JPH0816081A - Hologram recording sheet - Google Patents

Abstract

PURPOSE:To provide a hologram recording sheet which does not generate undesirable interference fringes. CONSTITUTION:The hologram recording sheet is composed of a volume type and phase type sensitizer 3 for hologram recording, and a flexible film 4 provided on the sensitizer 3, and as a film 4 to remove a stray light to be a cause to generate unnecessary interference fringes owing to an interface reflection, a film which a coloring process is applied is used. In the coloring processed film, the permeating light intensity necessary for hologram recording is reduced following the reduction of permeability, but the ratio of the stray light can be reduced proportionally to the square of the permeability, and thereby, the generation of undeirable interference fringes can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram recording sheet, and more particularly to a hologram recording sheet with reduced generation of unwanted interference fringes.

[0002]

2. Description of the Related Art In recent years, holograms have come to be widely used for decoration, forgery prevention, optical elements, and the like. In particular, recently, volume phase having excellent wavelength selectivity and excellent three-dimensional appearance has been obtained. Type (Lippmann type) holograms are drawing attention.

For example, the hologram combiner is one optical element, and its function can be said to be a semitransparent coupling element. FIG. 9A is a diagram for explaining the photographing method, in which the light oscillated from the laser 10 is divided into two by the half mirror 11, and each laser light is divided into the lens 1 by the lens 1.
A holographic combiner is used to perform divergent light emission from one point at 2 and 13, and to make these two divergent light beams enter from both sides of the volume phase hologram recording material 14 such as a photopolymer to perform interference recording as Lippmann hologram.

Such a hologram combiner 16
As shown in (b) of the figure, the light emitted from the display body 15 installed near one of the divergence points at the time of shooting is diffracted in the reflection direction, and the diffraction is as if the other divergence point at the time of shooting. It is performed as if it came out from the display object image 15 'installed in the vicinity,
The coupling magnification and the image position are determined by the relative distances L and L ′ between the divergence point at the time of photographing and the recording material 14, and only diffract only the wavelength at the time of recording or the wavelength having a specific relationship with it. Since light of other wavelengths is transmitted, the images can be superimposed or combined. As a hologram optical element represented by such a hologram combiner, there is a combiner for head-up display and the like.

By the way, the above-mentioned volume phase hologram recording light-sensitive material is usually made of PET as shown in the cross section of FIG.
A flexible film 1 of (polyethylene terephthalate) coated with a photosensitive material 3 such as a photopolymer is used. In FIG. 7, another flexible film 2 made of PET is attached on the photosensitive material 3 to form a dry film.

[0006]

However, in the above-mentioned conventional technique, when hologram recording is performed on the film having the form as shown in FIG. 7, the unwanted interference fringes (as shown in FIG. A phenomenon in which a grain pattern (a), a contour pattern (b), and a stripe pattern (c) are recorded is observed. This is due to birefringence of the PET film 1, reflection due to a large difference in refractive index between the PET film 1 and the sensitive material 3 (PET: 1.67, sensitive material: near 1.5), and reflection at the film-air interface. Is. The refractive indexes of volume phase hologram recording materials represented by photopolymers are all around 1.5.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a hologram recording sheet in which unwanted interference fringes do not occur.

[0008]

[Means for Solving the Problems] As a result of various studies to solve the above-mentioned problems, PE was used as a flexible film.
Instead of the T film, a film containing triacetyl cellulose (n = 1.48) as a main component, which has a low birefringence and a refractive index close to that of the photosensitive material of 1.5, or
The present invention has been completed by finding that the above problems can be solved by using a film containing polymethacrylate (n = 1.50) as a main component, and by using a semitransparent flexible film. It has come to.

Since triacetyl cellulose and polymethacrylate are soluble in organic solvents, it is not possible to dissolve them in an organic solvent and apply a photosensitive material such as a photopolymer.
Generally difficult. In such a case, a polyvinyl alcohol layer as a barrier layer is applied as an aqueous solution, dried, and then coated with triacetyl cellulose or polymethacrylate.

It is also effective to use a dyed film (ND film) in order to remove stray light which causes unnecessary interference fringes due to interface reflection.

That is, the hologram recording sheet of the present invention is a hologram recording sheet in which a photosensitive material layer is provided on a flexible film, wherein the flexible film is semi-transmissive at the recording wavelength.

In this case, the transmittance of the flexible film at the recording wavelength is preferably in the range of 70% to 1%, more preferably 50% to 10%.

The flexible film is preferably made of a dyed resin containing triacetyl cellulose as a main component or a dyed resin containing polymethacrylate as a main component.

Further, it is preferable to provide a resin layer containing polyvinyl alcohol as a main component as a barrier layer between the flexible film and the photosensitive material layer.

[0015]

The above-mentioned present invention will be described below. The hologram recording sheet of the present invention is basically formed with a layer structure as shown in FIG. Here, the flexible film 4 is a film made of a resin whose main component is triacetyl cellulose or polymethacrylate. As the hologram sensitive material 3, a conventionally known volume type and phase type sensitive material for hologram recording such as photopolymer can be used.

The layer structure as shown in FIG. 1A is formed by printing the hologram photosensitive material 3 on the flexible film 4 by a known coating method such as gravure coating, roll coating, blade coating, die coating and the like. It can be obtained by laminating a PET film 2 for forming a dry film form on the above.

When the hologram photosensitive material 3 is coated with a solvent that dissolves the flexible film 4, the polyvinyl alcohol (PVA) layer 5 is applied and dried on the film 4 in advance. In this case,
The layer structure is as shown in (b).

As the flexible film 4,
When the ND dyeing process is performed, it is possible to more effectively reduce the generation of undesired interference fringes due to interface reflection. In particular, as shown in FIG. 2, it is more effective when the hologram sensitive material 3 is attached to the hologram original plate 6 and duplicated by S-polarized light. This is for the following reasons.

When the intensity of the incident light is 100% (partial), when replicating through an AR coated glass coated with an antireflection film instead of the flexible film 4, at a very limited design wavelength and incident angle. , A
The reflectance from the surface of the R-coated glass can be suppressed to about 0.3%, and the transmitted light intensity (part) effective for hologram recording is about 99.7%. Similarly, the intensity of the (partial) reflected light that is incident on and reflected from the surface of the AR-coated glass, which causes unnecessary interference fringes, can be suppressed to about 0.3%. As described above, in the case of the method of copying via the AR-coated glass, normally, the AR-coated glass is laminated via the refractive index matching liquid (IMF) to perform stacking for replication.

However, in the case where the AR-coated glass has a wide wavelength range and a wide angle range, the above-mentioned reflectance is lowered due to the angle selectivity inherent to the glass. For example, the wavelength is 450 nm to 650 nm, the incident angle I
_{When 1} is from 0 ° to 60 °, it is difficult to reduce this to 2% or less in the entire region even if it is optimized.
On the other hand, as shown in FIG. 2, when the ND film 4 is interposed, the stray light intensity can be relatively reduced as follows.

As shown in FIG. 2, the incident light intensity is A (pass), the transmitted light intensity is B (pass →), the diffracted light intensity is C (pass →→), and the stray light intensity is D (pass →→).
→), n ₁ is the refractive index of air (1.0), n ₂ is the refractive index of the ND film 4 (the same applies to the photosensitive material 3 and the original plate 6), I ₁ is the incident light angle, I ₂ is the refracted light angle, Stray light intensity / transmitted light intensity = D / B is calculated, where r is the reflectance at the air-film 4 interface, t is the transmittance at the air-film 4 interface, and T is the vertical transmittance of the ND film 4.

From the law of refraction, n ₁ sinI ₁ = n ₂ sinI ₂ I ₂ = sin ^-1 {(n ₁ / n ₂ ) .sinI ₁ }. In the case of S-polarized light (polarization direction at duplication),
From the Fresnel formula, r = {sin (I ₁ −I ₂ ) / sin (I ₁ + I ₂ )} ² . Here, when the transmittance of the ND film 4 at the refraction angle I ₂ is T ′, log (1−T) / log (1−T ′) = cosI ₂ T ′ = 1− (1−T) ^{(1 / cosI2)} , and the transmitted light intensity B is B = t × A × T ′.

The stray light intensity D is D = r × C × T '× T'. As described above, the ratio of stray light is proportional to the square of the transmittance T ′, and thus the ratio of the stray light sharply decreases as the transmittance increases.

Using the above equation, T is 100, 70, 60, 50, 40, 30, 20, 10 when the interface reflection between the photosensitive material 3 and the original 6 is set to 0 and the diffraction efficiency in the original 6 is 100%. %
The transmitted light intensity (B) and the stray light intensity (D) of the ND film 4 of No. 4 are calculated, and the stray light intensity / the transmitted light intensity (D /
B) was calculated. The results are shown in Table-1, Table-2 and Table-3. Also, graphs of these are shown in FIGS. 3, 4, and 5, respectively.

[0025]

[0026]

[0027]

In this way, the dyed film 4 is
Although the transmitted light intensity necessary for hologram recording decreases as the transmittance decreases, the ratio of stray light is 2% of the transmittance.
Since it can be reduced in proportion to the power, it is extremely effective in suppressing undesired interference fringes as shown in FIG.

As described above, considering that about 2% of stray light is generated even when the AR coated glass is used,
3, the transmittance of the ND film 4 is 70% or less at an incident angle of 0 ° to 10 °, 60% or less at an incident angle of 15 ° to 30 °, 50% or less at an incident angle of 35 ° to 45 °, and an incident angle of 50.
40% or less at 60 ° to 60 °, 30 at 65 ° or more
% Or less, and in the case of a normal incident angle of 40 ° to 60 °, it is preferably 50% or less. When the transmittance is 30% or less, the stray light ratio is 1% at a practical incident angle.
It can be reduced to below, and the performance is superior to AR coated glass. Also, the lower limit of the transmittance may be larger than 1%,
If it is too small, the recording time will be long, so it is practically 1
0% or more is preferable.

By the way, the total duplication time greatly contributes to the duplication productivity and cost of holograms. The duplication time when using AR coated glass is the time to attach to the original plate: t ₁ IMF development stack time: t ₂ standing time: t ₃ recording time: t ₄ stack open IMF processing time: t ₅ original plate Peeling time: Sum of t ₆ ST ST = t ₁ + t ₂ + t ₃ + t ₄ + t ₅ + t ₆ .

On the other hand, when the ND film 4 is used, the time of sticking to the original plate: t ₁ 'recording time: t ₄ ' the time of peeling from the original plate: t ₆ ', and the sum ST' ST ' = the _{t 1 '+ t 4' +} t 6 '.

Since t ₁ = t ₁ ′ and t ₆ = t ₆ ′,
The difference between the two is (AR coated glass)-(ND film) = t ₂ + t ₃
+ T is _{4 + t 5 -t 4 '=} t 2 + t 3 + t 5 + (t 4 -t 4').

Therefore, when the ND film 4 was used according to the present invention, the AR coated glass was used in comparison with the increase amount of the recording time (t ₄ -t ₄ ′) accompanying the decrease of the transmitted light intensity. Time required at times (t ₂ + t ₃ +
When t ₅ ) is large, it can be seen that the present invention using the ND glass 4 is more advantageous from the viewpoint of productivity. Further, in the case of the present invention, since the index matching liquid (IMF) is not used, there is an advantage that the problems such as the flow and the inclusion of bubbles generated when the IMF is used do not occur.

[0034]

EXAMPLES Examples of the hologram recording sheet of the present invention will be described below together with comparative examples. Example 1 A 100 μm thick triacetyl cellulose (Fujitac: Fuji Photo Film Co., Ltd.) was dyed with a diphenylamine-based and anthraquinone-based disperse dye to produce a film having the spectral characteristics shown in FIG. On top of this, polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.,
Gohsenol NM-11) was applied as an aqueous solution to a thickness of 5 μm and dried. A full-color hologram sensitive material (Omnidex 705: manufactured by DuPont) having sensitivity to R, G, and B is laminated on this film, and PE is laminated thereon.
The T film was laminated to prepare a hologram recording film of the present invention composed of dyed triacetyl cellulose / PVA / sensitive material / PET.

PET of this hologram recording film was peeled off and laminated on the hologram master plate to form a stack of dyed triacetyl cellulose / PVA / sensitizer / hologram master plate, and hologram duplication was performed. Duplication wavelength is 488 nm (argon laser), 578 nm
(Die laser), 647nm (Krypton laser)
And the incident angle was 50 ° in all cases.

When the diffraction efficiency of unnecessary interference fringes due to stray light of the obtained duplicate hologram was measured, it was 2% or less, and it was good with almost no unnecessary interference fringes.

Example 2 On a PET film having a thickness of 100 μm, a solution obtained by mixing an acrylic resin (BR resin: manufactured by Mitsubishi Rayon Co., Ltd.) with diphenylamine-based and anthraquinone-based disperse dyes and a plasticizer was prepared to a thickness of 50 μm. Was coated and dried to prepare a film having the spectral characteristics shown in FIG. On this, polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd., Gohsenol NM-11) was added as an aqueous solution to give 5
The PET film was removed after coating to a thickness of μm and drying. A full-color hologram sensitive material having sensitivity to R, G, and B (Omnidex 705: manufactured by DuPont) is laminated on this film, and a PET film is laminated thereon, and dyed polymethylmethacrylate / PVA /
A hologram recording film of the present invention composed of a light-sensitive material / PET was produced.

PET of this hologram recording film was peeled off and laminated on the hologram master plate to form a stack of dyed polymethylmethacrylate / PVA / sensitizer / hologram master plate, and hologram duplication was performed. Duplication wavelength is 488 nm (argon laser), 578 nm
(Die laser), 647nm (Krypton laser)
And the incident angle was 50 ° in all cases.

When the diffraction efficiency of unnecessary interference fringes due to stray light of the obtained duplicate hologram was measured, it was 2% or less, and it was good with almost no unnecessary interference fringes.

Comparative Example 1 Polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd.) was coated on a PET film having a thickness of 100 μm.
Manufactured by Gosenol NM-11) as an aqueous solution to a thickness of 5 μm, dried, and then laminated with a full-color hologram sensitive material (Omnidex 705: manufactured by DuPont) having sensitivity to R, G, and B, and PET. The film was laminated to prepare a hologram recording film composed of PET / PVA / sensitive material / PET, and hologram duplication was performed in the same manner as in Example 1. The obtained hologram had many unwanted interference fringes due to stray light and was of poor quality.

Comparative Example 2 PET / PV of Comparative Example 1 above
AR coated glass was placed on a stack consisting of A / sensitized material / holographic original plate, and xylene was used as a refractive index matching liquid.
A stack to be R-coated glass / IMF / PET / PVA / sensitive material / hologram master plate was formed, and hologram duplication was performed in the same manner as in Example 1. The obtained hologram is
Compared with Comparative Example 1, although there were few unnecessary interference fringes due to stray light, there were still many unnecessary interference fringes and the quality was poor.

[0042]

As is apparent from the above description, according to the present invention, it is possible to reduce the generation of undesired interference fringes that existed when the conventional hologram recording sheet was used. It is possible to obtain a holographic combiner suitable for a head-up display having excellent quality. Further, it is not limited to such a combiner for head-up display, but is also used for volume phase type (Lippmann type) hologram recording for decoration, anti-counterfeiting, and other optical elements that require high appearance quality. can do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of a hologram recording sheet of the present invention.

FIG. 2 is a diagram for explaining the behavior of light in the case of hologram original copy.

FIG. 3 is a graph showing transmitted light intensity according to the transmittance of a flexible film.

FIG. 4 is a graph showing stray light intensity according to the transmittance of a flexible film.

FIG. 5 is a graph showing stray light intensity / transmitted light intensity according to the transmittance of the flexible film.

FIG. 6 is a graph showing spectral characteristics of the flexible film of each example.

FIG. 7 is a cross-sectional view showing a layer structure of a conventional hologram recording sheet.

FIG. 8 is a diagram showing a pattern of undesired interference fringes.

FIG. 9 is a diagram for explaining an imaging method and an operation of the hologram combiner.

[Explanation of symbols]

 2 ... PET film 3 ... Holographic material 4 ... Flexible film 5 ... Polyvinyl alcohol layer 6 ... Hologram master plate

Claims (6)

[Claims] 1. A hologram recording sheet having a photosensitive material layer provided on a flexible film, wherein the flexible film is semi-transparent at a recording wavelength. 2. The hologram recording sheet according to claim 1, wherein the flexible film has a transmittance at a recording wavelength of 70% to 1%. 3. The hologram recording sheet according to claim 2, wherein the flexible film has a transmittance of 50% to 10% at a recording wavelength. 4. The hologram recording sheet according to claim 1, wherein the flexible film is made of a dyed resin containing triacetyl cellulose as a main component. 5. The hologram recording sheet according to claim 1, wherein the flexible film is made of a dyed resin containing polymethacrylate as a main component. 6. The hologram recording sheet according to claim 4, wherein a resin layer containing polyvinyl alcohol as a main component is provided as a barrier layer between the flexible film and the photosensitive material layer.