JP2012163806A - Near-infrared ray shielding filter for display and image display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near-infrared ray shielding filter for a display which is arranged on the front surface of a display panel and shields near-infrared rays emitted from the display panel, the filter efficiently shielding the near-infrared rays while suppressing lowering of transmittance in a visible light region.SOLUTION: In a near-infrared ray shielding filter 10 for the display which has a near-infrared ray reflection layer 1 that makes visible light rays transmit therethrough and reflects near-infrared rays, and a near-infrared ray absorption layer 2 which makes the visible light rays transmit therethrough and absorbs the near-infrared rays in this order, in order from an observer V side, the near-infrared ray reflection layer has a first layer 1a which selectively reflects one circularly polarized light of right-handed circularly polarized light and left-handed circularly polarized light, and makes the other circularly polarized light transmit therethrough, and a second layer 1b which has an opposite rotational direction to that of the first layer that reflects circularly polarized light opposite to that of the first layer and makes the circularly polarized light opposite to that of the first layer transmit therethrough. And further, an electromagnetic wave shielding layer 4 may be provided in the side of a display panel 3 close to the near-infrared ray absorption layer. An image display apparatus 20 is structured so that the near-infrared ray shielding filter for the display is arranged on the front surface of the plasma display panel.

Description

  The present invention relates to a filter that is disposed in front of a display and shields infrared rays emitted from the display, particularly near infrared rays, and more particularly to a filter that can efficiently shield near infrared rays while keeping the transmittance of visible light as high as possible. The present invention also relates to an image display device using the filter.

In recent years, various thin displays such as a liquid crystal display (LCD) and a plasma display (hereinafter also referred to as PDP) have become widespread, and recently, the trend toward lower power consumption has increased.
In addition, an optical filter is disposed on the front surface (screen) of the display panel, and the optical filter allows the electromagnetic wave shielding function, the near infrared shielding function, the neon light shielding function, the toning function, the contrast improving function, the antireflection function, etc. In addition, various functions such as an antistatic function and an impact resistance function are realized. Among these functions, an optical filter that realizes a near-infrared shielding function that cuts off near-infrared rays is a near-infrared absorbing dye (hereinafter also referred to as a NIRA dye) that cuts light in the near-infrared region that interferes with the wavelength range used by the remote controller. ) Is widely used (Patent Document 1, Patent Document 2).

  The near-infrared shielding filter described in Patent Document 1 and Patent Document 2 is a single type of near-infrared absorbing dye such as a phthalocyanine compound, a benzopyran compound, a diimonium compound, and an antimony fluoride organic compound in a resin sheet. 2 or more types are used. Thereby, the absorption band is widened, and the near infrared ray is absorbed in a part or all of the wavelength band 800 to 1100 nm of the near infrared ray emitted from the front surface of the PDP.

  Also, near infrared rays are not absorbed using near-field absorption dyes (abbreviated as NIRA (Near Infrared Absorbing) dyes), but near infrared rays emitted from the display panel are reflected by a filter provided on the front surface. And the near-infrared shielding filter which cuts the near-infrared rays which reach | attain an observer by returning to the original direction is also proposed (patent document 3). In the near-infrared shielding filter described in Patent Document 3, the cholesteric liquid crystal solidified layer obtained by solidifying cholesteric liquid crystal reflects right (or left) circularly polarized light according to the rotational direction of the helical axis of the cholesteric liquid crystal, but the rotational direction is reverse. The left (or right) circularly polarized light of FIG. 1 reflects near infrared rays in the original direction by utilizing the transmitting property.

  In addition, when using a member provided with a conductor layer obtained by sputtering a conductive material such as silver or ITO (indium tin oxide) as an electromagnetic wave shielding function for PDP, the conductor layer should have a near infrared absorption function. Is common. However, in the case of a conductor layer formed by sputtering, the electromagnetic wave shielding performance is inferior to that of a conductor layer made of a metal mesh that is usually used, so that there is a problem that applicable models are limited. Therefore, in order to improve the electromagnetic wave shielding performance, the number of thin film laminations by sputtering may be increased. However, in that case, the transmittance in the visible light region is reduced and the manufacturing cost is increased, which is not practical.

Japanese Patent No. 3457132 Japanese Patent No. 3689998 JP 2000-28827 A

  However, the near-infrared shielding filters using NIRA dyes as described in Patent Document 1 and Patent Document 2 are not completely transparent in the visible light region and absorb in the visible light region. This is because the actual NIRA dye has a boundary (780 nm) between the long wavelength end side of the visible light region (approximately 680 to 780 nm band) and the short wavelength end side of the near infrared region (approximately 780 to 900 nm band). This is because there is no transmission spectrum (or absorption spectrum) with an ideal characteristic in which the transmittance rises sharply (or the absorption rate drops sharply). For this reason, since the vicinity of the lowest wavelength (near 780 nm) in the near-infrared band to be absorbed is close to the vicinity of the maximum wavelength (near 780 nm) in the visible light region, the near-infrared region has a high cut rate (low transmittance). When trying to do so, the transmittance also decreases in part of the visible light region, and there is a problem that the brightness of the display image is lowered and the hue of the image is shifted from the design value. Further, if it is attempted to prevent a decrease in image brightness and a hue shift in the image, there is a problem in that the transmittance in the near infrared region increases and the absorption rate decreases. Moreover, NIRA dyes with high transmittance in the visible light region are limited, and there are still many problems in terms of price and reliability. For this reason, it is difficult to say that a near-infrared shielding filter that absorbs near-infrared rays using NIRA dyes can efficiently use the light emission of the display panel, and the emission energy is wasted from the viewpoint of reducing power consumption. It was used for.

On the other hand, a near-infrared shielding filter using a cholesteric liquid crystal solidified layer as described in Patent Document 3 uses a plurality of types of NIRA dyes because the wavelength band selectively reflected by the characteristics of circularly polarized light is narrower than that of NIRA dyes. It is necessary to stack a plurality of types of cholesteric liquid crystal solidified layers having different types of wavelength bands for selective reflection, rather than the case. Accordingly, the entire thickness of the near-infrared shielding filter becomes thick and bulky, and the number of lamination processes increases. Further, the unit price of the cholesteric liquid crystal itself is high, so that the filter using the cholesteric liquid crystal solidified layer is more expensive than the filter using the NIRA dye. There is also a problem.
Therefore, in order to improve this point, the present applicant, in Japanese Patent Application No. 2009-260920, which has not been published at the time of filing the present application, a near-infrared reflective layer composed of a cholesteric liquid crystal solidified layer, a near-infrared absorbing layer composed of a NIRA dye, We proposed an infrared shielding filter for displays combined with the above. However, even in this form, the near-infrared shielding performance is not perfect, and the shielding rate at the near-infrared reflecting layer provided after absorption by the near-infrared absorbing layer is 50% at the maximum, for displays that can shield near-infrared more efficiently. An infrared shielding filter was desired.

  That is, an object of the present invention is to provide a near-infrared ray for a display that can efficiently block the near-infrared region, particularly the short wavelength end side, while suppressing a decrease in transmittance in the visible light region, particularly the long wavelength end side. It is to provide a shielding filter. It is another object of the present invention to provide an image display device using such a near-infrared shielding filter for display.

Therefore, in the present invention, the configuration of the near-infrared shielding filter for display is as follows.
(1) In a near-infrared shielding filter for display that is arranged in front of a display panel and shields near-infrared rays emitted from the display panel.
In order from the observer side, it has at least a near-infrared reflective layer that transmits visible light and reflects near-infrared light, and a near-infrared absorption layer that transmits visible light and absorbs near-infrared light in this order,
The near-infrared reflective layer selectively reflects one circularly polarized light (specific circularly polarized light) of right circularly polarized light or left circularly polarized light and transmits the other circularly polarized light, and the first layer is a circle. The rotation direction of the polarization is opposite, and the second circular layer is configured to selectively reflect one of the left circularly polarized light and the right circularly polarized light and transmit the other circularly polarized light.
(2) Further, according to the present invention, in the above configuration, an electromagnetic wave shielding layer is further provided on the display panel side than the near infrared absorption layer.

  Further, the image display device of the present invention has a configuration in which any one of the above-described near-infrared shielding filters for display is disposed on the front surface of the plasma display panel.

  According to the present invention, near infrared rays can be shielded extremely efficiently while suppressing a decrease in transmittance in the visible light region.

One example (a) of a near-infrared shielding filter for display according to the present invention and two types (b) and (c) of an image display device in which a near-infrared shielding filter for display is arranged on the front surface of a plasma display panel are illustrated. Sectional drawing. Sectional drawing which illustrates another form example (clarified the transparent base material 5) about the near-infrared shielding filter for displays by this invention. Explanatory drawing explaining the mechanism of the near-infrared shielding filter for displays by this invention. Explanatory drawing explaining the mechanism of the near-infrared shielding filter in the case of only a near-infrared reflective layer. The figure which shows an example of the spectrum of the transmittance | permeability and reflectance of a near-infrared reflective layer (single layer only of a 1st layer).

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

[Summary]
The near-infrared shielding filter for display of the present invention, like the near-infrared shielding filter for display 10 whose form is illustrated in FIG. 1A, sequentially transmits visible light and reflects near-infrared from the viewer V side. The near-infrared reflecting layer 1 and the near-infrared absorbing layer 2 that transmits visible light and absorbs near-infrared light in this order, and the near-infrared reflecting layer 1 is one of right circularly polarized light and left circularly polarized light. A first layer 1a that selectively reflects one circularly polarized light and transmits the other circularly polarized light, and the first layer is a circularly polarized light whose direction of rotation is opposite to one of the left circularly polarized light and the right circularly polarized light. It is a filter composed of two layers, the second layer 1b that selectively reflects and transmits the other circularly polarized light.
Hereinafter, in this specification, the 1st layer 1a is demonstrated as a layer located in the near-infrared absorption layer 2 side rather than the 2nd layer 1b.

The image display device 20 of the present invention has a configuration in which the display near-infrared shielding filter 10 as described above is disposed as the display panel 3 on the front surface of the plasma display panel as shown in FIG.
As a result, even if near-infrared rays are emitted from the display panel 3 to the viewer side, the near-infrared rays can be shielded very efficiently without reducing the transmittance in the visible light region constituting the image as much as possible. Therefore, it is possible to prevent the screen from becoming dark due to a decrease in the transmittance of visible light. If the brightness is the same, low power consumption can be achieved.

  “Visible light transmits and reflects near infrared light” and “Visible light transmits and absorbs near infrared light” are relative absorption and reflection characteristics of visible light and near infrared light. It does not necessarily mean that all visible rays are transmitted and all near infrared rays are reflected or absorbed.

In FIG. 1B, the near-infrared shielding filter for display 10 and the display panel 3 are arranged in close contact with no space (air layer) between them, but may be arranged with a space in between. Good. For example, the image display device 20 shown in FIG.
The image display device 20 illustrated in FIG. 1C has a configuration in which the display near-infrared shielding filter 10 further includes an electromagnetic wave shielding layer 4 on the display panel 3 side. The filter 10 is disposed on the front surface of the display panel 3 with an air space provided between them.

Further, the near-infrared shielding filter 10 for display may have a transparent base material, and in this case, the transparent base material is a separate layer that does not belong to the near-infrared reflective layer 1 or the near-infrared absorption layer 2 or It may be provided as a layer to which it belongs or as a layer to which it belongs.
For example, the near-infrared shielding filter for display 10 illustrated in FIG. 2A includes a near-infrared reflective layer 1 composed of a first layer 1a and a second layer 1b, and a near-infrared absorbing layer 2. It is the structure which has the transparent base material 5 as a support body which does not belong.
Moreover, the near-infrared shielding filter for display 10 illustrated in FIG. 2B has a configuration in which the near-infrared reflective layer 1 further includes a transparent substrate 5a between the first layer 1a and the second layer 1b. The near-infrared absorbing layer 2 comprises a near-infrared absorbing layer 2a and a transparent substrate 5b from the viewer V side, and the first layer 1a facing the near-infrared absorbing layer 2 side of the near-infrared reflecting layer 1 is absorbing near-infrared rays. The structure is in contact with the layer 2a.
In addition, the structure using a transparent base material is not limited to the layer structure of this FIG.

  The present invention will be further described in detail below.

[Mechanism for shielding near infrared rays]
As a result of intensive studies, the present invention has shown that the near-infrared absorbing layer 2 includes the near-infrared absorbing layer 2 and the near-infrared reflecting layer 1 composed of the first layer 1a and the second layer 1b having different turning directions of the circularly polarized light to be reflected. And near-infrared reflective layer 1 are combined in a predetermined positional relationship, and it has been found that near-infrared rays can be shielded extremely efficiently without reducing visible light transmittance. See FIG. 3 for the mechanism. To explain.
First, in the present invention, as the predetermined positional relationship, as shown in FIG. 3, the near infrared absorbing layer 2 is disposed between the display panel 3 that emits near infrared rays and the near infrared reflecting layer 1. Have.

In the description of FIG. 3, the near-infrared reflective layer 1 includes a first layer 1a and a second layer 1b that reflect near-infrared light as circularly polarized light, and the rotational directions of the circularly polarized light are different from each other, and reflected light from the first layer 1a. The circularly polarized light is right-handed circularly-polarized light R whose turning direction is clockwise (clockwise) toward the traveling direction of light, and the circularly polarized light of the reflected light of the second layer 1b is the opposite, and the turning direction is the traveling direction of light. It is assumed that the left circularly polarized light L is counterclockwise (counterclockwise).
In the description of FIG. 3, the near infrared source side layer close to the display panel 3 is called a first layer 1a, and the layer far from the display panel 3 is called a second layer 1b.
In addition, since the light that has not been polarized and separated before being reflected by the first layer 1a can be regarded as light in which the left circularly polarized light L and the right circularly polarized light R are mixed, the rotation direction of the circularly polarized light is indicated by “L + R”. .
It should be noted that the first layer 1a may be formed with either the right circularly polarized light R layer or the left circularly polarized light L layer.
In addition, the first layer 1a and the second layer 1b are layers in which the rotational directions of the circularly polarized light are opposite to each other. Therefore, either of these layers may be essentially the near infrared absorption layer 2 side. As described above, in the present specification, the first layer 1a is treated as a layer on the near infrared absorption layer 2 side.

  The near infrared ray (1) emitted from the display panel 3 to the viewer V side is first absorbed by the near infrared absorption layer 2. The near-infrared ray (2) that has passed without being absorbed by the near-infrared absorbing layer 2 is reflected by the first layer 1a of the near-infrared reflecting layer 1 as right circularly polarized light R as one of the left and right circularly polarized light. Then, the near-infrared ray (3) of the left polarized light L having a maximum of 50% reflected and the reverse rotation direction reaches the next second layer 1b. Then, this time, the second layer 1b reflects the left circularly polarized light L as one of the left and right circularly polarized light, and the entire near infrared light reaching the second layer 1b from the near infrared light source reflects a maximum of 100%. . In the second layer 1b, unlike the case of the first layer 1a, the near-infrared ray (3) reaching the second layer 1b has no right circularly polarized R component. A maximum of 100% will be reflected. The second layer 1b has a property of transmitting circularly polarized light that is reverse to the reflected light there, that is, the right circularly polarized light R, but the near infrared light that has reached the second layer 1b is component light of the right circularly polarized light R. Therefore, the near-infrared light of the left circularly polarized light L is not emitted from the second layer 1b as transmitted light. For this reason, the near infrared ray (4) of the left circularly polarized light L does not reach the eyes of the observer V from the second layer 1b.

On the other hand, the near-infrared ray (5) of the right circularly polarized light R reflected by the first layer 1a of the near-infrared reflecting layer 1 is again absorbed when it travels to the near-infrared absorbing layer 2 and is transmitted therethrough. Further, the near-infrared ray (6) of the left circularly polarized light L transmitted through the first layer 1a and reflected by the second layer 1b travels again to the first layer 1a. Since the first layer 1a has the property of transmitting the near-infrared ray (6) of the left circularly polarized light L, the near-infrared ray (6) of the left circularly polarized light L passes through the first layer 1a without being absorbed as it is. Eventually, the near-infrared ray (6) reflected by the second layer 1b is again re-absorbed when it passes through the near-infrared absorbing layer 2 and passes through it.
Therefore, the near-infrared absorbing layer 2 has the near-infrared ray (5) of the right circularly polarized light R reflected from the first layer 1a and the left circularly-polarized light L of the reflected light from the second layer 1b from the image observer V side. Both near-infrared (6) and will proceed. These near-infrared rays (5) and near-infrared rays (6) are absorbed again by the near-infrared absorption layer 2, and the near-infrared light L and the right-hand circularly polarized light R that are left unabsorbed are included. Infrared rays (7) are directed to the display panel 3. Next, the light is reflected by the display panel 3 and travels again in the direction of the viewer V, repeatedly passes through the near-infrared absorbing layer 2 and further attenuates.
In FIG. 3, which is a conceptual diagram, it seems that there is a space between each member, but usually there are usually an adhesive layer, other members, a transparent substrate, and the like. However, in the present invention, a space may or may not exist.

Further, the near-infrared ray (7) returned to the display panel 3 becomes light in which the right circularly polarized light R and the left circularly polarized light L are mixed, but when these are mixed in an equivalent amount, it can be regarded as natural light. Even if any of the circularly polarized light components remain, if the behavior is considered by distinguishing between the right circularly polarized light R and the left circularly polarized light L, the near infrared light can be shielded very efficiently.
That is, when the near infrared ray (7) returned to the display panel 3 is regularly reflected on the surface, the direction of the circularly polarized light of the reflected near infrared ray is reversed. Accordingly, when the near-infrared light of the right circularly polarized light R reflected by the first layer 1a of the near-infrared reflective layer 1 is reflected by the display panel 3 and again comes to the first layer 1a of the near-infrared reflective layer 1, Left circularly polarized light L is obtained. The near-infrared light of the left circularly polarized light L passes through the first layer 1a of the near-infrared reflection layer 1, but the near-infrared absorption layer 2 exists between the display panel 3 and the near-infrared reflection layer 1. Since the light passes through and reciprocates twice until it returns to the near-infrared reflective layer 1, the near-infrared can be shielded more efficiently than in the case of the first layer 1a of the near-infrared reflective layer 1 alone. become. Further, next to the first layer 1a of the near-infrared reflective layer 1, the second layer 1b having a reverse rotation direction of the circularly polarized light to be reflected is waiting, and reflects the left circularly polarized light L. Since the left circularly polarized light L is reflected and returned to the original direction and is not transmitted, the near-infrared light can be blocked very efficiently.
Next, the near infrared ray of the left circularly polarized light L reflected by the second layer 1b will be considered. The near-infrared light of the left circularly polarized light L is transmitted through the first layer 1b and reflected by the display panel 2 and then comes to the first layer 1a of the near-infrared reflective layer 1 again. It has become. The near infrared light of the right circularly polarized light R is reflected by the first layer 1 a of the near infrared reflection layer 1. And since it attenuate | damps and extinguishes similarly to the right circularly polarized light R reflected by the above-mentioned 1st layer 1a, a near infrared ray can be interrupted | blocked very efficiently.

  If the near-infrared absorbing layer 2 and the near-infrared reflecting layer 1 composed of the first layer 1a and the second layer 1b have the opposite positional relationship to the near-infrared source, the near-infrared reflecting layer 1 may reflect the light. Since near-infrared light passes through the near-infrared absorbing layer 2 only once as light transmitted through the near-infrared reflecting layer 1, the near-infrared light cannot be effectively shielded as described above.

  With the configuration as described above, compared to a configuration using only the near-infrared absorbing layer 2, the near-infrared light emitted from the display panel 3 can be further attenuated to near zero by simple calculation. On the other hand, when the target near-infrared shielding performance can be kept constant without increasing the target, the predetermined near-infrared shielding performance can be secured even if the near-infrared absorbing performance of the near-infrared absorbing layer is reduced to 0 (zero). . In this case, the absorption amount of visible light absorbed by the near-infrared absorbing layer on the long wavelength end side in the visible light region is also attenuated to 0 (zero). In this case, the meaning of providing the near-infrared absorbing layer itself does not exist, but this is an ideal story of simple calculation, and the actual near-infrared reflecting layer 1 has a first layer 1a and a second layer 1b. The reflectance of the specific circularly polarized light component (L or R) is not 100%, and there is a component that transmits a little. For this reason, a near-infrared absorbing layer 2 is provided as shown in FIG. 3 in order to more completely shield the near-infrared rays that pass through the first layer 1a and the second layer 1b of the near-infrared reflecting layer 1. In view of the near-infrared absorbing layer 2, when considering the maximum absorption wavelength and absorption wavelength band of an actual near-infrared absorbing dye, the combination of the near-infrared reflecting layer 1 and the near-infrared absorbing layer 2 is In practice, it makes sense. For this reason, when the absorption amount of the near-infrared absorbing layer 2 is not 0 (zero), but a certain amount of absorption is ensured, the concentration of the near-infrared absorbing dye in the near-infrared absorbing layer is reduced to transmit visible light. You can raise the rate. Moreover, since the usage-amount of the expensive near-infrared absorption pigment | dye added to a near-infrared absorption layer can be reduced, the cost reduction effect can also be anticipated.

On the other hand, when the near-infrared reflecting layer 1 following the near-infrared absorbing layer 2 is only the first layer 1a (or the second layer 1b) and either one of the left and right circularly polarized light is not reflected, this is also shown in FIG. If diverted and explained, it becomes as follows, and the near-infrared shielding performance cannot be improved so much.
That is, the near infrared ray (1) radiated from the display panel 3 to the viewer V side is absorbed by the near infrared ray absorbing layer 2, and the remaining transmitted near infrared ray (2) is caused by the first layer 1a of the near infrared ray reflecting layer 1. Near infrared (5) of right circularly polarized light R is reflected. Therefore, the remaining near infrared ray (2) absorbed by the near infrared absorption layer 2 reflects up to 50%, and the remaining 50% of the near infrared ray (3) of the left circularly polarized light L has no second layer 1b. Therefore, it reaches the eyes of the observer V as it is.

  Further, as shown in FIG. 4, when only the first layer 1a of the near-infrared reflecting layer 1 is omitted and the near-infrared absorbing layer 2 is omitted, it becomes as follows, and so near-infrared shielding performance cannot be expected. That is, the near infrared ray (1) radiated from the display panel 3 to the viewer V side is reflected by one of the left and right circularly polarized light at the first layer 1a of the near infrared reflecting layer 1 and the maximum is 50% in total. Reflected and the remaining 50% of near infrared rays (3) reach the eyes of the observer V. Already at this point, 50% of the near infrared rays emitted by the display panel 3 will allow transmission. On the other hand, the near infrared ray (2) reflected by the near infrared reflecting layer 1 returns to the display panel and the near infrared ray (4) reflected there repeats again toward the near infrared reflecting layer 1 and is reflected again there, A part of the near-infrared ray (5) in which the turning direction of the circularly polarized light is reversed passes through the near-infrared absorbing layer 1 and reaches the eyes of the observer V. Therefore, when the transmitted near infrared rays (3) and (5) of both are added, in the form of FIG. 4, more than 50% of the near infrared rays emitted from the display panel 3 are transmitted, and the near infrared shielding performance. Is not so expensive.

As shown in FIG. 4, the near-infrared reflective layer 1 includes two layers, a first layer 1a and a second layer 1b, but the near-infrared absorbing layer 2 is omitted and only the near-infrared reflective layer 1 is used. The near-infrared shielding performance is reduced as follows.
That is, the near infrared ray (1) radiated from the display panel 3 to the observer V side is the near infrared ray of the right circularly polarized light R as one circularly polarized light of the left and right circularly polarized light in the first layer 1a of the near infrared reflective layer 1. 4) is reflected. Here, 50% of the total is reflected, and the remaining 50% of the near-infrared ray (2) of the left circularly polarized light L proceeds to the next second layer 1b. In the second layer 1b, the near-infrared ray (5) of the left circularly polarized light L is reflected, and the near-infrared ray (3) of the left circularly polarized light L reaching the second layer 1b reflects a maximum of 100% as a whole. The left circularly polarized light L component that can be transmitted through the layer 1b is 0%. For this reason, the near infrared ray (3) of the left circularly polarized light L does not reach the eyes of the observer V from the second layer 1b. Further, the near infrared (4) of the right circularly polarized light R and the near infrared (5) of the left circularly polarized light L reflected by the near infrared reflecting layer 1 are mixed and returned to the display panel 3 to be reflected there again to be an image observer. Near infrared rays (6) traveling to the side. At this time, since the near-infrared absorbing layer 2 does not exist between the near-infrared reflecting layer 1 and the display panel 3, the near-infrared attenuation due to repeated transmission of the near-infrared absorbing layer 2 cannot be expected.
Therefore, in the first layer 1a and the second layer 1b of the near-infrared reflection layer 1, only when the reflectance of one specific circularly polarized light component is ideally 100%, a complete near-infrared ray is obtained by the above-described mechanism. Shielding is possible.

By the way, in the description with reference to FIGS. 3 and 4 so far, the first layer 1a and the first layer 1a of the near-infrared reflective layer 1 and the first layer in all wavelength bands of the near-infrared region that need to be cut off in order to explain basic performance. It is assumed that both the two layers 1b exhibit a 100% reflection function and a 100% transmission function with respect to one specific circularly polarized light component (L or R).
However, in reality, the cholesteric liquid crystal solidified layer has a wavelength bandwidth Δλ in which circularly polarized selective reflection occurs, and also has a wavelength λ _{0 in} which the reflectance of selective reflection is maximum, as will be described later. Even within the wavelength band, the reflectance of one specific circularly polarized light component does not become 100% completely. For this reason, a part of the left circularly polarized light L or the right circularly polarized light R is composed of both the near-infrared reflective layer 1 and the first layer 1a and the second layer 1b whose direction of rotation is opposite to that of the first layer 1a. Can reach the eyes of the observer V. Therefore, rather than completely reflecting in all the required wavelength bands and completely transmitting one circularly polarized light component completely, the incomplete part is recognized, and in order to compensate for the incompleteness, It is more practical to achieve the near infrared shielding performance required as a whole by combining with an infrared absorbing layer. And, near infrared rays can be shielded extremely efficiently without decreasing the transmittance of visible light.

  Next, each layer and each member will be described in detail.

[Near-infrared reflective layer]
The near-infrared reflective layer 1 has two layers, a first layer 1a and a second layer 1b, that transmit visible light but reflect near-infrared light, and have a specific circularly polarized light (and transmitted light) reflected by the two layers. There is no particular limitation as long as the turning directions of the specific circularly polarized light are opposite to each other, and a known layer can be used. For example, a cholesteric liquid crystal solidified layer can be used.

Examples of the cholesteric liquid crystal solidified layer include those disclosed in JP-A-2002-357717. This consists of a layer obtained by solidifying a cholesteric liquid crystal layer by a crosslinking reaction, cooling solidification or the like. In the cholesteric liquid crystal layer, the alignment direction of the molecular axes of the liquid crystal molecules is directed in a specific direction in a plane parallel to the front and back surfaces of the layer, and further proceeds from the back surface to the surface in the thickness direction of the layer. As a result of the orientation direction continuously rotating in one direction, the liquid crystal molecular axes have a structure (helix (three-dimensional helix) structure) in which the liquid crystal molecular axes are oriented like a tread of a spiral staircase as the thickness advances from the back surface to the front surface. The cholesteric liquid crystal solidified layer is solidified while maintaining such a helical molecular alignment state. In such a cholesteric liquid crystal solidified layer, circularly polarized light components rotating in the same direction as the rotation direction of the liquid crystal molecular axis spiral among the light incident on the front (or back) surface of the layer are selectively reflected. On the other hand, a specific circularly polarized light component rotating in the direction opposite to the rotation direction of the liquid crystal molecular axis spiral is selectively transmitted.
The reflectance of such selective reflection of circularly polarized light shows a maximum value at the wavelength λ ₀ of the following [Equation 1].
λ ₀ = nav · p [Formula 1]
Here, p is a helical pitch (also referred to as a helical pitch), and nav is an average refractive index in a plane perpendicular to the helical axis. This is also called a selective reflection wavelength.
The wavelength bandwidth Δλ in which circularly polarized light selective reflection occurs at this time is expressed by the following [Equation 2].
Δλ = Δn · p [Formula 2]
Here, Δn = n (parallel) −n (right angle), where n (parallel) is the maximum refractive index in the plane perpendicular to the helical axis, and n (right angle) is in the plane parallel to the helical axis. The maximum refractive index.

  A cholesteric liquid crystal solidified layer is a layer in which a cholesteric liquid crystal is solidified by a crosslinking reaction, a polymerization reaction or the like to fix a liquid crystal state, and as described above, of the light incident from one surface of the layer, a right circularly polarized light component (Or left circularly polarized light component, that is, a specific circularly polarized light component) is selectively reflected and the remaining component is an optical characteristic that transmits the left circularly polarized light component (or right circularly polarized light component) having the opposite direction of circularly polarized light. Have Such optical characteristics are that the layer has a cholesteric structure, and the circularly polarized light having the same optical rotation direction as that of the rotational direction is selectively reflected by appropriately setting the rotational direction in the spiral structure of the cholesteric structure. Therefore, it is known that the light beam reflected by the setting of the turning direction can be changed to right circularly polarized light or left circularly polarized light. The wavelength of the reflected light beam, that is, the selective reflection wavelength is equal to the helical pitch of the spiral structure, and the bandwidth of the reflected light beam with respect to the selective reflection wavelength is related to the birefringence of the layer. For this reason, the cholesteric liquid crystal solidified layer generally reflects and transmits near-infrared rays in a narrow wavelength band. Light rays outside the bandwidth range centered on the selective reflection wavelength are transmitted without being reflected.

Therefore, using only the solidified cholesteric liquid crystal layer to cut the near-infrared rays emitted from the display, a plurality of solidified cholesteric liquid crystal layers with different helical pitches are used, corresponding to multiple different selective reflection wavelengths. If it is not, it is not practical as described above in [Problems to be solved by the invention]. However, in the present invention, by using both the near-infrared reflective layer and the near-infrared absorbing layer by the cholesteric liquid crystal solidified layer in a predetermined arrangement, visible light is transmitted and the near-infrared is efficiently shielded. Therefore, for example, it is only necessary to obtain the final shielding performance with both the near-infrared absorbing layer and the near-infrared reflecting layer.
Further, if the selective reflection wavelength is brought to the near infrared region by utilizing the optical characteristics having a narrow bandwidth, it is possible to efficiently avoid a decrease in transmittance (due to reflection) in the visible light region.

Here, FIG. 5 is a diagram showing an example of a reflection spectrum and a transmission spectrum of the first layer that reflects only one circularly polarized light of the near-infrared reflective layer using the cholesteric liquid crystal solidified layer. A reflection and transmission spectrum centered around 1000 nm is shown.
The first layer of the near-infrared reflective layer exhibiting this spectrum is a single cholesteric liquid crystal solidified layer, and corresponds to the first layer 1a of the near-infrared reflective layer of Example 1.

  By the way, the selective reflection wavelength may be set according to the required performance, and is not particularly limited. However, from the viewpoint of efficiently suppressing the malfunction of the remote controller, the sensitivity characteristic of the receiver of the remote controller is considered. Is preferred. Therefore, the selective reflection wavelength is preferably in the range of 850 to 1100 nm. Further, the reflectance of light rays (near infrared rays) at the selective reflection wavelength in the first layer or the second layer of the near infrared reflection layer is preferably as large as possible, but the selective reflection characteristic of circularly polarized light is used. In terms of points, one of the right and left circularly polarized light is reflected and the other is transmitted, so ideally 50% of the half is the maximum (this point can be further increased in more detail later). ), And preferably 40% or more.

In addition, what is necessary is just to use a well-known thing suitably as a cholesteric liquid crystal material used for a cholesteric liquid crystal solidification layer, for example, liquid crystal compounds, such as polymerizable liquid crystal compounds, such as a polymerizable monomer compound and a polymerizable oligomer compound, and a liquid crystal polymer are used. can do. The polymerizable functional group exhibiting polymerizability in the polymerizable liquid crystal compound is typically an acrylate group, that is, an acryloyloxy group to an acryloyl group, but is not particularly limited. Such a polymerizable functional group usually has one end or both ends of the liquid crystal molecule. Moreover, as a cholesteric liquid crystal material, 1 type, or 2 or more types of liquid crystal compounds are used.
Further, as the cholesteric liquid crystal material, a liquid crystal material in which a compound exhibiting nematic liquid crystal properties and a chiral agent are used in combination is also suitable. As the chiral agent, known compounds can be used as appropriate.

  The thickness of the cholesteric liquid crystal solidified layer is not particularly limited as long as it is appropriately set according to the liquid crystal material, necessary reflection characteristics, and the like, but is, for example, 0.5 to 100 μm, and more preferably 1 to 10 μm.

The cholesteric liquid crystal solidified layer may be the first layer or the second layer of the near-infrared reflective layer by itself, but is laminated on an arbitrary base material, that is, from the base material and the cholesteric liquid crystal solidified layer, You may comprise the 1st layer of a near-infrared reflective layer, and a 2nd layer. Moreover, you may share a base material with other layers, such as a near-infrared absorption layer and an electromagnetic wave shielding layer.
For example, FIG. 2A shows a transparent substrate 5 between the near-infrared reflecting layer 1 and the near-infrared absorbing layer 2 as a layer that does not belong to these two layers. Thus, the laminated structure.
In addition, as a base material, although the transparent transparent base material 5 is fundamentally preferable, the colored transparent base material which gave the color-adjustment function by pigment | dye addition may be sufficient as a transparent base material, for example.

In addition, a cholesteric liquid crystal solidified layer may be laminated on the surfaces of various functional layers (described later). For example, the cholesteric liquid crystal solidified layer is laminated on the back surface of the base material provided in the antireflection layer, the back surface of the base material provided in the contrast enhancement layer, the back surface of the base material provided in the electromagnetic wave shielding layer, You may laminate | stack on the back surface of the base material with which the near-infrared absorption layer formed by construction is equipped. Here, the “back surface” means a surface opposite to the side where a functional layer such as an antireflection layer is laminated on the base material, and is a concept different from the display side and the viewer side.
Alternatively, a cholesteric liquid crystal solidified layer may be laminated on the functional layer. Various functional layers may be laminated on the cholesteric liquid crystal solidified layer. For example, a near infrared absorbing layer may be formed on the cholesteric liquid crystal solidified layer by coating.
The cholesteric liquid crystal solidified layer can be formed by a known forming method, for example, a composition containing a cholesteric liquid crystal material as described above by a known coating method such as roll coating, gravure roll coating, bar coating or the like. . Alternatively, lamination may be performed using a transfer method.
Further, the near-infrared reflective layer 1 has a structure in which the first layer 1a and the second layer 1b are laminated separately from each other, for example, with a transparent substrate 5 interposed therebetween as shown in FIG. As in (a), they may be laminated on one surface of the transparent substrate 5 while being in contact with each other.

  Then, using the cholesteric liquid crystal solidified layer, the first layer 1a and the first layer 1a form a second layer 1b in which the rotational direction of the circularly polarized light is opposite, and both the first layer 1a and the second layer 1b By constituting the near-infrared reflective layer, the right (or left) circularly polarized light is reflected by the first layer 1a, and the left (or right) circularly polarized light that has passed through the first layer 1a is reflected by the second layer 1b. Thus, the near-infrared reflective layer 1 can reflect not only one circularly polarized light of right (or left) circularly polarized light but also both right and left circularly polarized light. That is, it is a total reflection type near infrared selective reflection layer.

At this time, as the second cholesteric liquid crystal solidified layer, the first cholesteric liquid crystal solidified layer and the same circularly polarized light reflecting direction are used, and a retardation layer is provided between the first and second cholesteric liquid crystal solidified layers. The total reflection type near-infrared selective reflection layer can be obtained in the same manner by interposing the layer and reversing the direction of the circularly polarized light by the retardation layer.
That is, the second layer 1b can be composed of the same layer as the first layer 1a and the retardation layer with respect to the first layer 1a. In addition, as a cholesteric liquid crystal material, it is generally preferable to use a cholesteric liquid crystal material having a right spiral direction from the viewpoint of availability, cost, and the like. With such a configuration, the first layer 1a and the second layer 1b The circularly polarized light of the reflected light can be formed by using the same kind of cholesteric liquid crystal solidified layer in the turning direction.
At this time, the retardation of the retardation layer and the average retardation Re may be ½λ of a half wavelength, but values obtained by adding an integer of 1 or more to this, that is, 1.5λ, 2.5λ, 3.5λ, 5λ or the like is preferable in that the change in reflectance due to wavelength is small. The value of 1.5λ or the like may be shifted by about ± 0.2.
In other words,
Re = {(2n + 1) /2−0.2} × λ˜ {(2n + 1) /2+0.2} × λ [Formula 3]
It is.

[Near-infrared absorbing layer]
The near-infrared absorbing layer 2 is not particularly limited as long as it is a layer that transmits visible light but absorbs near-infrared light, and a known layer can be used. For example, it is a layer in which a near-infrared absorbing dye (NIRA dye) that absorbs near-infrared is dispersed in a matrix, and a resin binder is a typical matrix. A multilayer sputtered film by sputtering can also be used. Among these, a layer in which a near-infrared absorbing pigment is dispersed in a resin binder is representative. The near-infrared absorbing dye may be appropriately selected from organic and inorganic dyes and used alone or in combination of two or more, but in order to broaden the absorption wavelength band, two or more of them may be used in combination. preferable.

  Moreover, the near-infrared absorbing layer 2 in which the near-infrared absorbing dye is dispersed in the resin binder may be a layer combined with other functions. For example, a layer to which a near infrared absorbing dye is added, a pressure-sensitive adhesive layer, an electromagnetic wave shielding layer, a conductive composition layer as a primer layer, a contrast improving layer, or the like when a conductive primer layer is formed by a drawing primer type intaglio printing described later. And a near-infrared absorbing layer may be combined. Since the number of layers can be reduced by compounding, the number of manufacturing processes is reduced, leading to cost reduction. Or you may laminate | stack with another functional layer, for example, you may laminate | stack with an antireflection layer.

  In addition, what is necessary is just to select a well-known material suitably as an above-mentioned near-infrared absorption pigment | dye (NIRA pigment | dye) and a resin binder, for example, as an near-infrared absorption pigment | dye, an organic compound is an anthraquinone type compound, a naphthoquinone type | system | group. Compounds, phthalocyanine compounds, diimonium compounds, dithioneyl complexes and the like, and as inorganic compounds, indium tin oxide, titanium oxide, cesium-containing tungsten oxide disclosed in JP-A-2006-154516, etc. Is mentioned. Furthermore, if two or more types are used in combination, a combination of a phthalocyanine compound and a diimonium compound is a preferred example in addition to using a plurality of phthalocyanine compounds in combination. The phthalocyanine compound has an absorption band of 780 to 1000 nm, and the diimonium compound has a high absorption at 900 to 1100 nm and a high visible light transmittance. Can be absorbed.

Examples of the resin of the resin binder include an acrylic resin, a urethane resin, an epoxy resin, and a polyester resin, including the case where the adhesive layer is used.
In addition, the ratio in a matrix, such as a resin binder, of a near-infrared absorption pigment | dye is 0.001-15 mass% normally. Moreover, you may add various well-known additives, for example, antioxidant, a ultraviolet absorber, a photoreaction inhibitor, etc. as needed.
In addition, the near-infrared absorbing layer made of such a material can be formed by a known coating method such as roll coating, gravure roll coating or bar coating.

[Transparent substrate]
As illustrated in FIG. 2, the transparent substrate 5 may be used as a layer included in the near-infrared reflecting layer 1 or the near-infrared absorbing layer 2 or as a layer that is not included. Functions as a body.
There is no restriction | limiting in particular as the transparent base material 5, What is necessary is just to select and use a well-known thing suitably. For example, a resin film (or sheet), a resin plate, an inorganic material plate, or the like is representative. Examples of the resin of the resin film (or sheet) include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, polyolefin resins such as cycloolefin polymers, and cellulose resins such as triacetyl cellulose. Or polycarbonate resin, polyimide resin, and the like. As resin of a resin board, it is resin similar to the said resin film, for example. Examples of the material for the inorganic material plate include glass, quartz, and transparent ceramics. Among these, a biaxially stretched polyethylene terephthalate film is a suitable material in terms of cost, transparency, mechanical strength, and the like. In addition, the thickness of a transparent base material is about 12-5000 micrometers normally.

[Electromagnetic wave shielding layer]
The electromagnetic wave shielding layer 4 is not particularly limited as long as a known material is appropriately employed. For example, in addition to a commonly used metal mesh such as a copper etching mesh, it is a conductive layer such as a printed mesh using a conductive paste or the like, or a multilayer sputtered film formed on the entire surface instead of a mesh.
The copper etching mesh used is, for example, a copper foil processed into a mesh shape by chemical etching. In addition to copper, metals such as aluminum can also be used. The printed mesh is a conductive paste, for example, a conductive composition in which conductive particles such as silver are dispersed in a resin binder and printed on the mesh.
For the multilayer sputtered film, for example, ITO (indium tin oxide), silver or the like is used. Also, when the electromagnetic wave shielding performance is not so important, or when the electromagnetic wave itself is not generated from the display panel, the electromagnetic wave shielding layer is omitted, or a multilayer sputtered film is used and this is also used as a near infrared absorbing layer. You can also In that case, the cost can be reduced by reducing the number of sputtered layers.

  In addition, when forming a conductive composition layer as a printing mesh, what was formed by the drawing primer system intaglio printing method is preferable at the point which can form a high-definition mesh. The drawing primer type intaglio printing method is a printing method disclosed by the present applicant in Japanese Patent No. 4436441, and the ink filled in the concave portion of the intaglio plate surface is drawn to promote the transfer of the ink to the printing material. This is an intaglio printing method characterized in that a “primer layer”, which can also be called a “transition promoting layer”, acts in a fluid state during printing. For the primer layer, an ionizing radiation curable resin that is cured by ultraviolet rays or electron beams is preferably used.

  Moreover, the arrangement position of the electromagnetic wave shielding layer is basically not particularly limited. For example, the display panel side is closer to the near infrared absorption layer. In this way, when using an electromagnetic shielding layer such as a copper etching mesh or a mesh-like one such as a printing mesh, without placing a transparent resin layer on the mesh surface and protecting it, when placed as exposed, If the mesh is placed with the space facing the display panel side, it can be prevented that the mesh is damaged by unexpected external force.

[Other layers]
The near-infrared shielding filter for display according to the present invention may include other layers other than those described above as long as they do not depart from the gist of the present invention. For example, an optical filter layer that provides various optical filter functions, a functional layer that provides functions other than the optical filter function, and the like. As these layers, known layers can be appropriately employed.
The optical filter layer includes an ultraviolet absorbing layer, a neon light absorbing layer that absorbs neon light of the PDP, a color correction layer that corrects a display image to a desired color tone, an antireflection layer (antiglare, antireflection, antiglare and Any of anti-reflection)) and a contrast enhancement layer (such as a fine louver layer) described in Japanese Patent Application Laid-Open No. 2007-272161 for improving bright spot contrast. Moreover, as a functional layer that gives functions other than the optical filter function, an antifouling layer, an antistatic layer, a hard coat layer, a pressure-sensitive adhesive layer, a release film that protects the pressure-sensitive adhesive layer until use, an adhesive layer, For example, a primer layer and an impact resistant layer. In addition, these layers are single layers and may also have two or more functions.

[Position]
In the present invention, each of the layers described above requires a positional relationship in which the near-infrared reflecting layer 1 is disposed closer to the viewer V than the near-infrared absorbing layer 2, but there is no other limitation, and each layer has an arbitrary positional relationship. Can be arranged. However, as a matter of course, the antireflection layer for suppressing external light reflection is preferably closer to the observer than the near-infrared reflective layer, and the hard coat layer for preventing surface scratches (if it is a single layer) is also near-infrared. The observer side is preferable to the reflective layer. Needless to say, it is preferable to employ such a preferable positional relationship in the members disposed on the front surface of the display panel.

[Image display device]
The image display device 20 according to the present invention has a configuration in which the near-infrared shielding filter for display 10 as described above is arranged as the display panel 3 on the front surface of the plasma display panel, as described with reference to FIGS. 1B and 1C. It is. As the display panel 3, in particular, the plasma display panel, in principle, cannot emit near-infrared radiation from the display panel itself. Therefore, the effect of the present invention is more remarkable when applied to the plasma display panel.
Note that the near-infrared shielding filter for display of the present invention is useful as long as it emits near-infrared rays from the display panel to the viewer side, and may be applied to such a display panel.

[Usage]
The near-infrared shielding filter for display according to the present invention can be used for various applications. In particular, it is suitable for various display panels such as PDP and LCD, and particularly for front filters for PDP that have remarkable near-infrared radiation. In addition, an image display device in which such a near-infrared shielding filter for display is arranged on the front surface of a display panel such as a PDP is a television receiver, a measuring device or instrument, an office device, a medical device, a computer device, a telephone, It is used for display parts of electronic signboards and game machines.

  Next, the present invention will be described in further detail with reference to examples and comparative examples.

[Example 1]
(Near-infrared reflective layer)
As the near-infrared reflective layer 1, a transparent substrate 5 is used as a support, and a first layer 1a is formed on one side, a second layer 1b is formed on the other side, and a cholesteric liquid crystal solidified layer is laminated. did.
As the transparent substrate 5, a biaxially stretched polyethylene terephthalate film (Lumirror (registered trademark) U35, manufactured by Toray Industries, Inc.) having a thickness of 188 μm was prepared.
The retardation of the transparent base material has an average retardation Re of about 4083 nm, and for a near infrared wavelength of 1200 nm, 4083/1200 = 3.4, and the above-described [Equation 3], that is, Re = {(2n + 1) /2±0.2} × λ is satisfied.
However, for a wavelength of about 1000 nm of the reflection peak of selective reflected light to be described later, 4083/1000 = 4.1, and the above-described [Expression 3], that is, Re = {(2n + 1) /2±0.2}. Xλ is not satisfied.

  Preparation of the cholesteric liquid crystal solidified layer, as a Cholesteric liquid crystal material, has a polymerizable acrylate (acryloyloxy group, hereinafter the same) at both ends of the molecule, and has a spacer between the mesogen and the acrylate in the center, 96.95 parts of liquid crystalline monomer molecules (Paliocolor (registered trademark) LC1057 (manufactured by BASF)) and a chiral agent of the following formula (1);

A cyclohexanone solution in which 3.05 parts were dissolved was prepared. The cyclohexanone solution contains 2.5% by weight of a photopolymerization initiator (substance name: 1-hydroxy-cyclohexyl-phenyl-ketone, trade name: Irgacure (registered trademark) 184, manufacturer, based on the liquid crystal monomer molecules. A solution having a solid content of 40% by weight added by Ciba Specialty Chemicals).

Then, after applying the cyclohexanone solution on one surface of the transparent substrate with a bar coater without using an alignment film, the cyclohexanone in the solution is evaporated by heating at 120 ° C. for 2 minutes to obtain a liquid crystalline monomer. A coating film with oriented molecules was obtained. Next, the coating film is irradiated with ultraviolet rays, the acrylate in the liquid crystalline monomer molecule and the acrylate in the chiral agent molecule are three-dimensionally cross-linked to polymerize, and the cholesteric structure is fixed on the transparent substrate. A cholesteric liquid crystal solidified layer having a thickness of 5 μm was formed, and a laminated sheet in which the first layer 1 a composed of the transparent substrate 5 and the cholesteric liquid crystal solidified layer was formed was produced.
The reflection characteristic of the near-infrared reflective layer comprising the first layer 1a (measured with a spectrophotometer at a specular reflection angle of 5 °) rises from around 850 nm, has a reflection peak around 1000 nm, and has a base up to around 1200 nm. A reflection spectrum having a peak reflectance of 45% and a circularly polarized light selective reflection wavelength band Δλ defined as a half width of the reflectance of 167 nm is obtained, and the reflectance at the reflection peak is 45% and the base ( The reflectance in the wavelength region where the reflectance is not increased was 14%.

Next, as the second layer 1b of the near-infrared reflective layer 1, a cholesteric liquid crystal solidified layer is laminated on the other surface of the transparent substrate 5 on which the first layer 1a is formed. A near-infrared reflective layer 1 composed of the material 5 and the second layer 1b was produced.
Preparation of the cholesteric liquid crystal solidified layer, as a Cholesteric liquid crystal material, has a polymerizable acrylate (acryloyloxy group, hereinafter the same) at both ends of the molecule, and has a spacer between the mesogen and the acrylate in the center, 96.95 parts of liquid crystalline monomer molecules (Paliocolor (registered trademark) LC1057 (manufactured by BASF)) and a chiral agent of the following formula (2);

A cyclohexanone solution in which 3.05 parts were dissolved was prepared. The cyclohexanone solution contains 2.5% by weight of a photopolymerization initiator (substance name: 1-hydroxy-cyclohexyl-phenyl-ketone, trade name: Irgacure (registered trademark) 184, manufacturer, based on the liquid crystal monomer molecules. A solution having a solid content of 40% by weight added by Ciba Specialty Chemicals).
Thereafter, the second layer 1b was formed in the same manner as the first layer 1a, and the near-infrared reflective layer 1 provided with the transparent substrate 5 between these two layers was produced.

(Near-infrared absorbing layer)
As the near-infrared absorbing layer 2, an adhesive layer having a thickness of 25 μm containing a NIRA dye (near-infrared absorbing dye) was prepared on a release film.

In the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, first, an acrylic pressure-sensitive adhesive (an acrylic copolymer having a hydroxyl group and substantially free of a carboxyl group, SK-1811L manufactured by Soken Chemical Co., Ltd.) For 100 parts by mass, three types of NIRA dyes (all manufactured by Nippon Shokubai Co., Ltd.), 0.064 parts by mass of a phthalocyanine compound (Excolor (registered trademark) IR-14), and a phthalocyanine compound (Excolor (registered)) (Trademark) IR12) 0.090 parts by mass and phthalocyanine compound (Excolor (registered trademark) IR910) 0.162 parts by mass were added and sufficiently dispersed. Moreover, 3.34 parts by mass of 2,2′-dihydroxy-4-methoxybenzophenone (manufactured by CYTEC INDUSTRIES, Siasorb (registered trademark) UV24) as a benzophenone-based ultraviolet absorber and a hindered amine-based light stabilizer (Ciba Japan Co., Ltd.) 1.66 parts by mass, manufactured by TINUVIN (registered trademark) 144).
Furthermore, 2 mass parts of aromatic isocyanates (adducts of xylene diisocyanate and trimethylolpropane) were added in solid content and diluted with 30 mass parts of a diluent to prepare a pressure-sensitive adhesive composition.

The above pressure-sensitive adhesive composition is coated on the release surface of a release-treated polyethylene terephthalate film (Toyobo Co., Ltd., E7002) having a thickness of 100 μm as a release film with an applicator so that the film thickness when dried is 25 μm. Then, after drying at 70 ° C. for 3 minutes, a 75 μm-thick polyethylene terephthalate film having a thickness of 75 μm is laminated as a release film on both sides of the adhesive layer that is also used as a near-infrared absorbing layer. An adhesive film laminated with a release film was obtained.
In addition, the visible light transmittance of the adhesive layer of this adhesive film was 56%, and the transmittance from 850 nm to 1000 nm in the near infrared region was 25%.

(Near-infrared shielding filter for display)
The near-infrared reflective layer 1 provided with the transparent substrate prepared above and a polyethylene terephthalate film (A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm were combined with a near-infrared absorbing layer (also serving as a transparent substrate prepared above). The adhesive layer 2 was peeled off the release films on both sides and laminated via the near-infrared absorbing layer (also the adhesive layer) to produce a near-infrared shielding filter 10 for display.

(Evaluation of near-infrared shielding performance)
With the front glass filter removed from a commercially available plasma television and a white screen displayed as an image on the plasma display panel (PDP) 3, the near-infrared reflective layer 1 side of the display near-infrared shielding filter 10 is the observer V. It arranged so that it might face, and the brightness | luminance of the visible region and the near-infrared region was measured. The luminance measurement was performed using a spectral radiance meter in the visible light region, and a near infrared spectral radiometer in the near infrared region. The measurement was performed both when the infrared shielding filter for display 10 was installed and before (blank), and the transmittance at a predetermined wavelength was calculated from the luminance change before and after the installation.
As a result, the transmittance in the visible light region was 48%, and the transmittance at 850 to 1000 nm was 2%.

[Comparative Example 1]
Example 1 is the same as Example 1 except that the second layer 1b is omitted from the first layer 1a and the second layer 1b of the near-infrared reflective layer 1 and only the first layer 1a is used as the near-infrared reflective layer 1. In the same manner as described above, a near-infrared shielding filter for display was produced.
As a result, the visible light transmittance of the near-infrared shielding filter for display was 48%, and the transmittance from 850 nm to 1000 nm in the near-infrared region was 15%.

DESCRIPTION OF SYMBOLS 1 Near-infrared reflective layer 1a 1st layer of a near-infrared reflective layer 1b 2nd layer of a near-infrared reflective layer 2 Near-infrared absorption layer 3 Display panel (plasma display panel)
4 Electromagnetic wave shielding layer 5, 5a, 5b Transparent substrate 10 Near-infrared shielding filter for display 20 Image display device L Left circularly polarized light R Right circularly polarized light V Observer

Claims (3)

In an infrared shielding filter for a display which is disposed in front of a display panel and shields infrared rays emitted from the display panel.
In order from the observer side, it has at least a near-infrared reflective layer that transmits visible light and reflects near-infrared light, and a near-infrared absorption layer that transmits visible light and absorbs near-infrared light in this order,
The near-infrared reflective layer selectively reflects one circularly polarized light of right circularly polarized light or left circularly polarized light and transmits the other circularly polarized light, and the rotation direction of the circularly polarized light is opposite to the first layer. An infrared shielding filter for display, comprising a second layer that selectively reflects one circularly polarized light of left circularly polarized light or right circularly polarized light and transmits the other circularly polarized light.   The infrared shielding filter for display according to claim 1, further comprising an electromagnetic wave shielding layer closer to the display panel than the near infrared absorbing layer. The image display apparatus which has arrange | positioned the infrared shielding filter for displays of Claim 1 or 2 in the front surface of the plasma display panel.

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