JP2774509B2 - Method for producing volume phase hologram - Google Patents

Description

The present invention relates to a single volume phase hologram having different Bragg gratings capable of diffracting two different wavelengths of light.

(Prior Art) Conventionally, it has been suggested that volume phase holograms in which an inclined fringe pattern is recorded have importance in applications such as an optical coupling element of a head-up display and a laser eye protection visor for protecting eyes from a laser. .

The hologram as described above requires high diffraction efficiency and transparency, and hologram recording media having such performance include gelatin and poly (N-vinylcarbazole) (hereinafter referred to as PVCz) sensitized with dichromic acid. Abbreviations) are known.

Conventionally, when trying to diffract two different wavelengths with a volume phase hologram, a method is generally used in which two holograms having different Bragg gratings are bonded to each other. I have.

On the other hand, although it is possible in principle to record two Bragg gratings on one hologram, the diffraction efficiency and transparency can be simultaneously realized to a practical level by the developing operation of the volume phase hologram. The technology is unknown.

In particular, when the optical arrangement of the hologram and the display is fixed, such as in a head-up display, it is a technology to change the mutual arrangement and use the incident angle dependence of the diffracted light of the hologram to display other colors. There are many difficulties.

(Problems to be Solved by the Invention) When two holograms are stacked, there are problems such as light scattering at the bonding interface and technical difficulty of multicolor diffraction due to adjustment of the arrangement of the optical system such as bonding. The two-color display also has a problem that it is difficult to form a hologram having two intended Bragg gratings from the above problem.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and particularly to a volume phase hologram that can diffract light of different wavelengths with one hologram without changing the incident angle of the reproduction light. It is to provide.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, in the present invention, the hologram recording layer formed on the substrate is exposed to record an interference fringe pattern, the recording layer is developed and swelled and shrunk by an organic solvent, and then the recording layer is peeled from the substrate. A method for producing a volume phase hologram, wherein the surface in contact with the substrate is developed by swelling and shrinking with an organic solvent under conditions different from the developing conditions.

(Operation) The volume phase hologram is supported and fixed on a transparent substrate according to a normal manufacturing method. An effective hologram is obtained by exposing the light-sensitive material layer supported on the transparent substrate to a laser beam and then performing development by swelling / shrinking operations with a solvent. This is common to the dichromated gelatin system and the PVCz system.

The light-sensitive material layer supported and fixed on the transparent substrate is evenly irradiated with laser light and the interference wave is recorded, but when the solvent swells / shrinks, the solvent penetrates sufficiently into the vicinity of the substrate. Since no hologram is formed in the vicinity of the substrate, that is, only interference waves that do not function as holograms are recorded. Conversely, if the solvent has sufficiently penetrated into the vicinity of the substrate, the light-sensitive material layer tends to peel off from the substrate, and even swelling and shrinking in the direction perpendicular to the surface cannot be performed. Therefore, a layer in which a hologram grating is not formed remains even though a laser interference wave is inevitably recorded near the substrate interface.

The present invention provides a volume phase hologram having different diffraction peaks in the thickness direction of the recording layer by forming a different Bragg grating in addition to the conventional Bragg grating by using the above-described interface near layer.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

In the present invention, up to the first development processing is performed according to a conventionally known method. That is, a hologram recording layer is formed on an appropriate transparent base material such as a glass plate or a plastic film to obtain a hologram recording medium.

The formed recording medium is exposed by an optical system as shown in FIG. 1 using a coherent laser of two light beams of object light and reference light, which are coherent visible light up to 560 nm, in a conventional manner.

Following the exposure step, the recording layer is immersed in a solvent to elute and remove only unreacted halogen compounds (sensitizers) from the recording layer to remove coloring. This step can also serve as a swelling step. Subsequently, a primary swelling and shrinking treatment is performed according to a conventional method to perform a primary development. In this state, the interference fringes recorded near the substrate remain undeveloped as schematically shown in FIG. 2A.

In the present invention, the recording layer of the volume phase hologram obtained as described above is once separated from the transparent substrate. The peeling method is performed by immersing the recording layer in a solvent that does not attack the recording layer. Depending on the type of the transparent substrate, any method may be used as long as it does not damage the recording layer, such as dissolving and removing the transparent substrate. Subsequently, the film of the recording layer is peeled off, and re-fixed to the substrate with the surface in contact with the substrate facing outward (FIG. 2B).

At this time, if necessary, an adhesive such as epoxy, urethane, α-cyanoacrylate, etc., which is transparent and does not damage the recording layer may be used.

The subsequent secondary development process is the same as the primary swelling and shrinking process, but it is necessary to change the swelling and shrinking conditions, particularly the swelling conditions. For example, a solvent having a larger swelling power than the primary swelling, a higher temperature even with the same solvent, or by treating for a long time, a light having a longer wavelength than the diffraction grating obtained by the primary development. A new grating that diffracts the light. Further, when swelling is performed with a weaker force than the primary swelling treatment, a grating that diffracts light having a shorter wavelength than the primary grating can be formed (FIG. 2C).

For example, after exposure with argon at 488 nm, the first development is performed at 20 ° C. in xylene, a peak is set at 490 nm, and the second development is performed at 30 ° C., so that another diffraction piece is obtained at a longer wavelength side of about 50 nm. Can be set. In the above, the shrinkage treatment may be exactly the same, but a shift of about 150 nm is possible by further combining this with the effect of the solvent.

As a hologram photosensitive material that can be used in the present invention, PVCz can be suitably used. In the process of the present invention, the recording layer is required to be handled as a film. Therefore, it is preferable to use PVCz having a molecular weight of 1,000,000 or more, preferably in order to impart strength as a film.

(Effects) According to the present invention as described above, after exposure and development according to a conventional method, the recording layer is separated from the substrate, and the surface of the recording layer in contact with the substrate is subjected to development processing under conditions different from the above conditions. Accordingly, a volume phase hologram in which an interference fringe pattern having two different diffraction peaks in the thickness direction of the recording layer is recorded is provided.

Therefore, the problem of changing the incident angle of the illumination light at the time of exposure and changing the angle of the recording medium required for performing reflection and diffraction of two wavelengths with one hologram is solved. Can be solved, for example, problems such as scattering of light at a bonding interface, thickness, and weight.

(Examples) Next, the present invention will be described more specifically with reference to examples.

Example 1 2.5 g of PVCz having a weight average molecular weight of 1.52 million and a molecular weight distribution of 1.48
And carbon tetraiodine dissolved in chlorobenzene in a dark place and spinner (Kyowa Semiconductor) on a washed glass plate
Was applied and dried to form a 7.2 μm recording layer. The recording layer was exposed to an optical system shown in FIG. 1 using an Ar laser (488 nm) to record a hologram.

After exposure, the film was immersed in toluene at 35 ° C. for 2 minutes and xylene at 35 ° C. for 2 minutes, immersed in heptane at 20 ° C. for 2 minutes, and dried to obtain a volume phase hologram.

By leaving this in water for 30 minutes, the volume hologram film was separated from the substrate. With a polyester film having a surface tension of 40 dyne / cm measured according to JISK-6768, the hologram film was scooped from water and dried so that the surface in contact with the glass substrate was in contact with the polyester film.

Next, this was adhered to a glass plate coated with an epoxy adhesive and dried by adhesion.
It was immersed in xylene at 20 ° C. for 1 minute and then in hexane at 20 ° C. for 1 minute and then dried to obtain a volume phase hologram of the present invention.

When the reflection diffraction efficiency of the hologram was measured,
It showed a diffraction efficiency of 83% at 0 nm and 42% at 490 nm.

Example 2 After exposing to the same recording medium as in Example 1, immersing in toluene at 30 ° C. for 2 minutes and xylene at 30 ° C. for 2 minutes, further immersing in hexane at 18 ° C. for 2 minutes, and then drying, the volume phase type A hologram was obtained. This hologram has a maximum diffraction efficiency of 495nm
The width of the diffraction peak was 23 nm, and the transmittance was 83%.

The film was peeled and re-fixed in the same manner as in Example 1. This was immersed in dioxane at 35 ° C. for 1 minute and in ethyl ether at 15 ° C. for 1 minute and dried to obtain a volume phase hologram of the present invention.

When the reflection diffraction efficiency of the hologram was measured, 49
It had 78% diffraction peaks at 5 nm and 52% at 590 nm.

[Brief description of the drawings]

FIG. 1 shows a hologram recording optical system used in the embodiment,
FIG. 2 is a diagram schematically illustrating the method of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Kuwayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (58) Field surveyed (Int. Cl. ⁶ , DB name) G03H 1/00

Claims (2)

(57) [Claims] 1. A hologram recording layer formed on a substrate is exposed to light to record an interference fringe pattern, and the recording layer is developed and swelled and shrunk with an organic solvent. A method for producing a volume phase hologram, comprising swelling and shrinking a surface which has been in contact with a substrate with an organic solvent under conditions different from the developing conditions and developing the hologram. 2. The method according to claim 1, wherein the recording layer contains poly (N-vinylcarbazole).