and the scattering signal OFF is a state in which the potential difference between the transparent electrodes 102 and 107 is 0V. It corresponds to. Here, when the transmittance of the liquid crystal element 1 is set to about 70%, the ratio of the scattering signal ON period in one frame is about 1/12.

  Rather than controlling the applied voltage (effective value) to about 23 V using a general voltage modulation method to make the transmittance of the liquid crystal element 1 about 70%, the transmittance is about 70% using the PWM method. Therefore, it is possible to display an image with high contrast while maintaining the light transmission state of the liquid crystal element 1. This is because, when the transmittance is controlled using the PWM method, the light scattering state occurs in a certain period (for example, a period of 1/12 of one frame). The light projected from the projector 2 during this period is scattered in the same way as when the liquid crystal element 1 is in the light scattering state (that is, has a high contrast), so that an image projected during that period remains due to the afterimage effect. It is thought that it is visible.

  Moreover, since the liquid crystal element 1 according to the present embodiment uses the above-described uncured composition, the viewing angle is wide and the haze value from the oblique direction can be kept low. Therefore, even when the transmissive screen according to the present invention is installed at an angled position or is installed at a high position, it is possible to suppress the difficulty in viewing the video.

  Further, the resolution of the image projected on the screen depends on the resolution of the projector. Therefore, the resolution of the projected image can be increased by using a projector having a high resolution.

  As described above, in the present embodiment, the liquid crystal element 1 is an image light projected from the projector 2 in an intermediate state between the light transmission state and the light scattering state (specifically, a slight scattering state). The image is displayed on the surface opposite to the surface on which the light is projected. Therefore, the projected image can be displayed while maintaining high transparency.

  In the present embodiment, the drive circuit 4 drives the electrodes 102 and 107 by the PWM method. At that time, the drive circuit 4 drives the electrodes 102 and 107 with a pulse width that brings the liquid crystal element 1 into an intermediate state between the light transmission state and the light scattering state. In this case, the liquid crystal element 1 is in a light scattering state for a certain period (for example, 1/12 of one frame). Therefore, compared with a general voltage modulation method, the projected image can be displayed with a higher contrast while maintaining the light transmission state of the liquid crystal element 1.

  Hereinafter, the present invention will be described with reference to specific examples, but the scope of the present invention is not limited to the contents described below. In this embodiment, a case where the transmission screen of the present invention is used in a vehicle will be described as an example.

  FIG. 8 is an explanatory diagram showing an example when the transmission screen of the present invention is installed in a vehicle. In the example shown in FIG. 8, a transmissive screen 10 is disposed between the front seat and the rear seat in the car 11, and the projector 2 installed above the car is directed toward the rear seat via the transmissive screen 10. Indicates that the image is projected. That is, the projector 2 projects an image from the front to the rear in the vehicle. Further, the transmission screen 10 is in a slightly scattered state by the drive circuit 4 (not shown).

  At this time, the liquid crystal element 1 of the transmissive screen 10 scatters the light of the image projected from the projector 2, so that the surface opposite to the surface projected on the transmissive screen (that is, the front seat side surface). The image is displayed on the surface (ie, the surface on the rear seat side). Therefore, the person in the back seat can clearly see the projected image while ensuring the front view.

  On the other hand, the front seat person is required not to interfere with the driving of the vehicle by the image projected on the transmission screen 10. Here, the black portion of the image projected on the transmissive screen 10 becomes transparent. Therefore, even when an image is projected on the transmissive screen 10, a rear view can be secured.

  Further, the transmission screen 10 has a property of strong forward scattering and weak backward scattering. Therefore, among the light projected from the projector 2 onto the transmissive screen 10, the amount of light reflected by the transmissive screen 10 to the front seat side can be suppressed. That is, since the reflected light can be suppressed by using the transmissive screen 10, it is possible for the person in the front seat to suppress the troublesomeness caused by the light reflected from the rear.

  FIG. 9 is an explanatory view showing another example when the transmission screen of the present invention is installed in a vehicle. In the example shown in FIG. 9, the transmissive screen 10 is arranged on the rear side of the rear seat in the car 11 (for example, the rear glass portion of the car), and is directed from the projector 2 installed above the car toward the transmissive screen 10. Indicates that the image is projected. That is, also in this case, the projector 2 projects an image from the front to the rear in the vehicle. Further, the transmissive screen 10 illustrated in FIG. 9 is also in a fine scattering state by the drive circuit 4 (not shown).

  Similar to the example shown in FIG. 8, the liquid crystal element 1 of the transmissive screen 10 scatters the light of the image projected from the projector 2, thereby clearly displaying an image showing a sign or an advertisement to the rear vehicle. On the other hand, almost no image can be seen from the inside of the car. In particular, the image can be displayed more clearly at night or in a dark place.

  In addition, for example, when light (light) is illuminated from the rear vehicle on the screen in the total scattering state, the light is widely scattered, so that it is felt dazzling for people in the vehicle. However, since the transmissive screen 10 of the present invention is used in a slightly scattered state, it can reduce glare even when light (light) is illuminated from a rear vehicle, compared to the case of a fully scattered state.

  As mentioned above, although the case where the transmission type screen 10 of this invention was used in a vehicle was demonstrated to the example, the transmission type screen 10 of this invention can be utilized also for other various uses.

  The transmissive screen 10 of the present invention may be used for a show window, for example. In this case, for example, an image describing the product can be displayed in a superimposed manner on the front surface of the displayed product.

  Further, the transmission screen 10 of the present invention may be used for a game machine. In this case, for example, an image independent of the image displayed as the game screen can be displayed on the game screen.

  Moreover, you may utilize the transmissive screen 10 of this invention for a vending machine. In this case, for example, an arbitrary advertisement can be displayed on the glass on the front surface of the product shelf.

  As described above, the transmission screen 10 of the present invention can be applied to any portion where glass is generally used. For example, the transmission screen 10 of the present invention may be used for a window in a general home.

1 Liquid crystal element 2 Video projector (projector)
DESCRIPTION OF SYMBOLS 3 Observer 4 Drive circuit 10 Transmission type screen 11 Car 101,108 Glass substrate 102,107 Transparent electrode 103,106 Alignment film 104 Liquid crystal layer 105 Sealing layer

Claims (4)

A transmissive screen for displaying an image projected from an image projection device,
A liquid crystal / polymer composite layer is sandwiched between a pair of transparent substrates with electrodes, and includes a liquid crystal element capable of taking an intermediate state between a light transmission state and a light scattering state according to an applied voltage. ,
The liquid crystal element scatters light of an image projected from the image projection device in the intermediate state, and displays the image on a surface opposite to the projected surface. Mold screen. A drive circuit for driving the electrodes sandwiching the liquid crystal / polymer composite layer by a pulse width modulation method;
The transmissive screen according to claim 1, wherein the drive circuit drives the electrode with a pulse width that causes the liquid crystal element to be in an intermediate state between a light transmission state and a light scattering state. 3. The transmissive screen according to claim 1, wherein the liquid crystal element has a transmittance of 60% or more and 70% or less as an intermediate state between the light transmission state and the light scattering state. An image projection device for projecting an image from the front to the rear in the vehicle;
A transmissive screen for displaying an image projected from the image projection device,
The transmissive screen has a liquid crystal / polymer composite layer sandwiched between a pair of transparent substrates with electrodes, and takes an intermediate state between a light transmission state and a light scattering state according to an applied voltage. Including a liquid crystal element capable of
The liquid crystal element scatters light of a video projected from the video projection device in the intermediate state and displays the video on a surface opposite to the projected surface. Display device.

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