JP7449384B2 - Transparent screens for aquariums, aquariums, and transparent image display systems - Google Patents

Description

The present invention relates to a transparent screen for an aquarium that displays projected light projected from a projector as a projected image to an observer by being attached to an aquarium, an aquarium to which the transparent screen for an aquarium is attached; The present invention also relates to a transparent image display system using this aquarium.

Transparent screens that project and display information such as advertisements on show windows and information boards of commercial buildings in cities while maintaining light transparency have been attracting attention in the architectural field in recent years.
Furthermore, in addition to the field of architecture, the use of transparent screens as displays for projecting location information etc. onto the windshield of automobiles has been actively researched in recent years, and is attracting attention in the field of automobiles as well.

Among these, products that include a transparent screen in which light scatterers are dispersed in a transparent dispersion medium and a window base material such as a glass window base material are attracting attention from the viewpoint of screen transparency and image sharpness. There is. As examples of transparent screens studied, resin coatings in which fine particles such as diamond and silica are dispersed are known as disclosed in Patent Document 1, Patent Document 2, and Patent Document 3.

Japanese Patent Application Publication No. 2016-177245 Re-publication WO2008-016088 publication Japanese Patent Application Publication No. 2011-113068

In the building and automobile fields, window base materials are firmly fixed to the installation location and cannot be easily separated or dismantled.
On the other hand, screen films are often laminated to window substrates later, if necessary. In addition, if the screen film becomes unnecessary or needs to be replaced due to staining, etc., it is desirable to promptly remove the screen film and return the window base material to the same state as before the screen film was installed. .

By the way, conventionally, glass has been frequently used as a window base material. However, resin window base materials are sometimes used with emphasis on weight reduction, freedom of shape, and toughness. For example, a window base material made of acrylic resin has been proposed as a material that can withstand long-term use and has sufficient transparency.

Among window substrates made of acrylic resin, the challenges when using a transparent screen attached to an acrylic board for an aquarium, especially in an aquarium, include high transmittance and no bubble formation during the period of use. . Note that the generation of bubbles refers to air entering between the transparent screen and the aquarium acrylic board during use, resulting in a state where bubbles appear.
Furthermore, after using the transparent screen for a long period of time, it is also conceivable to peel off the screen in order to replace or remove the screen. Here, when the conventional transparent screen is removed, the transparent screen itself is peeled off, but only the adhesive remains on the aquarium acrylic plate, which is a so-called adhesive residue problem.
Acrylic panels for aquariums require high transmittance so that schools of fish can be viewed from indoors, and are extremely expensive because they are stacked several tens of centimeters thick to withstand tens of tons of water pressure. Therefore, once installed, the aquarium itself will not be replaced. Therefore, transparent screens used in aquariums are required to solve this problem of adhesive residue.

As a result of intensive studies using various adhesives on acrylic plates for aquariums, we found that in order to suppress the generation of bubbles, and to be removable so that no adhesive remains on the acrylic plates for aquariums when peeled off. It was found that the adhesive layer of a transparent screen for commercial use requires the following performance.
That is, in order to achieve the above objective, (1) the initial adhesive strength is 3.0 N/25 mm or more, and (2) the increase in adhesive strength after aging is suppressed, and the adhesive strength after aging is 4. It has been found that a range of .0 to 20.0 N/25 mm is required. If these requirements are met, a transparent screen for an aquarium that can be used as an acrylic board for an aquarium can be obtained.
In addition, the adhesive layer of the transparent aquarium screen must have (3) an initial adhesive force of 10 N/25 mm or less, and (4) a storage modulus of the adhesive layer of 1.0 × 10 ⁵ to 1.0 × 10 ⁸ Pa. It was also found that (5) the internal haze is preferably less than 0.8% in order to obtain high visibility.

That is, in order to achieve the above object, the present invention has the following configuration.
[1] A transparent screen for an aquarium comprising an adhesive layer, a transparent support, and a light reflective layer in this order,
The total light transmittance is 70% or more,
The adhesive layer has an initial adhesive strength of 3.0 N/25 mm or more, and an adhesive strength over time of 4.0 to 20. 0N/25mm,
A transparent screen for an aquarium that is attached to an acrylic board for an aquarium via an adhesive layer and displays an image on the projection side by reflecting the projection light projected from a projector.
[2] The transparent screen for an aquarium according to [1], wherein the adhesive layer has an initial adhesive force of 10 N/25 mm or less.
[3] The transparent screen for an aquarium according to [1] or [2], wherein the adhesive layer has a storage modulus of elasticity at 25° C. of 1.0×10 ⁵ to 1.0×10 ⁸ Pa.
[4] Any one of [1] to [3], wherein at least one of the light-reflecting layers has a cholesteric liquid crystal layer, all cholesteric liquid crystal layers have the same helical sense, and further satisfies the following formula (1). Transparent screen for aquarium described in Crab.
R[-45,30](550)/R[-45,15](550)≧1.3 Formula (1)
Here, R[-45,30] (550) is the polar angle 30 at an azimuth angle deviated by 180 degrees from the azimuth angle of the incident light for incident light at a polar angle of -45 degrees to the transparent screen for an aquarium. R[-45,15] (550) represents the reflectance at a wavelength of 550 nm, measured at a reception angle of °, and R[-45,15] (550) is the incident light at a polar angle of -45 ° to the transparent screen for an aquarium. It represents the reflectance at a wavelength of 550 nm, measured at a reception angle of 15 degrees polar angle at an azimuth angle deviated by 180 degrees from the azimuth angle of .
[5] The transparent screen for an aquarium according to any one of [1] to [4], further comprising a protective film on the side opposite to the transparent support of the adhesive layer.
[6] An aquarium in which the transparent screen for an aquarium according to any one of [1] to [5] is bonded to the surface of an aquarium made of an acrylic plate for an aquarium using an adhesive layer.
[7] A transparent image display system that projects light onto the aquarium according to [6] from a viewing side using a projector, thereby displaying an image formed by the projected light of the projector so as to be superimposed on the aquarium.

According to the present invention, there is provided a transparent screen for an aquarium that can be used for an acrylic board for an aquarium for a long period of time without any problem, an aquarium having this transparent screen for an aquarium, and a transparent image display system using this aquarium. .

FIG. 1 is a block diagram of a transparent screen for an aquarium having a cholesteric reflective layer. FIG. 2 is a diagram showing the configuration of a transparent screen for an aquarium having an optically shaped layer and a light reflecting layer. FIG. 3 is a diagram showing the configuration of a transparent screen for an aquarium having a light-reflecting layer.

Hereinafter, the transparent screen for an aquarium, the aquarium, and the transparent image display system of the present invention will be explained in detail.
Although the description of the constituent elements described below may be made based on typical embodiments of the present invention, the present invention is not limited to such embodiments.

The transparent screen for an aquarium of the present invention has an adhesive layer, a transparent support, and a light reflective layer in this order. The transparent screen for an aquarium of the present invention can be attached (attached) to an aquarium by having the adhesive layer attached to an acrylic plate for an aquarium (acrylic resin for an aquarium, acrylic base material for an aquarium) constituting the aquarium. .
Such a transparent screen for an aquarium of the present invention reflects the projection light projected from the projector, so that, for example, a customer visiting an aquarium can observe the inside of the aquarium and the image projected by the projector in a superimposed state. This is what makes it possible.

As described above, the transparent screen for an aquarium of the present invention is bonded to an acrylic plate for an aquarium forming an aquarium using an adhesive layer.
The acrylic board for an aquarium to which the transparent screen for an aquarium of the present invention is laminated is carefully cleaned of surface dirt, etc. before being laminated with the transparent screen for an aquarium in order to ensure adhesion with the transparent screen for an aquarium. It is preferable to keep it.

Acrylic plates for aquariums are usually used in a rectangular shape, but may be in other shapes, such as circular, elliptical, triangular, and other various shapes.

The size of the acrylic plate for an aquarium is determined as appropriate depending on the purpose of the aquarium. Further, the thickness is usually set depending on the purpose, for example, the strength required in the mode of use.

[Light reflective layer]
As the light reflecting layer, a wide variety of known ones can be used as long as it is a layer that can make the projected light projected from the projector visible to the viewer as an image.
A preferred example is a transparent layer in which a light scattering material is dispersed in a transparent dispersion medium.
Examples of transparent dispersion media include organic polymers and inorganic oxide polymers.
Examples of organic polymers include polyester resins, polycarbonate resins, polyacrylic resins, polystyrene resins, polyarylate resins, polyolefin resins, polyvinyl chloride resins, polyvinylidene chloride resins, polysulfone resins, polyethersulfone resins, diacetyl cellulose resins, Examples include triacetyl cellulose resin, ethylene vinyl alcohol copolymer, polyvinyl alcohol resin, and polyvinyl butyral resin.
Furthermore, inorganic oxide polymers are inorganic oxides that are polymerized into a network of atoms such as silicon, titanium, zirconium, iron, zinc, tin, hafnium, and tungsten through oxygen atoms. It is a polymer. Examples of inorganic oxide polymers include those using silicon oxides such as silica, alumina, titania, zirconia, iron oxide, zinc oxide, tin oxide, hafnium oxide, tungsten oxide, etc. as raw materials or starting materials. can. Moreover, these can also be used as a mixture.

Examples of light scatterers include low refractive index particles such as hollow silica beads and hollow resin beads, and high refractive index particles such as titanium oxide, zirconium oxide, iron oxide, tin oxide, barium titanate and diamond. It will be done.
Among these, titanium oxide particles, zirconium oxide particles, and diamond particles are preferably exemplified. Since these particles have a high refractive index and strong light scattering properties, they are preferable for use as a light scatterer in a transparent screen for an aquarium because they can provide both transparency and image sharpness.

Further, as another preferred light-reflecting layer, a light-reflecting layer in which light-reflecting fine particles are dispersed can also be used.
As an example, the light reflecting layer described in paragraphs [0033] to [0045] of International Publication No. 2017/94550 is exemplified. This light-reflecting layer includes a transparent binder and light-reflecting fine particles.
This light-reflecting layer is composed of light-reflecting fine particles dispersed in a transparent binder that are aggregated in an appropriate size, and while maintaining transparency, it anisotropically scatters and reflects the projected light projected from the projector. It can be projected. When this light-reflecting layer is used as a light-reflecting layer of a transparent screen for an aquarium, it has excellent transparency and color reproducibility, and has high brightness, allowing images to be clearly viewed.

In the transparent aquarium screen of the present invention, a particularly preferred example of the light-reflecting layer is a light-reflecting layer having a cholesteric liquid crystal layer. In other words, the cholesteric liquid crystal layer is a layer containing a cholesteric liquid crystal structure. The cholesteric liquid crystal layer is a layer formed by fixing a cholesteric liquid crystal phase in which a liquid crystal compound is cholesterically aligned.
Transparent screens and the like having a cholesteric liquid crystal layer are described in detail in, for example, Japanese Patent Application Publication No. 2018-200459, etc., but the parts particularly necessary for transparent screens for aquariums will be supplemented below.

FIG. 1 conceptually shows an example of a transparent screen for an aquarium according to the present invention, which has a cholesteric liquid crystal layer as a light reflection layer.
The transparent screen for an aquarium shown in FIG. 1 includes, from the bottom in the figure, a first adhesive layer 6, a first transparent support 5, a second adhesive layer 4, a second transparent support 3, an alignment layer 2, and a light reflective layer. 1. The light reflecting layer 1 has a cholesteric liquid crystal layer.
In the transparent screen for an aquarium shown in FIG. 1, the first adhesive layer 6 is the adhesive layer in the transparent screen for an aquarium of the present invention, and the first transparent support 5 is the transparent support in the transparent screen for an aquarium of the present invention. It is. Therefore, in the aquarium transparent screen shown in FIG. 1, the projection light (image light, projection light) from the projector is projected from the light reflective layer 1 side.
Although not shown in FIG. 1, the transparent screen for an aquarium of the present invention may be produced using a removable support.
For example, a reflective layer laminate is prepared in which an alignment layer 2 is formed on the surface of the second transparent support 3 and a light reflective layer 1, that is, a cholesteric liquid crystal layer is formed on the surface of the alignment layer 2. A releasable support is laminated to the reflective layer 1. On the other hand, an adhesive sheet is prepared in which the first adhesive layer 6 is formed on one side of the first transparent support 5 and the second adhesive layer 4 is formed on the other side. Preferably, an easily peelable protective film is attached to the adhesive layer of the adhesive sheet.

In addition, when the light reflection layer 1 has a cholesteric liquid crystal layer, the transparent screen for an aquarium of the present invention may optionally include a retardation layer or It may have a retardation layer and a linear polarizer.
The retardation layer is placed closer to the incident side of the projection light than the cholesteric liquid crystal layer, and the linear polarizer is placed closer to the incident side of the projected light than the retardation layer.
Various known retardation layers and linear polarizers can be used.

In the transparent screen for an aquarium shown in FIG. 1, a light reflecting layer 1 (cholesteric liquid crystal layer) is formed on a second transparent support 3 and an alignment layer 2.
The second transparent support 3 supports the alignment layer 2 and the light reflection layer 1. The second transparent support 3 is not limited to any material, and any transparent material used in known light-transmitting optical members having a cholesteric liquid crystal layer, such as various resin films, can be used as long as it has sufficient light transmittance. A variety of supports are available.
The alignment layer 2 is for aligning a liquid crystal compound forming a cholesteric liquid crystal layer which becomes the light reflection layer 1. The alignment layer 2 is also not limited, and various known alignment layers (alignment films) used in known light-transmitting optical members having cholesteric liquid crystal layers, such as resin films subjected to rubbing treatment, can be used. It is possible.

As an example, the transparent screen for an aquarium shown in FIG. 1 includes a laminate in which the alignment layer 2 is formed on the surface of the second transparent support 3 and the light reflective layer 1 is formed on the surface of the alignment layer 2, as described above. This laminate is then bonded with the second transparent support 3 side facing the second adhesive layer 4 side.
The second adhesive layer 4 is not limited to any particular material, and may be a known light-transmissive optical member such as an adhesive used in a commercially available double-sided adhesive sheet or a transparent optical adhesive (OCA (Optical Clear Adhesive)). Various known adhesives can be used.
Note that the adhesive suitable for the second adhesive layer 4 will be described in detail later. Moreover, in the transparent screen for an aquarium shown in FIG. 1, a double-sided adhesive sheet having adhesive layers on both sides of a resin film can also be used. This point will also be explained in detail later.

In addition, in the transparent screen for an aquarium of the present invention, the alignment layer 2 and the second transparent support 3 are not essential components. That is, the transparent screen for an aquarium of the present invention may have a structure in which the light reflecting layer 1 is directly bonded to the second adhesive layer 4. Moreover, the transparent screen for an aquarium of the present invention may have a structure in which a laminate of the alignment layer 2 and the light reflection layer 1 is bonded to the second adhesive layer 4. Further, in the transparent screen for an aquarium of the present invention, the second adhesive layer 4 is also not an essential component.
As an example of this configuration, in the method using the above-mentioned peelable support, a laminate in which the second transparent support 3, the alignment layer 2, and the light reflection layer 1 are formed is prepared, and the light reflection layer 1 is provided with the peelability support. After laminating the bodies, the second transparent support 3 or the alignment layer 2 may be peeled off, and then the second adhesive layer 4 may be laminated.
That is, the transparent screen for an aquarium of the present invention may have a structure in which the light reflecting layer 1 is directly formed on the first transparent support 5, as shown in FIG. 3 described later.

[Cholesteric liquid crystal layer]
In the transparent screen for an aquarium, the light reflecting layer may include one or more cholesteric liquid crystal layers.
Other layers such as alignment layers and adhesive layers may be included between the two or more cholesteric liquid crystal layers. Furthermore, other layers such as a base layer and a transparent layer may be included between the cholesteric liquid crystal layer and the retardation layer.

(Cholesteric liquid crystal structure)
The cholesteric liquid crystal structure may be any structure as long as the orientation of the liquid crystal compound in the cholesteric liquid crystal phase (cholesteric liquid crystal alignment) is maintained. A cholesteric liquid crystal layer typically has a structure in which a polymerizable liquid crystal compound is oriented in a cholesteric liquid crystal phase, and then polymerized and hardened by ultraviolet irradiation, heating, etc., resulting in a non-flowable state. In addition, any structure may be used as long as the orientation state does not change due to an external field, an external force, or the like.
Note that in the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound does not need to exhibit liquid crystallinity anymore. 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 in which it selectively reflects circularly polarized light in one sense of right-handed circularly polarized light or left-handed circularly polarized light, and transmits circularly polarized light in the other sense. In this specification, circularly polarized light selective reflection may also be simply referred to as selective reflection.
Many films formed from compositions containing polymerizable liquid crystal compounds have been known as films including a layer in which a cholesteric liquid crystal phase that exhibits selective reflection of circularly polarized light is fixed. You can refer to the technology.

The center wavelength λ of selective reflection of the cholesteric liquid crystal layer depends on the pitch P (=period of the helix) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal structure and λ=n×P.
Note that in this specification, the center wavelength λ of selective reflection possessed by the cholesteric liquid crystal layer means the wavelength located at the center of gravity of the reflection peak of the circularly polarized light reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer.

As can be seen from the above relationship λ=n×P, by adjusting the pitch of the helical structure (helical pitch), the center wavelength λ of selective reflection of the cholesteric liquid crystal layer can be adjusted. The cholesteric liquid crystal layer that exhibits selective reflection in the visible light region preferably has a center wavelength for selective reflection also in the visible light region. For example, adjusting the values of n and/or P in order to selectively reflect either right-handed circularly polarized light or left-handed circularly polarized light in response to red light, green light, and blue light, The center wavelength λ can be adjusted.

The transparent screen for an aquarium of the present invention does not produce a clear double image unlike the display of a projected image using a virtual image, but diffuse reflection occurs when the light reflected on the aquarium surface re-enters the transparent screen. As a result, image blurring occurs and clarity deteriorates.
Therefore, when using the transparent screen for an aquarium of the present invention by laminating it on the surface of an acrylic board for an aquarium, it is necessary to reduce image blurring caused by reflected light from the front or back surface of the acrylic board for an aquarium. It is preferable to bond the cholesteric liquid crystal layer (light reflection layer) to an acrylic plate for an aquarium so that light is obliquely incident on the cholesteric liquid crystal layer (light reflection layer). Alternatively, it is preferable to set the projection direction of the projection light from the projector so that the light is obliquely incident on the cholesteric liquid crystal layer.
Further, when light obliquely enters the cholesteric liquid crystal layer in this manner, the center wavelength of selective reflection shifts to the shorter wavelength side due to so-called blue shift. Therefore, with respect to the selective reflection wavelength required to display the projected image, n×P must be adjusted so that λ, which is calculated according to the above formula λ=n×P, is on the long wavelength side. is preferred.
When λ _d is the center wavelength of selective reflection when a light ray passes through a cholesteric liquid crystal layer with a refractive index of n ₂ at an angle of θ ₂ with respect to the normal direction of the cholesteric liquid crystal layer, λ _d is expressed by the following formula. It is expressed as The normal direction of the cholesteric liquid crystal layer is the helical axis direction of the cholesteric liquid crystal layer.
λ _d = n ₂ ×P × cos θ ₂

For example, suppose that a cholesteric liquid crystal layer and a retardation layer A having a λ/2 retardation are used as the light reflection layer 1.
In this case, the light incident from the retardation layer A side that has a λ/2 phase difference at an angle of 45° to 70° with respect to the normal line of the projected image display area in air with a refractive index of 1 is usually refracted. The light passes through the retardation layer A with a retardation index of about 1.45 to 1.80 at an angle of 23° to 40° with respect to the normal to the projected image display area, and enters the cholesteric liquid crystal layer with a refractive index of about 1.61. In the cholesteric liquid crystal layer, light is transmitted at an angle of 26° to 36°, so n×P can be adjusted by inserting this angle and the desired center wavelength of selective reflection into the above equation.
Since the helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound or its concentration, a desired helical pitch can be obtained by adjusting these factors. For measuring the helical sense and pitch, please refer to the methods described in "Introduction to Liquid Crystal Chemistry Experiments," edited by the Japan Liquid Crystal Society, published by Sigma Publishing, 2007, p. 46, and "Liquid Crystal Handbook," Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196. Can be used.

By adjusting the center wavelength λ of selective reflection of the cholesteric liquid crystal layer used in accordance with the emission wavelength range of the light source used for projection and the usage conditions of the cholesteric liquid crystal layer, clear projection with good light utilization efficiency can be achieved. Can display images.
In particular, when having multiple cholesteric liquid crystal layers, the center wavelength λ of selective reflection of each cholesteric liquid crystal layer can be adjusted according to the emission wavelength range of the light source used for projection, etc. It is efficient and can display clear color projected images.
The state of use of the cholesteric liquid crystal layer includes the angle of incidence of the projected light onto the cholesteric liquid crystal layer (projection direction), the direction in which the projected image is observed, and the like.

As the cholesteric liquid crystal layer, a cholesteric liquid crystal layer whose spiral sense is either right or left is used. The sense of circularly polarized light reflected by the cholesteric liquid crystal structure corresponds to the sense of the spiral of the cholesteric layer (cholesteric liquid crystal phase).
The helical senses of the cholesteric liquid crystal layers having different center wavelengths of selective reflection may be all the same or may include different senses, but preferably the same.

In the cholesteric liquid crystal layer, the half-width Δλ (nm) of the selective reflection band exhibiting selective reflection depends on the birefringence Δn of the liquid crystal compound and the above-mentioned helical pitch P, and follows the relationship Δλ=Δn×P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn.
Adjustment of Δn can be carried out by adjusting the type and mixing ratio of the polymerizable liquid crystal compound, or by controlling the temperature at the time of fixing the orientation.
The half width Δλ of selective reflection may be any one of 15 to 200 nm, 15 to 150 nm, 20 to 100 nm, and the like.

The cholesteric liquid crystal layer used in the present invention preferably has a liquid crystal compound fixed in a cholesteric alignment state.
The cholesteric alignment state may include an alignment state that reflects right-handed circularly polarized light, an alignment state that reflects left-handed circularly polarized light, or both. The liquid crystal compound used in the present invention is not particularly limited, and various known compounds can be used.

As is well known, a cholesteric liquid crystal layer has a striped pattern of bright and dark areas when its cross section is observed using a scanning electron microscope (SEM).
In the transparent screen for an aquarium of the present invention, when the reflective layer has a cholesteric liquid crystal layer, the striped pattern of the cholesteric liquid crystal layer preferably has a wavy structure. The wavy structure preferably has an average peak-to-peak distance of 0.5 to 50 μm. The average value of the distance between the peaks of the wavy structure is more preferably 1.5 to 30 μm, and even more preferably 2.5 to 20 μm.
In a typical cholesteric liquid crystal layer, the bright portion and the dark portion are parallel to the main surface of the cholesteric liquid crystal layer, that is, the plane on which the cholesteric liquid crystal layer is formed. Note that the main surface is the largest surface of a layer (film, plate-like object, sheet-like object). Such a normal cholesteric liquid crystal layer specularly reflects incident light.
On the other hand, a cholesteric liquid crystal layer whose bright and dark areas have a wavy structure diffusely reflects the incident light (scattered reflection). Because the cholesteric liquid crystal layer, that is, the reflective layer, diffuses and reflects light, the transparent screen for aquariums of the present invention provides clear images with sufficient brightness when observed not only from the front but also from the side and from above and below. becomes possible to observe.

In the present invention, the wavy structure specifically refers to at least one area M in which the absolute value of the inclination angle with respect to the main surface of the cholesteric liquid crystal layer is 5° or more in a continuous line of bright or dark areas of a striped pattern. It means that there are two peaks or valleys with an inclination angle of 0° that are located at the closest positions with the region M in between.

The peaks or valleys with an inclination angle of 0° include convex and concave shapes, but also include step-like and shelf-like points when the inclination angle is 0°. In the wavy structure, it is preferable that a region M having an absolute value of an inclination angle of 5° or more and a plurality of peaks or valleys sandwiching the region repeat in a continuous line of bright or dark regions of the striped pattern.

In addition, the distance between the peaks of the wavy structure is defined as the distance in the plane direction of the cholesteric liquid crystal layer between two peaks or troughs with an inclination angle of 0° located at the closest positions across the region M. The value is the arithmetic average of the length in the long axis direction of the cross section of 100 μm and the total film thickness.

Here, if each continuous line touches either of both interfaces of the film and is interrupted, both ends of the interrupted point are not considered to be peaks or valleys. Further, if each continuous line has a bent structure as shown in FIG. 2, which will be described later, the continuous line is considered to be interrupted at that point, and both ends thereof are not considered to be mountains or valleys.

As described above, in the transparent aquarium screen of the present invention, the reflective layer preferably has at least one cholesteric liquid crystal layer.
In this case, it is preferable that the helical sense of all the cholesteric liquid crystal layers, that is, the direction of rotation of the selectively reflected polarized light, be the same. Furthermore, it is preferable that the following formula (1) is satisfied.
R[-45,30](550)/R[-45,15](550)≧1.3 Formula (1)
In this equation (1), R[-45,30] (550) is defined as R[-45,30] (550) at an azimuth angle that is 180° shifted from the azimuth angle of the incident light for the incident light at a polar angle of -45° to the transparent screen for an aquarium. It represents the reflectance at a wavelength of 550 nm, measured at a polar angle of 30°.
On the other hand, R[-45,15] (550) is a polar angle of 15 degrees at an azimuth angle that is 180 degrees off from the azimuth of the incident light for incident light at a polar angle of -45 degrees to the transparent screen for an aquarium. It represents the reflectance at a wavelength of 550 nm, measured at a light receiving angle of .
In other words, the above equation (1) shows that even for light incident at the same polar angle of -45°, the reflectance when the light is received at a polar angle of 30° is 1.3 times the reflectance when the light is received at a polar angle of 15°. This shows that the above is true.
By satisfying this formula (1), the transparent screen for an aquarium of the present invention exhibits good diffuse reflection properties. As a result, as described above, it becomes possible to suitably observe the projected image regardless of the viewing direction, such as up, down, left, or right.

[Adhesive layer]
In the transparent screen for an aquarium of the present invention, the adhesive layer (first adhesive layer 6 in FIG. 1) bonded to the acrylic board for an aquarium is:
(1) The initial adhesive strength is 3.0N/25mm or more, and
(2) Suppressing the increase in adhesive strength over time, i.e. adhesive strength after 4 days under conditions of temperature 85°C and humidity 10% RH of 4.0 to 20.0N/25mm. Satisfy the range.
The transparent screen for an aquarium of the present invention has an adhesive layer that satisfies this condition, which suppresses the generation of bubbles over time, and furthermore, when the transparent screen for an aquarium is peeled off from the acrylic board for an aquarium after long-term use, the adhesive layer satisfies this condition. This prevents adhesive residue from remaining on the acrylic board.
Furthermore, in the aquarium transparent screen, preferably the adhesive layer is
(3) The initial adhesive strength is 10N/25mm or less,
(4) The storage modulus at 25°C is in the range of 1.0×10 ⁵ to 1.0×10 ⁸ Pa, and
(5) The internal haze is less than 0.8%.

The material constituting the adhesive layer described above is not particularly limited, but it is preferably a material that does not impede the transparency of the transparent aquarium screen.
Examples of compositions that can form such an adhesive layer include adhesive compositions using commonly used materials such as acrylic, silicone, urethane, and rubber materials. Among these, acrylic pressure-sensitive adhesive compositions are preferred because they have excellent transparency.

As a preferred example, the adhesive composition includes a crosslinking agent and a polymer having a reactive functional group that is a functional group that can react with the crosslinking agent, and the crosslinking agent and the crosslinkable polymer form a crosslinked structure. Examples include those that form an adhesive layer. In this specification, "a polymer having a reactive functional group that is a functional group that can react with a crosslinking agent" is also referred to as a "crosslinkable polymer."

(i) Crosslinkable Polymer From the viewpoint of further reducing the amount of outgas, the crosslinkable polymer is preferably an acrylic polymer with a reduced content of carboxyl groups. Specifically, the content of carboxyl groups in the crosslinkable polymer is such that the structural unit having a carboxyl group is 1.0 parts by mass or less per 100 parts by mass of the total monomers for forming the crosslinkable polymer. The amount is preferably 0.5 parts by mass or less, and more preferably 0.5 parts by mass or less. Furthermore, it is preferable that the crosslinkable polymer is an acrylic polymer having no carboxyl group. In this specification, "acrylic polymer having no carboxyl group" is also referred to as "carboxyl group-free polymer."
Similarly, the adhesive layer constituting the transparent aquarium screen of the present invention preferably has a low content of carboxyl groups, and more preferably does not substantially contain components having carboxyl groups. Examples of the structural unit having a carboxyl group include acrylic acid, methacrylic acid, and itaconic acid.

The constituent units of the crosslinkable polymer are not particularly limited.
The crosslinkable polymer may be composed only of structural units based on an acrylic compound, which is one or more compounds having a (meth)acryloyl group and its derivatives (ester, acrylonitrile, etc.), It may contain a structural unit based on an acrylic compound and a structural unit based on a compound other than an acrylic compound.
In addition, the "(meth)acryloyl group" in this specification means both an acryloyl group and a methacryloyl group. In this regard, the same applies to other similar terms. Moreover, the compounds other than the above-mentioned acrylic compounds may be composed of one type of compound, or may be composed of multiple types of compounds.

A preferable example of the above-mentioned acrylic compound is (meth)acrylic acid ester.
Specific examples of (meth)acrylic acid esters include chain skeletons such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth) ) acrylate, (meth)acrylate with a cyclic skeleton such as tetrahydrofurfuryl (meth)acrylate and imide acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate , (meth)acrylates having hydroxyl groups such as 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and amino groups such as N-methylaminoethyl (meth)acrylate. and (meth)acrylates having an epoxy group such as glycidyl (meth)acrylate.

Among these, the crosslinkable polymer preferably contains a structural unit based on an alkyl (meth)acrylate in which the alkyl group has 4 or less carbon atoms. In this specification, "alkyl (meth)acrylate whose alkyl group has 4 or less carbon atoms" is also referred to as "lower alkyl compound".
Specifically, such lower alkyl compounds include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Examples include acrylate, sec-butyl (meth)acrylate, and tert-butyl (meth)acrylate.

Among these, n-butyl (meth)acrylate, methyl (meth)acrylate, etc. are used from the viewpoint of facilitating the appropriate balance between increasing the adhesive properties of the adhesive layer and reducing the amount of outgas. preferable. One type of lower alkyl compound may be used alone, or two or more types may be used in combination.

Examples of monomers providing structural units based on compounds other than acrylic compounds include olefins such as ethylene and norbornene, carboxylic acid vinyl esters such as vinyl acetate, and aromatic compounds having ethylenically unsaturated bonds such as styrene. In this specification, "a monomer providing a structural unit based on a compound other than an acrylic compound" is also referred to as "other polymerizable compound."

The reactive functional group that the crosslinkable polymer has is preferably a functional group that reacts with the crosslinking agent described below. Examples of such functional groups other than carboxyl groups include hydroxyl groups, amino groups, and amide groups.

The type of compound that provides the structural unit having a reactive functional group in the crosslinkable polymer is not particularly limited.
Examples include the above-mentioned (meth)acrylates having a hydroxyl group and (meth)acrylates having an amino group. Examples of ethylenically unsaturated compounds having such a reactive functional group include ethylenically unsaturated compounds containing an amide group and alcohols having a vinyl group. In this specification, "ethylenic unsaturated compound having a reactive functional group" is also referred to as "reactive compound."
Specific examples of such reactive compounds include acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, 5-hexen-1-ol, 5-hexen-3 -ol, 4-penten-1-ol, and the like.

The reactive functional group possessed by the reactive compound is preferably a hydroxyl group, which is less likely to discolor due to heat or the like. Therefore, the reactive compound is preferably a (meth)acrylate having a hydroxyl group and/or an alcohol having a vinyl group.

The crosslinkable polymer may contain a structural unit based on a compound having an ethylenically unsaturated bond other than the structural unit based on the above-mentioned lower alkyl compound and the structural unit based on the reactive compound. Specific examples of monomers providing such structural units include olefins, carboxylic acid vinyl esters, and aromatics having ethylenically unsaturated bonds, as in the case of the other polymerizable compounds mentioned above.

When such a crosslinkable polymer contains a structural unit based on a lower alkyl compound and a structural unit based on a reactive compound, the content ratio of these structural units in terms of monomer mass in the crosslinkable polymer (lower alkyl compound: reactive compound) (compound) is preferably 90:10 to 99.9:0.1, more preferably 95:5 to 99.5:0.5.
By setting the above-mentioned ratio within this range, the stress residual rate of the resulting adhesive layer containing a crosslinked structure based on the crosslinkable polymer can be easily set within a suitable range.

The crosslinkable polymer used in the adhesive layer may further include a structural unit based on a morpholine compound containing an ethylenically unsaturated group. In this specification, "ethylenic unsaturated group-containing morpholine compound" is also referred to as "morpholine compound".
Since the morpholine group has the function of promoting the reaction of the crosslinking agent described below, by including a structural unit based on a morpholine compound, the crosslinkable polymer becomes a polymer having a functional group with the function of promoting crosslinking. . In this case, the crosslinking density of the adhesive layer can be increased while reducing the possibility of outgassing compared to the case where a low molecular weight crosslinking accelerator described below is contained, which is preferable.
Specific examples of morpholine compounds include N-vinylmorpholine, N-allylmorpholine, and N-(meth)acryloylmorpholine. Among the morpholine compounds, N-(meth)acryloylmorpholine, which is also an acrylic compound, is preferred from the viewpoint of good copolymerizability with compounds related to other structural units. One type of morpholine compound may be used, or a plurality of types may be used.

The content of structural units based on morpholine compounds in the crosslinkable polymer for the adhesive layer is based on lower alkyl compounds, from the viewpoint of keeping the stress residual rate within the above range and making it difficult to generate outgas. It is preferably 2 to 30 parts by mass, more preferably 4 to 25 parts by mass, based on 100 parts by mass of the lower alkyl compound content of the structural units and the reactive compound content of the reactive compound-based structural units. preferable.

The crosslinkable polymer for the adhesive layer is a structural unit based on a compound having an ethylenically unsaturated bond other than the above-mentioned structural units based on lower alkyl compounds, structural units based on reactive compounds, and structural units based on morpholine compounds. May include. Specific examples of monomers providing such structural units include olefins, carboxylic acid vinyl esters, and aromatics having ethylenically unsaturated bonds, as in the case of the other polymerizable compounds described above. Alternatively, compounds having a functional group having a crosslinking promotion function like morpholine compounds, such as ethylenically unsaturated group-containing imidazole compounds, are also exemplified.
Although the content of the structural units based on such compounds is not particularly limited, if the content is excessively large, there is a concern that it will become difficult to control the stress residual rate within the above range. Therefore, its content is 10 parts by mass based on 100 parts by mass of the lower alkyl compound content of the structural unit based on the lower alkyl compound and the reactive compound content of the reactive compound based structural unit. The upper limit is preferably 5 parts by mass, and more preferably 5 parts by mass.

(ii) Crosslinking agent As the crosslinking agent, polyvalent isocyanate compounds, melamine compounds, epoxy compounds, and the like can be used. Polyvalent isocyanate compounds are preferably used because they crosslink quickly and do not easily generate low-molecular compounds that cause outgassing and contamination.
As the polyvalent isocyanate compound, hexamethylene diisocyanate, tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, etc. are commercially available and are preferably used.
Further, as the crosslinking agent, polyisocyanate compounds and isocyanurate compounds obtained by addition-reacting these polyvalent isocyanate compounds with trimethylolpropane, etc., as well as bullet-type compounds, etc. can also be used. Furthermore, as a crosslinking agent, urethane prepolymer type polyisocyanates are used, which are obtained by addition-reacting these polyvalent isocyanate compounds with known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. etc. may also be used.

(iii) Other components The adhesive layer can contain various components without departing from the objective of the present invention.
Such components include, for example, crosslinking accelerators, coloring materials such as dyes and pigments, antioxidants such as anilide and phenol, ultraviolet absorbers such as benzophenone and benzotriazole, plasticizers, and antioxidants. , light stabilizers, dispersants, and leveling agents. However, it is preferable that these components do not easily generate outgas and do not impede the transparency of the adhesive layer.

There is no limit to the thickness of the adhesive layer.
Here, if the adhesive layer is too thin, there is a concern that desired adhesive properties may not be obtained, and if the adhesive layer is excessively thick, there is a concern that it will be disadvantageous from the viewpoint of workability.
Therefore, the thickness of the adhesive layer as a whole is usually selected in the range of 4 to 30 μm, preferably in the range of 6 to 25 μm.

In the transparent screen for an aquarium of the present invention, the adhesive layer (first adhesive layer 6 in FIG. 1) bonded to the acrylic board for an aquarium has an initial adhesive strength of 3.0 N/25 mm or more and an adhesive strength over time. , 4.0 to 20.0N/25mm.
In addition, in this invention, the adhesive force (peel force) of an adhesive layer is the adhesive force with respect to the acrylic board for an aquarium (acrylic resin for an aquarium).
Moreover, in the present invention, the adhesive strength over time is the adhesive strength after 4 days have passed under conditions of a temperature of 85° C. and a humidity of 10% RH.
The transparent screen for an aquarium of the present invention has an initial adhesive force of 3.0 N/25 mm or more and an adhesive force over time of 4.0 N/25 mm or more, so that when laminated to an acrylic plate for an aquarium (aquarium), Furthermore, it is possible to prevent air from entering between the aquarium acrylic plate and the aquarium transparent screen during the period of use, thereby preventing air bubbles from being generated. In addition, the transparent screen for aquarium of the present invention has adhesive strength over time of 4.0 to 20.0N/25mm, so that it can be peeled off even after long-term use. It also prevents the adhesive layer from remaining on the aquarium acrylic board when it is peeled off from the acrylic board, so-called adhesive residue.

In the transparent screen for an aquarium of the present invention, the adhesive layer has an initial adhesive force of 3.0 N/25 mm or more. The initial adhesive force of the adhesive layer is preferably 4.0 N/25 mm or more, more preferably 5.0 N/25 mm or more.
If the initial adhesive strength is less than 3.0N/25mm, it will not be possible to prevent air from entering between the aquarium acrylic board and the aquarium transparent screen during use, causing air bubbles to form, and the transparent screen will not be temporarily fixed. When doing so, it tends to peel off due to poor adhesion, reducing workability. Furthermore, by setting the initial adhesive force to 3.0 N/25 mm or more, the transparent screen does not peel off during the step of applying water to the acrylic board for an aquarium.
There is no upper limit to the initial adhesive force of the adhesive layer, but it is preferably 10.0 N/25 mm or less, more preferably 9.0 N/25 mm or less, and even more preferably 8.0 N/25 mm or less.
By setting the initial adhesive force of the adhesive layer to 10.0 N/25 mm or less, it is easy to peel off the aquarium transparent screen from the aquarium acrylic board after long-term use, that is, to reattach the aquarium transparent screen. be able to.
The initial adhesive strength of the adhesive layer can be controlled by adjusting the amount of crosslinking agent used in the above-mentioned adhesive composition. Specifically, the content of the crosslinking agent in the adhesive composition (adhesive layer) before the reaction to form a crosslinked structure proceeds is 0.00 parts by mass based on 100 parts by mass of the above-mentioned crosslinkable polymer. By adjusting the amount within the range of 1 to 10 parts by mass, it becomes easy to maintain the initial adhesive strength of the adhesive layer within the above range.

In the transparent aquarium screen of the present invention, the adhesive layer has an adhesive strength over time of 4.0 to 20.0 N/25 mm. The adhesive force of the adhesive layer over time is preferably 6.0 to 18.0 N/25 mm, more preferably 8.0 to 16.0 N/25 mm.
If the adhesive strength of the adhesive layer over time is less than 4.0 N/25 mm, it will not be possible to prevent air from entering between the aquarium acrylic board and the aquarium transparent screen during use, and the generation of air bubbles. When laminated with an acrylic board, sufficient adhesive strength is not obtained, and peeling tends to occur between the surface of the acrylic board for an aquarium and the adhesive layer during use. On the other hand, if the adhesive strength of the adhesive layer over time exceeds 20.0N/25mm, the adhesive strength will be too strong, and when removing the transparent aquarium screen from the aquarium acrylic board after long-term use, An adhesive layer remains behind, making it difficult to remove by hand, and the transparent support may be destroyed.
The peeling force over time of the adhesive layer can be controlled by adjusting the amount of the crosslinking agent used in the above-mentioned adhesive composition so that the peeling force over time falls within this range.

There is no limit to the storage modulus of the adhesive layer. The storage modulus of the adhesive layer is preferably 1.0×10 ⁵ to 1.0×10 ⁸ Pa, more preferably 5.0×10 ⁵ to 5.0×10 ⁷ Pa, and 1.0×10 ⁶ to 1.0×10 ⁷ Pa is more preferable.
By setting the storage elastic modulus of the adhesive layer to 1.0 x 10 ⁵ Pa or more, sufficient adhesive strength can be obtained when peeling the transparent aquarium screen from the aquarium acrylic board, and the generation of adhesive residue can be prevented. This can be more effectively prevented. By setting the storage elastic modulus of the adhesive layer to 1.0 x 10 ⁸ Pa or less, it becomes possible to easily peel off the transparent aquarium screen by hand when removing the aquarium transparent screen from the aquarium acrylic board after long-term use. Moreover, it is also possible to suitably prevent the transparent support from being destroyed during peeling.
The storage modulus of the adhesive layer can be controlled by adjusting the amount of crosslinking agent used in the above-mentioned adhesive composition so that the storage modulus falls within this range.

There is no limit to the haze of the adhesive layer used for transparent screens for aquariums. The adhesive layer preferably has a low internal haze so as not to impair transparency when bonded to an acrylic plate for an aquarium. The internal haze of the adhesive layer is preferably less than 0.8%, more preferably less than 0.5%, and even more preferably less than 0.2%.
By setting the internal haze of the adhesive layer to less than 0.8%, the transparency of the aquarium to which the acrylic plate for an aquarium is bonded can be ensured, and an aquarium with good internal visibility can be obtained.
The internal haze of the adhesive layer can be controlled by selecting the combination of the crosslinkable polymer and crosslinking agent and other components in the above-mentioned adhesive composition so that the internal haze falls within this range.

[Transparent support]
The transparent support supports the above-mentioned reflective layer, adhesive layer, and the like.
As the transparent support in the present invention, resin films such as TAC (triacetyl cellulose) and PET (polyethylene terephthalate) can be used as appropriate.
There is no limit to the thickness of the transparent support, but it is preferably 15 to 75 μm. Commercially available transparent supports having a thickness within this range can be suitably used.
By setting the thickness of the transparent support to 15 μm or more, appropriate stiffness and strength as a film can be ensured, and handling properties can be improved. Furthermore, by setting the thickness of the transparent support to 75 μm or less, it is possible to suppress the occurrence of warping of the film edges during construction and prevent peeling caused by this.
The thickness of the transparent support in the present invention is more preferably 25 to 50 μm.
Incidentally, the surface of the transparent support on the adhesive layer side may be subjected to corona treatment or an easy-adhesive coating such as acrylic for the purpose of increasing the adhesive force with the adhesive layer.

The transparent screen for an aquarium of the present invention may further have a protective adhesive film (protective film) on the surface of the adhesive layer and/or the light reflective layer before being bonded to the acrylic board for an aquarium.
In the present invention, a highly transparent resin film such as PET is used as the transparent support for the transparent aquarium screen, so optical inspection can be performed with the protective adhesive film attached. be.
Here, it is preferable that the protective adhesive film has a total light transmittance of 85% or more and a haze value of less than 0.8%. By setting the total light transmittance of the protective adhesive film to 85% or more and the haze value to less than 0.8%, transparency is ensured and the accuracy of optical inspection with the protective adhesive film bonded is improved. Can be made high.

As described above, the transparent aquarium screen of the present invention can be used as an adhesive sheet consisting only of an adhesive layer, but a double-sided adhesive sheet having adhesive layers on both sides of a resin film can also be suitably used.
In the case of using a double-sided adhesive sheet in the transparent screen for an aquarium of the present invention, for example, the resin film serves as the above-mentioned transparent support in the present invention, and one adhesive layer is bonded to the acrylic plate for an aquarium. , resulting in an adhesive layer having the above-mentioned initial and sequential adhesive strength. Further, the other adhesive layer is bonded to some layer (film, sheet-like material, plate-like material) constituting the transparent aquarium screen, such as a light-reflecting layer, for example.

In the transparent screen for an aquarium of the present invention, an example of a structure using a double-sided adhesive sheet is the transparent screen for an aquarium shown in FIG. 1 described above.
In this case, for example, as shown in the transparent screen for an aquarium in FIG. One adhesive layer 6 becomes the second adhesive layer 6, and the other adhesive layer becomes the second adhesive layer 4 bonded to the second transparent support 3.

In the aquarium transparent screen of the present invention using a double-sided adhesive sheet having adhesive layers on both sides of the resin film, the adhesive layer bonded to the aquarium acrylic board, that is, the first adhesive layer 6 in FIG. It has initial adhesive strength and temporal adhesive strength. By laminating this adhesive layer to the aquarium acrylic board, it can be attached to the aquarium acrylic board without generating bubbles, and it can be peeled off from the aquarium acrylic board if necessary. As mentioned above, there is no adhesive residue on the aquarium acrylic board.

On the other hand, among the adhesive layers of the double-sided adhesive sheet, the adhesive layer that is not bonded to the aquarium acrylic board, that is, the second adhesive layer 4 that is bonded to the second transparent support 3 in FIG. 1, is as shown below. It is preferable to include a crosslinked structure formed by a reaction between a crosslinking agent and a polymer (crosslinkable polymer) having a reactive functional group that is a functional group capable of reacting with the crosslinking agent. By using this adhesive layer, it is possible to prevent the adhesive layer and the layer attached to the adhesive layer, that is, the second transparent support 3 in FIG. 1, from peeling off unnecessarily.
Note that, as described above, the alignment layer 2 and the second transparent support 3 are not essential components in the transparent screen for an aquarium shown in FIG. Therefore, in the transparent screen for an aquarium shown in FIG. ) may be pasted.

In the following description, the inner adhesive layer that is not bonded to the aquarium acrylic board will be referred to as the "second adhesive layer", following the example of the transparent aquarium screen shown in FIG.

(i) Crosslinkable polymer The crosslinkable polymer for the second adhesive layer is preferably an acrylic polymer with a reduced content of carboxyl groups from the viewpoint of further reducing the amount of outgas from the double-sided adhesive sheet. . Specifically, the content of carboxyl groups in the crosslinkable polymer is such that the structural unit having a carboxyl group is 1.0 parts by mass or less per 100 parts by mass of the total monomers for forming the crosslinkable polymer. The amount is preferably 0.5 parts by mass or less, and more preferably 0.5 parts by mass or less. Furthermore, it is preferable that the crosslinkable polymer is an acrylic polymer having no carboxyl group. As mentioned above, in this specification, an acrylic polymer that does not have a carboxyl group is also referred to as a "carboxyl group-free polymer."
Similarly, the second adhesive layer preferably has a low content of carboxyl groups, and more preferably does not substantially contain any components having carboxyl groups. Examples of the structural unit having a carboxyl group include acrylic acid, methacrylic acid, and itaconic acid.

The constituent units of the crosslinkable polymer are not particularly limited.
The crosslinkable polymer may be composed only of structural units based on an acrylic compound, which is one or more compounds having a (meth)acryloyl group and its derivatives (ester, acrylonitrile, etc.), or It may contain structural units based on acrylic compounds and structural units based on compounds other than acrylic compounds.
In addition, the "(meth)acryloyl group" in this specification means both an acryloyl group and a metalloyl group. In this regard, the same applies to other similar terms. Moreover, the compounds other than the above-mentioned acrylic compounds may be composed of one type of compound, or may be composed of multiple types of compounds.

A preferred example of the above-mentioned acrylic compound is (meth)acrylic acid ester.
Specific examples of (meth)acrylic acid esters include chain skeletons such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth) ) acrylate, (meth)acrylate with a cyclic skeleton such as tetrahydrofurfuryl (meth)acrylate and imide acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate , (meth)acrylates having hydroxyl groups such as 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and amino groups such as N-methylaminoethyl (meth)acrylate. and (meth)acrylates having an epoxy group such as glycidyl (meth)acrylate.

Among these, the crosslinkable polymer preferably contains a structural unit based on an alkyl (meth)acrylate in which the alkyl group has 4 or less carbon atoms. As mentioned above, in this specification, "alkyl (meth)acrylate in which the alkyl group has 4 or less carbon atoms" is also referred to as "lower alkyl compound."
Specifically, such lower alkyl compounds include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Examples include acrylate, sec-butyl (meth)acrylate, and tert-butyl (meth)acrylate.

Among these, n-butyl (meth)acrylate and methyl (meth)acrylate are used from the viewpoint of facilitating the appropriate balance between increasing the adhesive properties of the second adhesive layer and reducing the amount of outgas. etc. are preferred. One type of lower alkyl compound may be used alone, or two or more types may be used in combination.

Examples of monomers providing structural units based on compounds other than acrylic compounds include olefins such as ethylene and norbornene, carboxylic acid vinyl esters such as vinyl acetate, and aromatic compounds having ethylenically unsaturated bonds such as styrene. As mentioned above, in this specification, "a monomer providing a structural unit based on a compound other than an acrylic compound" is also referred to as "other polymerizable compound."

The reactive functional group included in the crosslinkable polymer of the second adhesive layer is preferably a functional group that can react with an isocyanate group since the crosslinking agent contains a tolylene diisocyanate compound as described below. Examples of such functional groups other than carboxyl groups include hydroxyl groups, amino groups, and amide groups.

In the crosslinkable polymer, the type of compound that provides the structural unit having a reactive functional group is not particularly limited.
Examples include the above-mentioned (meth)acrylates having a hydroxyl group and (meth)acrylates having an amino group. Examples of ethylenically unsaturated compounds having such a reactive functional group include ethylenically unsaturated compounds containing an amide group and alcohols having a vinyl group. As mentioned above, in this specification, "ethylenic unsaturated compound having a reactive functional group" is also referred to as "reactive compound."
Specific examples of such reactive compounds include acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, 5-hexen-1-ol, 5-hexen-3 -ol, 4-penten-1-ol, and the like.

The reactive functional group possessed by the reactive compound is preferably a hydroxyl group, which is less likely to discolor due to heat or the like. Therefore, the reactive compound is preferably a (meth)acrylate having a hydroxyl group and/or an alcohol having a vinyl group.

When such a crosslinkable polymer contains a structural unit based on a lower alkyl compound and a structural unit based on a reactive compound, the content ratio of these structural units in terms of monomer mass in the crosslinkable polymer (lower alkyl compound: reactive compound) (compound) is preferably 90:10 to 99.9:0.1, more preferably 95:5 to 99.5:0.5.
By setting the above-mentioned ratio within this range, the second adhesive layer containing a crosslinked structure based on the obtained crosslinkable polymer can easily have a stress residual rate within a suitable range.

The crosslinkable polymer used in the second adhesive layer may further include a structural unit based on a morpholine compound containing an ethylenically unsaturated group. As mentioned above, in this specification, "ethylenic unsaturated group-containing morpholine compound" is also referred to as "morpholine compound".
Since the morpholine group has the function of promoting the reaction of the crosslinking agent described below, by including a structural unit based on a morpholine compound, the crosslinkable polymer becomes a polymer having a functional group with the function of promoting crosslinking. . In this case, the crosslinking density of the adhesive layer can be increased while reducing the possibility of outgassing compared to the case where a low molecular weight crosslinking accelerator described below is contained, which is preferable.
Specific examples of morpholine compounds include N-vinylmorpholine, N-allylmorpholine, and N-(meth)acryloylmorpholine. Among the morpholine compounds, N-(meth)acryloylmorpholine, which is also an acrylic compound, is preferred from the viewpoint of good copolymerizability with compounds related to other structural units. One type of morpholine compound may be used, or a plurality of types may be used.

The content of the structural unit based on a morpholine compound in the crosslinkable polymer for the second adhesive layer is determined from the viewpoint of keeping the stress residual rate within the above-mentioned range and making it difficult to generate outgas. It is preferably 2 to 30 parts by mass, and 4 to 25 parts by mass, based on the total of 100 parts by mass of the lower alkyl compound content of the structural units based on the content and the reactive compound content of the structural units based on the reactive compound. is more preferable.

The crosslinkable polymer for the second adhesive layer is based on a compound having an ethylenically unsaturated bond other than the above-mentioned structural units based on lower alkyl compounds, structural units based on reactive compounds, and structural units based on morpholine compounds. It may also include structural units. Specific examples of monomers providing such structural units include olefins, carboxylic acid vinyl esters, and aromatics having ethylenically unsaturated bonds, as in the case of the other polymerizable compounds mentioned above. Alternatively, compounds having a functional group having a crosslinking promotion function like morpholine compounds, such as ethylenically unsaturated group-containing imidazole compounds, are also exemplified.
Although the content of the structural units based on such compounds is not particularly limited, if the content is excessively large, there is a concern that it will become difficult to control the stress residual rate within the above range. Therefore, its content is 10 parts by mass based on 100 parts by mass of the lower alkyl compound content of the structural unit based on the lower alkyl compound and the reactive compound content of the reactive compound based structural unit. The upper limit is preferably 5 parts by mass, and more preferably 5 parts by mass.

(ii) Crosslinking agent The crosslinking agent for the second adhesive layer contains one or more compounds selected from the group consisting of tolylene diisocyanate (TDI) and its derivatives. In this specification, tolylene diisocyanate (TDI) and its derivatives are also referred to as "tolylene diisocyanate-based crosslinking agents" and may be further abbreviated as "TDI-based crosslinking agents."
The crosslinking agent for the second adhesive layer preferably contains a TDI-based crosslinking agent as a main component, more preferably consists of a TDI-based crosslinking agent, and even more preferably consists essentially of TDI.
Specific examples of TDI-based crosslinking agents include polyisocyanate compounds and isocyanurates added to trimethylolpropane and the like, bullet-type compounds, as well as known polyether polyols and polyester polyols, acrylic polyols, polybutadiene polyols, and Examples include urethane prepolymer-type polyisocyanates made by addition-reacting polyisoprene polyols and the like.
When the crosslinking agent contains a TDI-based crosslinking agent, the double-sided pressure-sensitive adhesive sheet can be bent more easily than when the crosslinking agent contains other polyisocyanate compounds such as xylylene diisocyanate (XDI) and hexamethylene diisocyanate (HMDI). Even if an external force is applied to the adhesive layer, stress is unlikely to remain in the adhesive layer.

The second adhesive layer preferably has a gel fraction of 10 to 70%, more preferably 20 to 60%. By adjusting the amount of the above-mentioned crosslinking agent used so that the gel fraction of the adhesive layer falls within this range, it becomes easy to set the stress residual rate within the above range.
Specifically, the content of the crosslinking agent in the adhesive layer before the reaction to form the crosslinked structure proceeds is 0.1 to 10 parts by mass based on 100 parts by mass of the above-mentioned crosslinkable polymer. By adjusting the gel fraction within this range, it becomes easy to make the gel fraction of the adhesive layer within the above-mentioned range.

(iii) Other components The second adhesive layer can contain various components without departing from the objective of the present invention.
Such components include, for example, crosslinking accelerators, coloring materials such as dyes and pigments, antioxidants such as anilide and phenol, ultraviolet absorbers such as benzophenone and benzotriazole, plasticizers, and antioxidants. , light stabilizers, dispersants, and leveling agents. However, it is preferable that these components do not easily generate outgas.

(iv) Thickness The thickness of the second adhesive layer is not particularly limited.
If it is too thin, there is a concern that desired adhesive properties may not be obtained, and if it is too thick, there is a concern that it will be disadvantageous from the viewpoint of processability. Therefore, the thickness of the second adhesive layer as a whole is usually selected in the range of 4 to 30 μm, preferably in the range of 6 to 25 μm.

Note that the transparent screen for an aquarium of the present invention is not limited to the configuration shown in FIG. That is, the transparent screen for an aquarium of the present invention can have various configurations as long as it has an adhesive layer, a transparent support, and a light reflective layer in this order.
In addition, in the example shown below, the light reflection layer may have the cholesteric liquid crystal layer mentioned above.

FIG. 3 shows an explanatory diagram of the layer structure of another preferred embodiment of a transparent screen for an aquarium. The transparent screen for an aquarium of the present invention may have a protective layer for protecting the light reflecting layer, as conceptually shown in FIG. 3.
The transparent screen for an aquarium shown in FIG. 3 includes, on one side of a transparent support 23, a light reflecting layer 21 containing a binder and fine particles dispersed in the binder. A protective layer 22 is further laminated on the light reflecting layer 21. Further, an adhesive layer 24 is laminated on the other surface of the transparent support 23 (the surface opposite to the light reflecting layer 21).
There are no restrictions on the protective layer 22, and various known sheet-like materials can be used as long as they have sufficient light transmittance. Examples include the various resin films exemplified in the transparent support described above.

As another example, a transparent aquarium screen having an optically shaped layer and a light reflecting layer is also preferably used.
For example, the transparent screen described in paragraphs [0017] to [0033] of JP-A No. 2017-156452, which has an optically shaped layer having a circular Fresnel lens shape and a half-mirror reflective layer, has a reflective layer that reflects light. Only the light is diffused; the transmitted light is not. As a result, a projected image with a good viewing angle and resolution can be displayed, and the water tank on the other side of the transparent screen will not be blurred or blurred, and will be clearly visible, achieving high transparency.

FIG. 2 conceptually shows the layer structure of an example of a transparent screen for an aquarium having this optically shaped layer and a light reflecting layer.
The transparent screen for an aquarium shown in FIG. 2 includes, in order from the acrylic plate for an aquarium side, an adhesive layer 16, a transparent support 11, a first optically shaped layer 12, a light reflective layer 13, a second optically shaped layer 14, and a protective layer. It is equipped with 15.

[Transparent aquarium screen and aquarium manufacturing method]
The transparent aquarium screen of the present invention can be manufactured by, for example, applying an adhesive composition to a laminate in which a light-reflecting layer is formed on a transparent support to form an adhesive layer. The aquarium of the present invention can be manufactured by bonding the thus produced transparent aquarium screen to an acrylic aquarium plate constituting the aquarium via an adhesive layer.
Alternatively, after coating an adhesive layer on a support different from the transparent support, only the adhesive layer may be transferred from the support and the adhesive layer may be provided on a laminate in which a light reflective layer is formed on the transparent support. .
Alternatively, after producing a double-sided adhesive film with adhesive layers coated on both sides of a support different from the transparent support, a laminate with a light reflective layer formed on the transparent support and an acrylic plate for an aquarium are bonded together. The transparent screen for an aquarium and the aquarium of the present invention may be created by laminating them via a double-sided adhesive film.
The coating method (coating method) when forming the above-mentioned adhesive layer is not particularly limited, and various known coating methods can be used, such as a die coater, a comma coater, a knife coater, a gravure coater, Alternatively, a roll coater or the like can be used.

In order to improve the adhesion between the adhesive layer and the transparent support and/or the aquarium acrylic board, the surface of the transparent support and/or the aquarium acrylic board may be subjected to an adhesion treatment such as corona treatment. can. An easily adhesive layer may be provided on the surface of the transparent support and/or the aquarium acrylic plate.

Such a transparent screen for an aquarium of the present invention has a total light transmittance of 70% or more.
By setting the total light transmittance to 70% or more, it is possible to suitably observe the inside of the aquarium in an aquarium with a transparent aquarium screen attached, both when the projected image is displayed and when the projected image is not displayed. become.

The transparent image display system of the present invention uses a projector to project projection light onto the aquarium of the present invention on which the transparent screen for an aquarium of the present invention is bonded from the viewing side.
That is, in the transparent image display system of the present invention, a projector projects light from the viewing side onto the aquarium of the present invention on which the transparent screen for an aquarium of the present invention is laminated, and the projected light is transmitted to the light reflecting layer of the transparent screen for an aquarium. This is an image display system that displays an image projected by a projector overlaid on the scene inside the aquarium by reflecting it off.
In the transparent image display system of the present invention, the projector is not limited, and various known projectors used in known image projection devices (image projection systems) can be used.

(Preparation of transparent acrylic board)
A transparent acrylic plate (Sumipex #000 [manufactured by Sumika Acrylic Co., Ltd.]) 300 mm square and 5 mm thick was prepared, and the surface was cleaned.
The acrylic resin of this transparent acrylic board is the same resin as the acrylic board for aquariums.

(Preparation of light reflective layer)
Display member RS-14 described in Example 13 of JP-A-2018-200459 was prepared as a light reflective layer.
This display member RS-14 has a cholesteric liquid crystal layer as a reflective layer.

(Preparation of adhesive composition)
Adhesive composition 1 was prepared with the following composition.
(Adhesive composition 1)
85 parts by mass of butyl acrylate, 15 parts by mass of methyl acrylate, 1 part by mass of acrylic acid, and 0.5 parts by mass of benzoyl peroxide were dissolved in ethyl acetate to give a monomer concentration of 40% by mass, and then heated at 60°C. Polymer solution 1 (mass average molecular weight: 1,100,000) was obtained by polymerizing for 9 hours.
Further, 45 parts by mass of butyl acrylate, 55 parts by mass of methyl methacrylate, 1 part by mass of acrylic acid, and 0.5 parts by mass of benzoyl peroxide were dissolved in toluene to give a monomer concentration of 20% by mass, and then 60 parts by mass of Polymerization was carried out at °C for 9 hours to obtain a polymer solution 2 (mass average molecular weight: 60,000).
65 parts by mass of solid content of polymer solution 1, 35 parts of solid content of polymer solution 2, 1 part by mass of isocyanate crosslinking agent (trade name: Coronate L [manufactured by Nippon Polyurethane Co., Ltd.]), and epoxy crosslinking agent (trade name) : Tetrad C [manufactured by Mitsubishi Chemical Corporation]) 0.05 part by mass was mixed to prepare adhesive composition 1.

(Preparation of adhesive sheet 1)
A PET film with a thickness of 25 μm was prepared.
The pressure-sensitive adhesive composition 1 was coated on both sides of this PET film so that the film thickness after drying was 25 μm. Thereafter, drying and aging were performed at 90 to 110° C. for 30 to 120 seconds to produce adhesive sheet 1 having adhesive layers on both sides of the PET film.
On the surface of each adhesive layer formed, an easily peelable PET film whose surface had been subjected to mold release treatment was laminated to form a protective film.

(Production of transparent screen for aquarium)
One side of the protective sheet of the adhesive sheet 1 obtained above was peeled off, and the support surface of the display member RS-14 described above was laminated to the exposed adhesive layer to produce a transparent aquarium screen of Example 1 Sample 1. did.

(Production of transparent acrylic plate laminated with transparent screen for aquarium)
The obtained transparent screen for an aquarium was bonded to a transparent acrylic board made of the same resin as the acrylic board for an aquarium described above.
Specifically, the protective film was peeled off from the obtained transparent aquarium screen, and the exposed surface of the adhesive layer was brought into close contact with the surface of the transparent acrylic board wetted with water. Thereafter, the air present between the adhesive layer and the transparent acrylic plate was scraped out from the side of the transparent aquarium screen using a rubber squeegee, and both were pasted together.
After that, the following evaluations were conducted.

(Evaluation 1) [Initial adhesive strength]
The initial adhesive strength (initial peel strength) of the adhesive layer in the present invention is a value measured according to JIS Z0237:2000.
To measure the adhesive strength, first cut the prepared aquarium transparent screen into a size of 25 mm x 150 mm, and use a transparent acrylic board (Sumipex #000 [manufactured by Sumika Acrylic Co., Ltd.], an acrylic board for an aquarium wetted with water). (same resin) and pressed together once with a 2 kg rubber roller, and left for 24 hours at a temperature of 25° C. and a humidity of 55% RH.
Thereafter, the adhesive force is measured using a tensile tester (unit: N/25 mm). The measurement conditions at this time were 180° peeling, temperature 25° C., humidity 55% RH, and peeling speed 300 mm/min.
(Evaluation 2) [Adhesion strength over time]
The adhesive strength over time (peel strength over time) of the adhesive layer was evaluated after drying the manufactured transparent aquarium screen and transparent acrylic board for 4 days at a temperature of 85°C and a humidity of 10% RH. The adhesive strength was measured in the same manner as the initial adhesive strength of No. 1.
(Rating 3) [Glue residue]
Adhesive residue on the adhesive layer was evaluated in the evaluation of adhesive strength over time in Evaluation 2 above, in which the presence or absence of adhesive residue on the surface of the transparent acrylic board was visually evaluated when the transparent aquarium screen was peeled off from the transparent acrylic board. be.
In addition, the above-mentioned "adhesive residue" in the present invention refers to a phenomenon in which a portion of the adhesive layer remains on the surface of the transparent acrylic board when the transparent aquarium screen is peeled off from the transparent acrylic board. In Table 1, "A" indicates that there was no adhesive residue, and "B" indicates that there was adhesive residue. In addition, cases where the adhesive force over time was so strong that the aquarium transparent screen could not be removed by hand from the transparent acrylic plate and the adhesive residue could not be evaluated were marked as "-" in Table 1.
(Rating 4) [Bubble generation]
A transparent acrylic board (Sumipex #000 [manufactured by Sumika Acrylic Co., Ltd.], 2 mm thick) was pasted on the prepared transparent screen for aquarium using water bonding under conditions of a temperature of 25°C and a humidity of 55% RH. After being left for 24 hours under conditions of humidity and RH of 55%, it was put into each test condition.
After 250 hours had elapsed, the sample was taken out and left for 24 hours at a temperature of 25°C and a humidity of 55% RH, and the presence or absence of bubbles on the adhesive surface between the transparent aquarium screen and the transparent acrylic plate was visually observed. . Adhesion reliability after time was evaluated according to the following criteria.
A: There are no bubbles on the adhesive surface between the transparent aquarium screen and the transparent acrylic board.
B: Bubbles were generated on the adhesive surface between the transparent aquarium screen and the transparent acrylic board.

(Evaluation 5) [Storage modulus]
When the storage elastic modulus of the adhesive layer of the produced transparent screen for aquarium was measured using Tensilon (manufactured by Toyo Seiki Seisakusho), the storage elastic modulus was 3.80 MPa.
The sample size during tensilon measurement was 5 mm in width, 1 mm in thickness, and 10 mm in length between chucks, and the pulling speed was 10 mm/min (temperature 25° C., humidity 55% RH). The storage modulus of other samples listed in Table 1 was also measured under the same conditions.
(Rating 6) [Internal Haze]
One drop of immersion oil for microscopic observation [manufactured by Nikon Corporation] was further dropped onto the adhesive layer of the prepared transparent screen for an aquarium, and an acrylic plate measuring 40 mm long x 40 mm wide and 2 mm thick was placed thereon. This was used as a sample for internal haze measurement.
When the internal haze was measured using a haze meter (NDH4000 [manufactured by Nippon Denshoku Industries Co., Ltd.]), the internal haze was 0.2%. Note that haze was measured based on JIS-K7136.
The internal haze of other samples listed in Table 1 was also measured under the same conditions.

(Evaluation 7) [Reflectance]
Three-dimensional bending spectroscopy is performed by appropriately setting the incident angle (polar angle and azimuth angle), acceptance angle (polar angle and azimuth angle), and measurement wavelength range so that the light enters from the light reflective layer side. Reflectance R[-45,30] (550) and reflectance R[-45,15] of a transparent screen for an aquarium prepared using a color measurement system (GCMS-3B [manufactured by Murakami Color Research Institute]) ] (550) was measured.
Here, R[-45, θ] (550) is the reception of light at a polar angle θ at an azimuth that is 180° different from the azimuth of the incident light for incident light at a polar angle of -45° to the transparent screen. Reflectance at a wavelength of 550 nm, measured in angle.

(Evaluation 8) [Total light transmittance]
When the total light transmittance of the produced aquarium transparent screen was measured using a haze meter (NDH4000 [manufactured by Nippon Denshoku Kogyo Co., Ltd.]), the total light transmittance was 78%. Note that the total light transmittance was measured based on JIS-K7136.
The total light transmittance of other samples listed in Table 1 was also measured under the same conditions.

The above evaluation results are shown in Table 1 below.

(Example 1 sample 2)
Example 1 Sample 1 had an adhesive layer made of Adhesive Composition 1 on one side, and an adhesive layer made of the same strong acrylic adhesive as PET-25WF (a commercially available double-sided adhesive sheet, manufactured by Nichiei Shinka Co., Ltd.). Adhesive sheet 2 was produced in the same manner as adhesive sheet 1 of sample 1, except that the adhesive sheet 2 was formed on the opposite side.
This adhesive sheet 2 is the same as Example 1 Sample 1 except that the protective film on the adhesive layer side made of the above-mentioned strong acrylic adhesive was peeled off and the surface of the support of the above-mentioned display member RS-14 was attached. In this way, a transparent aquarium screen of Example 1 Sample 2 was obtained.

(Example 1 sample 3)
A transparent aquarium screen of Example 1 Sample 3 was obtained in the same manner as Example 1 Sample 1 except that the thickness of the PET film in the adhesive sheet 1 used in Example 1 Sample 1 was changed to 50 μm.

(Example 1 sample 4)
Example 1 Example 1 except that the amount of isocyanate crosslinking agent in adhesive composition 1 used in Sample 1 was changed to 3.0 parts by mass, and the amount of epoxy crosslinking agent was changed to 1.0 parts by mass. In the same manner as Sample 1, a transparent aquarium screen of Sample 4 of Example 1 was obtained.
The transparent screen for an aquarium of Example 1 has a cholesteric liquid crystal layer as a light reflection layer, and is a so-called "cholesteric reflective transparent screen for an aquarium."

(Example 2)
Preparation of transparent screen with optical shape layer and light reflective layer In Example 1 Sample 2, instead of the display member RS-14 used as the reflective layer, the The screen 10 of the first embodiment was used as a reflective layer, and the protective film on the adhesive layer side made of the adhesive composition 1 of the adhesive sheet 2 was peeled off and laminated in the same manner as in Example 1 Sample 2. A transparent aquarium screen of Example 2 was obtained.

(Example 3)
Preparation of light-diffusing transparent screen In Example 1 Sample 2, the transparent screen described in Example 1 of International Publication No. 2017/94550 was used as the reflective layer instead of the display member RS-14 used as the reflective layer. The transparent aquarium screen of Example 3 was prepared in the same manner as Example 1 Sample 2 of the present invention, except that the protective film on the adhesive layer side made of adhesive composition 1 of the adhesive sheet 2 was peeled off and laminated. I got it.

(Comparative Example 1 Sample 11)
Transparent screen using commercially available double-sided adhesive sheet Example 1 Instead of adhesive sheet 1 used in Sample 1, PET-25WF (commercially available double-sided adhesive sheet [manufactured by Nichiei Shinka Co., Ltd.]) was used and laminated. Except for this, a transparent aquarium screen of Comparative Example 1 Sample 11 was obtained in the same manner as Example 1 Sample 1.

(Comparative Example 1 Sample 12)
Example 1 Sample 1 except that the amount of isocyanate crosslinking agent in adhesive composition 1 used in Example 1 Sample 1 was changed to 0.5 parts by mass, and the amount of epoxy crosslinking agent was changed to 0 parts by mass. In the same manner as above, a transparent aquarium screen of Comparative Example 1 Sample 12 was obtained.

(Comparative Example 1 Sample 13)
Example 1 Example 1 except that the amount of isocyanate crosslinking agent in adhesive composition 1 used in Sample 1 was changed to 3.0 parts by mass, and the amount of epoxy crosslinking agent was changed to 5.0 parts by mass. In the same manner as Sample 1, a transparent aquarium screen of Comparative Example 1 Sample 13 was obtained.
That is, the transparent screen for an aquarium of Comparative Example 1 also has a cholesteric liquid crystal layer as a light reflecting layer, and is a so-called "cholesteric reflective transparent screen for an aquarium."

(Comparative example 2)
Example 3 except that in the adhesive sheet 2 of Example 3, PS-D1 (commercially available adhesive sheet [manufactured by Panac Corporation]) was used instead of the adhesive layer made of adhesive composition 1. In the same manner, a transparent aquarium screen of Comparative Example 2 was obtained.

Table 1 shows the results of evaluating Samples 2 to 4 of Example 1, Examples 2 and 3, and Samples 11 to 13 of Comparative Example 1 and Comparative Example 2 in the same manner as Sample 1 of Example 1. .

From Table 1, samples 1 to 4 of Example 1, Example 2, and Example 3 using the adhesive of the present invention have appropriate initial and temporal peeling forces, no adhesive residue, no bubble formation, It can be seen that it is suitable as a transparent screen for aquariums.
In addition, the produced transparent aquarium screen was pasted on an acrylic aquarium (width 2m x height 2m), and a short throw projector TH671ST (DLP projection method, resolution 1080p, brightness 3000lm, manufactured by BenQ) was attached 1.5m from the aquarium. It was installed and projected on the ceiling at a distance. When confirmed from the front (0 degrees) and diagonal (30 degrees and 45 degrees on each side) of the aquarium, all samples showed R[-45,30](550)/R[-45,15](550). Since it was 1.3 or more, the image projected on the reflective transparent screen for an aquarium of the present invention could be clearly viewed from any position. In particular, in Example 1, the shadows of fish swimming in the aquarium could also be visually recognized with high clarity.

1 Light reflective layer 2 Alignment layer 3 Second transparent support 4 Second adhesive layer 5 First transparent support 6 First adhesive layer 11 Transparent support 12 First optically shaped layer 13 Light reflective layer 14 Second optically shaped layer 15 Protective layer 16 Adhesive layer 21 Light reflecting layer 22 Protective layer 23 Transparent support 24 Adhesive layer

Claims (6)

A transparent aquarium screen comprising an adhesive layer, a transparent support, and a light reflective layer in this order,
The total light transmittance is 70% or more,
The adhesive layer has an initial adhesive strength of 3.0 N/25 mm or more, and an adhesive strength over time of 4.0 to 20, which is the adhesive strength after 4 days at a temperature of 85° C. and a humidity of 10% RH. .0N/25mm , and the storage modulus at 25° C. is 1.0×10 ⁶ to 1.0×10 ⁷ Pa ,
A transparent screen for an aquarium, which is attached to an acrylic plate for an aquarium via the adhesive layer, and displays an image on the projection side by reflecting projection light projected from a projector. The transparent screen for an aquarium according to claim 1, wherein the adhesive layer has an initial adhesive force of 10 N/25 mm or less. The aquarium according to claim 1 or 2, wherein at least one layer of the light reflective layer has a cholesteric liquid crystal layer, all the cholesteric liquid crystal layers have the same helical sense, and further satisfies the following formula ( 1 ). transparent screen.
R[-45,30](550)/R[-45,15](550)≧1.3 Formula (1)
Here, R[-45,30] (550) is the polar angle at an azimuth angle that is 180° shifted from the azimuth angle of the incident light with respect to the incident light at a polar angle of -45° to the transparent screen for an aquarium. R[-45,15] (550) represents the reflectance at a wavelength of 550 nm measured at a light reception angle of 30°, and R[-45,15] (550) is the reflectance at a polar angle of -45° to the transparent screen for an aquarium. It represents the reflectance at a wavelength of 550 nm, measured at a reception angle of 15 degrees polar angle in an azimuth deviated by 180 degrees from the azimuth of the incident light. The transparent screen for an aquarium according to any one of claims 1 to 3 , further comprising a protective film on the side of the adhesive layer opposite to the transparent support. An aquarium, wherein the transparent screen for an aquarium according to any one of claims 1 to 4 is bonded to the surface of an aquarium made of an acrylic plate for an aquarium using the adhesive layer. 6. A transparent image display system that projects light onto the aquarium according to claim 5 from a viewing side using a projector, thereby displaying an image formed by the projected light from the projector so as to be superimposed in the aquarium.