JP2011107321A - Infrared light shielding filter for display and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared light shielding filter for display, arranged in front of a display panel and shielding infrared light emitted from the display panel, which efficiently shields near infrared light while suppressing reduction in transmittance in a visible light region. <P>SOLUTION: The infrared light shielding filter 10 for display has at least a near infrared light reflection layer 1 which transmits visible rays and reflects near infrared lights and a near infrared light absorbing layer 2 which transmits visible rays and absorbs near infrared lights in this order from an observer V side. As the near infrared light reflection layer, a layer which selectively reflects one circularly polarized light between right-handed circularly polarized light and left-handed circularly polarized light and transmits the other circularly polarized light, can be utilized. An electromagnetic wave shielding layer 4 can be provided on a side of the display panel 3 than the near infrared light absorbing layer. An image display apparatus 20 is constituted by arranging the infrared light shielding filter for display in front of the plasma display panel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a filter that is disposed in front of a display and shields infrared rays emitted from the display, and more particularly to a filter that can effectively shield 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, the plasma display has an optical filter on the front of the display panel. By the optical filter, the electromagnetic wave shielding function, infrared shielding function, neon light shielding function, toning function, contrast enhancement function, antireflection function, impact resistance function, etc. Various functions are realized. Among these functions, an infrared shielding function that cuts infrared rays includes 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. Widely used (Patent Document 1, Patent Document 2).

  Infrared shielding filters described in Patent Document 1 and Patent Document 2 are used alone in a resin sheet for NIRA dyes such as phthalocyanine compounds, benzopyran compounds, diimonium compounds, and antimony fluoride organic compounds. There are two or more types. Thereby, the absorption band is widened, and infrared rays are absorbed in a part or all of the wavelength band 800 to 1100 nm of near infrared rays emitted from the front surface of the PDP.

  Also, it does not absorb infrared rays using near-infrared absorbing dyes (abbreviated as NIRA (Near Infrared Absorbing) dyes), but reflects the infrared rays emitted from the display panel by a filter provided on the front surface. An infrared shielding filter that cuts infrared rays reaching the observer by returning to the original direction has also been proposed (Patent Document 3). In the 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 spiral axis of the cholesteric liquid crystal, but the rotational direction is reverse. Left (or right) circularly polarized light reflects infrared rays in the original direction by utilizing the property of transmitting.

  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 laminating steps increases. Therefore, there is a problem that a filter using a cholesteric liquid crystal solidified layer is more expensive than a filter using a NIRA dye.

  That is, an object of the present invention is to provide an infrared shielding for a display which can efficiently shield 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. To provide a filter. Another object of the present invention is to provide an image display device using such an infrared shielding filter for display.

Therefore, in the present invention, the configuration of the infrared shielding filter for display is as follows.
(1) A near-infrared reflection that is arranged in front of the display panel and shields infrared rays emitted from the display panel, and transmits visible light and reflects near-infrared light in order from the viewer side. It was set as the structure which has a layer and the near-infrared absorption layer which permeate | transmits visible light and absorbs near infrared rays at least in this order.
(2) Further, in the above configuration, the present invention has a configuration in which the near infrared reflection layer is a layer that selectively reflects one circularly polarized light of right circularly polarized light or left circularly polarized light and transmits the other circularly polarized light. .
(3) Further, according to the present invention, in any of the above-described configurations, an electromagnetic wave shielding layer is further provided on the display panel side than the near-infrared absorbing layer.

  Further, the image display device of the present invention is configured such that any one of the above-described 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 efficiently shielded while suppressing a decrease in transmittance in the visible light region.

Sectional drawing which illustrates one form (a) of the infrared shielding filter for displays by this invention, and two forms (b) and (c) of the image display apparatus which has arrange | positioned the infrared shielding filter for displays in the front surface of the plasma display panel. . Sectional drawing which illustrates another form example (transparent base material 5 was specified) about the infrared shielding filter for displays by this invention. Explanatory drawing explaining the mechanism of the infrared shielding filter for displays by this invention. Explanatory drawing explaining the mechanism of the infrared shielding filter of only an infrared reflective layer. The figure which shows an example of the spectrum of the transmittance | permeability of an infrared reflective layer, and a reflectance.

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

[Summary]
The infrared shielding filter for display of the present invention is a near infrared ray transmitting and reflecting near infrared ray in order from the observer V side, like the infrared shielding filter for display 10 whose one form is illustrated in FIG. The filter is configured to have at least an infrared reflection layer 1 and a near-infrared absorption layer 2 that transmits visible light and absorbs near-infrared light in this order.
The image display device 20 of the present invention has a configuration in which the display infrared shielding filter 10 as described above is disposed on the front surface of the plasma display panel as the display panel 3 as shown in FIG.
As a result, even when near-infrared rays are emitted from the display panel 3 to the viewer side, the near-infrared rays can be efficiently shielded 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.
“Transmit visible light and reflect near infrared light” and “Transmit visible light and absorb near infrared light” are relative absorption and reflection characteristics for visible light and near infrared light. It does not mean that all visible rays are transmitted and all near infrared rays are reflected or absorbed.

Further, in FIG. 1B, the display infrared shielding filter 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. . 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 infrared shielding filter 10 further includes the electromagnetic wave shielding layer 4 on the display panel 3 side. Are arranged on the front surface of the display panel 3 with an air space between them.

Moreover, the 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 infrared reflection layer or the infrared absorption layer, or a layer belonging to it. You may have as an upper layer which belongs.
For example, the infrared shielding filter for display 10 illustrated in FIG. 2A has a transparent substrate 5 between the infrared reflecting layer 1 and the infrared absorbing layer 2 as a support that does not belong to these layers. Further, in the infrared shielding filter 10 for display illustrated in FIG. 2B, the infrared reflecting layer 1 is composed of the transparent base material 5a and the infrared reflecting layer 1a from the observer V side, and the infrared absorbing layer 2 is the observer V side. From the infrared absorption layer 2a and the transparent base material 5b, the infrared reflection layer 1a and the infrared absorption layer 2a are in contact with each other.
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 earnest research, the present invention has found that near infrared rays can be efficiently shielded without reducing visible light transmittance by combining both the near infrared absorption layer and the near infrared reflection layer in a predetermined positional relationship. The mechanism will be described with reference to FIG.
First, in the present invention, as the predetermined positional relationship, as shown in FIG. 3, the near infrared absorbing layer 2 is arranged between the display panel 3 that emits infrared rays and the near infrared reflecting layer 1. . And in description of FIG. 3, the near-infrared reflective layer 3 demonstrates the case where near infrared rays are reflected as circularly polarized light.

  Near-infrared rays (1) emitted from the display panel 3 to the viewer V side are absorbed by the near-infrared absorbing layer 2. Near-infrared ray (2) that has passed without being absorbed by the near-infrared absorbing layer 2 is reflected by the near-infrared reflecting layer 1 to one of the left and right circularly polarized light, and a total of up to 50% is reflected, and the remaining rotational direction is The reverse circularly polarized near-infrared ray (3) reaches the eyes of the observer V. On the other hand, the near-infrared ray (4) reflected by the near-infrared reflecting layer 1 is reabsorbed when it passes through the near-infrared absorbing layer 2 again and passes therethrough. Near-infrared light (5) retransmitted through the near-infrared absorbing layer 2 is reflected by the display panel 3, travels again in the direction of the viewer V, repeatedly passes through the near-infrared absorbing layer 2, and is further attenuated. 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, when the near infrared ray (5) 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. Therefore, if the light reflected by the near-infrared reflective layer is right-handed circularly polarized light, the right-hand circularly polarized near-infrared light (5) is reflected by the display panel and when it comes to the near-infrared reflective layer again, it becomes left-handed circularly polarized light. It has become. This left circularly polarized near-infrared light passes through the near-infrared reflective layer, but there is a near-infrared absorbing layer between the display panel and the near-infrared reflective layer. Therefore, the near-infrared ray can be shielded more effectively than the case of using only the near-infrared reflective layer.
When the positional relationship between the near-infrared reflecting layer 1 and the near-infrared absorbing layer 2 is reversed, even if the near-infrared reflecting layer reflects the near-infrared light as the light transmitted through the near-infrared reflecting layer, the near-infrared absorbing layer. Can not be shielded effectively as described above.

  With such a configuration, as compared with 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 about half by simple calculation. On the other hand, in the case where 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 half. In this case, the 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 by half. For this reason, the visible light transmittance can be increased by reducing the concentration of the near-infrared absorbing dye in the near-infrared absorbing layer. 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, as shown in FIG. 4, when only the near-infrared reflective layer 1 is used, it becomes as follows, and so near-infrared shielding performance cannot be expected. In FIG. 4, the near-infrared reflective layer 1 reflects near-infrared rays using circularly polarized light as in the case of FIG. That is, the 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 in the near-infrared reflective layer 1, and a total of 50% is reflected and the remaining 50%. Near infrared (3) reaches 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 infrared rays (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 described above, in the present invention, near-infrared rays can be efficiently shielded without lowering the transmittance of visible light, which is unprecedented. Next, each layer and each member will be described in detail.

[Near-infrared reflective layer]
The near-infrared reflective layer 1 is not particularly limited as long as it is a layer that transmits visible light but reflects near-infrared light, and a known layer can be used. For example, a multilayer interference film, a cholesteric liquid crystal solidified layer, a wire grid polarization separation film, or the like can be used for the near infrared reflection layer.

Examples of the polarization separation film made of a multilayer interference film include those disclosed in, for example, [0015] to [0020] of Japanese Patent No. 3709402, FIG. This is because the refractive index of light in a predetermined wavelength region has anisotropy in a plane parallel to the front and back surfaces, has a maximum refractive index in a certain direction, and a minimum refractive index in a direction perpendicular to this. A / B / A / B / A / B in which the resin A having a refractive index and the resin layer B having an isotropic refractive index in a predetermined wavelength region regardless of the direction in the front and back surfaces are alternately formed. / A / B is a multi-layered structure of about 100 to 500 layers. Here, examples of the resin A include polyethylene naphthalate. Examples of the resin B include ethylene glycol-naphthalenedicarboxylic acid-terephthalic acid copolymer.
When the minimum refractive index value of the A layer is matched with the refractive index value of the B layer, out of the light incident on the multilayer interference film, in the in-plane direction (the fast axis direction) indicating the minimum refractive index of the A layer The oscillating polarization component (having an electric field) is transmitted through the multilayer interference film. On the other hand, the polarization component that vibrates (has an electric field) in the in-plane direction (slow axis direction) indicating the maximum refractive index of the A layer is reflected by the multilayer interference film.

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, the 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 λ0 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 (‖) −n (right angle), n (‖) is the maximum refractive index in a plane perpendicular to the helical axis, and n (right angle) is in a plane parallel to the helical axis. The maximum refractive index.
The cholesteric liquid crystal solidified layer will be specifically described later separately.

Examples of the wire grid polarization separation film are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 58-42003, 63-168626, 2006-330616, and US Pat. No. 7,158,302. It is a thing. This is a large number of metal filaments that are longer than the wavelength of light in a predetermined wavelength region and narrower than the wavelength of light in a predetermined wavelength region, and are arranged in parallel with a gap in between. Consists of structure. Usually, the arrangement of the metal filament groups is laminated on a transparent substrate such as a glass plate or a resin sheet.
Of the light incident on the wire grid polarization separation film, the polarization component that vibrates in the longitudinal direction of the metal filament (has an electric field) is reflected by the wire grid polarization separation film. On the other hand, the polarization component (having an electric field) that vibrates in the width direction of the metal filament passes through the wire grid polarization separation film.

  Note that the above-described document itself discloses a polarization separation layer within a predetermined wavelength bandwidth in the visible light region. On the other hand, when these techniques are applied to the near-infrared reflective layer of the present invention, specifications (parameters, etc.) for determining the wavelength at which polarization separation occurs in the polarization separation layers of the respective forms disclosed in these documents. By adjusting and setting a wavelength band in which selective reflection of specific polarized light occurs to a desired near infrared band, it functions as an infrared selective reflection layer. Of these infrared selective reflection layers, what to use may be selected comprehensively, including the required physical properties and cost, etc. Among them, the cholesteric liquid crystal solidified layer is in comparison with multilayer interference films and wire grid polarizing films. Cost is advantageous.

  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 the left circularly polarized component) is selectively reflected, and the remaining component has an optical characteristic of transmitting the left circularly polarized component (or the right circularly polarized component) having the opposite direction of the circularly polarized light. 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 provided in the near-infrared region by utilizing the optical characteristics with a narrow bandwidth, it is possible to effectively avoid the 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 a near-infrared reflective layer using a cholesteric liquid crystal solidified layer, and shows a reflection and transmission spectrum centered around 1000 nm.
The near-infrared reflective layer exhibiting this spectrum is a single cholesteric liquid crystal solidified layer and corresponds to 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 effectively 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. In addition, the reflectance of light rays (near infrared rays) at the selective reflection wavelength is preferably as large as possible. However, from the viewpoint of using the selective reflection characteristics of circularly polarized light, either the right or left circularly polarized light is reflected and the other is transmitted. Therefore, ideally, 50% of the half is the maximum (the point where this maximum value can be further mentioned will be described in detail later).

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.
As the cholesteric liquid crystal material, it is preferable to use a cholesteric liquid crystal material having a right spiral direction from the viewpoint of easy availability and cost.

  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, 0.1 to 100 μm, more preferably 0.5 to 20 μm, still more preferably 1 to 1. 10 μm.

The cholesteric liquid crystal solidified layer may be a near-infrared reflective layer by itself, but the near-infrared reflective layer may be composed of a layer laminated on an arbitrary base material, that is, the base material and the cholesteric liquid crystal solidified 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, it is laminated on the back surface of the base material provided in the antireflection layer, laminated on the back surface of the base material provided in the contrast improving layer, laminated on the back surface of the base material provided in the electromagnetic wave shielding layer, or near-infrared formed by coating. You may laminate | stack on the back surface of the base material with which an absorption layer is provided. 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. .

  The near-infrared reflective layer using the cholesteric liquid crystal solidified layer may further include a layer in which the direction of the circularly polarized light to be reflected is reverse. Accordingly, the right (or left) circularly polarized light is reflected by the first cholesteric liquid crystal solidified layer, and the left (or right) circularly polarized light that has passed through the layer is reflected by the first cholesteric liquid crystal solidified layer. By reflecting with the second cholesteric liquid crystal solidified layer in the reverse direction, the near-infrared reflecting layer as a whole reflects not only one of the right (or left) circularly polarized light but also the right and left circularly polarized light. It can also be made. 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. The retardation of the retardation layer and the average retardation Re may be ½λ of a half wavelength, but a value obtained by adding an integer of 1 or more to this, that is, 1.5λ, 2.5λ, 3.5λ, 4.5λ, etc. Is preferable in that the reflectance change due to wavelength is small. The value of 1.5λ or the like may be shifted by about ± 0.2.
That means
Re = {(2n + 1) /2±0.2} × λ [Formula 3]
It is. This configuration is also a configuration of Example 2 and Example 3 described later.

[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, an adhesive layer, an electromagnetic wave shielding layer, a conductive composition layer as a primer layer, a contrast improving layer, and the like when forming a conductive primer layer by a drawing primer type intaglio printing described later, A near infrared absorption 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 series Compounds, phthalocyanine compounds, diimonium compounds, dithioneyl complexes and the like, and inorganic compounds include 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 an 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 for the resin film (or sheet) include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins, polycarbonate resins, polyimide resins, polyolefin resins such as cycloolefin polymers, and triacetyl cellulose. Cellulosic 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 is, for example, a copper foil made into a mesh shape by chemical etching. In addition to copper, metals such as aluminum are also possible. Moreover, for example, a printed mesh is formed as a conductive composition layer in which a conductive composition in which conductive particles such as silver are dispersed in a resin binder is used for the conductive paste.
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 International Publication No. WO2008 / 149969, 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. The intaglio printing method is characterized in that a “primer layer”, which can 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 infrared shielding filter for display according to the present invention may include other layers other than those described above as long as it does 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 display infrared shielding filter 10 as described above is disposed as the display panel 3 on the front surface of the plasma display panel, as described in FIGS. 1B and 1C. is there. As the display panel 3, in particular, the plasma display panel cannot in principle ignore the infrared radiation from the display panel itself, and the effect of the present invention is more remarkable when applied to the plasma display panel.
Note that the infrared shielding filter for display according to 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 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, LCD, etc., especially for front filters for PDP that have remarkable infrared radiation. In addition, an image display device in which such an 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, an electronic device. Used for signboards, display units of game machines, etc.

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

[Example 1]
(Near-infrared reflective layer)
A near-infrared reflective layer 1 was prepared by laminating a cholesteric liquid crystal solidified layer on a transparent substrate 5 as a support.
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 is 4083/1200 = 3.4 with respect to a near infrared wavelength of 1200 nm, and the above-described [Equation 1], that is, Re = { (2n + 1) /2±0.2} × λ was 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 having a polymerizable acrylate at both ends of the molecule (Paliocolor (registered trademark) LC756 (manufactured by BASF)) 3 A cyclohexanone solution in which 0.05 part was 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 near-infrared reflective layer 1 composed of a transparent substrate 5 and a cholesteric liquid crystal solidified layer was produced.

The reflection characteristic of this near-infrared reflective layer (measured with a spectrophotometer at a regular reflection angle of 5 °) rises from around 850 nm, and a reflection spectrum having a reflection peak around 1000 nm is obtained. The reflectance at the reflection peak is 45. %, The reflectivity of the base (wavelength region where the reflectivity is not increased) was 14%.

(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%.

(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 pressure-sensitive adhesive layer 2 was peeled off the release films on both sides and laminated via the near-infrared absorbing layer (also the pressure-sensitive adhesive layer) to produce an 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 infrared shielding filter 10 is on the viewer V side. The luminance in the visible light 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 15%.

[Comparative Example 1] (Dye concentration increased only with near-infrared absorbing layer without near-infrared reflecting layer)
In Example 1, the near-infrared reflecting layer 1 was omitted, and an infrared shielding filter for a display having a configuration including only the near-infrared absorbing layer 2 was produced. However, the near-infrared absorbing layer 2 increased the dye concentration of the NIRA dye in the layer. As a result, the visible light transmittance of the infrared shielding filter for display was 30%, and the transmittance from 850 nm to 1000 nm in the near infrared region was 5%.

[Example 2] (Two layers of cholesteric liquid crystal solidified layer with a near-infrared reflective layer sandwiching a transparent substrate (retardation layer))
In Example 1, a laminate film having a layer configuration of [cholesteric liquid crystal solidified layer / transparent substrate] prepared as a near-infrared reflective layer was further laminated [cholesteric liquid crystal solidified layer / transparent substrate (retardation layer)]. / Cholesteric liquid crystal solidified layer / transparent substrate] A two-layer laminated film having a constitution was prepared as a near-infrared reflective layer in this example.
When the reflection characteristics of the near-infrared reflective layer were measured in the same manner as in Example 1, a reflection spectrum rising from around 850 nm and having a reflection peak around 1000 nm was obtained. The reflectance at the reflection peak was 88%, and the reflection of the base The rate was 14%.

  The near-infrared absorbing layer has the same near-infrared absorbing layer as that of Example 1, except that the NIRA dye concentration in the layer is changed, the visible light transmittance is 45%, and the transmittance in the near-infrared region is 850 nm to 1000 nm. Used a near-infrared absorbing layer of 15%. The dye concentration of the NIRA dye was 0.09 parts by mass of the phthalocyanine compound (Excolor (registered trademark) IR-14) and the phthalocyanine compound (Excolor (registered trademark) IR12) 0 in the blending amount of Example 1. 126 parts by mass and 0.226 parts by mass of a phthalocyanine compound (Excolor (registered trademark) IR910).

  Thereafter, in the same manner as in Example 1, the display was laminated in such a direction that the near-infrared absorbing layer (adhesive layer) was in contact with the surface of the transparent substrate provided in the near-infrared reflecting layer to produce an infrared shielding filter for display. As a result, the visible light transmittance of the infrared shielding filter for display was 38%, and the transmittance from 850 nm to 1000 nm in the near infrared region was 4%.

[Example 3] (Nira dye concentration reduced in Example 2)
In Example 2, the near-infrared absorbing layer identical to that in Example 1 was reduced in the concentration of the NIRA dye in the layer, and the visible light transmittance was increased to 67%. An infrared shielding filter for display was produced in the same manner as in Example 2 except that the 39% near infrared absorbing layer was used. As a result, the visible light transmittance of the infrared shielding filter for display was 58%, and the transmittance from 850 nm to 1000 nm in the near infrared region was 10%.

[Comparative Example 2] (NIRA dye concentration reduction with only near-infrared absorbing layer)
In Example 1, the near-infrared reflective layer was omitted, and an infrared shielding filter for a display having a configuration including only the near-infrared absorbing layer was produced. However, in the near infrared absorption layer, when the NIRA dye concentration in the layer is reduced and the visible light transmittance is 58%, the infrared shielding filter for display increases the transmittance of 850 nm to 1000 nm in the near infrared region to 28%. It was. Therefore, when the visible light region transmittance comparable to that of Example 3 was ensured, the transmittance in the near-infrared region was more than doubled, and the near-infrared shielding performance deteriorated.

[Comparative Example 3] (No near infrared absorbing layer in Example 2)
In Example 2, an infrared shielding filter for display having a configuration in which only the near-infrared reflecting layer was omitted and the near-infrared absorbing layer was omitted was prepared. As a result, the transmittance of 850 nm to 1000 nm in the near infrared region of the infrared shielding filter for display was 87%.

1 Near-infrared reflective layer 2 Near-infrared absorbing layer 3 Display panel (plasma display panel)
4 Electromagnetic wave shielding layer 5, 5a, 5b Transparent substrate 10 Infrared shielding filter for display 20 Image display device V Observer

Claims (4)

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.
An infrared shielding filter for a display having at least a near-infrared reflecting layer that transmits visible light and reflects near-infrared light and a near-infrared absorbing layer that transmits visible light and absorbs near-infrared light in this order from the viewer side.   The infrared shielding filter for a display according to claim 1, wherein the near-infrared reflective layer is a layer that selectively reflects one circularly polarized light of right circularly polarized light or left circularly polarized light and transmits the other circularly polarized light.   The infrared shielding filter for display according to claim 1, wherein the electromagnetic shielding layer is provided 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 any one of Claims 1-3 in the front surface of the plasma display panel.

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